Steel-reinforced Concrete Joints Research Articles

Structural Behavior of Steel Reinforced Concrete Joint Under Flexural Loads

This research investigates the behavior of RC beam column joints reinforced with steel sections. The study deals with the strengthening of RC joints by different steel sections. The investigation included a theoretical analysis through a performing of simulation of beam-column joints laced with steel sections by using FEA. Implementation of the parametric study included reinforcing the concrete beam with steel sections in many configurations. Shapes and length were the most variables in this study, and many shapes were used, such as I-section, box section, and plates, beside the concrete compressive strength variable. The most recent study revealed the possibility of the method to enhance the efficiency of the joint in resisting the loads while the offering many additional features such as higher ductility, stiffness, and energy absorption. The results showed that strengthening by the steel section enhanced the flexural strength of the joint, but these enhancements were to a certain limit due to the concrete strength limitation. The ultimate strength enhancement was 49%, which is considered a good index for the joint efficiency. The use of compressive strength in small amounts led to the enhancements being limited due to the weakness of the concrete. Strengthening the flexural side of the beam by adding a steel section requires stronger concrete to provide more contribution for the steel section to resist more flexural loads. The increase in the compressive strength of the concrete made the improvements reach their peaks. Strengthening by I-shaped and box steel sections showed that the enhancement due to the existence of the I section was greater than that of the box one. Doi: 10.28991/CEJ-2023-09-03-015 Full Text: PDF

Seismic Performances of SRC Special-Shaped Columns and RC Beam Joints Under Double-Direction Low-Cyclic Reversed Loading

Steel-reinforced concrete (SRC) special-shaped column and beam frame structure is a special structural form that can meet the requirements of high bearing capacity and satisfy the esthetic requirement of buildings. In this study, a new joint design approach is adopted to focus on the seismic behavior of SRC special-shaped column and reinforced concrete (RC) beam joints under low-cyclic double-directional reactions through pseudo-static tests with a controlled stirrup distance. The joints of SRC specimens were compared with those of RC specimens by controlling the area of steel and reinforcement, and hysteresis cycle skeleton curves and load and strain hysteresis cycles were analyzed. The specimen with profiled steel was found to have better energy dissipation capacity. The energy dissipation capacity and stiffness degradation of the nodes were analyzed. The test results showed that the energy dissipation capacity of the SRC joints was better than that of the conventional concrete column joints, and the stiffness degradation of RC joints was more significant than that of SRC joints.

Experimental and numerical study performed on seismic behavior of irregular external SRC joints in the main plant of CAP1400 NPP

The main plant of steel reinforced concrete (SRC) structure is proposed for CAP1400 nuclear power plant (NPP) in high seismic zone, which not only has better mechanical properties than reinforced concrete structure plant, but also has lower maintenance cost than steel structure plant. The irregular SRC joints are inevitably appeared in the main plant due to the limitations of power generation technology and equipment. In this paper, quasi-static cyclic tests were carried out on three 1:4 reduced scale irregular external SRC joints to discuss the seismic performance of the joints in the NPP, mainly including the damage pattern, hysteretic behavior, load carrying capacity, stiffness degradation and ductility. In addition, the detailed 3D finite element (FE) models were established, in which the bond-slip behavior between the shaped steel and concrete was considered by using the developed software to add a huge number of non-linear spring elements, and the FE models were verified by the test results. Then, the parametric study on seismic performance of irregular external SRC joint was carried out, and the influence of each parameter on the seismic performance of the irregular external SRC joint was analyzed. Finally, the effective and economical reinforcement measures were proposed, and verified by the FE method.

Equivalent Frame Model with a Decaying Nonlinear Moment-Curvature of Steel-Reinforced Concrete Joints

A numerical model for the analysis of frame structures that is capable of reproducing the behavior of reinforced concrete (RC) members and steel-reinforced concrete (SRC) members in all steps until collapse by simulating a reduced resistance capacity is presented in this work. Taking into account the solid models obtained in previous research that have been validated by experimental results, moment-curvature graphics were obtained in all steps: elastic, plastic, and post-critical to collapse. Beam models versus 3D models considerably simplified the calculation of frame structures and correctly described both the plastic and post-critical phases. The moment-curvature graph can be used in a simplified frame analysis, from post critical behavior to collapse.

Experimental evaluation of the behaviour of bamboo-reinforced beam–column joints

The housing industry has a high energy consumption because of the widespread use of items such as concrete and steel for construction. Consequently, researchers have explored the use of bamboo, which is an eco-friendly material, as an alternative to steel in the construction of buildings. Bamboo is already used for constructing various structural members, such as beams, columns, slabs, and walls. However, no study has been performed on the behaviour of beam–column joints made of bamboo reinforcement. The present study focused on using bamboo as an alternative reinforcing material in beam–column joints. A series of laboratory tests were conducted for investigating the mechanical properties of bamboo. The failure of six full-scale bamboo-reinforced beam–column joints in a reaction frame was examined. Furthermore, the effectiveness of different configurations of beam–column joints was investigated in terms of the load–deformation characteristics, ultimate moment, cracking behaviour, and failure patterns through experimental testing. A comparative study of bamboo-reinforced beam–column joints with and without water-repellent treatment and steel-reinforced beam–column joints is conducted. The ultimate load-carrying capacity of the bamboo-reinforced beam–column joints was considerably larger than that of joints without any water-repellent treatment. The performance of steel-reinforced concrete joints was marginally better than that of bamboo-reinforced concrete joints.

