Longitudinal Reinforcement Ratio Research Articles

Tensile characteristics of ultra-high-performance fibre-reinforced concrete with and without longitudinal steel rebars

Ultra-high-performance fibre-reinforced concrete (UHPFRC) specimens with and without longitudinal reinforcement were experimentally tested under direct tensile loading. The variables considered were the volume fraction of fibres (1.0% and 2.0%), the type of steel fibres (straight and hooked end) and the longitudinal steel reinforcement ratio (none and 1.2%). All of the specimens were tested using a servo-controlled fatigue testing machine in displacement control mode. The changes in displacement were monitored using linear variable displacement transducers and the digital image correlation technique. The strain profiles at different loading stages were used to identify the crack evolution process. The average localised strain was found to be 0.2–0.36%, with corresponding crack widths of 0.3–0.6 mm. A uniaxial tensile stress–strain model was developed based on the test results and data from the literature. Longitudinally steel-reinforced specimens showed both stiffening and strengthening effects. Tension-stiffened specimens with 1.0% fibres failed at a higher strain due to the formation of multiple macrocracks. In the specimens with 2.0% fibres, the rebar fractured in a brittle manner due to crack localisation. It is concluded that a higher longitudinal reinforcement ratio is needed to utilise UHPFRC effectively under tension-dominant loads.

Sensitivity Analysis of Parameters Affecting the Seismic Performance of RC Columns Strengthened by Fabric-Reinforced Cementitious Mortar

Abstract In recent years, fabric-reinforced cementitious mortar (FRCM) has emerged as a popular choice for strengthening reinforced concrete and masonry structures due to several advantages over conventional fiber-reinforced polymer (FRP) composites. Particularly, the enhancement of Reinforced Concrete (RC) columns using FRCM composites has garnered significant attention. While experimental investigations are crucial for assessing the effectiveness of FRCM, physical experiments are often resource-intensive and time-consuming. Therefore, this study seeks to investigate the impact of various design parameters on the performance of RC columns strengthened with FRCM under low-amplitude cyclic loads simulating earthquakes through Finite Element (FE) analysis. The FE model, incorporating columns and FRCM strengthening materials, was developed using the DIANA 10.5 program. To assess the reliability of the model, analytical results were compared with experimental findings from a previous study, focusing on lateral strength, hysteresis behavior, and failure modes. The validation outcomes demonstrated a reasonable correlation between the test and numerical results. Subsequently, a sensitivity analysis was conducted to explore the influence of input parameters, such as concrete compressive strength, fabric reinforcement quantity, longitudinal reinforcement ratio of the columns, and pre-axial loading levels, on the seismic performance of RC columns reinforced with FRCM. The findings of the sensitivity analysis were discussed in detail.

Maximum Drift Demands of Earthquake Damaged Reinforced Concrete Columns Based on Residual Flexure Cracks

AbstractAssessment of existing reinforced concrete (RC) structures after an earthquake is a challenging task that must somehow relate qualitative and quantitative observations in the plastic hinge regions and the associated residual deformation capacity of damaged structures. Having an estimate available for the remaining drift capacity will result in more economical and informed decisions regarding demolition or strengthening options. This study aims to develop a practical methodology to estimate the maximum drift demand of an RC column based on the residual crack width. For this purpose, fiber-based frame elements are used to model the RC column considering appropriately concrete behavior in compression and tension stiffening effects. Afterwards, the accuracy and reliability of the proposed methodology are demonstrated by validating the computational approach with two cyclic experimental results from literature and new test data for a one-bay one-story RC frame conducted within the course of this study. A comprehensive parametric study is performed for RC columns with different axial loads, longitudinal and transverse reinforcement ratios, and ground motions to exhibit the stochastic behavior. The study identifies the axial load ratio as the predominant parameter. Key findings include strong correlations between maximum drift ratios and total residual crack widths, as well as maximum compressive strains, with regression analysis yielding equations for accurate drift ratio estimation. Simple predictive models are proposed to estimate the maximum deformation demands based on observed residual crack widths. Residual cracking exceeding 5 mm poses significant risk for the columns with axial load ratios above 0.4, with 90% probability of exceedance 2% drift ratio.

