Stirrup Ratio Research Articles

Reinforced ultra-high performance concrete beam under flexure and shear: Experiment and theoretical model

This paper investigated the influence of different shear span ratios, longitudinal (LR) and stirrup (SR) reinforcement ratios, and material types on the flexural and shear performance of reinforced ultra-high performance concrete (UHPC) beams. A series of bending tests with shear span ratios of 4.0, 1.5, and 1.0 were conducted. Results reveal that UHPC beams with a LR ratio of 2.53% exhibit 1.66, 2.00, and 1.45 times higher load capacity than that of the beams with a LR ratio of 1.34% at shear span ratios of 4.0, 1.5, and 1.0, respectively. A SR ratio of 1.40% can achieve 15% and 35% enhancement in load capacity of UHPC beams at shear span ratios of 1.5 and 1.0, respectively. The UHPC beams made with hybrid polyethylene and straight steel fibers have the highest load capacity compared to the beams with straight steel fibers and hooked steel fibers. The enhancement can achieve 8%, 5%, and 15% at shear span ratios of 4.0, 1.5, and 1.0, respectively. Furthermore, cross-section analysis, a novel truss-arch model, and strut-and-tie model were employed to theoretically calculate the load capacity of the UHPC beams with different failure modes. The relative errors of the cross-section analysis and truss-arch model are smaller than 9% and 25%. The findings of this work could provide guidelines for the structural design of UHPC beams under different loading conditions.

Fatigue behavior of deep concrete beams with critical shear cracks

AbstractReinforced concrete deep beams in bridges and other critical infrastructure are subjected to millions of load cycles during their service life. At the same time, they typically work with high shear and develop critical diagonal cracks. The cyclic loading across the cracks results in fatigue damage of the shear‐resisting mechanisms, which needs to be taken into account in the assessment of existing structures, and in particular in members with small amount of shear reinforcement built according to early design codes. To aid the development of advanced assessment approaches for such structures, this paper presents five large‐scale fatigue tests of deep beams with a stirrup ratio of 0.134%. The beams are preloaded to develop complete diagonal cracks, and then are subjected to cycles with different minimum and maximum load. The focus is placed on detailed crack measurements, needed for the development of crack‐based assessment approaches. The crack data is analyzed with the help of the two‐parameter kinematic theory to quantify important deformations. It is shown that the fatigue across the shear cracks is associated mainly with degradation of aggregate interlock and progressive damage in the critical loading zones. It is also shown that as the maximum load is decreased, the fatigue life increases, and the failure mode can switch from shear to flexure.

Bond stress-slip behavior of ultrahigh-strength steel bars with spiral grooves embedded in plain and steel fiber high-strength recycled aggregate concrete

This study investigated the bond behavior of ultrahigh-strength steel bars with spiral grooves (UHSSBs) embedded in high-strength recycled aggregate concrete (RAC). Forty-five pullout specimens under monotonic loadings were designed to evaluate the effect of several parameters on the bond strength. The variables included concrete strength (50 MPa–60 MPa); recycled concrete aggregate (RCA) replacement ratio (0 %, 50 %, and 100 %); embedment length (5db, 10db, and 20db); concrete cover (25 mm, 45 mm, and 68.7 mm); surface treatment; volume fraction of steel fibers in RAC and stirrup ratio. The failure modes of these tests mainly concentrated on two types, pullout-type bond failure and splitting-type bond failure. According to the typical bond stress-slip curves and trendlines of plotted values, the bond strength increased with increasing of concrete compressive strength. For specimens with splitting-type bond failure, the higher normalized bond strength was observed in higher RCA replacement ratio and concrete cover thickness. The factors of embedment length and surface treatment were also proven to be effective for bond strength. For specimens with pullout-type bond failure, the presence of steel fibers and stirrups substantially restricted the splitting crack growth and improved the bond failure modes. Combined with previous experimental results, simple empirical equations for the average bond strength and bond stress-slip relationship between UHSSBs and RAC under different types of bond failure were developed by regression analysis, which can capture the experimental data with high accuracy.

