Behaviour Of Steel Connections Research Articles

Investigating the prying force magnitude and location in the T-stub connection based on the energy method

The prying action as a vital phenomenon in the bolted connections plays a major part in the behavior of steel connections. It is worth mentioning that prying force location has been considered to be at the edge of the flange in the T-stub model. Present research aims to investigate the prying force magnitude and location in the T-stub connection based on the energy method. Therefore, analytical formulas for the ratio of the prying force to the applied load and prying force location with and without considering shear deformation effect were proposed based on the energy method for bolted connections with no pretension. Results obtained from the formulas were compared with the results of the experimental and numerical models. Based on the obtained results, it was understood that despite previous assumptions that the location of the prying force is at the edge of the flange for all the cases, the prying force location depends on the thickness of the flange and the bolt distance from the web of the T-stub. Hence, considering prying force location at the edge of the flange underestimates the real value of the prying force resulting in premature failure of the bolt and connection.

A Study on the Application of Two Different Material Constitutive Models Used in the FE Simulation of the Cyclic Plastic Behavior of a Steel Beam-Column T-Stub Connection

Seismic actions inevitably cause cyclic plastic deformations in steel frame connections, which is a common cause of failure in steel structures. Nonlinear finite element (FE) static analysis has been employed in the study of the cyclic plastic behavior of a T-stub connection based on the reported cyclic test on the corresponding extensively tested T-stub connection made of Q235 steel. In particular, the isotropic-hardening and Chaboche constitutive models were employed to predict both the stress distribution and plastic development on the T-stub and the hysteretic curves of the entire T-stub connection. The two constitutive models were calibrated by four material tests to describe the yield and hardening behaviors of the Q235 steel used to make this T-stub connection. The two sets of simulation results obtained from the simulations of the two FE models employed by the two different constitutive models were compared with each other and with the experimental results. The comparisons reveal that the simulation results are similar and in good agreement with the experimental results when the cumulative plastic deformation in the T-stub is small. However, the results of the FE analysis using the Chaboche model are in better agreement with the experimental results when the cumulative deformation in the T-sub is large. This study can provide a reference for FE simulation of the cyclic plastic behavior of steel connections, including the T-stub connection.

Failure modes of end-plate connections with outer flange stiffeners: an experimental and numerical study

This paper presents the experimental and numerical results of six full-scale beam-to-column connections with bolted end plates in two groups. The effects of vertical and horizontal stiffeners on the static behaviour of the semi-rigid beam-to-column bolted connections were investigated. In addition, the aim of this research was to analyse the influence of end-plate connections that utilize the IPE profile with stiffeners welded on the behaviour of steel connections, to provide the necessary data for improving Eurocode 3, efficient use of residue IPE profiles and back to the consumption cycle. Furthermore, finite-element and experimental models of semi-rigid vertical and horizontal stiffened bolted connections were tested and compared. The main parameters observed are the evolution of the resistance, the stiffness, the rotation capacity, the ductility of a joint, failure mode and the energy dissipation.

A Novel Approach for Bolted T-Stub Connections

This paper reports an investigation into new connection types and their behaviors determined using full-scale experiments. T-shaped connections were created using the IPE standard profile. The aim of this study was to analyze the influence of T connections based on the IPE standard profile, height of beam to height of T-stub joint (H) of T-stub joints, and lengths (X) of T-stub joints on the behavior of steel connections, in order to provide the necessary data for improving Eurocode 3 and enable efficient use of residue IPE standard profiles and back to the consumption cycle. While the moment resistance values increased with an increase in H from Hmin to Hmax in model groups with X of 126 mm, and the energy dissipation increased with an increase in H from Hmin to Hmax and also with an increase in the lengths (X) of T-stub joints from 54 to 126 mm.

03.32: Analytical prediction of moment‐rotation behaviour of austenitic stainless steel bolted connections

ABSTRACTSteel framework is one of the most commonly used structural systems in modern construction and beam‐to‐column connections play a significant role in overall performance of the structure. Semi‐rigid behaviour of steel connections was investigated both experimentally and numerically over the last few decades. Stainless steel alloys are now increasingly used in construction industry owing to their superior material properties such as corrosion resistance, higher strength, enhanced ductility, significantly lower maintenance cost and attractive appearance. In this study, the performance of stainless steel top‐seat with or without double web angle (DWA) bolted connections are analytically investigated using a proposed four parameter power model assuming plastic hinges are formed in the connected angles. The proposed analytical model can predict the moment‐rotation behaviour using four key connection parameters such as initial stiffness, strain hardening stiffness, reference plastic rotation and shape parameter. These key parameters were expressed as functions of easily obtainable geometric and material properties. This model allows to predict complete moment‐rotation curves for stainless steel connections using the knowledge of easily available properties and configurations of the connecting elements. Analytically predicted moment‐rotation curves were compared with those obtained using 3D finite element models, and showed good agreement with actual connection behaviour.

