• Steel and Composite Structures
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• v.17 no.5
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• pp.735-751
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• 2014

Concrete-filled steel tube (CFT) composite columns, either circular (CCFT) or rectangular (RCFT), have many economical and aesthetic advantages but the behavior of their connections are complicated. This study aims to investigate, through an experimental program, the performance and behavior of different connections configurations between circular concrete filled steel tube columns (CCFT) and gusset plates subjected to shear and axial compression loadings. The study included seventeen connection subassemblies consisting of a fixed length steel tube and gusset plate connected to the tube end with different details tested under half cyclic loading. A notable effect was observed on the behavior of the connections due to its detailing changes with respect to capacity, failure mode, ductility, and stress distribution.

• Steel and Composite Structures
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• v.19 no.2
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• pp.467-484
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• 2015

Seismic performances of dual steel moment-resisting frames with mixed use of rigid and semi-rigid connections were investigated to control of the base shear, story drifts and the ductility demand of the elements. To this end, nonlinear seismic responses of three groups of frames with three, eight and fifteen story were evaluated. These frames with rigid, semi-rigid and combined configuration of rigid and semi-rigid connections were analyzed under five earthquake records and their responses were compared in ultimate limit state of rigid frame. This study showed that in all frames, it could be found a state of semi-rigidity and connections configuration which behaved better than rigid frame, with consideration of the base shear and story drifts criterion. Finally, some criteria were suggested to locate the best place of the semi-rigid connections for improvement of the seismic performance of steel moment-resisting frames.

• International journal of steel structures
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• v.18 no.4
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• pp.1464-1469
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• 2018

Steel frames with ductile connections have good seismic performance under strong earthquake, they are now popular for high seismic design. In order to simplify the process of numerical analysis of the steel frames with ductile connections, simplified connection models are introduced, two types of springs are placed in the simplified connection model, which can simulate deformation of the panel zone and members. 6-story-3-bay steel frames with ductile connections are simplified and carried out modal analysis, fundamental periods of the frames predicted by finite-element analysis for simplified steel frame models were compared to the results for actual frame models. 2-story steel frame with reduced beam section connections is simplified and carried out pseudo-static analysis, hysteretic curves and skeleton curves of the frame obtained by finite-element analysis for simplified steel frame model are compared to test results. The comparison show that the difference between them is small, it is reliable and effective to predict mechanical properties of the steel frame with ductile connection by finite-element analysis of simplified steel frame model.

• Steel and Composite Structures
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• v.30 no.5
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• pp.443-456
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• 2019

Although numerous researchers demonstrated the significant difference in performance between the various beam-to-column connection types, most of the previous studies in the area of infilled steel frames focused on the behaviour of frames with welded connections. Therefore, there is a need for conducting studies on infilled steel frames with other common connection types (extended endplate with and without rib stiffeners, flush endplate and shear connections). In this paper, firstly, a two-dimensional finite-element model simulating the cyclic response of infilled steel frames was presented. The infill-frame interaction, as well as the interactions between connections' components, were properly modelled. Using the previously-validated model, a parametric study on infilled steel frames with five different beam-to-column connection types, under cyclic loading, was carried out. Several parameters, including infill material, fracture energy of masonry and infill thickness, were investigated. The results showed that the infilled frames with welded connections had the highest initial stiffness and load-carrying capacity. However, the infilled frames with extended endplate connections (without rib stiffeners) showed the greatest energy dissipation capacity and about 96% of the load-carrying capacity of frames with welded connections which indicates that this type of connection could have the best performance among the studied connection types. Finally, a simplified analytical model for estimating the stiffness and strength of infilled steel frames (with different beam-to-column connection types) subjected to lateral cyclic loading, was suggested.

• Steel and Composite Structures
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• v.48 no.5
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• pp.547-564
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• 2023

This study investigates the effect of bolt preloading on the rotational stiffness of stainless steel end-plate connections. An experimental programme incorporating 11 full-scale joint specimens are carried out comparing the behaviours of fully pre-tensioned (PT) and snug-tightened (ST) flush/extended end-plate connections, made of austenitic or lean duplex stainless steels. It is observed from the tests that the presence of bolt preloading leads to a significant increase in the rotational stiffness. A parallel finite element analysis (FEA) validated against the test results demonstrates that the geometric imperfection of end-plate has a strong influence on the moment-rotation response of preloaded end-plate connections, which is crucial to explain the observed "two-stage" behaviour of these connections. Based on the data obtained from the tests and FE parametric study, the performance of the Eurocode 3 predictive model is evaluated, which exhibits a significant deviation in predicting the rotational stiffness of stainless steel end-plate connections. A modified bi-linear model, which incorporates three key properties, is therefore proposed to enable a better prediction. Finally, the effect of bolt preloading is demonstrated at the system (structure) level considering the serviceability of semi-continuous stainless steel beams with end-plate connections.

