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Abstract This study focused on sustainable and novel development of concrete through treated and untreated plastic waste aggregates. In this study, the surface of Elec-waste coarse aggregates was treated with sulfuric acid, marble dust coating, silica fume coating, and alkaline bleach. Elec-waste aggregates were used in concrete by replacing natural coarse aggregates in amounts of 10%, 20%, and 30%. The 10%, 20%, and 30% Elec-waste replacement ratios resulted in the compressive strength reduction of 8.97%, 27.99%, and 42.01%, respectively. The same percentage of Elec-waste aggregates reduced the splitting tensile strength by 21.77%, 35.89%, and 47.89%, respectively. However, the slump was observed to increase by 41.4%, 52.1%, and 68.8%, respectively. All the considered treatments enhanced the performance of Elec-waste aggregate concrete (E-WAC). Overall, the best improvement in the performance of E-WAC was imparted by silica fume coating, irrespective of the quantity of Elec-waste aggregates. The present study proposed an expression to estimate the reduction of the compressive strength of E-WAC. It was demonstrated that the equation by JCI-08 predicted splitting tensile strength of E-WAC close to experimental results.

The manufacturing of Ordinary Portland Cement (OPC) is one of the primary contributors to atmospheric CO2. The use of high-volume OPC replacement materials in self-compacting concrete (SCC) has been the focus of several investigations owing to the increased demand for environmentally friendly building materials. This paper presents the experimental investigation of the properties of SCC, where 25–70 % OPC was replaced with fly ash and calcined calcium carbonate (BCC). Different experimental tests, such as workability, mechanical properties, durability, and microstructural characteristics, have been carried out. The test results of workability showed that all the mixes were conforming to satisfactory conditions of EFNARC for the T500 flow timings within the range from 2.50 to 4.55 seconds and slump flow values within the range from 650 to 800 mm. This mix, here called 20F5C, had optimum behaviour with its 91-day compressive strength of 73.8 MPa, a gain of 7.7 % over the control. Replacement ratio, microstructure, and mechanical properties were correlated. Even high-replacement mixes like 50F20C provided a 91-day compressive strength of 58.9 MPa. This clearly shows the prospect of a considerable reduction in cement consumption while maintaining structural integrity. These results indicate the possibility of reduced OPC consumption in concrete production, which again identifies low carbon emission and utilization of waste according to international sustainability goals. The findings have revealed that SCC made with high-volume replacements of OPC could be an economically viable and environmentally friendly solution for the construction industry worldwide.

Recent research have highlighted the potential of hybrid confinement, combining high tensile strength fiber-reinforced polymers with large rupture strain confinement. This study presents experimental findings on 64 cylindrical and square-shaped specimens tested under axial compression, introducing a novel hybrid confinement method utilizing low-cost fiberglass chopped strand mat sheets and cotton ropes (COFS confinement). The experimental and analytical results yielded several key conclusions. Firstly, circular specimens exhibited significant peak strength increases in various subgroups, with enhancements ranging from 97.5 % to 285.5 %, and ultimate strain improvements ranging from 588.6 % to 1650.0 %. Similarly, square specimens under COFS confinement also demonstrated notable enhancements in ultimate strength and strain, with increases up to 244.7 % and 1083.0 %, respectively, particularly evident with higher levels of confinement. The influence of cross-sectional shape on compressive strength, strain, and energy dissipation was noted, with COFS confinement notably improving these factors for circular sections. Additionally, the study found that as the unconfined compressive strength increased, the enhancement in compressive strength, ultimate strain, and energy dissipation decreased. Moreover, the confinement ratio positively affected axial behavior improvement, with a proportional enhancement observed. However, the efficacy of the confinement ratio was influenced by cross-section type and plain concrete strength, emphasizing the need for considering these factors in COFS-based confinement design. Lastly, an analytical design-oriented model proposed for approximating stress vs. strain curves of COFS-confined concrete showed close agreement with experimental results, providing valuable insights for future design considerations.

