Technical Report for A structural Design Project

AN-NAJAH NATIONAL UNIVERSITY

Technical Report 2 Three-Dimensional Analysis and Design of the Gateway Building

Bashar Deek Yazan Muqbel Mo’az Alawneh Muhammed Fashafsheh Supervisor: Dr. Samir H. Helou December, 2013

to our parents

ACKNOWLEDGEMENT

We would like to express sincere heartfelt gratitude to our advisor Dr. Samir H. Helou for his valuable guidance and advice. He never ceased helping us learn important topics in the field of Structural Engineering. Dr. Helou has been a great source of encouragement and motivation as he provided us with his undivided attention and continuous support.

ABSTRACT The following project aims at providing a state of the art reinforced concrete structural design undertaking of a commercial building situated in the city of Ramallah; it is called The Gateway Building. The building is comprised of thirteen stories, of which the three basement levels serve as parking spaces, one basement level is reserved for storage purposes and the rest seven stories provide office spaces and stores. The upper most two floors are reserved for restaurants. The three basement levels together have a total area of 4800 square meters; each of the upper floors has an average floor area of about 870 square meters. The loads on each floor will be calculated according to its function. Load values, combinations and factors will be in compliance with the ACI, the IBC or the UBC. Analysis and design of the structure will be carried out using the Extended Three Dimensional Analysis of Building Systems Software, ETABS. The slabs’ design as well as the foundation design will be carried out using SAFE computer software. Various roofing schemes are investigated and explored; the most economic one is recommended. Foundation design is an inseparable part of the present design undertaking. The Gateway Building has already been designed and constructed in Ramallah. However, the present design exercise is conducted with absolutely no reference to any other previous propriety design efforts.

TABLE OF CONTENTS CHAPTER I: INTRODUCTION & NUMERICAL MODELING ........................................9 1. 2. 3.

PURPOSE: ....................................................................................................................................................9 BUILDING INTRODUCTION: ..............................................................................................................................9 STRUCTURAL TOPOLOGY ...............................................................................................................................12 3.1 Design Codes .....................................................................................................................................12 3.2 Materials Used ..................................................................................................................................12 3.3 Gravity Loads: ....................................................................................................................................13 3.3.1. 3.3.2.

Dead Loads .............................................................................................................................................. 13 Snow Loads.............................................................................................................................................. 13

3.4 Load Combinations: ...........................................................................................................................15 3.5 Soil Conditions: ..................................................................................................................................15 4. THE MODEL: ..............................................................................................................................................16 4.1 Model Geometry:...............................................................................................................................16 4.2 The Finite Element Model: .................................................................................................................22 4.2.1. The Frame Element: ................................................................................................................................ 22 4.2.2. Soil Springs .............................................................................................................................................. 24 4.2.3. The Shell Element: ................................................................................................................................... 25 4.2.3.1 The Mat Foundation: .................................................................................................................... 27 4.2.3.2 The Walls: ..................................................................................................................................... 28 4.2.3.3 Ramps: .......................................................................................................................................... 29 4.2.3.4 Stair Cases: .................................................................................................................................... 30 4.2.3.5 Slabs: ............................................................................................................................................. 31 4.2.4. Model Creation Procedure ...................................................................................................................... 32 4.2.5. Model Load Assignment .......................................................................................................................... 33

CHAPTER II: LINEAR STATIC ANALYSIS & DESIGN ................................................... 34 1.

PRELIMINARY ANALYSIS RESULTS....................................................................................................................34 1.1 Punching shear ..................................................................................................................................34 1.2 Deflection: .........................................................................................................................................38 2. STRUCTURAL DESIGN FOR STATIC LOADS..........................................................................................................39 2.1 Concrete Frame Design ......................................................................................................................39 2.1.1.

2.2 2.3

2.3.1. 2.3.2.

2.4

Column Design: ....................................................................................................................................... 39

Wall Design:.......................................................................................................................................51 Slab Design: .......................................................................................................................................63 th

4 Basement Slab Design ........................................................................................................................ 64 First-Roof Slab Design.............................................................................................................................. 68

Mat Foundation Design: ....................................................................................................................70

CHAPTER III: EARTHQUAKE ANALYSIS & DESIGN .................................................... 75 1. 2.

BACKGROUND ............................................................................................................................................75 GEOLOGY ..................................................................................................................................................75

3. 4. 5. 6. 7. 8.

MODAL ANALYSIS .......................................................................................................................................76 EQUIVALENT LATERAL LOAD METHOD .............................................................................................................77 RESPONSE SPECTRUM ANALYSIS.....................................................................................................................80 LOAD COMBINATIONS ..................................................................................................................................81 RESULTS ....................................................................................................................................................81 STRUCTURAL DESIGN FOR DYNAMIC LOADS......................................................................................................82 8.1 Mat Foundation Design .....................................................................................................................82 8.2 Slabs Design .......................................................................................................................................84 8.2.1.

Fourth Basement Slab Design.................................................................................................................. 84

CHAPTER IV: STRUCTURAL DESIGN SUMMARY & CONCLUSION.......................... 86 1. 2.

STRUCTURAL DESIGN SUMMARY ....................................................................................................................86 CONCLUSION ..............................................................................................................................................86

LIST OF TABLES

Table 1: Codes Used for Analysis and Design ......................................................................................12 Table 2: Materials Used-Concrete...........................................................................................................12 Table 3: Materials Used- Grade 60 Rebar Steel ....................................................................................12 Table 4: Lateral Earth Pressure ...............................................................................................................13 Table 5: ASCE Minimum Design Loads ...............................................................................................14 Table 6: Load Combinations ...................................................................................................................15 Table 7: Cartesian Grid Data ...................................................................................................................17 Table 8: Cylindrical Grid Data ................................................................................................................18 Table 9: Cylindrical System Origin .........................................................................................................18 Table 10: Frame element sections used in the model ..........................................................................23 Table 11: Story Data .................................................................................................................................31 Table 12: Punching shear ratios for all 50 columns in the 4th basement...........................................35 Table 13: Punching shear ratios for all 25 columns in the 1st roof ...................................................37 Table 15: Maximum Deflection Values at Selected Floors .................................................................38 Table 14: ACI TABLE 9.5 (b) of maximum permissible roof deflections .......................................38 Table 16: "Interior Columns_Large" Auto-Select List ........................................................................39 Table 17: "Interior Columns_Small" Auto-Select List ........................................................................40 Table 18: "Exterior Columns' Auto-Select List ....................................................................................40 Table 19: Columns Section Design ........................................................................................................46 Table 20: Column forces in the 4th basement .......................................................................................46 Table 21: ETABS flexural design data of C23 column section ..........................................................47 Table 22: ETABS shear design data of C23 column section ..............................................................48 Table 23: ETABS report for uniform basement wall reinforcement ................................................54 Table 24: ETABS report for uniform interior wall reinforcement ....................................................58 Table 25: CSA3 forces and reinforcement reported by SAFE in B4 slab ........................................65 Table 26: Forces and Reinforcement as reported by SAFE for max. design strip in 1st Roof .....69 Table 27: Soil Pressure .............................................................................................................................71 Table 28: SAFE vs. hand-calculated values for mat reinforcement ..................................................73 Table 29: Modal analysis output .............................................................................................................77 Table 30: Modal mass participating ratios .............................................................................................77 Table 31: Parameters of Equivalent Lateral Load Method .................................................................78 Table 32: Table 16-N from UBC-97 Code............................................................................................78 Table 33l: Load combinations for earthquake loads ............................................................................81 Table 34: Soil pressure summary due to combined lateral and gravity loads ...................................82 Table 35: Soil pressure summary for a 60cm-thick foundation .........................................................82 Table 36: Max. forces in the mat foundation due to dynamic load ...................................................83 Table 37: Punching shear data for 4th basement slab .........................................................................84 Table 38: Punching shear data for 4th basement slab with drop panels ...........................................85

LIST OF FIGURES

Figure 1: The Gateway Building ............................................................................................................... 9 Figure 2: Above-grade floors plan ..........................................................................................................10 Figure 3: Basement floor plan .................................................................................................................10 Figure 4: Elevation view of the building................................................................................................11 Figure 5: Model units and design codes.................................................................................................16 Figure 6: Grid Systems .............................................................................................................................16 Figure 7: Cartesian and Cylindrical Grid Systems ................................................................................19 Figure 8: Floors Labels .............................................................................................................................20 Figure 9: Story Data ..................................................................................................................................21 Figure 10: Local coordinate system of the frame element ..................................................................22 Figure 11: Local coordinates of a column section ...............................................................................23 Figure 12: Area spring property data......................................................................................................24 Figure 13: Soil Modulus assignment to shells .......................................................................................24 Figure 14: Quadrilateral shell element ....................................................................................................25 Figure 15: Shell element uniform coordinate systems .........................................................................26 Figure 16: 3D view of the mat foundation ............................................................................................27 Figure 17: Mat foundation section properties.......................................................................................27 Figure 18: 3D screen capture of the walls .............................................................................................28 Figure 19: 3D capture of the ramps .......................................................................................................29 Figure 20: Ramp-wall connection ...........................................................................................................29 Figure 21: 3D screen capture of stair slabs ...........................................................................................30 Figure 22: Slab mesh .................................................................................................................................31 Figure 23: 3D Extruded view of slabs ...................................................................................................31 Figure 24: The "model check" option ....................................................................................................32 Figure 25: Base Reactions due to a test load .........................................................................................33 Figure 26: Uniform shell load assignment .............................................................................................33 Figure 27: Snapshot of SAFE punching shear parameters for a 700X700mm interior column ...36 Figure 28: Local axes of columns ...........................................................................................................40 Figure 29: Column Labels ........................................................................................................................41 Figure 30: Column rebar selection rules in ETABS .............................................................................49 Figure 31: C23 rebar details in 3D view.................................................................................................49 Figure 32: Design section "E" for C23 column....................................................................................50 Figure 33: Design section "C" for C23 column ....................................................................................50 Figure 34: C23 design schedule from base to staircase .......................................................................50 Figure 35: Plan view of external basement walls ..................................................................................51 Figure 36: Extruded 3D view of external basement wall ....................................................................52 Figure 37: V23 values for the external basement wall .........................................................................53 Figure 38: M22 values for interior wall section ....................................................................................55 Figure 39:V23 values for interior wall section ......................................................................................56 Figure 40: Rebar selection prefrences for walls ....................................................................................59 Figure 41: 3D view of confined wall reinforcement at corners .........................................................60 Figure 42: Reinforced section in internal shear wall ............................................................................61

