ABSTRACT This study investigates the shear performance of ultra-high-performance concrete deep beams (UHPC-DBs) reinforced with hybrid fibers comprising 5D steel fibers and Forta-Ferro (FF) synthetic fibers. UHPC-DBs are widely used in bridges, piles, and transfer girders because of their high load-bearing capacity. Although fiber content strongly influences shear behavior, the contribution of synthetic fibers in hybrid systems remains insufficiently understood. To address this gap, finite element analysis based on the concrete damage plasticity (CDP) model was developed in ABAQUS and validated using experimental results from five previously tested UHPC-DBs with different fiber contents. Load – deflection response, crack patterns, shear capacity, mid-span deflection, fiber stress, and ductility were evaluated. Particle swarm optimization (PSO) was employed to identify the optimal hybrid fiber combination considering both shear performance and cost efficiency. Results indicate that a hybrid system containing 1.0% 5D steel fibers and 0.11% FF synthetic fibers provides the best performance-to-cost ratio, improving shear strength and ductility. Furthermore, UHPC-DBs reinforced with 1.0–2.5% steel fibers combined with 0.55% FF synthetic fibers achieved 92.83–99.19% of the shear capacity of beams reinforced solely with 1.5–3.0% steel fibers. These findings demonstrate the effectiveness of hybrid fiber reinforcement and support updating ACI 318–19 to account for synthetic fiber contributions practice.

Shear properties of UHPC hollow beams with glazed hollow beads

Shear capacity evaluation and buckling mechanisms of composite I-girders with corrugated steel webs

Developing machine learning models for estimating the shear capacity of barbell squat shear walls under seismic forces

A Gaussian Process Regression (GPR) model was developed to predict the shear capacity of exterior reinforced concrete (RC) beam-column joints subjected to seismic loading. The model accounts for key parameters, including beam and column geometry, reinforcement detailing, axial column load, and concrete compressive strength. A database of 273 experimentally tested specimens was used, with emphasis on horizontal joint shear strength. Three kernel structures within the GPR framework-Primary, Rational Second-Order, and Combined kernels-were examined. Model predictions were evaluated against existing shear-strength formulations using deterministic metrics (MAE, RMSE, and R2) and probabilistic measures (NLPD and MSLL). The results show that kernel effectiveness depends on model formulation; however, the Combined kernel exhibited more stable predictions and improved uncertainty calibration for models with higher-dimensional input sets. Sensitivity analysis identified concrete compressive strength, beam depth, and joint transverse reinforcement as dominant variables, followed by column height, axial load ratio, and reinforcement configuration. Overall, the proposed framework enables consistent shear-strength prediction and quantifies the relative influence of geometric and material parameters, contributing to more informed assessment and design of RC beam-column joints.

The concrete-rock interface plays a critical role in governing stability of concrete gravity dams. Existing design practices rely on mapped joint roughness coefficient (JRC) values that neglect both excavation-induced damage and displacement-dependent degradation resulting in unconservative overestimation of interface shear capacity. This study integrates 56 in-situ direct shear tests on Class I and II behavior rocks with displacement-dependent numerical modeling. Effective JRC values back-calculated from in-situ direct shear tests using the Barton-Bandis criterion revealed reductions of 40% (Class II) and 22% (Class I) relative to mapped JRC values that is attributed to excavation-induced damage. A two-stage model capturing hyperbolic pre-peak JRC mobilization and exponential post-peak degradation is presented and validated against in-situ measurements (R2 = 0.92 and 0.89 respectively). The validated interface is implemented for a 140 m concrete gravity dam using 20 recorded seismic acceleration time histories representative of the regional seismic hazard. Under 1.0g peak ground acceleration interface shear stress reached 5.32 MPa with 968 mm permanent displacement. Seismic fragility analysis indicated a median peak ground acceleration of 0.213g for serious damage at 50% exceedance probability. The results indicate that conventional approaches are less conservative. The presented field-validated approach provides a reasonable method for performance-based seismic risk assessment of concrete gravity dams in tectonically active regions. Further work incorporating cyclic shear testing, CNS boundary conditions, three-dimensional modeling and long-term bond degradation effects is recommended to enhance the reliability of the presented framework.

