In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear - - PowerPoint PPT Presentation

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

BROOK ROBAZZA1, KEN ELWOOD2, SVETLANA BRZEV3, DON ANDERSON4

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

1brook.robazza@civil.ubc.ca / 2elwood@civil.ubc.ca / 3svetlana_brzev@bcit.ca / 4dla@civil.ubc.ca

August 19 2013

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

INTRODUCTION

• Out-of-plane instability failure mechanism first documented by

Paulay and Priestley

• Investigate CSA S304.1-04 limits on the h/t ratio

height/thickness ratio

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

CSA S304.1-04 HEIGHT-TO-THICKNESS RATIO LIMITATIONS

Wall height-to-thickness ratio restrictions: Rd h / t.

• Limited ductility shear walls

1.5 18

• Moderately ductile shear walls

2.0 14

• Moderately ductile squat shear walls

2.0 20 Note: Post-disaster buildings need Moderately Ductile Walls (Rd = 2.0) regardless of seismic risk!

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

OUT-OF-PLANE INSTABILITY FAILURE MECHANISM

Phase 1: Uniaxial loading of reinforced masonry columns

A B

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

RESEARCH OBJECTIVES

1. Establish rational criteria for out-of-plane stability of reinforced masonry shear walls, 2. Determine safe and economical h/t limits for seismic design, and 3. Prepare recommendations for mitigation techniques and future masonry design standards. Phase 2: In-plane loading of reinforced masonry shear walls undergoing large plastic rotations

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

WALL SPECIMENS W1 AND W2 - DETAILS

Thickness, t = 140 mm Height, h = 3800 mm Length, L = 2600 mm h/t ratio = 27.1 h/L = 1.5 v = 0.33% h = 0.36% f’m = 53 MPa

42

15M 10M 15M

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

TEST SETUP REQUIREMENTS

1. W1 test – simulated bottom storey of a multi-storey structure with two inclined vertical actuators to simulate overturning moment 2. W2 test – simulated a wall in a single-storey structure

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

SPECIMEN W1 - LOADING PROTOCOL

Displacement-controlled loading protocol based on yield strain in end reinforcing bars with constant axial load of 660 kN (0.034f’m)

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

SPECIMEN W1 TESTING X X X

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

SPECIMEN W1 - AXIAL STRAINS

0.0053 0.0039 0.0026 0.0013

• 0.0013
• 0.0026
• 0.0039
• 0.0053

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

SPECIMEN W1 – KEY FINDINGS

1. Failure mechanism characterized by flexural toe crushing 2. High axial load prevented development of wide flexural cracks 3. High plastic tensile strains developed in vertical reinforcement but were localized at the bottom two courses of the wall

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

SPECIMEN W2 TESTING - OBJECTIVES

1. Remove applied axial stresses to induce wide flexural cracks within the plastic hinge zone 2. Ensure larger plastic tensile strains in vertical reinforcement 3. Be aware of sliding shear…

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

SPECIMEN W2 - LOADING PROTOCOL

Displacement-controlled loading protocol based on same displacement increment as W1 with zero applied axial load

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

W2 TESTING X X X X

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

W2 OUT-OF-PLANE INSTABILITY FAILURE MECHANISM X X X X X X X

WALL THICKNESS / 2 2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

W2 AXIAL STRAINS

0.010 0.009 0.008 0.007 0.006 0.005 0.004 0.003 0.002 0.001

• 0.001
• 0.002
• 0.003
• 0.004

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

W2 TESTING – KEY FINDINGS

1. Out-of-plane instability occurred at high ductility levels ( > 8Δy ) 2. Failure characterized by high plastic strains in vertical reinforcement ( > 5εy averaged over wall height ) and out-of-plane displacements exceeding half the wall thickness 3. Absence of axial load permitted development of wide and uniform flexural cracks in the wall ( > 10.5 mm prior to spalling ) 4. Out-of-plane displacements observed at low ductility levels ( ~2 Δy ) however these displacements subsided after the load reversal

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

SPECIMENS W1 AND W2 - COMPARISON OF HYSTERETIC RESPONSE

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

SPECIMENS W1 AND W2 - COMPARISON OF OUT-OF-PLANE DISPLACEMENTS

WALL THICKNESS / 2 WALL THICKNESS / 2 2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

CONCLUSIONS

1. Out-of-plane instability is a possible failure mechanism in reinforced masonry shear walls 2. Instability occurs when high tensile strains ( > 5εy averaged over wall height ) develop in vertical reinforcement, along with the wide and uniform flexural cracks ( > 10.5 mm prior to spalling ) 3. Axial load has a significant effect on the failure mechanism (large difference in behaviour between 0.034f’m and zero) 4. Out-of-plane displacements can initiate at low ductility ( ~2Δy ) , however instability occurs at high ductility levels ( > 8Δy ) 5. Height-to-thickness ratio alone not sufficient to assess the stability

• f reinforced masonry shear walls

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

Phase 3 of Research Study

1. Further investigate the parameters affecting the stability of slender reinforced masonry shear walls 2. Use these parameters to mitigate against instability in modern and existing reinforced masonry shear walls a. Determine critical axial stress level above which instability generally does not occur b. Explore the effect of better confinement in the important wall toe regions c. Examine reinforcement layouts which may lessen the probability for out-of-plane instability

2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING

In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results

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2013 UBC-Tongji-CSRN Symposium VANCOUVER, BRITISH COLUMBIA