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

UNIVERSITY OF BRITISH COLUMBIA DEPARTMENT OF CIVIL ENGINEERING In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results BROOK ROBAZZA 1 , KEN ELWOOD 2 , SVETLANA BRZEV 3 , DON ANDERSON 4 August 19 2013 1 brook.robazza@civil.ubc.ca / 2 elwood@civil.ubc.ca / 3 svetlana_brzev@bcit.ca / 4 dla@civil.ubc.ca

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA 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 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA 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: R d 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 (R d = 2.0) regardless of seismic risk!

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

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results RESEARCH OBJECTIVES Phase 2: In-plane loading of reinforced masonry shear walls undergoing large plastic rotations 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.

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA 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 15M 10M 15M Length, L = 2600 mm h/t ratio = 27.1 h/L = 1.5  v = 0.33%  h = 0.36% f’ m = 53 MPa 42

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results TEST SETUP REQUIREMENTS W1 test – simulated bottom storey of a multi-storey structure with 1. two inclined vertical actuators to simulate overturning moment W2 test – simulated a wall in a single-storey structure 2.

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

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results SPECIMEN W1 TESTING X X X

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

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

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA 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 Be aware of sliding shear… 3.

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

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results W2 TESTING X X X X

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results W2 OUT-OF-PLANE INSTABILITY FAILURE MECHANISM WALL THICKNESS / 2 X X X X X X X

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA 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 -0.001 -0.002 -0.003 -0.004

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results W2 TESTING – KEY FINDINGS Out-of-plane instability occurred at high ductility levels ( > 8 Δ y ) 1. 2. Failure characterized by high plastic strains in vertical reinforcement ( > 5 ε y 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 ) Out-of-plane displacements observed at low ductility levels ( ~2 Δ y ) 4. however these displacements subsided after the load reversal

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results SPECIMENS W1 AND W2 - COMPARISON OF HYSTERETIC RESPONSE

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

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA 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 Instability occurs when high tensile strains ( > 5 ε y averaged over 2. 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) Out-of-plane displacements can initiate at low ductility ( ~2 Δ y ) , 4. however instability occurs at high ductility levels ( > 8 Δ y ) 5. Height-to-thickness ratio alone not sufficient to assess the stability of reinforced masonry shear walls

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

UNIVERSITY OF BRITISH COLUMBIA 2013 UBC-Tongji-CSRN Symposium DEPARTMENT OF CIVIL ENGINEERING VANCOUVER, BRITISH COLUMBIA In-Plane Seismic Behaviour of Slender Reinforced Masonry Shear Walls: Experimental Results THE END Questions...