Shear Capacity Of Beams Research Articles

A Review on Mechanism and Influencing Factors of Shear Performance of UHPC Beams

Ultra-High-Performance Concrete (UHPC) is increasingly used in various engineering projects due to its exceptional mechanical properties. This work conducts a literature review of research on the shear performance of UHPC beams in recent decades, with a focus on summarizing the formulas for calculating shear capacity and the main factors influencing shear performance. Firstly, this work reviews the calculation methods for the shear capacity of UHPC beams in different countries, along with their respective advantages and limitations. Subsequently, it provides a detailed analysis of various factors influencing the shear performance of UHPC beams, including longitudinal and stirrup reinforcement, steel fiber content, aggregates, admixtures, the shear-span ratio, shear keys, bolts, shear-reinforcement techniques, and environmental impacts. Through horizontal comparisons, the performance of UHPC beams and ordinary concrete beams under similar experimental conditions is examined to reveal the optimal shear working conditions for UHPC beams. Additionally, it is found that UHPC performs exceptionally well in composite beams, being compatible with numerous materials and significantly enhancing the shear strength of these beams. Lastly, the paper proposes suggestions for maximizing the shear performance of UHPC beams within a safe and reliable operating range and outlines future research directions.

The Effect of Fiber Type on The Shear Capacity of Beams Manufactured By Using Geopolymer Concrete Based on Fly Ash

Ordinary Portland cement is currently generally used cementitious material in the construction industry. However, it has significant drawbacks as it not only depletes natural resources but also releases a substantial amount of carbon dioxide during its production process. On the other hand, alkali-activated cement is an alternative option that is derived from raw materials like slag, fly ash, and metakaolin, which contain silicon dioxide (SiO2) and aluminum oxide (Al2O3). This study investigates the shear capacity of fibre-reinforced geopolymer concrete (GPC) beams under shear loads. In the study, the shear behavior of beams produced from fly ash-based geopolymer of three different fiber types was determined by applying a three-point shear test. Four beams of 100x100x400 mm dimensions were produced: reference, steel fiber, basalt fiber and glass fiber. The results showed that using steel fiber has the greatest impact on shear capacity. In addition, the shear capacity of fibrous samples is greater than the shear capacity of the reference sample. The steel fiber sample has 203% more shear capacity than the reference sample.

Concept and Experimental Validation of Using Titanium Alloy Bars (TiABs) as Flexural Reinforcing in Concrete Beams

The research focuses on the use of Titanium Alloy Bars (TiABs) in concrete cap beams. TiABs offer good ductility, high strength, lightweight, superior corrosion resistance, lower overstrength, and better fatigue performance. TiABs have recently been used in several existing bridges in Oregon and Texas in the United States to increase shear and flexural capacities of concrete beams. While TiABs have been implemented in retrofitting of existing bridges in the United States, their application in new structures have not been tested and compared against conventional steel rebars. The research in this paper proposes concept for an innovative cap beam reinforced with longitudinal TiABs. The cap beam integrates both structural performance and durability. Flexural and shear design procedures for the cap beam in accordance with the AASHTO LRFD Design are discussed. To investigate structural performance, a large-scale cap beam reinforced with longitudinal grade 5 titanium alloy (Ti-6Al-4V) is tested under three-point bending test protocol. The results are compared against a benchmark cast-in-place beam with normal rebars under the same testing arrangement and loading protocol.

Shear capacity of slender FRP-RC beams utilizing a hybrid ANN with the firefly optimizer

The popularity of fiber-reinforced polymer (FRP) bars as a structural element has soared due to their advantageous mechanical and physical properties. Despite an abundance of code requirements and heuristic equations, engineers specializing in structural retrofitting and analysis often struggle to utilize a suitable yet precise equation. This study introduces a novel approach by presenting a firefly optimization algorithm (FOA) combined with an artificial neural network (ANN)—termed as FOA-ANN—as an advanced hybrid machine learning model. The primary objective is to predict the shear capacity of slender FRP reinforced concrete (FRP-RC) beams without stirrup. An extensive experimental database of slender FRP-RC beams without stirrup was compiled. Leveraging this database and the proposed hybrid method, a simple yet accurate closed-form equation for determining the shear capacity of slender FRP-RC beams without stirrup was formulated. Additionally, a selection of pre-existing equations was provided for comparison of accuracy. Results indicate that the suggested FOA-ANN equation offers a more accurate alternative, outperforming equations derived from CSA S806-12 and AASHTO LRFD. The FOA-ANN hybrid technique proves to be highly effective in predicting the shear capacity of slender FRP-RC beams without stirrup.