When reinforced concrete (RC) slabs are subject to low velocity impacts (LVI), they will experience highly non-linear behaviors based upon the combined effects of flexural deformations; tensile membrane actions; punching shears; and local crushing as well as the evolving nature of damage in these structures. Most analytical models have been developed under restrictive simplifications; lack complete partitioning of energies; and depend heavily upon computationally intensive finite element simulations. An analytical-energy-based approach is presented to predict the non-linear dynamic behavior of RC slabs subjected to both LVIs and equivalent blast loads. The proposed model integrates an improved two degree-of-freedom (2-DoF) dynamic interaction system with an explicit multi-mechanism energy partitioning procedure which can be used to quantify all of the major forms of energy consumption including flexural; membrane; shear; crushing; damping and damage. The analytical framework has incorporated strain rate enhancement through use of dynamic increase factors (DIFs); punching shear capacity through application of the critical shear crack theory (CSCT); and geometrically non-linear membrane behavior via Xie's formulation for large deflection membrane behavior. A wide-ranging parametric analysis was performed to examine the effect of impact energy; slab thickness; reinforcement ratio; boundary conditions and advanced materials systems such as normal strength concrete (NSC); ultra high-performance concrete (UHPC); and ultra high-performance fibre reinforced concrete (UHPFRC). Results indicated that an increase in the magnitude of impact energy from 1 to 6kJ resulted in an approximate 301% increase in slab displacement. Furthermore, an increase in the slab thickness from 60 to 125mm resulted in a reduction of approximately 68% in slab displacement. It was also found that when compared with RC slabs made with NSC, those made with UHPFRC had displacements decreased by approximately 61% and reduced damage dissipation energy by approximately 69% due to higher levels of crack bridging and membrane resistance. Lastly, it was determined that twisted and hooked end fibres had the greatest energy absorbing capability and provided the longest delay to punching shear failure. Validation studies were conducted against existing experimental data and comparative non-linear ABAQUS CDP simulations indicating prediction error margins generally less than ± 5-10% and good correlation in terms of slab displacement response; crack development; and failure progression. The validation studies also showed that the method could be easily adapted for equivalent blast load analyses using impulse equivalency principles thus enabling a rapid predictive tool for designing RC slab systems resistant to either low velocity impact or blast loads.

ABSTRACT For the elucidation of the shear capacity and energy dissipation characteristics of composite specimens of carbon fiber reinforced polymer (CFRP) and concrete filled steel tubular (CFST), and the clarification of the evolution law of hysteretic behavior of CFRP-CFST specimens under combined compression and shear stress, nine compression and shear specimens were designed and fabricated for systematic tests. The shear-displacement hysteretic curve. According to the test results, the circumferential constraint of the steel tube coupled with the transverse reinforcement of CFRP could effectively complement each other, jointly limit the lateral expansion of concrete, and improve the shear stiffness and ductility of specimens. Hence, the effects of two key parameters, axial compression ratio and transverse restraint coefficient of CFRP, on the specimens’ mechanical properties were further studied. ABAQUS was adopted for simulating the V-Δ curve. Under the dual support of test and simulation, the whole stress process of the component materials is analyzed theoretically, and the stress transfer path and damage evolution law of each material in different stress stages are revealed. In addition, the coupling effects of transverse CFRP layers, yield strength of reinforcement, strength grade of concrete, steel ratio and axial compression ratio on hysteretic behavior of specimens are discussed.

• Opening location primarily determines shear capacity in stirrup-less beams. • Large openings placed near supports reduce shear strength by up to 80%. • Square openings cause greater capacity loss than circular shapes. • Post-cracking energy absorption drops by over 80% for large openings. • A unified geometry-based model predicts shear capacity reduction. This study quantifies the influence of web‑opening shape, size, and location, as well as the shear span, on the shear capacity of reinforced concrete (RC) beams without transverse reinforcement. A nonlinear finite‑element (FE) model was validated against published experimental results and used to conduct a systematic parametric investigation of simply supported beams containing circular and square openings with opening‑to‑depth ratios (dₒ/H = 0.2, 0.4, and 0.6). Openings were placed at multiple normalized locations (x/a) along the shear span for (a/d) = 2.7, 5.5, and 8.2. The FE model reproduced the experimental peak loads and corresponding deflection within ±2% (one deflection outlier: +11%). Results indicate that opening effects are strongly coupled with size and location. At a/d=2.7, openings with dₒ/H=0.4 placed at critical locations reduced peak load by 36% (circular) and 41% (square), whereas openings with dₒ/H=0.6 reduced peak load by 70% and 80%, respectively. Small openings (dₒ/H = 0.2) resulted in a negligible reduction. Most cases showed that the maximum shear capacity losses were close to the supports and decreased toward the loading point. An empirical geometry-based solution is proposed to estimate the reduction in shear capacity and provide quantitative limits for the placement of support openings.

