Experimental study on full-scale steel beam-to-column moment connections

Ten full-scale steel beam-to-column moment connections used in moment-resisting frames （MRFs） were tested to study the failure process, failure mode, strength and plastic rotation capacity. The specimens include one traditional welded flange-bolted web connection, one traditional fully welded connection, four beam flange strengthened connections, three beam flange weakened connections, and one through-diaphragm connection. The test results show that the connections with flange cover plates or with partly cut beam flanges satisfy the beam plastic rotation demand for ductile MRFs. From the measured stress profiles along the beam flange and beam web depth, the mechanics of brittle fracture at the end of the beam is discussed. Design recommendations for steel beam-to-column moment connections are proposed.

A cyclic loading model for beam-to-column web connection

A finite element analysis of the beam-to-column web connection with H-shaped columns was performed using the ANSYS computer program. Based on the finite element analysis and theoretical analysis, a simplified model was developed to describe the cyclic loading behavior of beam-to-columns web connection in steel moment resisting frames, considering both bending and shear deformation modes of the beam flange plate. Several issues appearing to merit further researches were identified in the process of developing this model, such as the effect of beam flange plate on beam-to-column web connection stiffness and strength. A reasonable agreement was achieved between model predictions and finite element data, which verified the feasibility of the proposed model.

Local Tensile Strength of Connection Between H-Steel Beam Flange and Concrete-Filled Circular Column Tube with Through Diaphragm

This paper focused on investigating local tensile strength of connection between steel beam flange and concrete-filled circular column tube with through diaphragm. Three specimens were designed and tested to failure, and the structure behavior was studied by experiment and FEM analysis. On the basis of the results obtained, an estimation for local plastic and ultimate strengths of the connections using yield line theory was attempted, which results in a good prediction.

Research on BP-ANN Model of Semi-rigid Connection

The beam-to-column semirigid connection in a steel frame structure is represented by a zero-length rotational spring at the end of the beam element. The beam-to-column semirigid connection behavior is represented by its moment-rotation relationship. Several traditional mathematical models have been proposed to fit the moment-rotation curves from the experimental database,but they may be more reliable within certain ranges. In this paper, the intellectualized analytical model is proposed in the semirigid connections for top and seat angles with double web angles using the feed-forward back-propagation artificial neural network （BP-ANN） technique. the intellectualized analytical model from experimental results based on BP-ANN is more reliable and it is a better choice to the moment-rotation curves for beam-to-column semirigid connection. The results are found to provide effectiveness to the experimental response that is satisfactory for use in steel structural engineering design.

Numerical Analysis of the Composite Connection of Steel Joist Embedded in Concrete Girder

So far, numerous numerical studies have been conducted on the behavior of Composite Reinforced Concrete-Steel （RCS） beam-to-column connections. However, the lack of studies regarding the steel joist-concrete girder connection has yet to be addressed through comprehensive finite element methods to get an understanding of influential parameters. Hence, in this paper, composite connection of embedded steel joist in concrete girder is investigated with an appropriate finite element software, namely, ABAQUS. The validity of the proposed model is examined by the comparison made with the test data in literature. Results indicate that maximum bending capacity of the connection is achieved when embedment ratio is 1.78. Moreover, double web angles in the embedment region significantly reduce the embedment length required to achieve the maximum bending capacity. Finally, damage analyses show that bending capacity of concrete girder is slightly reduced in the connection zone.

Damage identification in connections of moment frames using time domain responses and an optimization method

Damage is defined as changes to the material and/or geometric properties of a structural system,comprising changes to the boundary conditions and system connectivity,adversely affecting the system’s performance.Inspecting the elements of structures,particularly critical components,is vital to evaluate the structural lifespan and safety.In this study,an optimization-based method for joint damage identification of moment frames using the time-domain responses is introduced.The beam-to-column connection in a metallic moment frame structure is modeled by a zero-length rotational spring at both ends of the beam element.For each connection,an end-fixity factor is specified,which changes between 0 and 1.Then,the problem of joint damage identification is converted to a standard optimization problem.An objective function is defined using the nodal point accelerations extracted from the damaged structure and an analytical model of the structure in which the nodal accelerations are obtained using the Newmark procedure.The optimization problem is solved by an improved differential evolution algorithm(IDEA)for identifying the location and severity of the damage.To assess the capability of the proposed method,two numerical examples via different damage scenarios are considered.Then,a comparison between the proposed method and the existing damage identification method is provided.The outcomes reveal the high efficiency of the proposed method for finding the severity and location of joint damage considering noise effects.

Experimental study on slender buckling-restrained knee braces with round steel bar cores

This study aimed to investigate a novel slender buckling-restrained knee brace damper (BRKB) for welded and weld-free steel framing systems. The proposed BRKB adopts steel bar cores connected by a central coupler and restrained by tube buckling restrainers with a cover tube supporter. The advantages of the proposed damper include easy assembly compared to conventional buckling restrained braces, and high architectural flexibility for the retrofitting of large-span weld-free or welded steel moment-resisting systems. Specifically, by increasing the number of contraction allowances, undesirable failure mechanisms that are global instability and local buckling of the restrainer ends can be effectively suppressed because the more uniform plastic deformation of the core bar can be achieved longitudinally. In this study, displacement-controlled compression and cyclic loading tests were carried out to investigate the deformation capacities of the proposed BRKBs. Structural performance metrics associated with both loading tests, such as strength capacities, strains at the cover tubes and buckling restrainers, and hysteretic behaviors of the proposed damper under cyclic loads, were measured and discussed. Test results revealed that the geometrical characteristics of the cover tubes and adopted contraction allowances at the dampers play essential roles in their load-bearing capacities.