Experimental Investigation of Pounding Responses in Base-Isolated Frame Structures at Expansion Gap

Abstract

Experimental simulation and parametric studies have been conducted to investigate the effect of pounding in base-isolated (BI) frame structures with expansion gaps. Earthquakes often result in extensive damage at expansion joints, which encouraged this experimental evaluation of pounding between BI frames. In the present research, the pounding effect in a series of combinations, such as adjacent flexible and stiffer BI frames of similar frequency and different frequency to adjacent frames, were experimentally analysed to find better combinations of adjacent structures with an expansion gap. In the experiments, the surfaces at the isolation and frame slab levels were free to impact in order to investigate direct pounding (DP) and mitigated pounding (MP) by inserting a neoprene rubber pad into the gap. The investigation was conducted by comparing BI structures with and without pounding responses as a result of the El Centro earthquake excitation. To demonstrate the extent of the pounding effect in adjacent structures, the horizontal and pounding force variations in each combination during DP and MP were evaluated. The experimental responses analysis results help in justifying a better variety of adjacent BI structures with an expansion gap. This experimental study shows that mitigating material in the gap is more efficient for nearer frequency combinations than for different frequency frame combinations.

Keywords

• pounding
• mitigated pounding
• adjacent base-isolated structures
• expansion gap
• shake table testing