Figure 43: Elevation section of internal wall reinforcement ...............................................................62 Figure 44: Screen capture of design strips menu in SAFE v12 ..........................................................63 Figure 45: X-axis design strips for 4th basement slabs .........................................................................64 Figure 46: CSA_3 moment diagram .......................................................................................................64 Figure 47: Moment Diagrams for all A-strips in 4th basement slab .................................................66 Figure 48: Moment Diagrams for all B-strips in 4th basement slab ..................................................67 Figure 49: Design-strip moment diagram with max. values ...............................................................68 Figure 50: Moment diagrams in both A&B strips for 1st-roof slab ..................................................68 Figure 51: Moment diagram of A-strips in mat foundation ...............................................................72 Figure 52: Moment diagrams of B strips in mat foundation ..............................................................73 Figure 53: Mat foundation detailing preferences ..................................................................................74 Figure 54: Seismic zone factor map .......................................................................................................75 Figure 55: Mass source Definition..........................................................................................................76 Figure 56: Story shears in X-direction due to ELLMX .......................................................................79 Figure 57: Story shears in Y-direction due to ELLMY .......................................................................79 Figure 58: Response spectrum curve .....................................................................................................80 Figure 59: CSA3 moment diagram for Comb8 ....................................................................................84

CHAPTER I: Introduction & Numerical Modeling

1. Purpose: The purpose of this Graduation Project Exercise is to analyze and design the structural system for a multi-functional building in Ramallah; dubbed the Gateway Building. The 3-D analysis and design undertakings are carried out in compliance with the ASCE, ACI and UBC codes of practice. This is accomplished by the widely used computer software ETABS and SAFE.

2. Building Introduction: The Gateway Building is a multi-functional building located in the city of Ramallah, Al-Irsal Street. It is comprised of thirteen stories of which four basement levels serve as parking spaces and the rest eight floors provide office spaces, stores and restaurants. The total area of the building is about 14,000 square meters. All stories have a height of 3 meters each. According to floor area and geometry, there are two groups of identical floors; the four basement floors and the upper floors.

Figure 1: The Gateway Building

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Figure 3: Basement floor plan

Figure 2: Above-grade floors plan

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Figure 4: Elevation view of the building

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3. Structural Topology

3.1 Design Codes Code ASCE /SEI 7-10 ACI Code 318-11

Use Minimum design loads, minimum section requirements and load combinations. Frames and shear wall section design and rebar.

ACI Code 318-08

Slab and mat foundation design using SAFE v12

UBC 97

Earthquake analysis Table 1: Codes Used for Analysis and Design

3.2 Materials Used Usage Foundation Columns Shear Walls Slabs

Strength f’c (MPa) 35 35 28 28

Concrete Unit Weight (kN/m3) 23.54 23.54 23.54 23.54

Modulus of Elasticity (MPa) 27806 27806 24870 24870

Table 2: Materials Used-Concrete

Usage

Min. Yield Strength (MPa)

Foundation Columns Shear Walls Slabs

413 413 413 413

Rebar Steel Min. Tensile Unit Weight Strength (kN/m3) (MPa) 621 77 621 77 621 77 621 77

Modulus of Elasticity (MPa) 200E+3 200E+3 200E+3 200E+3

Table 3: Materials Used- Grade 60 Rebar Steel

Solving for displacements and forces will be in the linear and elastic part of the stress-strain diagram for each material. All materials are isotropic.

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3.3 Gravity Loads: 3.3.1.

Dead Loads

The Dead loads are due to structural elements self weight. This load is computed internally by the software and included in the analysis. The self-weight multiplier is 1, so ETABS calculates the weight of an element by multiplying the materials density by the volume of element. Lateral earth pressure; this type of load acts on structural elements below the ground level; these are the external walls of the 4 basements. Backfill soil is classified as silty gravels or poorly graded gravel-sand mixes with a design lateral load value of 5.50 kN/m2 per one meter of depth. Table (3.2-1, ASCE). Since ETABS software does not have a linear function for loads varying with depth, it is decided that maximum earth pressure is calculated at the bottom of each basement story and imported to ETABS as uniformly distributed loads over areas. Basement Floor 4th basement 3rd basement 2nd basement 1st basement

Depth below grade (m)

Lateral earth pressure (kN/m2)

12 9 6 3

66 49.5 33 16.5

Table 4: Lateral Earth Pressure

3.3.2.

Snow Loads

Considering a snow density of 300 kg/m3 and a Maximum snow height of 70 cm; the snow load per square meter is 210 kg/m2 which corresponds to 2 kN/m2.

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Floor

Function

Live Load (kN/m2)

Dead Load (kN/m2)

Superimposed Dead Load (kN/m2)

Snow Load (kN/m2

4th basement 3rd basement 2nd basement 1st basement Ground Floor Mezzanine Floor 1st floor 2nd floor 3rd floor 4th floor 5th floor st 1 roof floor 2nd roof floor Staircase floor

Parking Parking Parking Parking Store spaces Store spaces Office spaces Office spaces Office spaces Office spaces Office spaces Restaurants Restaurants Staircase

2.5 2.5 2.5 2.5 3.6 3.6 2.4 2.4 2.4 2.4 2.4 4.8 4.8 1

Self weight Self weight Self weight Self weight Self weight Self weight Self weight Self weight Self weight Self weight Self weight Self weight Self weight Self weight

0 0 0 0 2 2 2 2 2 2 2 2 0 0

0 0 0 0 0 0 0 0 0 0 0 0 2 2

Table 5: ASCE Minimum Design Loads

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3.4 Load Combinations: For the analysis and design of the Gateway Building, gravity static loads are considered; the ASCE 7-5 in Chapter 2 recommends the use of the following load combinations for the strength design method: Comb1: U= 1.4D Comb2: U=1.2D + 1.6L Comb3: U=1.2D + 1.6L + 0.5S Comb4: U=1.2D+1.6L+ 0.5S+1.6H Comb5: U=Envelope (Comb1, Comb2, Comb3, Comb4) Table 6: Load Combinations

3.5 Soil Conditions: The Structure is built on rock that has a bearing capacity of 250 kN/m2. During analysis and design the soil is treated as a linear and elastic material which means the modulus of sub-grade soil is constant.

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4. The Model: Numerical Modeling is the basis for modern structural analysis and design. The model has to simulate the expected behavior of all elements within the structure.

4.1 Model Geometry: Model geometry is created in partial conformity with the architectural plans of the building. A more challenging structural system necessitated the elimination of some columns that are deemed superfluous; this resulted in longer span lengths at some locations. Model geometry creation steps: Metric SI standard units are used. All geometric dimensions are in meter units. Design code preferences are also selected

Figure 5: Model units and design codes

The geometry of the building required defining both Cartesian and cylindrical gridlines. Cartesian grid system is named G1 and cylindrical system is called Cylindrical inside ETABS. Secondary gridlines were separately added in order to account for interior structural details like shear walls and ramps. Gridlines are very important since they provide the milestones for model creation and facilitate the process of connecting finite elements precisely in the model.

Figure 6: Grid Systems

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G1- Cartesian Grid Data X Grid data

Y Grid Data

Grid ID

X Ordinate (cm)

Grid ID

Y Ordinate (cm)

A

0

1

574.2

B

1442.6

2

1204.2

C

1912.6

3

2584.2

D

2758.8

4

3326

E

3301.2

5

3461.4

F

3886.7

-

-

G

4526.2

-

-

H

5100.4

-

-

I

5411.4

-

-

Secondary Grid Lines Grid ID A1 A2 A3 A4 A5 A6 6

X1 (cm)

Y1 (cm)

X2 (cm)

Y2 (cm)

0

0

933.2

3461.4

933.2

3461.4

5411.4

3326

5411.4

3326

5100.4

574.2

686.7

0

1614.7

3442.1

2908.8

2584.2

2908.8

2974.2

2908.8

2974.2

3886.7

2974.2

0

0

4526.2

0

Table 7: Cartesian Grid Data

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Cylindrical Grid Data Radial Grid Data Grid ID

R Ordinate (cm)

A’

0

B’

574.2

Tangential Grid data Grid ID

T Ordinate (cm)

10 9 8 7 6 5 4 3 2 1

0 10 20 30 40 50 60 70 80 90 Table 8: Cylindrical Grid Data

Cylindrical System Origin Global X (cm)

4526.2

Global Y (cm)

574.2

Rotation (deg)

-90 Table 9: Cylindrical System Origin

Note that cylindrical system’s origin is located at the intersection of Cartesian gridlines 1&G.

