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This paper investigates experimentally and numerically structural performance of reinforced concrete (RC) circular column under double curvature buckling moment. RC circular columns are popularity embraced in RC structures not only owing to its esthetic, attractive appearance and easy for construction, but also for its better contribution for stress resistance. However, the corner or edge columns may be exposed to edge moment (EM) transferred from beam–column joint with double curvature effect. The current investigation proposes to understand the structural exhibition of such columns subjected to double curvature buckling edge moment generated at beam–column joint considering some parameters. A total number of 11 full-scale RC circular columns were constructed, installed, and then tested up to failure studying four parameters. These parameters were: clear height-to-diameter ratio (λ), longitudinal and lateral steel ratios (μ and ρ, respectively) and concrete type. The λ ratio has been introduced with: 4.89, 4.51 and 4.14. The μ ratio has been presented by: 2.2%, 2.3%, 2.6%, and 3.1%, while the ρ ratio was employed with: 0.84%, 0.93%, 1.00% and 1.18%. Three concrete types were studied; one of them was normal concrete (NC), while the other ones were high-performance concretes (HPCs) which were engineered cementitious composite (ECC) and high-strength fiber reinforced concrete (HSFRC). Experimental outcomes revealed that all studied parameters could affect and upgrade the structural performance; however, both longitudinal reinforcement and height-to-diameter ratio provided significant enhancement (about 51%–64%). Parallel to those exploited experimentally, nonlinear three-dimensional finite element models (FEMs) were installed, executed and established considering experimental outcomes producing an acceptable model with an under/over-estimation of about 4%. [ABSTRACT FROM AUTHOR]

To investigate the flexural behavior of hybrid reinforced concrete (Hybrid‐RC) beams with Basalt fiber‐reinforced polymer (BFRP) bars and steel bars, this paper designed 14 Hybrid‐RC beams and studied the effect of different reinforcement forms on the flexural behavior of Hybrid‐RC beams. The research results indicated that when ρ≈2.28%$$ \rho \approx 2.28\% $$, an increase in Af/As$$ {A}_{\mathrm{f}}/{A}_{\mathrm{s}} $$ leads to a decrease in the cracking moment, ultimate moment, and ductility of Hybrid‐RC beams, the maximum crack width and deflection will increase. When ρ≈0.86%$$ \rho \approx 0.86\% $$, an increase in Af/As$$ {A}_{\mathrm{f}}/{A}_{\mathrm{s}} $$ will lead to a decrease in the cracking moment, deflection, and ductility of the Hybrid‐RC beams, while the maximum crack width and ultimate moment will increase. In addition, when ρ≤1.87%$$ \rho \le 1.87\% $$, the area of BFRP bars (the area of steel bars remains unchanged) should be changed to improve the flexural behavior of the Hybrid‐RC beams; When ρ>1.87%$$ \rho >1.87\% $$, the Hybrid‐RC beams should change the area of steel bars (the area of BFRP bars remains unchanged) to improve the flexural behavior of the beams. In addition, the ductility index prediction equation for Hybrid (BFRP and steel)‐RC beams was fitted based on the results of the theoretical model research. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates experimentally and numerically structural performance of reinforced concrete (RC) circular column under double curvature buckling moment. RC circular columns are popularity embraced in RC structures not only owing to its esthetic, attractive appearance and easy for construction, but also for its better contribution for stress resistance. However, the corner or edge columns may be exposed to edge moment (EM) transferred from beam–column joint with double curvature effect. The current investigation proposes to understand the structural exhibition of such columns subjected to double curvature buckling edge moment generated at beam–column joint considering some parameters. A total number of 11 full-scale RC circular columns were constructed, installed, and then tested up to failure studying four parameters. These parameters were: clear height-to-diameter ratio (λ), longitudinal and lateral steel ratios (μ and ρ, respectively) and concrete type. The λ ratio has been introduced with: 4.89, 4.51 and 4.14. The μ ratio has been presented by: 2.2%, 2.3%, 2.6%, and 3.1%, while the ρ ratio was employed with: 0.84%, 0.93%, 1.00% and 1.18%. Three concrete types were studied; one of them was normal concrete (NC), while the other ones were high-performance concretes (HPCs) which were engineered cementitious composite (ECC) and high-strength fiber reinforced concrete (HSFRC). Experimental outcomes revealed that all studied parameters could affect and upgrade the structural performance; however, both longitudinal reinforcement and height-to-diameter ratio provided significant enhancement (about 51%–64%). Parallel to those exploited experimentally, nonlinear three-dimensional finite element models (FEMs) were installed, executed and established considering experimental outcomes producing an acceptable model with an under/over-estimation of about 4%.

