- Volume 16 Issue 1
DOI QR Code
Internal and net roof pressures for a dynamically flexible building with a dominant wall opening
- Sharma, Rajnish N. (Department of Mechanical Engineering, The University of Auckland)
- Received : 2011.07.29
- Accepted : 2012.03.12
- Published : 2013.01.25
This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.
- American Society of Civil Engineers (ASCE). (2005), ASCE 7-05 - Minimum Design Loads for Buildings and Other Structures, Part 6: Wind loads. ASCE/SEI 2005.
- Ginger, J.D., Holmes, J.D., and Kopp, G.A. (2008), "Effect of building volume and opening size on fluctuating internal pressure", Wind Struct., 11(5), 361-376. https://doi.org/10.12989/was.2008.11.5.361
- Guha, T.K., Sharma, R.N. and Richards, P.J. (2012), "Internal pressure dynamics of a leaky and quasistatically flexible building with a dominant opening", accepted for publication in Wind Struct.
- Holmes, J.D. (1980), "Mean and fluctuating pressures induced by wind", Proceedings of the 5th International Conference on Wind Engineering, Colorado State University 1979, Peragmon, Oxford.
- Hoxey, R.P. and Richards, P.J. (1995), "Full-scale wind load measurements point the way forward", J. Wind Eng. Ind. Aerod., 57(2-3), 215-224. https://doi.org/10.1016/0167-6105(94)00116-U
- Liu, H. and Saathoff, P.J. (1981), "Building internal pressure: sudden change", J. Eng. Mech.- ASCE 107(2), 309-321.
- Novak, M. and Kassem, M. (1990), "Effect of acoustical damping on free vibration of light roofs backed by cavities", J. Wind Eng. Ind. Aerod., 36(1), 289-300. https://doi.org/10.1016/0167-6105(90)90313-2
- Oh, J.H., Kopp, G.A. and Inculet, D.R. (2007), "The UWO contribution to the NIST aerodynamic database for wind loads on low buildings: Part 3. internal pressures", J. Wind Eng. Ind. Aerod., 29, 293-302.
- Pearce, W. and Sykes, D.M. (1999), "Wind tunnel measurements of cavity pressure dynamics in a low-rise flexible roofed building", J. Wind Eng. Ind. Aerod., 82(1-3), 27-48. https://doi.org/10.1016/S0167-6105(98)00213-X
- Robertson, A.P. (1992), "The wind-induced response of a full-scale portal framed building", J. Wind Eng. Ind. Aerod., 41-44, 1677-1688.
- Sharma, R.N. (2011), "Internal pressures in single compartment and partitioned two-compartment buildings with a dominant opening", IN REVIEW, J. Wind Eng. Ind. Aerod.
- Sharma, R.N. (2008), "Internal and net envelope pressures in a building having quasi-static flexibility and a dominant opening", J. Wind Eng. Ind. Aerod., 96(6-7), 1074-1083. https://doi.org/10.1016/j.jweia.2007.06.029
- Sharma, R.N. (2003), "'Internal pressure dynamics with internal partitioning", Proceedings of the 11th International Conf. on Wind Engineering, Texas Tech University, Lubbock Texas, June.
- Sharma, R.N. (1996), The influence of internal pressure on wind loading under tropical cyclone conditions. PhD Thesis in Mechanical Engineering, The University of Auckland.
- Sharma, R.N., Mason, S. and Driver, P. (2010), "Scaling methods for wind tunnel modelling of building internal pressures induced through openings", Wind Struct., 13(4), 363-374. https://doi.org/10.12989/was.2010.13.4.363
- Sharma, R.N. and Richards, P.J. (2005), "Net pressures on the roof of a low-rise building with wall openings", J. Wind Eng. Ind. Aerod., 93(4), 267-291. https://doi.org/10.1016/j.jweia.2005.01.001
- Sharma, R.N. and Richards, P.J. (2004), "The multi-stage process of windward wall pressure admittance", J. Wind Eng. Ind. Aerod., 92(14-15), 1191-1218. https://doi.org/10.1016/j.jweia.2004.07.004
- Sharma, R.N. and Richards, P.J. (2003), "The influence of helmholtz resonance on internal pressures in a low-rise building", J. Wind Eng. Ind. Aerod., 91(6), 807-828. https://doi.org/10.1016/S0167-6105(03)00005-9
- Sharma, R.N. and Richards, P.J. (1997a), "Computational modelling of the transient response of building internal pressure to a sudden opening", J. Wind Eng. Ind. Aerod., 72 (1-3), 149-161. https://doi.org/10.1016/S0167-6105(97)00244-4
- Sharma, R.N. and Richards, P.J. (1997b), "The effect of roof flexibility on internal pressure fluctuations", J. Wind Eng. Ind. Aerod., 72, 175-186. https://doi.org/10.1016/S0167-6105(97)00252-3
- Standards Australia and Standards New Zealand. (2002), AS/NZS 1170.2:2002 Structural design actions Part 2: Wind actions.
- Stull, R.D. (1988), An Introduction To Boundary Layer Meteorology, Atmospheric Sciences Library, Kluwer Acamedic Publishers, The Netherlands.
- Vickery, B.J. (1994), "Internal pressures and interactions with the building envelope", J. Wind Eng. Ind. Aerod., 53(1-2), 125-144. https://doi.org/10.1016/0167-6105(94)90022-1
- Vickery, B.J. (1986), "Gust factors for internal-pressures in low-rise buildings", J. Wind Eng. Ind. Aerod., 23, 259-271. https://doi.org/10.1016/0167-6105(86)90047-4
- Vickery, B.J. and Bloxham, C. (1992), "Internal pressure dynamics with a dominant opening", J. Wind Eng. Ind. Aerod., 41, 193-204. https://doi.org/10.1016/0167-6105(92)90409-4
- Vickery, B.J. and Georgiou, P.N. (1991), "A simplified approach to the determination of the influence of internal pressures on the dynamics of large span roofs", J. Wind Eng. Ind. Aerod., 38(2-3), 357-369. https://doi.org/10.1016/0167-6105(91)90054-Z
- Wind pressure characteristics of a low-rise building with various openings on a roof corner vol.21, pp.1, 2015, https://doi.org/10.12989/was.2015.21.1.001