EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Performance-Based Earthquake Engineering for Geotechnical and Structural Engineers
Mike Mahoney, FEMA
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Introductory remarksImpact of Soil-Structure Interaction on Response of Structures
Seminar 1: Practical Applications to Shallow Foundations
Craig D. Comartin
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
EERI Technical Seminars
BackgroundGeo-Structural Series
• Current: SSI and shallow foundations• Future Subjects:
Deep foundationsLiquefactionBasement wallsGround motions
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Related documentsATC-40 (1996): The Seismic Evaluation and Retrofit of Concrete Buildings
FEMA 273/274 (1997) and FEMA 356 (2000):Prestandard and Commentary for the Seismic Rehabilitation of Buildings
FEMA 440 (2005): Improvement of Nonlinear Static Seismic Analysis Procedures
ASCE 41: Seismic Rehabilitation of Existing Buildings
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
FEMA 356/ASCE 41
Inertial effectsFoundation stiffness and strengthRadiation damping
Kinematic effectsBase slab averaging (x,y)Embedment (z)
Soil–Structure Interaction
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Structure
Concrete shear wall
Concrete frame
Spread footings
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Analysis model
k v2k v3
K h3
K h2K h1
k v1
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Geotechnical component behavior
Force, Q
Displacement, Δ
Qlower c
upper Q c
Khigh
Q
KlowActualBehavior
Envelope Stiffness, K=Q
Δ
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Nonlinear static procedures(Push-over analysis)
Equivalent Linearization Displacement Modification
ATC- 40Capacity Spectrum Method
(CSM)
FEMA-356Displacement Coefficient
Method (DCM)
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
1. Neglecting ascending branch of design spectra 2. Incoherent input to relatively large plan
dimensions 3. Embedment (basements) 4. Radiation and material damping in supporting
soils5. Concentrating building masses at floor and
roof levels
Factors that affect response of short period buildings
SSI EFFECTSSSI EFFECTS
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
FEMA 440/ASCE 41
FEMA 440/ASCE 41
FEMA 440/ASCE 41
FEMA 356/ASCE 41
Inertial effectsFoundation stiffness and strengthRadiation damping
Kinematic effectsBase slab averaging (x,y)Embedment (z)
Soil–Structure Interaction
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Effects of Foundations on Performance
Foundation stiffness and strength affectvarious structural components differently.
Δ, small
Stiff and Strong Foundation
Smalldisplacementsprotect framefrom damage
High forcescause shearwall damage Δ, large
Flexible and Weak Foundation
Largedisplacementscause frame
damageFoundationyielding androcking protectsshear wall
Stiff and strong is not always favorable;nor is flexible and weak always conservative.
Foundation stiffness and strength affectvarious structural components differently.Foundation stiffness and strength affectvarious structural components differently.
Δ, smallΔ, smallΔ, small
Stiff and Strong Foundation
Smalldisplacementsprotect framefrom damage
High forcescause shearwall damage
High forcescause shearwall damage Δ, largeΔ, largeΔ, large
Flexible and Weak Foundation
Largedisplacementscause frame
damage
Largedisplacementscause frame
damageFoundationyielding androcking protectsshear wall
Stiff and strong is not always favorable;nor is flexible and weak always conservative.
Stiff and strong is not always favorable;nor is flexible and weak always conservative.
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Example building
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Shear wall and frame
77 ft.
20.5 ft. typ.
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Fixed base NSPInelastic mechanism controlled by shear in walls
Displacement demand
EERI TechnicalSeminar Series
Impact of Soil-Structure Interaction on Response of StructuresSeminar 1: Practical Applications to Shallow Foundations
Flexible base NSPInelastic mechanism controlled by pile yielding
Displacement demand