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Low yield point (LYP) steel is a kind of excellent material used in seismic structures. To get its constitutive model under cyclic loading, 20 specimens made of LYP steel SLY100 were tested under different loading systems. Monotonic characteristics, hysteretic curves, and failure modes were analyzed. Skeleton curves under cyclic loads were fitted. Parameters of combined hardening model were calibrated and verified. Then the constitutive model was applied in the numerical simulation of BRBs. It was indicated that SLY100 steel exhibited significant cyclic hardening phenomena and possessed distinguished ductility even after being subjected to cyclic loading. The Ramberg- Osgood model fit the skeleton curves well under cyclic loading with strain increasing gradually; good consistency between the stress-strain curves calculated by ABAQUS and test curves demonstrated the accuracy of the hardening parameters proposed. The finite element (FE) model of the buckling-restrained braces (BRBs) with SLY100 steel in which calibrated results were applied could simulate BRBs' performance well. [ABSTRACT FROM AUTHOR]

In order to quantitatively describe the effect of strength and stiffness degradation on seismic behaviors of steel frame, numerical models (the equivalent constitutive model considering damage and steel hysteretic constitutive model without considering damage) for predicting seismic behaviors of steel frame structures were described. Three frame models of five-floor, ten-floor and fifteen-floor frames were analyzed. Eight earthquake records were selected for time history analysis. The differences of inter-story drift ratio distribution calculated by two constitutive models were compared. The influencing laws and degrees of damage and degradation on seismic behaviors were also obtained. Finally, a prediction curve of degradation index was proposed, which could be used for damage control. Preliminary evaluation methods for seismic performance of steel frames considering damage and degradation were discussed. The analysis of the results showed that: the inter-story drift ratios of the three frames calculated by damage model were obviously larger than the results of non-damage model, showing that damage and degradation amplified the structural deformations. With the increasing of floors, the differences of inter-story drift ratio between damage model and non-damage model were gradually reduced. The weak stories of three models were located at 0.4 to 0.5 times of structural height, which should be paid more attention in design process. [ABSTRACT FROM AUTHOR]

8 specimens of beam-to-column bolted end-plate connections with various details and welded I-shaped section columns and beams were tested under monotonic loads. Based on the specification for the end-plate connection rotation proposed, the contribution of the panel zone and the gap between the end-plate and column flange to the joint rotation have been obtained. The influences of both flush and extended types, column stiffeners, end-plate rib stiffeners, bolt sizes and end-plate thicknesses etc on the joint behaviour have been compared. The test results indicate that all these connections tested are typically semi-rigid. For the flush and extended end-plate connection, the joint rotation mainly derives from the relative deformation between the end plate and the column flange and the shearing deformation of the panel zone respectively. Using a special method to measure bolt strain, the bolt tension forces and their development and distribution have been depicted and studied, and two bolt tension force distribution models for end-plate connections using pretensioned bolts are recommended. [ABSTRACT FROM AUTHOR]

Study of the dynamic properties of a monolayer cable net is described in this part II of the paper. The linear vibration properties of a cable net are analyzed in the form of a lumped-mass system based on the assumption of small-amplitude vibration. The respective influence of two vital factors: geometric shape and cable pretension on the dynamic properties of cable nets at different deflected positions under load is especially focused upon. Results show that when the geometric shape has a small displacement, the displacement influence on frequencies of vibration is almost the same as that of pre-tension, otherwise, the influence of geometric shape is far greater than that of pre-tension. Dynamic tests on the cable net model mentioned in Part I were also carried out at each pre-stretching stage. The results of experiments agree well with those of finite element analysis (FEA). In addition, a modified method called ‘MML’ based on Rayleigh's approach for the calculation of fundamental frequency is put forward in this paper, since it was found that Rayleigh's approach may sometimes introduce large errors. The nonlinear dynamic properties of the cable net were also analyzed. Different from the linear vibration case, nonlinear cases are to some extent amplitude-dependent. Thus explicitly approximate formulae for the first and second nonlinear modal frequencies are derived from continuous theory assuming the cable net to act as a continuous membrane. Transient dynamic analysis using the finite element software ANSYS was carried out to validate the formulae. The results given by the formulae and those via numerical analysis agree with each other well. [ABSTRACT FROM AUTHOR]

