Study On Design Method System And Practice Software Of Superstructure-Foundation-Soil Interaction

It has been recognized that the theory of superstructure-foundation-soil interaction is a well-known major branch of geotechnical engineering. However, the geotechnical engineer can get still no any more benefit using this theory in design and practice. On the contrary, some risks may be suffered due to the incomplete design theory and methodIt is the first time in China that the design method ofsuperstructure-foundation-soil interaction is taken as a system to study. This dissertation, based on the author’s experiences in foundation design, software development and applications for many years, attempts to enrich the design theory considering interaction between superstructure and foundation supplement the present design methods and develop the corresponding compute aid design programme for providing the effective guidance and service to designers.This dissertation includes three parts as follows:Part 1Study on Theory of Foundation Design Considering Superstructure-Foundation-Soil Interaction1. An excess use of steel in foundation design causes a huge waste of funds and resources. Many field experimental results have been shown that the measured value of stresses of steel bar in foundation slab is much less than the design value. The conclusion has been obtained by the detailed analysis on various possible influencing factors that the basic reason is the unreasonable design and calculated methods in which the main influencing factor lies on if considering the interaction or not.While the height of a high-rise building is close to or over the length and width of foundation, the whole performance will approach to that in deep beam. The calculated and analyzed results have shown that the stress of frame beam and slab in each floor is generated by interaction of whole and local buckling. From this reason, a method called simply deep beam is presented to calculate the stress of steel bar in foundation slab and this method can reduce the actual area of steel. For checking its feasibility the comparison between calculated and measured results has been made in some engineering cases.2. Based on the quantitative analysis for 5 engineering cases with field experiment data and 2 calculation examples, the influence range of superstructure stiffness on foundation deformation, foundation pressure and the stress of steel bar in foundation slab can be obtained when the building is constructed by frame-shear, frame, shear wall or tube structure. It is confirmed that there is a critical height (number of floors) for the increase of superstructure stiffness. The relationship between superstructure stiffness and number of floors can objectively reflects the process of superstructure stiffnessDifferential deformation, maximum horizontal stress at bottom and differential horizontal stress in the simply supported deep beam obviously change with number of floors. There are three turning points along the deformation-number of floors curve. For practical convenience to reflect the consistency of the working performance between high-rise building and deep beam, H=0.3L、0.5L、0.7L (H is the structural height above foundation slab and L is the foundation length) can be taken as the critical height for influence range of stiffness of shear wall, frame and frame structure. Future study on tube structure and other form of high-rise structure is needed. Currently, the height within influence range of tube structure with the foundational length less than 60 m would be preliminarily fixed as H=1.5～2.0L, while H=1.0～1.5L for those with the foundational length more than 60 m in order to study.To determine the influence range of superstructure stiffness can not only provide a better understanding on the mechanism of interaction, but also reduce the overall calculating workload. 3. Based on the limited geological data provided by an engineering geological survey report, a 3D geological model can be constructed to create the basic condition for the overall calculation of superstructure-foundation-soil interaction. In this paper, using the continuous processing method along the horizontal and vertical direction, the solid body of the whole site can be divided into continuous triangular prisms. Thus, the linear increment can be used to obtain the physical and mechanical indices of solid body at any position within semi-infinite space automatically and also construct a standard drilling hole automatically.Part 2 Study on Method System of Foundation Design Considering Superstructure-Foundation-Soil Interaction1.This paper systematically states the finite element overall design method considering superstructure-foundation-soB interaction, complements some important contents and proposes a concrete method to deal with the inconsistency of load combination between interior force and deformation of foundation in present design code. Thus, using this method presented in this paper the interior force and deformation in foundation corresponding to match design code can be calculated.2.This paper proposes a simple method for considering superstructure-foundation-soil interaction in which the simplified deep beam method is used to calculate the whole buckling and the improved inverted beam method to calculate the local buckling. Furthermore, the general design methods for foundation components is also illustrated. It should be noted that the other proposal can automatically identify the inner tube area of reinforced concrete and help computer automatically calculate the punching and sheering bearing capacity of foundation slab to the inner tube.3.The focus of primary study on design of foundation construction drawing design is how to improve the intelligence and efficiency of computer aided design in order to reduce the designers’ labor. This section has an unique perspective at three aspects of 1. integrating and selecting steel of foundation beam, 2.method of reinforcement of whole foundation plane and 3.automatic layout on pattern of foundation beam for construction drawing.Part 3 Study on Aided Design Software of Foundation Considering Superstructure-Foundation-Soil Interaction1. This part systematically illustrates the contents and functions required to set up the calculation model and analyze the features and data interface of the present domestic corresponding softwares, which is for engineers’ reference.2. A high-speed iterative method is presented to increase the efficiency of overall analysis on superstructure-foundation-soil interaction, which can eliminate the inconvenience caused by full rank of foundation stiffness matrix and asymmetry. Besides, some illustrations are given for the parameters influencing the calculating results.3. The visualization of calculating results and parameterized drawing and so on in post treatment are also studied.In one word, this dissertation provides the theory of foundation design, method system of foundation design and aided design software of foundation considering superstructure-foundation-soil interaction in order to be used in engineering practice in the near future.