• Steel and Composite Structures
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• v.11 no.4
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• pp.291-305
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• 2011

The new structure consisting of continuous compound spiral hoop reinforced concrete (CCSHRC)column and steel concrete composite (SCC) beam has both the advantages of steel structures and concrete structures. Two types of beam-to-column connections applied in this structural system are presented in this paper. The connection details are as follows: the main bars in beam concrete pass through the core zone for both types of connections. For connecting bar connection, the steel I-beam webs are connected by bolts to a steel plate passing through the joint while the top and bottom flanges of the beams are connected by four straight and two X-shaped bars. For bolted end-plate connection, the steel I-beam webs are connected by stiffened extended end-plates and eight long shank bolts passing through the core zone. In order to study the seismic behaviour and failure mechanisms of the connections, quasi-static tests were conducted on both types of full-scale connection subassemblies and core zone specimens. The load-drift hysteresis loops show a plateau for the connecting bar connection while they are excellent plump for bolted end-plate connection. The shear capacity formulas of both types of connections are presented and the values calculated by the formula agree well with the test results.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.49-52
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• 2004

In this studies, Dapped End Beams(DEB) having disturbed regions were designed by using strut tie model, and the main purpose of this paper is that whether T-headed bars and Steel fibers will be present or not. The ability of DEB with T-headed bars have a superior performance rather than others, such as improved ductility, larger energy adsorption and enhanced post-peak load carrying capability. The capacity of DEB with steel fibers also show increase of ductility, shear strength, fatigue strength and crack. Each DEB with both headed bars and steel fibers, headed bars, and steel fibers as a substitute reinforced steel in the disturbed regions and a DEB with only stirrup and tie reinforced steel were comparable. In contrast, the headed bar stirrups, the tie headed bars and the reinforced steel fibers did not lose their anchorage and hence were able to develop strain hardening and also served to delay buckling of the flexural compression steel. Excellent load-deflection predictions were obtained by increasing the tension stiffening effect to account for high load effects.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.675-682
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• 2002

The beam of composite structure composed of the RC structure in the end part and steel structure in the central palt were investigated during cyclic loading, in order to evaluate strength, stiffness, and deformational capacity. The parameters used in this study include the amount of reinforced steel bar between the steel beam and RC structure and the existence of the sticking plate. Test results showed that all specimens had stabilized hysteresis loops. Likewise, the specimens with sticking plate had higher load-carrying capacity compared with the one without it. In addition, the stiffness of the composite structure was higher than the steel structure. All specimens also showed good rotational capacity.

• Journal of Korean Society of Steel Construction
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• v.14 no.3
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• pp.413-421
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• 2002

This study sought to understand the mechanical behavior according to the shape of the connecting part of the hybrid beam. This part is composed of central steel. with the end reinforced by concrete in the experiment of cyclic loading. The experimental result was compared and verified with the ultimate strength formula. Likewise, the composite effect and the effectiveness of seismic capacity and stress transmission were examined. The types of each setup were as follows: main bars by welding type, reinforcing by end-plate type, reinforcing by shear connector type, and shear connector type. Results showed that the reinforcing by end-plate type and the shear connector type had excellent strength and seismic capacity as well as better stress transmission. This was due to the unity between reinforced concrete and the steel's connecting part. However, the experimental result was somehow different from the previously established ultimate strength formula. Thus, a definite ultimate strength formula is required.

• Computers and Concrete
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• v.10 no.1
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• pp.59-78
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• 2012

Although the effect of corrosion of reinforcing bar on the shear behavior of the reinforced concrete (RC) beam had been simulated by tests of the beam with unbonded, half-exposed or whole-exposed tensile steel reinforcements as well as defective stirrup anchorages, theoretical methods to accurately predict remaining capacity of this kind of RC beams, especially shear capacity, are still lacking. Considering the possible position of the critical inclined crack, the actual pattern of strains in the concrete body within the partial length and the proposed compatibility condition of deformations of the RC beam, shear strength of the RC beam with unbonded or exposed tensile steel reinforcements and/or defective stirrup anchorages is predicted. Comparison between the model's predictions with the experimental results published in the literature shows the practicability of the proposed model. Influence of the length of unbonded or exposed tensile steel reinforcements and the percentage of stirrups lacked end anchorages on the shear strength of the RC beam is discussed. It is concluded that, the shear strength of the RC beam with unbonded or exposed tensile steel reinforcements and/or defective stirrup anchorages is greatly influenced by the length of unbonded or exposed tensile steel reinforcements and the percentage of stirrups lacked end anchorages, this influence can be adverse, insignificant or even favourable, dependent on the given parameters of the corresponding normal bonded RC beam.