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Figure 7: Cartesian and Cylindrical Grid Systems

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Stories are defined in ETABS from bottom to top, keeping in mind that ETABS labels floors according to their ceiling, i.e. B4 slab is the top of the 4th basement floor and the ground slab for the 3rd basement floor and so on. Height of each story is assigned as well.

Figure 8: Floors Labels

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Floor Name

Height (mm)

Elevation (mm)

Stair Case Roof2 Roof1 F5 F4 F3 F2 F1 MEZZANINE GF B1 B2 B3 B4 Base

3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 0

42000 39000 36000 33000 30000 27000 24000 21000 18000 15000 12000 9000 6000 3000 0

Figure 9: Story Data

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4.2 The Finite Element Model: All structural elements in the model are either frame or shells elements. The task is to select the element type that would simulate the real behavior of the structure. The threedimensional model consists of a large number of finite-elements connected together at the nodes. The following are the element types used in the numerical model:

4.2.1.

The Frame Element:

The frame element is modeled as a straight line connecting two points. This element activates six degrees of freedom at both of its joints (three translational and three rotational) and include the effects of biaxial bending, torsion, axial deformation and biaxial shear deformations. A frame element has its own local coordinate system. The axes of this local system are denoted by 1, 2 and 3. The “1” axis is directed along the length of the element, the “2 & 3” axes lie in the plane perpendicular to the element. Understanding the local coordinate system is essential since it is the basis of load assignment and reading analysis results.

Figure 10: Local coordinate system of the frame element

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ETABS reports internal forces in frame elements as follows: P, the axial force. V2, the shear force in the 1-2 plane. V3, the shear force in the 1-3 plane. T, the axial torque. M2, the bending moment in the 1-3 plane (about the 2-axis). M3, the bending moment in the 1-2 plane (about the 3 axis)

All frame elements used in the model are prismatic and have square sections. All column supports at the bottom of the lower basement level are pinned.

Section C70x70 C40X40

Frame element sections used in the model Depth (mm) Width (mm) 700 700 400 400

Material Concrete_35MPa Concrete_35MPa

Table 10: Frame element sections used in the model

The figure below shows local axes of a typical column in ETABS, where the width is along the 3-axis and the depth is along the 2-axis.

Figure 11: Local coordinates of a column section

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4.2.2.

Soil Springs

The soil supporting the structure is assumed to be linear and elastic with constant subgrade modulus of (40 * safety factor * soil allowable pressure). Soil springs are assigned as area springs with stiffness equal to sub-grade modulus in the Z-direction and zero stiffness in the other two directions.

Figure 12: Area spring property data

Soil property (Modulus of Sub-grade Reaction is 25,000 kN/m3) is assigned to all shell elements that compose the mat foundation.

Figure 13: Soil Modulus assignment to shells

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4.2.3.

The Shell Element:

The shell element is a three- or four-node element that combines both membrane and plate-bending behavior. The major advantage of using the shell element in this model is that it does not have to be planar, thus it can be used to model inclined ramps and stairs. Shell elements in the model are uniformlyloaded in gravity and normal-to-plane directions. Both quadrilateral and triangular elements are used in the model, but the majority of shell elements are of a quadrilateral shape. Triangular elements are used in corners and irregular locations where the quadrilateral element could not be used. The shell element has its own local coordinate system. The axes of this local system are denoted 1, 2 and 3. The “1 & 2” axes lie in the plane of the element and the “3-axis” is normal to the plane. The shell element always activates all six degrees of freedom at each of its connected joints (Ux, Uy, Uz, Rx, Ry and Rz).

Figure 14: Quadrilateral shell element

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All shell elements used in the model are “thin-shells” which means that shear deformations are neglected. Local axes of area elements are meant to be uniform (all pointing towards one direction); this facilitates retrieving analysis results and assigning loads.

Figure 15: Shell element uniform coordinate systems

ETABS reports internal forces in shell element as the following: F11: Direct force per unit length acting at the mid-surface of the element on the positive and negative 1 faces in the 1-axis direction. F22: Direct force per unit length acting at the mid-surface of the element on the positive and negative 2 faces in the 2-axis direction. F12: Shearing force per unit length acting at the mid-surface of the element on the positive and negative 1 faces in the 2-axis direction, and acting on the positive and negative 2 faces in the 1-axis direction. V13: Out-of-plane shear per unit length acting at the mid-surface of the element on the positive and negative 1 faces in the 3-axis direction. V23: Out-of-plane shear per unit length acting at the mid-surface of the element on the positive and negative 2 faces in the 3-axis direction. M11: Direct moment per unit length acting at the mid-surface of the element on the positive and negative 1 faces about the 2-axis. M22: Direct moment per unit length acting at the mid-surface of the element on the positive and negative 2 faces about the 1-axis. M12: Twisting moment per unit length acting at the mid-surface of the element on the positive and negative 1 faces about the 1-axis, and acting on the positive and negative 2 faces about the 2-axis.

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Shell elements are used in the model for the following structural systems:

4.2.3.1

The Mat Foundation:

A mat foundation of 25 cm thickness is spread under the entire building; underneath columns there is additional thickness (drop panels) extruding 35 cm below the mat foundation. Concrete of 35 MPa compressive strength is used for the foundations.

Figure 16: 3D view of the mat foundation

Figure 17: Mat foundation section properties

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4.2.3.2

The Walls:

Walls of 30 cm thickness are constructed in the outer perimeter of the building where they act as retaining walls. Interior walls are of 20cm thickness acting as shear walls and elevator cores. All walls are defined as shell elements. All wall supports at the bottom of the lower basement level were idealized as pinned connections. Windows and doors are assigned as wall openings.

Figure 18: 3D screen capture of the walls

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4.2.3.3Ramps: Ramps are used in basement parking levels, so the model includes four ramps. They are modeled as shell elements with a thickness of 25cm. Ramps’ meshing is made with added accuracy so that the nodes on the ramp are adequately connected with the shear walls surrounding it. The modeling choice is made since there will be ample steel anchorage between the ramps and the walls; concrete is cast simultaneously for ramps and the adjacent parts of the walls.

Figure 19: 3D capture of the ramps

Figure 20: Ramp-wall connection

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4.2.3.4

Stair Cases:

The stair slabs are modeled as shell elements having a thickness of 20 cm. The stairs’ slabs are connected with the floor slabs in the model with no connection to the shear walls.

Figure 21: 3D screen capture of stair slabs

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4.2.3.5

Slabs:

Slabs of 25 cm thickness are defined as shell elements; they are used in the model for all floor levels.

Figure 22: Slab mesh

Table 11: Story Data

Figure 23: 3D Extruded view of slabs

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4.2.4.

Model Creation Procedure

The finite elements comprising the structure are interconnected with high accuracy and precision starting from base to top floor level. The 13-floors could be all replicated at once, but this is not a convenient act since errors in the model are almost inevitable, therefore once a certain storey is ready it is preferred to carry out a “Model Check” which will check area overlaps and other types of errors in the model. When a “Model Check” indicates errors, it is the designer’s job to locate the errors and fix them before trying to perform a “Model Run”, taking into consideration that a “no-error-message” that the check process shows does not necessarily indicate that the model will be “error-free” after performing the “Model Run”. In conclusion, carrying out a “Model Run” upon the completion of each individual story is the proper way to smoothen the process of locating errors. The “Model Run” is performed using the standard solver at the level of modeling since it reports errors in the model and locates them.

Figure 24: The "model check" option

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Most types of errors that are encountered are the “lost digits of accuracy”, mostly of 6 or 7 digits. The other type of error is the “Instability Error” which indicates the whole structure or some elements are instable; this is normally due to lack of boundary conditions. After making sure that model is free of any type of error, an equilibrium check is carried out. A test point load of 100 kN is applied at some point in the model in the three directions (X, Y and Z) and base reactions are subsequently checked. Results confirm the state of static equilibrium since base reactions in all directions must equal the applied point loads.

Figure 25: Base Reactions due to a test load

4.2.5.

Model Load Assignment

After making sure that the model is free of any type of errors, the loads are assigned according to the minimum design loads reported in Tables 4 & 5. All loads in the model are uniform loads distributed on area elements. For the assignment of load cases (superimposed, live and snow loads) on the slabs, all the slabs having the same load values are selected and have the load assigned to them in the gravity direction.