The behavior of precast concrete tunnel lining (PCTL) segments reinforced with glass fiber-reinforced polymer (GFRP) bars under punching loads is one area in which no research work has been conducted. This paper reports on an investigation of the punching-shear behavior of GFRP-reinforced PCTL segments induced by soil conditions, such as rock expansion or the geotechnical conditions surrounding a tunnel. Six full-scale rhomboidal PCTL specimens measuring 1500 mm (59 in.) in width and 250 mm (9.8 in.) in thickness were constructed and tested up to failure. The investigated parameters were: 1) reinforcement type (GFRP or steel); 2) reinforcement ratio (0.46 or 0.86%); 3) stirrups as shear reinforcement; and 4) segment length (2100 or 3100 mm [82.7 or 122 in.]). The experimental results are reported in terms of cracking behavior, punching-shear capacity, deflection, strain in the reinforcement and concrete, and failure modes. The results reveal that the GFRP-reinforced PCTL segment was comparable with its steel counterpart with the same reinforcement ratio and satisfied serviceability limits. Increasing the reinforcement ratio and decreasing the segment length enhanced the punching-shear strength. The shear stirrups improved the structural performance and increased the punching and deformation capacities of the GFRP-reinforced PCTL segments. In addition, theoretical predictions of the punching-shear capacity using the current design provisions were compared to the experimental results obtained herein. The theoretical outcomes show the suitability of using current FRP design provisions for predicting the punching capacity of PCTL segments reinforced with GFRP bars. [ABSTRACT FROM AUTHOR]

Restraining the expansion of expansive concrete with embedded rebars can exert chemical prestressing, which may affect the durability of concrete structures. This study aims to investigate the durability performance of expansive concrete by understanding the mechanism of air permeability changes while considering the variations in reinforcement arrangements and concrete dimensions. The Torrent's air permeability test was used to non-destructively evaluate the disparity in air permeability changes of expansive and normal concrete during the drying processes from 28 to 182 days. Additionally, expansive strain changes were continuously monitored to investigate chemical prestress. The experimental test results suggest the immense effect of the change in expansive strain on the air permeability of concrete. This study proposes that the change in microstructure owing to the loss of expansive strain may cause an increase in air permeability. The loss of expansive strain is a distinguished feature that differentiates the mechanism of air permeability changes in expansive and normal concrete. These findings suggest the possible improvement in the durability performance of expansive concrete in cases where the loss of its expansive strain can be controlled. [ABSTRACT FROM AUTHOR]

The crack resistance of concrete structures with low reinforcement ratios requires a broader examination. It is particularly important in the case of foundations working in changing subsoil conditions. Unfavorable phenomena occurring in the subsoil (e.g., ground subsidence, landslips, non-uniform settlement) can lead to unexpected cracking. Therefore, it is necessary to check the effectiveness of the low reinforcement provided. As there are limited studies on lightly reinforced concrete structures, we performed our own experimental investigation and numerical calculations. In the beams analyzed, the reinforcement ratio varied from 0.05% to 0.20%. It was found that crack resistance in concrete members depends on the reinforcement ratio and steel bar distribution. A comprehensive method was proposed for estimating the crack resistance of lightly reinforced concrete members in which both the reinforcement ratio and the reinforcement dispersion ratio were taken into account. Furthermore, the method considered the size effect and the fracture properties of concrete. The proposed method provides the basis for extrapolation of the test results obtained for small elements and conclusions for members with large cross-sections, such as foundations, which frequently use lightly reinforced concrete. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Strengthening the carpentry joints is considered a big challenge for designers to maintain the joined timber elements’ load transfer and integrity. This research work investigates different techniques to strengthen the lap joints in glulam timber beams using carbon fiber-reinforced polymer (CFRP) sheets. For this purpose, 12 specimens of glulam timber beams were tested using the four-point loading method. One of the glulam timber specimens was an intact nonlapped specimen, and the others were lapped at mid-span using half-height lap joints. The lap joints were strengthened using different configurations of the CFRP sheets. The test variables were the clamping scheme, bond length, and reinforcement ratio of the CFRP sheets. The analysis of the test results indicates that the CFRP strengthening configuration could be more effective in strengthening the lapped glulam timber beams when the reinforcement ratio of the longitudinal CFRP sheets was equal to 0.303%, and the wrapping CFRP sheets continued beyond the lapped joint by a distance equal to the beam height. Such a strengthening configuration could succeed in increasing the effective stiffness and ultimate load of the lapped timber specimen to 109 and 110%, respectively, relative to those of the intact nonlapped specimen. Moreover, the results reveal that increasing the length or the reinforcement ratio of the longitudinal CFRP sheets without increasing the width of the wrapping CFRP sheets could not succeed in achieving the required improvements in the structural behavior of the lapped timber beams.

Over the past decade, the textile-reinforced concrete (TRC) composite was gradually used to replace the fibre-reinforced polymer in the strengthening or repairing of existing reinforced-concrete structures, thanks to many criteria of sustainable development. The reinforcement ratio of textiles within TRC composites emerges as a crucial factor significantly impacting their reinforcement effectiveness, altering the material’s mechanical behaviour and properties. This study presents both experimental and numerical findings concerning the tensile behaviour of carbon TRC composites, exploring reinforcement ratios ranging from 0.5 to 1.5%. As experimental results, the carbon TRC specimens exhibited a strain-hardening behaviour with the cracking phase. The ultimate strength improved by 95 and 146% compared to that of non-reinforced specimens, respectively, with the reinforcement ratio of 0.92 and 1.32%. As numerical results, the model reached the strain-hardening curve with three distinct phases when the reinforcement ratio was higher than a critical value (0.7%). The effect of reinforcement ratio ranging from 0.5 to 1.5% on the mechanical behaviour and properties of carbon TRC was also highlighted and analysed.

