PSI - Issue 70

Vivek Kumar C et al. / Procedia Structural Integrity 70 (2025) 97–104

102

Story11 -458.0771 -234.1496 -459.236 -395.4253 -459.36 -369.2221 -530.4309 -359.680 Story12 -392.6696 -200.7161 -393.630 -338.9355 -393.7329 -316.4727 -415.248 -308.454 Story13 -314.8292 -160.9274 -315.554 -271.708 -315.6313 -253.6965 -298.527 -247.490 Story14 -223.4749 -114.2309 -223.923 -192.809 -223.9703 -180.0217 -180.26 -175.943 Story15 -117.5255 -60.0741 -117.652 -101.3049 -117.6653 -94.5764 -60.4343 -92.9647

Fig.5. Storey Shear at different X bracing locations

The X-bracing system is crucial for reducing lateral shear forces. At Story 1, EQx shear is -667.439 kN and EQy is -574.6987 kN, both lower than in the unbraced system. Corner shear decreases, with EQx at -665.4616 kN and EQy at -534.8814 kN. At Story 15, EQx shear is -117.652 kN and EQy is -101.3049 kN, showing further reduction compared to unbraced values of -117.5255 kN in EQx and -60.0741 kN in EQy. These reductions highlight the X bracing system's ability to redistribute shear, especially in higher stories. At Story 1, alternate location shear in EQx is -1353.565 kN, less than the unbraced -1534.774 kN, demonstrating bracing effectiveness. X-bracing reduces story shear forces, enhancing stability and minimizing shear-related failures in tall buildings. The unbraced system faces shear forces of -666.1919 kN in EQx and -340.5291 kN in EQy, reduced to -667.439 kN in EQx and -574.6987 kN in EQy with X-bracing. Although EQy shear is higher with X-bracing, overall shear is better managed due to lateral stiffness, vital as concentrated shear can cause local failures. X-bracing ensures even shear distribution throughout the building's height. At Story 15, EQx shear for the unbraced system is -117.5255 kN, while for X-bracing, it is -117.652 kN, indicating similar distribution at higher stories. This lowers structural failure risk due to excessive shear. Among X-bracing configurations analyzed, Central X-bracing proves most effective for seismic performance of multi-storey steel structures. This configuration delivers lowest displacement and shear forces across storeys, especially upper levels. Its central placement enables symmetrical load distribution with minimal torsion. 5.3. Storey Drift The study of storey drift in unbraced and X-braced systems reveals a trend in bracing effectiveness for reducing lateral movement. In the unbraced system, drift increases with height, with upper storeys experiencing more drift. At Story 1, the unbraced system records a drift of 0.000383 in EQx and 0.00154 in EQy, escalating to 0.000324 and 0.000388 at Story 15. The X-braced system shows reduced drift values at all storeys. At Story 1, it shows a drift of 0.000322 in both EQx and EQy, lower than the unbraced system. This trend continues to Story 15, where the X-braced system maintains a drift of 0.000322 in both directions.

Table 5. Storey Drift in different positions of X bracing

Unbraced

X Bracings – Storey Drift

Storey

EQx Alternate (EQy) Story15 0.000324 0.000388 0.000322 0.000322 0.000987 0.000987 0.00034 0.00034 EQy Centre (EQx) Centre (EQy) Corners (EQx) Corners (EQy) Alternate (EQx)