Experimental investigation of band-beam slabs subjected to close-range blast loading

Portable explosions in the form of backpacks and suitcases have been at the forefront of various terrorist activities due to their ability to create unrest in crucial infrastructure such as railway stations. At close range, these portable explosives, with charge sizes ranging from 2 kg to 10 kg, can reasonably damage vital structural elements of a building. For example, the debris produced by breaching one slab can overload and damage the slabs below in a multi-storey structure or pile up to block the access and continuous functioning of a building during rescue operations. A "band-beam slab" or "slab with a shallow beam" is one of the most used slab types in modern multi-storey buildings, especially on basements and lower floors. The band-beam slabs are commonly used to save headspace and floor-to-floor heights of multi-storeyed buildings. Therefore, investigation of the performance of band-beam slabs under close-in detonation is an interest of crucial infrastructure projects. To this end, the work presented in this paper investigates the performance of band-beam slabs subjected to close-in detonations. Thirteen band-beam slabs were subjected to close-in detonations against Composition-4 (C4) charges of sizes varying from 2.5 kg to 4.5 kg. The panels were designed to withstand the overall blast load following the typical design guidelines. However, some variations were introduced in the design to observe the effect of (i) slab reinforcement ratio, (ii) primary longitudinal reinforcement ratio of the beam, (iii) shear link size and spacing in band-beams, and (iv) scaled stand-off distance. In general, all test specimens experienced minor to moderate damage. At the same time, it is observed that the effect of the shear reinforcement ratio and detailing of the reinforcement play a significant role in reducing the spalling and crater formation. The observations have been compared with the UFC-3–340-02 guidelines for spalling and breach and found that experimental results reasonably agree with UFC predictions. Finally, based on the observations, design recommendations in terms of additional reinforcement to control and mitigate spalling, cracking and scabbing were proposed.

Parametric study, finite element analysis, and load capacity calculation for flexural behaviour of seawater and sea sand concrete beams reinforced with GFRP bars

This study sought to enhance the understanding of seawater sea sand concrete (SWSSC) structures reinforced with glass fiber-reinforced polymer (GFRP) bars. To achieve this, an experimental investigation was conducted involving the production and testing of 6 GFRP bar-reinforced SWSSC beams (GFRP beams) alongside 3 ordinary seawater sea sand concrete (OSWSSC) beams (Ordinary beams) to evaluate their flexural performance. Additionally, a subsequent analysis comprised the establishment of 11 full-scale finite element models aimed at parameter assessment on GFRP beams. The experimental and numerical findings revealed that an increase in sea sand replacement ratio in SWSSC beams, with a shear-span ratio of 2.2, led to varying degrees of shear-compression failure. Notably, owing to the superior crack resistance of SWSSC, the beams demonstrated outstanding structural coordination. Compared to OSWSSC beams, GFRP beams with a 100 % replacement ratio of sea sand or an increased in concrete strength to C55 had initial stiffness values that were 150 % and 106 % larger, respectively. Further investigation unveiled that a reduction in the shear-span ratio from 2.5 to 1.0 or an increase in the longitudinal reinforcement ratio from 1.27 % to 2.53 % significantly augmented the ultimate load-carrying capacity, resulting in increases of 88.0 % and 37.7 %, respectively. Based on these findings, several design recommendations are proposed: 1. Establish a deflection limit at l0/500 or implement more stringent measures for GFRP beams. 2. Consider reducing the diameter of GFRP bars while maintaining a 50 % sea sand replacement rate to mitigate crack formation. 3. An excessive longitudinal reinforcement ratio hampers the enhancement of specimen load-carrying capacity. 4. Consider utilizing Chinese specifications for flexural capacity calculations.

