Transcript IMI NEES PRESENTATION APRIL 2009rev.ppt

Performance-Based
Design of Masonry and
Masonry
Veneer: A NSF and
Industry ProjectSeismic Performance of
Masonry Veneer
Louisville Trowel Trades Exposition
Presentation
•Who we are
•Discuss the purpose of the
investigation
•Describe the testing program
•Briefly describe the test
results
•Discuss our preliminary
findings
Who we are

University of Texas at Austin
• Richard E. Klingner

University of California at San Diego
• Benson Shing

Washington State University
• Char Grimes , Katherine Keane , David McLean

U of L - NCAT
• Mark McGinley – Sameer Hamoush

Help from masonry industry
Purpose of Investigation
•Seismic performance of masonry
veneer has caused concern and
prompted investigation by the
National Science Foundation and
the Masonry Industry
•The NEES project is attempting
to quantify the seismic behavior
of Masonry veneer systems with
wood or masonry backing walls
Basic concepts

backing system of
wooden studs or
reinforced
concrete masonry

clay masonry
veneer , attached
to backing system
using connectors ,
to improve
esthetics , water penetration
resistance,
durability, etc
Connectors

for wood studs ,
corrugated ties ( nails )
or rigid ties ( screws )

In high seismic areas
require joint reinforcing
in veneer

for concrete masonry ,
adjustable ties or tri wire joint
reinforcement
Seismic behavior of low - rise
buildings with clay masonry veneer
roof diaphragm
walls oriented perpendicular
to ground motion respond
out - of - plane to movements
of slab and roof diaphragm
EARTHQUAKE
walls oriented
parallel to
ground motion
act as shear
walls
response of walls oriented parallel
to ground motion . . .

walls oriented parallel to ground motion
respond as shear walls
• for low aspect ratios ( ratio of height to plan
length less than about 1 ) , behavior is
generally dominated by shear , and walls are
designed to be strong enough to remain elastic
• for higher aspect ratios , behavior is generally
dominated by flexure , and walls can be
designed for ductile behavior
. . . response of walls oriented parallel
to ground motion

veneer and backup system have different
vibration characteristics , so in - plane
seismic response produces forces in
connectors

connectors can fail in shear by low - cycle
fatigue or pullout
response of walls oriented
perpendicular to ground motion . . .
roof diaphragm
a(t)
roof response
time
vertical
strip
loaded out
- of - plane
a(t)
ground motion
time
floor slab
. . . response of walls oriented
perpendicular to ground motion

walls oriented perpendicular to ground
motion respond essentially as vertical
strips , simply supported at floor and roof
diaphragms

veneer and backup system have different
vibration characteristics , so out - of - plane
seismic response produces axial forces in
connectors

connectors can fail in tension by low cycle fatigue or pullout
Work plan -- experimental , analytical
and educational

develop performance criteria for masonry
veneer and veneer connectors
• behavior of connectors under cyclic loads
• in - plane and out - of - plane behavior of veneer
on wood studs and on concrete masonry walls
• behavior of residential and commercial buildings

educate the profession and the public

improve design procedures and code
provisions
Experimental work . . .

quasi - static tests on connectors ( UT
Austin )

quasi - static tests on veneer over wood
studs ( NC A&T and U of L )

quasi - static tests on veneer over
concrete masonry ( UT Austin )

shaking - table tests of small specimens
( UCSD )

shaking - table tests of large specimens
( UCSD )
. . . Experimental work

quasi - static tests
on connectors

quasi - static tests
on veneer over
wood studs and
over concrete
masonry

shaking - table tests
of small specimens

shaking - table tests
of large specimens
middle 2007 ,
middle 2008
in - plane and
out - of - plane
loads
. . . Experimental work

quasi - static tests
on connectors

quasi - static tests
on veneer over
wood studs and
over concrete
masonry

shaking - table tests
of small specimens

shaking - table tests
of large specimens
late 2007
in - plane and
out - of - plane
shaking
. . . Experimental work

quasi - static tests
on connectors

quasi - static tests
on veneer over
wood studs and
over concrete
masonry

shaking - table tests
of small specimens

shaking - table tests
of large specimens
late 2008 ,
early 2009
shaking
. . . Analytical work

develop hysteretic
models for
connectors

develop static and
dynamic models for
veneer , concrete
masonry and wood
studs

calibrate models
using quasi - static
and shake - table
results
started
Fall 2007
. . . Analytical work

develop hysteretic
models for
connectors

develop static and
dynamic models for
veneer , concrete
masonry and wood
studs

calibrate models
using quasi - static
and shake - table
results
started
middle 2008
Educational outreach
started
Summer 2007

