ir.unimas.my on finite element analysis and... · seminar on . finite element analysis and design...

Seminar on

Finite Element Analysis and Design of RC Buildings

25-26th May 2005

Multi Media Theater, UNIMAS Main Campus

Kota Samarahan, Sarawak, Malaysia

Organized By

Asian Center for Engineering Computations and Software , School of Civil Engineering, Asian Institute of Technology (AIT)

Bangkok, Thailand

JOintly organized by

Department of Civil Engineering, Faculty of Engineering

University Malaysia Sarawak

The Institution of Engineers, Malaysia

Sarawak Branch

Dr. Naveed Anwar ~

Asian Institute of Technology, AIT ~

Finite Element Analysis and Design of RC Buildings'

May 25-26, 2005

Multi Media Theater, UNIMAS Main Campus

Kota Samarahan, Sarawak

'~---------------------------------,

[ Outline Overview of Computer Aided Analysis and Design of

Buildings

Structural Systems: Types, Selection and Behavior Modeling and Analysis of Buildings in 3D Design of Gravity Load Resisting Systems Design of Lateral Load Resisting Systems Special Modeling Techniques for Shear Walls, Transfer

Girders, Deep Beams, Foundation Systems and Long

Columns

Analysis, Design and Detailing of Foundations Dynamic and Non-linear Analysis for Wind and Earthquake

Loads Pushover Analysis for Performance Based Design Staged Construction Analysis

Finite Element Analysis and Design of RC Buildings - 1

Dr. Naveed Anwar ~ . . ACECOMS

ASian Institute of Technology, AIT

~~------------------------------------.

[ Building Systems Building is an assemblage of various Systems

- Basic Functional System

- Structural System

- HVAC System

- Plumbing and Drainage System

- Electrical, Electronic and Communication System

- Security System

- Other specialized systems


...

Dr. Naveed Anwar ~


The Building Structural System Physical

Diaphragm

Frame and Shear Walls Floor Slab System Lateral Load Resisting System

Gravity Load Resisting System

I ,

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The Building Structural System Conceptual

The Gravity load Resisting System (GLRS) - The structural system (beams, slab, girders, columns, etc)

that act primarily to support the gravity or vertical loads

The Lateral Load Resisting System (LLRS) - The structural system (columns, shear walls, bracing, etc)

that primarily acts to resist the lateral loads

The Floor Diaphragm (FD) - The structural system that transfers lateral loads to the

lateral load resisting system and provides in-plane floor stiffness

~ 6

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_ ....._._._.__ ._.__.. .._......-......... .__.._ ...._.. _ -_......_ .._....._ .. ._.._._._._._._....-... ---....--..-.-..- ..- ..--.--- --_ ..-_ ........_ -_._._..._.__.... .. ...- ._ .... ..... __.._-_......__...._..__...._--_.. -.--..-- ----.-- .--..-~-

[r----st~r~tural System - Analysis Model STRUCTURE

RESPONSESEXCITATION DisplacementsLoads

~ StrainsVibrations ~ StressSettlements

Stress ResultantsThermal Changes

\ I'I Structural Model


Dr. Naveed Anwar ~

Asian Institute of Technology, All ~ -.

~~--------------------------------~

[ The Structural System STRUCTURE

EXCITATION RESPONSES.. 6 P.

Linear Static Elastic Dynamic Inelastic Nonlinear

9 ~SJ

,~------------------------------~

[ Analysis of Structures

P. Real Structure is governed by "Partial Differential Equations" of various order

Direct solution is only possible for: Simple geometry Simple Boundary Simple Loading.

10


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,~--------------------------------~[ The Need for Modeling A - Real Structure cannot be Analyzed:

It can only be "Load Tested" to determine response

B - We can only analyze a "Model" of the Structure

C - We therefore need tools to Model the Structure and to Analyze the Model

----_.._-_. ....__ ..__.._ . - ....-.-. ..--.....- .-.-.-..-.--...--.---.-.---.-.----~-~.. ---

Finite Element Method: The Analysis Tool

Finite Element Analysis

(FEA)

- "A discretized solution to a

continuum problem using FEM"

Finite Element Method

(FEM)

- "A numerical procedure for

solving (partial) differential

equations associated with field

problems, with an accuracy

acceptable to engineers "

12

Finite Element Analiysis and Design of RC Buildings - 6



~~-------------------------------------.[ Continuum to Discrete Model I

Pv ~

3D-CONTINUM CONTINUOUS MODEL DISCRETE MODEL MODEL OF STRUCTURE OF STRUCTURE

(Governed by partial (Governed by either (Governed by algebraic differential equations) partial or total differential equations)

equations) 13

-_ .._--

[,----~F~m C'lassical to FEM Solution .. -------------- -- -- --- ----....

