Shear Capacity Research Articles

Interpretable ensemble machine learning models for predicting the shear capacity of UHPC joints

Precast ultra-high-performance concrete (UHPC) structures (PUSs) have gained increasing research and application interest in civil engineering owing to the combination of advanced construction materials and methods. UHPC joints are critical parts of PUSs; thus, an accurate prediction of their shear capacity (SC) is essential to ensure structural safety and reliability. However, existing equations for predicting SC have limited accuracy and applicability owing to their simplified assumptions and restricted input parameters. To address these challenges, this study used machine learning (ML) approaches to develop a unified and accurate predictive model for various types of UHPC joints. A well-curated database containing 218 UHPC joints with diverse types and configurations was established. Six ensemble algorithms and four traditional algorithms were employed to develop predictive models, and eight existing equations were compared for performance evaluation. Both correlation-based and SHAP-based feature selection methods were used to optimize the model accuracy. The ensemble algorithms demonstrated better performance than the traditional individual algorithms, with the gradient boosting machine (GBM) model ranked as the best ML model for SC. The ML model outperformed existing equations in all evaluated metrics, demonstrating its accuracy and robustness. Furthermore, Shapley Additive exPlanations (SHAP) analysis was employed to interpret the ML model, thereby providing insights into influential features and their relationships. These findings demonstrate the advantages of ML methods in predicting the SC of UHPC joints and provide valuable guidance for the structural design and research on PUSs.

Empirical Punching Shear Capacity Equation for Reinforced Concrete Two-way Slabs with Openings

This study proposes a new equation to estimate the punching shear capacity of Two Way Reinforced Concrete Flat Slab Column (TRFSC) connections with openings. The TRFSC connections with openings in the literature were simulated using the finite element modeling technique. Then, the test results were used to calibrate and verify the finite element model. Next, the number of test data was artificially increased using the finite element model to cover a wide range of critical perimeters. Finally, the effects of several parameters such as the size of the openings in the reinforced concrete slabs, their position, and distance concerning the column on which the punching loading is applied on the variation of punching shear load capacity of TRFSC connections with openings were observed, the results showed that the proposed equation generally gave better results than the several current code equations. For the study used in the verification of the finite element model, it was observed that the ratios of the punching capacity values calculated using the experimental results and the regulations varied between 0.79 and 0.92 on average, and the regulations gave results that were not on the safe side for TRFSC connections with openings. However, with the nonlinear correction coefficient proposed in this study, the ratios of the experimental results and analytically calculated capacity values were calculated as 1.10 on average, and the standard deviation and variant values decreased much more.

Punching shear tests and design of UHTCC-enhanced RC slab–column joints with shear reinforcements

Reinforced concrete (RC) flat-slab structures may experience progressive collapse, usually caused by the punching shear failure of slab–column joints. Existing research has shown that the use of shear reinforcements or ultra-high toughness cementitious composites (UHTCCs) in slab–column joints is efficient in improving their punching shear performance. In this study, shear reinforcement was introduced into UHTCC-enhanced RC slab–column joints. Specimens of UHTCC-enhanced slab–column joints were tested considering the effect of shear reinforcements. The cracking development process, bearing capacity and ductility were analysed. Yield line theory and critical shear crack theory were adopted to predict flexural and punching shear capacities, respectively. Finally, the failure patterns of the specimens were distinguished by comparing the predicted punching shear and flexural capacities, taking ductility coefficients into account. The theoretical and test results show the effect of shear reinforcement on the behaviour of UHTCC-enhanced joints. Significant improvements in the bearing capacity and ductility of the joints was achieved by applying shear reinforcement. The failure pattern of the joint varied from premature punching shear failure to flexural-triggered punching shear failure with the application of UHTCC, and this transformation was more pronounced with shear reinforcement applied into the UHTCC-enhanced joint.

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.

A Review of Concrete Structure in Terms of Deterioration and Strengthening with Analysis of Recent Technology

In this paper the components of concrete structure, which are steel and concrete, and corrosion will be discussed. Followed by a description of the old technique that was used to strength and repair reinforced concrete structures. Then this essay presents a state-of-the-art technique that is fiber reinforced polymer and reviews of its manufacturing methods. Next, the positive and negative aspects of using fiber reinforced polymer sheets as increase shear and flexure capacity will be analyzed. Finally, a brief summary will be concluded.

