Applied Mechanics and Materials Vols. 166-169

Abstract: Support vector machine is applied to springback forecasting for steel structure in the paper. In the steel structure, pressure-pad-force, friction coefficient and die filleted corner have a certain influence on springback amount.We employ BP neural network to compare with support vector machine to show the superiority of support vector machine in this study. Finally,we give the comparison of the prediction error of springback for steel structure between support vector machine and BP neural network. Evidently,the springback prediction for steel structure of support vector machine is better than that of BP neural network.

Abstract: The health monitoring and diagnosis of the major engineering structure is increasingly extensive attention from all the community. In particular, for the complex large-span steel roof unloading process, it is important especially. The unloading process will cause the change of structure stiffness include the internal force redistribution. The real-time and on-line monitoring have been applied to Xining stadium of the stress in the process of unloading for the purpose of structural health assessment in the paper, so as to achieve the purpose of the early warning of the problems which may arise in construction process. At the same time, through the comparison of the finite element software ANSYS analogue simulation and the value of the actual, it is obtained for the quality problem of steel structure in the process of unloading.

Abstract: An arch-truss roof structure with circular steel tube is applied to a gymnasium. Natural frequency and modes of this overall roof structure are analyzed, and time-procedure analysis is acted by applying ANSYS software. The analysis results demonstrate that this roof structure has larger stiffness, and its maximum node displacement under earthquake（7 degrees）can meet the requirements.

Abstract: To research the temperature field distribution of concrete beams, experiments on fire resistance of 6 reinforced concrete simple-supported beams were completed. Test results indicate that: the trends of the temperature field distribution in each section of beam are the same, but the difference of the values in each section is large; the larger section of beam is, the higher temperature of beam surface and the more slowly the heat transfer to the internal of beam, which shows the increase of concrete cover thickness can improve fire resistance of beams; After the fire, the gradient of temperature field distribution is very serious in the internal of beam; the higher the temperature of the fire, the bigger damage of reinforced concrete beams is.

Abstract: According to the poorly seismic behaviors of composite staggered trusses system, an improved composite staggered trusses system was proposed. Based on the experimental study of a 1/3 scale improved composite staggered truss frame steel structure model under cyclic loading, the seismic behaviors and failure mechanism was studied, and the seismic behaviors was evaluated by the hysteretic behavior, ductility, energy dissipation and rigidity degeneration. The study showed that the improved composite staggered truss steel structures had the advantages in bearing capacity, ductility, deformability and energy dissipation, but the lateral rigidity was weak and non-uniform along its vertical layout. The stress measurement showed that the plastic hinge formed in the web members of the truss firstly, then, in the chord members of the truss, and finally the plastic hinges formed in the column, earthquake energy mostly dissipated by the truss members, the failure mechanism of the improved composite staggered truss steel structures was the beam hinges failure mechanism.

Abstract: Buildings constructed before the sixties in Algerian urban areas, are typically low and mid rise multi-storey buildings made of stone and/or brick masonry walls or infill light steel framing. These types of buildings are known to be vulnerable to seismic effects. Within this paper, an assessment of such existing structures, using the “Vulnerability Index” method is presented. This allows a good classification and description of the seismic quality of the structures taking into account both, structural and non structural parameters considered to be ones of the main parameters governing the vulnerability of the structure. A technical data sheet, including all information that might be used in an associated computer program in Delphi is subsequently developed. The results obtained show that the established classification confirms the observed information in situ.

Abstract: In this paper, corrosion percentages ranged from 0 to 7.62% of steel rebar for pulling out specimens was controlled by the accelerated method of electrochemistry. According to the RILEM standard, pulling out test with dimensions of 200×200×200mm3 and recycled aggregate concrete (RAC) of C30 was carried out, and the load versus slip curves between RAC and corroded steel rebars with different corrosion percentages were recorded. Based on the experimental results, the effect of RAC and reinforcement corrosion on the bond behaviour between steel rebars was investigated. The results show that the bond strength between RAC and deformed bars increases with corrosion up to a certain amount, and then the bond strength decreases as the corrosion rate further increases, which is similar to that of normal concrete. However, the decreasing rate of the bond strength between RAC and corroded steel rebars is much faster than that between normal concrete and corroded steel bars. According to the testing results, the relationship of bond stress-slip between corroded bars and RAC was given in the end.

Abstract: Bond-slip performance between section steel and concrete has effect on crack width of steel reinforced concrete（SRC）beams based on experimental results. Current standards about SRC structures do not involve bond-slip effects when calculating the crack width of SRC beams, and this is not valid exactly . This article describes a new method of crack width calculation for SRC beams, which considering the bond-slip effects on crack width. Crack width of SRC beams are divided into two parts: one part ignoring the bond-slip between steel and concrete, and the other part considering additional crack width caused by the bond-slip. The total crack width is the sum of the two parts. Results show that the proposed method in this article is coincide with experimental study.

Abstract: In this article, the authors identify the one built in 1998, eight-story structure of steel reinforced concrete body dynamic parameters, and discussed the soil - structure interaction on the identification results.In this study, an 8 degrees of freedom analytical model and the impact analysis model of soil-structure interaction to be established; through the analysis of microseismic observations, using non-parametric (transfer function and Random Decrement method) and parameter techniques (off-line system identification method, ARX :Auto-Regression with eXtra input) to identify the structure of the natural frequency, damping ratio and the story stiffness. Finally, in considering the soil-structure interaction cases, structural parameters were identification and compared the results to confirm the impact of soil-structure interaction.

Abstract: Through advanced non-linear finite element models in different geometric parameters that considering the semi-rigid character of the couplers, the critical loads and failure modes of many fastener steel tube full hall formwork supports (FFS) with and without bridging were evaluated. Thirteen FFS specimens were tested to failure in order to examine the stability behavior and failure modes of them. The finite element analysis (FEA) results were well consistent with those of the test what could prove its validity. On the basis of FEA and experimental research, simplified models and corresponding calculation formulas were established for the FFS under uniform load through choosing different buckling modes, which were verified by the experimental and analytical results and turned out to be accurate enough in predicting the strength. The simplified models presented here considering the semi-rigid character of right-angle coupler, effect of adjacent horizontal tube which provided a very useful reference for the industry as well as academia for design and future research.