Advanced Materials Research Vols. 163-167

Abstract: Vertical cylindrical steel tanks are sensitive to differential settlement beneath the tank wall. Most previous studies were based on idealized harmonic settlement, however, for thin shell structures of high nonlinear behavior, it is obviously inappropriate to obtain the results under real settlement by simple summation of harmonic solutions. Real settlement of steel tanks can be grouped into two types - global differential settlement and local differential settlement. This paper examines the nonlinear response and stability behavior of floating-roof steel tanks under both types of settlement. It is shown that, for tanks under global differential settlement, local buckling occurs at the eave ring, followed by a stable post-buckling behavior, and final failure is by overall buckling of the tank shell; while for tanks under local differential settlement, the structural response is related to the degree of localization. At highly localized settlement, local snap-through buckling occurs at the tank wall, but it does not lead to a serious consequence, and the post-buckling behavior can also be utilized in design.

Abstract: Accorded with the criteria the X80 pipeline steels with RE additions have been prepared with a vacuum induction furnace. The effect of rare earths (RE) on austenite grain growth behavior in pipeline steel has been discussed in this work. After hot rolled, the effect of RE on austenite grain growth behavior have been studied by the thermal simulator, scanning electron microscopy and metallographic microscope. The results indicate that RE additions inhibit the abnormal growth of austenite grain, trace RE could significantly influence the austenite grain growth behavior, and obtain fine grain size in X80 pipeline steel. For instance, the activation energy of grain growth reduced from 475 kJ/mol to 425 kJ/mol with addition of 0.0220 wt.% RE according with no deliberate RE additions, but the grain growth index increased from 3.5 to 4.5.

Abstract: Nonlinear constitutive law was used in this paper. On the basis of plain section assumption, through isoparametric element theory, nonlinear secant and tangent stiffness matrices of section were derived. Nonlinear equation was solved by Newton-Raphson method. The bearing mechanism under the eccentric compression was revealed by changing eccentricity and position coefficient. The result is found to be in good agreement with the experimental data, and it shows that large and minor eccentricity failure mode, which are similar to reinforced concrete, are existed in steel tube-reinforced concrete column. In addition, force-moment correlation curve is derived. By calculation and comparison. The ultimate capacity is found to be greatly underestimated in the current technical specification.

Abstract: The dynamic characteristics are not only the important indexes for evaluating the bridge structural rigidity, but also the principal parameters for structural dynamic analysis and earthquake resistant analysis. In this paper, a three dimensional solid finite element model for a butterfly-shape arch bridge in Zhongshan city was established to analyze the dynamic characteristics. By comparison the numerical calculation results with measured results of the dynamic loading test, an analysis and evaluation of the dynamic performance of this new type spatial arch bridge was made, and can serve as reference to the dynamic analysis and seismic design of similar bridges.

Abstract: A certain project of tri-tower suspension bridge of which the main span was 1080m was taken as a case study of the mid tower stability. A 3D beam FEM model has been carried out to investigate the global mechanical behavior of the bridge in which the internal force response to several different typical load cases were specifically concerned. Moreover, the cable spring stiffness to the mid tower was defined as the ratio of the initial horizontal forces acting on the top end of mid tower to the corresponding horizontal displacement. And the effect of this equivalent spring stiffness on the stability performance of the mid tower was compared to other tow constraint conditions to the tower including free constraint and pin constraint. The comparison showed that the cable equivalent stiffness was 4342kN/m when living load was acting along the whole main girder of the bridge while this value varied with different load cases. The difference between the effect caused by the cable spring stiffness and the free constraint was small indicating that the stability of the mid tower was not sensitive to the cable constraint. In addition, with the increase of the equivalent spring stiffness, the longitudinal buckling eigenvalue also became larger and gradually approached the condition of pin constraint.