The influence of longitudinal rebar type and stirrup ratio on the bond performance of reinforced concrete with corrosion

This study investigated the bond-slip mechanism of eccentrically pulled out rebar under different corrosion level. The variation patterns of the bonding performance between two types of steel rebars (i.e., plain round rebar and ribbed rebar) and concrete with different stirrup ratios were obtained with respect to the amount of steel rebar corrosion. The differences in bonding performance between plain round rebars and ribbed rebars with concrete were compared, and the bond-slip mechanisms of plain round rebars and ribbed rebars with concrete were elucidated. The influence of longitudinal bar type and stirrup ratio on the ultimate bond strength and bond-slip constitutive curve was analyzed. It has been determined that in the case of uncorroded specimens featuring ribbed bars, the ultimate bond strength exhibits an approximately linear increase in relation to the stirrup ratio. Conversely, the stirrup ratio does not have a significant impact on the ultimate bond strength of uncorroded specimens with plain round bars. Transverse reinforcement plays a crucial role in mitigating the effects of cracked concrete by delaying the reduction in bond stress caused by the corrosion rate of longitudinal reinforcement. This phenomenon becomes increasingly prominent when higher stirrup ratios are utilized in the case of plain round reinforcement. Transverse reinforcement serves to suppress the occurrence of the brittle failure stage that follows the peak bond stress in specimens exhibiting a low corrosion rate. The magnitude of this effect becomes more pronounced as higher transverse reinforcement ratios are employed.

Experimental investigation on the seismic behavior of TRAC frame column with RCA treated by the silica fume cement paste

AbstractThe physical properties of recycled coarse aggregate (RCA) can be strengthened by pre‐soaking them in silica fume cement paste, thereby improving the mechanical properties of recycled concrete. To evaluate whether treated recycled coarse aggregate (TRCA), which is obtained by pre‐soaking in silica fume cement paste, can be applied to structural elements, considering the axial compression ratio and volumetric stirrup ratio, TRCA concrete (TRAC) frame column specimens and natural aggregate concrete (NAC) column specimens were prepared. Subsequently, a cyclic loading test was conducted on the specimens. The failure mode, hysteresis loop, skeleton curve, ductility, and energy dissipation capacity of the specimens were analyzed and compared. The results showed that compared with NAC specimens, the bearing capacities of the TRAC specimens were slightly higher. The seismic behavior of the TRAC frame columns achieved performance level similar to that of the NAC structural members at low axial compression ratios. This indicates that the RCA treatment of pre‐soaking in silica fume cement paste is effective, and TRAC can be used as loading‐bearing structural concrete.

Shear failure mechanism and parametric study for seawater sea-sand engineered cementitious composites beams reinforced by FRP bars: Finite element analysis

Seawater sea-sand engineered cementitious composites (SS-ECC) is recommended to be used in combination with fiber reinforced polymer/plastic (FRP) bars, which is beneficial to mitigate the lack of raw materials in offshore construction. In this study, finite element analysis was carried out to investigate the shear behaviors and failure mechanism of SS-ECC beams reinforced by FRP bars. The proposed finite element models were verified by the shear experimental results of SS-ECC beams with or without stirrups. It is observed that the shear behaviors of SS-ECC beams can be effectively reflected by the finite element models. Moreover, the shear failure mechanism of SS-ECC beams was carefully analyzed. SS-ECC in beams exhibits serious damage in the compression-shear zone, while FRP longitudinal bars and stirrups are not destroyed. Parametric study, including matrix material, shear span ratio and stirrup ratio, was conducted on. For stiffness and peak shear load, SS-ECC beams with stirrups are almost unchanged with the increment of stirrup ratio, which is due to SS-ECC’s failure rather than FRP stirrup rupture. In addition, the prediction method for shear capacity was further validated by the numerical results. The findings of this study lay a foundation for the engineering applications of SS-ECC beams.