This article presents a review of state of the art on nonmetallic reinforcement in terms of bending moment redistribution in double‐span elements. The authors present a summary of existing research programs focused on moment redistribution in FRP (Fiber Reinforced Polymer) reinforced concrete (RC). On this basis authors created a database of concrete elements with all the important construction properties of the elements. Gathered data are presented with quantitative analysis of several variables effecting moment redistribution in published articles. In the following publication authors show a research review which includes an analysis of the influence of variable parameters from the point of view of the database, concerning: degrees of longitudinal reinforcement, ratio between degrees of reinforcement in span and over the support, type of reinforcement (FRP/steel/hybrid), concrete class and transverse reinforcement. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ultra-high-performance geopolymer concrete (UHPGC) emerges as a sustainable and cost-effective alternative to Portland cement-based UHPC, offering similar mechanical properties while significantly reducing carbon footprint and energy consumption. Research on UHPGC components is extremely scarce. This study focuses on the flexural and crack behavior of UHPGC beams with different steel fiber contents and longitudinal reinforcement ratios. Five UHPGC beams were tested under four-point bending. The test results were evaluated in terms of the failure mode, load–deflection relationship, flexural capacity, ductility, average crack spacing, and short-term flexural stiffness. The results show that all the UHPGC beams failed due to crack localization. Increases in the reinforcement ratio and steel fiber content had favorable effects on the flexural capacity and flexural stiffness. When the reinforcement ratio increased from 1.18% to 2.32%, the flexural capacity and flexural stiffness increased by 60.5% and 12.3%, respectively. As the steel fiber content increased from 1.5% to 2.5%, the flexural capacity and flexural stiffness increased by 4.7% and 4.4%, respectively. Furthermore, the flexural capacity, flexural stiffness, and crack spacing of the UHPGC beams were evaluated using existing methods. The results indicate that the existing methods can effectively predict flexural capacity and flexural stiffness in UHPGC beams but overestimate crack spacing. This study will provide a reference for the structural design of UHPGC. [ABSTRACT FROM AUTHOR]

The article investigates the cyclic behavior of reinforced concrete flexural members by analyzing the impact of changing design parameters, highlighting conflicting findings from past research. Topics include the effects of transverse reinforcement spacing, longitudinal reinforcement diameter, and tension-to-compression reinforcement ratio on the seismic performance and shear slippage of specimens.

This paper carries out experimental and numerical investigations on the axial performance of circular Reinforced Concrete (RC) precast slender columns with an intermediate connection. A series of tests are carried out to study the effects of longitudinal reinforcement ratio (ρ), and embedded length of steel bars (Lb) of precast columns on their axial performance under concentric loading. Test results show that increasing the reinforcement ratio and the embedded length of the precast columns significantly improves the axial performance of the precast slender columns. Nonlinear finite element models (FEM) are developed to simulate the performance of the columns experimentally observed. The accuracy of the FEM is validated against the test results and found to reasonably predict the axial performance of tested columns. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) is a cement-based material with excellent impact resistance. Compared with traditional concrete, it possesses ultra-high strength, ultra-high toughness, and ultra-high durability, making it an ideal material for designing structures with impact resistance. The research on the impact resistance performance of UHPC and its composite structures is of great significance for the structural design of protective engineering projects. However, currently, there is still insufficient research on the impact resistance performance of UHPC composite structures. To study the impact resistance performance, experiments were conducted on UHPC targets using high-speed projectiles. The results were compared with impact tests on granite targets. The results indicated that when subjected to projectile impact, the UHPC targets exhibited smaller surface craters compared with the granite targets, while the penetration depth was lower in the granite targets. Afterwards, the process of a projectile impacting the UHPC composite structure was numerically simulated using ANSYS 16.0/LS-DYNA finite element software. The numerical simulation results of penetration depth and crater diameter were in good agreement with the experimental results, which indicates the rationality of the numerical model. Based on this, further analysis was carried out on the influence of impact velocity, impact angle, and reinforcement ratio on the penetration depth of the composite structure. The results show that the larger the incident angle or the smaller the velocity of the projectile is, the easier it is to deflect the projectile. There is a linear relationship between penetration depth and reinforcement ratio; as the reinforcement ratio increases, the penetration depth decreases significantly. This research is of great significance in improving the safety and reliability of key projects and also contributes to the application and development of ultra-high-performance materials in the engineering field. [ABSTRACT FROM AUTHOR]

The paper proposes a new equation for the prediction of punching shear strength of reinforced concrete flat slabs. The basis of the new predictive equation is a detailed numerical parametric study conducted using the nonlinear 3D finite element analysis using FE software MASA. For this, results of the previously tested flat slabs from literature are used as reference for validation of the numerical model. The numerical modelling procedure is validated with two previously tested slabs, one failing in pure punching prior to yielding of flexural rebar, and the second failing in flexure-punching which resulted in yielding followed by punching. The result shows that the load-displacement behavior, failure modes and the crack pattern are captured well by the analysis. Following the validation, a detailed parametric study is performed to investigate the influence of slab depth, concrete strength, longitudinal reinforcement ratio, column size and effect of reinforcement spacing. From the evaluation of results, it is observed that the punching resistance increases with slab depth but at a decreasing rate (size effect). The punching shear strength also increases with increasing longitudinal reinforcement ratio, concrete strength as well as the column area. All the reinforcing bars placed within a distance of 3.5 times the effective depth of the slab from the column center contributes significantly towards dowel action. With increasing column size, the deformation at the peak load also increases. Based on the evaluation of the results of the analyses, an empirical equation for the prediction of punching shear is derived. The results of the equation are compared with the results of a large experimental database of 235 tests, and it is shown that the proposed equation leads to better agreement with the test results compared to the equations given in the current codes (ACI, Canadian, Eurocode, Japanese code). The comparison shows that generally the predictions by existing equations in the codes tend to be unconservative for large slab with low reinforcement ratio.

