The response of precast concrete segmental columns subjected to near base impact

Precast concrete segmental column has attracted many attentions for the past decades due to its unique features especially in improving the construction quality and efficiency. However, the performance of precast segmental column under lateral impact loading has been less studied. Our previous studies performed laboratory pendulum impact tests on scaled segmental columns to investigate their behaviours when impacted at mid-span of the column. This article studies the response of segmental column when impacted near the column base, which generates different response modes and failure mechanisms compared to the columns subjected to the mid-span impact. Lateral impacts are applied either to segmental joint between the two bottom segments or directly onto the centre of the base concrete segment. A detailed three-dimensional numerical model is created and validated with laboratory impact testing results on scaled segmental columns. A full-scale 3-m tall segmental column is then numerically built to study the behaviour under near base impact. The column damage and failure modes are analysed. The influences of prestress level in the post-tensioning tendon and concrete strength on the performance of segmental column subjected to near base impacts are investigated through numerical simulations.

The effect of concrete shear key on the performance of segmental columns subjected to impact loading

Conventional precast segmental columns with seismic resistance design consist of only flat concrete segments with prestress tendon. This is because friction between adjacent segments is sufficient to resist the lateral forces from earthquake-induced actions. However, the friction between segments is not necessarily sufficient to resist lateral impact loads such as vehicle impact the column might experience during its service life. This article investigates the effectiveness of using concrete shear key in segments of precast segmental column in resisting the lateral impact loading. The precast reinforced concrete segments were designed with concrete shear keys to improve the column shear resistance capacity and minimize the relative displacement between adjacent segments. Two groups of segmental columns with and without shear key were designed and tested using a pendulum impact system. The effectiveness of shear key in resisting lateral impact loads was analysed by comparing the performance of the two groups of segmental columns. The testing results revealed that by introducing concrete shear key to segmental column, the relative displacement between adjacent segments could be effectively reduced. However, the large concrete shear key increased stress concentration in the concrete segments. Relatively, more severe damages to concrete segments were found on the columns with shear key. Further improvements on shear key designs should be made for better performance of segmental columns against impact loading.