ICCESD Islam et al 2012 Tall building.pdf (original) (raw)

Abstract

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Sustainable development of drift control is crucial for maintaining the lateral deflection of tall buildings within acceptable limits to ensure the proper functioning of nonstructural components and to prevent distress due to excessive deflection. Various structural systems are analyzed for their drift indices, which quantify the lateral stiffness and stability under wind and seismic loads. The analysis highlights the importance of selecting an appropriate structural form to enhance building rigidity and stability, particularly as building heights increase.

Figures (9)

Six major structural systems are selected to investigate the drift pattern due to lateral loading; they are framed system, braced-frame system, tubular system, shear wall-frame system, outrigger-braced system and hybrid system. A 20 storied frame system is considered as a prototype model for the analysis. The plan of framed system and shear wall-frame system are shown in Figure l(a) and (b). Table | provides the short description of the structural system analyzed in this research work. The tall buildings of different structural system are modeled considering 20 stories with story height 12.5ft using STAAD.Pro 2006, which is a structural analysis software. The thickness of the shear walls are considered 12in. The sizes of the beams are 12in x 20in and columns are 24in x 24in. The thickness of the shear walls are considered 12in, the cross sections of all the bracings are considered 12in x 12in and cross section of the outrigger beam is considered 12in x 48in. The wind load is applied as per BNBC (1993) considering exposure condition A and wind velocity 210 km/hr. Thus the lateral deflection due earthquake is much less compared to the wind load so wind load is considered as the governing lateral load for drift analysis in this research. Fixed support is applied at the base of the structures.

Six major structural systems are selected to investigate the drift pattern due to lateral loading; they are framed system, braced-frame system, tubular system, shear wall-frame system, outrigger-braced system and hybrid system. A 20 storied frame system is considered as a prototype model for the analysis. The plan of framed system and shear wall-frame system are shown in Figure l(a) and (b). Table | provides the short description of the structural system analyzed in this research work. The tall buildings of different structural system are modeled considering 20 stories with story height 12.5ft using STAAD.Pro 2006, which is a structural analysis software. The thickness of the shear walls are considered 12in. The sizes of the beams are 12in x 20in and columns are 24in x 24in. The thickness of the shear walls are considered 12in, the cross sections of all the bracings are considered 12in x 12in and cross section of the outrigger beam is considered 12in x 48in. The wind load is applied as per BNBC (1993) considering exposure condition A and wind velocity 210 km/hr. Thus the lateral deflection due earthquake is much less compared to the wind load so wind load is considered as the governing lateral load for drift analysis in this research. Fixed support is applied at the base of the structures.

Table 1: Description of the structural systems

Table 1: Description of the structural systems

Figure 4: Effect of large-scale bracing system (a) lateral deflection (b) inter-story drift. In case of large-scale bracing in Figure 4(a), the reduction of drift is extensively higher compared framed system, even the bracing at the external frame reduced the drift of the whole structure most efficiently. The inter-story drift in Figure 4(b) shows that the reduction of drift started from the 2" floor and lower at the connection floors of the bracings. For diagonal bracing, K bracing and double K bracing in Figure 5(a) & (b), the reduction is quite similar to large-scale bracing at exterior frame.

Figure 4: Effect of large-scale bracing system (a) lateral deflection (b) inter-story drift. In case of large-scale bracing in Figure 4(a), the reduction of drift is extensively higher compared framed system, even the bracing at the external frame reduced the drift of the whole structure most efficiently. The inter-story drift in Figure 4(b) shows that the reduction of drift started from the 2" floor and lower at the connection floors of the bracings. For diagonal bracing, K bracing and double K bracing in Figure 5(a) & (b), the reduction is quite similar to large-scale bracing at exterior frame.

Figure 7: Effect of shear wall-frame system (a) lateral deflection (b) inter-story drift.

Figure 7: Effect of shear wall-frame system (a) lateral deflection (b) inter-story drift.