Figure 26: Uniform shell load assignment

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CHAPTER II: LINEAR STATIC ANALYSIS & DESIGN 1. Preliminary Analysis Results 1.1 Punching shear A thickness of 25cm for the slabs is deemed adequate for resisting punching shear, yet the method used for the check is simple and does not account for moment effects on the punching shear stress and assumes a one-way behavior of slabs; a method that is not very accurate for buildings. SAFE V12 software is used for calculating punching shear ratios. Floors from ETABS model are exported to SAFE V12 while considering load on the exported floor plus all loads that come from upper stories. Punching shear ratio is the quotient of the maximum design shear stress over the concrete shear stress capacity. Ratios with a value of less than one mean that slab thickness is adequate for resisting punching shear; otherwise, slab thickness must be increased. The punching shear ratio check is performed for the mat foundation, 4th basement and 1st roof. This selection of floors is based on change in live load values and load from upper stories. 4th basement has the largest vertical load on columns; mat foundation has the largest vertical load combined with soil stress while the 1st roof has the highest live load value of all floors. The following table is the SAFE output for punching shear ratios based on ACI-318-08 code considering zero reinforcement for the 4th basement. COMB4 is used for the calculation. Maximum shear ratio (highlighted in red) is less than one. The “Not Calculated” message is generated because SAFE does not compute shear stress for columns that intersect with beams and/or shear walls. A 250 mm-thickness slab is deemed adequate for resisting punching shear for basement floors.

Point 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100

Global X (m) 14.426 19.126 19.126 19.126 19.126 27.588 27.588 27.588 27.588 38.867 38.867 38.867 45.262 45.262

Global Y (m) 12.042 25.842 18.892 12.042 5.742 25.842 18.892 12.042 5.742 12.042 5.742 18.892 25.842 18.892

Status Not Calculated OK OK OK OK OK OK OK OK OK OK OK OK OK

Ratio (Unitless)

Vu (kN)

0.75442 0.524153 0.461789 0.733241 0.836288 0.834174 0.888361 0.793316 0.991457 0.891976 0.922998 0.881885 0.610887

589.752 473.234 399.601 651.462 732.716 766.548 762.012 753.616 666.383 674.168 650.342 743.552 559.122

34

2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2332 2345 10410 10428 10431 10449 10476 10479 2087

45.262 45.262 8.41506 6.867 14.426 19.126 27.588 33.012 38.867 45.262 51.004 51.71601 52.49017 53.27564 54.114 45.262 38.867 33.012 27.588 19.126 14.426 9.332 3.24655 1.54805 0 6.96705 5.09332 10.11355 14.426 14.426 33.012 38.867 38.867 33.012 29.088 29.088 14.426

12.042 5.742 5.742 0 0 0 0 0 0 0 5.742 12.042 18.892 25.842 33.26 33.52765 33.721 33.89803 34.06202 34.31787 34.45998 34.614 12.042 5.742 0 25.842 18.892 12.042 18.892 25.842 25.842 25.842 29.742 29.742 29.742 25.842 12.042

OK OK OK Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated

0.513137 0.466837 0.764348

480.402 444.783 702.741

Table 12: Punching shear ratios for all 50 columns in the 4th basement

SAFE V2 uses the following equation for calculating punching shear stress (CSI Technical Report 1 “How SAFE Calculates Punching Shear Ratios, November 16th, 1998”). The following snapshot illustrates how SAFE applies the punching shear equation. VU =

35

Figure 27: Snapshot of SAFE punching shear parameters for a 700X700mm interior column

36

The same procedure is performed for the 1st roof floor where the live load is 4.8 kN/m2 (The largest of all floors). Point 2187 2189 2191 2193 2195 2197 2198 2199 2201 2203 2205 2207 2208 2210 2212 2214 2216 2226 2249 2250 2251 2252 2322 2335 14793 14830

GlobalX (m) 14.426 19.126 19.126 19.126 19.126 27.588 27.588 27.588 27.588 38.867 38.867 38.867 45.262 45.262 45.262 45.262 8.41506 10.11355 38.867 38.867 29.088 29.088 14.426 14.426 33.012 33.012

GlobalY (m) 12.042 25.842 18.892 12.042 5.742 25.842 18.892 12.042 5.742 12.042 5.742 18.892 25.842 18.892 12.042 5.742 5.742 12.042 25.842 29.742 29.742 25.842 18.892 25.842 25.842 29.742

Status Not Calculated OK OK OK Not Calculated OK Failed Failed Not Calculated OK Not Calculated Failed Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated Not Calculated

Ratio (Unitless)

Vu (kN)

0.933907 0.990372 0.953191

705.807 825.109 783.597

0.954601 1.401612 1.495514

715.622 1246.713 1280.51

0.964988

1177.222

1.441559

1158.114

Table 13: Punching shear ratios for all 25 columns in the 1st roof

Results show that a 250-mm-thick slab is inadequate for resisting punching shear at the interior columns therefore 150-mm-thick drop panels are used at interior columns. After applying the same procedure; Ground and Mezzanine floors need 150-mm-thick drop panels for the interior columns. Accordingly, a drop panel of 40 cm thickness is defined and assigned into the model at all interior columns.

37

1.2 Deflection: Deflection of structural elements in the building is a major concern. Actual deflections in the building need to be checked against permissible deflection limits in the ACI 318-08 code in order to judge slab thickness adequacy.

Table 14: ACI TABLE 9.5 (b) of maximum permissible roof deflections

The critical criterion for checking deflection is L/480 since the building has nonstructural elements likely to be damaged by large deflections. Floors are exported separately to SAFE V12 for deflection check.

Floor

Case

Max. deflection, Uz (mm)

Roof 1 GF B4 F1

Comb4 Comb4 Comb4 Comb4

22.99 21.59 22.54 18.57

Location X 33.012 33.012 33.012 33.012

Y 15.042 15.042 15.042 15.042

Critical Span length (mm) 11300 11300 11300 11330

Allowable Deflection (mm) 23.5 23.5 23.5 23.5

Status OK OK OK OK

Table 15: Maximum Deflection Values at Selected Floors

Maximum deflection values do not exceed maximum permissible values, therefore the slab thickness is judged adequate.

38

2. Structural Design for Static Loads After analysis of the ETABS model has been completed and the preliminary results are quite satisfying, the design process will be carried out in order to select optimum section dimensions and reinforcement ratios for all structural elements in the building.

2.1 Concrete Frame Design This includes the design of both columns and beams in the building. Design is performed in compliance with the ACI-318-11 Code.

2.1.1.

Column Design:

Column sections used in the modeling stage are checked again in the design stage in order to assure their adequacy of resisting applied forces and to select the optimum section dimensions. ETABS is used for this type of design where all columns in the model are assigned to an “auto-select list” where the software is given multiple sections defined by the user; the software’s job is to select the optimum section. A first check trial was carried out; it indicated that 70X70cm column section is not adequate at some locations. Three auto-select lists are created; one for the interior columns that have relatively large axial loads, one for the interior columns that have relatively small axial loads and one for the exterior columns.

Large Interior Columns Section Label

Width mm

Depth mm

Radius of Gyration about weak axis(mm)

C80X80

800

800

230.9

C80X60

800

600

173.2

C60X60

600

600

173.2

C40X40

400

400

115.5

Table 16: "Interior Columns_Large" Auto-Select List

39

Small Interior Columns Section Label

Width

Depth


C60X60

600

600

173.2

C60X40

600

400

115.5

C40X40

400

400

115.5

Table 17: "Interior Columns_Small" Auto-Select List

Large Exterior Columns Section Label

Width

Depth


C40X40

600

600

115.5

C30X30

600

400

86.6

Table 18: "Exterior Columns' Auto-Select List

Figure 27 below shows local axes of columns in ETABS, where width is along 3-axis and depth is along 2-axis.

Figure 28: Local axes of columns

The drawing next page shows all columns in the 4th basement level with all column labels. ETABS provided optimum sections for each column label according to the “auto-select” list each column is assigned to. Large interior columns and small interior columns are divided into 5 groups based on story levels; there are five groups (basements, GF to F2, F3 to F5, 2Roofs and the staircase). Exterior columns are not assigned to any group, thus sections for these columns are going to be the same along all story levels.

