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.

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.

Significant damage to reinforced concrete buildings by the 2009 Western Sumatera Earthquake revealed that deficiencies in design engineering and/or construction practice existed. This indicated that enforcement of building design codes was lacking. The Indonesian government has updated the building design codes which should have been applied in the construction of new buildings. However, enforcement of these codes on design engineering and/or construction practice in Padang city is not clear. In this study, a field investigation was performed to investigate common structural details and deficiencies in newly constructed multi-story reinforced concrete buildings. The investigation was conducted through visiting building construction sites in Padang city area. This study preliminary reports the investigation results on 39 private buildings and 8 government buildings. The common deficiencies found on the investigated buildings were low material quality, small structural dimensions with light longitudinal reinforcement, insufficient transverse reinforcement with poor details, improper location of lap splice of rebar, lack of hoops inside exterior and interior beam-column joints, and deficient anchorage of beam reinforcement to exterior beam-column joints. These investigation results clarify that enforcement of the latest buildings design codes in design engineering and/or construction practice is still lacking in the investigated area.

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