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

CEE 3702 - 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, 1994

• 19 deaths

• Collapse of Hillside and Tuck-Under Parking

• $40 billion loss (primarily due to secondary damage)

Northridge Ground Motion

Ground Damage

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

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

Displacement (in)

-3 -2 -1 0 1 2 3

Loa

d (l

b)

-10000

-8000

-6000

-4000

-2000

0

2000

4000

6000

8000

10000

Typical Results

Calculation of KE and ED

-400

-300

-200

-100

0

100

200

300

400

-0.015 -0.01 -0.005 0 0.005 0.01 0.015

Displacement (in)

Loa

d (l

b)

KE

ED

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