40

Figure 29: Column Labels

41

Column Label

C22

C23

C24

C25

C42

Auto-select list

Interior Columns_Large





Group

Design Section

Basements

C80X80

GF to F2

C80X80

F3 to F5

C80X80

2 Floors

C80X80

Staircase

C60X60

Basements

C80X80

GF to F2

C80X80

F3 to F5

C80X80

2 Floors

C80X80

Staircase

C60X60

Basements

C80X80

GF to F2

C80X80

F3 to F5

C80X80

2 Floors

C80X80

Basements

C80X80

GF to F2

C80X80

F3 to F5

C80X80

2 Floors

C80X80

Basements

C80X80

GF to F2

C80X80

F3 to F5

C80X80

2 Floors

C80X80

Staircase

C60X60

42

Column Label

C20

C12

C16

C3

C11

C18

Auto-select list

Group

Design Section

Basements

C80X80

GF to F2

C80X80

F3 to F5

C80X80

2 Floors

C80X80

Staircase

C60X60

Basements

C80X80

GF to F2

C80X80

F3 to F5

C80X80

2 Floors

C80X80

Basements

C80X80

GF to F2

C80X80

F3 to F5

C80X80

2 Floors

C80X80

Basements

C60X60

Interior_Columns

GF to F2

C60X60

Small

F3 to F5

C60XC40

2 Floors

C60X60

Basements

C60X60

Interior_Columns

GF to F2

C60X60

Small

F3 to F5

C60XC40

2 Floors

C60X60

Basements

C60X60

GF to F2

C60X60

F3 to F5

C60XC40




Interior_Columns Small

43

Interior_Columns C18

C19

C7

C8

C9

C10

C13

2 Floors

C60X60

Basements

C60X60

Interior_Columns

GF to F2

C60X60

Small

F3 to F5

C60XC40

2 Floors

C60X60

Basements

C60X60

Interior_Columns

GF to F2

C60X60

Small

F3 to F5

C60X40

2 Floors

C60X40

Basements

C60X60

Interior_Columns

GF to F2

C60X60

Small

F3 to F5

C60X60

2 Roofs

C60XC40

Basements

C60X60

Interior_Columns

GF to F2

C60X60

Small

F3 to F5

C60X60

2 Roofs

C60XC40

Basements

C60XC40

Interior_Columns

GF to F2

C60XC40

Small

F3 to F5

C60XC40

2 Roofs

C60XC40

Basements

C60XC40

Interior_Columns

GF to F2

C60XC40

Small

F3 to F5

C60XC40

2 Roofs

C60XC40

Small

44

Column Label

Auto-select list

Group

Design Section

C34

External Columns

All

C30X30

C35

External Columns

All

C30X30

C36

External Columns

All

C30X30

C37

External Columns

All

C30X30

C38

External Columns

All

C30X30

C39

External Columns

All

C30X30

C40

External Columns

All

C30X30

C41

External Columns

All

C30X30

C30

External Columns

All

C30X30

C31

External Columns

All

C30X30

C32

External Columns

All

C30X30

C33

External Columns

All

C30X30

C29

External Columns

All

C30X30

C28

External Columns

All

C30X30

C27

External Columns

All

C30X30

C26

External Columns

All

C30X30

C21

External Columns

All

C30X30

C15

External Columns

All

C30X30

C14

External Columns

All

C30X30

C46

External Columns

All

C30X30

C45

External Columns

All

C30X30

C44

External Columns

All

C30X30

C2

External Columns

All

C30X30

C1

External Columns

All

C30X30

45

C17

External Columns

All

C40X40

C6

External Columns

All

C40X40

C5

External Columns

All

C40X40

C4

External Columns

All

C40X40

C47

External Columns

All

C30X30

C43

External Columns

All

C30X30

C49

External Columns

All

C30X30

C48

External Columns

All

C30X30

Table 19: Columns Section Design

Selection of “Auto-select” lists and column groups take two points into consideration: optimization (selecting the minimum section that resists applied loads) and convenience during construction by keeping the number of column sections as minimum and as uniform as possible. The table below shows an example of forces in design sections in the 4th basement level. Column Label

Comb

Station m

P kN

V2 kN

V3 kN

T kN.m

M2 kN.m

M3 kN.m

C22

Comb5

C23

Comb5

C13

Comb5

C48

Comb5

0 3 0 3 0 3 0 3

-4405 -4342 -9175 -9112 -2690 -2666 -395 -228

-402 -402 -228 -228 -20 -20 2 -4.6

-142 -142 98 98 -13. -13 -11 25.8

1.69 1.69 1.33 1.33 -0.4 -0.4 0.76 -0.69

-408 31 202 -54 -9.15 46.77 -13 -12.9

-1094 112 -548 189 -28 40 10.6 5.7

Table 20: Column forces in the 4th basement

According the equation Φ Pn (max) = 0.80ø [0.85f’c (Ag – Ast) + fyAst], where Φ=0.65, f’c=35 MPa and Ast assumed as 3%, a section of 550x550mm would we adequate for resisting the axial force on C23 column, but the design section is larger due to high biaxial moment effects acting on the section. C23 column is taken as an example of ETABS column design and illustrated in detail in the following tables. Reinforcement detailing is provided as well.

46

ETABS 2013 Concrete Frame Design ACI 318-11 Column Section Design

Column Element Details (Flexural Details) Level

Element

Section ID

Combo ID

Station Loc

Length (mm)

LLRF

Type

B4

C23

C80x80

Comb5ic(Envelope Static)

0

3000

0.4

Sway Special

Section Properties b (mm)

h (mm)

dc (mm)

Cover (Torsion) (mm)

800

800

50

17.3

Material Properties Ec (MPa)

f'c (MPa)

Lt.Wt Factor (Unitless)

fy (MPa)

fys (MPa)

27806

35

1

413

413

Design Code Parameters ΦT

ΦCTied

ΦCSpiral

ΦVns

ΦVs

ΦVjoint

0.9

0.65

0.75

0.75

0.6

0.85

Axial Force and Biaxial Moment Design For Pu , Mu2 , Mu3 Design Pu kN

Design Mu2 kN-m

Design Mu3 kN-m

Minimum M2 kN-m

Minimum M3 kN-m

Rebar Area mm²

Rebar % %

11746.2555

460.9231

-709.4527

460.9231

460.9231

10129

1.58

Factored & Minimum Biaxial Moments NonSway Mns kN-m

Sway Ms kN-m

Factored Mu kN-m

Minimum Mmin kN-m

Minimum Eccentricity mm

Major Bending(Mu3)

-709.4527

0

-709.4527

460.9231

39.2

Minor Bending(Mu2)

155.0855

0

155.0855

460.9231

39.2

Axial Force and Biaxial Moment Factors Cm Factor Unitless

δns Factor Unitless

δs Factor Unitless

K Factor Unitless

Length mm

Major Bend(M3)

0.522102

1

1

1

3000

Minor Bend(M2)

0.4

1

1

1

3000

Table 21: ETABS flexural design data of C23 column section

47

ETABS 2013 Concrete Frame Design ACI 318-11 Column Section Design

Column Element Details (Shear Details) Level

Element

Section ID

Combo ID

Station Loc

Length (mm)

LLRF

Type

B4

C23

C80x80

Comb5ic(Envelope Static)

0

3000

0.4

Sway Special

Section Properties b (mm)

h (mm)

dc (mm)

Cover (Torsion) (mm)

800

800

50

17.3

Material Properties Ec (MPa)

f'c (MPa)

Lt.Wt Factor (Unitless)

fy (MPa)

fys (MPa)

27806

35

1

413

413

Shear Design for Vu2, Vu3 Rebar Av /s mm²/m

Design Vu kN

Design Pu kN

Design Mu kN-m

ΦVc kN

ΦVs kN

ΦVn kN

Major Shear(V2)

0

299.8167

11746.2555

-548.6075

1030.5642

0

1030.5642

Minor Shear(V3)

0

98.1831

11746.2555

202.573

1030.5642

0

1030.5642

Design Forces Factored Vu kN

Factored Pu kN

Factored Mu kN-m

Major Shear(V2)

299.8167

9175.5855

-709.4527

Minor Shear(V3)

98.1831

9175.5855

155.0855

Design Basis Shr Reduc Factor Unitless

Strength fys MPa

Strength fcs MPa

Area Ag cm²

1

413

35

6400

Concrete Shear Capacity Design Vu kN

Conc.Area Acu cm²

Tensn.Rein Ast mm²

Major Shear(V2)

299.8167

6000

5064

Minor Shear(V3)

98.1831

6000

5064

Shear Rebar Design Stress v MPa

Conc.Cpcty vc MPa

Uppr.Limit vmax MPa

Φvc MPa

Φvmax MPa

RebarArea Av /s mm²/m

Major Shear(V2)

0.5

2.29

6.22

Minor Shear(V3)

0.16

2.29

6.22

1.72

0

0

1.72

4.67

0

Table 22: ETABS shear design data of C23 column section

48

Rebar selection rules are provided to the software for detailing.

Figure 30: Column rebar selection rules in ETABS

Figure 31: C23 rebar details in 3D view

49

Figure 34: C23 design schedule from base to staircase

Figure 32: Design section "E" for C23 column Figure 33: Design section "C" for C23 column

50

2.2 Wall Design: Two groups of walls are used in the model; exterior walls of 30 cm thickness and interior walls of 20 cm thickness. The first group of walls mainly resists the lateral earth pressure induced by the backfill soil; therefore M22 and V23 are the governing forces for design. The second group acts mainly as bearing walls.

Figure 35: Plan view of external basement walls

Maximum values of flexural moment M22 and shear V23 are found in the wall section shown in Figure34. M22 and V23 values are plotted in the following diagrams. The maximum moment value occurs at the bottom and corresponds to 115 kN-m/m. The maximum V23 value also occurs at the bottom and corresponds to 128 kN/m. This external wall is supported by the basement slabs.

51

Figure 36: Extruded 3D view of external basement wall

The 3D Figure 35shows the external basement wall having pin supports at the bottom and supported by slabs of B4, B3, B2 and B1.

52

Figure 36: M22 values for the external basement wall

Figure 37: V23 values for the external basement wall

According the equation

, substituting the maximum

moment value of 115 kN.m/m, section strip width of 1000 mm and 300 mm as the effective depth of section, the reinforcement ratio is 0.35%, which is almost the same reinforcement ratio of 0.31 % that the software has provided.