Application of Organo-Modified Silica Nanoparticles to Improve the Load-Bearing Capacity of Bonded Joints of Dissimilar Steel Substrates

The paper deals with the joining of dissimilar steels by adhesive bonding. The base materials for the experimental work were deep-drawn low-carbon steel DC04, and hot-dip galvanized HSLA steel HX340LAD+Z. Adhesive bonding was performed using rubber-based and epoxy-based adhesives. The research aimed to verify the importance of surface preparation of steel substrates using a formulation with organically modified silica nanoparticles and epoxy organic functional groups, where one end of the functional group can be incorporated into the organic binder of the coating material and the other end can be firmly bonded to substances of an inorganic nature (metals). Since the binder base of adhesives is very similar to that of coatings, verifying the performance of this surface preparation when interacting with the adhesive is necessary. The load-bearing tensile shear capacity of single-lapped joints and the resistance of the joints against corrosion-induced disbanding in a climate chamber were tested. The energy dissipated by the joints up to fracture was calculated from the load-displacement curves. Bonded joints with organosilane were compared with joints without surface preparation and joints prepared by chroman-free zirconate passivation treatment. Exposure of the joints in the climatic chamber did not cause a relevant reduction in the characteristics of the joints. Organosilicate formulation was proved effective when bonding ungalvanized steels with a rubber-based structural adhesive, where it improves the bond quality between the adhesive and the substrate.

Restoring force model of phosphogypsum-filled cold-formed thin-walled square steel tube composite wall

The phosphogypsum (PG)-filled cold-formed thin-walled square steel tube (PFCFS) composite wall is a new type of cold-formed steel (CFS) wall. The restoring force model (including the skeleton curve and hysteresis rules) is an important performance of this type of walls. Based on the characteristics of load–displacement curves of the walls, a Pinching4 model for the skeleton curve of the walls is developed. The lateral stiffness and shear capacity of the walls are calculated by theoretical formulas, while other parameters are determined through data fitting. Moreover, the hysteresis rules of the walls adopt the Pivot model, and the Pivot parameters (α and β) of the walls are determined based on the principle of equal energy. Finally, based on the above restoring force model, the energy dissipation analysis for the walls with different parameters was conducted. The results show that improving the PG strength, stud thickness, or reducing the height-width ratio of the walls significantly enhances the energy dissipation capacity of the wall; increasing the OSB thickness, axial force ratio, or reducing the screw spacing gradually improves the energy dissipation capacity of the wall; the OSB configuration and the stud strength have a smaller impact on the energy dissipation of the wall; the energy dissipation capacity of the wall when the hold-down fails is lower.

Investigations on the shear performance degradation of ECC-NC grooved interface under salt freeze-thaw cycles

This study aims to clarify the mechanical behavior of engineered cementitious composite (ECC)-normal concrete (NC) grooved interface under salt freeze-thaw cycles. A comprehensive analysis was conducted to study the effects of the cycle number, interface agent, and ECC strength on the interface shear performance. The results showed that, compared with specimens in room temperature conditions, after 200 cycles, the shear strength and shear stiffness of all specimens decreased by no less than 37.8 % and 52.7 %, respectively. Moreover, using different interface agents or increasing ECC strength improved the interface salt freeze-thaw resistance significantly. Among all specimens using interface agents, fly ash had the best-enhancing effect on the interface shear performance. Additionally, considering interface area corrosion and degradation of material properties, a damage model was established. Based on the damage model, an equation for calculating the interface shear capacity was proposed, providing a valuable reference for the engineering application of ECC reinforcement in extreme environments.

A new approach to calculate the shear strength of high-performance reinforced concrete beams fibered with micro polypropylene (experimental and analytical study)

Micro polypropylene (PP) fibers are commonly utilized to increase concrete's durability and fire resistance in building projects. High-Performance-Fiber-Concrete (HPFC) has become increasingly popular in the sustainable buildings industry in the past two decades. Some important structures were constructed using HPFC with micro polypropylene fibers to limit corrosion and increase fire resistance. This paper presents an experimental and analytical investigation to study the effect of micro PP fibers on the shear strength of HPFC beams with and without stirrups. The experimental results were used to obtain a new and simple approach that can calculate the shear strength of HPFC beams without needing for experimental findings. Also, the effect of PP fibers was compared with that of using steel (ST) fibers only or the hybridization of both PP and ST fibers. Twelve simply supported beams were fabricated and loaded with a concentrated load up to failure and all the required data were obtained and examined. The results indicated that adding PP fibers was effective in increasing both the shear capacity and the toughness of HPFC beams, either with or without stirrups, especially for beams with 1 % PP fibers. For beams without stirrups either with or without PP fibers, the mode of failure was diagonal tension shear failure. The presence of stirrups and / or ST fibers changed the failure mode from diagonal tension shear failure to compression shear failure. Analytically, a new approach of ten equations, was proposed based on the angle of compression struts and the splitting tensile concrete strength, to calculate the shear strength of HPFC beams. The equations of the proposed approach were compared with the results of forty five experimental specimens from four different research studies to examine their validity. The results were in a very good agreement and accuracy with the experimental results.

