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基础隔震曾建议用作很多建筑和结构类型抗震设计的一种经济的途径。一般,具有极低水平刚度的支承系统限制了水平力从地面往结构的传递,使结构的基础被隔开,然而,由于支承系统的水平刚度是如光的低,以致这类结构在风荷作用下的位移太大,例如,一个具有隔震的自振频率为0.5Hz的建筑在为建筑重量1/10的风力作用下其水平变形将达4英寸。这样的“水平变形是难以接受的,但基础隔震系统可装备一种机械保险梢”,它足以抵抗风力,但在地震时断裂,使建筑脱离隔震系统。本报告中我们阐述了这种装置的一系列振动台试验,风力制动器由带有切口的剪力梢组成,对几种剪力梢和置于40000磅重三层钢框架模型下的天然橡胶隔震系统一起进行了试验。被试的剪力梢的断裂力从模型重量的3％～20％,模型结构受三种地震的不同拳道加速度激励。剪力梢突然而干脆地断裂,对各种梢的断裂力能合理地予计。虽然在梢断裂时,在模型结构中引起高振型的加速度,但很快消失。在本报告的末尾,根据试验结果,讨论了对足尺结构剪力梢“机械保险梢”的设计。
Base isolation has been proposed as an economical approach to the seismic design of many architectural and structural types. In general, support systems with very low horizontal stiffness limit the transfer of horizontal forces from the ground to the structure, leaving the foundation of the structure isolated, however, because the horizontal stiffness of the support system is low, such as light, such structures in the wind load The displacement under action is too large. For example, a building with an isolated natural vibration frequency of 0.5 Hz will have a horizontal deformation of up to 4 inches under a wind force of 1/10 of the building weight. Such “horizontal deformation is unacceptable, but the base isolation system can be equipped with a mechanical safety guard,” which is sufficient to resist the wind, but breaks during the earthquake, so that the building is separated from the seismic isolation system. In this report we describe a series of shaking table tests of this device. The wind brake is composed of a shear tip with a notch, several shear tips and a natural rubber spacer placed under a 40000-pound three-layer steel frame model. The earthquake system was tested together. The shear force of the shear tip of the test was from 3% to 20% of the model weight. The model structure was stimulated by the acceleration of different knuckles of the three kinds of earthquakes. The shear pintle suddenly and simply breaks, and the fracture force at various tips can be reasonably predicted. Although high-speed accelerations are induced in the model structure when the tip breaks, they quickly disappear. At the end of this report, based on the test results, the design of a “safety tip” for full-scale structural shear tips was discussed.