53

Story

Pier Label

Station

Design Type

Edge Rebar

End Rebar 14

Rebar Spacing mm 250

Min. Reinf. % 0.25

Current Reinf. % 0.31

B1

P30

Top

Uniform

12

B1

P30

Bottom

Uniform

12

14

250

0.25

0.31

B2

P30

Top

Uniform

12

14

250

0.25

0.31

B2

P30

Bottom

Uniform

12

14

250

0.25

0.31

B3

P30

Top

Uniform

12

14

250

0.25

0.31

B3

P30

Bottom

Uniform

12

14

250

0.25

0.31

B4

P30

Top

Uniform

12

14

250

0.25

0.31

B4

P30

Bottom

Uniform

12

14

250

0.25

0.31

Pier Leg mm

Leg X1 mm

Leg Y1 mm

Leg X2 mm 48133

Leg Y2 mm 769

Shear Rebar mm2/m 750

Top Leg 1 Bottom Leg 1 Top Leg 1 Bottom Leg 1 Top Leg 1 Bottom Leg 1 Top Leg 1 Bottom Leg 1

47225

346

47225

346

48133

769

750

47225

346

48133

769

750

47225

346

48133

769

750

47225

346

48133

769

750

47225

346

48133

769

750

47225

346

48133

769

750

47225

346

48133

769

750

Table 23: ETABS report for uniform basement wall reinforcement

54

For the interior walls, flexure and shear values as well as reinforcement data are reported. The following figures show M22 and V23 values in an interior wall section where the maximum values of forces are found.

Figure 38: M22 values for interior wall section

Maximum value of M22 is reported at the bottom of the wall section and corresponds to 54 kN-m/m. A hand calculated reinforcement ratio for this flexural force is 0.37 %. ETABS has provided a reinforcement ratio of 0.49 to 0.67, which is larger than the hand-calculated reinforcement values.

55

Figure 39:V23 values for interior wall section

Maximum value of V23 is reported at the bottom of the wall section and corresponds to 70 kN/m. The table next page provides reinforcement data for all interior walls with 20cm section thickness in the whole building.

56

Pier Label

Station

Design Type

Edge Rebar

End Rebar

Rebar Spacing mm

Min. Reinf %

Current Reinf %

Stair Case

P20

Top

Uniform

12

14

250

0.25

0.67

Stair Case

P20

Bottom

Uniform

12

14

250

0.25

0.48

Roof2

P20

Top

Uniform

12

14

250

0.25

0.67

Roof2

P20

Bottom

Uniform

12

14

250

0.25

0.49

Roof1

P20

Top

Uniform

12

14

250

0.25

0.67

Roof1

P20

Bottom

Uniform

12

14

250

0.25

0.49

F5

P20

Top

Uniform

12

14

250

0.25

0.67

F5

P20

Bottom

Uniform

12

14

250

0.25

0.49

F4

P20

Top

Uniform

12

14

250

0.25

0.67

F4

P20

Bottom

Uniform

12

14

250

0.25

0.49

F3

P20

Top

Uniform

12

14

250

0.25

0.67

F3

P20

Bottom

Uniform

12

14

250

0.25

0.49

Story

Pier Leg mm Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1

Leg X1 mm 360 12

Leg Y1 mm 2779 2

Leg X2 mm 3601 2

Leg Y2 mm 2974 2

Shear Rebar mm2/m

388 67

2681 7

3886 7

2974 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

101 13.6

1204 2

1442 6

1204 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

500

57

F2

P20

Top

Uniform

12

14

250

0.25

0.67

F2

P20

Bottom

Uniform

12

14

250

0.25

0.49

F1

P20

Top

Uniform

12

14

250

0.25

0.67

F1

P20

Bottom

Uniform

12

14

250

0.25

0.49

MEZZAN -INE

P20

Top

Uniform

12

14

250

0.25

0.67

MEZZAN -INE

P20

Bottom

Uniform

12

14

250

0.25

0.49

GF

P20

Top

Uniform

12

14

250

0.25

0.67

GF

P20

Bottom

Uniform

12

14

250

0.25

0.49

B1

P20

Top

Uniform

12

14

250

0.25

0.66

B1

P20

Bottom

Uniform

12

14

250

0.25

0.48

Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1 Top Leg 1 Botto m Leg 1

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

124 49.7

1354 2

1244 9.7

1554 2

500

Table 24: ETABS report for uniform interior wall reinforcement

58

In ETABS, all walls need to be labeled as piers so that the software would be able to provide reinforcement detailing values and graphics. Personal preferences for rebar selection are also provided to ETABS.

Figure 40: Rebar selection prefrences for walls

The software calculates all forces in wall sections and provides the required steel ratio and the minimum reinforcement according to ACI-318-11 Code. The uniform reinforcement option is selected; therefore reinforcement values are uniform in all wall sections having the same pier label. 30cm walls are labeled as Pier30 and 20cm walls are labeled as Pier20.

59

Figure 41: 3D view of confined wall reinforcement at corners

60

`

Figure 42: Reinforced section in internal shear wall

61

`

Figure 43: Elevation section of internal wall reinforcement

62

2.3 Slab Design: Each roof is exported to SAFE V12 for design. SAFE designs slabs for flexure and punching shear in accordance with ACI-318-08. There are two methods for design; a finiteelement-based method and a strip-based one. For this project, the strip-based design is used since it allows for rebar calculations, while the finite-element-based approach checks rebar area provided by designer against actual stresses in the slab. Moreover, design strips can be used for rebar detailing. Procedure of slab design is SAFE V12 is outlined below: Drawing design strips along the X and Y axes. Design strips are called Strip A and Strip B respectively. Strips for each axis are divided into two types; column strips that are drawn along column centerlines and middle strips drawn between each two rows of columns (in mid-spans). All strips have a width of 1 meter.

Figure 44: Screen capture of design strips menu in SAFE v12

Note that SAFE draws strips from centerlines, which means that a 1 meter strip is assigned as 0.5 meters from right and 0.5 meters from left. Design strips may cross slab openings and/or extrude slab outer lines, but this does not affect analysis or design results. Load combinations are checked (already exported from ETABS model) and the Strength (ultimate) Design Method is selected. “Run and Design” is carried out; the designer inspects strip forces and compares them with forces based on a finite element analysis. The values of shear and moment are almost identical everywhere in the slab. Only slabs for the 4th basement, ground floor and 1st roof are designed. This selection of slabs is based upon variation in live load values.

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2.3.1.

4th Basement Slab Design

Flexure and shear values are reported by SAFE. SAFE also provides reinforcement steel in accordance with ACI-318-08 Code. This slab is solid with no drop panels and has a thickness of 25cm. For design strips, MSA stand for middle strip-A and CSA stands for column strip-A.

Figure 45: X-axis design strips for 4th basement slabs

Figure 46: CSA_3 moment diagram

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Conc Width m

FTopMoment kN.m

FTopArea 2 mm

FTopAMin 2 mm

FBotMoment kN.m

FBotArea 2 mm

FBotAMin 2 mm

V Force kN

VArea 2 mm /m

Status

Global X m

Global Y m

0.5177 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

-34.4186 -0.1726 0 -127.3975 -60.5339 -10.9128 0 0 -3.09 -36.8601 -357.0576 -82.3367 -14.5507 -0.02 0 0 0 0 0 0 -7.3336 -66.5377 -265.5921 -105.2553 -32.4039 -0.4702 0

491.497 374.834 146.421 1669.485 765.834 134.806 0 0 38.034 461.063 5161.406 1053.254 180.049 0 0 0 0 0 0 0 90.442 844.326 3801.853 1362.75 404.358 5.781 0

240.933 465.396 0 465.396 465.396 465.396 0 0 465.396 465.396 465.396 465.396 465.396 0 0 0 0 0 0 0 465.396 465.396 465.396 465.396 465.396 0 0

2.6667 14.0022 35.7218 0.0193 0 1.1423 9.9952 9.9846 1.2232 0.0422 0 0 2.8689 34.8068 57.5723 69.0246 71.0779 69.4167 58.7434 37.6057 4.0817 0 0 0 0.0217 10.8523 28.1028

135.259 277.36 485.884 0 0 14.048 123.418 123.286 15.043 0 946.911 0 35.309 434.843 727.293 876.982 904.01 882.139 742.518 470.443 50.263 0 0 0 0 134.055 349.968

0 0 465.396 0 0 0 465.396 465.396 0 0 0 0 0 465.396 465.396 465.396 465.396 465.396 465.396 465.396 0 0 0 0 0 465.396 465.396

45.157 86.941 30.496 157.117 157.117 52.217 15.758 11.761 28.424 28.424 340.187 340.187 67.778 41.713 26.256 13.978 4.913 12.769 24.532 38.952 56.092 231.155 231.155 163.827 72.5 36.255 20.927

0 0 0 861.845 861.845 0 0 0 0 0 2820.612 2820.612 0 0 0 0 0 0 0 0 0 1212.478 1212.478 861.845 0 0 0

OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK

51.71601 51.004 50.262 45.262 44.867 43.867 42.867 41.867 40.867 39.867 38.867 38.012 37.012 36.012 35.012 34.012 33.012 32.588 31.588 30.588 29.588 28.588 27.588 27.126 26.126 25.126 24.126

12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042

Table 25: CSA3 forces and reinforcement reported by SAFE in B4 slab

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Figure 47: Moment Diagrams for all A-strips in 4th basement slab

66

Figure 48: Moment Diagrams for all B-strips in 4th basement slab

67

2.3.2.

First-Roof Slab Design

The roof slab has a relatively high live load of 4.8 kN/m2; therefore design is expected to be different. This slab is solid with a thickness of 25cm and having drop panels of 40cm thickness (15cm extrusion below slab surface) as stated earlier in the preliminary design.