Shear capacity of PVC-CFRP confined concrete column-RC beam interior joint strengthened with core steel tube

This paper presents an experimental investigation on polyvinyl chloride (PVC)-carbon fiber reinforced polymer (CFRP) confined concrete (PCCC) column-RC beam interior joint strengthened with core steel tube (CST). Thirteen interior joints are designed and tested under low cyclic loading considering the impacts of six variables, such as diameter-thickness ratio of CST, stirrup ratio of joint, axial compression ratio, CFRP strips spacing, reinforcement ratio of beam and reinforcement ratio of column. Distinct shear deformation in joint region finally dominates the failure of specimens. The load-displacement hysteretic curves are relatively full and eventually show inverse S shape, indicating the specimens have considerable seismic behavior and energy dissipation capacity. The yield and peak shear capacities increase as diameter-thickness ratio, stirrup ratio of joint, reinforcement ratio of column or reinforcement ratio of beam increases. Comparatively, the axial compression ratio and CFRP strips spacing exert less influence on shear capacity. Considering the impact of diameter-thickness ratio, stirrup ratio of joint and reinforcement ratio of column, a formula for estimating shear capacity of PCCC column-RC beam interior joints strengthened with CST is proposed and its accuracy is verified by test data.

Effect of stirrups on shear performance of geometrically-similar reinforced concrete deep beams: An experimental study

In practical engineering, reinforced concrete (RC) beams with stirrups are the predominant form of RC beams. The geometric dimensions of RC beams are large, and the brittle shear failure of them maybe show the characteristics of size effect. However, current research primarily focuses on the size effect of shear failure in RC beams without stirrups, with less emphasis placed on those with stirrups. Furthermore, when the minimum stirrup ratio is exceeded, there is no consensus regarding on whether the size effect still exists. Therefore, the objective of the present work is to discover the influence of the stirrup ratio on the size effect in RC deep beams. In this work, the shear failure experiment of RC deep beams considering the structural size (maximum beam height of 900 mm) and stirrup ratio (0%∼0.942%) is designed and completed. The experiment results indicate that: 1) for the beams without stirrups, clearly, the corresponding size effect on the shear strength is the most obvious, with beam depth increases from 300 mm to 900 mm, the nominal shear strength decreases approximately by 41%; 2) as the stirrup ratio increases from 0 to 0.942%, the size effect is weakened with the presence of stirrups; 3) however, size effect cannot be completely eliminated even when the stirrup ratio reaches as high as 0.942%; (4) generally, for the stirrup ratio of 0.3%, there is a decrease in nominal shear strength by 20%, indicating that consideration of size effects should be taken seriously in practical concrete structure design; (5) moreover, Jin et al.’s size effect law is also compared and validated by the present test data.

Seismic behavior of steel-reinforced high-strength concrete composite beams with bonded tendons

To study the seismic behavior of steel-reinforced high-strength concrete composite beams with bonded tendons (PSRHSCBs) under low cyclic loading, 13 PSRHSCBs were designed with the main parameters of the span-to-height ratio of beams (L/H), the cubic strength of concrete (fcu), the eccentricity of H-shaped steel (eH), the volume stirrup ratio (pv), the longitudinal reinforcement ratio (p), and the tension control stress of tendons(σcon). Using the simplified bilinear constitutive model of steel and the nonlinear constitutive model of high-strength concrete, and introducing plastic damage of concrete, fine finite element models were established with ABAQUS software. 11 similar test specimens were conducted by above modeling method, by comparing existing test curves and numerical simulation curves, both of them match well, which verified the validity of the modeling method. Subsequently, parameter analysis for 13 PSRHSCB specimens was performed, and the influence regularity of different parameters on the seismic behavior of this kind of composite beams was obtained. The results show that hysteretic curves of this kind of composite beams are full, and the failure mode is manifested as bending failure. The ultimate load, the energy dissipation capacity and the ductility coefficient of specimens can be improved significantly by increasing pv, on the contrary, the energy dissipation capacity and the ductility coefficient decrease gradually by increasing fcu. The stiffness degradation of specimens significantly slows down with the increasing of L/H and σcon, and the decreasing of eH. Finally, the trilinear skeleton curve model and the restoring force model are established by statistical regression, and the corresponding seismic design suggestions are given, and these can provide theoretical support for the seismic design of such composite beams in actual engineering.