K - 12 outreach

summer institutes at WSU and elsewhere
for K - 12 Hispanic and Native American
students

teaching modules on earthquakes ,
masonry and earthquake preparedness

professional outreach
Implementation plan . . .



develop guidelines for
in - and out - of - plane
design of masonry
veneer
refine current MSJC
provisions for design
and detailing of new
masonry and masonry
veneer
include displacement based design of new
masonry in MSJC
starts
Fall 2008
contribution of
veneer to in - plane
stiffness and
strength of wood stud and masonry
backing systems
design of veneer
and connectors for
out - of - plane
forces
. . . Implementation plan

develop guidelines for
in - and out - of - plane
design of masonry
veneer

refine current MSJC
provisions for design
and detailing of new
masonry and masonry
veneer

include displacement based design of new
masonry in MSJC
starts
Fall 2008
Quasi-Static Wood Test
Program
•A total of 8 full sized walls were
built. 4’x8’ and 8’x8’ (with opening)
•4 tested out-of-plane and 4 inplane
•Specimen configurations are what
is the code now and variations on
these.
Test Program
8 LVDT.s connected to
the veneer and backing
wall;
The load was cycled
from 250 lb, increasing
to 500 lb then
increasing in increments
of 500 lb until the
specimen failed.
If max. load reached
before specimen failed
-deflection control was
used.
Test Program
ANCHOR AND
REINFORCEMENT
SPECIMEN
DESCRIPTION
22 gauge corrugated tie (Type A) at 16 in. each way. This
satisfies current requirements for SDC D. 2” Cavity. 8d
nail.
22 gauge corrugated tie (Type B) at 16 in. each way with
joint reinforcement, mechanically attached. 2” Cavity
.This satisfies current requirements for SDC E. 8d nail
Rigid 16 gauge, at 16 in. horizontally and 24 in.
vertically with joint reinforcement (SDC E). This
represents a current West Coast solution. #10 Screw at
bend. 1 in. Cavity
22 gauge corrugated tie (Type A) at 16 in. horizontally
and 8 in. vertically. This represents an upgraded eastcoast solution. 8d nail, 2” cavity.
LOADING
Quasi-static
Wall #
Label
Wall 1
NCAT
Wood 5
Wall 2
NCAT
Wood 6
Wall 3
NCAT
Wood 8
Wall 4
NCAT
Wood 7
Test Results – Typical Behavior
•Typically top of wall deflected more than the
mid-height until the veneer cracked – most
cases.
•At a total load ~ 1000 to 2000 lb a bed joint
near mid-height cracked
Crack in
Bed Joint
Out-ofPlane Wall 1
Bed Joint
Crack
Test Results – Typical Behavior
•After
cracking,
some ties
(22 ga. S.
corrugated)
fatigue
cracked, and
started to
pull out the
nails.
(Wall 1)
Tie
Fractured
Test Results – Typical Behavior
•Failure
was due to
nail both
pullout and
facture –
22 ga. Ties
– Wall 1
Test Results – Typical Behavior
•Failure
was due to
primarily
nail pullout
fractured
ties (less
cracked)Wall2 22
ga. Ties
not
serpentine
Test Results – Typical Behavior
•Tie Failure
but nail
pullout and
fewer
fractured
ties – Wall
4 - 22 ga.
Ties not
serpentine
• at about
80 psf
Test Results – Typical Behavior
•For 16ga
ties (screws)
with Joint
rein. Ties
pulled out of
veneer at
failure and
top section
cracked off
(Wall 3)
