Calculation Of Shear Strength Research Articles

Contribution to the design of prestressed hollow core purlins without transverse reinforcement

AbstractThe hollow core purlin is a structural element resulting from the sectioning of hollow core slabs into two ribs. This component can be classified as a prestressed hollow core beam without transverse reinforcement. Although this solution offers potential for increasing the productivity of precast concrete element factories, it currently lacks normative guidelines due to the high risk of shear failure. The aim of this study is to highlight an equation to underpin the design of hollow core purlins based on experimental verification. To achieve this objective, six samples of hollow core purlins were analyzed. Initially, the manufacturing characteristics and cross‐sectional geometry of each piece were observed to gather data on the production process. Subsequently, positive bending tests were conducted to characterize stiffness and determine the effective mean tensile strength. Later, shear strength tests were performed to identify the failure mechanisms of the elements. In parallel, the prestressing forces, stiffness, tensile strength, cracking moment, calculated shear strength using the flexural‐shear mechanism, and verification of shear strength due to diagonal tension were computed based on concrete compressive strength values and data provided by the manufacturer. Finally, the experimental values obtained were compared with the theoretical calculated values to establish a correlation that highlights the calculation procedure that best represents the behavior of the studied elements.

Interfacial shear behavior of salt freeze-thaw pre-damaged NC with ECC: Experimental and theoretical investigations

This study aims to clarify the interfacial shear behavior of salt freeze-thaw pre-damaged normal concrete (NC) with engineered cementitious composite (ECC). A comprehensive analysis was conducted to study the effects of the cycle number, interfacial roughness, and ECC curing age on the interfacial shear performance. The results showed that, as the cycle number increased, the interfacial shear strength decreased to varying degrees. The optimal interfacial roughness was 5.5mm, and further increasing roughness would decrease the interfacial shear stiffness. When the ECC curing age was 7 days, it had already reached 85% of the interfacial shear strength of specimens cured for 28 days. Additionally, considering the effects of cycle number and interfacial roughness, an interfacial shear strength calculation model and a shear-slip curve prediction model were established, providing a valuable reference for the engineering application of ECC repair for salt freeze-thaw damaged NC.

Shear Performance in Reinforced Concrete Beams with Partial Aggregate Substitution Using Waste Glass: A Comparative Analysis via Digital Imaging Processing and a Theoretical Approach.

The usage of waste glass aggregate (WGA) associated with the replacement of fine aggregate (FA) and coarse aggregate (CA) is observed to reduce the number of raw materials for sustainable concrete. For this aim, a total of 15 beams were produced, and then investigational experiments were implemented to observe the shear performances. The stirrup spacing and WGA proportion were chosen as the main parameters. FA and CA were exchanged with WGA with weight proportions of 0, 10, and 20%. The experimental investigation results showed that changing stirrup spacing and WGA proportion affected the fracture and shear properties of reinforced-concrete-beams (R-C-Bs). Furthermore, the findings of the test results revealed that the proportion of WGA could be efficiently consumed as 20% of the partial replacement of FA. With the addition of FA to the mixture, the load carrying capacity of R-C-Bs increases. On the other hand, increasing the WGA ratio by more than 10% using CA, together with increasing the stirrup spacing, can significantly reduce the capacity of R-C-Bs. It was observed that the calculated shear strengths of R-C-Bs with inadequate stirrup spacing, based on ACI 318 and EC2 design codes, can be up to 52 and 79% higher than the experimental results for R-C-Bs containing coarse glass aggregate and 21 and 56% higher for R-C-Bs containing fine glass aggregate, respectively. Additionally, an image processing method was applied to describe the damages/microdamages in R-C-Bs. At that point, the findings obtained from the experimental part of the study were confirmed by the results of the image processing method. Although the strains obtained with the image processing method are reliable, it has not been determined exactly where the crack will occur due to the very sudden development of the shear crack at the moment of beam failure.

