• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.10a
• /
• pp.430-437
• /
• 1998

The existing design expressions for shear strength of reinforced concrete columns are lacking in consistent seismic design philosophy and very conservative. However, relatively not so many experiments have been conducted to verify the shear resisting mechanisms of columns. The previous researches concentrated on deriving an experimental model from their test results. So, there is a need to approach this problem from the analytical point of view to be balanced with the experimental effort. This paper presents a method of modeling reinforced concrete columns under seismic shear loading. Lower bound solutions are obtained by using an analogous truss model and concrete arch actions. This model agrees with the precedented test results by some margins.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.15 no.5
• /
• pp.45-54
• /
• 2011

This paper presents a nonlinear finite element analysis procedure for the performance assessment of deteriorated reinforced concrete bridge columns. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), was used to analyze these reinforced concrete structures. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. Advanced deteriorated material models are developed to predict behaviors of deteriorated reinforced concrete bridge columns. The proposed numerical method for the performance of damaged reinforced concrete bridge columns is verified by comparison with reliable experimental results.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.3 s.49
• /
• pp.21-33
• /
• 2006

The purpose of this study is to assess the seismic performance of reinforced concrete bridge columns using nonlinear finite element analysis. The accuracy and objectivity of the assessment process may be enhanced by the use of sophisticated nonlinear finite element analysis program. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Damage index aims to provide a means of quantifying numerically the damage in reinforced concrete bridge columns sustained under earthquake loading. The proposed numerical method for the seismic performance assessment of reinforced concrete bridge columns is verified by comparison with reliable experimental results.

• Steel and Composite Structures
• /
• v.13 no.5
• /
• pp.473-487
• /
• 2012

An experimental study was performed to investigate the seismic performance of steel reinforced concrete (SRC) special-shaped columns. For this purpose, 17 steel reinforced concrete special-shaped column specimens under low-cyclic reversed load were tested, load process and failure patterns of the specimens with different steel reinforcement were observed. The test results showed that the failure patterns of these columns include shear-diagonal compression failure, shear-bond failure, shear-flexure failure and flexural failure. The failure mechanisms and characteristics of SRC special-shaped columns were also analyzed. For different SRC special-shaped columns, based on the failure characteristics and mechanism observed from the test, formulas for calculating ultimate shear capacity in shear-diagonal compression failure and shear-bond failure under horizontal axis and oblique load were derived. The calculated results were compared with the test results. Both the theoretical analysis and the experimental results showed that, the shear capacity of T, L shaped columns under oblique load are larger than that under horizontal axis load, whereas the shear capacity of +-shaped columns under oblique load are less than that under horizontal axis load.

• Steel and Composite Structures
• /
• v.17 no.3
• /
• pp.271-285
• /
• 2014

This paper aims to examine the behavior of slender reinforced concrete columns confined with external glass fiber reinforced polymers (GFRP) sheets under eccentric loads. The experimental work conducted in this paper is an extension to previous work by the author concerning the behavior of eccentrically loaded short columns strengthened with GFRP wrapping. In this study, nine reinforced concrete columns divided into three groups were casted and tested. Three eccentricity ratios corresponding to e/t = 0, 0.10, and 0.50 in one direction of the column were tested in each group. The first group was the control one without confinement with slenderness ratio equal 20. The second group was the same as the first group but fully wrapped with one layer of GFRP laminates. The third group was also fully wrapped with one layer of GFRP laminates but having slenderness ratio equal 15. The experimental results of another two groups from the previous work were used in this study to investigate the difference between short and slender columns. The first was control one with slenderness ratio equal 10 and the second was fully wrapped and having the same slenderness ratio. All specimens were loaded until failure. The ultimate load, axial deformation, strain in steel bars, and failure mechanisms of each specimen were generated and analyzed. The results show that GFRP laminates confining system is less effective with slender columns compared with short one, but this solution is still applied and it can be efficiently utilized especially for slender columns with low eccentric ratio.

• Computers and Concrete
• /
• v.14 no.2
• /
• pp.193-209
• /
• 2014

Cyclic test of the columns is of practical relevance to the performance of compression members during an earthquake loading. The strength, ductility and energy absorption capabilities of reinforced concrete (RC) columns subjected to cyclic loading have been estimated by many researchers. These characteristics are not normally inherent in plain concrete but can be achieved by effectively confining columns through transverse reinforcement. An extensive experimental program, in which performance of four RC columns detailed according to provisions of ACI-318-08 was studied in contrast with that of four columns confined by a new proposed technique. This paper presents performance of columns reinforced by standard detailing and cast with 25 and 32 MPa concrete. The experimentally achieved load-displacement hysteresis and backbone curves of two columns are presented. The two approaches which work in conjunction with Response 2000 have been suggested to draw analytical back bone curves of RC columns. The experimental and analytical backbone curves are found in good agreement. This investigation gives a detail insight of the response of RC columns subjected to cyclic loads during their service life. The suggested analytical procedures will be available to the engineers involved in design to appraise the capacity of RC columns.