The influence of fire on self-curing reinforced concrete flat slabs was inspected in this study. In this paper the focus will be on the effectiveness of the reinforcement ratio, heat duration and cooling method on the behavior of self-curing (SCU) reinforced concrete flat slabs exposed to fire. To create SCU concrete, polyethylene glycol (PEG 400) is added at a rate of 0.5% of cement weight. Twenty-five RC plates (1200 mm x 1200 mm x 70 mm) lying on four supports and being subjected to concentrated load were used to achieve the experimental programme. The experimental program was conducted in two stages. The first stage, the specimen exposed to high temperature (600oc) for 1 hour and 2 hours. To record the failure load and the deflections at each load increment, the load was gradually increased in the second stage. The results show that, the cracking and the ultimate loads decreased, while the deflection increase either with the increase of fire flame duration and cooling method from gradually to sudden.

Confined masonry (CM) construction is being increasingly adopted for its cost-effectiveness and simplicity, particularly in seismic zones. Despite its known benefits, limited research exists on how the stiffness of confining elements influences the in-plane behavior of CM. This study conducted a comprehensive parametric analysis using experimentally validated numerical models of single-wythe, squat CM wall panels under quasi-static reverse cyclic loading. Various cross-sections and reinforcement ratios were examined to assess the impact of the confining element stiffness on the deformation response, the cracking mechanism, and the hysteretic behavior. The key findings included the observation of symmetrical hysteresis in experimental CM panels under cyclic loading, with a peak lateral strength of 114.3 kN and 108.5 kN in push-and-pull load cycles against 1.7% and 1.3% drift indexes, respectively. A finite element (FE) model was developed based on a simplified micro-modeling approach, demonstrating a maximum discrepancy of 2.6% in the peak lateral load strength and 5.4% in the initial stiffness compared to the experimental results. The parametric study revealed significant improvements in the initial stiffness and seismic strength with increased depth and reinforcement in the confining elements. For instance, a 35% increase in the lateral strength was observed when the depth of the confining columns was augmented from 150 mm to 300 mm. Similarly, increasing the steel reinforcement percentage from 0.17% to 0.78% resulted in a 16.5% enhancement in the seismic strength. These findings highlight the critical role of the stiffness of confining elements in enhancing the seismic performance of CM walls. This study provides valuable design insights for optimizing CM construction in seismic-prone areas, particularly regarding the effects of confining element dimensions and reinforcement ratios on the structural resilience.

The crack resistance of concrete structures with low reinforcement ratios requires a broader examination. It is particularly important in the case of foundations working in changing subsoil conditions. Unfavorable phenomena occurring in the subsoil (e.g., ground subsidence, landslips, non-uniform settlement) can lead to unexpected cracking. Therefore, it is necessary to check the effectiveness of the low reinforcement provided. As there are limited studies on lightly reinforced concrete structures, we performed our own experimental investigation and numerical calculations. In the beams analyzed, the reinforcement ratio varied from 0.05% to 0.20%. It was found that crack resistance in concrete members depends on the reinforcement ratio and steel bar distribution. A comprehensive method was proposed for estimating the crack resistance of lightly reinforced concrete members in which both the reinforcement ratio and the reinforcement dispersion ratio were taken into account. Furthermore, the method considered the size effect and the fracture properties of concrete. The proposed method provides the basis for extrapolation of the test results obtained for small elements and conclusions for members with large cross-sections, such as foundations, which frequently use lightly reinforced concrete.

This paper presents an experimental study about the effect of the ratio between the area of Basalt Fiber Reinforced Polymer (BFRP) bars to the total area of steel and BFRP bars (Af/At) on the behavior of Reinforced Concrete Box (RCB) girders. Also, it displays the effectiveness of the mixed steel and BFRP (MSBFRP) bars as the main reinforcement to enhance the behavior of RCB girders in flexure. Moreover, the ultimate flexural capacity of the tested girders was evaluated analytically. The experimental program consisted of five RCB girders. The first two girders were reinforced in the tension side with either steel or BFRP bars, while the other three ones were reinforced with both steel and BFRP bars with different Af/At ratios. The effect of Af/At ratio on the initiation and propagation of cracks, mode of failure, ultimate and cracking loads, the corresponding deflection, and ductility was investigated. It was found that increasing the Af/At ratio improved both the ultimate load and the deflection at failure, while the ductility index decreased. Comparing the obtained RCB test results with those found in the literature of the ordinary beams revealed that the behavior is almost identical. The Af/At ratio of about 50% to 70% is recommended in the design of hybrid RCB girders as it provides enough post elastic strength and stiffness for meeting the ductility requirement.