Numerical simulation and theoretical analysis on RECC ring beam joints for RECC-encased CFST composite columns

The failure mechanisms of reinforced engineered cementitious composite (RECC) ring beam joints were numerically analysed using finite element (FE) software of ATENA. The failure mode, load-carrying capacity, ductility, and distribution of the strain in the steel reinforcement were comprehensively investigated. The simulation results showed that the RECC ring beam significantly contributed to the mechanical property of the joint. Part of the circumferential reinforcement in the ring beam contributed to the shear strength and improved the strength of the core ECC by the restraint effect. A total of 46 specimens were subsequently investigated to examine the influences of the circumferential reinforcement ratio, stirrup ratio, axial compressive ratio, tensile properties and compressive strength of ECC on the seismic behaviour of RECC ring beam joints. Finally, a simplified softened strut-and-tie model was proposed to predict the shear-carrying capacity of the RECC ring beam joint.

Sensitivity Analysis of Factors Influencing the Blast Resistance of Reinforced Concrete Columns Based on Grey Relation Degree

Reinforced concrete (RC) column is an important load-bearing component in building structures. In order to study the blast resistance of RC columns, the numerical simulation model was verified based on the field test data, and the ANSYS/LS-DYNA 2020R2 software was used to expand the working conditions. The sensitivity analysis method of grey relation degree was used to study the effects of factors, such as the diameter of longitudinal reinforcement, number of longitudinal reinforcement, the diameter of the stirrup, stirrup spacing, strength of concrete, scale distance, and strength of reinforcement on the blast resistance of RC columns. The results show that changing the number of longitudinal reinforcements to control the reinforcement ratio can make the peak displacement of RC columns smaller rather than changing the diameter of longitudinal reinforcement. Changing the stirrup spacing to control the stirrup ratio can make the RC column have better blast resistance rather than changing the diameter of the stirrup. The strength of reinforcements and concrete materials has little effect on the mid-span peak displacement of RC columns. The grey relation degree of the influencing factors of the mid-span peak displacement of the RC column is in the order of stirrup spacing, the diameter of the stirrup, scale distance, the diameter of longitudinal reinforcement, the number of longitudinal reinforcement, and the strength of concrete. The relation between stirrup spacing and the diameter of the stirrup is larger, and the grey relation degree is 0.6914 and 0.6660, respectively. This study can provide a reference for the design and construction of RC column structures.

Seismic performance objectives and quantitative deformation limits for superimposed RC shear walls with embedded bracings

To achieve performance-based evaluations for superimposed RC shear walls with embedded bracings (SRCXSW), their seismic performance objectives and quantitative deformation limits are established in this research based on the presentation of the seismic fortification targets and the parametric analysis of deformation limits by OpenSees. Research results exhibit that the seismic fortification targets proposed in this paper can meet the criteria of “Three-level Seismic Fortification Objectives” as stipulated in Chinese regulations, while also accommodating the owner’s desired performance requirements. The deformation indexes of SRCXSW are notably insensitivity to the arrangement of embedded bracings, the volume stirrup ratio and the reinforcement ratio in boundary element, while can be substantially affected by the axial load ratio and aspect ratio. In contrast to the longitudinal reinforcement and stirrup ratio in hidden columns, the volumetric ratio of the embedded bracings exerts a much more pronounced influence on the deformability of SRCXSW. Subsequently, an appraisal of the suggested deformation limits for SRCXSW, in conjunction with those outlined in current assessment codes, is carried out. It is common to observe inadequate safety margins when utilizing the deformation limits for cast-in-place RC shear walls in Eurocode 8 and ASCE/SEI 41. Conversely, the deformation limits proposed in this paper for SRCXSW are robust and offer ample safety margins for practical engineering applications.

