Advanced Materials Research Vols. 163-167

Abstract: The different dilatometric curves of continuous cooling transformation with the different cooling rates were determined by means of Gleeble-2000 thermal simulation machine. The CCT curve of heavy rail steel was obtained by measuring the dilatometric curves and metallographic analysis. And the effects and mechanisms of chromium on the phases transformation of heavy rail steel were investigated. It is found that, the heavy rail steel only takes place pearlite and martensite transformation during continuous cooling. The CCT curve of heavy rail steel is moved right with increasing chromium content, which indicates that chromium can obviously improve the stability of super cooled austenite and delay the pearlite transformation. When the content of chromium is increased from 0.21% to 0.40%, the shortest incubation time of pearlite transformation is increased from 25s to 52s. When the cooling rate ≤ 5°C s^-1, with increasing chromium content, both starting and finishing temperatures of pearlite transformation are decreased at different extent, meanwhile the pearlite is refined. In addition, when the content of chromium is increased from 0.21% to 0.40%, the critical cooling rate of quenching is decreased from 15°C s^-1 to 7°C s^-1.

Abstract: Orthotropic monolithic steel bridge deck system stiffened by U rib is very fit for high-speed railway steel bridges because of its excellent mechanical behaviors. Thickness of flange is a very important parameter of U rib and has influence on mechanical behaviors of orthotropic monolithic steel bridge deck system. Based on the engineering practice of Anqing Yangtze River Railway Grand Bridge, the kind and the extents of influences of thickness of flange of U rib on mechanical behaviors of orthotropic monolithic steel bridge deck system are studied with finite element analysis. The results show that thickness of flange of U rib has relative large positive influences on rigidity, strength and stability of orthotropic monolithic steel bridge deck system. 14~18mm is the appropriate range of thickness of flange of U rib for high-speed railway steel bridges.

Abstract: The initiation position can be predicted by studying on strain concentration factors (SNCF) and SNCF distributions. This paper concerns an experimental investigation of SNCF of welded T-joints composed of circular hollow section (CHS) braces and concrete-filled square hollow section (CFSHS) chords under axial loading on the braces with two load cases of tension and compression. Static experiments were performed on eight test specimens designed for considering different non-dimensional geometric parameters and C50 grade concrete. Compared with joints made of CHS-SHS, the experimental results indicate that the CHS-CFSHS T-joints have lower strain concentration factors which may increase fatigue strength. The position of the maximum SNCF is usually located at 0⁰ or 90⁰ of the intersection line between a CHS brace and a CFSHS chord.

Abstract: Application of orthotropic steel bridge decks has become increasingly widespread, but with the growing traffic, the bridge decks frequently get fatigue damage, even forming cracks. This paper makes an overall analysis on the orthotropic steel bridge decks cracks of a certain bridge in Southern China, and experimentally studies on both in-situ and new strengthening materials, including low temperature impact toughness, conventional mechanical properties and fatigue performance. Test conclusions indicate that the two materials have good performance, which means the cracks have no business of in-situ materials, and the strengthening materials can be put into use.

Abstract: This paper focuses on the research of stability capacity of shells with openings, the judgment of joint rigidity and the influence of joint rigidity on stability capacity of shell structure. The research result showed that it should give priority to use ribbed-Schwedler shells for the shells with large openings. Currently, there is no clear standard for judging joint rigidity, this paper presents a way to identify the steel joints stiffness. In the structural design of Chang'an stadium, according to the joint structure, it is proved to be hinged node by analyzing the joint stiffness. Buckling analysis results show that: single-layer shell with hinged nodes also has good stability. The result of the research has a certain value to practical engineering design.

Abstract: This paper investigated some problems in steel tubuar joints design.The joint stiffness has played an important role in evaluating the whole stability of the structure. Currently there is no clear standard for judging joint stiffness, this paper presents a way to identify the steel joints stiffness. Accordingly, the analysis results of joint stiffness can be directly applied to practical engineering. This paper also proposed new steel welded joints which adapt to space slant and twisted surface for solving problem about square steel pipe joints design. This joints not only ensure regional stiffness and have an attractive appearance, simple structure, but also apply to engineering very well. The result of the research has a certain value to practical engineering design.

Abstract: Taking Jinan Yellow River Bridge as an example, using 3D finite element method, displacement and behavior of four-line high-speed railway bridge with two main trusses, K-shaped brace and middle suspender is studied. The results show that transversal wave of displacement of floor system is significant, and the difference of the displacement in transversal direction reaches 6 mm. The causes includes: large distance between two main trusses, large stiffness of stringers, longitudinal stiffeners and crossbeams, weak transversal stiffeners which do not connect to lower chords. About 90% of the loads are transferred to the crossbeam through path 1 and about 60% to 80% of these loads through K-shaped braces. Less than 10% of the loads transferred to lower chords through path 2.

Abstract: Cast-steel joints characterized in strong adaptability are widely applied in various long span spatial structures. At present, there is no national design specification available on cast-steel joints. Therefore, it is quite a necessity to conduct full-scale test or model test on cast-steel joints suffering complicated forces. This Paper has, taking Nantong Sports Exhibition Center as an example, conducted the experimental study of some important joints, and compared with elastic-plastic nonlinear finite element analysis result. According to the result, the fracture morphology of joints, stress distribution and bearing capacity of joints obtained from the elastic-plastic nonlinear finite element analysis are consistent with those of measured result, proving that the analysis theory applied in engineering design is basically suitable for the actual working condition of cast-steel joints and the joints are sufficiently safe.

Abstract: Crisscross concrete-filled steel tube core column is a kind of new component. In this paper, the cross-sectional temperature distributions and thermal-stress of crisscross concrete-filled steel tube core columns are analyzed by using nonlinear finite element method under eight-side fire, so we can acquire mechanics performance in the high temperature life and fire-resistant. Simulation results show that: this kind of construction has a good inherent performance under fire, moreover, reducing load is an effective measure to improve the fire resistance of crisscross concrete-filled steel tube core columns.

Abstract: Full-scaled bearing capacity experiments are performed on a new type of profiled steel sheet, i.e. HV-380. Experiments are divided into two parts. In the first part, positive uniform loads are applied on test specimens to determine bearing capacity of sheet system under downward load perpendicular to sheet. While negative uniform loads are applied on test specimens to determine bearing capacity of sheet system under upward load perpendicular to sheet in the other part. The experiment result indicates that the capacity under negative uniform loads is less than it under positive uniform loads for same sheet type and configuration, i.e. wind uplift governs the design of the new type of profiled steel sheet; and most failure mode is clip failure. Based on experiment result, wind resistances are derived and applicable regions are suggested.