Effectiveness evaluation of different steel fibers on the shear strength of reinforced SFRC slender beams without web rebars

Current studies have mainly focused on the effect of specific steel fibers on the shear performance of steel fiber-reinforced concrete (SFRC) slender beams. However, there has been a lack of in-depth research evaluating the effectiveness of different steel fibers through a statistically comparative analysis of experimental data from various researchers. Existing design methods do not fully account for the impact of all types of steel fibers on the shear capacity of SFRC slender beams, providing very limited guidance on selecting appropriate steel fibers. This highlights the need for research to verify the strengthening effectiveness of different steel fibers. This paper establishes databases comprising 232 shear-failed reinforced SFRC beams with four other types of steel fibers straight wire, deformed wire, deformed cut-sheet and ingot mill, based on a comprehensive review of published literature. These databases complement an existing database of 280 reinforced SFRC beams using hook-end wire steel fibers as shear reinforcement. The databases are used to evaluate the validity of several well-known existing formulas for predicting the shear capacity of beams and to determine the fiber bond factor values that reflect the diverse strengthening effects of different steel fibers. Utilizing a simi-empirical synergetic prediction model for the shear strength of reinforced SFRC slender beams with hook-end wire steel fibers, the shear resistances of test beams in databases with the other four types of steel fiber are analyzed. The primary contributors to shear capacity are identified as the uncracked shear-compression SFRC and the dowel action of longitudinal tensile steel bars. The contribution of steel fibers is linked to the shear resistance of uncracked shear-compression SFRC. From a practical design perspective, a conservative prediction formula is verified, aligning with the lower boundary of the tested shear strength obtained from the database of beams. Finally, suitable steel fibers for s enhancing the shear strength of reinforced SFRC beams without web rebars are suggested based on their effectiveness.

Shear performance and capacity of FRP reinforced concrete beams: Comprehensive review and design evaluation

To enhance the durability of concrete structures in harsh environments, replacing steel bars with FRP bars is judged a feasible method. The low elastic modulus and transverse strength of FRP bars result in the weak shear capacity of concrete beams reinforced with FRP bars. Reviewing and summarizing existing literature are important for addressing this challenge. The research progress on the shear behaviour of concrete beams reinforced with FRP bars was systematically described from two aspects in this paper. In the aspect of literature review, shear mechanisms and main influencing factors of concrete and FRP stirrups were summarized. In addition, achievements and shortcomings of existing literature were summarized, and potential research directions were pointed out. In the aspect of design method evaluation, a database containing 525 samples was established and calculation models of shear capacity of concrete beams reinforced with FRP bars in seven codes were evaluated. Evaluation parameters mainly included shear span ratio, effective height, and maximum strain of FRP stirrups. Based on the calculation model in Italian code CNR DT203-06, an optimized model was proposed to improve the accuracy in predicting concrete shear contribution. The review and evaluation in this paper had important reference significance for improving the design level of concrete structures reinforced with FRP bars and promoting the engineering application of FRP bars.

Shear Behavior of High-Strength and Lightweight Cementitious Composites Containing Hollow Glass Microspheres and Carbon Nanotubes