• Steel and Composite Structures
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• v.4 no.6
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• pp.453-469
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• 2004

In this article, a genetic algorithm based optimum design method is presented for non-linear steel frames with semi-rigid connections. The design algorithm obtains the minimum weight frame by selecting suitable sections from a standard set of steel sections such as European wide flange beams (i.e., HE sections). A genetic algorithm is employed as optimization method which utilizes reproduction, crossover and mutation operators. Displacement and stress constraints of Turkish Building Code for Steel Structures (TS 648, 1980) are imposed on the frame. The algorithm requires a large number of non-linear analyses of frames. The analyses cover both the non-linear behaviour of beam-to-column connection and $P-{\Delta}$ effects of beam-column members. The Frye and Morris polynomial model is used for modelling of semi-rigid connections. Two design examples with various type of connections are presented to demonstrate the application of the algorithm. The semi-rigid connection modelling results in more economical solutions than rigid connection modelling, but it increases frame drift.

• Steel and Composite Structures
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• v.22 no.2
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• pp.429-448
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• 2016

This paper presents a finite element (FE) model for predicting the behaviour of steel column-column connections under axial compression and tension. A robustness approach is utilised for the design of steel column-column connections. The FE models take into account for the effects of initial geometric imperfections, material nonlinearities and geometric nonlinearities. The accuracy of the FE models is examined by comparing the predicted results with independent experimental results. It is demonstrated that the FE models accurately predict the ultimate axial strengths and load-deflection curves for steel column-column connections. A parametric study is carried out to investigate the effects of slenderness ratio, contact surface imperfection, thickness of cover-plates, end-plate thickness and bolt position. The buckling strengths of steel column-column connections with contact surface imperfections are compared with design strengths obtained from Australian Standards AS4100 (1998) and Eurocode 3 (2005). It is found that the column connections with maximum allowable imperfections satisfy the design requirements. Furthermore, the steel column-column connections analysed in this paper can be dismantled and reused safely under typical service loads which are usually less than 40% of ultimate axial strengths. The results indicate that steel column-column connections can be demounted at 50% of the ultimate axial load which is greater than typical service load.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.335-348
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• 2014

For high-strength steel, it is difficult to be applied to flexible structural member because it have high yield ratio and low basic material's toughness. One of the great problems when using high-strength steel connections is the brittle fracture at the end of the beam member in common with general mild steel connections. In the cases of mild steel connections, it has be developed that special moment frame connection details by reinforcing structural member or improvement of welding access hole. But, it is incomplete at yet about applicability estimation of high-strength steel connections. This study is the initial step research for the applicability estimation of beam-to-column connections being applied to developed high-strength steel, HSA800. And, it studied about structural performance of the high-strength steel connections according to the details of welding access hole through full-scale test and analytical method.

• Steel and Composite Structures
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• v.17 no.6
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• pp.851-865
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• 2014

Full penetration welded steel moment-resisting frame (SMRF) structures with welded box sections are widely employed in steel bridges, where a large number of steel bridges have been in operation for over fifty years in Japan. Welding defects such as incomplete penetration at the beam-column connections of these existing SMRF steel bridge piers were observed during inspection. Previous experiments conducted by the authors' team indicate that gusset stiffeners (termed fillets in this study) at the beam-web-to-column-web joint of the beam-column connections may play an important role on the seismic performance of the connections. This paper aims to experimentally study the effect of the fillet radius on seismic performance of the connections with large welding defects. Four specimens with different sizes of fillet radii were loaded under quasi-static incremental cyclic loading, where different load-displacement relations and cracking behaviors were observed. The experimental results show that, as the size of the fillet radius increases, the seismic performance of the connections can be greatly improved.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.435-438
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• 2005

The use of new hybrid systems that combine the advantages of steel and reinforced concrete structures has gained popularity. One of these new mixed systems consists of steel beams and reinforced concrete shear wall, which represents a cost- and time-effective type of construction. A number of previous studies have focused on examining the seismic response of steel coupling beams in a hybrid wall system. However, the shear transfer of steel coupling beam-wall connections with panel shear failure has not been thoroughly investigated. The objective of this research was to investigate the seismic performance of steel coupling beamwall connections governed by panel shear failure. To evaluate the contribution of each mechanism, depending upon connection details, an experimental study was carried out The test variables included the reinforcement details that confer a ductile behaviour on the steel coupling beam-wall connection, i.e., the face bearing plates and the horizontal ties in the panel region of steel coupling beam-wall connections. It investigates the seismic behaviour of the steel coupling beams-wall connections in terms of the deformation characteristics. The results and discussion presented in this paper provide background for a companion paper that includes a design model for calculating panel shear strength of the steel coupling beam-wall connections.