P-Delta Mass Rig System for Shake Table Tests of Slender Cantilever Columns Open Access
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Shake table tests are used to simulate ground motions and their effects on structures when these are excited by earthquakes. Numerous experiments have been conducted to better understand the behavior of cantilever columns under such excitations. However, there is a lack of testing that can be used to better quantify the response of slender columns influenced by P-Delta effects. In the presence of P-Delta effects, slender columns experience destabilizing moments that can lead to the instability of the test specimen, thus requiring additional safety remediation during testing.A literature review shows different mass setups have been used for shake table tests. In one approach the mass is directly connected and placed on top of the column. In other setups the mass is placed on top of a rigid tower placed next to the shake table. This is also designated in the literature as a mass rig system. This system forms a horizontally constraint-free mechanism providing the required inertial dynamic loading during the testing procedure. The transfer of the inertial forces will be realized by connecting the top of the columns to the inertial mass by a rigid link. Although, a mass rig system removes several safety concerns associated with shake table testing of cantilever columns, the mass rig systems proposed to date do not properly represent the P-Delta effects that slender columns experience during ground motions. In this research, a new mass rig system is proposed that attempts to mitigate this deficiency by placing the inertia mass on a convex surface. Design of the convex surface is achieved by ensuring that the equations of motion for the inertia mass on the convex surface lead to the same solution as if the mass was placed directly on the column. In this research, the proposed mass rig system consists of a rigid link that connects the inertial mass to the top end of the column, and the mass is constrained to move along a predefined path using rails and roller coaster like connections. Through the research the mass rig system is numerically analyzed and validated using experimental data. The objectives of the research outlined in this Master thesis are as follows:* Design a new mass rig system for shake table tests of slender columns.* Derive the equation of motion for the proposed mass rig system.* Validate the numerical simulations based on shake table tests.