Punching and lateral cyclic behavior of concrete slab-column connections reinforced with steel sheets

During an earthquake, slab-column structures with high gravity-shear ratios often experience increased local shear stress and deformation in the connection area, leading to reduced unbalanced moment capacity and drift capacity of the connections. This study aims to create a new and more efficient method of enhancing the unbalanced moment capacity and deformation capacity of reinforced concrete slab-column structures through using steel sheets as punching reinforcement. Tests were conducted to evaluate the effects of the thickness, extension length, and layout of this new type of punching reinforcement on the unbalanced moment capacity and deformation capacity of the connections when subjected to vertical and horizontal cyclic loads. The results indicated that as the steel sheet thickness increased, the unbalanced moment capacity of SC-2 and SC-3 rose by 24 % and 48 % respectively, while the drift capacity improved by 20 % and 40 % compared to SC-1. Furthermore, the failure mode shifted from stress-induced punching to drift-induced punching. Compared to SC-1, a cruciform layout with an additional diagonal arrangement of sheets increased the unbalanced moment capacity and drift capacity by approximately 17 % and 20 %, respectively. The extension length of the sheets reduced from 600 to 420 had negligible effect on the unbalanced moment capacity and deformation capacity. Utilizing experimental data, this study compared the relationship between the drift capacity and gravity shear ratio of connections reinforced with different shear reinforcements. The underlying causes for the observed lower drift capacity of the specimens are analyzed, and design recommendations for optimizing the steel sheets are subsequently proffered. After thoroughly analyzing the experimental results, a simplified calculation methodology for assessing the shear strength of steel sheets was developed, taking inspiration from the shear strength calculation approach outlined in ACI 318–19. The efficacy of this simplified approach was subsequently validated by comparing the experimental results with those predicted by current design codes. Furthermore, by comparing the experimental results with the predicted values, the relationship between the punching failure mode of connections and their punching strength was discussed.

Analytical calculation of the in-plane shear strength of fibre-reinforced concrete

Existing code prescriptions for determining the shear strength of fibre-reinforced concrete (FRC) elements are either empirical or rely on important assumptions that require further clarification. A mechanically based method is here proposed to determine the fibres and the shear reinforcement contributions to the in-plane shear strength of membrane elements. The method is derived from the comprehensive Cracked Membrane Model for FRC to determine in-plane shear strength of FRC panels and is suitably adapted to determine the shear strength of beam elements. The proposed methodology is compared to existing code formulations and validated against experimental results from 14 panels subjected to in-plane shear stresses and from 34 beams failing in shear. The average ratio between experimental and calculated shear strength is 1.00 for the panels and 1.11 for the beams, with coefficients of variation 11 % and 24 %, respectively. The proposed analytical methodology enables the determination of shear strength and failure modes in FRC elements, with or without shear reinforcement. Equations providing the fibre contribution and the compression field inclination are derived from mechanical considerations, emphasizing the key influencing variables. The proposed method can serve as a basis for code-like formulations for shear strength linked to the involved mechanics, but for which further levels of simplification are still required.

Mechanical properties of steel fiber reinforced recycled concrete under compression-shear stress state

The continuous urbanization of construction has led to an increasing demand for concrete, resulting in large-scale gravel and river sand mining, which seriously affect the sustainable development of the environment. The waste concrete produced by the demolition of old buildings is processed into recycled aggregate to replace natural aggregate, and then the preparation of recycled concrete can effectively alleviate this problem. This paper investigates the mechanical properties of steel fiber reinforced recycled concrete (SFRRAC) under compression shear conditions, a compression shear test with 99 cubic specimens was designed, with the variation parameters being recycled aggregate concrete replacement rate, compressive stress, and steel fiber content. The failure mode of SFRRAC under compression-shear stress was observed, and the shear force-displacement curve was calculated. Furthermore, a thorough examination was performed to assess the mechanical characteristics of SFRRAC specimens under compression-shear stress. The findings of this study suggest that as the compressive stress increases, the failure characteristics of the specimens shift from exhibiting brittle failure to displaying ductile failure. The shear strength is most sensitive to the change in compressive stress. When the compressive stress reaches 6 MPa, the shear strength can reach 3.41 times that of the direct shear specimen. The shear strength of SFRRAC specimens is composed of the bond strength of concrete, shear expansion strength, and friction shear strength. The incorporation of steel fibers can modify the distribution of shear strength among the individual components. The adverse effect of the recycled aggregate replacement rate on the toughness index of the specimen is mainly concentrated after the peak point. Nevertheless, an elevation in compressive stress and the inclusion of steel fibers can counterbalance this detrimental influence. The shear strength calculation formula of SFRRAC in shear state is put forward, which has a reference value. This study provides an experimental reference and a theoretical basis for further examination of SFRRAC.

