Project #4 Energy Dissipation Capacity of a Wood-frame Shear Wall CEE Numerical Analysis

Session Objectives Provide background on the performance of wood-frame structures subjected to earthquakes (Northridge) Provide the specifics of an experimental research program aimed at reducing damage Define the scope of the numerical analysis project

Historical Performance of Wood-Framed Structures Under Seismic Loads Properly designed and constructed structures perform “adequately” Significant secondary damage to structures following an earthquake Catastrophic failures in non-engineered or poorly constructed structures

Performance of Wood-frame Structures in the Northridge Earthquake, January 17, deaths Collapse of Hillside and Tuck-Under Parking $40 billion loss (primarily due to secondary damage)

Northridge Ground Motion

Ground Damage

Structural vs. Nonstructural Damage Structural Systems –Beams –Columns –Slabs –Steel, Concrete, Masonry, Wood What is nonstructural damage?

Nonstructural Damage All damage that is not structural Secondary damage More costly than structural damage Includes nonphysical damage

Window Frames

Elevator and Door Frames

Collapse

Cripple Walls

Typical Wood Shear Wall

Wood-frame Shear Walls

Wall Openings

Anchor Bolts Quantity and Location Splitting of Bottom Plate Splitting of Posts Construction/Installation Errors

Anchor Bolts

Nonstructural Damage

Problems in Wood Structures Cripple Walls Shear Walls Wall Openings Anchor Bolts Nonstructural Damage How do we improve these trouble areas?

Northridge Fallout City of Los Angeles Inspections Code Changes (after every EQ) Research - $6.9 million from FEMA to CUREe (California Universities for Research in Earthquake Engineering) Innovative Systems

Improvements Strong Walls Anchor Bolts Add Strength

Objective of the Experimental Research Program Investigate and evaluate methods for increasing the energy dissipation capacity of wood-framed shear walls using viscoelastic dampers.

Viscoelastic Dampers Viscoelastic dampers manufactured by 3M Prevalent in Steel and Concrete Structures *Never been applied to wood-frame structures

Damping Schemes Corner Sheathing-to-stud Diagonal X-brace

VE Dampers Applied to Wood Walls

Dynamic Test Setup Wood Shear Wall Hydraulic Actuator applying the “EQ”

Experimental Investigation Full-scale testing of conventional wood shear walls (no dampers) Full-scale testing of wood shear walls with viscoelastic dampers Compare structural properties of both

Dynamic Test Procedure

Typical Results

Calculation of K E and E D KEKE EDED

Numerical Analysis Project The data for two individual hysteresis loops is on the website. –1 set for a conventional wall –1 set for a diagonally damped wall Calculate the energy dissipation for each wall Determine whether or not using VE dampers as a means for increasing the energy dissipation capacity of wood-frame shear walls is feasible.

Final Project Executive Summary Problem Description Detailed Solution Methodology Results Conclusions Project Due at the beginning of class on Monday December 11th