The problem found in many rigid pavement concrete slabs is the occurrence of cracks. Research on the width of cracks in rigid pavement due to the influence of reinforcement ratio is necessary because the stiffness and strength of concrete slabs are related to slab thickness, concrete quality, reinforcing steel quality and reinforcement numbers. This study aims to determine the cracking behavior of rigid pavements subjected to monotonic static line loads due to variations in reinforcement ratio experimentally. Specimens tested in the laboratory were 2×0.6×0.2 m concrete slabs placed on 30 cm thick soil with 6 % CBR value as a support. The variation of reinforcement ratio was ρ=0.004; ρ=0.007; ρ=0.01; ρ=0.02. Concrete quality fc=30 MPa, steel quality fu=580 MPa. The results shows at small reinforcement ratios the results are close to the average crack width of the formula from the regulations and at large reinforcement ratios the results are further away from the average crack width based on the formula in the regulations. The largest crack width observed in this study occurred in rigid pavement with a reinforcement ratio of ρ=0.004, under a load of 210 KN, resulting in a crack width of 0.519 mm. It was found that the relationship between crack width and the reinforcement ratio follows a linear equation across all variations. The research also revealed variations in crack width between experiments conducted under different design codes, with results closely aligning with the average crack width determined by rule-based formulas, especially for a small reinforcement ratio (ρ=0.004). Conversely, for a larger reinforcement ratio (ρ=0.01), the results deviated further from the crack width predicted by the code-based formula [ABSTRACT FROM AUTHOR]

As a transfer member at the discontinuous place of vertical load, the deep beam has a complex stress mechanism and many influencing factors, such as compressive strength of concrete, shear span ratio, and reinforcement ratio. At the same time, the stress analysis principle of traditional shallow beams is no longer applicable to the design and calculation of deep-beam structure. The main purpose of this paper was to use the strut-and-tie model to analyze its stress mechanism, and to verify the applicability of the model. Nine high-strength concrete deep-beam specimens with longitudinal reinforcement with an anchor plate of the same size were tested by two-point concentrated loading method. The effects of shear span ratio (0.3, 0.6, and 0.9), longitudinal reinforcement ratio (0.67%, 1.05%, and 1.25%), horizontal reinforcement ratio (0.33%, 0.45%, and 0.50%), and stirrup reinforcement ratio (0.25%, 0.33%, and 0.50%) on the failure mode, deflection curve, characteristic load, crack width, steel bar, and concrete strain of the specimens were analyzed. The results showed that the failure mode of deep-beam specimens was diagonal compression failure. The normal section cracking load was about 15 to 20% of the ultimate load, and the inclined section cracking load was about 30~40% of the ultimate load. The shear span ratio increased from 0.3 to 0.9, and the bearing capacity decreased by 32.9%. When the longitudinal reinforcement ratio increased from 0.67% to 1.25%, the ultimate load increased by 42.6%. The shear span ratio and longitudinal reinforcement ratio have a significant effect on the bearing capacity of the high-strength concrete deep beams with longitudinal reinforcement with an anchor plate. The shear capacity of nine high-strength concrete deep-beam specimens with longitudinal reinforcement with an anchor plate was calculated by national standards, and the results were compared with the calculation results of the Tan–Tang model, the Tan–Cheng model, SSTM, and SSSTM. The analysis showed that the softened strut-and-tie model takes into account the softening effect of compressive concrete, and is a more accurate mechanical model, which can be applied to predict the shear capacity of high-strength concrete deep-beam members with longitudinal reinforcement with an anchor plate. [ABSTRACT FROM AUTHOR]

