Mechanics Based Modeling of Mechanics Based Modeling of the Dynamic Response of Wood the Dynamic Response of Wood

Frame BuildingFrame Building

By

Ricardo Foschi, Frank Lam,Helmut Prion, Carlos Ventura Henry He and Felix Yao

University of B.C.

CUREe-Caltech Woodframe Project

Element 1 - Researchers Meeting

University of California, San Diego

January 2001

UBC

UBC Research Project: UBC Research Project: Reliability and Reliability and Design of Innovative Wood Design of Innovative Wood

Structures under Earthquake and Structures under Earthquake and Extreme Wind ConditionsExtreme Wind Conditions

Combined analytical and experimental studies to evaluate the performance of wood frame structures

Reliability procedures to consider the randomness of loading and system response

Funded by Forest Renewal BC Collaborations with CUREe-Caltech Woodframe Project

UBCUBC TEAMTEAM

Principal researchers: R.O. Foschi, F. Lam, H. Prion, & C. Ventura

F. Yao, H. Li, Y.T. Wang – Structural Analysis, Reliability H. He - Modeling and testing of simple 3D structures M. Popovski - Glulam frames D. Moses, N. Allotey, A. Schreyer - Nail & bolted connections R. Mastschuch, B. Sjoberg - Reinforced bolted connections N. Richard, P. Welzel - Openings M. Stefanescu, G. Finckenstein - Japanese Post & Beam Frames Full scale shake table testing of 2 storey buildings

3-D Model of Wall Systems3-D Model of Wall Systems

Develop and verify 3D structural analysis model with mechanics based nail hysteresis subroutine– Model Development– Input Data– Full Scale Test Data

Completed verification of static, cyclic and dynamic behaviour (2D)

Completed verification of static behaviour (3D)

– (PI: ROF, FL – HH)

Wind Load

Lateral Load

Vertical Load

Double-side Panels

Frame

Nails

Insulation

Structural ModelStructural Model

Light-frame building structure

Sandwich diaphragm type components with optional insulation layer

Wide range of material properties

Multiple load inputs Load/displacement

control

Structural ModelStructural Model Element types

Panel - 4-node elastic orthotropic plate element Frame - 3D elastic beam element Nail - nonlinear spring element in x, y, z directions

Substructuring used in local-global transformations Performed only in frame elements and connections to frame

DOF in panel and frame elements

Nx

Ny

Mx

My

dx

dy

x,u

y,v

z,w

Rot-x

Rot-y

Rot-z

Mxy

Mxy

dx

dy

x

y

z

Pure twistDisplacements & rotations

qdxdy

Mechanics Based Nail HysteresisMechanics Based Nail Hysteresis

Beam elements (nail) on nonlinear foundations (panel and frame)

Basic material properties– Non-linear Stress Strain Behaviour of

the steel

– Non-linear Embedment Properties of the Wood

Hysteresis behaviour

Cyclic BehaviourCyclic Behaviour

Mechanics based nail model was implemented into 3D program

Single nail case compared to test results Pinched and asymmetric hysteresis loops Stiffness and strength degradations

Possible issues Solution Stability Model Calibration Material Properties

Mechanics-Based Nail ModelMechanics-Based Nail ModelUBC_HYST_TEST

-1500

-1000

-500

0

500

1000

1500

-30 -20 -10 0 10 20 30

DISP_mm

LOAD_N

HYST_UBC TEST_UBC

ISO_HYST_TEST

-1500

-1000

-500

0

500

1000

1500

-30 -20 -10 0 10 20 30

DISP_mm

LOAD_N

HYST_ISO TEST_ISO

NEARFAULT_HYST_TEST

-1500

-1000

-500

0

500

1000

1500

-30 -20 -10 0 10 20 30

DISP_mm

LOAD_N

HYST_NF TEST_NF

STANFORD_HYST_TEST

-1500

-1000

-500

0

500

1000

1500

-30 -20 -10 0 10 20 30

DISP_mm

LOAD_N

HYST_STAN TEST_STAN

0

20

40

60

80

100

120

140

0 20 40 60 80 100

Wall 6 Wall 1

Wall 3

-150

-100

-50

0

50

100

150

-80 -60 -40 -20 0 20 40 60 80

Cyclic Test

Monotonic Test

Monotonic and Cyclic Tests of 7.2 m WallMonotonic and Cyclic Tests of 7.2 m Wall

Monotonic and Cyclic Tests of 2.4 m WallsMonotonic and Cyclic Tests of 2.4 m Walls

