Abstract

Depending on the type of configuration and connector arrangement, beam-to-column end-plate joints can be rigid, semi-rigid, or pinned. Fully restrained joints are required for rigid frames in which it is anticipated that the frame joints will have adequate rigidity to maintain the angles between intersecting parts in the service condition, ensuring full moment transfer. In contrast, partially restrained joints in semi-continuous frames are distinguished by relative rotations between crossing members, allowing the bending force to be transferred only partially. The concept of utilizing partially restricted, unstiffened joints in construction has gained traction since it looks to be more feasible and inexpensive. Bending transfer in partially constrained joints allows semi-continuous frames to withstand actions. Semi-continuous frames can survive actions due to bending transfer in partially restricted joints. At the same time, a certain degree of rotation is permitted, which improves the overall ductility of these structures. Using thinner end plates than those used in practical applications is one of the most effective ways to affect the ductility of end-plate beam-to-column joints. It was confirmed in a previous experimental study that the composite joints, where the thickness of the end plates is equivalent to about 60% of the diameter of the bolt used in composite joints, were taken into account in subsequent tests, and these studies can be confirmed using ABAQUS and Ls-Dyna modelling. All of these concerns are addressed, and recommendations for numerical modelling methodologies are made in order to ultimately analyse the reaction of the symmetric extended end plate joints with 8-bolts under hogging and sagging bending moments.

The paper presents new studies on numerical modeling (FEM) for beam-to-column behavior under sagging and hogging bending moment when the framework is exposed to service and unexpected loads that may cause a column loss scenario. This investigation is focused on four bolts end-plate joints with 10 mm thickness which are proven experimentally to have more ductile behavior than other end-plates joints (6, 8 bolts), spite of their weakness to transfer the unexpected loads from the initial state to a residual state of the stable equilibrium, that leads to a failure of limited floor area to adjacent joints when tested experimentally (Saleh, 2014). FEM technique used in this research is an extension of the previous technique and is characterized by the use of a more sophisticated technique than the previous, discovered from the result of continuous research and the use of all the options available in the new version of commercial ABAQUS/CAD software. The elements are designed using multiple layers of specific elements of a brick arranged in such a way that the mesh nodes of the tiles should coincide with certain layers with the top of the shear inlay and in line with reinforcement, not as the former study that used thick shell elements to model the reinforced concrete slab with total negligence of reinforcing steel and bolts between the slap and the beam. This investigation is very complex because of highly nonlinear effects associated with the prediction of joint performance, such as structural imperfections, huge displacements and large rotations, inelastic properties of steel and concrete, bonding effects between steel and concrete, friction between …

The paper presents studies on experimental investigation of beam-to-column joint behaviour in standard and exceptional events situations. This assessment is done to form a picture of the general the behavior of full scale frameworks at both the level of the global behavior of the framework, in terms of its load-displacement characteristic, and of the local behavior of joints in terms of their moment-rotation characteristics, and evaluates details about the interaction of the joint elements and how they work together in a balanced manner, during exceptional events, this study concerns the joints which are subject to the collapse and also includes the behavior of joints in the neighborhood of the collapse. The intricacy of such investigations appear from nonlinear effects associated with the outlook of joint behavior or functioning, such as structural shortcomings, large displacements and rotations, inelastic properties of steel and concrete materials, the effects between steel and concrete, and slip between concrete and structural steel, through others. The paper addresses these problems using two types of joints flush and extended end-plate with four and eight bolts and provides recommendations and reasoning for the behavioral techniques for the evaluation of joint moment-rotation response when exposed to negative and positive moments together.

The paper presents studies on experimental investigation of beam-to-column joint behavior in standard and exceptional events situations. This assessment is done to form a picture of the general the behavior of full scale frameworks at both the level of the global behavior of the framework, in terms of its load-displacement characteristic, and of the local behavior of joints in terms of their moment-rotation characteristics, and evaluates details about the interaction of the joint elements and how they work together in a balanced manner, during exceptional events, this study concerns the joints which are subject to the collapse and also includes the behavior of joints in the neighborhood of the collapse. The intricacy of such investigations appear from nonlinear effects associated with the outlook of joint behavior or functioning, such as structural shortcomings, large displacements and rotations, inelastic properties of steel and concrete materials, the effects between steel and concrete, and slip between concrete and structural steel, through others. The paper addresses these problems using two types of joints flush and extended end-plate with four and eight bolts and provides recommendations and reasoning for the behavioral techniques for the evaluation of joint moment-rotation response when exposed to negative and positive moments together.

