Steel-reinforced High-strength Concrete Research Articles

Seismic Performance of Steel-Reinforced High Strength Concrete Joints Considering Bond Slip Effect

This study presents a solution for push-out failure for the staged bond-slip constitutive relationship between the structural steel and high strength concrete, taking into account the concrete strength grade, anchoring length, and stirrup ratio. The critical point coordinates for different stages are determined by the tests of 14 steel-reinforced high strength concrete (SRHSC) specimens. It is observed that with the increase in the concrete strength grade and anchorage length, the ultimate load of the specimens increased significantly, but the influence on the residual bond strength was not significant. The effect of the stirring ratio was mainly manifested in a slight increase in the initial bond strength. The formula for calculating SRHSC characteristic bond strength and characteristic slip value is established, and the bond-slip constitutive relation of SRHSC is proposed based on the tests. The material constitutive model considering the effect of bond-slip is implanted into the software in the case of the ABAQUS finite element platform. The material is applied to the numerical simulation analysis of the SRHSC exterior joints. The rationality and accuracy of the new material are verified by comparing the simulation results with the test results.

Probabilistic code-based shear capacity model for I-shaped steel reinforced concrete (SRC) beams

A code-based probabilistic prediction model is developed for structural design and reliability analysis of the shear capacity of shear-critical steel reinforced concrete (SRC) beams. First, an experimental database of 83 shear tests was compiled from the literature, including steel-reinforced normal-strength concrete, steel-reinforced high-strength concrete, and steel reinforced lightweight aggregate concrete. Then, three deterministic formulations from the most commonly-used specifications JGJ, AIJ, and ACI-AISC were presented and compared against the database. Based on the different shear mechanism and formula considerations in the code-based deterministic models, this study developed 12 probabilistic models that account for both epistemic and aleatory uncertainty to examine the impact of concrete strength, shear span ratio, number of parameters, and their interactions. The Bayesian theory and Markov Chain Monte Carlo (MCMC) simulation method were utilized to calibrate the models by generating posterior distributions of the model parameters and the standard deviation (SD) of the model error. Optimal model selection hinges upon balancing precision and intricacy. An analysis was then conducted to evaluate the accuracy of the selected model, and the probabilistic model was applied to estimate the shear reliability of a SRC beam. Results demonstrate that the model objectively represents the probabilistic properties of the shear capacity of SRC beams and has the capability to conduct reliability analysis.

Non-linear analysis of eccentric compression of steel and steel fiber reinforced high strength concrete column

To improve the ductility of high-strength concrete and enhance the ductility and load-bearing capacity of steel reinforced high-strength concrete (SRHSC) columns, steel fibers were added to SRHSC to prepare steel and steel fiber reinforced high-strength concrete (SSFRHSC) columns. In order to study the eccentric compression of SSFRHSC columns, based on the experimental study of the eccentric compression of SSFRHSC columns, finite element model specimens of SSFRHSC eccentric columns were established using ABAQUS software, and the accuracy of the model was verified by combining the test results. On the basis of the experiments, the parameters such as steel fiber volume rate, concrete strength and eccentricity distance were further changed to extend the study. The results show that: with the increase of the volume rate of steel fiber from 0.5 % to 3 % and the concrete strength from C40 to C90, the ultimate bearing capacity of the specimen increases by 40.81 % and 58.69 % respectively; at the same time, when the eccentric distance increases from 0 mm to 100 mm, the ultimate bearing capacity of the specimen decreases by 66.76 %, and when the eccentric distance When the eccentricity distance was increased from 0 mm-40 mm to 60 mm-100 mm, the structural damage form changed from brittle damage to ductile damage.

Bond-slip performance of water cooling steel-reinforced high-strength concrete after high temperature

The degradation of bond-slip behavior between steel and concrete after a fire is one of the potential causes of building collapse. In contrast, water cooling is the most commonly used method for extinguishing fires. This paper presents an experimental study on the bond-slip performance of water-cooled steel-reinforced high-strength concrete (SRHC) after exposure to high temperatures. A total of 19 SRHC specimens were tested using push-out experiments to characterize the load-slip curves. The study also discusses the effects of key parameters, including maximum temperature, concrete strength, constant temperature duration, and anchorage length of the steel section, on bond-slip performance. The results indicate that the critical point for degradation of high-strength concrete due to water cooling is 400 °C. As the temperature increases, the bond strength and shear stiffness of the specimens decrease, while the energy dissipation capacity increases. Furthermore, this study develops a constitutive model for water-cooled bond-slip behavior in SRHC and proposes formulas for ultimate bond strength and residual bond strength.