In this study, an experimental program was conducted to investigate the shear behavior of beams made of high-strength and lightweight cementitious composites (HS-LWCCs) containing hollow glass microspheres and carbon nanotubes. The compressive strength and dry density of the HS-LWCCs were 87.8 MPa and1.52 t/m3, respectively. To investigate their shear behavior, HS-LWCC beams with longitudinal rebars were fabricated. In this test program, the longitudinal and shear reinforcement ratios were considered as the test variables. The HS-LWCC beams were compared with ordinary high-strength concrete (HSC) beams with a compressive strength of 89.3 MPa to determine their differences; the beams had the same reinforcement configuration. The test results indicated that the initial stiffness and shear capacity of the HS-LWCC beams were lower than those of the HSC beams. These results suggested that the low shear resistance of the HS-LWCC beams led to brittle failure. This was attributed to the beams’ low elastic modulus under compression and the absence of a coarse aggregate. Furthermore, the difference in the shear capacity of the HSC and HS-LWCC beams slightly decreased as the shear reinforcement ratio increased. The diagonal compression strut angle and diagonal crack angle of the HS-LWCC beams with shear reinforcement were more inclined than those of the HSC beams. This indicated that the lower shear resistance of the HS-LWCCs could be more effectively compensated for when shear reinforcement is provided and the diagonal crack angle is more inclined. The ultimate shear capacities measured in the tests were compared with various shear design provisions, including those of ACI-318, EC2, and CSA A23.3. This comparison showed that the current shear design provisions considerably overestimate the contribution of concrete to the shear capacity of HS-LWCC beams.

Shear behavior of reinforced concrete beams with high-strength reinforcements after high temperatures

This paper investigates the effect of steel reinforcement configured with different strengths after different high temperatures on the shear performance of the test beams, a total of 20 reinforced concrete (RC) beams, through experiments, numerical analyses and theoretical studies, in order to understand the key factors affecting the shear performance of the beams. The test revealed that the mechanical properties of concrete and steel reinforcement showed a trend of increasing and then decreasing after high temperatures. Increasing the stirrup ratio and stirrup strength can significantly improve the crack resistance and shear capacity of the beams, as well as the deformation performance of the beams. The residual shear strengths of test beams with high-strength stirrups after exposure to high temperatures are significantly greater than those of ordinary reinforced concrete beams. Specifically, the shear capacity of beams with high-strength stirrups after exposure to 800°C increased by 23.7 % compared to ordinary beams, and the mid-span deflection performance increased by 28.7 %. The stresses in the shear span region of the test beams after high temperature were more concentrated at the diagonal and the number of cracks was significantly reduced. In this paper, a simplified formula for calculating the residual shear capacity of RC beams after room and high temperatures is proposed, which can well predict the test results.

Predicting shear strength of fiber-reinforced concrete beams reinforced with longitudinal FRP bars with machine learning techniques

ABSTRACT This study investigates the shear strength prediction of Fibre-Reinforced Concrete (FRC) beams reinforced with Fibre-Reinforced Polymer (FRP) bars and without stirrups through the application of Machine Learning (ML) techniques. The utilisation of FRP bars, particularly Glass Fibre-Reinforced Polymer (GFRP) and Basalt Fibre-Reinforced Polymer (BFRP) bars, has emerged as a promising alternative to traditional steel reinforcement due to their superior mechanical properties and corrosion resistance. Moreover, the incorporation of macro- and micro-discrete fibres into concrete compositions enhances both shear and flexural behaviour while reducing crack propagation induced by tensile stresses. The primary objective of this research is to develop accurate predictive models for the shear capacity of FRP-reinforced concrete beams, considering various influential parameters. Six different ML techniques, namely Multiple Linear Regression (MLR), Gaussian Process Regression (GPR), k-Nearest Neighbors (KNN), Support Vector Machines (SVMs), Artificial Neural Networks (ANNs) and Random Forest Regression (RFR), are employed to analyse the complex interactions between input variables, such as fibre type, bar diameter, concrete compressive strength, beam dimensions and the resulting shear strength. By leveraging these computational approaches, we aim to overcome the limitations of conventional analytical methods and provide robust predictions for structural design and optimisation.