Figure 8: Effect of outrigger-braced system (a) lateral deflection (b) inter-story drift.

Figure 8: Effect of outrigger-braced system (a) lateral deflection (b) inter-story drift.

Hybrid shear wall-diagonal bracing system is found to be the most efficient structural system in reducing the drift of the tall buildings (Figure 9a). The efficiency of hybrid shear wall-outrigger beam system is more or less similar to shear wall-frame system. The inter-story drift of the hybrid s ow from 2"* story which results in the lesser lateral deflection (Figure all the structural systems and are shown in Figure 10. It is clearly visib hear wall-diagonal bracing system is also 9b). The drift indexes are calculated for e that the drift index is the minimum for hybrid shear wall-diagonal bracing system (H1) and is followed by large-scale diagonal bracing system (B2) and both lie below 0.0015. With these two systems, B1, B5 and S2 also lie ound effective in reduction of the drift of tall buildings for abov below the limit of ASCE 7-05 (2005) i.e. drift index below 0.0025. Again F2, B4, S1, S3 and H2 structural systems are found to be lower drift index below 0.003 as for the requirement for conventional tall buildings. Tubular system and outrigger system are not e considering specifications. Following expression shows the comparative situation of the structural systems with respect to drift index:

Hybrid shear wall-diagonal bracing system is found to be the most efficient structural system in reducing the drift of the tall buildings (Figure 9a). The efficiency of hybrid shear wall-outrigger beam system is more or less similar to shear wall-frame system. The inter-story drift of the hybrid s ow from 2"* story which results in the lesser lateral deflection (Figure all the structural systems and are shown in Figure 10. It is clearly visib hear wall-diagonal bracing system is also 9b). The drift indexes are calculated for e that the drift index is the minimum for hybrid shear wall-diagonal bracing system (H1) and is followed by large-scale diagonal bracing system (B2) and both lie below 0.0015. With these two systems, B1, B5 and S2 also lie ound effective in reduction of the drift of tall buildings for abov below the limit of ASCE 7-05 (2005) i.e. drift index below 0.0025. Again F2, B4, S1, S3 and H2 structural systems are found to be lower drift index below 0.003 as for the requirement for conventional tall buildings. Tubular system and outrigger system are not e considering specifications. Following expression shows the comparative situation of the structural systems with respect to drift index:

Figure 10: Drift index of the structural systems.

Figure 10: Drift index of the structural systems.

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References (6)

  1. ASCE 7-05, (2005), "Minimum Design Loads for Buildings and Other Structures," ASCE/SEI 424. Bangladesh National Building Code (BNBC), (1993), Housing and Building Research Institute and Bangladesh Standards and Testing Institutions.
  2. El-Leithy, N. F., Hussein, M. M. and Attia, W. A. (2011), "Comparative Study of Structural Systems for Tall Buildings", Journal of American Science, Vol: 7(4).
  3. Islam, M.M., Siddique, A. and Murshed, A. (2011), "Sustainable Development in Drift Control of Tall Buildings: Study of the Structural Parameters", 4th Annual Paper Meet and 1st Civil Engineering Congress, Civil Engineering Division, Institution of Engineers, Bangladesh (IEB).
  4. Lee, J., Bang, M. and Kim, J. (2008), "An Analytical Model for High-Rise Wall-Frame Structures with Outriggers", THE STRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGS, Struct. Design Tall Spec. Build. Vol: 17, 839-851, Published online 1 October 2007 in Wiley Interscience (www.interscience.wiley.com).
  5. Mendis, P. Ngo, T. Hariots, N. Hira, A. Samali, B. Cheung, J. (2007). "Wind Loading on Tall Building", EJSE Special Issue: Loading on Structures, 41-54.
  6. Smith, B.S. & Coull, A. (1991). "Tall Building Structures: Analysis and Design", Singapore: John Wiley & Sons, Inc.