Tensile behaviors and configurations of double-headed bar overlap connections for precast concrete members

The superiorities in construction time, cost, and quality of precast RC structures are accompanied by the challenges in connection, particularly in steel bars connections between RC components. The extensively used steel bar connections for either grouted sleeve splice connection or grouted spiral-confined lap connection requires on-site grouting, which is a concealed construction process with increased the risk of grouting defects, thereby impairing connection reliability. The confined headed bar connection (CHBC) with visible on-site construction has been proposed to address the unseen grouting defects concerns. However, modern structures that use large-diameter or high-strength rebars present higher demands for steel bar connection capacity. For CHBC, it is suggested to use either a long connection length or a large-size head to satisfy the capacity demand. However, the long connection length can increase field wet operation, which is disadvantage in precast concrete construction. The large-size head can help reduce the connection length, but it can cause inconvenience including construction congestion and the increased eccentric bending moment under tension. This paper presents the CHBC with double-head configuration, which can reduce the single head size. The proposed CHBC consists of confinement stirrups and two overlapped headed bars and the stirrup confining the core concrete can also improve the CHBC capacity. Experimental investigation on 21 CHBC specimens has been carried out. The failure modes, bearing capacity, and stirrup strain development have been studied. Effects of the double-head configuration and confinement stirrup ratio have been analyzed through experimental and numerical investigation. Results show that the double-head configuration has a minor impact on the tensile capacity of CHBC while the increase of confined stirrup ratio can improve the tensile capacity of CHBC. Configuration details of size and spacing for stirrup reinforcement in CHBC are proposed. Based on the test results, CHBC tensile capacity prediction method is suggested, which can take the head configuration into account.

Experimental Research on Axial Compression Performance of High-Performance-Fiber-Reinforced-Cement-Composite-Prefabricated Monolithic Composite Columns

In order to improve the mechanical properties of prefabricated monolithic composite columns, high-performance fiber-reinforced cement composite (HPFRCC) material was used to prefabricate mold shells and form a composite column with post-cast ordinary concrete. Axial compression tests were conducted on five HPFRCC-prefabricated shell composite columns and one RC prefabricated shell composite column to study the mechanical performances of prefabricated monolithic composite columns. The influences of the volume stirrup ratio, the longitudinal reinforcement ratio, and the shell material on axial compression performance were also studied. The results showed that using HPFRCC-prefabricated shells could improve the deformation performance of the composite column. The compressive strain corresponding to the yielding load of the HPFRCC-prefabricated formwork column was 23.85% higher than that of the RC-prefabricated shell composite column, and the compressive strain corresponding to the peak load increased by 26.72%. The longitudinal reinforcement ratio slightly affected the axial compression bearing capacity of the prefabricated shell composite column. Compared with ECCT−01, the peak load of ECCT−04 increased by 0.6%, and the peak load of ECCT−05 increased by 1.4%. As the volume stirrup ratio increased, the deformation performance of the HPFRCC-prefabricated composite column improved. Compared with ECCT−01, the compressive strain corresponding to the yield load and peak load of ECCT−02 increased by 24.21% and 7.33%, respectively. The compressive strain values corresponding to the yield load and peak load of ECCT−03 decreased by 25.58% and 24.01%, respectively.

