2031 research outputs found
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Effects of GFRP Stirrup Spacing on the Behavior of Doubly GFRP-Reinforced Concrete Beams
Get PDFThis study investigates the impact of varying glass fiber-reinforced polymer (GFRP) stirrup spacing on the performance of doubly GFRP-reinforced concrete beams. The research focuses on assessing the behavior of GFRP-reinforced concrete beams, including load-carrying capacity, cracking, and deformability. It explores the feasibility and effectiveness of GFRP bars as an alternative to traditional steel reinforcement in concrete structures. Six concrete beams with a cross-section of 300 mm (wide) í— 250 mm (deep), simply supported on a 2100 mm span, were tested. The beams underwent four-point bending with two concentrated loads applied symmetrically at one-third of the span length, resulting in a shear span (a)-to-depth (h) ratio of 2.8. The experimental findings reveal that altering the GFRP stirrup spacing along the longitudinal axis of the beams, from 200 mm (equivalent to the effective depth (d)) to 50 mm (equal to (dâ„4)), altered the mode of failure from flexure-shear to flexure-compression. However, when the spacing was equal to or less than (dâ„3), there was no significant improvement in load-carrying capacity, as the contribution of GFRP bars in resisting shear loads was limited. Under service loads, the GFRP-reinforced beams exhibited wider cracks, but reducing the stirrup spacing helped restrain crack widening. Incorporating GFRP bars in the compression zone had a positive effect on reducing crack width in the tension zone. Additionally, using GFRP stirrups with spacing varying between (d) and (dâ„2) in the pure bending region increased the deflection ductility indexes. To enhance the ductility of GFRP-reinforced concrete beams, it is recommended to use GFRP stirrups in the pure bending region with spacing greater than the spacing between GFRP stirrups in the shear spans. The study highlights that the current ACI code overestimates the shear capacity provided by GFRP stirrups, particularly when the spacing is less than or equal to (dâ„3). Doi: 10.28991/CEJ-2024-010-02-011 Full Text: PD
Ensemble Learning Models for Prediction of Punching Shear Strength in RC Slab-Column Connections
Get PDFIn reinforced concrete (RC) structures, accurate prediction of the punching shear strength (PSS) of slab-column connections is imperative for ensuring safety. The existing equations in the literature show variability in defining parameters influencing PSS. They neglect potential variable interactions and rely on a limited dataset. This study aims to develop an accurate and reliable model to predict the PSS of slab-column connections. An extensive dataset, including 616 experimental results, was collected from earlier studies. Six robust ensemble machine learning techniques”random forest, gradient boosting, extreme gradient boosting, adaptive boosting, gradient boosting with categorical feature support, and light gradient boosting machines”are employed to predict the PSS. The findings indicate that gradient boosting stands out as the most accurate method compared to other prediction models and existing equations in the literature, achieving a coefficient of determination of 0.986. Moreover, this study utilizes techniques to explain machine learning predictions. A feature importance analysis is conducted, wherein it is observed that the reinforcement ratio and compressive strength of concrete demonstrate the highest influence on the PSS output. SHapley Additive exPlanation is conducted to represent the influence of variables on PSS. A graphical user interface for PSS prediction was developed for users' convenience. Doi: 10.28991/CEJ-SP2024-010-01 Full Text: PD
Evaluating the Performance of Right Turn Lanes at Signalized Intersection Using Traffic Simulation Model
Get PDFThe issue of traffic congestion at signalized intersections is a concern in transportation systems due to the growth of urban areas and increased vehicular transportation. To study the evolution of congestion and evaluate the traffic performance operation of signalized intersections under problematic congested and improved conditions, the microscopic simulation VISSIM software is utilized. The objectives of this paper are to evaluate operational techniques, build a simulation model, and produce a well-calibrated and validated model. The methodology procedure to evaluate the signalized intersection involves the application of a traffic simulation model to observe real-time delays and stopped vehicles. Using the VISSIM software Version 9 to create an intersection model and redesign geometry with an exclusive right turn to enhance the intersection functionality and reduce delay. Our research focused on the Al-Nakhala signalized intersection located in the southern part of Palestine urban street in Baghdad city. This intersection is one of the busiest along the corridor due to significant land-use changes in the study area, including residential, educational, or commercial areas generating daily pressure from additional trips and saturating the absorptive capacity of the intersections. The proposed scenario of an exclusive right–turn could reduce the queue length and vehicle delay at the signalized intersection, resulting in a more efficient traffic operation. As a result of the reduction in vehicle delay, the Level of service (LOS) for the north, west, and east approaches improved from F to D. However, there was only a slight improvement for the south approach, with the LOS changing from E to F. Nonetheless, there was a noticeable reduction in queue length and vehicle delay ranging from 25% to 50%. Doi: 10.28991/CEJ-2024-010-07-010 Full Text: PD