Exploring engineering properties of sustainable multi‐grade concrete: Materials, structural, and environmental aspects

AbstractThrough experimental and theoretical studies, this research explores the materials, structural, and environmental aspects of multi‐grade concrete (MGC), a potentially sustainable structural concrete. The experimental part investigates the compressive, split cylinder, flexural, and shear strengths of MGC, essential parameters for the design of structural members composed of MGC. It also provides the relationships between various strengths. The compressive behavior is correlated with the cracking pattern and the confinement effect caused by the end platens. The theoretical study involves determining the carbon emissions (CEs) and modifying ASTM/ACI expressions for the flexural tensile strength (FTS) and shear capacity applicable to MGC. Three uni‐grade concretes (UGCs) with distinct materials, properties, and grades: grade 17 (G17), grade 25 (G25), and grade 30 (G30), were poured in layers of varied thicknesses to make two variants of MGC. Experimental investigations showed that the higher‐strength concrete (HSC) confined the lower‐strength concrete (LSC) part thus increasing the compressive strength. Replacing 50% of LSC with HSC led to an increase in compressive and shear strengths by 21% and 40%, respectively. The shear strength values of reinforced MGC beams observed experimentally are aligned with those obtained through the modified expressions developed by the authors. A trade‐off analysis among the strengths, CEs, and costs of UGC and MGC can aid in selecting MGC customized to specific requirements, thereby contributing to the development of sustainable structural concrete.

Shear strengthening of reinforced concrete beams completely wrapped by large rupture strain (LRS) FRP

An experimental work on the shear strengthening of reinforced concrete (RC) beams completely wrapped by large rupture strain (LRS) FRP is presented in this paper. A total of 14 three-point bending tests were carried out on simply supported RC beams, with a focus on the impacts of the shear span-to-depth ratio (1.53, 2.25, and 3.01) and FRP reinforcement ratio (0.37 %, 0.75 %, and 1.12 %) on the shear behavior of RC beams strengthened with LRS FRP. For the beams with a median length, the ductility coefficients increased by 81 %, 154 %, and 335 % with the increase in FRP reinforcement ratio. For the long beams, the ductility coefficients increased by 116 %, 286 %, and 470 % as the FRP reinforcement ratio improved. The ductility markedly improved with the increase in shear span-to-depth ratio. PET FRP’s fracture was not found at the ultimate state, and the improvement in mid-span deflection after the peak state was mainly contributed by the shear deformation. The strengthened specimens exhibited a ductile shear failure mode. For the short RC beams, the shear capacity was slightly enhanced, and the ductility was not improved after being strengthened. The strengthened short RC beams still showed a brittle diagonal compression failure mode. The experimental shear contribution of PETT FRP was compared with the prediction of the existing design guidelines. Finally, an effective strain model of PET FRP, including the shear span-to-depth ratio effect, was proposed and verified with the experimental results.

Shear Performance and Damage Characterization of Prefabricated Basalt Fiber Reactive Powder Concrete Capping Beam Formwork Structure

Basalt Fiber Reactive Powder Concrete (BFRPC) semi-prefabricated composite capping beam structures can effectively improve the shortcomings of ordinary concrete capping beams' construction difficulties and insufficient bearing capacity. In this study, with the objective of analyzing the shear damage and damage characteristics of a prefabricated BFRPC capping beam formwork, structural damage tests under different levels of loading were carried out to obtain the mechanical parameters of key nodes. Acoustic emission (AE) and Digital Image Correlation (DIC) techniques were used to acoustically and visually characterize the formwork damage. The research results showed that the damage stage of the capping beam formwork was divided, and an early damage warning method was proposed based on the acoustic parameters. Using the DIC technique to identify the crack width evolution pattern during the shear process, it was found that the cracks expanded steadily as the load increased. Combining the experimental and simulation results as well as the Subdivision Superposition Theory, a half-open stirrup strength discount factor β was introduced and suggested to take a value of 0.79. The formula for calculating the shear capacity of BFRPC capping beam formwork is proposed to provide a theoretical basis for its application in prefabricated assembled structures.

