Seismic Stiffening Strategies for a Tall Y-Shaped Building: An Innovative Distributed Belt Wall System

With rapid urban growth and the use of complex geometries like tall Y-shaped reinforced concrete structures, the seismic vulnerabilities are further accentuated due to irregularities in plan that induce torsional responses. These irregularities become additional demands on structural systems and need to be taken up by lateral load-resisting mechanisms satisfactorily. This study investigates the seismic behaviour of Y-shaped structures for two major systems: SMRF and FTS with five different stiffening alternatives comprising the conventional outrigger/belt system and a new distributed belt wall system. Dynamic loadings were numerically simulated with ETABS, conversional among linear elastic static (Equivalent Static Load-ESL) and dynamic (Modal Response Spectrum Analysis-RSA) loadings. The analysis parameters included modal period, lateral deflections, storey drifts, seismic base shear, overturning moments, and torsional irregularities. From the results, it was found that the FTS actually exhibits better control of stiffness and deformation compared to SMRF with all stiffening arrangements having some positive impact on performance when compared with the bare core-wall system. The distributed belt wall system, in particular, dramatically reduces deflections, drifts, as well as torsional effects, especially when employed with the FTS, thereby enhancing the resilience of the structure. However, stiffer systems, particularly the distributed belt wall, increase seismic base shear, which is a foremost consideration for design. Considered better from seismic point of view, Y-shaped building integrated with distributed belt wall, the inherent complex torsional behaviour of Y-shaped buildings makes three-dimensional dynamic analysis a must. The foregoing findings thus serve as valuable guidelines for the design of earthquake-resistant buildings with complex geometry.