An accurate quantification of the displacement capacity of a reinforced masonry shear-wall system is of critical importance to seismic design because it has a direct implication on the seismic force modification factor, which is the R factor in ASCE 7. In spite of the shear capacity design requirement in TMS 402, special reinforced masonry walls within a building system could still develop shear-dominated behavior, which is perceived to be far more brittle than flexural behavior. These walls have a low shear-span ratio either because of the wall geometry (i.e., a low height-to-length ratio) or the coupling forces introduced by the horizontal diaphragms, which are often ignored in design. Although shear-dominated walls appeared to be very brittle in quasi-static tests conducted on single planar wall segments, reinforced masonry structures survived major ground shaking well in past earthquakes. This could be partly attributed to the beneficial influence of wall flanges as well as the over-strength of the system. Flanged walls are common in masonry buildings, but their behavior is not well understood because of the lack of laboratory test data. Furthermore, other walls or columns that are present in the structural system to carry gravity loads could enhance the lateral resistance of the shear walls and the displacement capacity of the system by providing axial restraints as well as alternative load paths for gravity loads. A research project is being carried out with shake-table tests to investigate the displacement capacity of shear-dominated reinforced masonry wall systems. This paper presents results of the first shake-table test conducted in this project on a full-scale single-story
coupled T-wall system. The structure was tested to a drift ratio exceeding 15% without collapse.
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Evaluation of collapse resistance of reinforced masonry wall systems by shake‐table tests
This paper presents a shake‐table test study to investigate the displacement capacity of shear‐dominated reinforced masonry wall systems and the influence of wall flanges and planar walls perpendicular to the direction of shaking (out‐of‐plane walls) on the seismic performance of a wall system. Two full‐scale, single‐story, fully grouted, reinforced masonry wall specimens were tested to the verge of collapse. Each specimen had two T‐walls as the seismic force‐resisting elements and a stiff roof diaphragm. The second specimen had six additional planar walls perpendicular to the direction of shaking. The two specimens reached maximum roof drift ratios of 17% and 13%, without collapsing. The high displacement capacities can be largely attributed to the presence of wall flanges and, for the second specimen, also the out‐of‐plane walls, which provided an alternative load path to carry the gravity load when the webs of the T‐walls had been severely damaged. The second specimen developed a higher lateral resistance than the first owing to the additional axial compression exerted on the T‐walls by the out‐of‐plane walls when the former rocked. The shear resistance of the T‐walls evaluated with the design code formula matches the test result well when this additional axial compression is taken into account. However, it must be understood that the beneficial influence of the wall flanges depends on the magnitude of the gravity load because of the P‐Δ effect and the severity of damage induced in the wall flanges when the wall system is subjected to bidirectional ground motions.
more » « less- Award ID(s):
- 1728685
- NSF-PAR ID:
- 10454724
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Earthquake Engineering & Structural Dynamics
- Volume:
- 50
- Issue:
- 2
- ISSN:
- 0098-8847
- Page Range / eLocation ID:
- p. 475-494
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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An accurate quantification of the displacement capacity of a reinforced masonry shear-wall system is of critical importance to seismic design because it has a direct implication on the seismic force modification factor, which is the R factor in ASCE 7. In spite of the shear capacity design requirement in TMS 402, special reinforced masonry walls within a building system could still develop shear-dominated behavior, which is perceived to be far more brittle than flexural behavior. These walls have a low shear-span ratio either because of the wall geometry (i.e., a low height-to-length ratio) or the coupling forces introduced by the horizontal diaphragms, which are often ignored in design. Although shear-dominated walls appeared to be very brittle in quasi-static tests conducted on single planar wall segments, reinforced masonry structures survived major ground shaking well in past earthquakes. This could be partly attributed to the beneficial influence of wall flanges as well as the over-strength of the system. Flanged walls are common in masonry buildings, but their behavior is not well understood because of the lack of laboratory test data. Furthermore, other walls or columns that are present in the structural system to carry gravity loads could enhance the lateral resistance of the shear walls and the displacement capacity of the system by providing axial restraints as well as alternative load paths for gravity loads. A research project is being carried out with shake-table tests to investigate the displacement capacity of shear-dominated reinforced masonry wall systems. This paper presents results of the first shake-table test conducted in this project on a full-scale single-story coupled T-wall system. The structure was tested to a drift ratio exceeding 15% without collapse.more » « less
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