Enhancing the Flexural Capacity of Reinforced Concrete Beam by Using Modified Shear Reinforcement
Get PDFMany researchers have studied how modifying conventional shear reinforcement into spiral and truss systems improves the behavior of RC beams. However, there is a scarcity of studies investigating the influence of spiral reinforcement, and limited research is available on the flexural capacity of beams utilizing truss reinforcement systems. Additionally, recent designs focused only on the rectangular spiral and rectangular truss systems, underscoring the necessity of incorporating a new design of modifications in the stirrup configurations. These gaps must be addressed to identify the most effective design for achieving the desired flexural capacities. As a result, the present study conducts a simulation and experimentation on RC beams utilizing modified stirrups through the Abaqus software to describe the load-deflection relationship, determine the flexural capacity and ductility, and analyze the failure mode and crack patterns. The present study simulated seventeen finite element models, including one control beam as BN and four various designs that used rectangular spiral (BR-S), rectangular truss system (BT-R), and a new modification, namely vertical X-shaped stirrups (BV-X), and X-shaped truss system (BT-X) with four spacings of 150mm, 125mm, 100mm, and 75mm. The findings reveal that the most effective enhancement in RC beam behavior was observed within the BT-R group, particularly with BT-R 100, which demonstrated a remarkable 6.551% increase in flexural capacity compared to BN. Moreover, stirrup spacing and inclination considerably impact the beam's performance, depending on the various modifications of stirrups in RC beams. Furthermore, uniform failure modes have been observed across all models and specimens, including BN, demonstrating that modified stirrups improve RC beam performance. The present study compared and verified the finite element simulation results through an actual experiment from BN and BT-R 150 models and specimens. Doi: 10.28991/CEJ-2024-010-06-02 Full Text: PD
Study on Solutions for Early Dismantling of Aluminum Formwork Systems in High-Rise Building Construction
Get PDFThis paper evaluated the impact of early aluminum formwork (AF) removal on the structural integrity of reinforced concrete (RC) beam-slab systems, specifically focusing on punching shear capacity, deflection, and crack width. The study provided a comprehensive analysis of the AF system, detailing its erection and dismantling sequences while examining its advantages and disadvantages. Moreover, safety principles for early formwork removal were proposed in accordance with the Vietnamese code (TCVN 5574:2018). By utilizing calculation examples based on actual high-rise building constructions and employing the finite element method, the study offered practical guidelines for the safe and effective use of AF systems, balancing rapid construction with structural safety. The findings emphasized the importance of assessing punching shear, deflection, and crack width criteria at the time of formwork removal to ensure structural safety. Results indicated that RC beam-slab systems remain safe in terms of punching shear capacity, deflection, and crack width if the shoring span does not exceed 1.6m when the concrete reaches its design strength. Furthermore, early removal of AF was feasible when the concrete achieved a strength grade of B12.5, with a shoring span of up to 1.6 m and a minimum slab thickness of 200mm. This study also contributed novel insights into optimizing construction efficiency by offering practical guidelines for the safe and effective use of AF systems, thus providing valuable recommendations for construction professionals and engineers. Doi: 10.28991/CEJ-2024-010-10-07 Full Text: PD
Flexural Behavior of Reinforced Concrete Beams with Steel-Plate Reinforced Vertical Opening
Get PDFThe structural response of simply supported Reinforced Concrete (RC) beams with square vertical openings is investigated in this work. Studies were conducted using seven specimens of RC beams, with the aim of comparing beams with vertical openings to those without. Meanwhile, the other beams featured carefully positioned square openings. Note that one of these beams served as the control and had no openings. Each beam was the same length (1400 mm) with a 180í—120 mm cross-section. Two-point loads were applied over a span of 1200 mm throughout the testing method, with a central load placed 300 mm from the ends. The openings were positioned in the middle of the span and came in three different widths: 20, 40, and 60 mm. Openings were made using either 1.5 mm thick square steel tubing or none at all. The major goal of this study was to determine whether the steel tube could compensate for the decrease in beam strength and the impact of decreasing beam cross-section (producing opening). Correspondingly, the beam ultimate load was found to decrease by 15.75%, 24.2%, and 32.5% for opening widths of 20 mm, 40 mm, and 60 mm, respectively, as the opening width increased. On the other hand, the performance gain for beams strengthened with steel plates when steel tubes were used was 11.78%, 12.14%, and 13.28% for the respective opening widths. Doi: 10.28991/CEJ-2024-010-09-04 Full Text: PD
Evaluation of Tidal Energy Potential Using a Two-Way Tidal Energy Model