Mechanical Property Analysis and Calculation Method Modification of Steel-Reinforced High-Strength Concrete Columns.

The existing studies lack research on the ductility of steel-reinforced high-strength concrete (SRHC) columns and current specifications restricted the use of high-strength concrete in steel-reinforced concrete (SRC) columns. To compensate for the shortcomings of the existing research and promote the application of high-strength concrete in SRC structures, we test six SRHC columns and one SRC column to examine the effects of the steel content, eccentric distance, and slenderness ratio on the ductility, bearing capacity, and failure mode of SRHC columns. Further, Abaqus finite element models are established to predict the influences of more parameters on post-peak ductility and analyze the relationship between strain development of the concrete and the decrease in bearing capacity of SRHC columns. The results show that the penetration of cracks into aggregate during failure is the primary reason for the poor ductility of the SRHC columns. Improving the confinement effect of the stirrups on concrete is the most effective measure to enhance the ductility of the SRHC columns. The decline in the stirrup spacing from 100 mm to 50 mm increased the ductility coefficient from 1.47 to 5.56. The effect of the steel content, stirrup strength, and slenderness ratio on the ductility coefficient of SRHC columns is less than 30%. After analyzing the reason for the error of current specifications, a modified formula with an error of less than 5% is developed.

Structural behavior of mega steel-reinforced high-strength concrete rectangular columns under axial compression

To meet the requirements of practical engineering, mega steel-reinforced concrete (SRC) columns have been used in super high-rise buildings in recent years. Previous studies on SRC columns primarily focused on simple H-shaped and cruciform steel sections; insufficient attention was paid to mega columns, which are frequently designed with complex steel sections and high-strength concrete. In this study, four 1/6 scaled mega steel-reinforced high-strength concrete (SRHC) rectangular columns with cross-sectional dimensions of 700 mm × 565 mm and various steel ratios and concrete strengths were tested under one-way repeated compression to examine the damage evolution, load-axial deformation response, axial bearing capacity, ductility, stiffness degradation, strain development, restoration, and energy dissipation capacity. The test results indicated that increasing the steel ratio effectively alleviated crack widening and concrete spalling and advanced the bearing capacity, ductility, stiffness, restoration, and energy dissipation capacity. With an increase in concrete strength, the peak load, stiffness, restoration capacity in the elastic-plastic stage, and the energy dissipation capacity in the elastic stage improved, whereas the ductility was sharply impaired, resulting in more abrupt damage. Three provisions were examined to calculate the bearing capacity with conservative estimation. Hence, a theoretical model considering the confinement from the stirrups and steel sections was presented to predict the axial strength with a desirable accuracy. Furthermore, a finite element model was developed to perform the damage evolution and parametric study.

Experimental and analytical research on steel reinforced high-strength concrete columns with different steel sections

Steel reinforced concrete columns are the key vertical load-bearing members in the frame composite structures of super high-rise buildings. The steel sections and steel ratios of these columns are the major factors affecting their seismic performance. In this paper, four large steel reinforced high-strength concrete (SRHC) columns were designed. The influences of closed and open steel sections on the seismic performance of SRHC columns with different steel ratios were analyzed. The test results show that the SRHC columns with closed steel sections had plumper hysteresis loops, a higher and more stable bearing capacity, and greater deformation and energy dissipation capacities than the columns with open steel sections. The influences of the steel ratio on the plumpness of the hysteresis loops, residual deformation and energy dissipation capacity of the columns with open steel sections were greater than those of the columns with closed steel sections. The fiber-based method was adopted to predict the F-Δ curves and N-M interaction curves of the SRHC columns with closed and open steel sections. The calculated results show good agreement with the test results, and the experimental results can provide evidence for the seismic design of SRHC columns with both closed and open steel sections.

