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midas Gen – One Stop Solution for Building and General Structures
Pushover Analysis
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar
Webinar Schedule
Topics Presenter Date
February
Basic Product Introduction & General Use Yaman 2/14, Tue
Advanced Concrete Building Design (Beam, Column, Wall, Slab) Ravi 2/28, Tue
March
Basic Product Introduction & General Use Yaman 3/13, Tue
Advanced Steel Structure Design Ravi 3/27, Tue
April
Basic Product Introduction & General Use Yaman 4/10, Tue
Advanced Pushover Analysis Ravi 4/24, Tue
May
Basic Product Introduction & General Use Yaman 5/15, Tue
Advanced Time History Analysis Ravi 5/29, Tue
June
Basic Product Introduction & General Use Yaman 6/12, Tue
Advanced Construction Stage Analysis & Column Shortening Ravi 6/26, Tue
midas Gen – One Stop Solution for Building and General Structures
Pushover Analysis
Webinar Objective
Methods of Analysis for Earthquake Resistant Structures
Introduction to Pushover Analysis
Pushover Analysis of RC Building
Pushover Analysis of Steel Building
Conclusion
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar
1. Introduction to Pushover Analysis.
2. Discussion of Features available in midas Gen for Pushover
Analysis.
3. Live demonstration of performing pushover analysis and
interpretation of results.
4. At the conclusion of the webinar attendees will be familiar with
pushover analysis and midas Gen applicability to it.
Objective
midas Gen – One Stop Solution for Building and General Structures
Pushover Analysis
Webinar Objective
Methods of Analysis for Earthquake Resistant Structures
Introduction to Pushover Analysis
Pushover Analysis of RC Building
Pushover Analysis of Steel Building
Conclusion
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Methods of Analysis for Earthquake Resistance Structures
Design Methods
Force Based Design
• Elastic Response Acceleration is determined form the estimated structural period and given design
elastic response spectrum.
• Modified design acceleration is obtained by dividing the Elastic Response Acceleration by Response
Reduction Factor (R)
• Design Force is calculated using modified design acceleration.
• Displacement Check is made after the structural members satisfy the Force requirements.
Problems :-
• The distribution of design forces are based on initial estimate of stiffness and as stiffness is dependent
on the strength of elements, this cannot be know until the design process is complete.
• Distribution of seismic forces between elements based on initial stiffness is illogical, as it incorrectly
assumes different elements can be forced to yield simultaneously.
• Ductility capacity is a function of structural geometry, not just of structural type. Hence it is inappropriate
to specify a same displacement ductility factor for all structures of the same type.
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Methods of Analysis for Earthquake Resistance Structures
Design Methods
Performance Based Design/ Displacement Based Design
• Importance of deformation rather than strength in seismic performance is gaining more popularity in
recent times due to the deficiencies inherent in the force-based system of seismic design.
• The design is carried out by specifying a target displacement.
• There is no need to use a force reduction factor
• The inelastic nature of the structure during a earthquake is directly addressed.
• Displacement based design procedure can provide a reliable indication of damage potential.
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Methods of Analysis for Earthquake Resistance Structures
Analysis Methods
Linear
Static
Equivalent Lateral Load
Small Displacement
Dynamic
Response Spectrum Analysis
Small Displacement
Linear Response History Analysis
Small Displacement
Nonlinear
Static
Equivalent Lateral Load
Small or Large Displacement
Dynamic
Nonlinear Response History Analysis
Small or Large Displacement
Sequential Yield Analysis
Pushover Analysis
midas Gen – One Stop Solution for Building and General Structures
Pushover Analysis
Webinar Objective
Methods of Analysis for Earthquake Resistant Structures
Introduction to Pushover Analysis
Pushover Analysis of RC Building
Pushover Analysis of Steel Building
Conclusion
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Why Pushover Analysis
• Pushover Analysis in the recent years is becoming a popular method of predicting seismic
forces and deformation demands for the purpose of performance evaluation of existing and
new structures.
• Pushover analysis is a partial and relatively simple intermediate solution to the complex
problem of predicting force and deformation demands imposed on structures and their
elements by severe ground motion.
• Pushover analysis is one of the analysis methods recommended by Eurocode and FEMA
273.
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Why Pushover Analysis
• Pushover analysis provides valuable insights on many response characteristics like
• Force Demand on Potentially brittle elements.
• Consequences of strength deterioration of individual elements on structural behavior.
• Identification of critical regions in which the deformation demands are expected to be
high and that have to become the focus of through detailing.
• Identification of strength discontinuities in plan or elevation that will lead to changes in
dynamic characteristics in the inelastic region.
• Verification of completeness and adequacy of load path, considering all structural and
non structural elements of the structural system.
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
What is Pushover Analysis
- Is a technique by which a structure is subjected to a incremental lateral load of certain
shape.
- The sequence of cracks, yielding, plastic hinge formation and failure of various
structural components are noted.
- The structural deficiencies are observed and rectified.
- The iterative analysis and design goes on until the design satisfies a pre-established
criteria.
- The performance criteria is generally defined as Target displacement of the structure
at roof level.
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Performance Level
- Performance Level is defined as the expected behavior of the building in the design
earthquake in terms of limiting levels of damage to the structural and nonstructural
components
- The limiting condition is described by the physical damage within the building, the
threat to life safety of the building’s occupants created by the damage, and the post
earthquake serviceability of the building.
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Performance Level
• This is the performance level related to functionality and any required repairs are minor.
