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Tang Y.,Key Laboratory of Geotechnical and Underground Engineering | Zhao X.,Tongji University
KSCE Journal of Civil Engineering | Year: 2015

Although certain measurements regarding super-tall buildings constructed using the top-down method have been published, new advances in top-down construction have been developed with the construction of super-tall buildings in China. This paper presents the theory of soil-structure interactions in pile foundations and extends it to the top-down construction method. Based on this theory, the forces and the deformation of the diaphragm wall, slab and soldier piles at various stages of construction can be computed. Two typical tall buildings of 60 and 37 stories with deeply embedded 4-level and 5-level basements located in Shanghai were used as case studies of the vertical displacements of their diaphragm walls and soldier piles, the deflections of the diaphragm walls, the earth pressures, and the rebar stresses during top-down construction. The values measured in the field agree well with the predicted values from soilstructure interactions theory and statistical-empirical formulas. Two additional super-tall buildings of 101 and 121 stories, in which the 4- level and 5-level basements and the main buildings are round, are discussed regarding their unique deformational characteristics. In addition, the diaphragm wall can serve a load-sharing function. These engineering case studies, including the comprehensive predictions of deformation based on field tests and estimates using statistical formulas, can improve tall building design. © 2015 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg Source

Jiang M.-J.,Tongji University | Jiang M.-J.,Key Laboratory of Geotechnical and Underground Engineering | Zhang W.-C.,Tongji University | Zhang W.-C.,University of Western Australia
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2014

The Tait equation of state for liquid is implemented into the N-S equations-based computational fluid dynamics (CFD). This method is then coupled with the distinct element method (DEM) so as to establish CFD-DEM codes to simulate the porous media with weakly compressive fluid. Firstly, the governing equations for the coupled CFD-DEM method are introduced, including equations for fluid-particle interaction forces, N-S equations, Tait equation of state for liquid and motion equations for particle system. Then, a coupled CFD-DEM scheme is implemented into the DEM commercial software PFC2D. Finally, two benchmarking examples, namely, single particle free settling and one-dimensional consolidation, are used to validate the coupled CFD-DEM method. The results show that in the CFD-DEM simulations the free settling velocity of single particle meets the Stokes's solution, and the excess pore pressure and degree of consolidation at different values of Tv are close to those of the Terzaghi's consolidation theory. Source

Zhang Q.,Tongji University | Shen M.,Tongji University | Ding W.,Tongji University | Ding W.,Key Laboratory of Geotechnical and Underground Engineering | Clark C.,Louisiana State University
Journal of Geophysics and Engineering | Year: 2012

The study of creep properties of the rock mass structural plane is of great importance in solving practical problems in rock mass mechanics. The time-dependent deformation and long-term strength of the rock mass are controlled significantly by the creep mechanical behaviour of the structural plane, and the study of creep properties of the rock mass structural plane is an important area in rock mass deformation. This paper presents fundamental research on the mechanical properties of regular jugged discontinuities under various normal stresses, and focuses on the creep property of the structural plane with various slope angles under different normal stress through shear creep tests of the structural plane under shear stress. According to test results, the shear creep property of the structural plane is described and the creep velocity and long-term strength of the structural plane during shear creep is also investigated. Finally, an empirical formula is established to evaluate the shear strength of the discontinuity and a modified Burger model proposed to represent the shear deformation property during creep. © 2012 Nanjing Geophysical Research Institute. Source

Chen Z.Y.,Tongji University | Chen Z.Y.,Key Laboratory of Geotechnical and Underground Engineering | Shen Z.Y.,Tongji University
Advanced Steel Construction | Year: 2010

Tests were conducted on six L-shaped concrete-filled steel stub columns (CFSSC) and one L-shaped steel hollow column. The nonlinear damage process and the failure mode of the specimens were described. The influences of structural parameters on the axial bearing capacity of L-shaped CFSSCs were investigated. These structural parameters included the width-to-thickness ratio of the steel plate, with or without stiffeners, and the limb length. The experimental results indicated that the confined effect of the steel tube on the infilled concrete was more distinct for an L-shaped CFSSC with a short limb than one with a long limb. For an L-shaped CFSSC with a short limb, the stiffeners may improve the ductility of the specimens to the extent of 1.5 times although they were less effective in improving the bearing capacity. On the other hand, the stiffeners were ineffective in both improving bearing capacity and ductility of the L-shaped CFSSC with a long limb. Source

Yuan Y.,Key Laboratory of Geotechnical and Underground Engineering | Yuan Y.,Tongji University | Chen Z.,Key Laboratory of Geotechnical and Underground Engineering | Chen Z.,Tongji University
Journal of Earthquake and Tsunami | Year: 2010

The large-scale construction of underground structures prompts researchers and engineers to reconsider seismic safety of existing and new underground structures against future strong earthquakes. This paper attempts to assess the current state-of-the-art in experimental and analytical researches on large-scale urban underground buildings. Three key issues, which need to be urgently resolved in numerical computation, are also discussed. Finally, necessity and applicability of damage control techniques are explored. The techniques, which are proved to be effective in surface buildings, are expected to update seismic performances of underground structures. © 2010 World Scientific Publishing Company. Source

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