Get PDFTidal energy is a renewable energy source that provides sustainable energy through the utilization of tidal differences, making it a very promising option. This study examines a more effective tidal energy reservoir model by building a 1:100 scale prototype in the laboratory with several predetermined variations, namely an earthen pond (100, 80, and 60 cm), and flow holes (1.5, 1, and 0.5 cm) with initial tidal height differences of 10 cm, 15 cm, and 20 cm. The model uses a 6-hour time period, which corresponds to a semidiurnal tidal model. The results showed that the highest energy output was 281.84 kWh, achieved with a 1.5 cm flow hole, 20 cm tidal height difference for the initial condition, and 80 cm pond width. For a 1 cm flow hole, the outputs were 1774.8 kWh and 1803.78 kWh for 15 cm and 20 cm tidal height difference for the initial condition with a pond width of 100 cm. Meanwhile, the 0.5 cm flow hole produces potential energy outputs of 2623.8 kWh and 2611.4 kWh for different tidal heights of 15 cm and 20 cm for the initial condition with a pond width of 100 cm. Better model performance can be connected to a mini generator to validate the energy generated from the designed prototype model. Doi: 10.28991/CEJ-2024-010-09-016 Full Text: PD
Durability of Fiber-Reinforced Polymer (FRP) Bars: Progress, Innovations and Challenges Based on Bibliometric Analysis
Get PDFThis review systematically examines the literature on the Fiber-Reinforced Polymer (FRP) bars durability in concrete matrices using bibliometric analysis to understand progress, innovations, and challenges. The objective is to explore the durability of FRP bars, which are recognized for their strength-to-weight ratio, corrosion resistance, and non-conductivity, as a potential substitute to conventional steel reinforcement. Methods involved employing bibliometric tools such as Biblioshiny and VOSviewer to analyze trends, collaboration patterns, and the global distribution of publications. Findings reveal an increase in research activity over the past two decades, significant international collaboration, and leading contributions from key countries. Critical environmental factors like alkalinity, thermal conditions, and chemical aggressors affecting the interface of fiber-matrix mechanical properties were highlighted. Advances in predictive modeling for long-term behavior conditioned FRP bars are studied, steering future research towards improved durability and sustainable construction practices. This study contributes novelty by providing a comprehensive bibliometric perspective on FRP bar durability, identifying emerging trends, and suggesting areas for future suggested research to enhance the reliability and application of FRP bars in construction. Doi: 10.28991/CEJ-SP2024-010-09 Full Text: PD
Development of Pavement Deterioration Models Using Markov Chain Process
Get PDFA common phenomenon in developing countries is that the function of the pavement in the road network will experience structural damage before the completion of life is reached, and the uncertainty of pavement damage is difficult to predict. Planning for maintenance treatment depends on the accuracy of predicting future pavement performance and observing current conditions. This study aims to apply the Markovian probability operational research process to develop a decision support system predicting future pavement conditions. Furthermore, it determines policies and effectiveness in managing and maintaining roads. A standard approach that can be used by observing the history of pavement damage from year to year is to estimate the transition probability as a Markovian-based performance prediction model. The results show that the application of the model is quite optimal, changes in pavement conditions after repair can be easily compared with an increase in good condition, reaching 92.8%. Routinely and consistently handling road deterioration will give favorable results regarding pavement condition value. This will ease in the management of the road network and the accomplishment of the optimal maintenance and repair policies. Doi: 10.28991/CEJ-2024-010-09-012 Full Text: PD
Increasing the Efficiency of Underground Block Leaching of Metal
Get PDFThe purpose of this study is to increase the efficiency of underground block metal leaching by increasing the metal content in the pregnant solution using the cavitation effect. To achieve this goal, it is proposed to process (cavitate) the leaching solution on the injector. The following research methods were used in this study: analysis of the current state of scientific and technical problems and research, laboratory work to establish the effect of the treated (cavitated) solution on the metal content in the pregnant solution, collection and processing of statistical data from laboratory work, analysis of research results, and preparation of conclusions. According to the results of laboratory research, leaching with a treated solution on an injector leads to an increase in the content of a useful component in the pregnant solution. The maximum increase in the metal content in the pregnant solution was achieved by processing the leaching solution for 5 min. The effectiveness of the solution over time after treatment was maintained for a long time (up to one month). Changes in the solution pressure did not affect the effectiveness of the treated leaching solution. The scientific novelty of this work consists of determining the dependence of the content of the useful component in the pregnant solution on the time of processing the leaching solution on the injector and the leaching time, which determines the optimal time for processing the solution on the injector to obtain the maximum metal content in the pregnant solution. The dependence of the content of the useful component in the solution on the pressure during leaching with untreated and treated solutions on the injector was obtained. Doi: 10.28991/CEJ-2024-010-10-014 Full Text: PD