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midas Gen

midas Gen

Advanced Webinar

Dynamic Analysis

MIDAS Information Technology Co., Ltd. 2

Integrated Design System for buildings and General StructuresWhy midas GenWhy midas Gen

Stadiums

Power Plants

Hangar

Airport

Transmission

Towers

Cranes

Pressure Vessels

Machine Structures

Underground

Structures …

Versatility

Specialty Structures Applications

Beijing National Stadium Beijing National Aquatic Center Beijing Olympic Basketball Gymnasium

Seoul World Cup Stadium JeonJu World Cup Stadium DeaJeon World Cup Stadium

USA Pavilion China Pavilion German Pavilion

midas Gen

Contents

1. Seismic Design for New Buildings

2. Seismic Design for Existing Buildings

3. Base Isolators and Dampers

4. Mass

5. Damping

6. Modal Analysis

7. Fiber Analysis

One Stop Solution for Building and General Structures

4

Seismic Design Flowchart (New Buildings)

Seismic Design Process as per Eurocode8 (New buildings)

Seismic Design

Performance RequirementPerformance Requirement

Ground ConditionGround Condition

Seismic ActionSeismic Action

Combination of Seismic ActionCombination of Seismic Action

Criteria for Structural RegularityCriteria for Structural Regularity

Seismic AnalysisSeismic Analysis

Safety VerificationSafety Verification

Capacity Design & DetailingCapacity Design & Detailing

•Seismic Zone•Representation of seismic action

[Method of Analysis][Method of Analysis]•Lateral Force method of Analysis•Modal Response Spectrum Analysis•Pushover Analysis•Inelastic Time History Analysis


5

Performance Requirement and Compliance Criteria


No-collapseTNCR=475 yearW/O limitation of collapse

Damage LimitationTDLR=95 yearW/O limitation of use

Compliance CriteriaCompliance Criteria

Ultimate limit statesResistance and Energy Dissipation Capacity need to be checked.

Global level verificationOverturningSliding

Member LevelDuctile component: Plastic RotationBrittle component: Resistance

Damage limitation statesGlobal Level: Inter-story driftMember Level: Resistance (ULS)

Seismic Design Flowchart (New Buildings)Seismic Design


6

Ground Conditions



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Seismic action

I II III IV

T=475 year 0.8 1.0 1.2 1.4

Importance FactorImportance Factor

Representation of Seismic ActionRepresentation of Seismic Action

a. Response Spectrum

- Horizontal elastic response spectrum

- Vertical elastic response spectrum

- Horizontal design response spectrum (Behavior factor, q, is considered.)

- Vertical design response spectrum (Behavior factor, q, is considered.)

b. Time history

[Horizontal Elastic Spectrum]



8

Combination of Seismic Action

•Load Combination of permanent loads and variable loads

•100:30 Rule(1.0Ex + 0.3Ey), (0.3Ex + 1.0Ey)

(1.0Ex + 0.3Ey + 0.3Ez ), (0.3Ex + 1.0Ey + 0.3Ez), (0.3Ex + 0.3Ey + 1.0Ez)



9

Criteria for Structural Regularity

Structural RegularityStructural Regularity

Analysis MethodAnalysis Method

•Lateral Force method of Analysis

•Modal Response Spectrum Analysis

•Pushover Analysis

• Inelastic Time History Analysis



10

Safety Verification

Ultimate Limit States

Resistance condition: MRd >= MEd, VRd >= VEd

Global and local ductility condition: MRc >= 1.3 MRb

Equilibrium condition : overturning or sliding Resistance of horizontal diaphragmResistance of foundationsSeismic joint condition

Damage limitation

Limitation of story drift



11

Capacity Design

Ductility ClassDuctility Class

DCL (Low ductility)

DCM (Medium ductility)

DCH (High ductility)

Structure Type & Behavior FactorStructure Type & Behavior Factor



12

Design Procedure

Capacity Design Feature

• structures to provide the appropriate amount of ductility in the corresponding ductility classes.• Automatic capacity design capability for beam, column, wall and beam-column joint• EN 1998-1: 2004 (DCM/DCH), NTC2008 (CD “B”, CD “A”), ACI318-05• Design action effects are calculated in accordance with the capacity design rule. Special provision for

ductile primary seismic walls is considered.• Detailing for local ductility is considered.

- max/min reinforcement ratio of the tension zone- the spacing of hoops within the critical region- mechanical volumetric ratio of confining hoops with the critical regions

Capacity design shear forces on beams

Define ductility class and check design results Design envelope moments in walls


13

Design Procedure

Design member forces (Design moments)

Where,

MRb: Beam moment resistance

Mce : column member force due to seismic load case


14

Design Procedure

Design member forces (Design shear forces)

Capacity design values of shear forces on beams

Capacity design shear force in columns

Where, MRb: Beam moment resistance

MRc: Column moment resistance

(calculated using same axial force

ratio in PM interaction curve)

Mce: Bending moment of column due to

seismic load case


15

Design Procedure

Design envelope for bending moments in slender walls Design envelope of the shear forces in the walls of a dual system

Design member forces (Wall design forces)

Wall systems Dual systems


16

Seismic Assessment of Buildings as per Eurocode8 (Existing buildings)


Knowledge LevelKnowledge Level

Seismic ActionSeismic Action

Combination of Seismic ActionCombination of Seismic Action

Seismic AnalysisSeismic Analysis

Safety VerificationSafety Verification

Decision for Structural InterventionDecision for Structural Intervention

•Seismic Zone•Representation of seismic action

[Method of Analysis][Method of Analysis]•Lateral Force method of Analysis•Modal Response Spectrum Analysis•Pushover Analysis•Inelastic Time History Analysis

