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SUMMARYThis paper proposes a new analytical model for masonry-infilled R/C frames to evaluate the seismic performance considering R/C frame-infill interactions. The proposed analytical model replaces masonry infill with a diagonal compression strut, which represents distributed compression transferred between frame and infill interfaces. The equivalent strut width is presented as a function of the frame-infill contact length, which can be evaluated by static equilibriums related to compression balance and lateral displacement compatibility at the frame-infill interfaces. The proposed analytical model was verified through comparisons with experimental results obtained for several brick masonry-infilled R/C frames representing a typical R/C building with nonstructural masonry infill in Indonesia. As a result, good agreements were observed between the experimental and analytical values of the lateral strength and ductility of the infilled frames. The seismic performances of two earthquake-damaged R/C buildings with different damage conditions were evaluated considering infill effects by applying the proposed analytical model. Consequently, the nonstructural brick masonry infill significantly affected the seismic resistances of the buildings, which seemed to lead to differing levels of damage for each building. These results indicate that the proposed analytical model can be an effective tool for more precisely screening earthquake-vulnerable existing R/C buildings in Indonesia.

SUMMARYNumerous non-ductile reinforced concrete (RC) buildings with little or no shear reinforcement in beam-column joints can be found in regions of moderate seismicity. To strengthen such substandard beam-column joints, this study proposes a method in which RC wing walls are installed beside existing columns, which overcomes the lack of realistic strengthening methods for congested connections in RC buildings. The proposed strengthening mechanism improves the joint moment capacity by utilizing tension and compression acting on the beam-wing wall boundaries; thus, brittle joint hinging failure is prevented. Three 3/4-scale RC exterior beam-column joint specimens without shear reinforcement, two of which were strengthened by installing wing walls with different strengthening elements, were fabricated and tested. The test results verified the effectiveness of the proposed strengthening method and the applicability of this method to seismically substandard beam-column joints.

Earthquakes occurring on September 12 (8.4 M L ) and 13 (7.9 M L ), 2007, in South and West Sumatra, Indonesia, respectively, damaged many buildings. This paper reports investigation results on damaged buildings in and around Padang, West Sumatra, and discusses the seismic performance of two reinforced concrete (RC) frame structures with unreinforced masonry (URM) brick walls.Observations revealed that several RC structures with URM walls suffered severe damage such as shear failure of columns, buckling of column longitudinal reinforcements, and collapse of brick walls. In confined and simple URM structures, damage mainly to brick walls was observed. On the contrary, timber structures performed relatively well during the earthquakes.Two calculations were performed-one with and one without infill walls, focusing on two three-story collapsed and surviving RC buildings in Padang. A distinct difference was identified between the seismic performance of the two buildings when considering infill walls. Therefore, these samples of earthquakedamaged buildings verify that nonstructural infill walls can significantly contribute to the seismic performance of this type of structure.

This paper describes the effects of nonstructural brick walls on the seismic performance of reinforced concrete (R/C) buildings. Experimental and analytical studies were conducted on two buildings: one of which collapsed and the other suffered moderate damage due to the 2007 Sumatra, Indonesia earthquakes. A brick wall was extracted from the moderately damaged building and transported to Japan from Indonesia to experimentally evaluate its seismic performance. Two R/C one-bay frame specimens were constructed, and the imported wall was installed in one of the specimens. Comparing the seismic performance of specimens with and without the brick wall through quasi-static cyclic loading tests, wall contributions were quantitatively evaluated. Moreover, the seismic performance of the earthquake-damaged Indonesian buildings was evaluated numerically considering the findings of the tests. The analyses revealed a possible reason for the collapse of one of the buildings due to the earthquakes.

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This study aims at improving a strength reduction factor r 3 related to opening height for RC shear walls in the AIJ design standard. FEM analyses for RC shear wall specimens with vertically aligned openings were conducted to evaluate contributions of the wall components to the overall lateral strengths. As a result, the flexural resistances of the partial walls divided by the openings were overestimated by r 3 , while the shear resistances of the beams between the openings agreed with those by r 3 . Therefore, a new strength reduction factor new r 3 was proposed on the basis of a flexural strength reduction index for this type of wall. Consequently, the estimations for the ultimate strengths of the above specimens using new r 3 showed good agreements with the experimental strength reductions.