Shear Strength of Ultra-High-Performance Concrete Beams without Stirrups—A Review Based on a Database

This paper presents a comprehensive study on ultra-high-performance concrete (UHPC) beams without stirrups, where the test data of 487 beams were collected, and an experimental database was established. Four distinct shear strength calculation models for UHPC beams were examined in the study. These models were created from national specification guides. The results indicate that while the code equation is useful for predicting UHPC beam shear capacity, it consistently underestimates actual values, with a mean experimental-to-calculated ratio above 1.5. The database was also used to study the impacts of the compressive strength of UHPC, the shear span-to-depth ratio, the fiber volume fraction, and the reinforcement ratio on the shear strength of UHPC beams. The findings showed that the shear span-to-depth ratio significantly affected the shear load-bearing capacity of UHPC beams. The increase in the compressive strength of UHPC, fiber volume fraction, and reinforcement ratio positively affected the shear strength of UHPC beams to varying degrees. Additionally, there were size effects for beams with a shear span-to-depth ratio of less than 1.5 and an effective depth of more than 300. In addition, coefficients accounting for fiber influence and the shear span-to-depth ratio were incorporated to develop an enhanced formula for UHPC beams. The empirical data from the database tests revealed that the average ratio of the beams’ experimental shear capacity to the values predicted by the modified equation is 1.3, with a standard deviation of 0.74. These results suggest that the refined equation offers improved calculation precision and broader applicability. Eventually, a summary of the issues pertaining to the shear performance of UHPC beams and the key future research directions is provided to facilitate a clearer comprehension and awareness of emerging concepts for scholars within the discipline.

Limits for the Punching Shear Capacity of the Flat Slabs Reinforced with Transverse Reinforcement

One of the most effective and common ways of an increasing the punching shear capacity of the flat slabs is using of shear reinforcement. An important limit during the design is the determination of the maximum punching shear resistance. The fact that the calculation of such an important value is still clearly empirical has met with criticism from many experts in recent years. Consequently, a new design model for the calculation of the maximum punching shear resistance, based on the critical shear crack theory was developed. The second generation of the Eurocode 2 (prEC2) introduces a more accurate and sophisticated design model for the determination of the upper limit of the punching shear capacity and considers several parameters. The main aim of this paper is to describe the new methodology of calculation of the maximum punching shear strength and the parameters that could influence it. The paper deals also with an assessment of the suitability of new model by comparing it with experimental results, that have been selected from a database of specimens that failed by punching at the level of VR,max.

Effect of Drying–Wetting Cycle and Vibration on Strength Properties of Granite Residual Soil

Granite residual soil (GRS) exhibits favorable engineering properties in its natural state. However, a hot and rainy climate, combined with vibrations generated during mechanical construction, can cause a notable decrease in its strength. In this study, the evolution of stress–strain curves and strength parameters (cohesion c and internal friction angle φ), unconfined compression strength (UCS) under drying and wetting(DW) cycles and vibration were investigated by means of direct shear test and UCS test. Furthermore, modified formulas for calculating shear strength and UCS under DW cycles and vibration were proposed, and their accuracy was verified. The results are as follows: The stress–strain curve of shear strength exhibits strain-hardening characteristics, and the shear compressibility of the sample increases with the number of DW cycles and vibration time. However, the stress–strain curve of UCS shows strain-softening properties, and the peak strength shifts forward with the number of DW cycles and vibrations. With the increase in the number of DW cycles and the vibration time, c shows a non-linear degradation, with a maximum degradation of 58.6%. φ fluctuates and increases due to the densification effect of DW cycles, but the influence of vibration on φ decreases with the increase in the number of DW cycles. UCS rapidly decreases and gradually stabilizes after DW cycles and vibration, with a maximum degradation of 81.1%. This study can serve as a reference for the stability analysis of GRS pits subjected to long-term influences of hot and rainy climates and mechanical vibration, providing valuable insights for future research.