FEMClassical

Actual Structure Structural Model

-- Kr=R

... "Partial Differential "Algebraic Equations "

Equations" fo'edY =JP!iICW+ Jp!iiils. K = Stiffness r = Response

(Principle of Virtual Work) ; R = Loads \4


Dro Naveed Anwar ~


~~------------------------------~

[ Simplified Structural System

Deformations (D) A

D K '+--oJ

F-, ,

F=KD 15

-- .--..... _---- - . . _ .. .. _ 0_ __0"___ - .___

~~--~----------~--------------~

[ The Structural System

STRUCTURE

RESPONSESEXCITATION. A

Pv

Linear Static Elastic Nonlinear Dynamic Inelastic

--_.. _------_....._-- -_.


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Dr. Naveed Anwar ~


~~----~------------------------~[ The Equilibrium Equations 1. Linear-Static Elastic OR Inelastic

Ku=F

2. Linear-Dynamic Elastic

3. Nonlinear - Static Elastic OR Inelastic

4. Nonlinear-Dynamic Elastic OR Inelastic

Mi(t)+CU(t)+Kf{t}+F{t)NL=F(t) ~

~--------------------------------~[ Analysis Type The type of Analysis to be carried out depends on the Structural System

The Type of Excitation (Loads) - The Type Structure (Material and Geometry)

- The Type Response


18

Dr. Naveed Anwar ~


~~-------------------------------------.

[ Some More Solution Types Non-linear Analysis

- P-Delta Analysis

- Buckling Analysis

- Static Pushover Analysis

- Fast Non-Linear Analysis (FNA)

Large Displacement Analysis

Dynamic Analysis - Free Vibration and Modal Analysis

Response Spectrum Analysis

Steady State Dynamic Analysis

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[~----~'~-S-t-at-ic-V-S-D-y-n-am--iC--------~

Static Excitation When tbe Excitation (Load) does not vary rapidly with Time

- When the Load can be assumed to be applied "Slowly"

Dynamic Excitation - Wben tbe Excitation varies rapidly witb Time

- When tbe "Inertial Force" becomes significant

Most Real Excitation are Dynamic but are

considered"Quasi Static"

Most Dynamic Excitation can be converted to

"Equivalent Static Loads"

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Dr. Naveed Anwar ~


,~------------------------------------~[ Elastic Vs Inelastic Elastic Material

Follows the same path during loading and unloading and returns to initial state of deformation, stress, strain etc. after removal of load! excitation

Inelastic Material Does not follow the same path during loading and unloading and may not returns to initial state of deformation, stress, strain etc. after removal of load! excitation

Most materials exhibit both, elastic and inelastic

behavior depending upon level of loading.

Linear Vs Nonlinear

Linearity - The response is directly proportional to excitation

- (Deflection doubles if load is doubled)

Non..Linearity - The response is not directly proportional to excitation - (deflection may become 4 times ifload is doubled)

Non..linear response may be produced by: - Geometric Effects' (Geometric non-linearity)

Material Effects (Material non-linearity)

- Both

Finite Element AnalysiS and Design of RC Buildings - 11



"'

[ Basic Analysis Types excitation Structure Response

Static Elastic Linear

Static Elastic Nonlinear

Static Inelastic Linear

Static Inelastic Nonlinear

Dynamic Elastic Linear

Dynamic Elastic Nonlinear

Dynamic Inelastic Linear

Dynamic Inelastic Nonlinear

23 ~SJ

....... - ............- -

- -_.... .. .. _._....... .. __..._--_ ......_.. __...__.._-.._...._. __... ._..__........_---- _............. __ . _ .-......- ...._. ......... ._._... .........._..._.

[r----~'Some More Solution Types Non-linear Analysis

- P-Delta Analysis

- Buckling Analysis

- Static Pushover Analysis

- Fast Non-Linear Analysis (FNA)

- Large Displacement Analysis

Dynamic Analysis - Free Vibration and Modal Analysis

- Response Spectrum Analysis

- Steady State Dynamic Analysis

24

--- ...._.. --......._... ._--_.................__ ._.........._ ..._._ ... ..........-....-................- .....- ..-.... ......-- . . ..~ Finite Element Analysis and Design of RC Buildings - 12

25

Dr. Naveed Anwar ~

Asian Institute of Technology, AfT ~

[ Elastic Vs Inelastic ] Elastic Material

- Follows the same path during loading and unloading and returns to initial state of deformation, stress, strain etc. after removal of loadl excitation

Inelastic Material - Does not follow the same path during loading and unloading and

may not returns to initial state of deformation, stress, strain etc. after removal of loadl excitation

Most materials exhibit both, elastic and inelastic

behavior depending upon level of loading.