Seismic Design Flowchart (Existing Buildings)Seismic Design


17

Performance Requirement and Compliance Criteria


Near Collapse (NC) TNCR=2475years

Significant Damage (SD) TNCR=475years

Damage Limitation (DL) TNCR=225years

Compliance CriteriaCompliance Criteria

Near Collapse (NC) Ductile: ultimate deformation (plastic rotation)Brittle: ultimate strength

Significant Damage (SD) Ductile: damage-related deformationBrittle: conservatively estimated strength

Damage Limitation (DL) Ductile: yield strengthBrittle: yield strengthInfills: story drift



18

Knowledge Levels



19

Pushover Analysis

Why Pushover Analysis?Why Pushover Analysis?

a) To verify or revise the over strength ratio values (alpha_u/alpha_1)

b) To estimate the expected plastic mechanisms and the distribution of damage

c) To assess the structural performance of existing or retrofitted buildings

d) As an alternative to the design based on linear-elastic analysis which uses the

behavior factor, q

alpha_u

alpha_1

Hinge status for alpha_uHinge status for alpha_1

Pushover Global Control

Define Lateral Loads

Define Hinge Properties

Assign HingesPerform Analysis

Check Pushover Curve and

Target Disp.

Check Hinge Status

Safety Verification

Process in midas GenProcess in midas Gen



20

Safety Verification



21

Base Isolators and Dampers

Base Isolators and Dampers

Dynamics

Objectives of Seismic Isolation Systems

Enhance performance of structures at all hazard levels by:

Minimizing interruption of use of facility (e.g., Immediate Occupancy Performance Level)

Reducing damaging deformations in structural and nonstructural components

Reducing acceleration response to minimize contents related damage

Characteristics of Well-Designed Seismic Isolation Systems

Flexibility to increase period of vibration and thus reduce force response

Energy dissipation to control the isolation system displacement

Rigidity under low load levels such as wind and minor earthquakes


22

Base Isolators and DampersDynamics

Base Isolators:

Lead Rubber Bearing Isolator

Friction Pendulum System Isolator

Applicable Base Isolators in midas Gen


23

[Viscoelastic Damper][Viscoelastic Damper] [Hysteretic System Damper][Hysteretic System Damper]

Applicable Dampers in midas Gen



24

Analysis Results (Graph & Text output)


[Hysteretic Graph of Friction pendulum system isolator][Hysteretic Graph of Friction pendulum system isolator]

[Hysteretic Graph of Lead rubber bearing isolator][Hysteretic Graph of Lead rubber bearing isolator]

[Time History Graph at 1st story and 3rd story][Time History Graph at 1st story and 3rd story]


25

[Without Isolators][Without Isolators]

[With Isolators][With Isolators]

Shear force at 1st story column Displacement - Frequency

Displacement - FrequencyShear force at 1st story column


Analysis Results (Time History Graph)


26

Mass

• Nodal Masses

• Floor Diaphragm Masses

• Loads to Masses

• Consistent Mass

• Self-weight to Mass

[Lumped Mass and Consistent Mass][Lumped Mass and Consistent Mass]

Lumped MassLumped Mass

Consistent MassConsistent Mass

MassDynamics

210 0 0 0 0 0 1

0 210 0 0 0 0 1

0 0 210 0 0 0 1

0 0 0 210 0 0 2420

0 0 0 0 210 0 2

0 0 0 0 0 210 2

L

u

ALI

u

2 2

2 2

140 0 0 70 0 0 1

0 156 22 0 54 13 1

0 22 4 0 13 3 1

70 0 0 140 0 0 2420

0 54 13 0 156 22 2

20 13 3 0 22 4

c

u

L L

L L L LALI

u

L L

L L L L

ν1 ν2

u1 u2

θ1 θ2

1 2


27

Damping

Modal

User defines the damping ratio for each mode, and the modal response will be calculated based on the user defined damping ratios.

Mass & Stiffness ProportionalDamping coefficients are computed for mass proportional damping and stiffness proportional damping.

Strain Energy ProportionalDamping ratios for each mode are automatically calculated using the damping ratios specified for element groups and boundary groups in Group Damping, which are used to formulate the damping matrix.

DampingDynamics


28

Modal Analysis

Eigen Vectors

Subspace Iteration

This method is effectively used when performing eigenvalue analysis for a finite element system of any scale and

commonly used among engineers.

Lanczos

Tri-diagonal Matrix is used to perform eigenvalue analysis. It is particularly useful for finding decompositions of

very large sparse matrices. The performance of Lanczos method is superior to that of the Subspace Iteration.

Ritz Vectors

Unlike the natural eigenvalue modes, load dependent Ritz vectors produce more reliable results in dynamic analyses

with relatively fewer modes. The Ritz Vectors are generated reflecting the spatial distribution or the characteristics of the

dynamic loading.

Modal AnalysisDynamics


29

Fiber Analysis

Fiber Cell Result PlottingFiber Cell Result PlottingSection division for Fiber Model definitionSection division for Fiber Model definition

Kent & Park Model Menegotto-Pinto Model

Inelastic Material Properties (Stress-strain curve)Inelastic Material Properties (Stress-strain curve)

Fiber AnalysisDynamics

Thank You!Thank You!Thank You!


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