Monolayer cable nets have been widely applied in point-supported glass facades in recent years because of transparency, light weight and flexibility of construction. In this paper, work on the static load bearing performance of this type of cable net is described through the use of finite element analysis (FEA) and tests on a 1/10-scale model of a real project in P.R. China under construction. Firstly a method of analysis inverse to the sequence of erection and much different from conventional methods, is used to model the pre-stretching of cables with the aid of FEA to provide guidelines for the tests. Cable pre-stretching proceeds by three stages, then load bearing behaviour tests on the cable net are carried out both before and after the installation of glass panels. The agreement between the pre-stretching tests and the FEA analysis indicates that the inverse analysis method is convenient in calculation, and provides useful references for the pre-stretching of similar types of cable net in practical engineering. The nonlinear relationship found between loads and displacements just indicates the nonlinear properties of flexible cable nets. Before the installation of glass panels, the structural stiffness actually increases slowly with increasing external loads, and greater initial pre-tension is more beneficial to load bearing capacity of the structure. But too large an initial pre-tension may overload the supporting structures of the cable net. The increase in cable force due to external loads is small. Nevertheless, the stiffness of the glass panels themselves make a significant contribution to the overall structural stiffness, the contribution which becomes less obvious as the stiffness of the cable net itself increases. [ABSTRACT FROM AUTHOR]

The pinned connection method was used to connect the large-span floor truss to the steel column in Zoucheng International Conference Center project, which played a quite important role to achieve the in-plane rotation and transfer heavy loads directly. Four specimens were tested experimentally to investigate the monotonic and cyclic behavior of this connection method, including two independent pinned connections and two assembled truss connections. The load-displacement curves, deformation development, failure mode, ductility and energy dissipation capacity were discussed in detail. Besides, the nonlinear multi-scale finite element models of the pinned and truss connections were established. The numerical simulations not only captured the global behavior and local limit states observed in tests but also revealed valuable new information that could not be directly obtained from the tests. The experimental and numerical results showed that both the pinned and truss connections had good ductility, load transfer ability and ideal rotation capacity with large safety margin, indicating these constructions could be used as references for similar projects. [ABSTRACT FROM AUTHOR]

The present investigation studies the load bearing performance of stainless steel bolted connections. The austenitic stainless steel developed in China containing approximately 17% of Cr, which could be graded as EN 1.4401, has been selected for this research. In order to study the bearing strength of stainless steel bolted connections, experimental tests on 5 specimens have been conducted. In addition, complementary finite element (FE) models, which have been validated by the test results, have been adopted to analyse the effect of the key factors for bearing strength of the stainless steel bolted connections. The key factors include end distance, thickness of connecting plate, diameter of stainless steel bolt and edge distance. According to the FEA results, the loading capacity increases with the increase of the thickness of the plate and the diameter of the bolt approximate linearly. However, the end distance and edge distance have a comparatively complicated influence on the loading capacity of the connection. Based on mathematical analysis of the experimental and FEA results, a calculation method as well as its simplified form for the bearing strength of stainless steel bolted connections has been proposed. [ABSTRACT FROM AUTHOR]

The present investigation studies the overall stability bearing capacities of stainless steel welded I-section beams. Experimental tests of 8 specimens have been conducted. In addition, complementary finite element (FE) models, which have been validated by the test results, are adopted to calculate the overall stability bearing capacities of the beams. Based on the results of FE analyses and experimental tests, as well as the comparisons of design standards for buckling reduction factor calculations of stainless steel structural components, two calculation methods for buckling reduction factors of welded I-section beams are proposed. One is the modification of Chinese code for design of steel structures, and the other is regressed by the FE analysis results. Both methods are conservative and have simple formulations for engineering design. [ABSTRACT FROM AUTHOR]