• Steel and Composite Structures
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• v.10 no.5
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• pp.385-414
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• 2010

In current European Standard EN 1993, the moment-rotation characteristics of beam-to-column joints made from steel with a yield stress > 460MPa are obtained from elastic design procedures. The strength of the joint basic components, such as the column web subject to local transverse compression, is thus limited to the yield resistance rather than the plastic resistance. With the recent developments of higher strength steel grades, the need for these restrictions should be revisited. However, as the strength of the steel is increased, the buckling characteristics become more significant and thus instability phenomena may govern the design. This paper summarizes a comprehensive set of finite element parametric studies pertaining to the strength behaviour of high-strength steel unstiffened I-columns in transverse compression. The paper outlines the implementation and validation of a three-dimensional finite element model and presents the relevant numerical test results. The finite element predictions are evaluated against the strength values anticipated by the EN 1993 for conventional steel columns and recommendations are made for revising the specifications.

• Steel and Composite Structures
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• v.34 no.6
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• pp.803-818
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• 2020

Semi-rigid connections with blind bolts could solve the difficulty that traditional high strength bolts were unavailable to splice a steel/composite beam to a closed section column. However, insufficient investigations have focused on the performance of semi-rigid connection to square concrete filled double-skin steel tubular (CFDST) columns. In this paper, a component model was developed to evaluate the mechanical behavior of semi-rigid composite connections to CFDST columns considering the stiffness and strength of column face in compression and column web in shear which were determined by the load transfer mechanism and superstition method. Then, experimental investigations on blind bolted composite joints to square CFDST columns were conducted to validate the accuracy of the component model. Dominant failure modes of the connections were analyzed and this type of joint behaved semi-rigid manner. More importantly, strain responses of CFDST column web and tubes verified that stiffness and strength of column face in compression and column web in shear significantly affected the connection mechanical behavior owing to the hollow part of the cross-section for CFDST column. The experimental and analytical results showed that the CFDST column to steel-concrete composite beam semi-rigid joints could be employed for the assembled structures in high intensity seismic regions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.62-70
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• 2007

This paper reports an evaluation method on the shear strength of interior beam-column joints composed of steel beams and reinforced concrete columns(RCS). The shear strength is generally calculated by the sum of the nominal shear resistance of a steel web panel and concrete elements. In this paper, the shear strength is calculated based on the compression strut theory instead of compression field theory. Design equations presented herein are evaluated through comparison with existing experimental results. The comparisons between experimental and calculated results show an excellent agreement.

• Structural Engineering and Mechanics
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• v.73 no.6
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• pp.613-620
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• 2020

The research study is focuses on a form of all-bolted joint with the external ring stiffening plate in the prefabricated steel structure. The components are bolted at site after being fabricated in the factory. Six specimens were tested under cyclic loading, and the effects of column axial compression ratio, concrete-filled column, beam flange sub plate, beam web angle cleats, and spliced column on the failure mode, hysteretic behavior and ductility of the joints were analyzed. The results shown that the proposed all-bolted joint with external ring stiffening plate performed high bearing capability, stable inflexibility degradation, high ductility and plump hysteretic curve. The primary failure modes were bucking at beam end, cracking at the variable section of the external ring stiffening plate, and finally welds fracturing between external ring stiffening plate and column wall. The bearing capability of the joints reduced with the axial compression ratio increased. The use of concrete-filled steel tube column can increase the bearing capability of joints. The existence of the beam flange sub plate, and beam web angle cleat improves the energy dissipation, ductility, bearing capacity and original rigidity of the joint, but also increase the stress concentration at the variable section of the external reinforcing ring plate. The proposed joints with spliced column also performed desirable integrity, large bearing capacity, initial stiffness and energy dissipation capacity for engineering application by reasonable design.

• Advances in Computational Design
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• v.3 no.1
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• pp.71-86
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• 2018

Thin-walled cross-sections can be optimized to enhance their resistance and progress their behaviour, leading to more competent and inexpensive structural system. The aim of this study is to afford a methodology that would facilitate progress of optimized cold formed steel (CFS) column section with maximum ultimate strength for practical applications. The proposed sections are designed to comply with the geometrical standards of pre-qualified column standards for CFS structures as well as with the number of industrialized and practical constraints. The stiffening evaluation process of CFS lipped channel columns, a five different cross section are considered. The experimental strength and behaviour of the proposed sections are verified by using the finite element analysis (FEA). A series comprehensive parametric study is carried out covering a wide range of section slenderness and overall slenderness ratio of the CFS column with and without intermediate web stiffeners. The ultimate strength of the sections is determined based on the Direct Strength Specification and other design equation available from the literature for CFS structures. A modified design method is proposed for the DSM specification. The results indicate that the CFS column with complex edge and intermediate web stiffeners provides an ultimate strength which is up to 78% higher than standard optimized shapes with the same amount of cross sectional area.