Seismic behavior of large-size encased cross-section steel-reinforced high-strength concrete circular columns

Steel-reinforced high-strength concrete (SRHSC) columns can resist large percentages of horizontal shear forces and axial loads, and are widely used in super high-rise buildings. To investigate the effects of the axial load ratio, steel ratio, and loading direction on the seismic performances of encased cross-section SRHSC circular columns, a low-cyclic loading test was conducted on four large-sized specimens, each with a diameter of 700 mm. The failure characteristics, hysteresis curves, bearing capacity, deformation, stiffness degradation, and energy dissipation were analyzed. The finite element software OpenSEES (based on fiber elements) was used to simulate the hysteretic curves of the test specimens, and the simulated results were in good agreement with the test results. The results indicate that all four specimens show bending-dominated damage characteristics. The axial load ratio has a significant influence on the peak load, ductility, and deformation capacity. By increasing the steel ratio, the stiffness degrades more slowly and the specimen shows a better seismic energy dissipation performance. The effect of steel ratio on the improvement of peak load is more evident under a low axial load. With increasing steel strength, there is no significant effect on the initial stiffness and ductility. The specimens with different loading directions have balanced seismic performance, therefore, the columns are suitable for structures in seismic regions. There is little difference between the results calculated by the code of China and Europe and the test results, but the results calculated by the code of China are in better agreement.

Analysis of seismic performance and research of load capacity of steel reinforced high strength concrete columns with rectangular helical hoops

This paper mainly focused on the seismic performance and shear calculation method of steel reinforced high-strength concrete (SRHC) columns with rectangular helical hoops. An experimental investigation was performed in this paper. Eleven SRHC columns with rectangular helical hoops and one with ordinary hoops were constructed at the laboratory of Guangxi university. The failure modes, hysteresis loops, envelope curves, characteristic loads and displacements and cumulative damage analysis are presented and investigated. It can be seen from the test results that the failure modes of SRHC columns can be divided into three types with the shear span ratio increased, namely, shear baroclinic failure mode, flexure-shear failure mode and flexure failure mode. In addition, the specimens with rectangular helical hoops have plumper hysteretic loops. Shear span ratio is the main influencing factor of characteristic load; the axial compression ratio and concrete strength have less influence on characteristic load, while stirrup ratio has little effect on the characteristic load. Finally, a calculation method for shear capacity of SRHC columns under shear baroclinic failure and flexure-shear failure mode is proposed.

Interfacial bond properties and comparison of various interfacial bond stress calculation methods of steel and steel fiber reinforced concrete

Due to the construction difficulties of steel reinforced concrete (SRC), a new composite structure of steel and steel fiber reinforced concrete (SSFRC) is proposed for solving construction problems of SRC. This paper aims to investigate the bond properties and composition of interfacial bond stress between steel and steel fiber reinforced concrete. Considering the design parameters of section type, steel fiber ratio, interface embedded length and concrete cover thickness, a total of 36 specimens were fabricated. The bond properties of specimens were studied, and three different methods of calculating interfacial bond stress were analyzed. The results show: relative slip first occurs at the free end; Bearing capacity of specimens increases with the increase of interface embedded length. While the larger interface embedded length is, the smaller the average bond strength is. The average bond strength increases with the increase of concrete cover thickness and steel fiber ratio. And calculation method 3 proposed in this paper can not only reasonably explain the hardening stage after the loading end curve yielding, but also can be applied to steel reinforced high-strength concrete (SRHC) and steel reinforced recycled coarse aggregate concrete (SRRAC).

Seismic resistance capacity of steel reinforced high-strength concrete columns with rectangular spiral stirrups

In this paper, several experimental investigations on seismic resistance capacity of steel reinforced high-strength concrete (SRHC) columns with rectangular spiral stirrups are presented. Tests were carried out on eleven SRHC columns with rectangular spiral stirrups and one comparative SRHC column with an ordinary stirrup arrangement under low reversed cyclic loading to investigate their failure patterns, characteristic loads and displacements, hysteresis loops, skeleton curves, inter-story drift ratios and ductility coefficients, energy dissipation capacities and stiffness degradation. Range analysis and variance analysis methods were used to analyze the data from the experiments. The results showed that the failure patterns of the test specimens changed from shear baroclinic failure to shear-bond and flexural failure, as the shear span ratio was increased. In addition, the shear span ratio is the main factor that had a significant effect on the carrying capacity of the test specimens. The carrying capacity of the SRHC specimens increased gradually, but their ductility decreased as the axial compression ratio was increased. The ductility coefficients of the SRHC specimens with the normal stirrup and the rectangular spiral stirrup were 3.01 and 3.27, respectively, indicating that the columns with the rectangular spiral stirrup had better deformation capacity. Furthermore, the inter-story drift ratios of all the columns with the rectangular spiral stirrup in elastic phase and elastic-plastic phase were in the range of 1/200 to 1/66 and 1/26 to 1/17, respectively, which are much larger than the limit value specified by the seismic design code. In addition, the SRHC columns with rectangular spiral stirrups exhibited plumper hysteresis curves and higher energy dissipation than the SRHC column with ordinary stirrup. Thus, the SRHC columns with rectangular spiral stirrups showed good seismic resistance capacity.