Experimental study on shear capacity of SRC joints with different arrangement and sizes of cross-shaped steel in column

The seismic performance of the ordinary steel reinforced concrete (SRC) columns has no significant improvement compared to the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type shaped steel were put forward on this background, and they were named as enlarging cross-shaped steel and diagonal cross-shaped steel for short. The seismic behavior and carrying capacity of new-type SRC columns have been researched theoretically and experimentally, while the shear behavior remains unclear when the new-type columns are joined onto SRC beams. This paper presents an experimental study to investigate the shear capacity of new-type SRC joints. For this purpose, four new-type and one ordinary SRC joints under low reversed cyclic loading were tested, and the failure patterns, load-displacement hysteretic curves, joint shear deformation and steel strain were also observed. The ultimate shear force of joint specimens was calculated according to the beam-end counterforce, and effects of steel shape, load angel and structural measures on shear capacity of joints were analyzed. The test results indicate that: (1) the new-type SRC joints display shear failure pattern and has higher shear capacity than the ordinary one; (2) the oblique specimens have good bearing capacity if designed reasonably; and (3) the two proposed construction measures have little effect on the shear capacity of SRC joints embedded with diagonal cross-shaped steel. Based on the mechanism observed from the test, the formulas for calculating ultimate shear capacity considering the main factors (steel web, stirrup and axial compression ratio) were derived, and the calculated results agreed well with the experimental and simulated data.

Performance of Steel-Reinforced Concrete Beam-to-Column Joints after Exposure to Fire

AbstractThis paper presents a numerical analysis on the postfire behavior of steel-reinforced concrete (SRC) column to axially and rotationally restrained SRC beam joints. A finite-element analysis (FEA) model was developed to simulate the reaction of the composite joints under an entire loading and fire phase, including ambient temperature loading, heating, and cooling with constant loads and postfire loading. For validation, the proposed modeling method was used to simulate the results of SRC joint postfire tests and SRC column and joint fire-resistance tests. The comparison demonstrates the accuracy of the proposed FEA model. Based on the validated FEA model, the failure modes of SRC joints with restrained beams were investigated, and the joint deformation and internal force development during the entire loading and fire phase were analyzed. Afterward, two important parameters, namely, residual joint strength index and residual stiffness index, were defined based on the joint moment versus relative rot...

Seismic behavior of steel reinforced concrete (SRC) joints with new-type section steel under cyclic loading

No significant improvement has been observed on the seismic performance of the ordinary steel reinforced concrete (SRC) columns compared with the reinforced concrete (RC) columns mainly because I, H or core cross-shaped steel cannot provide sufficient confinement for core concrete. Two improved SRC columns by constructing with new-type section steel were put forward on this background: a cross-shaped steel whose flanges are in contact with concrete cover by extending the geometry of webs, and a rotated cross-shaped steel whose webs coincide with diagonal line of the column's section. The advantages of new-type SRC columns have been proved theoretically and experimentally, while construction measures and seismic behavior remain unclear when the new-type columns are joined onto SRC beams. Seismic behavior of SRC joints with new-type section steel were experimentally investigated by testing 5 specimens subjected to low reversed cyclic loading, mainly including the failure patterns, hysteretic loops, skeleton curves, energy dissipation capacity, strength and stiffness degradation and ductility. Effects of steel shape, load angel and construction measures on seismic behavior of joints were also analyzed. The test results indicate that the new-type joints display shear failure pattern under seismic loading, and steel and concrete of core region could bear larger load and tend to be stable although the specimens are close to failure. The hysteretic curves of new-type joints are plumper whose equivalent viscous damping coefficients and ductility factors are over 0.38 and 3.2 respectively, and this illustrates the energy dissipation capacity and deformation ability of new-type SRC joints are better than that of ordinary ones with shear failure. Bearing capacity and ductility of new-type joints are superior when the diagonal cross-shaped steel is contained and beams are orthogonal to columns, and the two construction measures proposed have little effect on the seismic behavior of joints.

Steel-reinforced concrete joints under reversal cyclic load

The performance of structural joints comprising built-up steel-reinforced concrete (SRC) columns connecting to reinforced concrete (RC) beams under reversal cyclic loads is described in this paper. Eight composite joint specimens were tested to failure. Three modes of failure, namely, bending failure in beam, bending–shear failure in beam and shear failure in beam and joint were observed. Test results indicated that energy dissipation capacity of the SRC joint depends on the modes of failure and the levels of axial load imposed on the column. The higher the level of axial force imposed on the column, the lower the energy dissipation capability but the larger shear capacity of the joint. An analytical model for the evaluation of the shear capacity of SRC joint taking into account the effects of the presence of steel section, stirrups, axial force in column and ductility demand is proposed. Analytical and experimental results show good agreement.

Steel-reinforced concrete joints under reversal cyclic load

The performance of structural joints comprising built-up steel-reinforced concrete (SRC) columns connecting to reinforced concrete (RC) beams under reversal cyclic loads is described in this paper. Eight composite joint specimens were tested to failure. Three modes of failure, namely, bending failure in beam, bending–shear failure in beam and shear failure in beam and joint were observed. Test results indicated that energy dissipation capacity of the SRC joint depends on the modes of failure and the levels of axial load imposed on the column. The higher the level of axial force imposed on the column, the lower the energy dissipation capability but the larger shear capacity of the joint. An analytical model for the evaluation of the shear capacity of SRC joint taking into account the effects of the presence of steel section, stirrups, axial force in column and ductility demand is proposed. Analytical and experimental results show good agreement.