| Summary: | 碩士 === 國立成功大學 === 建築學系碩博士班 === 95 === In Taiwan, confined masonry is commonly used for in-filled walls in low-rise RC buildings. Although the un-reinforced masonry (URM) walls displayed well in-plane strength in the past earthquakes, they are also fragile when subjected to out-of-plane loading.
In order to study the out-of-plane failing behavior of un-reinforced confined masonry walls, a series of single-axis shaking table tests had been taken. Four full-scaled one-story RC frames consist of no wall, half-brick thick pre-laid, half-brick thick post-laid, and one-brick thick pre-laid URM in-filled walls were designed to investigate the effect of thickness and construction methods on the out-of-plane strength. The beams and the slab of specimens were purposely strengthened to provide larger inertial force and confinement to the in-filled walls. A time-history record of Chi-Chi earthquake is chosen to excite the specimen on the out-of-plane direction of walls while the intensity is gradually enhanced each excitation.
For all the URM walls, horizontal cracks occurred at the top and the bottom edges almost as soon as the tests began. Then as the ground motion was increased, the top and bottom cracks extend to the whole width of walls and other horizontal cracks started to show between them. The post-laid walls began to split from the RC frame during the later stages of the loading procedure and eventually collapsed in pieces. Contrarily, the pre-laid walls remained in the frames throughout the entire test.
The test results suggest that increasing thickness of URM walls usually leads to slightly higher stiffness. However, there is no apparent relationship between thickness and out-of-plane strength. Generally, specimens with pre-laid walls show higher strength and stiffness than the one with post-laid wall. All the specimens with URM in-filled walls show higher strength than the one without walls. Therefore, the possible out-of-plane contribution of URM walls is confirmed in this test. Meanwhile, existing assessment equations were used to compare with the test results, but all the equations tends to underestimate the out-of-plane strength of URM walls.
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