EFFECT OF PLAN SHAPES ON THE RESPONSE OF TALL BUILDINGS UNDER WIND LOADS

Abstract

The evaluation of wind loads on building is carried out by using relevant codes/standards and available literature. The codes/standards suggest the pressure coefficients and force coefficients for the standard plan shape buildings, but do not cover too elongated and uncommon plan shape. Due to all these facts the wind pressure estimation for tall buildings are very much important. Therefore, attempts have been made in the present study to find the wind force and pressure distributions on the building models having different plan shape but keep same height. The present study has been made in two phases namely wind tunnel experiments and response analysis. The aim of the experimental study is to carryout extensive wind tunnel testing on rigid model of square, rectangular and T-shaped building to evaluate pressure coefficients on different faces of building model. Building models having square, rectangular, L and T- plan shape are used in the present study. Ply sheet is used for force measurement and transparent Perspex sheet (6mm thickness) used for pressure measurement. Building models is made in the geometrical model scale ratio of 1:200. An open terrain wind model classified as terrain category 2 was simulated using a set of small cube box and roughness elements placed upstream of the building model inside the wind tunnel. Detailed experimental studies are carried out to find the force and pressure coefficients around the building model considering isolated and interference effect on building model. Force coefficient are evaluated using load cell for different wind angles and spacing whereas fluctuating values of wind pressure at all pressure points on different surfaces of building models. Various instruments are also used along with the data acquisition system for force measurement and surface pressure measurement over the entire building model in the wind tunnel. To obtain the analytical response of the buildings, STAAD Pro software package is used in the present study. Only linear static method is considered for analyzing the building frames for dead load, live load and wind load combination. The mean responses i.e, base shear and base moment of pair of buildings located in close proximity of geometric configurations having T-plan shaped is evaluated using the experimentally obtained mean pressure coefficient. Block-Di and block-D2 of T-shaped building is analyzed for wind incidence angle 0° using experimentally obtained pressure coefficient and the response i.e, base shear is compare with force obtained from rigid model test at a geometrical scale of 1:200. 9.6% error is found to differ between the software and experimental results .This percentage error is under the acceptable range (0-15%) which shows that the present study on wind tunnel achieves high degree of accuracy.