• Experimental assessment of punching shear behavior in RC slabs supported by embedded square CFST columns. • Evaluation of multiple strengthening techniques including steel bolts, welded bars, hybrid systems, and prestressing. • Strengthening methods increased punching capacity up to 5.47 times and energy absorption up to 10.49 times. • Strengthened connections exhibited a clear transition from brittle punching to ductile failure modes. • A validated nonlinear finite element model accurately predicts the behavior of strengthened CFST–RC slab connections. The increasing use of concrete-filled steel tube (CFST) columns in modern construction highlights the critical need to understand and enhance punching shear resistance at RC slab-column connections. This study presents an experimental and numerical investigation into the punching shear behavior of square RC slabs supported by embedded square CFST columns, focusing on novel and adapted strengthening techniques. Thirteen RC slab specimens were subjected to concentrated loading from a central embedded CFST column stub. The study systematically evaluated the effectiveness of various strengthening methods, including embedded steel bolts with varying lengths, welded steel bars around the column perimeter, combined bolt and welded bar configurations, and the application of a prestressing system. The experimental results demonstrate that these techniques significantly enhance the punching shear capacity and modify the failure characteristics compared to the control slab. Strengthening methods successfully transitioned the behavior towards more ductile and energy-dissipating modes, characterized by more extensive crack patterns. Quantitatively, the ultimate punching load was increased by up to 5.47 times (achieving 75.53 kN), elastic stiffness by up to 2.24 times, and absorbed energy by a remarkable up to 10.49 times. Complementing the experimental program, a sophisticated finite element model is proposed to simulate the behavior of these strengthened connections. The numerical predictions show excellent correlation with the experimental results.

Abstract Reinforced concrete flat slab systems are attractive because of their architectural flexibility and reduced floor depth; however, they remain vulnerable to brittle punching shear failure. This paper investigates the structural performance of flat slabs strengthened with Reactive Powder Concrete (RPC) drop panels as a localized method for improving punching shear resistance. Six slab specimens (940×940×60 mm) were tested under monotonic concentric loading. The main variables were drop-panel thickness (15, 30, and 45 mm) and column dimensions (75×75 mm and 125×125 mm). The results showed that increasing the RPC drop-panel thickness from 15 mm to 45 mm substantially increased the ultimate load capacity. For the 75×75 mm column series, the capacity increased from 153 kN to 334 kN, while for the 125×125 mm column series, it increased from 180 kN to 278 kN. The reinforcement strain data and crack patterns further indicated that thicker RPC panels promoted a less brittle response than the thinnest panels. Overall, the findings demonstrate that RPC drop panels can significantly improve the punching performance of flat slabs.

Shear capacity design method for vertical joints in wind turbine concrete towers under combined bending-shear loads

Influence of Additional Reinforcement Length on the Punching Shear Capacity of Flat Slabs: Experimental Study and Code Comparison

This study presents an experimental and theoretical investigation on the shear behavior of a novel truss-type steel-reinforced recycled concrete short beam (TSRSB). Five TSRSB specimens with varying recycled coarse aggregate (RCA) replacement ratios (r = 0%, 50%, 100%) and shear span-to-depth ratios (λ = 0.76, 1.14, 1.52) were tested under concentrated loading to analyze their failure modes, load-displacement responses, and strain developments. The results indicate that reducing the shear span-to-depth ratio significantly enhances the shear capacity and initial stiffness; for instance, the ultimate load of the specimen with λ = 0.76 was 70.1% higher than that with λ = 1.52. In contrast, the RCA replacement ratio had a negligible impact on the ultimate load, with a maximum reduction of only 3.2%. A sophisticated finite element model was developed and validated against the experimental results, demonstrating high accuracy with a mean ratio of simulated-to-experimental ultimate load of 1.07. Based on the identified "truss-arch" mechanical model, a practical formula for predicting the shear capacity of TSRSB is proposed. This formula incorporates the influence of the RCA replacement ratio via a reduction factor (α = 20/(20 + r)) and superposes the contributions of the recycled concrete, stirrups, vertical and diagonal web members of the truss, and the steel flanges. Within the tested parameter ranges (r = 0 ~ 100%, λ = 0.52 ~ 1.14), the proposed formula shows good agreement with the experimental data, yielding a mean calculated-to-experimental shear capacity ratio of 1.00 with a coefficient of variation of 0.01. Therefore, the formula can provide a preliminary reference for the shear capacity calculation of specimens falling within these parameter ranges.

The performance and design of reinforced concrete, also known as slender beams are explained in the current study by a number of international codes. Slender beams are essential in modern construction because they preserve structural integrity while allowing for efficient material use. This research conducts a comprehensive comparative analysis of shear design provisions for slender reinforced concrete beams across major international standards, including ECP, ACI, Eurocode, CSA, BS, and JSCE. The innovation lies in systematically identifying differences and commonalities in methodologies related to shear capacity determination, minimum reinforcement requirements, and serviceability criteria. By addressing the current gap of exhaustive analyses needed to standardize criteria and resolve methodological discrepancies, the work aims to enhance the reliability, effectiveness, and uniformity of global shear design processes for slender beams. This comparative approach is intended to assist engineers and academics in making more informed design decisions, thereby improving the efficiency, structural integrity, and safety of slender beam applications in modern construction. In summary, the novel contribution is the exhaustive and systematic comparison of various international design codes concerning slender RC beam shear design. Identification of inconsistencies and variations that affect structural security and design efficiency. Providing insights that could aid in harmonization and standardization of shear design provisions worldwide. Offering recommendations towards achieving more consistent, safe, and economical slender beam designs in contemporary construction.

