WWW.BENTLEY.COM
RAM Concept
Jim Trenerry MIEAust CPEng
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Goals of this presentation Highlight RAM Concept’s capabilities Discuss version 2 enhancements / Version 3 ugges ons or earn ng
e program
Discussion of features that many clients have overlooked Modelling notes
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Capabilities Analysis and design of concrete floors − reinforced − post-tensioned − hybrid mix of RC and PT
Suspended floors − − − − − − −
flat plates beam and one-way slabs two-way beam and slab ribbed slabs / waffle slabs any mix of the above steps: soffit and/or surface
Rafts
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
RAM Concept: Version 2 Span segments − Generation − Width » Manual width » Middle Strip discussion
− Su ort Width − Trimming
Orthotropic Behavior − No-torsion beams − Pour strips
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
RAM Concept: Version 2 Minimum Rebar Punching Shear − Stud shear reinforcement − -
Lateral Self-Equilibrium Loadings
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
RAM Concept: Version 3 3.0 July release − Reinforcement detailing − Wood Armer
3.10 / 4.0 − EC2 Code − Tendon Detailing − Tendon Design − Save Results
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
The RAM Concept design process could be considered to comprise 5 stages Defining the concrete form (**) Defining tendons (if used) (***) Drawing loads (*) ***** Interpreting results (****) The (**) rating is meant to indicate relative degree of difficulty, or relative time you would expect to spend on the stage.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
RAM Concept manual The manual contains a large amount of information. Ideally, you should read it all. We recommend that you at least read the following chapters (and do the tutorials) before beginning your first design.
Ch 1 : Introduction Ch 2 : Looking at the Workspace Ch 3 : Understanding Layers Ch 4 “Using Plans and Perspectives” Ch 5 “Drawing and Editing Objects”
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
RAM Concept manual Ch 16 “Defining the Structure” Ch 22 “Defining Design Strips”.
Ch 35 “General Tips”. Ch 36 “Frequently Asked Questions”. Ch 37 “Errors and Warnings”. Ch 38 : RC Slab Tutorial or Ch 40 : PT Flat Plate Tutorial (AS3600); preferably both Ch 50 : AS3600-2001 Design Ch 53 “Estimating deflections”.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
RAM Concept manual The tutorials introduce you to the “philosophy” of the program and quickly give you experience in using many of the tools. The descriptions are not exhaustive, and you should reference the actual tool description in the appropriate chapter for further information. It is highly recommended that the tutorials are redone for Version 2. The completed tutorial files are available from the program directory, so you don’t have to start from scratch. For example, you could open , , design strips input. Even though design strips are discussed in the tutorials, you should read Chapter 22 Defining Design Strips. Every user must understand how design strips work and this will help in implementing them properly.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
RAM Concept manual RAM Concept does not replace the code. It implements some, but not all, of AS3600. Chapter 50 AS3600-2001 Designdescribes what code rules are used and how the authors interpret and implement the rules. Using the program does not absolve you of knowing your building code.
Specifically, RAM Concept does not consider the following: − Rule 9.1.2 (detailing bars for 25% of the negative moment) − Rule 9.1.3 (general detailing) − Develo ment len ths
Online manual and PDF −
The online manual can be accessed through:
−
The PDF can be accessed through:
Help > Contents Start > RAM Concept > RAM Concept Manual
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Tips for modelling the concrete form Restraint − Columns and walls will restrain the floor against (post-tensioning induced) axial deformations unless » Columns are modelled with rollers see followin slide – It is unlikely that columns above will restrain the floor, and so a roller above will generally be appropriate
» Walls are NOT designated as shear walls
− Restraint forces will generally reduce the P/A and hence increase the service reinforcement. It usually increases strength reinforcement too.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Columns
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Orthotropic properties The orthotropic properties in Concept allow you to model details such as half joints and pour strips. This is done by setting the K factors for axial or bending stiffness.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Half joints A half joint is modelled by setting KMs and KFr (or KMr and KFs) to very low values.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Half joints
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Pour strips: restraint can be modified with slab behaviour properties
Concept has always calculated the restraint effects , calculations have not taken into effect the benefits of the pour strip's time delay. When the pour strip's axial stiffness is low, there is more precompression (P/A) in the slab which is a better solution for service design.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Pour strip with defined slab behaviour property
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Tips for modelling the concrete form
− It is recommended that intersecting walls are drawn such that one wall terminates at the centreline of the other (see following slide) − Walls above behave similarly to beams (see following slide). If in doubt as to their effect, don’t draw them.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Drawing Walls
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Effect of wall modelled above
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Effect of wall modelled above plot of moment about x-axis
Mx=-152kNm/m
© 2006 Bentley Systems, Inc.
Mx=-166kNm/m
WWW.BENTLEY.COM
Tips for modelling the concrete form Compressible property − Column and wall properties include “compressible”. This is useful when there are two or more supports very near each other. − Elastic reaction effects sometimes produce unreasonable reactions for incompressible supports. The following slides show how compressible supports can “share” the load. − The authors generally recommend that compressible supports are used. The only disadvantage is that deflection plots show non-zero values at supports.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Column inside wall … large “elastic reaction” effect
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Fixed end effect large column reaction / tension in wall
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Make more realistic with compressible supports
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Incompressible © 2006 Bentley Systems, Inc.