Recent earthquakes have highlighted the need to strengthen existing structures with substandard designs. NFRPs provide a sustainable, cost-effective alternative for strengthening, but accurately predicting their performance remains a challenge. This study investigates the use of machine learning algorithms for predicting the compressive strength concrete specimens confined with various NFRPs. Four algorithms were employed: decision tree, random forest, neural network, and gradient boosting regressor. A diverse dataset encompassing various geometries, material properties, and confinement configurations was used to train and evaluate the models. Gradient boosting regressor (GBR) achieved the highest performance, with an average R-squared value of 0.94 and low mean absolute error (MAE) and root mean squared error (RMSE) during training and k-fold cross-validation. Neural network and random forest also demonstrated satisfactory performance, with average R-squared values of 0.88 and 0.86, respectively, during cross-validation. These results suggest that machine learning holds promise for predicting the compressive strength of concrete confined with NFRPs. GBR offers the most accurate predictions, making it a valuable tool for engineers seeking to optimize the design and performance of strengthened structures using sustainable materials.

This paper presents a comprehensive investigation into the behavior of concrete confined with hybrid Basalt and Chopped Strand Mat (B-CSM) fibers. The newly proposed B-CSM confinement technique substantially enhances the brittle compressive stress-strain behavior, leading to a noteworthy increase in peak strength (approximately 90%) and ultimate strain (approximately 461 %). The efficiency of B-CSM confinement is affected by the strength of plain concrete, with lower-strength specimens indicating a more pronounced enhancement. The performance of existing analytical models for FRP confinement in predicting ultimate strength and strain in B-CSM confined concrete is assessed, highlighting the need for tailored models. Regression-based equations are proposed for characteristic points along the stress-strain curve, enabling accurate prediction of material behavior. The predicted stress-strain curves exhibit a high level of agreement with experimental results. These findings provide valuable insights for the design and application of B-CSM confinement techniques in structural engineering, facilitating improved performance and ductility of concrete structures under compressive loading conditions.

Abstract This study explores the potential use of low-cost natural fiber reinforced rope polymers (FRRP) to improve the compressive behavior of circular, square, and rectangular reinforced concrete (RC) specimens. A total of 42 specimens were tested under monotonic axial compression in three groups. Groups were formed to differentiate specimens with different cross-sectional shapes such as circular, square, and rectangular. The findings demonstrate that FRRP can effectively boost the compressive behavior of RC columns. Circular specimens with three-layer hemp FRRP exhibited a 200% increase in compressive strength and a 270% improvement in corresponding strain. Cotton FRRP provided a 117% boost in compressive strength and a 233% enhancement in strain. In square specimens, three-layer hemp FRRP resulted in a 110% rise in compressive strength and a 186% increase in strain, while cotton confinement yielded improvements of 95% and 144%, respectively. For the square and rectangular specimens, the improvement in the compressive behavior was reduced compared to the circular specimens because of stress concentrations near corners. Moreover, the study showed that the hemp FRRP confinement outperformed the cotton confinement. The investigation also revealed that the existing analytical models were inadequate in predicting the mechanical properties of RC confined with natural FRRP. Therefore, the study introduces novel equations to predict the compressive strength and corresponding strain for both hemp and cotton confined concrete in various cross-sectional types. These proposed equations exhibit a good level of accuracy in predicting the compressive strength and corresponding strain.

Abstract This research work investigates the axial stress versus strain responses of un-strengthened and carbon fiber reinforced polymer (CFRP) composites strengthened concrete specimens made with electronic waste coarse aggregates. For this purpose, 36 circular and non-circular 300 mm high concrete specimens constrained with CFRP sheets and partially replaced with E-waste coarse aggregates were prepared. The effect of cross-sectional geometry, 20% partial substitution of natural coarse aggregates with E-waste aggregates, corner effect of non-circular concrete specimens, confinement of specimens with CFRP sheets, and effect of the number of confinement sheets were also studied. In control concrete specimens, the coarse aggregates were 848 kg/m3 and E-waste aggregates were 212 kg/m3. The cement was 475 kg/m3 and fine aggregates were 655 kg/m3. Test results indicated that compressive strength is reduced by substituting natural coarse aggregates with E-waste aggregates. At the same time, compressive strength increased to 71%, 33%, and 25% for circular, square, and rectangular concrete specimens, respectively, by CFRP confinement. Whereas the axial strain increased to 1100%, 250%, and 133%, for circular, square, and rectangular concrete specimens, respectively, by CFRP confinement. CFRP sheets also enhanced the Poisson's ratio. Because of the greater confinement given by a double CFRP layer, it is more effective than a single layer. Furthermore, results also indicated that strength reduction in non-circular concrete specimens was greater than in circular concrete specimens for all studied cases. In the end, for theoretical calculations, strength and strain models for confined concrete suggested by different researchers were applied and compared with experimental results. In comparison to the experimental findings, theoretical data showed that most of the models were either on the higher or on the lower side, while only some model results matched well with the experimental data.