~80psf
Wood Quasi-Static In-Plane
Tests
Wood Quasi-Static In-Plane
Tests
Cracking
in veneer
and
sheathing
failures
CMU Quasi-Static O-O-P &
In-Plane Tests – U of T
Testing of in- and out-of-plane wall
segments on outdoor shaking table at the
University of California at San Diego,
September 2007
GROUND MOTIONS
1994 NORTHRIDGE EARTHQUAKE - CALIFORNIA
Sylmar
Tarzana
1.5
2.5
2
1.5
Acceleration (g)
Acceleration (g)
1
0.5
0
-0.5
1
0.5
0
-0.5
-1
-1.5
-2
-1
-2.5
0
5
10
15
20
25
Time (sec)
Sylmar - 6 Story County Hospital
0
5
10
15
20
Time (sec)
Tarzana – Cedar Hill Nursery
25
RESPONSE SPECTRUM
6
Sylmar
Tarzana
Spectral Acceleration (g)
5
IBC - SDC E
80% Sylmar
4
36% Tarzana
Natural Period
3
5% Damping
2
1
0
0
1
2
3
4
Period (sec)
Earthquake Level
% Sylmar % Tarzana
Design Earthquake
(10% in 50 Years)
(476 Years Return Period)
80 %
Maximum Considered Earthquake
(2% in 50 Years)
(2500 Years Return Period)
120%
36 %
X 1.5
54%
OUT-OF-PLANE BEHAVIOR
Nail Pullout
OUT-OF-PLANE BEHAVIOR
Nail Pullout
OUT-OF-PLANE BEHAVIOR
Connector Deformation after Collapse
OUT-OF-PLANE BEHAVIOR
Peak Backing Acceleration (g)
5
4
MCE
Design Level
6
Wood 5
3
Wood 6
Wood 7
2
Wood 7X
Wood 8
Wood 9
1
Wood 10
0
0.0
0.5
1.0
1.5
2.0
Peak Ground Acceleration (g)
2.5
3.0
IN-PLANE BEHAVIOR
 Rocking
4
h4
 Rocking
 Sliding
4
h4
4
100
Veneer Drift (%) 
h4
 Sliding
IN-PLANE BEHAVIOR
Peak Veneer Acceleration (g)
6
5
4
MCE
3
Wood 1
2
Wood
1
Wood 2
Wood
3
1
Wood 3
Wood 4
Wood 2
Wood 4
0
0.0
0.5
1.0
1.5
2.0
Drift (%)
2.5
3.0
3.5
IN-PLANE BEHAVIOR
5
4
MCE
Design Level
Peak Veneer Acceleration (g)
6
3
Wood 1
2
Wood 2
Wood
1
1
Wood 3
Wood
3
Wood 2
Wood 4
Wood 4
0
0.0
0.5
1.0
1.5
2.0
Peak Ground Acceleration (g)
2.5
3.0
3.5
Important Findings from small
tests- dynamic & quasi static
out - of - plane behavior
•veneer cracks at horizontal joints
early in response , but this does not
mean failure
•veneer over concrete masonry fails
at horizontal joint cracks under high
loads
•veneer over wood fails by failure of
nails or screws
•some corrugated ties fail in low cycle fatigue
Important Findings from small
tests- dynamic & quasi static
in - plane behavior
•veneer slides and rock
•different response of veneer
and backing system imposes end
displacements on connector
•response of connectors to this
history is governed by low cycle fatigue
Important Findings from small
tests- dynamic & quasi static
Performance objectives for
veneer
•veneer should not fall off
under design earthquake
(500 years ) and even under
maximum considered
earthquake ( MCE -- 2,500
years )
Important Findings from small
tests- dynamic & quasi static
• design objectives are met for veneer over
concrete masonry backing
– specimens resisted peak ground accelerations
of 2.87 g ( more than 2.5 times maximum
considered earthquake )
• design objectives are probably met for
veneer over wood - stud backing
– specimens have resisted peak ground
accelerations of at least 2.0 g ( more than
2 times maximum considered earthquake )
– possible issues with nail pullout and low cycle fatigue of some corrugated
connectors
Large Scale Tests