Structural behavior of concrete slabs made of seawater sea sand and reinforced with GFRP reinforcement under flexural loading

Seawater sea sand concrete (SSC) structures reinforced with glass fibre-reinforced polymer (GFRP) reinforcing bars offer a promising alternative to conventional reinforced concrete, especially in the face of depleting clean water and river sand. However, comprehensive studies on the flexural performance and cracking behaviour of SSC structures reinforced with GFRP reinforcing bars are currently limited. This study delves into the influence of longitudinal reinforcement ratio on the flexural and cracking behaviour of SSC slabs reinforced with GFRP reinforcing bars under quasi-static loads, as well as the bond behaviour of GFRP reinforcing bar and SSC. The experimental program included 9 large-scale slabs and 30 pull-out specimens, revealing that the longitudinal reinforcement ratio significantly affects the flexural performance, particularly at higher load levels. Increased reinforcement ratio improved flexural stiffness, reduced deflection and crack width, enhancing load-carrying capacity and energy absorption. Although bond strength decreased at the serviceability load (up to 47%), a marginal reduction was observed at the ultimate state. The study proposes a semi-empirical equation for the effective moment of inertia of SSC slabs, accounting for the influence of reinforcement ratio on cracking moment and reduced bond strength of GFRP reinforcing bars. This equation aligns well with experimental results, demonstrating low error and coefficient of variation.

Numerical investigation of the effect of longitudinal steel reinforcement ratio on the ductility of concrete beams

Abstract This research aims to use numerical methods to analyze concrete beams with different reinforcement ratios. Two software packages – ABAQUS and OpenSeesPy – were employed to achieve this task. Empirical stress–strain relationships were utilized to forecast the concrete’s stress–strain behavior. The numerical analysis results were compared with previously published experimental results, and the findings showed a reasonable similarity. The results were consistent with the published laboratory results, particularly for ultimate and yield loads, with no more than 10% differences. However, the ultimate deflection variation was higher. For the first control beam, denoted as B 2−12, ABAQUS predicted a 24.64% difference in ultimate deflection, while OpenSeesPy predicted a 35.83% difference for the second beam, sampled as B 2–16. However, the ultimate deflection for the remaining beams differed by less than 10%. Meanwhile, the difference in yield deflection was greater than in ultimate deflection, with OpenSeesPy showing a maximum difference of 18.51%. The maximum ductility was found to occur at a reinforcement ratio equal to 0.0016. Additionally, OpenSeesPy was faster than ABAQUS in computation while still producing satisfactory agreement with experimental results.

Torsional strength design method and cost analysis of FRP bars reinforced ECC beams without stirrups

Fiber reinforced plastic (FRP) bars reinforced engineered cementitious composites (ECC) beams without stirrups own excellent torsional performance and good application prospect. However, the corresponding torsional strength design method is not available. In order to predict the torsional strength of the ECC beams, a theoretical design method is established in this research. The proposed design method is based on the variable-angle space truss (VAST) model, and the tensile resistance supplied by fibers is carefully considered. The established design method is verified through the experimental results. It can be found that the predicted values agree well with the experimental values. A parametric analysis is carried out. Ultimate torque (i.e., torsional strength) increases significantly with the increment of ECC strength grade or longitudinal reinforcement ratio. However, at the same cross-section area, ultimate torque decreases slightly with the increment of height/width ratio. In addition, the cost effectiveness of the ECC beams without stirrups is discussed. Compared with mortar beam with a stirrup reinforcement ratio of 0.7%, FRP bars reinforced ECC beams without stirrups have small cost/ultimate torque ratio (a reduction ratio of 39.14%–60.86%), indicating that the ECC beams without stirrups own satisfactory cost effectiveness. This study will provide a torsional strength design guideline for FRP bars reinforced ECC beams without stirrups.