Shear design and life cycle assessment of novel limestone calcined clay cement reinforced concrete beams

AbstractTo reduce the impact on global warming, many countries and regions are advocating the use of low‐carbon and green supplementary cementitious materials (SCMs) to improve the cement industry. This study investigates the shear behavior of reinforced concrete (RC) beams made with a novel green concrete, limestone, calcined clay, and cement clinker (LC3). Full‐scale shear tests were conducted on RC and LC3‐RC beams to evaluate their fundamental behavior for structural applications. The shear resistance of LC3 concrete beams was evaluated using Chinese, American, and Eurocode codes, while carbon emission and environmental impact were analyzed by life cycle assessment (LCA). Results showed that LC3‐RC and RC beams exhibited similar shear behavior in terms of crack initiation, propagation, and development. The increase in concrete strength improved the stiffness of LC3‐RC specimens, while RC specimens remained unchanged. The ductility of RC specimens was inversely proportional to concrete strength, while LC3‐RC beams exhibited optimal ductility. The increase in stirrup ratio significantly improved the shear resistance of both LC3‐RC and RC beams. With increased shear‐span ratio, the failure mode of LC3 specimens improved, changing from diagonal‐compression to shear compression or diagonal tension failure. The shear resistance of both LC3‐RC and RC beams was underestimated by GB 50010‐2010, ACI 318‐19, and Eurocode 2. LC3 concrete significantly reduced energy consumption and carbon emissions and achieved favorable environmental benefits in terms of GWP, PMFP, POFP, TAP, and TETP. Increasing usage of limestone in LC3 may further decrease environmental potential without sacrificing mechanical properties. The findings of this study contribute to the development of sustainable and environmentally friendly structures in engineering.

Effect of retrofit type on the blast performance and failure mode of HSC beams retrofitted with UHPFRC

This paper presents a strategy to prevent shear failure and improve the structural performance of existing high-strength concrete (HSC) beams under blast loading. The strategy involves retrofitting with ultra-high performance fiber reinforced concrete (UHPFRC), a novel material which is well-adapted for the blast hardening of concrete structures. Shock-tube air-blast tests are conducted on seven HSC beams which are retrofitted with UHPFRC. The objective was to characterize the effectiveness of various retrofit types on the blast behaviour of both shear-deficient and flexural-dominant HSC members. Three retrofit types were considered: U-jacketing (UJ), full-jacketing (FJ) and a tension-sided (T) overlay. Other parameters included the effects of the concrete substrate roughening method, as well as the tension steel ratio (1.6% or 2.4%) and presence of stirrups in the beams. Both the UJ and FJ retrofits were found to be effective in preventing shear failure in shear-deficient HSC beams having varying shear demands. In addition, both retrofits increased member strength and stiffness, thereby reducing blast-induced displacements and increasing overall blast resistance. Comparing the two retrofits, optimal performance was obtained with full-jacketing due its ability to delay concrete crushing. In HSC beams with sufficient stirrups, both the T-sided and FJ retrofits reduced blast-induced displacements; however, the use of full-jacketing was better able to control damage and increase blast capacity. The roughening method had no substantial effect on the FJ retrofit performance or failure mode, with no debonding observed in the tests.

Simplified Evaluation of Shear Stiffness Degradation of Diagonally Cracked Reinforced Concrete Beams.

Shear cracking in concrete box-girder bridges, which could cause excessive deflection during the serviceability limit state, cannot be effectively avoided by code-guided design. While elastic shear deformation only accounts for a small proportion of total deformation for un-cracked reinforced concrete (RC) beams, the magnitude of after-cracking shear deformation becomes comparable to flexural deformation for RC beams. However, there is still a lack of practical models to predict the after-cracking shear deformation of RC beams. First, six thin-webbed I beams were tested to investigate the shear stiffness degradation mechanism and the decrease ratio. Then, a very simple truss strut angle formula, which is the crucial parameter for shear stiffness, was established. Furthermore, a stiffness degradation rule for partially cracked beams was proposed considering the influence of concrete tension stiffening, which is essential for predicting the development process of after-cracking shear deformation. Finally, directly measured shear strains were used to validate the proposed shear stiffness model. The results showed that the shear stiffness drops to about 30~40% of the original stiffness after the first diagonal crack, and the remaining shear stiffness is only about 10% of the original one when the stirrup yields. Increasing the stirrup ratio is a more effective method to control shear stiffness degradation for diagonally cracked RC beams. Also, the proposed shear stiffness model well captures the main features of the shear stiffness degradation, and it provides a relatively accurate prediction of the equivalent shear stiffness at the post-cracking stage.