      

40

30

20

10

0

200 100806040

Wall 5

Wall 3

Wall 1

40

20

0

-20

-40

-40-80 80400

MonotonicTest

Cyclic Test

Model VerificationModel Verification- Monotonic Case 1- Monotonic Case 1

Model VerificationModel Verification- Monotonic Case 2- Monotonic Case 2

Model VerificationModel Verification- Cyclic Case 1- Cyclic Case 1

Model VerificationModel Verification- Cyclic Case 2- Cyclic Case 2

Model PredictionsModel Predictions- Cyclic Case- Cyclic Case

Shake Table Test set up of 2.4 wallShake Table Test set up of 2.4 wall

Support frame

Shake table

LongitudinalactuatorVertical

actuators

Shear wallspecimen

Distributionbeam

Inertia masses

Model VerificationsModel Verifications

Shear Wall

Fundamental Frequency

Experimental Results (Hz)

Model Predictions (Hz)

Jtest 10a – 2.4x2.4 Jumbo Panel

4.5 4.0

Jtest 11 – 1.2x2.4 Regular Panels

3.3 2.9

Model VerificationsModel Verifications

  Jtest11

 Regular Panel

Jtest10a

Jumbo Panel 

   Test Model  Test    Model

Displ. (mm)

60.0 61.9 14.1 22.4

Accel. (g)

0.42 0.52 0.52 0.40

Model VerificationModel Verification- Dynamic Case 2D- Dynamic Case 2D

Model PredictionsModel Predictions- 3-D Static Response- 3-D Static Response

Model of an Eccentric StructureModel of an Eccentric Structure

Specimen DetailsSpecimen Details

Model VerificationModel Verification- Static Case 3D- Static Case 3D

3D Model Verification 3D Model Verification Vibration FrequenciesVibration Frequencies

Vibration Mode Experimental Results (Hz)

Model Predictions (Hz)

No.1 (Sway Motion E-W)

2.9 2.8

No.2 (Sway Motion N-S)

5.0 6.1

No.3 (Torsion) 8.8 8.8

Model VerificationModel Verification- Dynamic Case 3D - Dynamic Case 3D

Single Component ShakingSingle Component Shaking

-100

-50

0

50

100

0 5 10 15 20 25 30 35 40 45

Time (sec)

Drift (mm)

Test FEA

-0.50

-0.25

0.00

0.25

0.50

0 5 10 15 20 25 30 35 40 45

Time (sec)

Acce. At Top (g)

Test

FEA

Failed Shake Table SpecimenFailed Shake Table Specimen

Failed Shake Table SpecimenFailed Shake Table Specimen

3D Simplified Model Test 3D Simplified Model Test ObservationsObservations

Significant torsional response Single Component Shaking (~0.4g pga)

– Damage initiated in the narrow wall– Adjacent long wall was also severely damaged– Significant softening after 1st pulse

Two Component Shaking (~0.26g pga)– Two side walls were severely damaged– Significant softening after 1st pulse

Summary on Model DevelopmentSummary on Model Development

Modeling/analytical procedures Program calibrations and verification (Dynamic case) Study of structural parameters and performance

• Experimental procedures Verification of 3D finite element program

Static Dynamic

Reliability based design procedures Response Surfaces Approaches

UBC’s Large Shake TableUBC’s Large Shake Table

20 ft by 25 ft rigid frame

Low friction roller bearings

67 kip, 36 inch actuator

Subsystem Subsystem testingtesting

Simulated weight of 2nd floor

Two Storey House TestTwo Storey House Test