Analysis And Design Of Long Span Grid Structure Of A Gymnasium In Chongqing

With the development of the economy and constant progress of science and technology, application of grid structures in buildings is more and more extensive, Grid structures belong to statically undetermined structure so it's very difficult to analyze its mechanical performance, entirety and stability. Numerous designer and researcher in and abroad had made a large number of researching and analysis and investigations on this field, and made a series of achievements correspondingly. But on the respect of the vibration characteristic and the combination the controlling internal force of trusses for long-span structures, the analysis and researching are seldom, so it's necessary to do much further research and analysis in the field of long-span structures and it would be meaningful, the conclusions can be used as references for engineering practice. This paper analyzes the characters of grid structures, the choices of grid structures form, introduces principia of structural calculation and the constitution of joint, and claries the foundational theory of grid analysis. And it also summarizes the current situation of the design of the long-scale grid. As to the design of the long-span grid of a gym, according to the demand of architectural modeling, there are two models of structural forms, square pyramid space grid and the square pyramid that had been deleted some trusses, in the matter of joints use of each model, the design adopt bolt-sphere joint and welding-sphere joint. When it comes to the structural analysis, MSTCAD and SAP2000 have been used to analyze structural internal force and the vibration characteristic of grid. The paper also compares the mechanical behavior and the economy of each model, and induces the combination of controlling internal force of trusses in various earthquake intensity-category regions.Based on the comparison and analysis, the paper gives some conclusions as following:Compare with space pyramid grid, the stiffness of the square pyramid grid which had been deleted some trusses reduces dramatically, and the difference of the mechanical performance are very large, its integrality and distortional ability are poor, and meanwhile the distinction of the amount of steel use can be ignored.The foundational period of the pyramid grid and the pyramid grid that had deleted some trusses are close to each other, and the former 9 intrinsic period of the pyramid grid that had deleted some trusses are longer than the pyramid. The vibration modes of the pyramid grid and the pyramid grid that had deleted some trusses mainly are vertical, and 3~9 vibration modes of the pyramid grid that have deleted some trusses are the parts that had deleted the trusses' vibrating, so under the high vibration modes this model is easy to lead to local damage, and bad for seismic performance.In the regions of 6 and 7 fortification intensity, the mainly controlling internal forces of the trusses of grid are the work case combinations of 1.2 multiply dead load plus 1.4 multiply live load, and 1.2 multiply and 1.4 multiply wind load. In the regions of 8 and 9earthquake intensity-category, the controlling work case combination is 1.2 multiply dead load and 1.0 multiply earthquake load.The form of joint plays a negligible role in structural mechanical behavior, so when the form of joint chosen, the constructional technics should be weight on necessarily, generally speaking, the bolt sphere joint often be used in practice for its conveniences and reliability of quality.