• Steel and Composite Structures
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• v.16 no.2
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• pp.157-185
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• 2014

This paper examines the behaviour of two types of practical open beam-to-tubular column connection details subjected to combined moment, axial and/or shear loads. Detailed continuum finite element models are developed and validated against available experimental results, and extended to deal with flexural, axial and shear load interactions. A numerical investigation is then carried out on the behaviour of selected connections with different stiffness and strength characteristics under various load combination scenarios. The influence of applied levels of axial tensile or compressive loads on the bending stiffness and capacity is examined and discussed. Additionally, the interaction effects between shear forces and co-existing bending and axial loads are examined and shown to be comparatively insignificant in terms of stiffness and capacity in most cases. It is also shown that the range of connections considered in this paper can provide rotational ductility levels in excess of those required under typical design scenarios. Based on these findings, a simplified component-based representation is proposed and described, and its ability to represent the connection response under combined loading is verified using results from detailed numerical simulations.

• Structural Monitoring and Maintenance
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• v.4 no.3
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• pp.237-253
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• 2017

Among various structural health monitoring technologies, impedance-based damage detection has been recognized as a promising tool for diagnosing critical members of civil structures. Since the piezoelectric transducers used in the impedance-based technique should be bonded to the surface of the structure using bonding layers (e.g., epoxy layer), it is hard to maintain the as-built condition of the bonding layers and to reconfigure the devices if needed. This study presents an experimental investigation by using magnetically attached PZT-interface for the impedance-based damage detection in bolted girder connections. Firstly, the principle of the impedance-based damage detection via the PZT-interface device is outlined. Secondly, a PZT-interface attachment method in which permanent magnets are used to replace the conventional bonding layers is proposed. Finally, the use of the magnetic attraction for the PZT-interface is experimentally evaluated via detecting the bolt-loosening events in a bolted girder connection. Also, the sensitivity of impedance signatures obtained from the PZT-interface is analyzed with regard to the interface's material.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.55-63
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• 2018

Recently, the use of duplex stainless steel which with a two-phase microstructure (equal mixture of ferrite and austenite) has been increased in a variety of industrial fields due to higher strength leading to weight saving, greater corrosion resistance(particularly, stress corrosion cracking) and lower price. However, currently, stainless steels are not included in the structural materials of Korean Building Code and corresponding design standards are not specified. In this paper, experimental studies have been performed to investigate the structural behaviors of duplex stainless steel (STS329FLD) bolted connection with two bolts for providing the design data. Main variables are shear connection type (single shear and double shear) and end distance parallel to the direction of applied force. Fracture modes at the final step of test were classified into typical block shear fracture, tensile fracture and curling. Curling occurrence in single shear connection led to ultimate strength drop by up to 20%. Test strengths were compared with those by current design specifications such as AISC/AISI/KBC, EC3 and AIJ and proposed equations by existing studies. For specimens with no curling, Clement & Teh's equation considering the active shear plane provided a higher strength estimation accurancy and for specimens with curling, Kim & Lim's equation considering strength reduction by curling was also overly unconservative to predict the ultimate strength of curled connections.

• Steel and Composite Structures
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• v.20 no.3
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• pp.501-512
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• 2016

High-strength structural bolts have been utilized for beam-to-column connections in steel-framed structural buildings. Failure of these components may be caused by the bolt shank fracture or threads stripping-off, documented in the literature. Furthermore, these structural bolts are galvanized for corrosion resistance or quenched-and-tempered in the manufacturing process. This paper adopted the finite element simulation to demonstrate discrete mechanical performance for these bolts under tensile loading conditions, the coated and uncoated numerical model has been built up for two numerical integration methods: explicit and implicit. Experimental testing and numerical methods can fully approach the failure mechanism of these bolts and their ultimate load capacities. Comparison has also been conducted for two numerical integration methods, demonstrating that the explicit integration procedure is also suitable for solving quasi-static problems. Furthermore, by using precise bolt models in T-Stub, more accurately simulate the mechanical behavior of T-Stub, which will lay the foundation of the mechanical properties of steel bolted joints.

• Journal of Korean Society of Steel Construction
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• v.16 no.3 s.70
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• pp.365-375
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• 2004

This paper presents the numerical results in strength and stress distribution behavior for the connections of corrugated steel plates (CSP). The results obtained using the finite element method indicate that the CSP with =30mm of longitudinal edge lap, by the current standard specification, has very conservative values. The results also indicate the difference of strength behavior from the bolt arrangement. The strength behavior of standard corrugated type with staggered holes is only affected by circumferential edge lap, but the edge lap and bolthole spacing have an effect on the strength behavior for the deeply corrugated type with parallel holes. Based on these results, this paper examines the current specification of the connections for CSP.