• Steel and Composite Structures
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• v.39 no.3
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• pp.337-352
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• 2021

The study presented experimental and numerical investigation on the seismic performance of steel reinforced concrete (SRC) L-shaped column- reinforced concrete (RC) beam joints. Various parameters described as steel configuration form, axial compressive ratio, loading angle, and the existence of slab were examined through 4 planar joints and 7 spatial joints. The characteristics of the load-displacement response included the bearing capacity, ductility, story drift ratio, energy-dissipating capacity, and stiffness degradation were analyzed. The results showed that shear failure and flexural failure in the beam tip were observed for planar joints and spatial joint, respectively. And RC joint with slab failed with the plastic hinge in the slab and bottom of the beam. The results indicated that hysteretic curves of spatial joints with solid-web steel were plumper than those with hollow-web specimens. The capacity of planar joints was higher than that of space joints, while the opposite was true for energy-dissipation capacity and ductility. The high compression ratio contributed to the increase in capacity and initial stiffness of the joint. The elastic and elastic-plastic story deformation capacity of L-shaped column frame joints satisfied the code requirement. A design formula of joint shear resistance based on the superposition theory and equilibrium plasticity truss model was proposed for engineering application.

• Steel and Composite Structures
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• v.47 no.3
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• pp.437-450
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• 2023

A half open cross section built-up column, namely cold-formed thin-walled steel built-up column with 12-limbsection (CTSBC-12) is put forward. To deeply reveal the mechanical behaviors of CTSBC-12 under axial compression and put forward its calculation formula of axial bearing capacity, based on the previous axial compression experimental research, the finite element analysis (FEA) is conducted on 9 CTSBC-12 specimens, and then the variable parameter analysis is carried out. The results show the FEA is in good agreement with the experimental research, the ultimate bearing capacity error is within 10%. When the slenderness ratio is more than 96.54, the ultimate bearing capacity of CTSBC-12 decreases rapidly, and the failure mode changes from local buckling to global buckling. With the local buckling failure mode unchanged, the ultimate bearing capacity decreases gradually as the ratio of web height to thickness increases. Three methods are used for calculating the ultimate bearing capacity, the direct strength method of AISI S100-2007 gives result of ultimate axial load which is closest to the test and FEA results. But for simplicity and practicality, a simplified axial bearing capacity formula is proposed, which has better calculation accuracy with the slenderness ratio changing from 30 to 100.

• Journal of Korean Society of Steel Construction
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• v.17 no.4 s.77
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• pp.431-438
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• 2005

A steel-concrete composite column is a recently developed composite system in which the two opposite flanges of the H-shape section are connected by welded links, and the vacant space enclosed by the flanges, web, and links is filled with concrete. Previous experiments on the SC composite column were performed to evaluate its compression and bending and shear strengths, respectively, and they showed fairly good results. In addition to thesestudies, it may be necessary to evaluate the flexural-axial capacity of an SC composite column, because itscolumn members are generally subjected to axial force and bending moment at the same time. In this study, the bending strength of an SC composite column subjected to axial compression force was investigated experimentally. The results of the study showed that the AISC-LRFD provisions representedexcessively low values compared with those of the ACI, Eurocode-4, and Japan Code provisions. The Eurocode-4 provisions represented reasonable evaluations of the strength of the SC composite column composed of a non-compact section.

• Steel and Composite Structures
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• v.1 no.2
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• pp.245-268
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• 2001

The analysis of steel-concrete composite joints presents some particular aspects that increase their complexity when compared to bare steel joints. In particular, the influence of slab reinforcement and column concrete encasement clearly change the moment-rotation response of the joint. Starting from an energy approach developed in the context of steel joints, an extension to composite joints is presented in this paper that is able to provide closed-form analytical solutions. In addition, the possibility of tri-linear or non-linear component behaviour is also incorporated in the model, enabling adequate treatment of the influence of cracked concrete in tension and the softening response of the column web in compression. This methodology is validated through comparison with experimental tests carried out at the University of Coimbra.

• Steel and Composite Structures
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• v.45 no.1
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• pp.51-66
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• 2022

This paper presents the axial compression behavior of partially encased composite (PEC) columns using H-shaped structural steel. In the experimental program, a total of eight PEC columns with H-shaped steel sections of different flange and web slenderness ratios were tested to investigate the interactive mechanism between steel and concrete. The test results showed that the PEC columns could sustain the load well beyond the peak load provided that the flange slenderness ratio was not greater than five. In addition, the previous analytical model was extended to predict the axial load-strain relationships of the PEC columns with H-shaped steel sections. A good agreement between the predicted load-strain relationships and test data was observed. Using the analytical model, the effects of compressive strength of concrete (21 to 69 MPa), yield strength of steel (245 to 525 MPa), slenderness ratio of flange (4 to 10), and slenderness ratio of web (10 to 25) on the interactive mechanism (K_h = confinement factor for highly confined concrete and K_w = reduction factor for steel web) and ductility index (DI = ratio between strain at peak load and strain at proportional load) were assessed. The numerical results showed that the slenderness of steel flange and yield strength of steel significantly influenced the compression behavior of the PEC columns.