Advanced Materials Research Vols. 163-167

Abstract: Proper content of titanium, microalloying in steel ZG200-400 smelted in intermediate frequency induction furnace, could effectively increase the volume of concentrated shrinkage cavity, and restrain the forming of shrinkage porosity. The concentrated shrinkage cavity was analyzed quantitatively by stuffing wet gluten and draining water method. The maximal cavity arrived at 0.18wt.% titanium microalloying. By scanning electron microscope (SEM) and energy disperse spectroscope (EDS) analysis, it was found that TiC, acting as heterogeneous nuclei, could refine the structure grains, diminish the strong dendrites, and increase the fluidity and feeding capacity of steel liquid. However, overdoes titanium microalloying easily caused mass nitrides or oxides, which kept solid phases with high meting point in metal liquid to increase its viscosity, decrease the fluidity and enlarged the composition supercooling. So the metal liquid, with poor feeding, left more shrinkage porosity, less concentrated shrinkage cavity in solidification.

Abstract: The computational model of numerical analysis of the planar pre-stressed steel trusses subjected to fire load is established according with main consideration to the response mechanism of the structure in fire. For the convenience of application, the EC3 constitutive model of the steel materials in fire is simplified with series expansion, and the suggested formula for each stage are unified. The fire behavior of the planar pre-stressed tubular steel trusses in which two cables are set is analyzed with the model presented here and the effect law of different factors on the bearing capacity of the structures in fire are discussed. It is concluded that fire response of the pre-stressed steel trusses is affected obviously by the different model of material under the same fire conditions, and critical temperature of the structure in fire increases with strength grade of steel material, which means that choice of the proper material model used for analysis of behavior of the steel structure under fire is very important and need to be studied further.

Abstract: Kinematically indeterminate structure is a type of special structure that consists of internal mechanism. This paper mainly proposes a unified approach for the motion analysis of kinematically indeterminate structure based on inextensional mechanism, which is achieved by the equilibrium matrix SVD. The physical meaning of inextensional mechanism is studied and the detail procedure for the simulation algorithm is presented. Further more, it is applied to trace the motion paths of unfolding process of an expanded octahedron tensegrity unit and the deployment of radial retractable structure. Simulation results show the validation and efficiency of the presented method.

Abstract: This paper summarizes the regulations about steel frame second-order effect of some design code in the world, and find out a critical factor of controlling second-order effect. The second-order effects of staggered truss were studied systematically by using ETABS program, and put forward design proposals the second-order effects of internal force and displacement, the simplified formula on second-order effect magnification factor of displacement was given.

Abstract: This paper deals with the mechanical property of a new designed bridge pavement of box girder bridges. Our concerning is the stress change at the interface between the steel deck and the pavement due to the vehicle wheel loads, which can be considered as a kind of concentration force to the pavement. The finite element method is utilized to analyze the present problem. Several simulations are carried out by taking account of different positions of the vehicle wheels in order to simulate the interface stress change under real conditions. The present results can be a helpful reference for steel-deck pavement design.

Abstract: Stability design for compressive web members of tubular structure could be simplified as determination of effective length of compressive web members. There were no design provisions for effective length of compressive web members in tubular truss in the current design code of steel structure (GB50017-2003). Based on previous research achievements, parameter analyses on compressive web members in tubular truss with simple joints were performed using finite element software, in which diameter ratios and wall thickness ratios of web members to chord members as well as different construction styles were considered. After analyzing 3 series, sum to 42 FEM model, the results indicates that stiffness ratio of web members to chord members has a significant effect on effective length of compressive web members, thus increasing width ratio of chord members to web members could decrease effective length of compressive web members; the effective length of compressive web member in circular tube truss is suitable to be 0.75 in-plane and out-plane, and 0.8 for the mixed truss of circular and square tube.

Abstract: Construction control is the key technique for cable dome. During the actual engineering, however, it is difficult to ensure no difference between the real prestress distribution and the designed value due to existed construction errors. The practical problem for cable dome construction is to determine how much is allowable errors limit. To solve the problem, sensitivity analysis of manufacture errors of bearing and cable length are carried out in this paper. The random errors are simulated by Monte Carlo method. In a numerical model of cable dome with the diameter of 62m, the sensitivity of effect of bearing and cable length manufacture errors on structural performance is analyzed. Numerical results show that the manufacture errors of radial bearing, hoop cable 2, ridge cable 3, diagonal cable 3 and hoop cable 1 should be strictly controlled. Besides, the maximum allowable errors are proposed referring to the domestic existing specifications.

Abstract: In the present paper the whole structure and the construction process of SPZ1300/48 gantry is introduced and the stability of the gantry under lifting process and transition process is also analyzed by some reliable finite element method software. By the analysis of the overall stability of the structure, taking into account the bad weather (strong winds) in the region, in the case of lifting process and after the segments placed, the optimal lifting sequence of the beam segments on account of the stability of the structure itself is obtained. By this way a useful sample for analysis of similar systems is provided, and then a technical foundation is established for bridge constructions by segmental assembling method for larger span or tonnage.

Abstract: The elastic and plastic characteristics of the Y-joint of frame-core tube structures with steel pipe column and steel pipe outrigger truss is studied in this paper. The finite-element method is adopted in the numerical study. To avoid the damage of the joint, controlling the relatively convex-concave deformation of the column wall through adding internal stiffener plate is discussed. Through the comparison of numerical study of the Y-joint with different shape of stiffener plate, a feasible design of the Y-joint is given.

Abstract: A certain natatorium is selected as the object for the corrosion researches on common carbon steel which has been used in the corrosive environments for 20 years. Bearing and deformation capacities are calculated to simulate corrosion by elastic and elasto-plastic finite elements analysis with ANSYS. The result is shown that corrosion condition should be considerable to the space truss with thin wall thickness in the severely corrosive environments.