• English
• Polish

Aspects related to robustness of steel frameworks with semi-rigid steel and steel-concrete composite joints are dealt with. Experimental investigations were carried out for sub-frames fabricated in technical scale. Pushdown tests for steel subframes simulated the joint ability to transfer the bending moment and axial force under a column loss scenario. Tests on composite sub-frames were arranged in two stages. The first one was related to a service stage when the slab was under a gravity load and the column to be removed supported. The gravity load was sustained in the second stage when a column loss scenario was simulated. Experiments have shown that composite flush end-plate joints may not be robust enough since their low strength under sagging bending, despite of good ductility, does not allow for the redistribution of internal forces in order to achieve the equilibrium in the residual state after static column removal. Contrary, symmetrical steel and composite joints with extended end-plates on both sides of beam flanges seem to be more robust, despite of their lesser ductility. Robust bending behaviour is possible because extended end-plate joints exhibit a better balance between the strength and rotation capacity that allows to achieve the equilibrium state in case of a static column loss event.

Progressive building collapse occurs when failure of a structural component leads to the failure and collapse of surrounding members, possibly promoting additional collapse. Global system collapse will occur if the damaged system is unable to reach a new static equilibrium configuration. The objective of this research is to identify and investigate the importance of issues related to the unexpected collapse resulting from the loss of key elements of the structure (a column or columns, for example). In this research study there are examined on the entire frame including details of the column loss scenario and also the influence of the ductility and strength of beam-to-column joints adjacent to the location of such as incident. The study also includes catenary action in beams resulting from collapse and its impact on the adjacent joints and reports on the comparison of negative and positive moments in joints. In addition, it records the important notes associated with the state of collapse and parts of this research include the conformity of numerical and analytical results, the ratio of credibility and conformity of results and the test. This thesis reports in detail on the experimental and numerical investigations of the behaviour of steel and composite joints, which aim to develop common solutions with regard to the joint semi-rigid and partial strength properties that might allow for significant rotations and the redistribution of internal forces in structural system when there was a damage to its key element such as a column. Investigations of steel and composite joints with regard to their ductile behaviour are presented. Thereby special attention is paid to shaping of …

ABSTRACT

In order to capture the effect of joint progressive stiffness degradation with the hardening effect taken into account, the three parametric continuous model is adopted hereafter for the analytical formulation. The current paper is an extension of the previous work (Gizejowski et al. 2012) giving all the details of the developed model together with a calibration procedure for basic model parameters. Experimental data used was obtained from laboratory tests carried out at the Warsaw University of Technology for beam-to-column joints of different reinforcement ratio. The results of calibration exercise as well as the values of calibrated model parameters are given for practical application.

Abstract

The paper presents studies on numerical modelling of beam-to-column joint behaviour in typical service and exceptional design situations. The complexity of such investigations arises from highly nonlinear effects associated with the prediction of joint performance, such as structural imperfections, large displacements and rotations, inelastic properties of steel and concrete, bonding effects between steel and concrete, and slip between concrete and structural steel, among others. The paper addresses these problems and provides validation of numerical modelling techniques trough comparison with experimental data for joints under hogging and sagging moments. © (2012) Trans Tech Publications.

Eurocodes [1], [2] cover presently only the so-called basic design situations where the beam-to-column joints are subjected to hogging bending with a negligible influence of the axial force. Design requirements for structural robustness in case of exceptional or extreme actions are being developed in which the joint ductility demand is one of the primary requirement [3][6]. Localized structural damage due to these actions may propagate through a large portion of a structural system causing its entire collapse or the progressive collapse process may be restricted to the relatively small region that is in proportion to the load effects caused. The latter might be provided by design ensuring the ability of transfer the so-called tying forces. Eurocodes do not give any guidelines on how to calculate the tying resistance of joints, mainly because of lack of experimental evidence on the joint ductility under extreme actions. For robust design, joints need to pose the rotation capacity required for inelastic redistribution process to take place on the so-called alternative equilibrium path. The capability of a structure to sustain local damage is evaluated by a notionally conducted removal of its column(s) and checking whether the local damage may be absorbed by the deteriorated structural system. This requires investigations conducted into the behaviour of joint responses to sagging bending accompanied by an axial tying. This paper is concerned with experimental tests of steel and steel-concrete composite sub-frames through which the beam-to-column joint behaviour in typical standard and exceptional design situations is possible to be evaluated. Problems related to the joint strength, stiffness and rotation capacity response under sagging moment in case of the column removal that simulates the frame system behaviour in an exceptional situation are addressed and conclusions drawn.