Abstract: Taking Xinjiang Exhibition Center Roof as an example, three models ("No construction stage" model, "Stretching on the ground" model and "Flow construction stage" model) were set up and analyzed with consideration of different segmented construction methods. The results show that the effect of the segmented construction method on the prestressed state of long-span truss string structures is significant. For the "No construction stage" model, the maximal cable force during construction is the largest among three models, while there are great differences between each cable force. However, the maximal displacement of sliding ends is the smallest among three models. For the "Stretching on the ground" model, the tension control force is the most uniform. This is because the cable of every truss is pre-tensioned independently, which causes no influence on other cables. For the "Flow construction stage" model, the maximal displacement of sliding ends and the uniformity of cable forces of the truss string structures are between those given by the other two models.

Abstract: Distortional buckling may occur for Cold-formed thin-walled steel lipped channel member except local buckling and overall buckling. The buckling of flange and lip are the important factor for the occurrence the distortional buckling. The different design codes have different design method for calculating plate buckling coefficient of flange and lip using the effective width method. So the effective width method in different codes are introduced and the load-carrying capacities of 100 lipped channel section compressive members collected from reference are computed using ‘Cold-formed steel structures (AS/NZS 4600:2005)’, ‘Supplementary rules for cold-formed members and sheeting(EN1993-1-3:2006)’, ‘North American specification for the design of cold-formed steel Structural Members(AISI-S100:2007)’, ‘Specification for the design of cold-formed steel structural members (AISI:1996)’ and ‘Technical code of cold-formed thin-walled steel structures’(GB50018-2002). The calculated results show that ‘Technical code of cold-formed thin-walled steel structures (GB50018-2002)’ and ‘Supplementary rules for cold-formed members and sheeting (EN1993-1-3:2006)’ are conservative and ‘Cold-formed steel structures (AS/NZS 4600:2005)’, ‘North American specification for the design of cold-formed steel Structural Members (AISI-S100:2007)’ and ‘Specification for the design of cold-formed steel structural members (AISI:1996)’ are unsafe. The elastic buckling stress of different lipped channel sections are predicted by finite strip program (CUFSM) and get the suggested calculation formula of plate buckling coefficient of flange according to regression Analysis. The calculated results using suggested plate buckling coefficient of flange are agree to test results.

Abstract: A two-span, three-story steel frame with two web and top-seat angle connections was constructed. Then a low-cycled reverse loading experiment with this frame was conducted to obtain elastic-plastic behavior of semi-rigid connections steel frame under cyclic loading. And nonlinear finite element analysis of steel frame with semi-rigid and rigid connection is performed in this paper. At last, comparisons between the analysis results and the testing results are carried out, the behavior and the effects of the two web and top-seat angles connections on steel frame are analyzed.

Abstract: Transmission tower-line systems with different elevations in mountainous areas are established in this paper. The change curve of ice increasing with time was given according to the data of ice record. Considering the influences of height difference, ice increasing, plastic analysis of transmission tower is carried out. It can be concluded that the ultimate bearing capacities of ice coating of the tower is significantly influenced by the elevation of the towers beside it. It also can be concluded that the ultimate bearing capacity of ice coating can be improved only when the section of weakness member is increased.

Abstract: Heavy rail steel was prepared by the process of vacuum induction furnace smelting, forge work and rolling. Effects and mechanisms of niobium on the fracture toughness of heavy rail steel were investigated. In addition, the appropriate range of niobium content for heavy rail steel was determined. With the niobium content increasing, both the austenite grain size and pearlite laminae distance of heavy rail steel were decreased gradually at first and then increased rapidly. When the niobium content was low, the precipitates containing niobium predominantly appeared in the cementite, which improved the toughness of heavy rail steel by fining the austenite grain size and pearlite laminae distance; when the niobium content > 0.024%, the fine dispersed precipitates containing niobium mainly occurred in the ferrite, which improved the toughness of heavy rail steel by pining dislocations and inhibiting crack growth; with the niobium content increasing, both the quantity and size of precipitates containing niobium were increased gradually; when the niobium content > 0.073%, most precipitates containing niobium could not pin dislocations and inhibit crack growth because the particles size was too big, thus the fracture toughness of heavy rail steel was bad. So the optimum range of the niobium content could improve the fracture toughness of heavy rail steel. In the present study, when the niobium content was about 0.053%, the fracture toughness of heavy rail steel was the best. The maximum plane-strain fracture toughness was 49.88 MPam^1/2.