• Steel and Composite Structures
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• 제43권5호
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• pp.673-688
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• 2022

Post-earthquake fire is a major threat since most structures are designed allowing some damage during strong earthquakes, which will expose a more vulnerable structure to post-earthquake fire compared to an intact structure. A series of experimental research on steel-concrete composite beam-to-column joints subjected to fire after cyclic loading has been carried out and a clear reduction of fire resistance due to the partial damage caused by cyclic loading was observed. In this paper, by using ABAQUS a robust finite element model is developed for exploring the performance of steel-concrete composite joints in post-earthquake fire scenarios. After validation of these models with the previously conducted experimental results, a comprehensive numerical analysis is performed, allowing influential parameters affecting the post-earthquake fire behavior of the steel-concrete composite joints to be identified. Specifically, the level of pre-damage induced by cyclic loading is regraded to deteriorate mechanical and thermal properties of concrete, material properties of steel, and thickness of the fire protection layer. It is found that the ultimate temperature of the joint is affected by the load ratio while fire-resistant duration is relevant to the heating rate, both of which change due to the damage induced by the cyclic loading.

• Steel and Composite Structures
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• 제35권2호
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• pp.261-278
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• 2020

In steel-concrete composite beams, to improve the cracking resistance of the concrete slab in the hogging moment region, a new type of connector in the interface, named uplift-restricted and slip-permitted screw-type (URSP-S) connector has been proposed. This paper focuses on the behavior of steel-concrete composite beams with URSP-S connectors. A total of three beam specimens including a simply supported beam with URSP-S connectors and two continuous composite beams with different connectors arrangements were designed and tested. More specifically, one continuous composite beam was equipped with URSP-S connectors in negative moment region and traditional shear studs in other regions. For comparison, the other one was designed with only traditional shear studs. The failure modes, crack evolution process, ultimate capacities, strain responses at different locations as well as the interface slip of the three tested specimens were measured and evaluated in-depth. Based on the experimental study, the research findings indicate that the larger slip deformation is allowed while using URSP-S connectors. Meanwhile, the tensile stress reduces and the cracking resistance of the concrete slab improves accordingly. In addition, the overall stiffness and strength of the composite beam become slightly lower than those of the composite beam using traditional shear studs. Moreover, the arrangement suggestion of URSP-S connectors in the composite beam is discussed in this paper for its practical design and application.

• Steel and Composite Structures
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• 제9권4호
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• pp.349-366
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• 2009

The composite slim beam has become popular throughout Europe in recent years and has also been used on some projects in China. With its steel section encased in a concrete slab, the steel-concrete composite slim beam can provide the floor construction with minimum depth and high fire resistance. However, the design method of the T-shape steel-concrete composite beam is no longer applicable to the composite slim beam with deep deck for its special construction, of which the present design models are not available but mainly depend on experiences. The elevation of the flexural stiffness and bending capacity of composite slim beams with deep deck is rather complicated, because the influences of many factors should be taken into account, such as the variable section dimensions, development of cracks and non-linear characteristics of concrete, etc. In this paper, experimental investigations have been conducted into the flexural behavior of two specimens of simply supported composite slim beam with deep deck. The emphases were laid on the bonding force on the interface between steel beam and concrete, the stress distribution of beam section, the flexural stiffness and bending capacity of the composite beams. Based on the experimental results, the reduction factor of equivalent stress distribution in concrete flange is suggested, and the calculation method of flexural stiffness and bending capacity of simply supported slim beams are proposed.

• Advances in concrete construction
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• 제12권5호
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• pp.399-409
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• 2021

The existing method to improve the coordination performance of the inner and outer parts of concrete-encased concrete-filled steel tube (CFST) composite columns by increasing the volume-stirrup ratio causes difficulties in construction due to over-dense stirrups. Thus, this paper proposes an open polygonal composite stirrup with high strength and high ductility CRB600H reinforced rebar, and seventeen specimens were constructed, and their axial compressive performance was tested. The main parameters considered were the volume-stirrup ratio, the steel tube size, the stirrup type and the stirrup strength. The test results indicated: For the specimens restrained by open octagonal composite stirrups, compared with the specimen of 0.5% volume-stirrup ratio, the compressive bearing capacity increased by 14.6%, 15.7% and 21.5% for volume-stirrup ratio of 0.73%, 1.07% and 1.61%, respectively. For the specimens restrained by open composite rectangle stirrups, compared with the specimen of 0.79% volume-stirrup ratio, the compressive bearing capacity increased by 7.5%, 6.1%, and -1.4% for volume-stirrup ratio of 1.12%, 1.58% and 2.24%, respectively. The restraint ability and the bearing capacity of the octagonal composite stirrup are better than other stirrup types. The specimens equipped with open polygonal composite stirrup not only had a higher ductility than those with the traditional closed-loop stirrup, but they also had a higher axial bearing capacity than those with an HPB300 strength grades stirrup. Therefore, the open composite stirrup can be used in practical engineering. A new calculation method was proposed based on the stress-strain models for confined concrete under different restrain conditions, and the predicted value was close to the experimental value.