,,---------------------------------------,[ Linear Vs Nonlinear

Linearity - The response is directly proportional to excitation

- (Deflection doubles if load is doubled)

Non-Linearity - The response is not directly proportional to excitation

- (deflection may become 4 times ifload is doubled)

Non-linear response may be produced by: - Geometric Effects (Geometric non-linearity)

- Material Effects (Material non-linearity)

- Both


Dr. Naveed Anwar ~


Elasticity and Linearity

eo linear, but Inelastic o Elastic. but nonlinear e

27

,~------------------------------~[ L~ads to Actions Loads

Load Cases , Load Combinations

Design Envelopes , 28 Design Actions

Finite Element Analysis and Design of RC Buildings ~ 14

I

I Dr. Naveed Anwar ~

Asian Institute of Technology, AIT ~ I I ~~------------------------------~[ Load Cases I Load cases are defined by the user and

used for analysis purpose only

I Static Load Cases I - DeadLoad Live Load

- Wind Load

I Earthquake Load Cases - Response Spectrum Load Cases

I - Time mstory Load Cases Static Non-Linear Load Cases

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~~------------------------------~[ Load CombinationsI I

The Load Combinations may be created by the program, user defined or a combination of both.

Some Examples: [Created by the program]

I - 1.4rOL I

- 1.4rOL + 1.7(LLL + rRLL)

- O.75[1.4rOL + 1.7(LLL +rRLL) + l.7WL]

- O.75[1.4rDL +1.7(LLL + rRLL) 1.7WL] - O.9rOL + 1.3WL

I - O.9rOL - 1.3WL

I

- 1.1 [1.2rOL +O.5{LLl + rRLl) + 1.0E]

- 1.1 [1.2rOL +O.5{LLl + rRlL) 1.0E]

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Dr. Naveed Anwar ~ I


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~~---------------------------------- I[ Obtaining Envelop Results

Combi Comb2 Comb3 ~ombN I

4oad Case1

Iload Case 2

I

load Case 3

Envelop Results Iload Case M

II _ {Max,p}II .'P3.4p.-:I> PN. Totiit]~ Pi P2 Min,P I

I

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Can Envelop Results be Used for Design? I

Actions Interact with each other,

P

Ieffecting the stresses For Column Design: P, Mx, My

For Beam Design: Mx, Vy, l z I

For Slabs: Mx, My, Mxy

At least 3 Actions from each combination

must be considered together as set I

Therefore, Envelop Results Can Not be

Used I,

Every Load Combinations must be used

for design with complete "Action Set"

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IFinite Element Analysis and Design of RC Buildings - 16

I

I Dr. Naveed Anwar ~

. . ACECOMSASian Institute of Technology, AIT

I I ~~--------------~~----------------~ [ Design Actions For Static Loads I

II

For static loads, CombinationsDesign Actions are

I 1/1obtained as the ..J---+---+--+----1lll cumulative result ra .A----t---+--+----1 u from each load '0

I ..J---+---+--+----1g combination, as set ..J for all interacting actions

I The final or critical

I Combinationsresults from design of all load combinations I

33 are adopted

I

I

Static, Dynamic and Nonlinear ResultsI For a Single Action:

I Static Load Case Response Spectrum Load Case I

+

Load Combination1for each Time Step

I TableTime History Load Case OR 1 for envelop

I 1for each Load StepStatic Non-linear Load Case OR 1for Envelop I 34

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I Finite Element Analysis and Design of RC Buildings - 17 I~~-

I Dr. Naveed Anwar ~ I'

A I f T h I ACECOMSsian nstltute 0 I ec no ogy, AIT

~~--------------------------~--------~

[ Special Load Cases Response Spectrum Cases

- All response spectrum cases are assumed to be earthquake load cases

- The output from a response spectrum is all positive.

- Design load combination that includes a response spectrum load case is checked for all possible combinations of signs (+, -) on the response spectrum values

- A 3D element will have eight possible combinations of

P, M2 and M3 and eight combinations for M3, V, T

35

Response Spectrum Results for Action Set

Design Actions needed for Columns:

+P, +Mx, +My +P,+Mx,-My +P, -Mx, +My

Maximum Results obtained by: +P, -Mx,-My

SRSS, CQC, etc.

' f------t... ... -P, +Mx, +My

P,Mx,My> -P, +Mx, -My -P, -Mx, +My

-P, -Mx, -My I

36

Fini,te Element Analysis and Design of RC Buildings - 18

I I I I I I I I I I I I I I I I I I

I I 3>Dr. Naveed Anwar

. . ACECOMS Asian Institute of Technology, AIT

I I L'---~~--me-H-is-to-ry-A-n-al-YS-iS-Re-s-u-lt-s----0

option - 2: Design For All Values I (At each time step) I ,- .. .

