Advanced Materials Research Vols. 243-249

Abstract: Through the analysis of the transmission mechanism—distribution beam for large section (side length>800mm) concrete-filled rectangular steel tube column by the theory of elastic foundation beam we can obtain, percentage of load-carrying capacity shared by concreteis related with vertical spring stiffness of the steel tube, rotational spring stiffness of the steel tube, the vertical spring stiffness of the core concreteand stiffness of the distribution beam. Through analysis of the relationship among percentage of load-carrying capacity shared by concreteand the impact factors, we can identify the main factors that affect the percentage of load-carrying capacity shared by concrete, to control the design of the distribution beam.

Abstract: According to the thought of beam string structure, pre-stressing structure was presented that it was joined by rigid grid and flexible cable by pole support. It was grid string branch structure. A calculation model of string branch grid was founded. Static and dynamic characteristics of the structure that it was acted by different pre-stress value were analyzed. Through the analysis, the structure displacement and internal forces of rod are improved obviously depending on pre-stress value. The pre-stress value is larger, structure displacement and internal forces of rod are lower. Natural vibration characteristics of the structure are almost not changing, while pre-stress value is changing. When the structure is time history analysis, its response curve accords with general law of structural vibration. Node displacement response of up and bottom chord nodes are not occurred retardation effect.

Abstract: The optimization methodology of the steel-concrete composite beam was proposed in this paper. The objective function is the cost of the composite beams, and the design variables are the geometry parameters, including height and width of the concrete deck, as well as thickness of the steel flange and web. The constraint conditions are main requirements stated in Chinese code for the design of composite beam, reasonable calculating theories and indispensable constructions, as well as some mature and consistent conclusions confirmed by experimental studies. Stiffness reduction coefficient is used to consider the effect of bond-slip effect between concrete and steel when calculating the beam deformation. The optimization for composite beam under uniform loads is given as a demonstration example finally. The methodology proposed in this paper should be useful for obtaining the solution of this kind of optimization problem.

Abstract: There are many factors influencing the bearing capacity of spatial joint, whose load-carrying capacity is also more complicated. In this paper, the finite element method is adopted for the tubular joint of TX-type square steel tube to explore the influences on the ultimate bearing capacity resulting from the axial stress of main tube and the loading ratio J_AA. The analytical results show that: for the joint with small β, the pressure of main tube will reduce the joint strength, while the appropriate tension is beneficial, but too large tension will lower the joint strength. The loading ratio JAA has significant influences on the joint, and when the ratio is positive, the outer-planar branch plays a very good role in the stiffening effect of the joint.

Abstract: This paper aims to evaluate the fatigue life of an existing railway riveted steel bridge. Based on the measured train load information, the current load spectrum of the bridge is obtained, and the stress histories and stress spectrum of main members of the bridge are achieved using FE model and rain-flow counting method. The fatigue life of the bridge using traditional method is evaluated. At the same time, the finite element (FE) model of riveted component is established and the stress intensity factor of crack tip is calculated. The fatigue crack is simulated on the basis of linear elastic fracture mechanics (LEFM), and the fatigue life of the main members is also evaluated based on the damage tolerance analysis method. The evaluated results of fatigue life show that the fatigue remaining life of the bridge is very long due to the lower live load stress level.

Abstract: A major difficulty in reliability analysis of reinforced concrete (RC) columns subjected to both axial compression and bending moments is the interaction between strength of bending and axial compression. In particular, the limit state function cannot be explicitly expressed due to this interaction. This paper analyzes the correlation between load effects. Given the calibration point, a mathematical expression for the load correlation, r_MN, in terms of eccentricity of dead load and live load, e_G and e_Q, is established, which physically clarifies the relationship of r_MN with load path. Given the ratio of eccentricity k = e_G/e_Q and the ratio of load effects r, the reliability analysis for RC columns with considering the correlation between load effects can be analyzed by using the correlation relationship proposed in this study and FORM method. This study provides an effective and practical approach to the reliability analysis.

Abstract: 3D Integer models of steel portal frames are made to analyze the influence of end-plate bolted connections on internal force and displacement of frames by using finite element method. The results show that end-plate bolted connections are semi-rigid connections, and the flexibility of the connections affects the behavior of the frames, and their influences can not be ignored in the steel portal frames design and analysis.

Abstract: With the application of high strength concrete and rebar, the influence of concrete strength on cracking width of reinforced concrete beam with high strength rebar is becoming more and more important. To investigate the effect of concrete strength on cracking width of reinforced concrete beam with high strength rebar, the experiment including 6 simply supported T-beams with high-strength rebar and 2 beams with ordinary-strength rebar have been made. Then the relevant specifications advised in Code for Design of Concreter Structure (GB50010-2002) are revised according to the experiment results so as to considering the influence of concrete on cracking width. A new cracking width method considering the influence of concrete strength on cracking width for reinforced concrete beam with high strength rebar is proposed. Finally, the comparisons between predictions and experiment results have been conducted, which shown that the proposed new cracking width method agreed with experiment results well.

Abstract: With the increase of the height, the lateral stiffness of high-rise buildings decreased. The high and flexible structures would have large movement when they are suffered lateral forces arising from earthquakes and winds. Compared with the ordinary high-rise buildings, the dynamic characteristics of the connected tall building will be changed by the connection; its seismic response and background of excitation are more complicated. Various finite element models with different connection location are established in order to find out the change of dynamic characteristics caused by the connection. According to modal analysis, the natural periods and mode shapes of different models are obtained. By utilizing the time history analysis method, El Centro earthquake wave was inputted, the seismic responses are obtained. The difference of results and summarized variation of dynamic characteristics with connection factors are analyzed. The results show that structural natural period and mode shape will be changed when the connection position changing. Under the seismic excitation, the change of location has little effect on the displacement time history and the maximum displacement, but the influences to the acceleration time history and the maximum acceleration value are obvious.

Abstract: An experiment of sixteen frame column underpinning joints of frame structure moving was introduced, the experiment sample failure phenomena and failure type was obtained. The type was like “deep beam” failure type-“tension bar arch”, and the last failure place occurred on the interface of column and beam. Then, the underpinning joint stress mechanism and failure mode was determined based on the experiment’s conclusion. In addition, the failure course of joint was divided two stages which were before and after interface punching slip by theoretical analysis, for the stage before interface punching slip a space “tension-bar-arch” mechanical model was presented for the underpinning joint, then theoretical bearing capacity equation for this underpinning joint were obtained. At the same time, for the stage of interface after punching slip, the theory of interface shear was put into the analysis of joint, then interface bearing capacity equation was obtained for this stage. At last the height equation was obtained by the analysis of the stage of after interface slip.