The investigation and estimation of flexural strength in shear-critically designed RC beams considering the steel fiber content

Despite numerous studies investigating the effectiveness of steel fibers in RC members subjected to various loading conditions, the majority ignored the impact of the interaction between the tensile reinforcement ratio, compressive strength of fibrous concrete, and steel fiber dosage. This paper aimed to inspect and quantify the effects of hooked-end steel fiber dosage on the bending behavior of RC beams considering the interaction arising from various longitudinal reinforcement ratios. For this purpose, an extensive and hybrid investigation involving both experimental and numerical techniques was conducted. In the experimental part, an investigation was carried out to evaluate the contribution of a specific amount of fiber ratio and various aspect ratios to the behavior of large-scale RC beams having a shear-deficient design. Three beams with a 0.5% hooked-end steel fiber ratio and one without fibers but with a minimum amount of stirrups were produced, and three-point bending tests were conducted. All beams having fibers utilized full flexural strength as in the beam with stirrups. Once the experimental studies were completed, the numerical models were then developed and validated with those of experimental three-point bending tests using the non-linear finite element code VecTor2 to establish a basis for the comprehensive parametric study. The parametric study consisted of 33 analyses. Rebar and volumetric fiber ratios were selected to be variables, and the ratios adopted were within the typical range used in structural engineering applications. Based on the regression analysis a linear and a quadratic model were proposed for estimating the yield and peak strength depending on the steel fiber content. Finally, the obtained models were verified using work from the literature and found to be effective in forecasting the strength of shear-deficient RC beams with 0.8%, 1.0%, and 1.2% tensile reinforcement ratios and hooked end steel fibers (0.5 to 1.5%).

Study on Seismic Mechanical Properties of Reinforced Concrete Energy Dissipation Wall and Seismic Response Analysis of Structure

Utilizing the nonlinear finite element analysis software, ABAQUS, an examination is undertaken to evaluate the ductility characteristics and seismic design methodologies pertinent to a representative reinforced concrete hollow high pier. The research encompasses several focal areas: elucidation of seismic design strategies related to ductility categories, exploration of plastic energy dissipation mechanisms, determination of ductility indices, and delineation of structural measures to enhance ductility. Employing the nonlinear FEA software, ABAQUS, it is recommended that the longitudinal reinforcement ratio for ductile piers fall within the range of 0.6% to 4%. Furthermore, for flexible bridge piers, the maximum spacing of confinement reinforcements should either exceed 100 mm, be sixfold the diameter of the longitudinal reinforcement, or equate to at least one-quarter of the pier column’s bending direction section width. Combined with the influence of high pier ductility seismic axial pressure ratio, reinforcement, concrete factors such as factor analysis results, put forward and checking a reinforced concrete hollow high pier ductility seismic optimization scheme, increase the strength of the plastic hinge area section, through the comparative analysis in different seismic strength of plastic hinge unit cloth, maximum ductility coefficient and pier top displacement to verify its influence on the ductile seismic.

Behaviour of steel-reinforced recycled aggregate concrete-filled GFRP tubular short columns under eccentric axial compression

Since the mechanical properties of recycled aggregate concrete (RAC) are different from those of natural aggregate concrete (NAC), the mechanical behaviour of reinforced RAC members has attracted great interest. Meanwhile, fibre-reinforced plastics (FRP) have been applied to improve the load capacity of concrete members owing to their good durability. This study primarily focused on the performance of glass FRP (GFRP) confined steel-reinforced RAC short columns (FCSRAC) under eccentric compression. In this study, 29 FCSRAC were used to understand the effects of the recycled coarse aggregate (RCA) replacement rate, strength of RAC, eccentric distance, fibre orientation of the GFRP tube, strength of the GFRP, and longitudinal reinforcement ratio on the eccentric compression behaviour. The results show that the longitudinal steel bar ratio and hoop strength of the GFRP tube play a critical role in the load capacity of the FCSRAC, especially at large eccentric distances. With improved steel bars and GFRP tubes, RAC can be used in core concrete to replace NAC in a column. In addition, a prediction model of the load capacity of the FCSRAC was proposed based on Samaan's model and the static equilibrium principle, introducing the eccentric distance, fibre orientation of the GFRP tube, and RCA replacement rate. The predicted results agree with the experimental results.