Abstract This study presents an experimental and finite element analysis of reinforced concrete beams with solid, hollow, prismatic, or non-prismatic sections. In the first part, a total of six beams were tested under four-point monotonic bending. The test matrix was designed to provide a comparison of structural behavior between prismatic solid and hollow section beams, prismatic solid and non-prismatic solid section beams, and prismatic hollow and non-prismatic hollow section beams. The intensity of shear was maximum in the case of prismatic section beams. The inclusion of a tapered section lowered the demand for shear. In the second part, Nonlinear Finite Element Modeling was performed by using ATENA. The adopted modeling strategy resulted in close agreement with experimental crack patterns at ultimate failure. However, the ultimate failure loads predicted by nonlinear modeling were generally higher than their corresponding experimental results. Whereas in the last part, the developed models were further extended to investigate the effect of the strength of concrete and ratio of longitudinal steel bars on the ultimate load-carrying capacity and cracking behavior of the reinforced concrete beams with solid, hollow, prismatic, or non-prismatic sections. The ultimate loads for each beam predicted by the model were found to be in close agreement with experimental results. Nonlinear modeling was further extended to assess the effects of concrete strength and longitudinal reinforcement ratio on failure patterns and ultimate loads. The parametric study involved beams reinforced with glass fiber-reinforced polymer (GFRP) bars against shear and flexural failure. In terms of ultimate load capacities, diagonal cracking, and flexural cracking, beams strengthened with GFRP bars demonstrated comparable performance to the beams strengthened with steel bars.

This research suggested natural hemp fiber-reinforced ropes (FRR) polymer usage to reinforce recycled aggregate square concrete columns that contain fired-clay solid brick aggregates in order to reduce the high costs associated with synthetic fiber-reinforced polymers (FRPs). A total of 24 square columns of concrete were fabricated to conduct this study. The samples were tested under a monotonic axial compression load. The variables of interest were the strength of unconfined concrete and the number of FRR layers. According to the results, the strengthened specimens demonstrated an increased compressive strength and ductility. Notably, the specimens with the smallest unconfined strength demonstrated the largest improvement in compressive strength and ductility. Particularly, the compressive strength and strain were enhanced by up to 181% and 564%, respectively. In order to predict the ultimate confined compressive stress and strain, this study investigated a number of analytical stress–strain models. A comparison of experimental and theoretical findings deduced that only a limited number of strength models resulted in close predictions, whereas an even larger scatter was observed for strain prediction. Machine learning was employed by using neural networks to predict the compressive strength. A dataset comprising 142 specimens strengthened with hemp FRP was extracted from the literature. The neural network was trained on the extracted dataset, and its performance was evaluated for the experimental results of this study, which demonstrated a close agreement.

This study presents an innovative approach to enhance the flexural capacity of cement-clay interlocking (CCI) brick walls using ferrocement jackets with an expanded wire mesh. The investigation involved 15 CCI brick walls subjected to flexural load testing, exploring various mesh sizes and anchor configurations on single and dual sides. The results revealed that while the primary failure mode involved dry joint opening and subsequent ferrocement debonding in the strengthened walls, effective anchorage mechanisms delayed dry joint opening until debonding occurred. The reinforced walls exhibited improved peak load capacity, notably in dual-sided reinforcement cases. With plastering on both sides and supplemented with anchors, an improvement of up to 221% in flexural capacity was obtained. The study emphasizes the influence of wire mesh size on anchorage effectiveness and its correlation with debonding susceptibility. Additionally, the moment-curvature analysis demonstrated resilient, ductile responses in load-bearing characteristics, with occasional abrupt declines due to ferrocement jacket debonding. Unlike control walls, the strengthened walls exhibited strains exceeding yield thresholds, indicating enhanced structural performance.

