Pudjisuryadi, Pamuda (2011) IN-ELASTIC PERFORMANCE OF 2D-TWO BAY ORDINARY CONCENTRICALLY BRACED STEEL FRAME. In: The 2nd International Conference on Earthquake Engineering and Disaster Mitigation, 19-07-2011 - 20-07-2011, Surabaya - Indonesia.
Abstract
In this study, in-elastic performance of 2D-two bay ordinary concentrically braced steel framed is observed. The steel structure has equally 6m bays, and five stories with uniform 4m floor to floor height. It is assumed as a part of common office building resting on soft soil of Zone 6 in Indonesian Seismic Map (SNI 03-1726-2002). The seismic reduction factor, R is taken as much as 3.0. All braces are assumed to reach their capacity during severe earthquake event. The steel grade used for whole structure is kept the same in order to stimulate the commonly available steel used in Indonesian construction industry (fy=240 MPa, f¬u=370 MPa). Steel design is carried out by using Indonesian Steel Structure Code (SNI 03-1729-2002), while the in-elastic performance is evaluated by non-linear static pushover analysis. The non-linear hinge properties are adopted from Table 5 of FEMA 356 which and generated automatically inside SAP2000 software package. Design result of the particular chosen geometry size, shows that the braces are controlled dominantly by slenderness ratio limitation. To satisfy the limitation criteria, the maximum axial stress ratio of the braces is still as low as 0.389. Beams and columns, which have to remain elastic while subjected to axial resistance capacity of the braces, have higher reserve capacity. Observed in-elastic behavior by non-linear static pushover shows that the structure still remains in elastic range due to design earthquake (500 years return period). However, with increasing demand spectra, it is observed that plastic hinges start to develop in the lower story of compression braces and propagate to higher story. It is concluded that the code provision succeeds to isolate the damage in braces. However, slenderness ratio limitation of braces specified by the code, if not accompanied by appropriate selection of steel grade (i.e. using lower steel grade), can result in over-conservative design.
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