Finite element analysis of the seismic performance of PVC-CFRP confined concrete column-ring beam interior joints

This paper presents a finite element (FE) analysis of the seismic performance of PVC-CFRP confined concrete column-ring beam interior joints (PCCC-RBIJs) under low cyclic loading. Based on the constitutive relationship of materials, a FE model was established using ABAQUS and validated against the experimental results of ring beam joints found in the literature. Then, FE parametric analysis was performed to investigate the influence of studied parameters on the seismic performance of the PCCC-RBIJs. These studied parameters included the axial compression ratio, height-diameter ratio of the ring beam joint, column longitudinal reinforcement ratio, reinforcement ratio and stirrup ratio of ring beam, and joint concrete strength. The FE analysis showed that the seismic performance of PCCC-RBIJ specimens can be enhanced by increasing their axial compression ratio, column longitudinal reinforcement ratio, and ring beam reinforcement ratios or decreasing their height-diameter ratio of the ring beam joint. Although the joint concrete strength and ring beam stirrup ratio have little effect on the seismic performance of the joint, the ring beam stirrup ratio affects the stirrup utilization. The paper also provides design suggestions for PCCC-RBIJs.

Flexural Behavior of Alkali-Activated Ultra-High-Performance Geopolymer Concrete Beams

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

Comparative Analysis of Shear Strength Prediction Models for Reinforced Concrete Slab–Column Connections

This research focuses on a comprehensive comparative analysis of shear strength prediction in slab–column connections, integrating machine learning, design codes, and finite element analysis (FEA). The existing empirical models lack the influencing parameters that decrease their prediction accuracy. In this paper, current design codes of American Concrete Institute 318-19 (ACI 318-19) and Eurocode 2 (EC2), as well as innovative approaches like the compressive force path method and machine learning models are employed to predict the punching shear strength using a comprehensive database of 610 samples. The database consists of seven key parameters including slab depth (ds), column dimension (cs), shear span ratio (av/d), yield strength of longitudinal steel (fy), longitudinal reinforcement ratio (ρl), ultimate load-carrying capacity (Vu), and concrete compressive strength (fc). Compared with the design codes and other machine learning models, the particle swarm optimization-based feedforward neural network (PSOFNN) performed the best predictions. PSOFNN predicted the punching shear of flat slab with maximum accuracy with R2 value of 99.37% and least MSE and MAE values of 0.0275% and 1.214%, respectively. The findings of the study are validated through FEA of slabs to confirm experimental results and machine learning predictions that showed excellent agreement with PSOFNN predictions. The research also provides insight into the application of metaheuristic models along with ANN, revealing that not all metaheuristic models can outperform ANN as usually perceived. The study also highlights superior predictive capabilities of EC2 over ACI 318-19 for punching shear values.

Investigation of shear response due to variation of fiber volume fraction, transverse steel, and placement method on short span R/UHPC beams