The simple model for welded angle connections in fire

Due to the high sensitivity of fire affected steel behavior, fire resistance of steel structures is of great importance. Moreover, since the connections act as the main means of integration of frame members, the behavior of steel connections in fire is significantly important. Considering the importance of this matter, this paper describes a spring-stiffness model developed to predict the behavior of welded angle connections made of bare-steel at elevated temperature. The joint components are considered as springs with predefined mechanical properties i.e. stiffness and strength. The elevated temperature joint’s response can be predicted by assembling the stiffness of the components which are assumed to degrade with increasing temperature based on the recommendations presented in the design code. Comparison of the results from the model with existing experimental data shows good agreement. The proposed model can be easily modified to describe the elevated temperature behavior of other types of joints as well as joints experiencing large rotations.

Investigation of Shear Capacity of Steel Bolts under Elevated Temperatures

Structures that have collapsed as a result of fire, such as the World Trade Center 7 building, have highlighted that the behavior of steel connections at elevated temperatures is not well understood. The purpose of this research project was to determine the shear capacity of structural steel bolts at 500°C and 550°C. A laboratory test setup was designed and built to conduct full-scale experimental tests on bolts within connections. The test setup allowed the specimen to be loaded in tension or compression using two hydraulic rams and heated with high-temperature ceramic radiant heaters to simulate fire conditions. Thermocouples were used to monitor the temperatures inside the bolt and on the exterior surface of the bolt, and displacement sensors were used to monitor the relative displacement of the bolt. A thermal test in which the shear surfaces of the bolt were heated to 550°C was conducted. The results show that when the bolt is heated at a rate of 7°C per minute, the temperature of the exterior bolt surface is 1.4 times higher than that of the interior shear surface of the bolt. This information will be beneficial for future tests as the temperature inside of the bolt can be determined without the use of a thermocouple in future experiments. In subsequent tests, bolts will be loaded to failure once the bolt inside temperature reaches 500°C and 550°C. The results of the loading tests at elevated temperatures will be compared to the ambient loading test results to examine the differences in behavior. The experimental data from both the thermal and mechanic tests will be used in future tests that will study the thermal and structural performance of steel connections.

Fatigue Behaviour of Welded Steel Connections under Combined Actions

This paper describes experimental and numerical studies on the fatigue behavior of steel connections under combined loads, including a cyclic load and a static load. The steel connections consist of two steel plates joined together by single-sided girth welds. They were tested to failure under a constant amplitude tensile cyclic load combined with varied tensile static loads, which are perpendicular to the cyclic load. The experimental results reveal that the presence of the tensile static load in the perpendicular direction to the cyclic load is able to reduce the fatigue crack propagation rate and hence extend the fatigue life. Modeling of the steel connections is described in this paper to determine the effect of the magnitude of tensile static load on fatigue propagation life. The Boundary Element Analysis System Software (BEASY) is used. The analyses of these tested specimens are compared with their experimental results. It is proved that the boundary element method through the BEASY software is able to provide a close estimation of the cyclic behavior of steel connections.

Component modelling of flexible end-plate connections in fire

This paper describes a component-based model for simulating the behaviour of flexible end-plate connections between beams and columns in steel framed structures in fire conditions. In this method, a simple steel connection was split into a number of active components for which mechanical properties are represented by non-linear springs. The behaviour of a steel connection is then determined by assembling the individual behaviour for each active component into a spring model. The component model presented in this paper is capable of predicting the behaviour of steel connections under varied loading conditions. It is also capable of predicting the tying resistance and critical components of failure for steel connections in fire. Compared with experimental test data, a good correlation with the simplified model has been achieved and this method, combined with finite element modelling, may be used to examine the performance of simple steel connections in fire conditions.

Numerical simulation of bolted steel connections in fire using explicit dynamic analysis

Behaviour of steel connections in fire is a multi-dimensional problem involving parameters such as temperature, tying forces and large deformations. Investigation of this behaviour will remain one of the main subjects for fire engineering research in the coming years. Finite element simulation plays an important role in the study of connections because fire tests are expensive to perform. Unlike normal structural analyses, finite element simulation of bolted steel connections is a challenging task, as large numbers of contacts exist in the model. This leads to convergence difficulties in static solvers. This paper explores the use of an explicit dynamic solver to analyse bolted steel connections. By comparing the results with those from static analysis and tests, it is shown that the explicit dynamic solver, with proper control, gives satisfactory predictions of the responses of steel connections up to post-failure deformations.

An effective two-dimensional numerical method for the analysis of a class of steel connections

This paper presents a successful method to analyse steel plate connections under static loading and to calculate their respective stress states. In particular, the proposed method which is based on the theoretical results of a new branch of Mechanics, called Nonsmooth Mechanics, concerns the simulation of the structural behaviour of steel connections in the case that the development of zones of plastification, as well as unilateral contact and friction effects on the interfaces between connection members and bolts are taken into account. Within the framework of the herein proposed method, effective two-dimensional finite element models capable to describe plasticity, unilateral contact and friction effects are constructed; the latter constitute easy-to-use and accurate numerical models for the analysis of steel connections subjected to static loading. The aforementioned models are simplifications of the respective three-dimensional ones and aim to reduce in a reliable way the huge computational effort required for the analysis of three-dimensional fine meshes of discretized steel connections.