• Journal of Korean Society of Steel Construction
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• v.28 no.6
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• pp.467-476
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• 2016

For the connections between modular units in modular buildings, the bolted joints with connector plates are used commonly. The strength of structure is determined by the weakest part of structure and the connections may be weaker than the members being joined. Therefore, to check the safety of modular building, the structural performance of connections between modular units as well as that of beam-to-column connections should be evaluated. In this study, the behavior of module to module connection with straight and cross shaped connector plates is investigated by lateral cyclic tests according to KBC2009 0722.2.4 which shall be conducted by controlling the story drift angle in the width and the longitudinal direction respectively. All of test results generally show the stable ductile behavior up to 0.04rad drift levels and the tests in longitudinal direction show a superior energy dissipation per cycle in each of the load steps. However, the straight shaped connector plates have the degradation of stiffness with cyclic loading and the larger drift angle of column than the cross shaped connector plates.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.737-745
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• 2004

In general, most of the beam-to-column connections for steel structures are regarded as either rigid connections or pin connections. Recently, the concept of a semi-rigid connection was introduced for a correct analysis of steel structures. Several experimental and theoretical researches have been performed regarding the structural behaviors of frames and buildings with semi-rigid connections. The results are not well known, and structural frame/building has not been designed to introduce the concept of semi-rigid connections between a beam and column until this time. To resolve this, this research depends on design specifications prepared by other advanced countries for the design of buildings with semi-rigid connections. Such a specification, however, should incorporate domestic characteristics of steel material properties and load conditions. This paper deals with structural capacities and deformable behaviors for a split-T tensile connection with F10T high-strength bolts to investigate the structural characteristics of semi-rigid frames. The experimental parameters include the thickness of T-flanges, painted or not, preloaded or not, and load pushover pattern. A total of 20 specimens were fabricated and tested with a 300-ton UTM. The structural capacities and behavior for split-T tensile connections were evaluated on each research parameter.

• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.325-335
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• 2005

This study tackles the development of an improved detail of partially restrained CFT square column-to-beam connection and the evaluation of its mechanical behavior under monotonic loading. The connection is designed to strengthen shearing capacity at the bottom of the connection due to the ultimate behavior of PR-CC by its detail of the bottom connection and simplify the fabrication process. The suggested connection is the welded bottom beam flange connection(M-2) and is compared with the existing PR-CC of bolted seat angle connection(M-1). Two specimens were fabricated in actual size and tested under monotonic loading. Based on the test results, the welded bottom beam flange connection exhibited about 85% of the stiffness of steel beam. It was similar to the bolted seat angle connection and behaved as PR-CC. The specimen of the supposed connection type failed at the shear connection of web but was similar to the bolted seat angle connection until the failure. It obtained sufficient stiffness and capacity through the reinforcingsteel and the capacity and deformational ability equivalent to the full-plastic moment through the anchor inside the steel tube at the web connection. So, it can be said that the suggested connection exhibits sufficient ductile behavior.

• Steel and Composite Structures
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• v.8 no.5
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• pp.403-421
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• 2008

The design provisions for semi-rigid steel frames have been incorporated in codes of practice for steel structures. In order to do the same, it is necessary to know the experimental moment-relative rotation (M-${\theta}_r$) behaviour of beam-to-column connections. In spite of numerous publications and collection of several connection databases, there is no unified approach for the semi-rigid design of steel frames. Amongst the many connection models available, the Frye-Morris polynomial model, with its limitations reported in the literature, is simple to adopt at least for the linear design space. However this model requires more number of connection tests and regression analyses to make it a realistic prediction model. In this paper, 3D nonlinear finite element (FE) analysis of beam-column connection specimens, carried out using ABAQUS software, for evaluating the M-${\theta}_r$ behaviour of semi-rigid top and seat-angle (TSA) bolted connections are described. The finite element model is validated against experimental behaviour of the same connection with regard to their moment-rotation behaviour, stress distribution and mode of failure of the connections. The calibrated FE model is used to evaluate the performance of the Frye-Morris polynomial model. The results of the numerical parametric studies carried out using the validated FE model have been used in proposing modifications to the Frye-Morris model for TSA connection in terms of the powers of the size parameters.

• Steel and Composite Structures
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• v.2 no.2
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• pp.147-160
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• 2002

This paper summarises results of the research performed at the Department of Steel Structures and Structural Mechanics from the "Politehnica" University of Timisoara, Romania, in order to evaluate the performance of beam-to-column extended end plate connections for steel and composite joints. It comprises laboratory tests on steel and composite joints, and numerical modelling of joints, based on tests. Tested joints are double-sided, with structural elements realised of welded steel sections. The columns are of cruciform cross-section, while the beams are of I section. Both monotonic and cyclic loading, symmetrically and antisymmetrically, has been applied. On the basis of tested joints, a refined computer model has been calibrated using a special connection element of the computer code DRAIN 2DX. In this way, a static/dynamic structural analysis of framed structures with real characteristics of the beam to column joints is possible.