This study investigates the response of small-scale, reinforced ultra high performance concrete beams. Seven specimens were cast and experimentally tested. Steel fiber volume fraction, amount of longitudinal and transverse steel reinforcement, and casting direction varied between specimens. High longitudinal reinforcement ratios of 4.1% and 9.5% were expected to drive relatively large shear demands and low steel fiber volume fractions of 0.5% and 1% were expected to decrease the UHPC’s ability to resist tension, shear, and compression. Specimens were either cast at one end or mid-span. All specimens failed in shear, as expected. R/UHPC beams with only 0.5% fibers and a stirrup spacing equal to half the beam’s depth carried more ultimate load than beams with 1% fibers and twice the stirrup spacing. At a 0.5% fiber volume fraction, UHPC performed well, exhibiting fiber bridging in tension and resisting spalling in compression. As longitudinal reinforcement ratio increased from 4.1% to 9.5%, load carrying capacity generally increased, but not proportional to the increase in steel. Placement method did not influence fiber orientation in the R/UHPC beams when measured in 2D planes transverse or longitudinal to the specimens’ major axis. The longitudinal and transverse reinforcement interrupted fiber flow and prevented significant fiber alignment; combined with the short span of the beams, these factors mitigated the influence of placement method.

Flexural behavior of RC beams with multiple parallelogram openings

On account of the detrimental effects of the post-drilling holes in hardened RC beams, designing the beams with transverse openings before construction is becoming more popular in the last decades. The contribution of the transverse openings to the overall economy and efficiency of construction by reducing the unusable dead space in the floor height is a rather significant motivation behind the vast number of studies on this topic. In search for the opening geometries and reinforcement schemes with the least negative effects on the beam behavior, the present study focused on the parallelogram (diamond) opening geometry, which is thought to facilitate the transmission of diagonal compression forces in the beam web thanks to the inclination of the posts. Within this scope, a total of 12 beams, including two reference beams without openings, were tested under four-point bending. Circular, square and parallelogram (45°−60°−75°) opening geometries were adopted and the test results were evaluated based on the opening geometry and the longitudinal reinforcement ratio. In order to avoid various shear failure modes of beams with openings, different special reinforcement schemes were employed around the web openings. Two different longitudinal reinforcement ratios were used to understand if pure flexural failure can be reached in RC beams with openings without being affected by different shear failure modes (beam- and frame-type diagonal tension and diagonal compression). The inclination angle of the posts between the openings in parallelogram opening geometry was found to be the most crucial parameter in the final beam failure and beam ductility. The use of diagonal cables surrounding the openings and connecting the posts and chords was established to be obligatory in square and parallelogram opening geometries to reach a ductile beam behavior without being affected by Vierendeel panel action and different shear failure modes.

A comparative study of LightGBM, XGBoost, and GEP models in shear strength management of SFRC-SBWS

Steel fiber reinforced concrete (SFRC) was revealed to have superior mechanical properties compared to plain concrete, especially under shear loads. However, Due to a lack of prediction models for SFRC-Slender Beams without Stirrups (SFRC-SBWS) in the available literature, the application of SFRC-SBWS in reinforced concrete (RC) constructions is limited. This research aims to fill a literature gap by analyzing different Machine Learning (ML) algorithms, including Extreme Gradient Boosting (XGBoost), Light Gradient Boosting Machine (LightGBM), and Gene Expression Programming (GEP), to forecast the shear strength of SFRC-SBWS specimens. A database of 333 tested SFRC-SBWS specimens was collected and analyzed. The results revealed the LightGBM and XGBoost algorithms surpassed other studied algorithms with Coefficient of determination (R2) = 95.74% and 93.27%, Root Mean Square Error (RMSE) = 20.04 kN and 25.19 kN, respectively. A GEP-based closed-form model was suggested to forecast the shear strength, considering the most important factors, including beam depth effect, beam width, and longitudinal steel reinforcement ratio. The proposed GEP model has an R2 = 91.12% and RMSE = 101.44 kN, showing a slightly lower prediction accuracy. The effectiveness of the studied models was evaluated from various angles, and the results demonstrate the importance of managing new technological advancements to create reliable support methods. Engineers that use these approaches get a dependable tool for estimating shear resistance, which is crucial in guaranteeing the safety and lifespan of RC structures. The successful combination of classic engineering approaches and revolutionary ML strategies indicates the potential for improving accuracy and reducing bias in prediction-oriented investigations. As the engineering field supports technological improvements, combining robust and efficient prediction models, as described in this paper, can contribute considerably to resilient structure design and safety assurance. This leads to sustainable and robust management of structures with greater confidence in predictions.

