Full Paper Proc. of Int. Conf. on Advances in Civil Engineering 2012
Effectiveness of Dome Structures in Reduction of Stresses under Transverse Loadings Ashim Kanti Dey1, Chinmoy Deka2 1
Department of Civil Engineering, National Institute of Technology, Silchar, Assam -10, India Email: ashim_kanti@yahoo.co.in 2 Department of Civil Engineering, National Institute of Technology, Silchar, Assam -10, India Email: cdekanits@gmail.com Abstract— In the present study effectiveness of dome shaped roofing in reduction of deformations under lateral loading is discussed. A comparison was made between a flat roof structure and a dome roof structure on deformations imposed under lateral loading. STAAD Pro software was used to evaluate deformations, bending moments and shear forces under different combinations of loads. For the same column and beam sizes it was observed that deformation in dome roof structure is 30% less than that in flat roof structure. Similar reduction in bending moments and shear forces were also observed. On the other hand, for the same deformation, the sizes of columns were needed to be increased by 40% in the flat roof structure. The present study concludes that a considerable amount of material and money can be saved in choosing a dome shaped roof with a marginal loss in floor area and a total loss of the utility of a flat roof.
transverse loadings in comparison to a conventional flat roof structure. The same seismic load combinations were applied to both the flat roof and dome shaped roof frames using STAAD Pro software [3]. The values of deformation, maximum bending moment and maximum shear force in columns were compared. It was observed that the structure with dome shaped roof was more effective against transverse loads. II. METHODOLOGY A. Dome Shaped Structure Concept Dome shaped structures have been used in ancient times such as the Mughal era with the purpose of lending symmetry and enhancing the beauty of buildings. Research has been carried out on the effect of wind load on dome shaped structures. In a study on the buckling effect of wind load on cylindrical tanks with dome shaped roof, it was seen that there is a low imperfection sensitivity of the tanks for buckling loads associated with wind speeds 45% higher than those specified by the ASCE 7-02 standard [4]. The design and construction method used for a dome subjected to wind loads has been also studied [5]. It was concluded that the pressure coefficients obtained using Fourier series formulation are in close agreement with those obtained by experimental work. However very limited research works have been reported on the possibility of use of dome shape roof to resist transverse loads. The idea behind the present study originated from the fact that a structure may not collapse by virtue of its shape. In this respect a dome shaped structure is more stable than a rectangular frame. During shaking the position of centre of gravity (C.G) of a rectangular structure is shifted whereas there is little shift of C.G of a dome. The outer shell of a dome is under compression in ordinary loading. With a transverse load little or no tension is developed in the shell, whereas, tension is developed in the outer column of the frame structure. Reversal of stresses due to load reversal causes damage and spalling of concrete. Thus a dome shaped roof is supposed to withstand higher loads than a flat roof. With this concept in mind it is proposed to try a structure with dome shaped roof under transverse load. Since the entire structure can’t be made dome shaped because of limitation of space and utility, it is proposed to make at least two/three top floors dome shaped. The present analysis has made a
Index Terms—Dome Shape; Rectangular; Flat Roof; Deformation; Bending Moment; Shear Force; Lateral Load; Transverse Load.
I. INTRODUCTION Most earthquake-related deaths are caused not directly by an earthquake but due to collapse of structures. A structure collapses because of faulty construction, improper design calculation or impractical loading concept. Failure is also due to extent of response of a structure under a seismic loading. It is now observed that a building of moderate height collapses whereas a high rise building does not show any distress although both the buildings are located in the same place. This is because of resonance of frequencies of soil column layer and the building. Since long people are trying to make their buildings earthquake resistant. As a result, various earthquake resistant practices are being followed in different regions of the world. Methods like base isolation [1] and friction damped bracing systems [2] have been studied. Traditionally, the focus of the seismic resistant design of buildings has been collapse prevention with the ultimate aim of saving the invaluable human lives. However, these buildings take enough damage that makes them unfit for further use after an earthquake. The new goal is to build structures that not only avoid collapse, but take no damage when an earthquake strikes and are ready for immediate occupancy with little or no economic loss. Following this philosophy, the present study aimed to find out whether a structure with dome shaped roof would be more resistant to © 2012 ACEE DOI: 02.AETACE.2012.3. 12
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