• Steel and Composite Structures
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• v.48 no.5
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• pp.599-610
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• 2023

To avoid debonding failure, a novel type of hybrid anchorage (HA) is proposed in this study that uses a slotted plate to lock the ends of the fiber-reinforced polymer (FRP) sheet in addition to the usual bonding over the substrate of the strengthened member. An experimental investigation was performed on three groups of RC beams, which differed from one another in either concrete strength or steel reinforcement ratio. The test results indicate that the end self-locking of the CFRP sheet can improve the failure ductility, ultimate capacity of the beams and its utilization ratio. Although intermediate debonding occurred in all the strengthened beams, it was not a fatal mode of failure for the three specimens with end anchorage. Among them, FRP rupture occurred in the beam with higher concrete strength and lower steel reinforcement ratio, whereas the other two failed by concrete crushing. The beam strengthened by HA obtained a relatively high percentage of increase in ultimate capacity when the rebar ratio or concrete strength decreased. The expressions in the literature were inspected to calculate the critical loads at intermediate debonding, FRP rupturing and concrete crushing after debonding for the strengthened beam. Then, the necessity of further research is addressed.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.681-690
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• 2000

Recently, a long span is often required for the spacious building. Therefore the increase of stiffness is necessary to prevent floor vibration and control deformation of the building under earthquake and wind loads. For this purpose, steel beams with stiffened ends by reinforced concrete are effective. To realize such an effective reinforcement method, the smoothening of bending and shear stress transmission at the boundaries between middle-part of the steel beam and both end-parts of the steel beam with stiffened ends by reinforced concrete is required. Therefore, the fixed plate was installed at the boundary with the view of transferring the stress smoothly. This paper evaluates the method of effective transmission of bending and shear stress through the numerical analysis that is based on advanced experimental tests.

• Structural Engineering and Mechanics
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• v.88 no.5
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• pp.481-492
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• 2023

The past earthquakes revealed the importance of the design of moment-resisting reinforced concrete framed structures with ductile behavior. Due to seismic activity, failures in framed structures are widespread in beam-column joints. Hence, the joints must be designed to possess sufficient strength and stiffness. This paper investigates the effects of fibers on the ductility of hybrid fiber reinforced self-compacting concrete (HFRSCC) when subjected to seismic actions; overcoming bottlenecks at the beam-column joints has been studied by adding low modulus sisal fiber and high modulus steel fiber. For this, the optimized dose of hooked end steel fiber content (1.5%) was kept constant, and the sisal fiber content was varied at the rate of 0.1%, up to 0.3%. The seismic performance parameters, such as load-displacement behavior, ductility, energy absorption capacity, stiffness degradation, and energy dissipation capacity, were studied. The ductility factor and the cumulative energy dissipation capacity of the hybrid fiber (steel fiber, 1.5% and sisal fiber, 0.2%) added beam-column joint specimen is 100% and 121% greater than the control specimen, respectively. And also the stiffness of the hybrid fiber reinforced specimen is 100% higher than the control specimen. Thus, the test results showed that adding hybrid fibers instead of mono fibers could significantly enhance the seismic performance parameters. Therefore, the hybrid fiber reinforced concrete with 1.5% steel and 0.2% sisal fiber can be effectively used to design structures in seismic-prone areas.

• Computers and Concrete
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• v.21 no.3
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• pp.299-310
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• 2018

When reinforced concrete structures are subjected to strong seismic forces, their beam-column connections are very susceptible to be damaged during the earthquake event. Consequently, structural designers try to fit an important quantity of steel reinforcement inside the connection, complicating its construction without a clear justification for this. The aim of this work is to evaluate -and demonstrate- numerically how the quantity and the array of the internal steel reinforcement influences on the nonlinear response of the RC beam-column connection. For this, two specimens (extracted from an experimental test of 12 RC beam-column connections reported in literature) were modeled in the Finite Element code FEAP considering different stirrup's arrays. The nonlinear response of the RC beam-column connection is evaluated taking into account the nonlinear thermodynamic behavior of each component: a damage model is used for concrete; a classical plasticity model is adopted for steel reinforcement; the steel-concrete bonding is considered perfect without degradation. At the end, the experimental responses obtained in the tests are compared to the numerical results, as well as the distribution of shear stresses and damage inside the concrete core of the beam-column connection, which are analyzed for a low and high state of confinement.

• Earthquakes and Structures
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• v.22 no.2
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• pp.203-218
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• 2022

In this paper, quasi-static tests were carried out on three prefabricated reinforced concrete column-steel beam (RCS) sub-assemblages with floor slabs and one comparison specimen without floor slab. The effects of axial compression and floor slab on the seismic performance were studied, and finite element simulations were conducted using ABAQUS. The results showed that the failure of prefabricated RCS sub-assemblages with floor occurred as a joint beam and column failure mode, while failure of sub-assemblages without floor occurred due to beam plastic hinge formation. Compared to the prefabricated RCS sub-assemblages without floor slab, the overall stiffness of the sub-assemblages with floor slab was between 19.2% and 45.4% higher, and the maximum load bearing capacity increased by 26.8%. However, the equivalent viscosity coefficient was essentially unchanged. When the axial compression ratio increased from 0.24 to 0.36, the hysteretic loops of the sub-assemblages with floor became fuller, and the load bearing capacity, ductility, and energy dissipation capacity increased by 12.1%, 12.9% and 8.9%, respectively. Also, the initial stiffness increased by 10.2%, but the stiffness degradation accelerated. The proportion of column drift caused by beam end plastic bending and column end bending changed from 35% and 46% to 47% and 36%, respectively. Comparative finite element analyses indicated that the numerical simulation outcomes agreed well with the experimental results.