Seismic fragility of concrete building in Malaysia considering the effects of inadequate lap splice length

Abstract

The tremors due to Sumatra earthquake have been reported recently with low to moderate seismic activity level, which have been causing fear to people who are in Peninsula Malaysia. Those, that the new structure should be built or partially built with retrofitting of the existing structure, are the major questions to design globe, which lead essential seismic hazard assessment is necessary to ground motion scenarios due to potential earthquakes. A gap in the previous studies was identified that the inadequate lap splice length in column may give higher probability of exceedance in the seismic design. Accordingly, the seismic fragility curve development is useful in contributing further insight to the continuing evolution of low ductile reinforced concrete frame subjected to far field ground motions with studying the effects of inadequate lap splice length. Three models such as three-, six- and nine- storeys, in low ductile bare reinforced concrete frames developed through ETABS, were included in this study. In order to develop the adequate lap splice lengths to RC frame in ETABS, the P-M2-M3 hinges were assigned to all joints in column with “controlled” dynamic lap splice lengths under column behaviour while all hinges in beam and columns were developed with the behaviours based on American Society of Civil Engineers, ASCE 41-13, standard of seismic evaluation and retrofit of existing buildings. Subsequently, all RC frame models were subjected to analyses such as static pushover, push over with first mode and push over with dynamic mode, the observation of the plastic hinges formation in terms of the damage levels of IO, LS and CP were predicted, and finally, the maximum storey drifts of each damage level were projected to determine as capacity of RC frame in the development of fragility assessment. In addition, the performance of all models was studied by a series of Incremental Dynamic Collapse Analysis (IDA) by means of incremental of 0.05g until 0.50g, which were subjected to 15 far-field ground motions. Based on maximum storey drifts in each analysis from IDA, the median, standard deviation and standard error corresponding to Peak Ground Acceleration (PGA) value were attained as demand of the fragility assessment. Finally, according to the predicted capacity and demand, the fragility curves were presented to the frames of 3-storey, 6-storey and 9-storey with column behaviour consisted of controlling inadequate development or splicing subjected to far-field earthquake excitations. By providing adequate lap splice lengths in columns, the push over analysis showed that there were no damages in columns near foundation while the columns near foundation showed the damage levels of IO, LS and CP when they do have inadequate lap splice lengths. In capacity assessment by push over analysis, maximum storey drifts in all cases were increased by providing adequate lap splice lengths, which this trend brought to be stated that the columns were improved in strength to bear horizontal loads against horizontal displacement. Also, based on the observation of plastic hinge formations at all levels, the damage levels were postponed by providing adequate lap splice lengths to columns and this is a very convenient representation to avoid column failure and postpone the damaged states. Based on the predicted maximum storey drifts from IDA, the storey drifts were lower in all cases due to providing adequate lap splice lengths to columns, which this study brought that the parameter of inadequate lap splice length will be super imposition parameter in controlling the drifts and avoiding structural damages. Developed fragility curves can be a statistical tool in representing the probability of exceeding against PGA and for estimating a specific damage measure in design practice.