Key Engineering Materials Vols. 400-402

Abstract: Combined with the respective advantages in S-R(Sway-Rocking) impedance concept and finite-element method, a simplified 3D structural dynamic FEM considering composite pile-group-soil effects is presented. The structural members including piles are modeled by spacial beam or shell elements, and raft-base is divided into thick-shell elements with its spring-dashpot boundary coefficient obtained by impedance backcalculated. The mass-spring elements for soil between piles are set to simulate vertical, horizontal pile-group effects by strata-equivalent approach. The soil beside composite body is separated into near-field and far-field parts. The former is modeled by nonlinear spring-dashpot elements based on Winkler’s hypothesis, while the latter is modeled by a series of linear mass-spring-dashpots. With the effects of boundary track forces and energy radiation, the presented model enables researchers to conduct the time-domain nonlinear analysis in a relatively simple manner which avoids sophisticated boundary method and solid-element mesh bringing with tremendous computational cost. The seismic effect on dynamic interaction of pile-soil-complicated structures would be efficiently annotated from two structural engineering and geotechnical engineering aspects and the numerical calculation effort would be drastically decreased too. The complete procedure is mainly performed using the parametric design language assembled in the Finite Element Code Ansys. With the dynamic analysis of foundation and superstructure for a pile-supported 15-storey building, the influence of the participant effect on structural dynamic response will be depicted by various dynamic parameters of pile-soil-raft foundation in detail. Not only do the results have an agreement with some conclusions drawn by the general interaction theory, but also certain of phenomena which would be disagree with that by general analysis is involved. Even with the finite-element meshes for 68 piles, the time-history analysis procedure for PGSS (Pile-Group-Soil-Superstructure) system and the qualitative evaluation with various SSI parameters can be also fulfilled efficiently and rapidly by presented means. These results may be of help to the designers to quickly assess the significance of interaction effect for the high-rise buildings resting on any type or layout of pile-group foundation.

Abstract: Residential houses and civil buildings in China were mainly low-rise buildings before 1980s. With the rapid development of urban construction, urban land became more and more scarce. Thus in recent years, it becomes increasingly popular nationwide to add more stories to existing building for its particular techno-economy advantages. Adding-storey plays an important role in mitigating the pressure of demand for more building sites, improving the living condition，and accelerating the modernization progress of cities’ shabby zones. In this paper, a brief review was presented on the evolution, status-quo and trends of the adding-storey of existing buildings in China, and three new adding-storey methods using passive control technology were introduced, which can be used for peers' reference.

Abstract: Based on tension-compression and bending equivalences, an equivalent single material plate is formed to substitute bridge deck of composite girder with steel fiber reinforced concrete (SFRC) and steel. Thickness and elastic modulus of the equivalent plate are then formulated. After three dimensional finite-element analyses of the bridge deck, in terms of shell element membrane effect and girder flexion-torsion theory, combined with compatibility of deformation, single material shell element stress is restored to stresses on SFRC plate and steel plate separately; shear force distribution on shear keys between SFRC and steel is analyzed.

Abstract: In practical engineering, we often encounter designs of variable cross-section or compound section skew girder bridge. While in many bibliographies, uniform cross-section of the concrete beams studying was carried out, but few of variable cross-section concrete beams were in-depth studied. Based on analyzing the mechanical behavior of variable cross-section beam skew girder bridge, the semi-analytic solution of variable cross-section beam skew girder bridges were provided in this paper. With this method developed a planar computation program to resolve the calculation problems of skew girder bridge, a more convenient way will be brought up for designers in calculation.

Abstract: Incremental launching method is a construction technology for prestressed concrete continuous bridges widely used in China. In the incremental launching method, the superstructure of a bridge is erected from one side of bridge longitudinally to the opposite bank. Compared with other technology for bridge erection methods, it may reduce the cost of labor, shorten the construction period and save the assembly yard. So it is a competitive construction method for medium-span prestressed concrete continuous bridges. A large number of skew bridges will be built especially at mountain area, so it is very necessary to research on incrementally launching method for skew bridges. The objective of the study presented in this paper is to introduce the method used in the Lishui Bridge in Zhangjiajie city of China.

Abstract: The static behavior of a reinforced concrete trough railway bridge is analyzed by finite element method. The influences of load distribution fashion, supporting width of the bearings and the additional support beneath the girder are investigated; and the spatial effect of the stress distribution is studied as well. To confirm the analysis accuracy, the results are calibrated with the field load test results. It is found that the influence of load distribution fashion is minor and negligible, while those of supporting width and additional support are not negligible; and the spatial effect is significant.

Abstract: The layered soil model is used to simulate the nonlinear performances of the layered soil in this paper. Using the shear-displacement method, the flexibility coefficients of the pile-pile and the pile-soil are deduced based on the interaction mechanism of the pile-pile and the pile-soil in the layered soil. After that, the stiffness matrix of the pile-soil system can be established. Using coupling method presented in this paper, the interaction equation of superstructure-pile-raft-soil system is formulated. The interaction equations are used to analyze the reaction force on the pile head and the displacement characteristics of the raft of the piled-raft foundation in the layered soil and its practicality is excellent.

Abstract: Using the nonlinear analysis method and program of the interaction of superstructure- pile-raft-soil system in layered soil in the state of the previous literature, the reaction force on the pile head and the displacement characteristics of raft of the piled-raft foundation are analysed when the thickness of the raft, the spacing of the piles, the length and the diameter of the pile are changed. Some quantitative data and qualitative conclusions are obtained in this paper.

Abstract: A networked structural laboratories system for seismic simulation of structures is presented. It consists of an independent network based communication platform (NCP) and various applications based on NCP. The NCP was developed based on client/server concept along with a proposed data model and communication protocols. It is capable of transferring control and feedback data among computers connected by Internet that is a hierarchical network with ubiquitous deployment of middleboxes, such as firewalls and network address translators. Communication speed tests were conducted in various network environments. Applications for hybrid dynamic test of bridge and building structures have been developed and remote hybrid tests of structures were carried out among the Hunan University, the Harbin Institute of Technology, and the Tsinghua University.

Abstract: Concrete-filled special-shaped (L-shaped, T-shaped, and cross-shaped, and etc.) steel tube column is a type of member in which concrete is poured into special-shaped steel tube so that steel and concrete support loads together. It improves the seismic behaviors of reinforced concrete special-shaped columns due to the better confining effects provided by the steel tube. A test research on the seismic behaviors of one concrete-filled T-shaped steel tube column with pseudo static method is presented and the load-displacement curve and skeleton curve are provided. Series of steel bar stiffeners were welded onto the steel tube in order to postpone the buckling of steel tube and to enhance confining effects. A numerical analysis program was developed using a fiber-based method. The constitutive model of concrete employed the modified Mander model, and that of steel employed a bi-linear model considering the Bausinger effect. The numerical analysis program was verified by the test results and parametric analysis was carried out, in which the influences of the ratio of axial compression stress to strength, steel tube thickness and concrete strength were mainly discussed. The following conclusions are obtained: with the increase of the ratio of axial compression stress to strength, the bearing capacity of member increases and the energy dissipation capacity improve, while the ductility deteriorates. With the increase of steel tube thickness, the initial rigidity, bearing capacity, ductility and energy dissipation capacity improves simultaneously. With the increase of concrete strength, the bearing capacity increases, the energy dissipation capacity improves, while the ductility deteriorates.