To explore the effect of the addition of steel plates as wall panels on the shear resistance of cold-formed thin-walled C-shaped steel (CFS) walls sheathed with the paper straw board on both sides (CFSPSB composite walls), one CFSPSB composite wall and three CFSPSB composite walls with built-in steel plate (CFSSPSB composite walls) were tested under monotonic horizontal loading. The failure form and failure process of specimens were obtained to analyse the shear capacity, lateral rigidity, and ductility of composite walls. The results show that when the steel plate is added to one side of the composite wall, the yield load is increased by 42.85%, and the lateral stiffness is increased by 20.15%. When the steel plate is added to the both sides of the composite wall, the yield load is increased by 94.34%, and the lateral stiffness is increased by 43.09%. Consequently, the addition of steel plates can significantly improve the shear bearing capacity and lateral stiffness of CFSSPSB composite walls. The ANSYS analysis results show that the width of the composite wall, stud space, and the self-tapping screw obviously influence the shear resistance of CFSSPSB composite walls, and a formula for shear capacity is proposed.

Abstract This study presents a nonlinear finite element assessment of the seismic vulnerability of Bridge B5593, located in the south‐western region of South Africa. Previous evaluations identified a high likelihood of column failure; however, these were based on linear material models incapable of capturing damage evolution. In this investigation, a high‐fidelity three‐dimensional solid‐element modeling framework is developed using the concrete damage plasticity (CDP) constitutive model to explicitly simulate tensile cracking, compressive crushing, stiffness degradation, and progressive failure in reinforced concrete columns. The model is verified against global structural properties and subjected to nonlinear time history analyses for peak ground accelerations ranging from 0.05 to 0.20 g. Results indicate that, while all columns possess sufficient shear capacity, flexural demand governs the response, with several columns exceeding their bending moment capacities by up to 82%. Importantly, tensile damage initiates at low seismic intensities (0.05 g) and propagates rapidly with increasing excitation, leading to significant stiffness degradation and localized failure, particularly in shorter columns. These findings highlight that material‐level damage progression provides critical insight beyond conventional force‐based assessments. The adopted modeling approach is intended as a local damage‐focused complement to conventional beam‐based global analyses, enabling detailed evaluation of failure mechanisms not captured by standard methods. Although simplifications such as fixed‐base conditions, idealized bearing behavior, and uniform ground motion were adopted, these do not affect the identification of critical vulnerabilities. The results demonstrate that Bridge B5593 is susceptible to moderate to severe damage at design‐level seismic events, with a significant risk of partial or global collapse at higher intensities. The study underscores the need for refined assessment approaches and potential retrofit strategies for existing bridges in regions of emerging seismic risk.

The pursuit of durable, ductile concrete has intensified because steel reinforcement suffers corrosion and durability problems. Glass fiber–reinforced polymer (GFRP) bars offer high strength-to-weight, corrosion resistance, and nonmagnetic properties, yet their low elastic modulus and sudden failure can result in large deflections, wide cracks and sudden collapse of GFRP reinforced concrete. This experimental study examined punching shear capacity and behaviour of two-way slabs reinforced with GFRP bars without shear reinforcement. It assessed whether hybrid reinforcement of GFRP bars in tensile zone and steel in compression zones of a flat slab improves punching shear capacity and failure mode relative to behaviour of GFRP or conventional steel-reinforced slabs only. A total of 26 full flat slab specimens with varied reinforcement ratios were cast and concentrically loaded representing interior columns of slab-column connection; parameters including load–deflection, first-crack load, crack patterns, ultimate capacity, punching shear resistance, and energy absorption were evaluated. Experimental failure loads or punching loads were compared with predicted failure loads using American, British and Canadian design codes as well as one proposed model existing in literature. The results revealed that American (ACI 318-19) code gave a better but conservative prediction of VExpr/VPred of 1.25 (experimental to predicted failure loads ratio) compared with the British (BS 8110) code, Canadian code and the model in literature all of which overestimated the punching capacity of the flat slabs. The study concludes that tensile reinforcement ratio and concrete strength have significant effect on punching capacity of the flat slab while compression reinforcement and hybrid reinforcement with conventional steel in compression zones have insignificant or unclear effect on punching shear capacity of the slab specimens. It is proposed that punching shear equation of ACI 318-19 design code be modified to include the contribution of tensile reinforcement to the punching shear capacity of flat slabs.

A novel boltless interlocking steel modular building system: Design, construction and mechanical performance

Design shear capacity of steel beams with compact flanges and slender corrugated webs