Operational Level
• This corresponds to the most widely used criteria for essential facilities. The building’s spaces and systems are expected to be reasonably usable
Immediate Occupancy level
• This level is intended to achieve a damage state that presents an extremely low probability of threat to life safety, either from structural damage or from falling or tipping of nonstructural building component
Life Safety Level
• This damage state addresses only the main building frame or vertical load carrying system and requires only stability under vertical loads.
Collapse Prevention Level
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Seismic hazard
Seismic Hazard is a function of
- The Building Performance level
- The Mapped Acceleration Parameters
- The Site Class Coefficients
- The Effective structural damping
- The fundamental Structural Period
The general response spectrum is formulated
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Target Displacement
The Target displacement is calculated by
dt = C0C1C2C3SaTe2g/4p2
where:
C0 = Modification factor for SDOF MDOF
C1 = Modification Factor to relate expected maximum inelastic displacements to
displacements calculated for liner elastic response
C2 = Modification factor to represent the effect of hysteresis shape on the
maximum displacement response
C3 = Modification Factor to represent increased displacements due to dynamic P-
effects.
Sa = Response spectrum acceleration
Te = Characteristic period of the response spectrum.
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Reasons for Performing Pushover Analysis
Why Pushover Analysis over Nonlinear Dynamic Analysis
• To run a full dynamic, non – linear analysis on even a simple structure takes a long
time. But with pushover analysis accurate results can be obtained in fractions of the
time it would take to get any useful results from the fully dynamic analysis.
• When performing a dynamic analysis, it is best to use a series of earthquakes. The
Pushover Analysis naturally accounts for all earthquakes with the same probability of
exceedance by predicting the maximum displacement that can be expected in the
form of the Target Displacement.
midas Gen – One Stop Solution for Building and General Structures
Pushover Analysis
Webinar Objective
Methods of Analysis for Earthquake Resistant Structures
Introduction to Pushover Analysis
Pushover Analysis of RC Building
Pushover Analysis of Steel Building
Conclusion
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Pushover Analysis Procedure
Pushover Global Control
Define Lateral Loads
Define Hinge Properties
Assign Hinges Perform Analysis
Check Pushover Curve and
Target Disp.
Check Hinge Status
Safety Verification
Process in midas Gen
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
RC Model
15
@3
,00
0 =
45
,00
0
9000 9000
27200
4000 40001200
unit : mm
C1 C1
G1 LB1 G1
Designation Story Section Number Column Dimension
C1
12~15F
8~11F
4~7F
1~3F
104
103
102
101
500 x 500
600 x 600
700 x 700
800 x 800
Designation Section Number Section Dimension
G1 21 350 x 600
LBl 31 200 x 300
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Hinge Properties
0
0.2
0.4
0.6
0.8
1
1.2
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04
Mo
men
t/S
F
Rotation/SF
Hinge Property
A
B C
D E
IO LS
CP
B - Yield State
IO – immediate Occupancy
LS – Life Safety
CP – Collapse Prevention
C – Ultimate State
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Pushover Curve
Roof Displacement (U)
Base S
hear
(V)
Pushover Curve
Spectral Displacement (Sd)
Spectr
al A
ccele
ration
(Sa)
Capacity Spectrum
roofroofd
a
PFS
WVS
,1
1
1*/
//
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Demand Spectrum
Spectr
al A
ccele
ration
Time Period
T0
Sd = SaT2/4p2
Acceleration Vs Time Period
Spectr
al A
ccele
ration (
Sa)
Spectral Displacement (Sd)
T0
Acceleration Vs Displacement
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Performance Point
S
pe
ctr
al A
cce
lera
tio
n
Spectral Displacement
Demand Spectrum for effective
damping at performance point
Capacity Spectrum
midas Gen – One Stop Solution for Building and General Structures
Pushover Analysis
Webinar Objective
Methods of Analysis for Earthquake Resistant Structures
Introduction to Pushover Analysis
Pushover Analysis of RC Building
Pushover Analysis of Steel Building
Conclusion
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Steel Model
Figure 3. Elevation
Figure 1. Three-dimensional structural model
6,0
00
10,000
2,500 2,500 2,500 2,500
A
B
1 2 3
G2
G2
G2G2
C2 C2
C2C2 C1
C1
G1
G1
G1
BR
BR
3,000
3,000
3,000
9,000
BR1
BR1
BR2
Figure 2. Structural plan
Section Name Section ID Section DB Section Size
C1 1 UNI HEA240
C2 2 UNI HEA300
G1 21 UNI HEA280
G2 22 UNI IPE240
Brace1 31 UNI HEA160
Brace2 32 UNI HEA120
midas Gen – One Stop Solution for Building and General Structures
Pushover Analysis
Webinar Objective
Methods of Analysis for Earthquake Resistant Structures
Introduction to Pushover Analysis
Pushover Analysis of RC Building
Pushover Analysis of Steel Building
Conclusion
One Stop Solution for Building and General Structures Midas Gen – Advanced Webinar Introduction
Conclusion
- Pushover Analysis is a very useful tool for the evaluation of New and existing structures.
- Pushover Analysis provided much useful information that cannot be obtained from elastic
static and dynamic analysis.
- Pushover Analysis provides a relatively simple solution than nonlinear Dynamic analysis
and more realistic and comprehensive solution than linear elastic analysis.
- Push over analysis require considerable amount of understanding of the subject by the
engineer.
- Pushover analysis is approximate in nature and is based on static loading and it cannot
represent the dynamic phenomena with a large degree of accuracy.
- Pushover Analysis does not create good solutions, it only evaluates solution.
- Load pattern choice makes a huge difference to the analysis results.
midas Gen – One Stop Solution for Building and General Structures
Q & A