Figure 50: Moment diagrams in both A&B strips for 1st-roof slab

Maximum negative and maximum positive moments are 689 kN.m and 96.7 kN.m are reported respectively in the CSA2 strip in the slab.

Figure 49: Design-strip moment diagram with max. values

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ConcWidth m

FTopMoment kN.m

FTopArea mm2

FTopAMin mm2

FBotMoment kN.m

FBotArea mm2

FBotAMin mm2

VForce kN

VArea mm2/m

Status

GlobalX m

GlobalY m

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

-265.0206 -692.2001 -174.8691 -43.3142 -0.0868 0 0 0 0 0 -0.0931 -46.6357 -187.5513 -736.1775 -85.5196

2107.761 5925.636 2388.936 577.721 125.632 111.039 107.217 98.449 97.796 97.202 110.065 625.263 2582.8 6401.231 1095.772

744.634 744.634 465.396 465.396 0 0 0 0 0 0 0 465.396 465.396 744.634 465.396

0 0 0 0 35.1028 74.6225 93.4558 96.4577 93.3042 74.1228 34.046 0 0 0 0

229.749 201.323 220.075 130.779 473.076 979.651 1229.757 1268.027 1224.313 969.458 455.534 147.345 366.405 374.324 0

0 0 0 0 465.396 465.396 465.396 465.396 465.396 465.396 465.396 0 0 0 0

158.399 510.627 510.627 136.563 77.354 43.957 22.479 8.943 23.05 44.788 78.841 146.988 605.309 605.309 74.946

861.845 2329.948 2329.948 0 0 0 0 0 0 0 0 0 3169.326 3169.326 0

OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK

27.126 27.588 28.588 29.588 30.588 31.588 32.588 33.012 34.012 35.012 36.012 37.012 38.012 38.867 39.867

12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042 12.042

Table 26: Forces and Reinforcement as reported by SAFE for max. design strip in 1st Roof

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2.4 Mat Foundation Design: This is the structural system used in this project for supporting the building. The use of this type of foundation reduces the potential of differential settlement. The relation between stresses in the mat slab and the downward vertical settlement is defined as the soil sub-grade modulus (K). An initial check of the model under this service load combination (D+L) resulted in a base reaction of 162,500 kN. With soil capacity of 250kN/m2 the required foundation area is 650m2 which is way less than the area of the foundation provided in the model. Modulus of sub-grade used is K=25000 kN/m3. Before starting the first run, all points are selected and released in the vertical Z direction, and then soil sub-grade property is applied as area springs. An initial check of punching shear results for the mat foundation shows that drop panels of 70cm below columns are not adequate for resisting punching shear stress at some locations where shearing stress reached twice that of the section’s capacity. Depth of drop panel had to be increased to 120cm in order to resist punching shear stress. The major concerns when designing foundations are; foundation uplifts and soil allowable pressure. There should be no behavior of uplift in the mat foundation (tension in soil) and the allowable soil pressure must not be exceeded at any part in the foundation. The following table reports SAFEv12 values of soil pressure. Area F1 F1 F1 F1 F2 F2 F2 F2 F3 F3 F3 F3 F4 F4 F4 F4 F5 F5 F5 F5 F6

Surface Pressure (kN/m2) -112.98 -137.1 -156.3 -156.29 -0.57 -20.15 -18.83 -0.91 -118.7 -118.92 -99 -98.7 -98.7 -99 -62.53 -60.07 -60.07 -62.53 -32.98 -26.27 -26.27

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F6 F6 F6 Area F9 F9 F9 F9 F10 F10 F10 F10 F11 F11 F11 F11 F12 F12 F12 F12 F13 F13 F13 F13 F14 F14 F14 F14 F15 F15 F15 F15 F22 F22 F22 F22 F23 F23 F23 F23 F24 F24 F24 F24 F26

-32.98 -21.96 -9.09 Surface Pressure (kN/m2) -20.15 -81.08 -72.42 -18.83 -81.08 -173.56 -162.77 -72.42 -173.56 -238.77 -233.9 -162.77 -238.77 -244.54 -237.08 -233.9 -188.48 -178.84 -233.9 -237.08 -178.84 -125.78 -162.77 -233.9 -9.09 -21.96 -21.34 -3.36 -125.78 -64.06 -72.42 -162.77 -64.06 -27.07 -18.83 -72.42 -27.07 -13.7 -0.91 -18.83 -137.1

Table 27: Soil Pressure

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All pressure values have a negative sign which means that soil is subjected to compressive forces only and no uplift in the foundation. Maximum and minimum absolute pressure value highlighted in red is 244.54 kN/m2; it is less than the allowable soil pressure; 250 kN/m2. The 25 cm mat thickness selected in the ETABS model is not adequate for resisting flexure because the required reinforcement exceeded the maximum allowed. Thickness was increased to 30 cm and resulted in an acceptable reinforcement ratio.

Figure 51: Moment diagram of A-strips in mat foundation

Maximum positive moment = 4318.3 kN-m occurs in column-strip A at section with thickness of 120 cm. Maximum negative moment = 283.6 kN.m occurs in column-strip B at section with thickness of 30 cm.

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Figure 52: Moment diagrams of B strips in mat foundation

Moment kN.m 4318.3 -283.6

Section Depth mm 1200 300

Section Width 1000 1000

Reinforcement Ratio 0.0088 0.0093

As,hand (mm2)

As,SAFE (mm2)

10,610 2,797

10877 3344

Table 28: SAFE vs. hand-calculated values for mat reinforcement

The table above is a verification of steel reinforcement provided by SAFEv12 for maximum negative and positive moments in the mat foundation. Now SAFE has provided steel reinforcement areas for all strips in the mat foundation. For detailing, the designer has to provide his own preferences for rebar diameters and spacing.

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Figure 53: Mat foundation detailing preferences

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CHAPTER III: EARTHQUAKE ANALYSIS & DESIGN 1. Background Earthquakes can cause disastrous damage to structures if the forces they induce are sufficiently greater than the capacity of structural elements in the structure. The potential seismic forces that may hit the Gateway Building should be studied. Behavior of the gravityloaded structure will be investigated against lateral dynamic forces. Two methods are used for calculating seismic forces; the equivalent static lateral load method and the response spectrum method. For gravity loads, the elevator cores and internal walls in the model act as bearing walls, while walls in the outer perimeter act as bearing walls and resist shear and moment due to lateral earth pressure from soil backfill in the basement levels. Analysis complies with 1997 UBC Code.

2. Geology The Gateway building is located in al-Irsal Street, Ramallah. This zone is classified as 2A with both the acceleration seismic and the velocity seismic coefficients (Ca and Cv) equal to 0.15 because soil is classified as rock,SB. This is considered a moderate-risk zone according to UBC97.

Figure 54: Seismic zone factor map

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3. Modal Analysis This is a linear analysis that is used to determine the vibration modes of the structure. These modes are useful to understand the dynamic behavior of the structure and form the basis of the Response Spectrum Analysis. The Eigenvector analysis is used to find the modes of The Gateway Building. The number of modes this analysis can provide is equal to the mass degrees of freedom found in the model, but usually for such buildings the first modes are sufficient. Eigenvector analysis reports values as Eigenvalues. An Eigenvalue is the square of the circular frequency ( 





Where K is the stiffness and M is the mass participating in the dynamic analysis, therefore the mass source must be well-defined in order to provide correct dynamic behavior for the structure. The mass participating in the dynamic behavior of the structure comprises of self-mass of the structure plus superimposed dead load and a portion of live load; 0.3.

Figure 55: Mass source Definition

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Mode

Period (Seconds)

Frequency (cycle/second)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

1.102 0.931 0.511 0.268 0.227 0.143 0.128 0.121 0.097 0.088 0.083 0.074 0.069 0.065 0.063 0.059 0.058 0.058 0.054 0.053

0.907 1.074 1.956 3.736 4.408 6.974 7.793 8.296 10.301 11.346 12.116 13.576 14.469 15.368 15.997 16.899 17.216 17.374 18.58 18.872

Circular Frequency (rad/sec) 5.7019 6.748 12.2874 23.4749 27.6991 43.82 48.9648 52.1273 64.7201 71.2888 76.125 85.2979 90.9094 96.5631 100.5101 106.1809 108.1725 109.1661 116.7427 118.5737

Eigenvalue (rad2/sec2) 32.5119 45.5361 150.9794 551.0726 767.2421 1920.1896 2397.5558 2717.2537 4188.687 5082.0939 5795.0088 7275.7348 8264.5268 9324.4252 10102.2897 11274.3828 11701.2977 11917.2423 13628.8596 14059.7315

Table 29: Modal analysis output

The UBC-97 code states in section 1631.5.2 that at least 90 percent of the participating mass of the structure is included in the calculations for each principal horizontal direction. This code requirement necessitated 20 modes to be inspected since 12 modes were not enough to satisfy the code requirement. Direction UX UY

Static 99.98 99.98

Dynamic 93.54 93.49

Table 30: Modal mass participating ratios

4. Equivalent Lateral Load Method The Equivalent Lateral Load Method is based on simplified procedure that substitutes potential dynamic forces for their equivalent static ones based on code provisions and factors. For analysis, equivalent static base shear is program-calculated based on the input values according to the UBC-97 Code. This method gives a good indication of story shears.