January 2009 tested
wood backed system

March 29 and 30th
tested CMU backed
system
Wood Walled Specimen Construction
Wood Walled
Specimen Test
2009-01-23
0.21 g
0.25 Sylmar. The specimen was subjected to 0.25 times the
Sylmar record (the record from the Sylmar recording station)
-1994 Northridge earthquake, which had a magnitude of 6.7.
about a magnitude 6.1 earthquake. This produced no sliding
and no visible damage.
2009-01-23
0.42 g
0.50 Sylmar. This was equivalent to about a magnitude 6.4
earthquake.
This produced no sliding and no visible
damage.
Design EQ
0.67g
0.80 Sylmar (equivalent to magnitude 6.6 earthquake). This is
ASCE7-05 design earthquake for Seismic Design Category
D. It has a 10% probability of exceedance in 50 years (476year return period).Top of veneer “Plan south side” of the
structure (corrugated ties, movement joints) peeled, due to
extraction of the nails from the wood frame. This was not
what we anticipated. MOISTURE!
Wood Walled
Specimen Test
Maximum
Considered
Earthquake
1.01g
1.20 Sylmar (~ 6.8 earthquake). ASCE7-05 maximum considered
earthquake for SDC D. (2% probability of exceedance in 50 years
(2500-year return period). Lots of deflection. Remaining veneer on
the plan south side of the structure came off, again by extraction of
the nails from the wood frame. The rest of the structure was
essentially undamaged.
1.26g
1.50 Sylmar (equivalent to about a magnitude 6.9 earthquake). Roof
displacements of more than ***6 inches. The remaining veneer was
essentially undamaged. It visibly responded out-of-plane.
1.68g
First 2.0 Sylmar (~7.0 earthquake). Most of the veneer at the top of
the plan north side came off by breaking of the bed joints at the level
of the connectors (Figure 3). Pier rocking was noticeable to the plan
north of the door on the plan east side. (Figure 4).
1.68g
Second 2.0 Sylmar (~ 7.0 earthquake). The rest of the veneer at the
top of the plan north side came off , accompanied by breaking of the
bed joints at the level of the connectors and by failure of the
connection to the veneer. The veneer on the plan east side fell off, due
to extraction of nails from the studs. The veneer on the plan west side
was very close to coming off, and slid several inches. Nail extraction
was evident.
CMU Walled Specimen Construction
CMU Walled
Specimen Test
PGA
Comments
0.17g
0.20 Sylmar. (~ magnitude 6 earthquake.) It produced no sliding or
visible damage.
0.34 g
0.40 Sylmar. This is equivalent to about a magnitude 6.5 earthquake.
It produced no sliding or visible damage.
0.67g
(Design EQ)
0.80 Sylmar (~6.6 earthquake). Design earthquake for SDC D. It has a
10% probability of exceedance in 50 years (476-year return period). It
produced no sliding or visible damage.
1.01g
1.20 Sylmar (~ 6.8 earthquake- 2% probability of exceedance in 50
(Maximum years -2500-year return period). It produced no visible damage. The
Considered in-plane veneer began to slide a little.
Earthquake)
1.68 g
2.00 Sylmar (~ 7 earthquake). This produced hairline cracking at the
bases of the CMU walls in- and out-of-plane.
CMU Walled
Specimen Test
PGA
Comments
1.79 g
1.00 Tarzana. We changed motions so as not to exceed the
capacity of the table. We saw rocking of the in-plane CMU walls
(short wall segments, and sliding of the long CMU wall segments.
2.69 g
1.50 Tarzana. We saw more rocking and sliding of the CMU walls
in-plane. The veneer on the compass east side slammed against
the CMU on the east side, fracturing the veneer at the compass
northeast corner and starting cracking of veneer at the southeast
corner. The veneer cracked on the compass east side.
2.69 g
1.50 Tarzana again. The specimen slid more than 6 in. The
veneer was badly damaged at the compass northeast and
southeast corners, and on the compass east side. The CMU walls
were badly damaged on the east side.
Summary
Wood Specimens
1) Low-rise wood-stud and masonry veneer
(2006 IRC requirements for SDC D2) can resist
earthquakes above MCE without collapse.
2) These buildings generally performed as
expected, but note:
- Masonry O-O-P is just mass but in-plane it
stiffens the building and shares load.
- Connectors are critical –the pullout of nails in
the building test at levels of shaking less than
DBE is concerning. Nails are effected by
moisture (up to 70% reduction) – Screws or ring
shank nails needed.
-Joint reinforcing does not help.
Summary
CMU Specimens
1) Low-rise reinforced CMU back-up and clay
masonry veneer structures (2008 MSJC Code and
Specification for SDC D) can resist earthquakes
above MCE without collapse.
2) The seismic response was generally consistent
with performance expectations and:
-Veneer meeting 2008 MSJC Code and
Specification, experienced only minor cracking and
stayed fully connected to the CMU walls, up to
1.75 MCE.
-In plane veneer not just mass
Summary
CMU Specimens
-Connectors behaved well, implying that current
MSJC requirements for veneer connectors are OK
-No effect for joint reinforcement.
-Vertical control joints in the CMU at the lintels
delayed the onset of damage to the CMU walls
past MCE.
-Vertical expansion joints in the veneer at the
ends of the lintels permitted the underlying
masonry to rock without damage to the veneer
above the lintels.
-Vertical expansion joints in the veneer at the
corners prevented damage there from movement
of the in-plane walls.
Acknowledgements
This investigation was conducted
under funding from a Nation
Science Foundation – NEES
Small Group Grant.
Funding was also provided by the
Council for Masonry Research,
BIA and NCMA.
The conclusions and opinions
expressed are solely those of
the researchers