Experimental and Numerical Study on the Mechanical Performance of Ultra-High-Performance Concrete T-Section Beams

Aiming to investigate the mechanical performance of UHPC T-section beams, five specimens are fabricated and tested, considering the variable steel fiber volume fraction (SFVF). The code of the Association Francaise de Génie Civil (AFGC) is evaluated by test data. Additionally, based on Abaqus (2020), refined finite element analysis (FEA) models of specimens are established and validated by experimental data. Moreover, the parametric sensitivity analysis is carried out, which aims to further investigate the effect of shear span ratio, longitude reinforcement ratio, and stirrup ratio on the bending-shear behavior of T-section beams. The test results indicated that the ultimate load of the specimen improves with the increase of SFVF, and the use of steel fibers can greatly improve the shear capacity instead of the bending capacity. Furthermore, SFVF can change the failure mode; the specimens fail in shear failure when SFVF < 2%, while they fail in bending failure when SFVF ≥ 2%. From the evaluation of codes, the AFGC code is conservative in the prediction of ultimate capacity, which can guide the design of UHPC structures well. Additionally, from the parametric analysis of FEM, the failure mode transformed from shear failure to bending failure as the shear span ratio increased, particularly in specimens with SFVF ≥ 2.5%. Moreover, the stirrup ratio ρsv has a significant effect on the shear performance of structures with SFVF ≤ 1%, while it has less effect with SFVF ≥ 2%.

Bond-slip behavior between reactive powder concrete and H-shaped steel

The mechanical performance of the steel reinforced reactive powder concrete (SRRPC) structural components significantly depends on the steel-concrete interfacial bond behavior. This paper presents an experimental and analytical investigation on the bond-slip behavior between the reactive power concrete and the H-shaped steel. A total of 11 specimens, considering the cover thickness, embedded length, stirrup ratio and bonding part (whole section, flange and web), were tested through the push-out configurations. Results showed that the cover thickness has the most significant impact on the interfacial properties. Moreover, the SRRPC exhibited the highest residual bond strength compared with the other steel reinforced concretes. The five-stage model and the modified tri-linear model were proposed to describe the average bond stress-slip relationship. It was found that the five-stage model had an excellent accuracy while the modified tri-linear model can reasonably predict the average bond stress-slip relationship. Finally, a comprehensive analytical model was developed to investigate the local longitudinal strain of the shape, bond stress and relative slip.

Seismic performance of steel-reinforced reactive powder concrete columns

The seismic performance of the innovative steel-reinforced reactive powder concrete (SRRPC) composite columns was evaluated via the cyclic experiments considering the steel shape ratio, axial compression ratio and the stirrup ratio. The SRRPC columns generally exhibited appreciable seismic behavior, great crack-resistance and excellent anti-spalling property. It was found that increasing the steel shape ratio from 4.20% to 5.35% can significantly enhance the ductility and the energy dissipation capacity. As the axial compression ratio increased from 0.1 to 0.3, the peak lateral load increased but the ductility significantly decreased. Increasing the stirrup ratio from 1.57% to 2.52% was not helpful for seismic performance in the pre-peak zone but was beneficial to the strength and ductility in the post-peak zone. Moreover, the average strength loss of the SRRPC columns with low axial compression ratio at the 4.5% drift ratio was less than 12.5%, satisfying the modern seismic drift criteria. Two coefficients, βtu and k, for predicting the equivalent tensile strength were identified and compared to the suggested values from the specifications JGJ/T 465-2019 and T/CCPA 35-2022, respectively. An analytical model was successfully developed to predict the lateral load-bearing capacity. Good agreements were found between the experimental and analytical results.