Performance Prediction of GFRP-Reinforced Concrete Deep Beams Containing a Web Opening in the Shear Span

This study aimed to investigate the nonlinear structural behavior of concrete deep beams internally reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars and containing a web opening of various sizes and locations within the shear span. Three-dimensional (3D) numerical simulation models were developed for large-scale GFRP-reinforced concrete deep beams (300 mm × 1200 mm × 5000 mm) with a shear span-to-depth ratio (a/h) of 1.04. Predictions of the numerical models were validated against published experimental data. A parametric study was conducted to examine the effect of varying the opening size and location on the shear response. Results of the numerical analysis indicated that the strength of the deep beam models with an opening in the middle of the shear span decreased with an increase in either the opening width or height. The rate of the strength reduction caused by increasing the opening height was, however, more significant than that produced by increasing the opening width. Placing a web opening in the compression zone close to the load plate was very detrimental to the beam strength. Conversely, a negligible strength reduction was recorded when the web opening was placed in the tension side above the flexural reinforcement and away from the natural load path. Data of the parametric study were utilized to introduce simplified analytical formulas capable of predicting the shear capacity of GFRP-reinforced concrete deep beams with a web opening in the shear span.

Shear strengthening of self-compacting lightweight concrete beams with steel fibers and unbonded prestressing bars

This study aims to investigate the shear behavior of self-compacting lightweight concrete (SCLC) beams strengthened with steel fibers and unbonded prestressing bars. For this, the experimental program included the use of hooked-end steel fibers with volume fractions of 0.5 %−0.75 %, and high-strength prestressing bars with varying prestressing forces and transverse reinforcement ratios. The addition of steel fibers in SCLC significantly increased the normalized shear capacity of beams, reaching up to 2.50 times higher values, whereas the substitution of normal coarse aggregates with lightweight aggregate resulted in a decrease of up to 10.1 %. The shear strengthening of SCLC beams with unbonded prestressing bars provided a substantial increase in the ultimate shear capacity up to 2.06 times higher than that of beam without reinforcement. Increasing the prestressing force of bars effectively restrained the occurrence of critical shear cracking, consequently enhancing the shear capacity. Utilizing hybrid reinforcement with fibers and prestressing bars resulted in a transition of failure mode from shear to flexural, attributed to the improved shear capacity. For the SCLC beams reinforced with steel fibers, the shear strengths were predicted by previous prediction models. When modifier for lightweight concrete was considered, the Imam’s model most precisely predicted the shear strengths with an average vu/vn ratio of 1.00 and SD of 0.07. The fib model Code, based on the modified compression field theory, provided accurate predictions for the shear capacities of SCLC beams with unbonded prestressing bars, exhibiting an average Vu/Vn ratio of 1.00 and SD of 0.09. The fiber-resisting component was reasonably considered in the model with an average Vu/Vn ratio of 1.02 and SD of 0.07.

Five Machine Learning Models Predicting the Global Shear Capacity of Composite Cellular Beams with Hollow-Core Units

The global shear capacity of steel–concrete composite downstand cellular beams with precast hollow-core units is an important calculation as it affects the span-to-depth ratios and the amount of material used, hence affecting the embodied CO2 calculation when designers are producing floor grids. This paper presents a reliable tool that can be used by designers to alter and optimise grip options during the preliminary design stages, without the need to run onerous calculations. The global shear capacity prediction formula is developed using five machine learning models. First, a finite element model database is developed. The influence of the opening diameter, web opening spacing, tee-section height, concrete topping thickness, interaction degree, and the number of shear studs above the web opening are investigated. Reliability analysis is conducted to assess the design method and propose new partial safety factors. The Catboost regressor algorithm presented better accuracy compared to the other algorithms. An equation to predict the shear capacity of composite cellular beams with hollow-core units is proposed using gene expression programming. In general, the partial safety factor for resistance, according to the reliability analysis, varied between 1.25 and 1.26.

Shear behavior of seawater sea-sand concrete beams reinforced with BFRP bars after seawater dry-wet cycling

