High-rise diagrid tube structures are widely used in high-rise buildings because of their strong lateral stiffness and flexible arrangement of plane layout. The lateral stiffness of rectangular diagrid tube structures is studied by many researchers, but it seldom attracts attention for arbitrary polygonal ones. Therefore, it is necessary to propose a calculation model for lateral stiffness of arbitrary polygonal diagrid tube structures. First, the basic concept of modular method is defined. Assuming that diagonals are only subjected to axial force, a calculation model of lateral stiffness of arbitrary polygonal diagrid tube structures is presented. The lateral displacements of structures are calculated by modular method. Then the accuracy of modular method and calculation model of lateral stiffness are verified by finite element method. Intersection law of structural lateral displacement curves is achieved. Taking the top displacement of structures as the reference index and based on the principle of equivalent material, diagonal angle optimization method is proposed, whose rationality is validated by finite element method. Based on the design method of top displacement control, preliminary design method of cross section of diagonals is suggested. Results in this paper are expected to provide a theoretical reference for preliminary engineering design. KEYWORDS cross-sectional design method, diagrid structure, lateral displacement, lateral stiffness, modular method, optimization of diagonal angle

IntroductionWest tower in Guangzhou Zhujiang new city is a new type of tube structure system as shown in Fig. 1 and Fig. 2, which has total floor area of 247000 square meters. Outer tube of this structure consists of diagonal members which are concretefilled steel tube columns, while inner tube consists of shear walls and steel frames. Shear walls of inner tube are cancelled above 67th floor and replaced by steel frames. Elevation for the underground fourth floors is -18.7meters, and elevation for the top of structure is 432 meters. Because the height of West tower is higher than code limit value and shear walls of inner tube change into oblique steel frame at 67th floor, which leads to vertical irregular arrangement of the structure. Thus, West tower belongs to a complex super high-rise structure [1] .At present, researches on high-rise diagrid structures are still not very mature. Moon [2] proposed preliminary design method for diagonal members. Han [3] researched deflection, stress and failure mode of diagonal nodes by conducting model test of concrete filled steel tubular joint. Tian [4] conducted a shaking table test on West tower by using micro-concrete and brass tube, and destructed form of West tower was obtained. Kim [5] obtained hysteresis curve of steel diagonal nodes by experiment. Kim [6] evaluated the seismic performance of diagrid structure by finite element method.Structural type of diagrid structure makes the force-mechanism become complicated, and it also makes mechanical property calculation of diagrid structure difficult. Therefore, it is necessary to carry out further experimental study on seismic performance of whole structure. For this reason, a shaking table test of a plexiglas model in scale 1:80 was carried out to study the seismic performance of the structure. In further, an elastic time-history analysis by finite element software was carried out on the structure, the mechanical characteristics and weak parts of the diagrid tube structure were obtained by comparing the results of analysis and shaking table test. In this paper, the research also expects to provide the basis for the reasonable design of diagrid tube structure.

A large number of over-track buildings have been designed in metropolis during the recent decades for adapting to rapid urbanization and saving land resources. However, the over-track buildings are potentially affected by train-induced vibration that may cause discomfort or health problem for residents, which in turn needs to be carefully evaluated. In this study, the responses of a high-rise over-track building with three different transfer types have been investigated using the recorded threedimensional accelerations from in-situ tests. By performing time history analyses, the vibration responses of the fixed structure, traditional rubber bearing (TrRB) isolated, and thick-layer rubber bearing (ThRB) isolated structures are analyzed and evaluated, respectively. The results show that the most evident vibration is in the vertical direction with vibration energy mainly concentrated among the high frequencies. Thereafter, the effects of vibration control by using different isolation technologies are compared. It is demonstrated that the abilities to isolate vertical train-induced vibration could be enhanced by using ThRB while the horizontal isolation performance is still guaranteed. Then the reason for the variation of vibration amplitude along the building height is discussed. This research enriches the train-induced vibration database and exemplifies the vibration mitigation control and design for over-track buildings.

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