Data-driven prediction method for shear capacity of corroded rectangular reinforced concrete shear walls under varied failure modes

The physical and mechanical properties of rectangular reinforced concrete shear walls (RRCSW) will deteriorate over time due to acidic erosion, causing changes in damage characteristics and a reduction in shear capacity under seismic loading. The aim of this paper is to develop a failure mode-based prediction method for the shear capacity of corroded RRCSW, as the existing formulas for calculating shear strength become invalid in such scenarios. Initially, a total of 2403 RRCSW samples with various corrosion levels and main design parameters were generated and simulated using the authors' previous numerical method to obtain a comprehensive database of shear capacity. Subsequently, an efficient damage mode identification method for RRCSW was established using the Random Forest algorithm, and its accuracy and applicability in identifying damage modes of corroded RRCSW were verified. Finally, the existing calculation formulas for RRCSW in flexure-shear and shear failure modes were selected and modified to consider the corrosion effect based on the shear capacity database. The comparative analysis revealed that the proposed formulas provide accurate predictions of the shear capacity of corroded RRCSW, making the results of this study invaluable for seismic design of new structures and seismic performance evaluation of existing structures.

Evaluation of seismic performance of reinforced concrete columns retrofitted with steel links

The replaceable steel link (RSL) system enhances seismic performance by addressing early brace buckling found in conventional brace systems. This innovative system features a sliding slot, allowing for lateral steel link movement in response to column displacements, which effectively delays buckling. This study builds upon previous research introducing the RSL system and delves into the previously unexplored effect of the sliding slot length on the system's dynamic behavior. Experimental results showed that shorter sliding slots delayed the onset of shear cracks and concrete spalling, particularly when subjected to eccentric lateral loads. Retrofitted specimens exhibited a load capacity 1.5 times greater than their non-retrofitted specimen, irrespective of the slot length. The difference between the experimental and calculated shear strengths was a mere 4%, with a deviation from the FEMA 356 design criteria of approximately 12%. Therefore, the viability of using existing design criteria to predict the hysteretic behavior of retrofitted columns with the RSL system has been confirmed.

Shear mechanism and strength calculation of steel shear keyed dry joints in precast segmental bridges

Precast concrete segmental bridges (PCSBs) are prone to weakness at the joints. To ensure accurate positioning and effective force transmission between segments, steel shear keyed joints were designed in the present study. A comprehensive investigation was also conducted into the shear performance of such joints, drawing on existing experimental research and theoretical analysis, so as to facilitate more comprehensive understanding of the shear mechanism and calculation methods involved. The results reveal that the steel shear keyed joint effectively transmitted shear force through the contact pressure between the steel key and concrete, aided by confining pressure. The steel keyed joint was also found to possess high shear capacity and exhibit good ductility. A mechanical model of the steel shear keyed joint was constructed, and the shear mechanism and failure modes were revealed, including shear failure of the steel key, local compression failure of concrete, and tearing failure of concrete. Finally, the present authors suggest that the shear failure of the steel key should be used as the basis for the shear resistance design of steel shear keyed joints, which can be calculated according to the formula ( The strength of concrete around the steel key should also be checked.

Design oriented shear strength prediction model of UHPFRC beams

The application of Ultra-high performance fiber reinforced concrete (UHPFRC) to beams can effectively improve their strength and ductility properties. At present, there are more shear test studies on UHPFRC beams, but few theoretical studies on their strength calculation method. The fibers in UHPFRC can inhance the strength of the beams, and how to quantify the fibers’ contribution to the total strength is a research difficulty. Firstly, the shear strength database including 197 UHPFRC beam specimens is created. The key characteristics determining the shear strength, namely fiber volume fraction, stirrup configuration, and shear-span ratio, are determined by evaluating the test results. Then, considering the effects of the factors above, a truss-arch model is developed. The arch shear strength is determined by utilizing the shear deformation coordination of the arch compression structs and truss compression structs. Superimposing the shear strengths of the arch and truss models yields the shear strength of UHPFRC beams. Finally, the accuracy and reliability of the proposed method are assessed using the test database and compared to existing shear strength calculations. The study findings demonstrate that the mean value of the calculated to observed shear strength ratios produced by the suggested technique is 1.10, with a coefficient of variation of 0.28, indicating that the proposed method has superior calculation accuracy and reliability than existing methods.

