• Computers and Concrete
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• 제8권1호
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• pp.59-70
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• 2011

A theoretical model known as the modified rotating-angle softened-truss model (MRA-STM), which is a modification of Rotating-Angle Softened-Truss Model and Modified Compression Field Theory, is presented for the analysis of reinforced concrete membranes in shear. As an application, shear strength and behaviour of reinforced concrete exterior beam-column joints are analysed using the MRA-STM combining with the deep beam analogy. The joints are considered as RC panels and subjected to vertical and horizontal shear stresses from adjacent columns and beams. The strut and truss actions in a beam-column joint are represented by the effective transverse compression stresses and a softened concrete truss in the proposed model. The theoretical predictions of shear strength of reinforced concrete exterior beam-column joints from the proposed model show good agreement with the experimental results.

• Steel and Composite Structures
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• 제30권6호
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• pp.591-601
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• 2019

This research study investigates experimentally and analytically the axial compressive behaviour of Concrete Filled Fiber Reinforced Polymer Tube (CFFT) columns with and without Fiber Reinforced Polymer (FRP) bars. The experimental program comprises five circular columns of 204-206 mm outer diameter and 800-812 mm height. All columns were tested under concentric axial compressive loads. It was found that CFFT columns with and without FRP bars achieved higher peak axial compressive loads and corresponding axial deformations than conventional steel reinforced concrete (RC) column. The contribution of FRP bars was about 12.1% of the axial compressive loads carried by CFFT columns reinforced with FRP bars. Axial load-axial deformation ($P-{\delta}$) curves of CFFT columns were analytically constructed, which mapped well with the experimental $P-{\delta}$ curves. Also, an equation was proposed to predict the axial compressive load capacity of CFFT columns with and without FRP bars, which adequately considers the contributions of the circumferential confinement provided by FRP tubes and lower ultimate strength of FRP bars in compression than in tension.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.194-199
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• 2001

Lap splice in plastic hinge region is inevitable because of due to constructional joint between footing and column. R/C Circular columns with lap-splice in plastic hinge region are widely used in Korean highway bridges. In addition, these columns which constructed before the seismic design code have a number of structural deficiencies. It is, however, believed that there are not many experimental research works for nonlinear behavior of these columns subjected to earthquake motions. The object of this research is to evaluate the seismic performance of existing circular reinforced concrete bridge piers by the Quasi-static test. Existing reinforced concrete bridge piers were moderate seismically designed in accordance with the conventional provisions of Korea Highway Design Specification. This study has been performed to verify the effect of lap spliced longitudinal steel, confinement steel type and confinement steel ratio far the seismic behavior of reinforced concrete bridge piers. Quasi-static test has been done to investigate the physical seismic performance of RC bridge piers, such as displacement ductility, energy absorption, strength degradation etc.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.59-62
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• 2005

Seven columns laterally reinforced with either mechanically anchored crossties or conventional crossties under cyclic loading are tested. 4 columns are specimens for flexural strength and 3 columns are for shear strength. Main variable is anchorage types of crossties. Conventional hooks, 180$^{\circ}$ standard hook-mechanical anchorage and all mechanical anchorage type are used. The specimens are tested under 10$\%$ axial load of nominal axial capacity of the columns combined with increasing lateral load. From the flexure test, it is found that columns with mechanical anchorages exhibit superior performance in terms of ductility and energy dissipation. The crossties with mechanical anchorages reduce buckling length of longitudinal rebar. From the shear test, it is found that. 3 specimens exhibit almost the same strength, displacement, and shear failure mode at ductility factor =2.

• Steel and Composite Structures
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• 제12권6호
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• pp.523-540
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• 2012

It was clear from the former researches on reinforced concrete filled tubular steel (RCFT) structures that RCFT structures have different performance than concrete filled steel tubular (CFT) structures. However, despite of that, load-sharing ratio of RCFT is evaluating by the formula and range of CFT given by JSCE. Therefore, the aim of this investigation is to study the load-sharing ratio of RCFT columns subjected to axial compressive load by performing numerical simulations of RCFT columns with the nonlinear finite element analysis (FEA) program - ADINA. To achieve this goal, firstly proper material constitutive models for concrete, steel tube and reinforcement are proposed. Then axial compression tests of concrete, RC, CFT, and RCFT columns are carried out to verify proposed material constitutive models. Finally, by the plenty of numerical analysis with small-sized and big-sized columns, load-sharing ratio of RCFT columns was studied, the evaluation formulas and range were proposed, application of the formula was demonstrated, and following conclusions were drawn: The FEA model introduced in this paper can be applied to nonlinear analysis of RCFT columns with reliable results; the load-sharing ratio evaluation formula and range of CFT should not be applied to RCFT; The lower limit for the range of load-sharing ratio of RCFT can be smaller than that of CFT; the proposed formulas for load-sharing ratio of RCFT have practical mean in design of RCFT columns.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.505-511
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• 2003