The utilization of recycled waste in the production of new concrete raises significant concerns regarding the quality of the resulting concrete. One prominent drawback of recycled aggregate concrete (RAC) is its inferior mechanical properties compared to natural aggregate concrete. In this study, we examine the impact of hemp fiber rope (HFR) confinement on improving the compressive stress-strain behavior of RAC, specifically using recycled brick aggregates from fired-clay solid bricks (RAC-FCSB) as a partial substitute for natural coarse aggregates. Furthermore, we explore and compare the effectiveness of HFR confinement in the form of strips versus fully wrapped confinement. To conduct the experiments, a comprehensive framework was developed, involving a total of 32 cylindrical specimens. The parameters of interest included the configuration of HFR confinement (strips or full wrapping), the number of HFR layers, and the inherent strength of the concrete. The results indicate that HFR strips can significantly enhance the compressive stress-strain response. However, their performance falls short when compared to the fully wrapped HFR confinement. Nonetheless, HFR strips were able to enhance the peak compressive stress and strain of RAC-FCSB up to 204% and 190%, respectively. The second part of the study investigated the performance of existing models of HFR confinement in predicting the peak compressive stress and strain of RAC-FCSB. The deficiencies in existing models were highlighted, and new models based on non-linear regression analysis were proposed to accurately predict the peak compressive stress and strain of HFR-confined RAC-FCSB.

The low cost of cement-clay interlocking (CCI) bricks is an attractive feature, resulting in a wide utilization of CCI bricks in the construction of masonry walls. Despite this, an experimental database on the performance of CCI brick walls is scarce. This study tested ten large masonry walls constructed with CCI bricks in a running bond pattern. Two types of CCI bricks were used to assess the effect of chemical position on the diagonal compressive capacity of walls. Further, different grouts and steel bars were used within the openings in CCI bricks. A combination of grout and steel bars resulted in the optimal improvement of the diagonal compressive strength, whereas up to 110% higher improvement in the diagonal compressive strength was achieved by doubling the compressive strength of grout. Interestingly, the type of bricks did not influence the improvement in the diagonal compressive capacity of CCI brick masonry walls. A regression-based equation was proposed to predict the diagonal compressive capacity of CCI brick walls by including the yield strength of steel bars, the compressive strength of grout, and the diagonal compressive strength of ungrouted walls as explanatory variables. The predicted capacities of CCI brick walls were found to be in close agreement with experimental results.

Each year, an enormous amount of construction waste is produced worldwide. The reuse of construction waste in construction works is a sustainable solution. The present research work utilized recycled brick aggregates in the production of concrete. The resulting concrete exhibited substandard splitting tensile, flexural, and compressive properties. Steel fibers were used to improve these substandard properties of recycled brick aggregate concrete. The volume fractions of 1%, 2%, and 3% for steel fibers were mixed in concrete, whereas recycled brick aggregates were obtained from solid fired-clay bricks, hollow fired-clay bricks, and cement–clay interlocking bricks. The compressive strength was enhanced by up to 35.53% and 66.67% for natural and recycled brick aggregate concrete, respectively. Strengthened flexural specimens demonstrated up to 8765.69% increase in the energy dissipation. Specimens strengthened with steel fibers showed substantially improved splitting tensile, flexural, and compressive responses. Separate equations were proposed to predict the peak compressive strength, strain at peak compressive strength, elastic modulus, and post-peak modulus of recycled brick aggregate concrete. The proposed regression equations were utilized in combination with an existing compressive stress–strain model. A close agreement was observed between experimental and predicted compressive stress–strain curves of recycled brick aggregate concrete.

