Effect of Inadequate Lap Splice Length on the Collapse Probability of Concrete wall Buildings in Malaysia

Background

In recent decades, Malaysia has shown a significant increase in the number of constructed high-rise buildings due to rapid urbanization and an increase in its population. However, due to the country's low seismicity, the majority of such tall buildings and infrastructures have not been designed against seismic actions. Therefore, they do not comply with the required seismic detailing and often suffer from inadequate lap splice length. After the 2015 Sabah earthquake that imposed significant damage to public buildings, the seismic vulnerability of buildings in Malaysia received increasing attention. As a result, researchers have tried to quantify the seismic vulnerability of buildings in Malaysia through the development of fragility curves.

Objectives

In Malaysia, most developed seismic fragility curves for buildings have not taken into account the effect of inadequate lap splice length. Therefore, this study investigates to what extent an inadequate lap splice length can alter the concrete wall buildings’ probability of collapse.

Methods

Two 25-story concrete wall buildings with an identical plan but different parking levels were selected. Fifteen natural far-field earthquake records were used in the incremental dynamic analysis to calculate the inter-story drift demand and capacities. The inelastic response of beams and columns was simulated through the lumped plasticity model, and that of concrete walls and slabs was taken into account through the fiber-based distributed plasticity model. The effect of inadequate lap splice length in columns was simulated in the finite element models using the proposed method in ASCE/SEI 41-17 code. The developed fragility curves were compared with those established by other researchers for the same buildings.

Results

It was observed that seismic-induced damage mostly concentrated on the columns of parking levels while the concrete walls remained in the elastic region. The obtained inter-story drift capacities were all less than 2%. Besides, the inter-story drift capacities of interior frames were less than half of exterior frames. The exterior frame of the building with three parking levels exhibited a larger probability of exceeding the CP limit state than the interior frame. A similar observation was made for the building with five parking levels when the PGA was more than 0.25g. Moreover, the probability of exceeding the CP limit state of the exterior frame with three parking levels was significantly more than that of the exterior frame with five parking levels. A similar observation was made for the interior frames when the PGA was larger than 0.2g. Furthermore, the conducted comparison showed that an inadequate lap splice length could increase the concrete wall buildings’ probability of collapse between 38 to 89%. The increase in the collapse probability of the interior frame with five parking levels was almost twice that of the exterior frame.

Conclusion

It was concluded that the inadequate lap splice length could significantly reduce columns’ rotational capacity and result in brittle failure mode and limited residual strength. Besides, the inadequate lap splice length of columns reduced the inter-story drift capacity of investigated buildings and significantly increased their probability of collapse. Therefore, it was strongly suggested to include the effect of inadequate lap splice length in the finite element models when conducting seismic vulnerability studies.

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