The shear behavior of 27 basalt fiber-reinforced polymer reinforced seawater sea-sand concrete (BFRP-SSC) beams after seawater dry-wet cycling was comprehensively investigated. Parameters considered included stirrup diameter and spacing, shear span-to-depth ratio, stirrup surface treatment, cycling duration, concrete cover thickness, and seawater temperature. Results indicate that seawater dry-wet cycling increases cracking load and decreases bending stiffness in BFRP-SSC beams. Increasing shear span-to-depth ratio from 1.55 to 2.35 led to load reductions of 31.3 % and 49.7 % at 6.5 mm mid-span deflection. Seawater dry-wet cycling, particularly temperature and duration, significantly impacts the mechanical properties of stirrups. This results in diminished shear contribution and reduced efficacy in inhibiting diagonal crack propagation, leading to a shift in beam failure mode from diagonal compression failure to shear compression failure and diagonal tension failure. Increasing cycling duration from 60 to 120 days decreased tensile strength retention by 19.1 % and 33.3 % respectively. Based on experimental data, Arrhenius theory, and the time shift factor (TSF) method, a predictive model was developed for the shear capacity retention of beams subjected to seawater dry-wet cycling. Results indicate that after 100 years in a tidal environment (70 % and 90 % relative humidity), shear capacity damage factors of 0.77 and 0.52, respectively, can be applied to account for the impact of seawater dry-wet cycling on the shear capacity of BFRP-SSC beams.

Retrofitting intact and heat-damaged shear-deficient concrete beams using CFRP ropes and dowels

The potential for recovering the shear capacity of heat-damaged beams using carbon-fibre-reinforced polymer (CFRP) ropes was investigated using 12 concrete beams (150 × 250 × 1450 mm3) with shear reinforcement deficiency. Six beams were heated for 2 h at a temperature of 400°C; the others were not heated. All the beams were retrofitted with near-surface mounted CFRP ropes as external U-shaped stirrups, inserted in vertical holes (embedded through reinforcement) or implemented as a hybrid system of both. Lateral dowels were implanted in concrete along with schemes involving U-shaped stirrups to improve resistance against cover separation and shear failure, respectively. The mechanical behaviour of the beams was evaluated under three-point loading, with data collected and analysed to characterise the load–deflection relationships. Cracking and failure modes were analysed. For the heat-damaged beams, the adopted schemes restored load capacity and improved toughness and ductility, but not flexural stiffness. Moreover, implementing ropes as U-shaped external stirrups, terminating 20 mm below the top surface of the beams, helped avert side-cover separation, yet resulted in horizontal shear failure at the level of the upper concrete cover of the damaged beams. The residual strain induced in the U-shaped external stirrups was 14–40%, which is compatible with those reported in other works adopting similar repair methodologies.

Shear resistance test analysis and calculation method of shear capacity of UHPC-NC beam without web reinforcement

In order to study the failure phenomenon and shear resistance performance of UHPC-NC beams without web reinforcement, shear resistance tests were carried out on 15 UHPC-NC beams without web reinforcement. The variation parameters were shear span ratio, web thickness, steel fiber content, and compressive stress level. The load-deflection curve, failure phenomenon and crack development of the test beam are analyzed. The test results show that the joint between the top plate and the bottom plate of UHPC-NC I-beam without web reinforcement is the weakest, and the cracked web is easy to be “cut off” at the joint; The “banding crack area” of web is closely related to the shear span ratio, and the width of ribbon area increases with the increase of shear span ratio. The shear capacity of UHPC-NC I-beam without web reinforcement decreases with the increase of shear-span ratio. The shear capacity increases with the increase of web thickness and compressive stress level. The shear capacity has little relationship with steel fiber content, and the initial stiffness of the structure can be improved by applying prestress. Finally, considering the influence of the top slab compression-shear zone and the bottom slab tension-shear zone on the shear capacity of UHPC-NC prestressed composite beams without web reinforcement, the corresponding calculation method of shear capacity is given based on the modified compression field theory and the idea of sub-item superposition, and the applicability of the calculation method is verified by the test results.

Analytical Model for Calculating Shear Capacity of NSC Beams Strengthened by UHPC Lateral Layers

Analytical Model for Calculating Shear Capacity of NSC Beams Strengthened by UHPC Lateral Layers

Shear performance and strength of reinforced concrete non-prismatic beams with basalt fiber reinforced polymer rebars

Tapered beams, which are horizontal structural elements, possess varying moments of inertia across their length. Among these, the pier cap mode is widely employed in engineering applications. This research explores the influence of incorporating basalt fiber reinforced polymer (BFRP) bars on the shear strength of eight concrete haunched beams. While two of these beams were straight beams, the others have different inclination angles. The study aimed to examine two main factors: the angles of tapered part in the compression chord and the effect of BFRP stirrups. Results from the experiment revealed a direct correlation between increasing tapered angles and the enhancement of shear capacity in haunched beams. Consequently, a comprehensive analysis was conducted using three different codes, leading to the formulation of proposed equations derived from semi-empirical methods. The analysis demonstrated a high level of accuracy in predicting shear strength with a satisfactory safety margin.

