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Seismic Isolator Tests

The safe and reliable implementation of seismic isolation requires verifying the properties and capacities of the isolators through testing.

Quality Control Tests are performed on every isolator to verify the isolator properties used in the design of the isolated structure

Prototype Isolator Tests are performed on two representative isolators of each isolator size and type, to verify the adequacy and properties of the isolation system. The Prototype Isolator Tests include Real-Time Property Tests and Isolator Capacity Tests.

Real-Time Property Tests measure the dynamic properties of the prototype isolators over the range of applicable loads and displacements used in the design. The measured isolator properties from these tests are used in the modeling of the isolator properties in the design and analysis of the structure.

Isolator Capacity Tests ensure that the prototype isolators exhibit safe structural behavior during the strongest earthquake shaking considered in the structure design. To prevent the collapse of a seismically isolated structure, it is very important that the seismic isolation isolators have the strength and stability to withstand Maximum Considered Earthquake (MCE) shaking without structural isolator failures.

The Isolator Capacity Tests check the prototype isolators for significant structural degradation caused by the combined design compression and shear loading under MCE conditions. Isolators need to be able to dissipate the energy from long duration MCE shaking when tested at the isolated natural period TM. They also need to be able to safely accommodate short duration uplift displacements or tension loads, and afterwards maintain their lateral strength and stiffness when loaded again at the design compression loading. While supporting the design vertical load, the isolator should maintain a positive incremental lateral stiffness as the lateral loads are incrementally increased up to the calculated MCE shear load and displacement. If a positive incremental lateral stiffness is not maintained, isolator displacements larger than the calculated design displacement will occur, which may cause isolation system instability and complete structure collapse.

Detailed testing requirements are given for Buildings and Bridges below.