www.cafetinnova.org ISSN 0974-5904, Volume 10, No. 02 DOI:10.21276/ijee.2017.10.0235 April 2017, P.P. 378-382 Received: December 11, 2016; Accepted: February 27, 2017; Published: April 26, 2017 International Journal of Earth Sciences and Engineering, 10(02), 378-382, 2017, DOI:10.21276/ijee.2017.10.0235 Copyright ©2017 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved. Effect of Height Variation of Closely Located Interfering Buildings on Wind Loads on Tall Buildings BHARAT SINGH CHAUHAN AND ASHOK KUMAR AHUJA Department of Civil Engineering, Indian Institute of Technology Roorkee-247667, Uttarakhand, INDIA Email: bharat32@gmail.com, ahujashok@gmail.com Abstract: This research paper investigates the modification of wind loads on a tall building (principal building) having rectangular cross-sectional shape due to the variation in height of two closely located interfering buildings having a similar plan shape. The models of the three buildings (principal and interfering buildings) are placed in a U shape plan for the study. The heights of interfering building models are varied in two different manners: (1). Height of both the interfering building models is reduced simultaneously (2). Height of only one of the interfering building model is reduced. Wind tunnel experiments are undertaken using five component force balance load cell and the results are reported in the form of X-Y plots. The interference effect causes increase in the torsional moment as height difference of the two interfering buildings increase, also shielding effect causes reduction in the along wind force as height of the interfering buildings increases. Value of torsion on the principal building is observed to be as high as 33 times of that in the isolated case. However, a reduction is high as 69 percent is observed in the force in along wind direction due to shielding. Keywords: Wind tunnel, Tall building, Rectangular plan, Interference effects, Height variation, U-Shape, Force measurement. 1. Introduction With the growing demand of tall buildings in metropolitan cities due to population concentration, the wind tunnel studies to understand effects of wind on these tall buildings have started to become inevitable. Information available in various codes of practice on wind loads [AS/NZS: 1170.2 (2002), ASCE: 7-02-2002, EN: 1991-1-4-2005, IS: 875 (Part- 3) 2015] provide guidance limited to isolated cases only. Many researchers have carried out the studies in the area of the effect of wind on tall buildings due to the presence of other interfering buildings. It has been shown that the wind loads on tall buildings are greatly affected in the presence of closely located interfering buildings [Khanduri et al. (1998)]. The significance of interference studies on wind loads on tall buildings has been shown by several research studies in the past. Khanduri et al. (1998) analyzed the experimental data available on interference studies and concluded that the wind loads on the principal building are greatly affected if the interfering building is closely located. Xie and Gu in 2004 studied the effect of interference on square plan shaped principal building due to the presence of one and two interfering buildings also having square plan shape by varying the location, height and plan size of the interfering buildings. In 2008 Amin carried out wind tunnel experiments to study the effect of interference on rectangular plan shape buildings having aspect ratio of 1:2.5 and 1:1.5 due to the mutual presence of the buildings arranged in L - and T -shape patterns, concluding that the wind loads on the buildings are greatly affected by the arrangement, wind direction and relative dimensions of the buildings. Zhao and Lam (2008) studied the effect of mutual presence on 5 square plan shaped buildings arranged in L- and T- shape patterns with a variation in spacing amongst the buildings and the wind direction. Kim et al. (2011) carried out wind tunnel studies to understand the interference effects on local peak pressures on a square plan shape tall building due to the presence of an interfering building having a similar shape with a variation in wind direction, location and height of the interfering building. Kushal (2013) had conducted wind tunnel experiments to study the effect of interference on rectangular plan shape tall building due to the presence of a square plan shape tall building by varying the spacing amongst the buildings arranged in L- and T- shape patterns. Pandey (2013) studied the effect of presence of two square plan shape tall buildings on a similar plan shape principal building with a variation in wind direction and spacing of the buildings. Mara et al. (2014) undertook wind tunnel experiments to study the aerodynamic and peak response interference factors on square plan shape buildings due to the presence of another identical building at different upstream positions. Yan and Li (2016) carried out Wind tunnel experiments to understand the interference effects between identical tall buildings with aerodynamic modifications by varying the location of the interfering building. Going through the literature it can be observed that the wind loads are greatly affected by the relative dimensions and location of the buildings. However, it can be observed that no research is available for interference studies on commonly used rectangular plan shape tall buildings due to the presence of closely located two