Simulation of Mechanical Properties of Special-Shaped Concrete-Filled Steel Tubular Column and Steel Beam Joints after Fire

To study fire after the mechanical performance of steel girder node special-shaped concrete-filled steel tube column, based on standard ISO - 834 litres of cooling curve, the node temperature field model was established based on finite element software ABAQUS, the compute nodes in the overall uniform temperature field under fire as a result, the reasonable choice of fire after the steel and concrete constitutive model, the temperature field results into the node stress model, considering the factors that influence the whole effect of fire loading in low cycle, the nodes of the finite element model, and contrast analysis of the temperature after the fire of the node and hysteretic performance and ultimate bearing capacity. The results show that the failure modes of special-shaped CFST column-steel beam joints at room temperature and after fire are the same, and the ultimate bearing capacity of the joints after fire decreases significantly by 14.88% compared with that at room temperature.

Cyclic Experiments and Global Buckling Design of Steel-Angles-Assembled Buckling-Restrained Braces

Compared with traditional BRB, the steel-angles-assembled buckling-restrained brace (SAA-BRB) is an innovative BRB with light-weight, accurate control of the geometrical dimensions, easy installation and convenient disassembly. The SAA-BRB is composed of an external restraining system and a cruciform-sectional inner core. The external restraining system is assembled by four steel angles with the connection of high-strength bolts, and the spacers are installed between the inner core and the restraining system. In this study, the hysteretic behavior of SAA-BRB was investigated by experiments and finite element (FE) simulations. Firstly, three SAA-BRB specimens with different restraining ratios were tested under cyclic loads to investigate the hysteretic performance. It was found that all specimens exhibited stable responses and satisfactory energy-dissipating capabilities during the whole loading process. Then, a refined FE model was established, and its validity in predicting the hysteretic responses of SAA-BRB was verified by the experiments. Moreover, based on the yielding criteria of the outmost fiber for the restraining member section, a design formula for the restraining ratio requirements to avoid global buckling of the SAA-BRB was deduced. Finally, extensive parametric analysis was conducted to verify the accuracy of the design formula by changing the geometric dimensions (the restraining ratio) of models. It was found that the proposed formula for the restraining ratio requirement could lead to a conservative prediction with reasonable accuracy, thus providing valuable references for global buckling design of SAA-BRBs in engineering practice.

Study on hysteretic behavior of concrete CFRP specimen

In order to study the hysteretic behavior of concrete CFRP specimen under different influence factors, 12 specimens were designed. By consulting related literature, the research progress and main results of concrete-wrapped CFRP at home and abroad in recent years are summarized, and the accurate solution calculated by the multi-scale method and the error of the experimental value are verified by MATLAB. The non-linear vibration generated by the hysteretic performance under the action of wind excitation is introduced, which provides a certain reference for the later research.

Research on the hysteretic performance of flower-gusset composite joints for single-layer aluminium alloy lattice shell structures

Joints are the most critical component of reticulated shell structures, and their hysteretic performance is crucial to the mechanical properties of the whole reticulated shell structure under seismic action. Therefore, the hysteretic behaviour of aluminium alloy flower-gusset composite joint for an out-of-plane bending moment was studied by experiments and numerical analysis. The results show that the hysteretic curves of flower-gusset composite joints and gusset joints contain four stages: an elastic stage, a bolt slip stage, a hole wall pressure-stiffness degradation stage and a failure stage. The hysteretic performance of the new flower-gusset composite joint is obviously better than that of the traditional plate joint. With the increase in the thickness of the cover plate, the bending stiffness of the flower-gusset composite joint increases significantly, while the rotational deformation decreases. Then, a restoring force model of the flower-gusset composite joint is proposed through theoretical analysis based on experiments and numerical analysis.

HYSTERETIC PERFORMANCE OF WEAK-AXIS CONNECTION WITH I-SHAPED PLATES IN STEEL FRAME

This paper elucidates numerically the behavior of weak-axis moment connections proposed by welding I-shaped plates in the H-section column to increase connection strength and ductility in steel frame. After validating the numerical methods through comparing the results of numerical analysis and experiments, the effectiveness of the proposed weak-axis connection were examined through comparing to the traditional weak-axis connection. The proposed weak-axis connection could move the highest stresses away from the start-stop points of a weld, and thus preventing the premature brittle fracture of the beam flange welds. The plastic hinge formed away from the beam-column interface, while the local buckling occurred in the weld access holes region in the traditional weak-axis connection. The proposed weak-axis connections can be classified as rigid in a strong-bracing system, and be classified as semi-rigid in weak-supported or unsupported system. And then a series of parametric studies was conducted to better understand the behavior of proposed weak-axis moment connections. The force-displacement relationships, location of the plastic hinge, Mises index (MI), triaxiality index (TI) and rupture index (RI) distributions at the beam flange welds were reported in detail. According to the numerical analysis, the design variables of I-shaped plates and widened flange plate are suggested, along with a design procedure.