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Parameter T (seconds) R Soil profile type Z Ca Cv I

Value 1.1 4.5 SB 0.15 0.15 0.15 1.0

Table 31: Parameters of Equivalent Lateral Load Method

T, structure period in seconds, is determined according to ETABS output for the first mode of the structure. The software provided a value of 1.1 seconds. Method A in Section 1630.2.2 in the UBC-97 Code provides an equation to approximate T.

T= Ct (hn)3/4

Where, Ct= 0.03, a numerical coefficient. hn= 137.8 ft, height of the building in feet.

This equation yielded a structure period of 1.2 seconds. This values is not significantly different from the values provided by ETABS. R, the over-strength factor that considers global ductility capacity of lateral-forceresisting systems. This factor makes the design forces less than the forces induced by the earthquake. The Gateway Building’s lateral-force-resisting structural system is classified as concrete shear-walls. Table 16-N in the UBC-97 Code provides R values for common structural systems.

Table 32: Table 16-N from UBC-97 Code

SB, soil profile type as in Table 16-J in the UBC-97 Code. Soil on site is classified as rock.

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Z, seismic zone factor. The UBC-97 Code provides values for Z for all regions in the world. For this analysis practice, the value of Z is taken from Earth Sciences and Seismic Engineering Center at An-Najah University. Ca, seismic coefficient from Table 16-Q in the UBC Code. Cv, seismic coefficient from Table 16-R in the UBC Code. I, Importance factor that depends on occupancy category as in Table 16-K. Equivalent lateral load is defined as a load pattern in ETABS in both X and Y directions. This resulted in a 4142 kN base shear in the both X and Y-directions. Load patterns are denoted by ELLMX and ELLMY.

Figure 56: Story shears in X-direction due to ELLMX

Figure 57: Story shears in Y-direction due to ELLMY

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5. Response Spectrum Analysis Elastic dynamic analysis of a structure utilizes the peak dynamic response of all effective modes. The response spectrum curve is a plot of period and acceleration based on statistical data for each location. For Ca and Cv values of 0.15 and a damping ratio of 5%, the UBC-97 Code provides a response spectrum curve.

Response Spectrum Curve 0.45 0.4 0.35

Acceleration

0.3 0.25 0.2 0.15 0.1 0.05 0 0.00

2.00

4.00

6.00

8.00

10.00

12.00

Period Figure 58: Response spectrum curve

Proper modal combinations are assigned into ETABS in order to utilize the response all effective modes. Defining a modal combination is essential since peak modal responses occur at different times. The CQC (complete quadratic combination) method is used for modal combination.

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6. Load Combinations Load combinations of static gravity forces are added to dynamic forces. Comb5: U=Envelope (Comb1, Comb2, Comb3, Comb4) Comb6: U=1.2D + 1.0L + 1.0S + 1.0H + 1.0E Comb7: U=1.2D + 1.0L + 1.0S + 1.0H - 1.0E Comb8: U=Envelope(Comb5, Comb6, Comb7) Table 33l: Load combinations for earthquake loads

7. Results All story drifts are below maximum allowable drifts in the UBC-97 Code. Design philosophy is based on the idea of assuring life safety during earthquakes, therefore, some structural elements may undergo plastic deformations due to seismic forces but this will not cause threat to the life of the building’s occupants.

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8. Structural Design for Dynamic Loads The main concern is the lateral forces induced to the structure by the earthquakes. Structural elements’ that are designed to resist gravity static forces are expected to fail under dynamic loading. Capacity of elements designed in the linear static stage of the project will be re-evaluated after applying dynamic loads, and necessary changes to their design will be carried out if needed. Design under dynamic loads is compared to design under static loads.

8.1 Mat Foundation Design The mat foundation is subjected to the summation of all story shears in the building. Soil is assumed to be the same as in the static analysis; linear with modulus of 25,000 kN/m 3. The pressure in any point in the mat foundation must not exceed 250 kN/m2, that is the maximum allowable soil pressure. Tension or uplift forces on the soil are not allowed as well. For resisting gravity static forces, a mat foundation thickness of 30cm thickness with 120cm drop panels under columns was dubbed adequate. This design is re-evaluated under dynamic lateral load. The first design trial deemed a 30cm thickness adequate for resisting flexure and shear forces and provided reinforcement ratios that satisfy minimum requirement and are below maximum allowed limit, but soil pressure exceeded maximum allowable limit and there were tensile forces acting on the soil as shown in next table. MaxPress kN/m2

MinPress kN/m2

GlobalXMax m

GlobalYMax m

GlobalXMin m

GlobalYMin m

8.98

-389.72

33.012

16.042

27.588

13.042

Table 34: Soil pressure summary due to combined lateral and gravity loads

Excessive pressure on soil can be treated by increasing the mat foundation stiffness. This is achieved by increasing the thickness. Both uplift and excessive pressure on soil were treated by increasing mat thickness to 60cm. MaxPress kN/m2

MinPress kN/m2

GlobalXMax m

GlobalYMax m

GlobalXMin m

GlobalYMin m

-22

-241

8.410

35.658

14.426

17.042

Table 35: Soil pressure summary for a 60cm-thick foundation

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Max. negative moment (kN.m) Max. positive moment (kN.m) Max. shear (kN)

Design Strip

Section thickness mm

4613.6221

1200

513.2

600

3275.746

1200

Table 36: Max. forces in the mat foundation due to dynamic load

The table above reports maximum moment and shear force in the mat foundation slab. The difference between these forces and the forces reported due to static gravity loads are not significantly different.

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8.2 Slabs Design Slab thickness and reinforcement ratios adequacy is judged based on dynamic loading.

8.2.1.

Fourth Basement Slab Design

The design completed for gravity loads will be checked against dynamic lateral loads. Design strips are defined as stated earlier. SAFE V12 has shown that the thickness of 25cm is adequate and is able to resist the lateral load.

Figure 59: CSA3 moment diagram for Comb8

Moment values due to Comb8 are not significantly different from those due to Comb5, therefore slab thickness is adequate. Some variations in reinforcement values have been found. As per punching shear design, it was determined that the use of drop panels for basement floors slabs is unnecessary. Under dynamic loading, 40cm drop panels had to be used because punching shear ratios exceeded 1 at many locations. Point 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099

Global X 19.126 19.126 19.126 19.126 27.588 27.588 27.588 27.588 38.867 38.867 38.867 45.262

Global Y 25.842 18.892 12.042 5.742 25.842 18.892 12.042 5.742 12.042 5.742 18.892 25.842

Status OK OK OK Failed OK OK OK OK Failed Failed Failed Failed

Ratio 0.825018 0.657269 0.634517 1.176682 0.926061 0.779566 0.792111 0.927096 1.150031 1.402556 1.024411 1.119385

VU 556.497 244.066 217.287 650.936 496.443 720.752 716.204 738.724 629.302 662.195 613.127 715.722

Table 37: Punching shear data for 4th basement slab

All punching shear calculations are based on the slab’s effective depth of 217mm.

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After adding drop panels, all punching shear ratios were below 1. Point 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099

Global X 19.126 19.126 19.126 19.126 27.588 27.588 27.588 27.588 38.867 38.867 38.867 45.262

Global Y 25.842 18.892 12.042 5.742 25.842 18.892 12.042 5.742 12.042 5.742 18.892 25.842

Status OK OK OK OK OK OK OK OK OK OK OK OK

Ratio 0.51545 0.387563 0.392851 0.642104 0.662842 0.464407 0.472063 0.533066 0.684385 0.742246 0.63552 0.721301

VU 588.531 414.934 388.707 682.224 633.553 727.141 707.536 788.709 596.694 686.242 609.602 846.306

Table 38: Punching shear data for 4th basement slab with drop panels

Reinforcement details for the 4th basement slab are shown in the appendix.

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CHAPTER IV: Structural Design Summary & Conclusion 1. Structural Design Summary Analysis via a numerical model and the application of reinforced-concrete design principles that comply with the ACI-318-11 Code have resulted in a section of 60-cm depth with 120-cm drop panels below columns for punching-shear resistance. As for columns, the largest section is square-shaped with 80-cm side length, and the smallest section is also a square with 30-cm length. Exterior walls that resist the seismic lateral forces as well as gravity forces have a 30-cm thick section with reinforcement ratios 3 times greater than the minimum ratio advised by the code. Interior walls have a section of 20-cm. For slabs, all floors have slabs with 25-cm thickness with drop panels protruding 15-cm below slab (total thickness of 40-cm) for resisting punching shear forces.

2. Conclusion This project group has come up with many conclusions regarding analysis and reinforced concrete design. Conclusions are summed as follows: Flat-plate slab systems are very efficient and can be used for relatively long spans in commercial buildings. This practice is proven by eliminating numerous columns that were considered superfluous. Column-drop panels are good for both increasing punching shear capacity of the section and for negative moment resistance. They have also been found to reduce deflection along the span. For numerical modeling, the shell-element is best used for modeling shear walls and slabs for they take into consideration both in-plane and out-of-plane bending behavior in addition to axial forces. The soil supporting the structure did undergo excessive pressures and tensile forces at some locations due to the lateral forces induced by the earthquake, therefore, the mat thickness had to be doubled. This practice may not be economical but is justified.

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APPENDIX Reinforcement Detailing

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Technical Report for A structural Design Project

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