Experimental Investigation on Shear Behavior of Non-Stirrup UHPC Beams under Larger Shear Span–Depth Ratios

Due to the extraordinary mechanical properties of ultra-high-performance concrete (UHPC), the shear stirrups in UHPC beams could potentially be eliminated. This study aimed to determine the effect of beam height and steel fiber volume content on the shear behavior of non-stirrup UHPC beams under a larger shear span–depth ratio (up to 2.8). Eight beams were designed and fabricated including six non-stirrup UHPC beams and two comparing stirrup-reinforced normal concrete (NC) beams. The experimental results demonstrated that the steel fiber volume content could be a crucial factor affecting the ductility, cracking strength, and shear capacity of non-stirrup UHPC beams and altering their failure modes. Additionally, the height of the beam had a considerable effect on its shear resistance. French standard formulae were more accurate for the UHPC beams with larger shear span–depth ratios, PCI-2021 formulae greatly overestimated the shear capacity of UHPC beams with larger shear span–depth ratios, and Xu’s formulae were more accurate for the steel fiber-reinforced UHPC beams with larger shear span–depth ratios. In summary, French standard formulae were the most suitable formulae for predicting the shear capacity of UHPC beams in this paper.

Experimental and numerical analysis on shear capacity of steel-reinforced geopolymer concrete beams with different shear span ratios

PurposeThe purpose of this study is to use the corrected stress field theory to derive the shear capacity of geopolymer concrete beams (GPC) and consider the shear-span ratio as a major factor affecting the shear capacity. This research aims to provide guidance for studying the shear capacity of GPC and to observe how the failure modes of beams change with the variation of the shear-span ratio, thereby discovering underlying patterns.Design/methodology/approachThree test beams with shear span ratios of 1.5, 2.0 and 2.5 are investigated in this paper. For GPC beams with shear-span ratios of 1.5, 2.0 and 2.5, ultimate capacities are 337kN, 235kN and 195kN, respectively. Transitioning from 1.5 to 2.0 results in a 30% decrease in capacity, a reduction of 102kN. Moving from 2.0 to 2.5 sees a 17% decrease, with a loss of 40KN in capacity. A shear capacity formula, derived from modified compression field theory and considering concrete shear strength, stirrups and aggregate interlocking force, was validated through finite element modeling. Additionally, models with shear ratios of 1 and 3 were created to observe crack propagation patterns.FindingsFor GPC beams with shear-span ratios of 1.5, 2.0 and 2.5, ultimate capacities of 337KN, 235KN and 195KN are achieved, respectively. A reduction in capacity of 102KN occurs when transitioning from 1.5 to 2.0 and a decrease of 40KN is observed when moving from 2.0 to 2.5. The average test-to-theory ratio, at 1.015 with a variance of 0.001, demonstrates strong agreement. ABAQUS models beams with ratios ranging from 1.0 to 3.0, revealing crack trends indicative of reduced crack angles with higher ratios. The failure mode observed in the models aligns with experimental results.Originality/valueThis article provides a reference for the shear bearing capacity formula of geopolymer reinforced concrete (GRC) beams, addressing the limited research in this area. Additionally, an exponential model incorporating the shear-span ratio as a variable was employed to calculate the shear capacity, based on previous studies. Moreover, the analysis of shear capacity results integrated literature from prior research. By fitting previous experimental data to the proposed formula, the accuracy of this study's derived formula was further validated, with theoretical values aligning well with experimental results. Additionally, guidance is offered for utilizing ABAQUS in simulating the failure process of GRC beams.

Interface Shear Capacity and Flexural Performance of Hybrid Beams

Interface Shear Capacity and Flexural Performance of Hybrid Beams