Experimental investigation was conducted into the flexure/shear-critical behavior of earthquake-damaged reinforced concrete columns with lap splicing of longitudinal reinforcement in the plastic hinge region. Six test specimens in the aspect ratio of 2,5 were made with test parameters: confinement ratios, lap splices, and retrofitting FRP materials. They were damaged under series of artificial earthquakes of which magnitude could be compatible in Korean peninsula. Directly after the pseudo-dynamic test, damaged columns were retested under inelastic reversal cyclic loading simultaneously under a constant axial load, P=$0.1f_{ck}A_g. Residual seismic performance of damaged columns was evaluated and compared to that of the corresponding original columns. Test results show that RC bridge piers with lap-spliced longitudinal steels in the plastic hinge region appeared to fail at low ductility. This was due to the debonding of the lap splice, which resulted from insufficient development of the longitudinal steels. The specimens externally wrapped with composite FRP straps in the potential plastic hinge region indicated significant improvement both in flexural strength and displacement ductility, and strain energy ductility.

• Earthquakes and Structures
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• 제11권5호
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• pp.823-840
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• 2016

The plastic hinge lengths of beams and columns are a critical demand parameter in the nonlinear analysis of structures using the finite element method. The numerical model of a plastic hinge plays an important role in evaluating the response and damage of a structure to earthquakes or other loads causing the formation of plastic hinges. Previous research demonstrates that the plastic hinge length of reinforced concrete (RC) columns is closely related to section size, reinforcement ratio, reinforcement strength, concrete strength, axial compression ratio, and so on. However, because of the limitations of testing facilities, there is a lack of experimental data on columns with large section sizes and high axial compression ratios. In this work, we conducted a series of quasi-static tests for columns with large section sizes (up to 700 mm) and high axial compression ratios (up to 0.6) to explore the propagation of plastic hinge length during the whole loading process. The experimental results show that besides these parameters mentioned in previous work, the plastic hinge of RC columns is also affected by loading amplitude and size effect. Therefore, an approach toward considering the effect of these two parameters is discussed in this work.

• Steel and Composite Structures
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• 제8권4호
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• pp.329-342
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• 2008

The strengthening of reinforced concrete (RC) columns by steel angles and strips (steel cage) is one of various techniques available to increase ultimate column load. Different authors have shown the influence of the beam-column joint on the behaviour of columns strengthened by steel cages. This paper presents an experimental study carried out at the Universidad Polit$\acute{e}$cnica de Valencia with the aim of analysing two different techniques to solve the strengthening close to the joint and the influence on the behaviour of RC columns strengthened steel cages. The ultimate loads obtained in the laboratory tests for these two techniques are compared to that specified by Eurocode 4.

• Structural Engineering and Mechanics
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• 제5권6호
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• pp.743-754
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• 1997

A three-dimensional constitutive modeling for reinforced concrete is presented for finite element nonlinear analysis of reinforced concrete. The targets of interest to the authors are columns confined by lateral steel hoops, RC thin shells subjected to combined in-plane and out-of-plane actions and massive structures of three-dimensional (3D) extent in shear. The elasto-plastic and continuum fracture law is applied to pre-cracked solid concrete. For post cracking formulation, fixed multi-directional smeared crack model is adopted for RC domains of 3D geometry subjected to monotonic and reversed cyclic actions. The authors propose a new scheme of decomposing stress strain fields into sub-planes on which 2D constitutive laws can be applied. The proposed model for 3D reinforced concrete is experimentally verified in both member and structural levels under cyclic actions.

• Structural Engineering and Mechanics
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• 제32권2호
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• pp.251-267
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• 2009

Reinforced concrete (RC) structures consist of two different materials: concrete and steel bar. The stress transfer behaviour between the two materials through bond plays an important role in the load-carrying capacity of RC structures, especially when they subject to lateral load such as blast and seismic load. Therefore, bond and slip between concrete and reinforcement bar will affect the response of RC structures under such loads. However, in most numerical analyses of blast-induced structural responses, the perfect bond between concrete and steel bar is often assumed. The main reason is that it is very difficult to model bond slip in the commercial finite element software, especially in hydrodynamic codes. In the present study, a one-dimensional slide line contact model in LS-DYNA for modeling sliding of rebar along a string of concrete nodes is creatively used to model the bond slip between concrete and steel bars in RC structures. In order to model the bond slip accurately, a new approach to define the parameters of the one-dimensional slide line model from common pullout test data is proposed. Reliability and accuracy of the proposed approach and the one-dimensional slide line in modelling the bond slip between concrete and steel bar are demonstrated through comparison of numerical results and experimental data. A case study is then carried out to investigate the bond slip effect on numerical analysis of blast-induced responses of a RC column. Parametric studies are also conducted to investigate the effect of bond shear modulus, maximum elastic slip strain, and damage curve exponential coefficient on blast-induced response of RC columns. Finally, recommendations are given for modelling the bond slip in numerical analysis of blast-induced responses of RC columns.