The influence of fire on self-curing reinforced concrete flat slabs was inspected in this study. In this paper the focus will be on the effectiveness of the reinforcement ratio, heat duration and cooling method on the behavior of self-curing (SCU) reinforced concrete flat slabs exposed to fire. To create SCU concrete, polyethylene glycol (PEG 400) is added at a rate of 0.5% of cement weight. Twenty-five RC plates (1200 mm x 1200 mm x 70 mm) lying on four supports and being subjected to concentrated load were used to achieve the experimental programmed. The experimental program was conducted in two stages. The first stage, the specimen exposed to high temperature (600o c) for 1 hour and 2 hours. To record the failure load and the deflections at each load increment, the load was gradually increased in the second stage. The results show that the cracking and the ultimate loads decreased, while the deflection increased either with the increase of fire flame duration and cooling method from gradually to sudden. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The torsional behavior of solid reinforced concrete (RC) members reinforced with fiber-reinforced polymer (FRP) bars has been the subject of several experimental studies. No experimental research, however, seems to have focused on RC box girders reinforced with FRP bars under a pure torsional moment. This paper reports the results of an experimental investigation on the torsional strength and behavior of full-scale RC box girders reinforced with longitudinal glass FRP (GFRP) bars. All specimens measured 380 mm (15 in.) in height, 380 mm (15 in.) in width, 100 mm (4 in.) wall thickness, and 4000 mm (157.48 in.) in length. They were tested under pure torsional loading over a clear span of 2000 mm (78.74 in.). The test specimens consisted of four RC box girders with longitudinal GFRP bars and one RC box girder with longitudinal steel bars as a reference. All the specimens were constructed without web reinforcement to study the contribution of the longitudinal reinforcement to torsional strength. The test variables included the longitudinal reinforcement ratio (ranging between 1.10 and 2.74%) and the type of longitudinal reinforcement (GFRP or steel). The test results indicate that increasing the GFRP longitudinal reinforcement ratio increased the torsional strength after the initiation of the first diagonal crack, especially for specimens with a high reinforcement ratio. In addition, theoretical torsional moment-twist curves were developed and gave predictions consistent with the experimental test results. Lastly, the ultimate torsional strength of the GFRP-RC box girders without web reinforcement was estimated with the CSA S806-12 (R2017) design equation with a modification related to the GFRP tensile strain limit. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper investigates the tensile behavior of reinforced engineering cementitious composite (ECC) members. Twelve reinforced ECC members were tested in uniaxial tension. The stress‐average strain curves, failure modes, and the strain of longitudinal reinforcement at selected sections were obtained during testing. The influence of reinforcement ratio on the load resistance and deformation capacity of members was determined. Test results showed that the tensile behavior of reinforced ECC members could be divided into three stages, namely, the elastic stage, the microcracking stage and the major cracking stage. ECC significantly contributed to the load resistance of reinforced ECC members before the formation of major cracks through tension stiffening effect. The load capacity and deformation capacity of reinforced ECC members increased with the increase of reinforcement ratios. For members with ungrooved steel bars, the ultimate load and ultimate strain increased by 130.0% and 115.2% with the reinforcement ratio increased from 1.01% to 2.26%. For members with grooved steel bars, the ultimate load and ultimate strain increased by 123.6% and 98.7% with the reinforcement ratio increased from 0.78% to 2.04%. Based on the test results, the failure mechanism of reinforced ECC members was analyzed and equations for predicting the load capacity of members were proposed. Comparisons between experimental and calculated load capacities suggested that the calculated results were in good agreement with the experimental values. The study on the tensile behavior of reinforced ECC members provides useful results for the design and application of reinforced ECC members. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) grid-reinforced ultra-high performance concrete (UHPC) slabs are new structural solutions that take advantage of the mechanical properties of FRP and UHPC. However, the punching shear behavior of this new slab type has not been characterized. Therefore, punching shear tests were conducted to eight carbon fiber-reinforced polymer (CFRP) bars or grid-reinforced UHPC square slabs (600 mm side width × 40 mm thick). Several influential factors [e.g., use of CFRP bars or grids as flexural reinforcements, type of strengthening short fiber, steel fiber (SF) content, and presence of shear reinforcements] were investigated. The test results showed that FRP grids and short fibers helped to distribute the applied loads and dissipate the input energy; therefore, more cracks were observed, and higher punching shear capacities were achieved. Furthermore, increasing the reinforcement ratio in the FRP grids led to a more significant postcrack ductility response, which increased the punching shear capacity by 17%. In addition, SF addition could enhance the initial cracking load of the slab (Vcr), and polyethylene (PE) fiber addition could intensify the postcrack ductility response, both enhanced the punching shear capacity. The installation of shear reinforcements (eight pieces of 80 mm long CFRP grid strips) appeared to be more cost-effective than increasing SF content. Finally, compared with the current design provisions for conventional reinforced concrete slabs, a more accurate (average error of 8%) punching shear model was proposed for FRP grid-reinforced UHPC slabs with or without SF additions. However, the robustness of the proposed model will be assessed with more test data in the future. [ABSTRACT FROM AUTHOR]

Ultra-high-performance geopolymer concrete (UHPGC) emerges as a sustainable and cost-effective alternative to Portland cement-based UHPC, offering similar mechanical properties while significantly reducing carbon footprint and energy consumption. Research on UHPGC components is extremely scarce. This study focuses on the flexural and crack behavior of UHPGC beams with different steel fiber contents and longitudinal reinforcement ratios. Five UHPGC beams were tested under four-point bending. The test results were evaluated in terms of the failure mode, load–deflection relationship, flexural capacity, ductility, average crack spacing, and short-term flexural stiffness. The results show that all the UHPGC beams failed due to crack localization. Increases in the reinforcement ratio and steel fiber content had favorable effects on the flexural capacity and flexural stiffness. When the reinforcement ratio increased from 1.18% to 2.32%, the flexural capacity and flexural stiffness increased by 60.5% and 12.3%, respectively. As the steel fiber content increased from 1.5% to 2.5%, the flexural capacity and flexural stiffness increased by 4.7% and 4.4%, respectively. Furthermore, the flexural capacity, flexural stiffness, and crack spacing of the UHPGC beams were evaluated using existing methods. The results indicate that the existing methods can effectively predict flexural capacity and flexural stiffness in UHPGC beams but overestimate crack spacing. This study will provide a reference for the structural design of UHPGC.

This paper presents the flexural behavior of reinforced concrete box (RCB) girders reinforced with both steel and fiber-reinforced polymer (FRP). An experimental study was conducted on five RCB girders. The first two girders were reinforced in the tension side with either steel or basalt FRP (BFRP) bars, while the other three ones were reinforced with both steel and BFRP bars with various BFRP-to-total reinforcement ratios (Af/At). The RCB girders were tested under four-point monotonic static loading and the main fundamental characteristics of the proposed reinforcement were investigated. The experimental results showed that increasing the Af/At ratio improved both the ultimate load and the deflection at failure, while the ductility index decreased. Comparing the obtained RCB test results with those found in the literature of the ordinary beams revealed that the behavior is almost identical. With the range of the experimental investigations conducted in this study, a value of about 50% to 70% for Af/At ratio is recommended in the design of hybrid RCB girders as it provides enough post elastic strength and stiffness for meeting the ductility requirement. Ultimately, the application of the analytical structural approach available in the literature was adopted to predict the flexural capacity of mixed RCB girders and good agreement with the experimental results was proved. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The concrete tensile deformation energy dissipation is of major interest for reinforced concrete uncracked section design. Extensive research, numerical and experimental, is dedicated on the concrete tension stiffening and its cracking behavior, but limited studies center on the deformation energy dissipation. A steel bar embedded in a cylindrical concrete specimen has been subjected to an axial tensile load, and the load-displacement responses recorded. A variation in concrete compression strength ranging from 32 MPa to 47 MPa has been observed. The focus of this study has been to analyze and formulate the deformation energy dissipation behavior as a function of concrete compression strength and reinforcement ratio. The experimental data have showed that the relationship followed a nonlinear ascending path with a bifurcation point, after which the curve's gradient has gradually declined. A 3D finite element model has been constructed and validated to the experimental data. The model has been developed to generate the influence of a broad range of reinforcement ratios. An equation for predicting the tensile deformation energy dissipation has been proposed based on experimental and numerical data. The equation is valid for reinforcement ratios ranging from 0.001 to 0.1 and a compression strength of 47 MPa. The equation can be utilized for section optimization purposes. [ABSTRACT FROM AUTHOR]