• Structural Engineering and Mechanics
• /
• v.35 no.5
• /
• pp.593-616
• /
• 2010

The seismic performance of reinforced concrete (RC) bridge columns is a significant issue because the interaction of flexural ductility and shear capacity of such columns with varied amounts of lateral reinforcement is not well established. Several relationships between flexural ductility and shear capacity have been proposed by various researchers in the past. In this paper, a parametric study on RC bridge columns is conducted using a nonlinear finite element program, "Simulation of Concrete Structures (SCS)", developed at the University of Houston. SCS has been previously used to predict the seismic behavior of such columns. The predicted results were compared with the test results obtained from experiments available in literature. Based on the results of the parametric study performed in this paper, a set of new relationships between flexural ductility and shear capacity of RC columns is proposed for seismic design.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.28 no.4
• /
• pp.215-222
• /
• 2024

Many older reinforced concrete (RC) buildings were constructed and designed with only gravity loads in mind. Columns in those buildings have insufficient reinforcement details that do not satisfy the requirements specified in current seismic design standards. This study aims to develop drift-based fragility functions for lightly RC columns. For this purpose, a database of 193 lightly RC columns was constructed to determine central and dispersion values of drift ratios for individual damage states. Additionally, to develop more accurate fragility functions of the columns, the failure mode of RC columns was incorporated into fragility functions. The classification procedure for column failure mode is proposed in this study. Fragility functions for older RC columns are constructed according to four different damage states. The main variables of the fragility functions proposed in this study are column properties and failure mode.

• Computers and Concrete
• /
• v.24 no.1
• /
• pp.73-83
• /
• 2019

Concrete reinforced with fiber reinforced polymer (FRP) bars (FRP-RC) has attracted a significant amount of research attention in the last three decades. A limited number of studies, however, have investigated the effect of bond slip on the performance of FRP-RC columns under eccentric loading. Based on previous experimental study, a finite-element model of eccentrically loaded FRP-RC columns was established in this study. The bondslip behavior was modeled by inserting spring elements between FRP bars and concrete. The improved Bertero-Popov-Eligehausen (BPE) bond slip model with the results of existing FRP-RC pullout tests was introduced. The effect of bond slip on the entire compression-bending process of FRP-RC columns was investigated parametrically. The results show that the initial stiffness of bond slip is the most sensitive parameter affecting the compression-bending performance of columns. The peak bond stress and the corresponding peak slip produce a small effect on the maximum loading capacity of columns. The bondslip softening has little effect on the compression-bending performance of columns. The sectional analysis revealed that, as the load eccentricity and the FRP bar diameter increase, the reducing effect of bond slip on the flexural capacity becomes more obvious. With regard to bond slip, the axial-force-bending-moment (P-M) interaction diagrams of columns with different FRP bar diameters show consistent trends. It can be concluded from this study that for columns reinforced with large diameter FRP bars, the flexural capacity of columns at low axial load levels will be seriously overestimated if the bond slip is not considered.

• Advances in concrete construction
• /
• v.4 no.4
• /
• pp.319-332
• /
• 2016

In most cases strengthening reinforced concrete columns exposed to high strain rate is to be expected especially within weak designed structures. A special type of loading is instantaneous loading. Rapid loading can be observed in structural columns exposed to axial loads (e.g., caused by the weight of the upper floors during a vertical earthquake and loads caused by damage and collapse of upper floors and pillars of bridges).Subsequently, this study examines the behavior of reinforced concrete columns under rapid loading so as to understand patterns of failure mechanism, failure capacity and strain rate using finite element code. And examines the behavior of reinforced concrete columns at different support conditions and various loading rate, where the concrete columns were reinforced using various counts of FRP (Fiber Reinforcement Polymer) layers with different lengths. The results were compared against other experimental outcomes and the CEB-FIP formula code for considering the dynamic strength increasing factor for concrete materials. This study reveals that the finite element behavior and failure mode, where the results show that the bearing capacity increased with increasing the loading rate. CFRP layers increased the bearing capacity by 20% and also increased the strain capacity by 50% through confining the concrete.