Experimental investigation of SRHSC columns under biaxial loading

The behavior of 8 steel reinforced high-strength concrete (SRHSC) columns, which comprised of four identical columns with cross-shaped steel and other four identical columns with square steel tube, was investigated experimentally under cyclic uniaxial and biaxial loading independently. The influence of steel configuration and loading path on the global behavior of SRHSC columns in terms of failure process, hysteretic characteristics, stiffness degradation and ductility were investigated and discussed, as well as stress level of the longitudinal and transverse reinforcing bars and steel. The research results indicate that with a same steel ratio deformation capacity of steel reinforced concrete columns with a square steel tube is better than the one with a cross-shaped steel. Loading path affects hysteretic characteristics of the specimens significantly. Under asymmetrical loading path, hysteretic characteristics of the specimens are also asymmetry. Compared with specimens under unidirectional loading, specimens subjected to bidirectional loading have poor carrying capacity, fast stiffness degradation, small yielding displacement, poor ductility and small ultimate failure drift. It also demonstrates that loading paths affect the deformation capacity or deformation performance significantly. Longitudinal reinforcement yielding occurs before the peak load is attained, while steel yielding occurs at the peak load. During later displacement loading, strain of longitudinal and transverse reinforcing bars and steel of specimens under biaxial loading increased faster than those of specimens subjected to unidirectional loading. Therefore, the bidirectional loading path has great influence on the seismic performance such as carrying capacity and deformation performance, which should be paid more attentions in structure design.

Mechanical performance of glass fiber–reinforced polymer tubes filled with steel-reinforced high-strength concrete subjected to eccentric compression

Glass fiber–reinforced polymer tubes filled with steel-reinforced high-strength concrete are proposed as glass fiber–reinforced polymer–steel-reinforced high-strength concrete composite members. Eccentric compression is a typical loading scenario for such column members in practice. Experimental investigation on eight glass fiber–reinforced polymer tubes filled with steel–reinforced high-strength concrete columns subjected to eccentric compression was conducted. The effects of fiber orientation, thickness of glass fiber–reinforced polymer tube, slenderness ratio of columns, and loading eccentricity were investigated. It was found that the compression bearing capacity of glass fiber–reinforced polymer–steel-reinforced high-strength concrete columns increased with the decrease in the fiber tangle angle and the increase in the thickness of the glass fiber–reinforced polymer tube but reduced with the increase in the eccentricity and the slenderness ratio. Corresponding formulas were developed based on the nonlinear full-process analysis theory to describe the compression behavior of glass fiber–reinforced polymer–steel-reinforced high-strength concrete under eccentric loading. Good agreement was found through the comparison between the theoretical and the experimental results. The validated modeling approach was, therefore, employed to develop a parametric analysis that can be used to provide valuable guidance for practical application and further research on such structural members.

Experimental study on steel reinforced high-strength concrete columns under cyclic lateral force and constant axial load

This paper presents the results of an experimental study on the seismic behavior of steel reinforced high-strength concrete (SRHC) columns. A total of 21 SRHC columns were tested under simulated earthquake loading conditions, and the major experimental parameters were the axial load level, stirrup arrangement, structural steel details and studs. The effects of these parameters on the behavior of the SRHC columns were analyzed in detail. The test results showed that SRHC columns with multiple stirrups and commonly used structural steel ratios demonstrated excellent seismic behavior and were suitable for use in high-rise buildings in seismic regions. The axial load had a negative effect on the energy dissipation and deformation capacity. Stirrups exhibited little effect on the initial stiffness and lateral force at cover spalling, but had a positive effect on the energy dissipation and deformation capacity. The benefit of structural steel was more obvious when the effective confinement index was larger or the SRHC columns were subjected to a greater axial load. Structural steel also improved the positive effect of the stirrups. It is suggested that multiple stirrups should be adopted in SRHC columns to provide full play to structural steel; in addition, more structural steel should be adopted when significant axial loads are applied to SRHC columns. Studs did not significantly affect the performance of SRHC columns during the early loading stage. However, columns with studs exhibited better energy dissipation and deformation capacity along with slower stiffness degradation.