Compressible
WWW.BENTLEY.COM
Post-tensioning you can specify flat or round duct tendons tendon forces can be: − assumed as constant, or − long-term losses
-
,
» This is done by drawing live-ends. Tendon extensions will then be calculated and can be shown on plan
− Note: initial service calculations (often known as “transfer”) will use a factored tendon force
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Tendon low point location
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Design strips As previously mentioned, design strips (generally) require the most time and consideration of all the program stages. The authors recommend that design strips are drawn to reflect the intent of AS3600: − Flat slabs and plates should have column and middle strips of appropriate widths − Beam design strip widths should be similar to those in rule 8.8.2 » If in doubt, draw a “middle strip” between beam strips
There should usually be one design strip segment per nominal span, and sometimes more. If there is a lot of repetition in the floor, there should be no need to cover it with design strips. Judgement should save you time.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Please read this chapter in manual ! © 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Design strips
Difficult floor … but the client just has to be more logical. The image shows some design strips that are useless - they cause the shear problems because they are so wide and cross so many steps. In the attachment I have chan ed latitude. Longitude needs some work. There are many satisfactory arrangements, and many more bad arrangements that could be drawn. The client need to give this a lot more thought.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Design strips
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Design strips – explanation in chapter
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Default span properties – tab 1
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Don’t reduce integrated M and V due to sign change
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Myy : moment at face of column can change sign which affects integral
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Potential impact of no reduction of M
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Default span properties – tab 2
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Span width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Span width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Span width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Span width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Span width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Span width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Column strip width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Column strip width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Column strip width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Column strip width
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Manual strips : “ovular” building
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Automatic spans (latitude)
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Automatic strips (no good!)
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Manual strips
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Auto spans (longitude)
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Auto strips (longitude)
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Manual strips
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Default span properties – tab 3
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Cross section trimming Many users report unexpected shear bars. This is usually a “shear core” issue. To understand this, consider the shear design of a T-beam section: generally, you would use only the web. The same logic is applied to other cross-sections. ou can v ew a perspec ve o es gn s r p cross sec ons. s s very useful for identifying shear core issues and viewing the section geometry used in the calculation. See section 21.9.4. The “Auditor” reveals what concrete is used in shear calculations (see Chapter 28).
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Design Strips – shear core
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
User defined reinforcement
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
User defined reinforcement
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Miscellaneous tips We have created a template (for the purpose of starting a file) that may or may not suit your needs. You can create your own template with additional plans, materials and settings that you can use when you start a new file. See section 2.4 of the manual. Many tools can be expanded to reveal additional capabilities. See section 2.5. The Utility tool can save you a lot of time when you need to move and stretch many objects or control points. See section 5.9. You can remove trivial results such as small reactions. See section 7.3. The Left Wall and Right Wall tools can be very useful. See section 15.6. You can view the percentage of load that is balanced by the post-tensioning within design strips. See section 26.2.6. Live load reduction is described in Chapter 42. The “Auditor” unlocks the “black-box” of calculations. See Chapter 28.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Miscellaneous tips You can refine the mesh locally.
See section 16.2.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Miscellaneous tips (continued) Read Chapter 27 Plotting Results. Many users are unaware of the power of the plot capabilities. You can plot many results including (strip based) moments (actual and demand), crack widths and reinforcement, to name just a few. You can add plans. See section 26.3.3. Some clients prefer to plot the reinforcement on new plans rather than use the template plans that show bar call-outs.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Miscellaneous tips Deflection Deflection considerations are often critical in a design. Chapter 53 Estimating Deflections describes the methods used. The opening note directs you to the most important sections. It is recommended that you understand which plots consider cracking, and which do not.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Deflection The manual discusses a methodology for determining the long term deflection when Live Load is not permanent (and that is the case for most floors) but it could be updated in view of the LT plot we now have (rather than discuss manual ECR calcs). Deflection Example: Assumptions: creep factor is 3 25% of Live Load is permanent and the other 75% is transient. 100% of live load has been previously applied and so maximum cracking has occurred The long term deflection uses: − effect of maximum cracking − 25% of live load modified with creep effect − 75% of live load with no creep effect
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Deflection 1) The live load creep factor is 1.5. Dead load creep factor is 3.
2) A cracking factor is calculated, similar to section 53.6.2 in manual. 3) However, rather than Calculating weighted ECR, the user can use the LT Deflection Plot from the Max Service Rule Set to observe elastic deflection. This is done by using the plot icon to change the plotted value.
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
In the image LT deflection with 100% of LL is 45 mm. The elastic deflection is 8.3 mm. [The ECR plot is shown for information only.] Since the creep factor FOR THIS RULE SET CALC is 3: the cracking factor is 45 / 8.3 / 3 = 1.8. In other words, the long term deflection multiplier is 45/8.3 = 5.4 (high)
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Create a new LOAD Combination, as shown in the image below, with •load factor for DL and Balance of 5.4 (creep * cracking factor = 3 * 1.8). •load factor for LL of 2.70 (live creep * cracking factor = 1.5 * 1.8).
© 2006 Bentley Systems, Inc.
WWW.BENTLEY.COM
Open the new deflection plan and observe Max deflection is 36 mm rather than 45 (a 20% reduction). Note: slab is 300 thick kPa.
© 2006 Bentley Systems, Inc.
