staad pro and circular slab

STRUCTURE WITH A CIRCULAR SLAB Data:

Top Circular slab Radius : 5.0m Height: 7.0m Two bay Each 3.5m Column size: 0.45m dia Beam size: 0.23m x 0.38m Plate thickness :0.15m Concrete Grade: M20 Steel Grade :Fe415

Fig. 1 Structure with a circular slab Model 1.Geometry Creation :

New Project

 Select  Space Units:

File Name=Circular slab

 Next.

Select

Length =meters; Force=KN;  Add

beam

Finish.

Geometry  Run structure Wizard Select Frame models from Truss model Select

Reverse Cylindrical Frame and double click on it.

Fig. 2 Geometry

parameters

Model name: Reverse Cylindrical Frame Length =7m

Radius =5m

Angle=360

º

No. of Bays along length= 2 No. of Bays along Periphery=16

 Apply Transfer

Remove bottom members 16 Beams are deleted

Model Yes

Ok.

Fig. 3 Geometry of the Structure created with dimension

Fig. 4 Structure with a circular slab-elevation in isometric view Select Top portion of ring beam   New view Select surface meshing surface meshing

 Select

Change

 Plan

view (top view)

all the nodes along periphery one by one using

No. of divisions=3

Ok.

Go to whole structure.

Fig. 5 Define Mesh Region and change Division as 3

Fig. 6 Model after surface meshing of top circular slab 2. Member Property :

Click General

 

Property

Define Circle

YD=0.45m (Column)  Add.

Fig.7 Property for column member Rectangle YD=0.38

ZD=0.23 (Beam)  Add 

Fig. 8 Property for Beam member Thickness node 1,2,3&4=0.15m(slab thickness)  AddClose.

Fig. 9 Property for slab thickness Highlight YD=0.45 & Select

 Beam

Parallel to Y

 Assign

to selected beam

 Assign Yes.

Highlight YD=0.38 ZD=0.23 and select Top ring beam and middle tie beam member Assign to selected beam

 Assign Yes

.

Highlight thickness=0.15m & select plate cursor. Select Top portion of slab



 Assign to selected beam  Assign Yes Close. 3. Supports :

Click Support

 Create  Fixed  Add.

Highlight support 2 and select bottom

most nodes of column by windowing using node cursor nodes  Assign Yes

 Close  De

 Assign

to selected

select the nodes and change to beam cursor.

Fig. 10 Property for support as Fixed 4. Loading :

Click Load case Details Primary

Number

 Add.

:1 Loading type: none Title: Load case 1

Click Load case 1 details Self weight

 Y

 Add

.

 Add.

Factor=-1  Add.

Plate loadsPressure on Full Plates W1=-1KN/m2 Highlight selfweight

Select

selected beam/plates

GY  Add.

geometry cursor & select entire structure  Assign to

 Assign Yes.

5. Analysis Type:

Click Analysis/print Click post print



Define

No

print



Add  Close.

commands Load list

 select

Load comb  AddClick

analysis Results  Add  Close, Note: Save the File before Run the Program. 6. Design :

Click Design

ConcreteCurrent

code : IS456

Define

Parameters

Fc=20,000KN/m2  Add. Click Design commands  Design slab elements

 AddClose.

Highlight Fck=20000 and select plate cursor and select entire structure  Assign

to selected beams/plates

Highlight Design of slab elements one or two portion

 Assign

 Assign Yes.

Top

plan view

 Select

to selected beams/plates

a triangular portion of

 Assign Yes.

Fig. 11 Selection of triangular element for slab assigning 7. Analysis:

From Main Menu

 `

Analysis

 Run

Analysis

 

Done.

8.Results :  Go

to post processing mode.

Select load case 1

Ok.

Click Summary of results of max. and Mini. Displacement

for nodes given in Table form.

Fig. 12 Result- summary Max. and mini. Displacement of nodes Results  Plate stress contour  Select Load case 1 Stress Type: Mx (Local)  Apply Ok.

Fig. 13 Max. and Mini. Bending moment Mx (local) Results  Plate stress contour  Select Load case 1 Stress Type: My (Local)  Apply Ok.

Go to Top view. You can see almost Mx=My (Because of circular

shape of slab). Deflection =9mm.

Fig. 14 Max. and mini. Bending moment My (local)

Fig. 15 Plate orientation of triangular element of slab Mx +ve Top reinforcement along X direction and M-x Bottom reinforecement. At mid span steel is at bottom.

Go to Staad output

Click

Concrete design and see the reinforcement of circular

slab. +Z-top slab reinforcement. Longitudinal reinforcement is at bottom.

Fig. 16 Slab Element Design summary -Min. & Max. reinforcement area for bending moment Mx and My