An equivalent coupled-two-beam (CTB) discrete model is presented to compute the dynamic response in time domain of flexible-base buildings with linear fluid viscous dampers (FVDs). The equivalent model consists of a flexural cantilever beam and a shear cantilever beam connected in parallel by a finite number of axially rigid members that allows the consideration of intermediate modes of lateral deformation. The effects of different lateral deformations on the pre-design stage of two high-rise buildings are showed considering four soil types (hard rock, dense soil, stiff soil and soft soil) and three different distribution methods for linear FVDs: uniformdistribution (UD), story-shear-proportional-distribution (SSPD) and story-shear-strain-energy-distribution (SSSED). For UD method, the damping coefficients of FVDs increase as the flexural rigidity of the building decreases; whereas for SSPD and SSSED methods, the damping coefficients of FVDs vary along the height depending on the type of lateral deformation. For the three distribution methods and the same lateral deformation, the damping coefficients of FVDs decrease as the soil flexibility increases, which leads to a significant decrease in controlling earthquake-induced vibrations and wind-induced vibrations in the two high-rise buildings on a soft soil.

Introduction

Increasing urbanisation in recent decades has led to the construction of high-rise buildings worldwide, which are susceptible to seismic and wind loads. Currently, the structural design of tall buildings must satisfy different criteria such as strength, ductility, stability, resilience, sustainability, among others. Earthquake engineering is usually governed by the ultimate limit state, where peak displacements are of great importance to avoid damage in the structure. On the other hand, wind engineering is usually governed by the serviceability limit state, where root-mean-square (RMS) accelerations are of great importance to avoid human discomfort. The lateral deformation of buildings strongly depends on the type of lateral resisting system, which is usually depends on the height of the building. Accordingly, low-rise buildings usually deform like pure shear beams; whereas in medium-rise and high-rise buildings, the flexural deformation is as significant as the shear deformation. Simplified continuous models are one of the most used procedures for pre-design complex structures and performing parametric analyses to identify the most important variables during the design process. The continuous Timoshenko beam [1] reflects a series coupling of the beam’s bending and shear stiffnesses, while the coupled-two-beam (CTB) continuous model [2] couples the bending and shear stiffnesses in parallel.