Protection Retainer Based on Tensile Fusing Units and Performance Tests

Abstract:

Protection retainer with fusing pins used in isolators often lead to asynchronous failure owing to the brittle fracture when a group of pins are employed. Stress concentration in the necked zone may cause fatigue failure under functional loads. A protection retainer with tensile fusing units was presented in the study, in which the external lateral load was transferred as tensile force exerted on the fusing units by a deviator. The tensile fusing units had certain length of necked section that provides essential ductility to prevent brittle fracture. Smooth section transition with relatively large radius was used to enhance the capacity in resisting fatigue loads. Static tests on shear pins, tensile fusing units and the new retainer with multiple tensile fusing units were conducted. The results showed that the tensile fusing units have much larger ultimate deformation capacity than the shear pins and the ductile capacity of the tensile fusing units can be adjusted with different length of the necked zone. The tested retainers exhibited consistent ultimate loading capacity as predicted by the theoretical equations and small discreteness with repeatability tests. This indicates that the tensile fusing units in the retainers can work in sync. Furthermore, fatigue tests on the shear pins and the tensile fusing units were conducted and the results showed evidently higher fatigue resistance of the tensile fusing units.

Key words:isolator; protection retainer; tensile fuse units; limit ductility; fatigue property