Abstract
Shake table tests were performed on three two-story 1 : 3 reduced scale RC frame structures, representative of buildings with construction deficiencies in Pakistan. The models were subjected to the natural accelerogram of the 1994 Northridge earthquake and tested under multiple scaled excitations until the models attained incipient collapse state. The models’ damage mechanisms were studied, and the seismic response in terms of floor acceleration and floor displacement was retrieved. A uniform damage scale was developed for global performance assessment of considered deficient RC frames, listing average estimate of limit states’ drifts and base shear coefficients, with measured uncertainty, and describing frame damage condition. Numerical frame models were prepared in finite element-based program SeismoStruct and calibrated against experimental tests. The frames were analyzed through incremental dynamic analyses. Seismic fragility functions were derived using a probabilistic-based methodology, which may be used for global damageability assessment of the considered frame building typology. Available building damage-to-loss factors were employed to transform structural damages to repair cost ratio, which were correlated with seismic intensity (repair cost ratio versus seismic intensity) to derive the seismic vulnerability curve, which may be used for the direct economic loss estimation of the considered frame building typology.
Highlights
For the test model frame structures, the displacement and acceleration response were recorded through install instrumentation in the form of linear displacement transducers and accelerometers. e experimental data obtained for each test model were further analyzed to obtain the damage limit state as per the FEMA [16], which can be employed for the seismic performance assessment of the frame structures
Modern existing RC frame building typology in Pakistan is designed to the recent building code of Pakistan and detailed as per the requirements of [15] for special moment-resisting frame structures
Shake table tests performed on representative three low-rise two-story 1 : 3 reduced scale RC frames with construction deficiencies have revealed that such frame building typology exhibits mixed mechanism of column and beam member hinging followed by severe beam-column joint panel damage. is can result in significant vulnerability of the considered frame structures
Summary
(iv) e first-story joint panel regions were extremely damaged and with concrete spalling at the base.(v) After this excitation, the test model was near to the collapse stage. When the frame model reaches to the input excitation of 60%, the test model was found to be lateral at a roof drift value of 3.92% During this input shaking, the test frame experiences significant damages in the structural members (beam and columns) as well as the joint panel regions. It was observed that ground-story level joint panel regions experienced major cracking and with concrete cover spalling and detachments at bottom levels After this run, the test model was near the collapse stage, and the testing program was stopped. It was observed that, as in the case of Model-2, the damage pattern appears to be on much lower shaking demands as compared with the other two models. e experimental observed damage response in test Model has been reported in Table 3 and Figure 6
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