Use Of Outrigger, Belt Wall And Bracing Systems In High Rise Building Subjected To Wind Loads
Mohammed Arsalaan Wajid,  Dr. S. Amaresh Babu
In the fast changing and ever evolving world of today, high-rise structures with innovative designs have become the norm. Even though these structures are a marvel to look at, they have their own fair share of problems. As one goes higher, the wind forces become a huge obstacle that needs to be dealt with effectively in order to ensure the security of the residents. After extensive research and trial runs, many creative solutions have come up to tackle the effect of wind energy. In the present study, an attempt is made to effectively reduce the lateral displacement caused by wind forces with the help of a belt wall, optimally placed outriggers and a proper bracing system.
In this research, with the assistance of Outrigger / Belt wall / Bracing systems, an effort has been made to assess an economical technique of decreasing lateral displacement of the structure owing to wind forces. The present study takes in consideration an elliptically planned height structure of about 320 m, the structure consists of 78 above ground level stories and 2 below. It comprises of an elliptical core as lateral load resisting system. The structure is studied with (i) Core wall (ii) Core wall with Outrigger (iii) Core wall with Belt wall (iv) Core wall with combination of Outrigger and Belt wall and (v) Core wall with Bracing systems. The thickness of outrigger/Belt wall is varied from 300mm to 500m with a step of 100.
The Outrigger/Belt wall system is provided on different levels and in some cases, it is provided on two different levels. The Outrigger/Belt wall is provided only on plant floors/refuge floors/mechanical floor. The bracing system is studied only at level 70 only with cross sectional areas and with different materials (concrete and steel). There are four plant floors in the model structure, which are at level 17, 51, 70 and at roof level. The parameters discussed in this study are the lateral displacement, which occurs at the roof level of the structure along with the moment reduction shared by the elliptical core that is caused by wind forces and the moment shared by the combination system, i.e. the bracing system, outriggers and the belt wall. After much trial and error, it was established that the optimum location of a single outrigger or belt wall was level 51. For two different levels, the best location was found to be at level 17 and level 70.
On the other hand, the use of bracing system drastically reduced the lateral displacement of the building right down to the permissible value but it was found to be ineffective when it came to reducing the moment shared by the core. Out of all the options and various permutations and combinations, the safest and most economical setup was found to be combination of belt wall and outrigger at two levels i.e. level 17 and level 70.
This study also shows that the lateral displacement of the structure can be minimized by enlarging the size of the central core or in other words simply increasing the stiffness of the building. However, the drawback of this method is the exponential increase in the cost of the structure thereby making it profligate, because the increase in size of core directly results in the increase in volume of concrete used, which is negligible when the combination system proposed in this study is utilized.
Keywords- Outrigger, belt wall , bracing system, wind loads
Unique Identification Number - IJEDR2001015Page Number(s) - 75-81Pubished in - Volume 8 | Issue 1 | January 2020DOI (Digital Object Identifier) -    Publisher - IJEDR (ISSN - 2321-9939)
Cite this Article
Mohammed Arsalaan Wajid,  Dr. S. Amaresh Babu,   "Use Of Outrigger, Belt Wall And Bracing Systems In High Rise Building Subjected To Wind Loads"
, International Journal of Engineering Development and Research (IJEDR), ISSN:2321-9939, Volume.8, Issue 1, pp.75-81, January 2020, Available at :http://www.ijedr.org/papers/IJEDR2001015.pdf