Ensuring Structural Integrity: An Evaluation of Vertical Shortening in Tall Concrete Buildings

Vertical shortening, a phenomenon inherent to concrete structures, plays a key role in the quality and safety of construction, particularly in tall reinforced concrete buildings. This behavior is intrinsically linked to the time-dependent properties of concrete, encompassing both creep and shrinkage. Neglecting these aspects, especially when non-uniformly distributed, can give rise to various structural issues, including partition distress, overloading, and potential cracking in horizontal elements. This paper delves into the principal factors influencing vertical shortening and presents a rigorous approach to their evaluation, treating creep and shrinkage as critical parameters. The investigation employs two illustrative case studies: the first revolves around a 15-story reinforced concrete building with single columns supporting tributary areas at various levels, acting as a calibration case; the second encompasses a 30-story reinforced concrete structure employing a dual system, providing a broader perspective applicable to three-dimensional structures. A diverse array of analyses is conducted, incorporating considerations for concrete’s linear and nonlinear behavior as well as the impact of construction stages. Our findings reveal that vertical shortening is directly proportional to the building’s height and inversely related to concrete strength, longitudinal reinforcement ratios, member dimensions, volume-to-surface ratios, age of the structure upon load application, and relative humidity. Consequently, precise assessments of differential shortening effects are paramount. The utilization of staged construction analysis and time-dependent effects is recommended as the most suitable approach for evaluating vertical shortening effects.

A Machine-Learning-Based Failure Mode Classification Model for Reinforced Concrete Columns Using Simple Structural Information

The seismically deficient column details in existing reinforced concrete buildings affect the overall behavior of the building depending on the failure type of the column. The purpose of this study is to develop and validate a machine-learning-based prediction model for the column failure modes (shear, flexure–shear, and flexure failure modes). For this purpose, artificial neural network (ANN), K-nearest neighbor (KNN), decision tree (DT), and random forest (RF) models were used considering previously collected experimental data. Using four machine learning methodologies, we developed a classification learning model that can predict the column failure modes in terms of the input variables using the concrete compressive strength, steel yield strength, axial load ratio, height-to-dept aspect ratio, longitudinal reinforcement ratio, and transverse reinforcement ratio. The performance of each machine learning model was compared and verified by calculating the accuracy, precision, recall, F1-Score, and ROC. Based on the performance measurements of the classification model, the RF model has the highest average value for the classification model performance measurements among the considered learning methods and can conservatively predict the shear failure mode. Thus, the RF model can rapidly predict the column failure modes with the simple column details. Additionally, it was demonstrated that the predicted failure modes from the selected model were exactly same as the failure mode determined from a code-defined equation (traditional method).

Structural behavior of RPC beams subjected to flexural and torsional effects

This research is concerned with the behavior of reactive powder concrete beams (RPC) under the combined effects of bending and torsion moments, with three main parameters: torsional to bending moments ratio (T/M), longitudinal reinforcement ratio ( ), and transverse reinforcement ratio ( ). 12 rectangular reinforced RPC beams with dimensions of (1500 200 150) mm were tested. The outcome demonstrated that increasing the longitudinal reinforcement ratio from =0.009 to =0.016 improved the ultimate capacity significantly by 34.16%, and 35.54% in cases of (T/M) =0, and 0.5 respectively, also it significantly improved moment-deflection response in the case of (T/M) = 1, and well improved torque-rotation response in cases of (T/M)=0.5, and 1. Increasing the transverse reinforcement ratio from = 0.0042 to =0.0075 improved the ultimate capacity significantly by 49.22% in case of pure torsion and slightly improved it in other cases. Also it significantly improved moment- deflection response in case of (T/M) = 1 and improved torque -rotation response in cases of (T/M)=1and ꝏ.