Comparison of the Behaviour of Curved and Straight Types of Steel Shell Roof Structures

ABSTRACT: In this research, the straight and curved models of the steel shell roof with different plates were analysed, designed and the results were compared with one another. Through this exercise it is aimed at achieving an ideal shell roof structure which could cover a larger surface. Therefore, three types of shell roofs were considered duopitch, cylindrical and dome and the main objective was to compare the straight and curved model of the shells. According to the findings of the literature review, this is the first time for such comparison to be carried out among the basic types (duopitch, cylindrical, dome) of shell roof structure. In addition to the advantage of covering large openings the shell roof structures also use the least materials to do this. Most of its resistance against the forces imposed on it is due to its curved surface. It is this particular characteristic of the shell structures that has been attracting architects and civil engineers more in the recent years. This research shows how effective the curved surfaced shell roof can be with different angles in helping the structure to resistance its self weight and applied loads. Moreover, it also indicates under which conditions a particular structure can be more reliable. This kind of shell roof is not common in all shapes and each model needs special characteristics. When all the comparisons were made, an optimal structure with the largest span of shell roof and resistance to loads was obtained. In this research, three different angles were used in three shell roof models in simple and general conditions and the results were compared in order that a structure with ideal condition can be obtained in future while basic conditions also need to be understood. For each shell roof type, three plates were considered for analyses and designed. A metal box with either 5cm or 7cm I-section edges, each box has 0.5m length and breadth and I-section edges with either 0.05m or 0.07m height and 0.003m thickness. A metal box with L-section edges, each box has 0.5m length and breadth and L section edge with 0.05m height and 0.02m edge and 0.03m thicknesses. The comparison between these plates indicates the load carrying capacity and span capability of the structures. When all different shell roof types are able to cover the same opening, then it is these plates which determine the weight and the amount of stresses in the structure. The research showed that it is necessary and important to consider the maximum possible loads these structures could carry and also to find out the maximum span and the loads that these types of structures can tolerate. This kind of design is very economic in shell structures and has the capability of replacement and frequent usage in different areas while the other structures do not have this ability. Key words: Shell, Metal box, Steel structure, Curved model, Straight model. ……………………………………………………………………………………………………………………………………………………………………………………………………………………