• Coupled systems mechanics
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• 제9권5호
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• pp.473-498
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• 2020

This paper presents a careful theoretical investigation into interfacial stresses in reinforced concrete foundation beam repairing with composite plate. The essential issue in the analysis of reinforced structures with composite materials is to understand the individual behaviour of each material and its interaction with the remaining ones. The present model is based on equilibrium and deformations compatibility requirements in and all parts of the repaired RC foundation beam, i.e., the reinforced concrete foundation beam, the composite plate and the adhesive layer. The theoretical predictions are compared with other existing solutions, By comparisons between the existing solutions and the present new solution enable a clear appreciation of the effects of various parameters such as the geometric characteristics and mechanical properties of the components of the repaired beam, as well as the geotechnical stresses of the soil are considered. This research is helpful for the understanding on mechanical behaviour of the interface and design of the composite-concrete hybrid structures.

• Steel and Composite Structures
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• 제14권5호
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• pp.493-509
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• 2013

Bending behavior of reinforced concrete slabs encased over shallow I-sections at different levels of compression heads were investigated in present study. 1500 mm long I-sections were used to create composite slabs. Compression heads of monolithic experimental members were encased at different levels into the concrete slabs. Shear connections were welded over some of the I-sections. The testing was carried out in accordance with the principles of four-point loading. Results revealed decreasing load bearing and deflection capacities of composite beams with increasing encasement depths into concrete. Mechanical properties of concrete and reinforcing steel were also examined. Resultant stresses calculated for composite beams at failure were found to be less than the yield strength of steel beams. Test results were discussed with regard to shear and slip effect.

• Steel and Composite Structures
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• 제10권2호
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• pp.169-185
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• 2010

The present work describes the experimental tests on steel and lightweight concrete composite beams performed at University of Minho, Portugal. The study involves tests on simply supported composite beams of 4.5 m span, with the same geometrical disposition, supports and materials. The geometrical configuration for the cross section and supports is identical for every beam, varying the shear connectors' distribution and the loading conditions. Headed studs are used to provide the connection between the steel profile and the concrete slab. The parameters in study are the stud disposition and the load distribution. The main objective is to describe the composite beams behaviour, focused on its connection, and to analyse the contribution of the different components to the beams load and deformation capacity. All the tests explored the beams maximum load and deformation capacity and different types of failure were observed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.355-362
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• 2001

This study deals with cracking control of concrete deck in steel-concrete composite bridges according to the concrete slab casting sequences. In correlation studies between casting sequences, time dependent effects of concrete creep and shrinkage are implemented in the analytical model. Finally, the methods of cracking control in terms of concrete slump and relative humidity are suggested to prevent early transverse cracking of concrete slab.

• Steel and Composite Structures
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• 제21권5호
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• pp.981-997
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• 2016

To avoid the cracks of cast-in-place concrete in shear pockets and seams in the traditional composite beam with precast decks, this paper proposed a new type of prefabricated steel truss-concrete composite beam (ab. PSTC beam) with pre-embedded shear studs (ab. PSS connector). To study the initial cracking load of concrete deck, the development and distribution laws of the cracks, 3 PSTC beams were tested under hogging moment. And the crack behavior of the deck was compared with traditional precast composite beam, which was assembled by shear pockets and cast-in-place joints. Results show that: (i) the initial crack appears on the deck, thus avoid the appearance of the cracks in the traditional shear pockets; (ii) the crack of the seam appears later than that of the deck, which verifies the reliability of epoxy cement mortar seam, thus solves the complex structure and easily crack behavior of the traditional cast-in-place joints; (iii) the development and the distribution laws of the cracks in PSTC beam are different from the conventional composite beam. Therefore, in the deduction of crack calculation theory, all the above factors should be considered.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.485-495
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• 2018

This paper presents the results of an experimental study on the structural performance of an innovative GFRP-concrete composite beam construction, which is reinforced with longitudinal GFRP pultruded box-profile and transverse steel stirrups. GFRP perfobond (PBL) shear connectors are employed to enhance the bonding performance between the GFRP profile and the concrete portion. To investigate the shear and flexural performance of this composite system, eight specimens were designed and tested under three-point and four-point bending. The main variables were the height of the composite beam and the shear span-to-depth ratio. The test results indicated that bonding cracks did not occur at the interface between the GFRP profile and the concrete until the final stage of the test. This shows that the specimens performed well as composite beams during the test and that the GFRP PBL connectors were reliable. Based on the test results, two calculation methods were used to determine the flexural and shear capacity of the composite beams. A comparative study of the test and theoretical results suggests that the proposed methods can reasonably predict both the flexural and shear capacities of the specimens, whereas the provisions of ACI 440 are relatively conservative on both counts.