Shear strengthening of RC beams with prestressed NSM CFRP: Influencing factors and analytical model

This study proposes the application of prestressed near-surface-mounted (NSM) carbon-fiber-reinforced polymer (CFRP) technique in the field of the shear-strengthening of bridges for the first time. Fourteen reinforced concrete (RC) beams shear strengthened with prestressed NSM CFRP were tested under static load. The effect of the CFRP prestressing level, spacing, angle, and end-anchorage measures on the shear-strengthening behavior was evaluated. The experimental results demonstrate that the ultimate shear capacity of prestressed NSM CFRP shear-strengthened beams increased by 65–127% when compared to that of the reference beams, and the width of shear cracks was effectively suppressed. The failure mode of prestressed NSM CFRP shear-strengthened beams without end-anchorage measures was web concrete cover separation, which can be suppressed using a CFRP U-jacket and through-beam screw. Increasing the CFRP prestressing level and percentage enhanced the ultimate shear capacity and cracking resistance of the strengthened beams. However, an excessively high CFRP percentage and prestress level combination resulted in large shear crack angles and decreased the shear contribution of CFRP and concrete. Finally, an analytical model based on the modified compression field theory (MCFT) was proposed to predict the flexural-shear load response of strengthened beams, which was in agreement with the experimental results.

One-way shear strength design of flat-plate voided slabs

Current design standards do not include design provisions to handle the reduced shear capacity of voided flat-plates, and the current design practice considers its shear capacity as a percentage of the solid slab. The study presents an investigation of the one-way shear capacity of flat-plate voided slabs. The investigation is carried out using a compiled evaluation experimental database and an experimental program. A capacity reduction factor for flat-plate voided slabs, λvoid, is proposed and is a function of void height to the slab height (hvoid/h) ratio. The proposed factor is calibrated to the ACI 318-19 shear model. The proposed factor allows for section optimization based on shear capacity, where the height of the void former can be selected based on the shear load subjected to and the required shear strength. This is not possible using the current practice of the manufacturers, where they use either a constant capacity reduction factor or a factor that is slightly affected by the hvoid/h ratio. The model is applicable for voided slabs with a void former clear spacing of 0.10–0.16 of its diameter, or higher. Incorporating the reduction factor, λvoid, resulted in an average experimental-to-predicted (Vexp/Vpred) of 1.67 and COV of 16 %. By comparing the average Vexp/Vpred and COV of voided slabs to solid slabs, the strength reduction factor (ϕ) of 0.75 for shear will still be applicable.

Lateral Performance Analysis of Trapezoidal Orthogonal Stiffened Steel Plate Shear Walls

This paper introduces a trapezoidal orthogonal stiffener steel plate shear wall (TSW). The finite element model of the TSW was developed following the validation of low-cycle repeated tests conducted on a single-span double-layer steel plate shear wall. The paper studies the effects of the flat steel plate thickness, stiffener thickness, stiffener height, and stiffener bottom width on the seismic performance of TSW. Building upon these findings, a theoretical formula for the ultimate shear capacity of TSW was developed. The results prove the following: (1) By changing the flat steel plate thickness, the stiffener thickness, and the stiffener height, the seismic behavior of TSW can be enhanced. It is suggested that the flat steel plate thickness is 4~6 mm, the stiffener thickness is 4~6 mm, and the stiffener height is not more than 60 mm, while the effect of the stiffener bottom width on the seismic behavior of TSW can be neglected. (2) The maximum error is 22.16%, compared to the theoretical value of TSW ultimate shear capacity with the finite element simulation value. However, as the finite element results surpass the test results, it indicates that the formula-derived results are unsafe, necessitating a recommendation for correction.

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

Ultimate Shear Capacity of the Cold-Formed Steel Torsionally Restrained Beam-to-Column Moment Connection with a Three-Bolted Clip Angle and Flange Cleat

Ultimate Shear Capacity of the Cold-Formed Steel Torsionally Restrained Beam-to-Column Moment Connection with a Three-Bolted Clip Angle and Flange Cleat

Experimental and numerical investigation of punching and post-punching shear capacities of post-tensioned flat plate slab-column joints influenced by prestressing levels

Post-tensioned slab systems serve as an effective method to enhance the progressive collapse resistance of concrete flat plate structures by significantly improving the punching shear and post-punching capacities of their slab-column joints. While the existing research mainly focused on the punching shear behaviour of post-tensioned slab-column joints in small deformation stages, the post-punching behaviour in large deformations has been overlooked. This study aims to fill this research gap thorough experimental and numerical studies. Experimentally, four slab-column joints, including three post-tensioned specimens (with varied prestressing levels) and one specimen without tendons, were designed and tested. Detailed failure process and load-resisting mechanisms of the specimens at different deformation stages were discussed. The test results confirmed the efficiency of post-tensioning in improving the punching shear performance. Varying prestressing levels have influenced the development of punching shear capacity but did not affect the growth rate of load resistance in the initial post-punching stage. Numerically, validated finite element models were used to predict the post-punching capacities of the specimens. The numerical results indicated that post-tensioning helped increase post-punching capacities, but such an enhancement was independent of the prestressing levels. Additionally, the influence of the rupture strains of both tendons and reinforcement on the post-punching capacity was investigated through a parametric study.

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.

Shear Capacity of Ferrocement Plates

Shear Capacity of Ferrocement Plates