Evaluation of Mean Wind Force Coefficients for High-Rise Building Models with Rectangular Cross-Sections and Aspect Ratio’s of 6 and 8

Abstract

Studies on measurement of wind loads on rigid models (geometric scale of 1:300) of tall rectangular high-rise buildings having plan dimensions of 7.5 cm (b) × 15 cm (d) with two different heights (h) of 45 cm and 60 cm, under simulated open terrain condition was carried out using Boundary Layer Wind Tunnel (BLWT) facility at CSIR-SERC, Chennai. The measurements of mean base forces (${\bar{\text{F}}}_{\text{x}}$, ${\bar{\text{F}}}_{\text{y}}$ and ${\bar{\text{F}}}_{\text{z}}$) and torsions (${\bar{\text{T}}}_{\text{x}}$, ${\bar{\text{T}}}_{\text{y}}$ and ${\bar{\text{T}}}_{\text{z}}$) were made using a six-component force/torque sensor for 8 different angles of wind incidence (θ), ranging from 0° to 90° and for 4 various mean wind velocities (${\bar{\text{U}}}_{\text{ref}}$). Based on the analysis, mean base forces/torsions in three mutually perpendicular axes, mean force coefficients in body fixed axes X and Y, mean drag, lift force and torsion coefficients were obtained corresponding to reference mean pressures measured at top of the building. It is observed that the magnitudes of measured forces/torsions for model with h/b = 8 are found to be high when compared with forces for model with h/b = 6. The evaluated values of mean force coefficients obtained from the present study were compared with the values reported in IS: 875 and found that the values given in code are found to be conservative. Further, the % difference between them is observed to be within 5 %, especially for wind direction normal to longer width of models with h/b = 6 and 8, respectively.