The Canterbury earthquake royal commission report highlighted that, despite being well-detailed, several reinforced concrete (RC) shear walls did not achieve their anticipated ductility capacities. In order to enhance the performance of such walls during future seismic events, the report recommended the use of concentrated and confined rebars at the wall toes coupled with high reinforcement ratios within the wall to initiate secondary cracks and extend the inelastic wall regions, thus minimizing the corresponding seismic demands. In this respect, the current study evaluates the seismic performance of RC walls with flanged and boundary element configurations compared with their typical rectangular counterparts, when different reinforcement ratios are incorporated. Specifically, the study presents a detailed analysis of six three-story half-scaled RC shear walls tested under quasi-static cyclic loading representing different seismic demands. The six walls were originally tested in two phases, where each phase had three different wall types (i.e., rectangular, flanged, and boundary element configurations). Walls in both phases had the same overall dimension and cross-section area; however, Phase II walls had 2.4 times the vertical reinforcement ratios used in Phase I walls. Following a summary of the experimental program and results, the current study presents the analytical results of the walls in terms of their load-strain relationships, curvature profiles, stiffness degradation trends, energy dissipation capacities, and equivalent viscous damping ratios. A comparison between the theoretical and experimental curvatures is also presented for the test walls at different drift levels. The results show that flanged and boundary element walls had low yield curvatures and high ultimate curvatures which resulted in enhancing their displacement ductility capacities. Flanged and boundary element walls also exhibited higher stiffness degradation rates when compared with their rectangular counterparts, leading to reduced seismic demands. Moreover, flanged and boundary element walls with high vertical reinforcement ratios (1.58%–1.63%) had higher energy dissipation capacities than their counterparts with low vertical reinforcement ratios (0.66%–0.69%). However, rectangular walls with low vertical reinforcement ratios (1.17%) showed higher ultimate curvature capacities than rectangular walls with high vertical reinforcement ratios (2.80%). Overall, the results demonstrate that future editions of relevant design standards (e.g., CSA A23.3 and ACI 318-19) should consider assigning different seismic design parameters (e.g., ultimate compressive strains, equivalent viscous damping ratios, and ductility-related modification factors) for RC shear walls based on their end configurations that can significantly alter the performance of such walls under seismic events. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Textile-reinforced concrete (TRC) is highly anticipated as an alternative to reinforced concrete due to its ability to enable lightweight design, free formability, and improved ductility. In this study, TRC panel test specimens were fabricated and four-point loading flexural tests were performed to examine the flexural characteristics of TRC panels reinforced with carbon fabric, and to investigate the effect of the fabric reinforcement ratio, anchorage length, and surface treatment of fabric. Furthermore, the flexural behavior of the test specimens was numerically analyzed using the general section analysis concept of reinforced concrete and compared with the experimental results. Due to bond failure between the carbon fabric and the concrete matrix, the TRC panel showed a large decrease in flexural performance in terms of flexural stiffness, flexural strength, cracking behavior, and deflection. This low performance was improved by increasing the fabric reinforcement ratio, anchoring length, and sand–epoxy surface treatment of the anchorage. Comparing the numerical calculation results with the experimental results, the deflection of the experimental results was approximately 50% larger than the numerical calculation results. This is because the perfect bond between the carbon fabric and the concrete matrix failed, and slip occurred. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cost estimation at the conceptual design stage of a building is necessary because it is considered as a fundamental input in further decision making. This paper presented a neural network method in approximating the optimum dimension and the minimum reinforcement ratio of beams and columns at the conceptual design stage of hotel buildings in Yogyakarta. A group of 27 building variations were prepared as the training data for the set up neural network model. Fourteen empirical formulas were obtained which could be used to estimate the optimum dimension and minimum reinforcement ratio of beams and columns with 5 parameters which consist of soil sites class, beam spans, number of floors, concrete strengths and diameters of the reinforcing bar.