Numerical simulation analysis of load-bearing capacity at joints of symmetrical cantilever-assembled bridges based on the logistic regression model

Abstract Bridge joint bearing capacity analysis is difficult to fit the requirements of the era of big data. The traditional way of bridge-bearing capacity numerical analysis exists in the wave of digital development of big data information, the Internet of Things, and artificial intelligence technology like a wild development. The traditional way of under the problem: is efficiency, engineering analysis is not accurate, data information paper, work responsibility is not in place, technical equipment, etc. This paper revolves around the numerical simulation analysis of the load-bearing capacity at the joints of symmetrical cantilever-assembled bridges based on the logistic regression model by finding literature to understand the concept and algorithm of the logistic regression model, construct logistic regression model based on dichotomous dependent variable logistic regression algorithm, logistic regression model parameter estimation, logistic regression. The three aspects of the model evaluation index are studied. The numerical simulation analysis of the load-bearing capacity at the symmetrical cantilever joint based on the logistic regression model, the shear strength calculation at the bridge joint, and the bridge longitudinal bar slip deformation are calculated, respectively, and then the actual value of the bridge load bearing capacity is derived. Simulation in the bridge bearing capacity at 0kN, 5kN, 10kN, 15kN, 20kN, 25kN, and 30kN, the model algorithm evaluation index under the three indicators of prediction rate, accuracy, deviation of the verification analysis. The results show that the prediction rate of the logistic regression model algorithm based on the load carrying capacity up to 30kN is 84%, the accuracy rate is 94%, and the deviation is 11%, and the three index values have better performance compared with the one-dimensional linear regression model algorithm and the multiple linear regression model algorithms. This study is beneficial to extend the bridge structural analysis function and make the bridge load capacity assessment more automatic; it can facilitate the comparison of historical data of bridge tests, longitudinal change of indicators at different testing time points, and grasp the current situation and change trend of bridges. Thus it is of great historical significance to the development of the Chinese bridge infrastructure industry.

Seismic performance of concrete-encased hexagonal CFST column base: Design method

This paper presents the parametric analysis and design method for the concrete-encased hexagonal concrete-filled steel tubular (CFST) column base under combined compression and biaxial bending. The corresponding experimental and numerical investigations on the seismic performance of the concrete-encased hexagonal CFST column base under combined compression and biaxial bending have been presented in the companion paper (Yang et al., 2023). The finite element model established in the companion paper is used to study the influence of key parameters on the load bearing capacity and the distribution of internal force. These parameters include those of the CFST column, the outer RC, the plate-anchor component, the axial load ratio and shear connectors. A total of six failure modes are identified, including three types of flexural failure and three types of shear failure. The ultimate capacity and ductility of the column base with flexural failure at the bottom or top of the plate are higher than that of other four failure modes, which are determined as the reasonable failure modes for practical application in the design and analysis of concrete-encased column bases. A novel design approach for the concrete-encased CFST column base is introduced. A simplified method is proposed to predict the flexural resistance of the concrete-encased CFST column base, following up with the shear strength calculation of outer RC to determine the stirrup arrangement. Some constructional recommendations are also proposed.

Effects of aspect ratios and strengthening methods on seismic behavior of masonry piers strengthened by using hybrid-fibers modified reactive powder concrete

Piers are the main load-bearing elements of masonry structures. Damage to piers in earthquakes will lead to the collapse of the whole structure, so piers need to be strengthened. In order to study the effectiveness of hybrid-fibers modified reactive powder concrete (HFMRPC) coating strengthening on masonry piers and the influence of different strengthening methods and aspect ratios on the seismic behavior of masonry structures, six masonry walls with different aspect ratios (0.8, 1.0, and 1.4) and strengthened by different methods (unreinforced, single-sided coverage in piers, double-sided coverage in piers, and double-sided cross-bracing) were tested under in-plane quasi-static loading. The test and analysis results showed that the seismic behavior of masonry walls in terms of bearing capacity, displacement ductility, stiffness, and energy dissipation was effectively enhanced by HFMRPC coating. The improvement range of ductility coefficient, initial stiffness, and cumulative energy dissipation were 86.3% ∼ 229.3%, 18.2% ∼ 104.0%, and 57.0% ∼ 139.7%, respectively. The most suitable strengthening method for strengthening piers was double-sided cross-bracing compared with other methods. The strengthening effect of the double-sided coverage in piers was improved with the increased aspect ratio. Additionally, masonry wall shear strength and flexural capacity calculation methods were proposed based on GB 50003-2011, N-M interaction diagrams, and equivalent rectangular stress block.