Bending Bearing Capacity of Steel Tubular Columns Filled with Steel-Reinforced High-Strength Concrete

Steel tubular column filled with steel-reinforced high-strength concrete (STSRHC) has higher bearing capacity and seismic performance, so STSRHC has a good application prospect in Engineering. So far, it is in the stage of research. To calculate the bending bearing capacity of steel tubular column filled with steel-reinforced high-strength concrete (STSRC), the bending resistance of STSRHC is predicted by the method of plastic stress distribution, and the formula of bending bearing capacity is successfully established. The results show that the calculated results based on the plastic stress distribution method and the experimental ones are in agreement well, and the formula can be used into columns that have different section form of inserted steel. The conclusions have a guiding significance on improving other performances of STSRHC.

Mechanical Behaviors of Slender Steel Tubular Columns Filled with Steel-Reinforced High-Strength Concrete

To study on the mechanical behaviors of the new slender steel-concrete composite columns that are named after steel tubular columns filled with steel-reinforced high-strength concrete(STSRHC), the mechanical models of slender STSRHC are established for the analysis with the finite element software ABAQUS. There are seven influencing factors on the mechanical behaviors of slender STSRHC, they are: slender ratio, eccentricity, the thickness of steel tube, the yield stress of steel tube, the yield stress of inserted steel, the cube strength of high-strength concrete, the shape of inserted steel cross section. The results show the results calculated by software have good agreements with the tested ones; slender ratio, eccentricity and the thickness are the most effective factors on the mechanical properties of slender STSRHC.

Analysis for Pure Bending Performance of Circular Steel Tubular Columns Filled with Steel-Reinforced High-Strength Concrete

This paper is about a new steel tubular columns filled with concrete.

Experimental and numerical study on steel reinforced high-strength concrete short-leg shear walls

Reinforced concrete (RC) short-leg shear wall structure is a new type of mid-rise residential structure system. It has been widely used in China. In order to expand its scope of application to higher high-rises, studies have been focused on novel approaches improving the seismic behavior of this structure system. The present experimental and numerical study was performed to investigate the bearing capacity and seismic behavior of steel reinforced high-strength concrete (SRHC) short-leg shear walls. Results indicate that the tested SRHC short-leg shear walls have shown a bending failure mode, with the crushing of the compressed concrete and the yielding of the tensioned steel. The loading capacity of SRHC short-leg shear walls was greatly improved. The ductility coefficient of the specimens was between 3.62 and 4.35, which was equivalent to that of common RC short-leg shear walls. The specimens with steel-plate skeleton are more ductile in terms of displacement ductility and energy dissipation than the specimens with steel-truss skeleton. The results also indicate that decreasing the compressive ratio improves ductility. The bearing capacity of SRHC short-leg shear wall can be considerably improved by using high strength concrete, while the ductility decreases with the increase of the concrete strength due to the inherent brittleness of high-strength concrete.

Experimental research on fire resistance of circular steel tube column filled with steel-reinforced high-strength concrete

Experimental research on fire resistance of circular steel tube column filled with steel-reinforced high-strength concrete

The Shear Capacity Calculation of Steel Reinforcement High-Strength Concrete Short Columns Restrained with FRP

This article aims to study the calculation for shear capacity of SRHC (Steel Reinforced High-Strength Concrete) members restrained with CFS (Carbon Fiber Sheet). Experimental study, theoretical analysis and calculation simulating are integrated in this article for the research of the shear failure characteristics and effect of various parameters on their behavior of SRHC members restrained with SFC on the basis of existed SRHC members tested results. The shear strength formula of steel reinforcement high-strength concrete short columns restrained with CFS is put forward, which based on the superposed strength method. This method on the basis of the load-deformation process of CFS is similar to hooping. The results indicate that the shear capacity of SRHC columns restrained with CFS is higher than SRHC columns. And, due to the axial compression ratio, shear span ratio and the amount of reinforcement influence the shear capacity of the FRP materials. So, these three kinds of factors are also the influencing factors of shear capacity of SRHC members restrained with CFS. The effect of the internal concrete restrained with CFS is good because of the function of CFS is equal to hooping and the strain of CFS is bigger than the strain of steel, so this simple calculation method is safe , which may be useful for further study and engineering design.