Dynamic response of slender/thin reinforced precast concrete walls using shaking table

Abstract

Two geometrically identical three-eight full scale of thin/slender precast wall panels constructed with different base block connections are tested under several earthquake excitations using shaking table. Specimen 1 is designed with a high longitudinal reinforcement ratio with a fixed-base conventional monolithic connection. Specimen 2 is designed with one-half of longitudinal reinforcement ratio Specimen 1 with a rocking-base connection. Both of the walls are designed to carry gravity loading of 34kN and a 50kN supplementary inertia mass is seated on a separate frame at a pin-based connection to represent the initial impulse from earthquake. A shaking table is used to imitate the selected past earthquake records. Specimen 1 is tested under the Taft earthquake excitation with Peak Ground Acceleration (PGA)=0.2g, El Centro (PGA=0.4g) and Kobe (PGA=0.8g), while Specimen 2 undergoes Taft (PGA=0.2g) and El Centro (PGA=0.4g). The dynamic response of Specimen 1 is significantly influenced by its tendency towards permanent out-of-plane deformation. The experimental result shows that Specimen 1 collapsed with a maximum in-plane displacement of 90mm at 5.2 second. Specimen 2 experienced horizontal cracks at bottom one third of the wall. The surface cracks became wider during 0.4g PGA El Centro motion and a large ductility demanded was localised over a very short plastic hinge zone (PHZ). The specimen gradually collapsed due to tensile fracture of the longitudinal starter bars within the grouted zone. This research demonstrates that thin/slender precast wall panel with an excessive longitudinal reinforcement bars is not stable with height to thickness ratio of 60:1 subjected to strong ground shaking. A high ratio of longitudinal reinforcement in walls can generate large in-plane diagonal compressive strut leading to out-ofplane buckling behaviour.