.....~~i\;.o~)t Lt:'~L...w jl~~~j~-.l It...i...;~~ ~1,.ll'.rnl.~I'.nlnI .at.J.I'Jrll'rJ~1 7."II7""f'!r-~~~~r~""~r)""r.!l~f!'!'p::!~

I Response Curve for One Action

I I

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I - - _ . _ ---I

Max Val

Option -1: Envelope Design

Min Val

~~-----------------------------------~

[ Time History ResultsI I

The default design load combinations do not include any time history results

Define the load combination, to include time history forces in a design load combination

I Can perform design for each step of Time

History or design for envelops for those resultsr-;;:;;;;;:;;;=;::;;:;;:;;;;:;;;:;;::;;;:;;;;;;;;

I For envelope design, the design is for the maximum of each response quantity (axial

load, moment, etc.) as if they occurred

simultaneously.

Designing for each step of a time history gives correct correspondence between different response quantities

38

I Finite Element Analysis and Design of RC Buildings - 19

I


ASian Institute of Technology I AIT

I

"--~------------------------------------, I[ Time History Results

- ...:. The program gets a maximum and a minimum value for each I

response quantity from the envelope results for a time history

I- For a design load combination any load combination that

includes a time history load case in it is checked for all possible

combinations ofmaximum and minimum time history design

values. I

- If a single design load combination has more than one time Ihistory case in it, that design load combination is designed for

the envelopes of the time histories, regardless of what is

specified for the Time History Design item in the preferences I

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[~--~" Static Non Linear Results I

- The default design load combinations do not include any

Static Nonlinear results I

- Define the load combination, to include Static Nonlinear

Results in a design load combination I

For a single static nonlinear load case the design is performed for each step of the static nonlinear analysis. I

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I I Dr. Naveed Anwar ~


Wind load Cases

At least 3 basic Wind Load Cases should be considered - Along X-Direction

I - Along Y Direction - Along Diagonal Each Basic Wind Load Case should

I be entered separately into load combinations twice, once with (+ve) and once with (-ve) sign

I Total of 6 Wind Load Cases should

I considered in Combinations, but only 3 Load Cases need to be defined and analyzed

Wx~

41

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I['---~'Wind load CombinationsI

I

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(t) Is the load factor specified for Example:

I Wind in the design codes Comb = O.75(1.4D + 1.7W) will

need Six Actua]' Combinations

Six Additional Load Combinations Combl= O.75(1.4D + 1.7Wx)

are required where ever "Wind" is Comb2 = O.75(1.4D - 1.7Wx)

I mentioned in the basic Load! Comb3 = O.75(1.4D + 1.7Wy)Combinations I

Comb4 = O.75(1.4D - 1.7Wy)

Comb5 = O.75(1.4D + 1.7Wxy)

Comb6 = O.75(1.4D - 1.7Wxy)

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I Finite Element Analysis and Design of RC Buildings - 21 I

http:O.75(1.4Dhttp:O.75(1.4Dhttp:O.75(1.4Dhttp:O.75(1.4Dhttp:O.75(1.4Dhttp:O.75(1.4Dhttp:O.75(1.4D

I -

Dr. Naveed Anwar ~ I

Asian Instltute 0f TechnoIogy, AIT ACECOMS

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I~~-----------------------------------,

[ The Building Structural System I

The Gravity Load Resisting System (GLRS) - The structural system (beams, slab, girders, columns, etc)

that act primarily to support the gravity or vertical loads I

The 'lateral Load Resisting System (LLRS)

- The structural system (columns, shear walls, bracing, etc) I

that primarily acts to resist the lateral loads

The Floor Diaphragm (FD) I- The structural system that transfers lateral loads to the

lateral load resisting system and provides in-plane floor

stiffness I

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Finite Element Analysis and Design of RC Buildings - 22 I

I

I I Dr. Naveed Anwar ~


I I ~~----------------------------------~[ Main Slab Types: Usage I Buildings

- Flat Slabs, One way Slabs, Two way Slabs

I - Isolated Footings, Combined Footings, Rafts - Pre-cast slab panels, hollow core slabs

I Bridges and Highways Deck Slab on Girders - Box Girder Slabs

I - Slab on Grade: Pavements, Approach Slabs, Water Retaining Structures

I - Retaining Wall Systems - Tank Roof and Floor slabs I

45

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~~------------------------------------~[ Basic DefinitionI Plate

I - Any member, or part of member whose thickness is much less than its other dimensions Slab

I - A plate resting on supports, generally horizontal and transferring vertical loads directly.

I Slab System

I A combination of various components, such as slabs, beams, drop panels, stiffeners, joists, girders, ribs, all acting together to transfer the loads to supports

I 46

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I Finite Element Analysis and Design of RC Buildings - 23 II

Seminar on Finite Element Analysis and Design of RC Building.pdf

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