Evaluating the Influence of Sand Particle Morphology on Shear Strength: A Comparison of Experimental and Machine Learning Approaches

Particulate materials, such as sandy soil, are everywhere in nature and form the basis for many engineering applications. The aim of this research is to investigate the particle shape, size, and gradation of sandy soil and how they relate to shear strength, which is an essential characteristic that impacts soil stability and mechanical behaviour. This will be achieved by employing a combination of experimental methodology, which includes the use of a microscope direct shear apparatus, and machine learning techniques, namely multiple linear regression and random forest regression. The experimental findings reveal that angular-shaped sand particles enhance the shear strength characteristics compared to spherical, rounded ones. Similarly, coarser sand particles improve these characteristics compared to finer sand particles, as do well-graded particles when compared to poorly graded ones. The machine learning findings show the validity of both models in predicting shear strength when compared to the experimental results, showing high accuracy. The models are designed to predict shear strength of sand considering six input features: mean particle size, uniformity coefficient, curvature coefficient, dry density, normal stress, and particle regularity. The most important features from both models were identified. In addition, an empirical equation for calculating shear strength was developed through multiple linear regression analysis using the six features.

Strength prediction methods in shear bond behaviour of composite slabs

Composite deck slabs are gaining wide acceptance in many countries as they promote faster, lighter and economical construction in buildings. The shear behaviour of composite deck slab is a complex phenomenon. Strength of composite deck slabs can be analyzed by different methods for restrained and unrestrained conditions. In this work various methods for determining the shear bond capacity of composite deck slab are studied by modelling composite deck slab for various shear spans in finite element analysis software. The main objective is to understand the deflection as well as slip characteristics of composite deck slab and to apply these values for calculating shear strength using different methods of the composite deck slab. A comparison between methods are also done to find out the best possible prediction method. It is found that Partial Shear Connection (PSC) method performs better than that of other methods considered.

Experimental and Numerical Investigation of Integrated Steel Shear Walls with Varying Web Width-to-Thickness Ratios

The cold-formed steel-framed shear wall sheathed with steel sheet is widely used as a lateral force-resisting system for light-framed construction. However, the boundary conditions of the screw joint are not clear when steel is screwed to the frame. To address this issue, experimental methods have been used to calculate shear strength, but these methods have many limiting factors. In this study, we investigate the structural performance of integrated steel shear walls with varying web width-to-thickness ratios as an alternative to steel-sheathed shear walls used in light-gauge steel frames. The proposed design equation for cold-formed steel integrated shear walls is validated by three specimens and 72 finite element models. This equation allows designers to determine the strength of integrated steel shear walls without conducting full-scale shear-wall tests.

Improved Design Shear Method for the Bolted Cold-Formed Steel Clip-Angle Connector

In this paper, the ultimate shear capacity of the 3-bolt cold-formed steel clip-angle between the cold-formed steel (CFS) beam and column is evaluated through 54 laboratory tests. A series of experiments were conducted by varying (1) thickness, and (2) aspect ratio (L/D) of clip-angles for different depths (D) and widths (A). The experimental program consists of three phases of tests: (1) Phase-I: direct shear load tests on clip-angle attached to a CFS column through 4.6-grade bolts; (2) Phase-II: CFS column replaced with a hot-rolled steel (HRS) column, since the CFS column experienced bearing failure in Phase-I; and (3) Phase-III: 10.9-grade bolts used instead of 4.6, as the 4.6-grade bolts subjected to bolt shear failure in Phase-II. Failure modes observed in the test specimens are (1) shear local buckling of clip-angle; (2) column bearing failure; (3) bolt shear failure; and (4) tear failure in clip-angle. Design shear equations from the literature, for the bolted clip-angle, were found to be inefficient for the high-grade steel (fy=375 MPa to 550 MPa), and conservative for the commonly available low-grade steel (fy=275 MPa). Hence a new shear strength equation is suggested for the clip-angle from the collated data of the present study and past research work. A comparative study between 2-bolt and 3-bolt clip-angle configurations was conducted to evaluate the increase in shear strength. Reliability studies were conducted, and corresponding resistance and safety factors were suggested for the design shear strength calculation corresponding to load and resistance factor design (LRFD), limit state design (LSD), and allowable strength design (ASD) methods.