The present study investigates the effect of Engineered Cementitious Composites (ECC) layer thickness against various reinforcement ratios on the flexural performance of reinforced ECC–concrete composite beams. In total, 20 reinforced composite beams are selected from the literature to predict their flexural response using Finite Element (FE) analysis. In addition to the FE analyses, a detailed analytical study is performed using the strain compatibility procedure to predict the flexural strength of ECC–concrete composite beams. The results from the FE analyses are compared against the experimental results and are found to show a close agreement. Using the validated FE models, detailed parametric studies are conducted to determine the effectiveness of different design parameters such as (a) ECC height replacement for a reinforcement ratio, (b) reinforcement ratio for an ECC height replacement, and (c) adequate reinforcement ratio for effective strengthening. The results of the parametric study show that the use of 0.4 ECC height replacement ratio and 1.70% steel reinforcement ratio exhibit better load‐carrying capacity in ECC–concrete composite beams. The effective tensile reinforcement ratio for the ECC–concrete composite beams from minimum to maximum varies in the range of 0.92%–1.85%, respectively. The moment capacities predicted from the section analysis is in good agreement with the experimental and numerical moment capacities. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hollow concrete columns (HCCs) are an effective structural system for piles, electric poles, and bridge piers due to their low self-weight in conjunction with the high strength offered and reduced material use. This study investigated the behavior of concentrically loaded circular HCCs reinforced with glass fiber–reinforced polymer (GFRP) bars and spirals. Eleven hollow circular columns with outer/inner diameters of 305 and 113 mm and two solid specimens as controls were fabricated. All had a height of 1,500 mm. The investigated parameters included transverse GFRP reinforcement ratio in terms of the on-center spiral spacing and spiral diameter, configuration (spiral and hoops), and the influence of hollowness. The theoretical ultimate load-carrying capacity and the confined concrete strength of the tested hollow GFRP-reinforced concrete columns were evaluated and predicted using the available design equations and confinement models in the FRP design codes, standards, and literature. The test results indicate that either decreasing the spacing of the spiral/discrete hoops or increasing the spiral diameter could increase the ultimate carrying capacity as well as improve the confinement efficiency and ductility of HCCs. [ABSTRACT FROM AUTHOR]

Ultra-high-performance concrete (UHPC) is a cement-based material with excellent impact resistance. Compared with traditional concrete, it possesses ultra-high strength, ultra-high toughness, and ultra-high durability, making it an ideal material for designing structures with impact resistance. The research on the impact resistance performance of UHPC and its composite structures is of great significance for the structural design of protective engineering projects. However, currently, there is still insufficient research on the impact resistance performance of UHPC composite structures. To study the impact resistance performance, experiments were conducted on UHPC targets using high-speed projectiles. The results were compared with impact tests on granite targets. The results indicated that when subjected to projectile impact, the UHPC targets exhibited smaller surface craters compared with the granite targets, while the penetration depth was lower in the granite targets. Afterwards, the process of a projectile impacting the UHPC composite structure was numerically simulated using ANSYS 16.0/LS-DYNA finite element software. The numerical simulation results of penetration depth and crater diameter were in good agreement with the experimental results, which indicates the rationality of the numerical model. Based on this, further analysis was carried out on the influence of impact velocity, impact angle, and reinforcement ratio on the penetration depth of the composite structure. The results show that the larger the incident angle or the smaller the velocity of the projectile is, the easier it is to deflect the projectile. There is a linear relationship between penetration depth and reinforcement ratio; as the reinforcement ratio increases, the penetration depth decreases significantly. This research is of great significance in improving the safety and reliability of key projects and also contributes to the application and development of ultra-high-performance materials in the engineering field.

The cyclic out-of-plane behavior of unreinforced masonry (URM) walls strengthened with externally bonded glass fiber-reinforced polymer (GFRP) strips is experimentally studied in this paper. A total of four fired clay brick masonry walls were prepared in this study. Three walls were seismically retrofitted by bonding vertical GFRP strips and one specimen was unreinforced and was used as built. All masonry walls were subjected to one-directional cyclic out-of-plane lateral loadings. The lateral cyclic out-of-plane behavior in terms of failure patterns, force-displacement behavior, ultimate strength and displacement capacity, secant stiffness, and hysteretic energy dissipation of each specimen was studied. The test results indicate that externally bonded vertical GFRP retrofitting significantly improves the cyclic out-of-plane performance of brick masonry walls. The ultimate out-of-plane flexural and displacement capacity of strengthened walls was increased up to 1000% and 300%, respectively, compared to the companion URM wall. Based on the principles of strain compatibility and internal force equilibrium, an analytical model is proposed for calculating the ultimate out-of-plane flexural capacity of GFRP-strengthened walls for different failure patterns. In addition, several design recommendations, such as the strain in GFRP strips at delamination failure and the maximum and minimum GFRP reinforcement ratio, were proposed based on strain compatibility. [ABSTRACT FROM AUTHOR]

The investigation of the structural performance of reinforced concrete members in the construction process has become a critical issue for Hybrid GFRP bars with steel bars. The ultimate concrete shear strength of reinforced concrete beams contains both GFRP bars and Steel bars in main reinforcement are a main task of work. This paper examines the effect of sharing the fiber-reinforced polymer (FRP) bars with steel bars for reinforced concrete (RC) structures on the concrete shear strength of RC beams. Fourteen RC beams without shear reinforcement were constructed and tested up to failure. The test beams included two steel-RC beams, one GFRP-RC beam, and eleven steel bars and GFRP bars (hybrid GFRP/steel)-RC beams. The main parameters were the reinforcement ratio, shear span to depth ratio, depth of the beam, concrete compressive strength, and compression reinforcement. The test results are presented in terms of crack patterns, failure modes, load-deflection, and load-strain behavior. The test results showed that hybrid GFRP/steel bars causing significant improvement in the ductility with reduction of the deformation comparing with an only steel bar in main steel in tested beams. The dowel action can play a major role in the process by which shear is carried in a beam. Finally, the initial proposal equation that calculates the shear strength of hybrid reinforced elements can serve as a guideline for the introduction of hybrid bars (GFRP and Steel) at the main reinforcement in RC beams.