Development of floating rubber-concrete isolation slab system for 3D vibrations

Abstract

Nowadays by implementing of various machineries and equipment, the structures are subjected to multidirectional vibrations as combination of vertical and horizontal cyclic oscillations. The slabs are the main structural components, imposed to the dynamic loads due to vibrating generator machines and the load is transferring from slabs to the foundation through the girders and columns.Recently, application of the high damping rubber bearings to the structures as base isolator systems to dissipate imposed dynamic loads is frequently considered by design engineers, mainly for controlling horizontal vibrations. However, in order to isolate machine-induced vibrations, it is required to isolate the machine itself within the story.Therefore, in the present research an attempt has been made to develop a floating rubber-concrete isolation slab system (FRCISS) by implementing High Damping Rubber (HDR) under the floating slab system. The components of the proposed system are designed based on required criteria and the performance of the developed FRCISS in reducing vibrations in both horizontal and vertical directions are investigated through finite element method.Thereafter, two prototypes of FRCISS slabs have been casted and experimentally tested under horizontal and vertical cyclic loadings by using dynamic actuator in order to validate the model. Eventually, the new proposed FRCISS is applied on lab-size 3-story, 1-bay buildings numerically. In each building, the floating system is installed within a different story and is subjected to dynamic load. Then the dynamic response of the structures with floating systems are compared with the dynamic response of conventional structures in order to assess the capability of FRCISS to diminish vibration effect.For interior vibrations, the lateral drifts in the structure with floating systems in the 1st, 2nd, and 3rd stories under horizontal cyclic loading were reduced by an average 87.33%, 62.21% and 47.08%, compared to lateral drifts in conventional structures, respectively, while the deflection under vertical loading was reduced by 11.1%. Whereas, the average drift reduction values were 69.68%, 26.08%, and 20.18% under the north-south seismic component, and 74.03%, 17.1%, and 16.55% under the east-west seismic component, for the modified buildings compared to conventional buildings. The current study contribution is summed up in demonstrating the possibility of implementing HDR in the floating slabs to isolate horizontal and vertical vibrations and protect the machinery.