This study presents an experimental framework with seventeen beams to investigate the impact of loading type, configuration, and through-bolt anchorage on LC-GFRP (Low-Cost Glass-Fiber-Reinforced Polymer) confinement performance. Beams underwent three-point and four-point bending, with LC-GFRP applied in various ways, including U-shaped, side-bonded, and fully wrapped, with and without anchors. The performance of LC-GFRP was compared to CFRP (Carbon-Fiber-Reinforced Polymer) and sisal wraps. LC-GFRP in side-bonded and U-shaped configurations without anchors under three-point bending showed no shear failure, while those under four-point bending without anchors experienced shear failure. With anchors, U-shaped configurations successfully prevented shear failure. The side-bonded, U-shaped, and U-shaped configurations along the full span with anchors demonstrated peak capacity enhancements of 72.11%, 43.66%, and 68.39% higher improvements than the corresponding configurations without anchors, respectively. Wrapping all sides of the beam with LC-GFRP or CFRP prevented shear failure without additional anchors, with complete wrapping being the most efficient method. When anchors were used, significant capacity enhancements were observed. Existing shear strength prediction models were evaluated, highlighting the need for more tailored expressions for LC-GFRP confinement, especially for non-U-shaped configurations.

This study aimed at understanding the awareness and knowledge levels of planning and engineering students and practitioners about the 15-Minute City concept (FMC). The three main objectives were to determine the awareness levels, factors affecting the awareness levels and the knowledge level about FMC. A questionnaire survey was conducted in Lahore, Pakistan, which included questions on the respondents’ demographics, and their awareness and knowledge about FMC. The collected data were analyzed using various statistical analysis techniques to achieve the objectives of the study. The results indicated that a high number of respondents did not have awareness about the FMC concept. Ordinal regression model indicated that type of degree and numbers of seminars attended had a significant influence on the awareness levels. Those having or pursuing planning degrees had higher awareness about FMC than those with engineering degrees. Those who attended more number of seminars on urban and transport planning had higher levels of awareness about FMC as compared to those with lower number of seminars. Civil and Transportation Engineers play an important role in the planning and development of cities, however, they were found to have lower awareness levels. The results of this study can be used to determine how the awareness level of planners and engineers can be increased about more sustainable solutions including FMC.

Excessive volumetric changes associated with shrinkage and non-uniform moisture and heat distribution along long-span girders induce unwanted curvatures. This study aims at investigating both short- and long-term measurements of various quantities involving midspan deflections, tendon strains, longitudinal steel bar strains, concrete strains, and thermal changes in precast-post-tensioned (PCPT) girders. A total of 2 PCPT girders were cast in this study with symmetrical structural and geometrical details. Post-tensioning of the first and second girders was performed on the 28th and 120th days of their casting, respectively. Long-term measurement was performed on the first girder. It was observed that all measured parameters increased swiftly during post-tensioning. During the initial 30 days after post-tensioning, a gradual increase in all parameters was observed, whereas all measured parameters exhibited negligible increase beyond that. A Finite Element Model was generated using ATENA to estimate short-term deflections of PCPT girders during post-tensioning. In general, a good agreement between experimental and analytical midspan deflections was observed.

This study investigated the influence of CFRP composite wrapping techniques on the load–deflection and strain relationships of non-prismatic RC beams. A total of twelve non-prismatic beams with and without openings were tested in the present study. The length of the non-prismatic section was also varied to assess the effect on the behavior and load capacity of non-prismatic beams. The strengthening of beams was performed by using carbon fiber-reinforced polymer (CFRP) composites in the form of individual strips or full wraps. The linear variable differential transducers and strain gauges were installed at the steel bars to observe the load–deflection and strain responses of non-prismatic RC beams, respectively. The cracking behavior of unstrengthened beams was accompanied by excessive flexural and shear cracks. The influence of CFRP strips and full wraps was primarily observed in solid section beams without shear cracks, resulting in enhanced performance. In contrast, hollow section strengthened beams exhibited minor shear cracks alongside the primary flexural cracks within the constant moment region. The absence of shear cracks was reflected in the load–deflection curves of strengthened beams, which demonstrated a ductile behavior. The strengthened beams demonstrated 40% to 70% higher peak loads than control beams, whereas the ultimate deflection was increased up to 524.87% compared to that of the control beams. The improvement in the peak load was more prominent as the length of the non-prismatic section increased. A better improvement in ductility was achieved for the case of CFRP strips in the case of short non-prismatic lengths, whereas the efficiency of CFRP strips was reduced as the length of the non-prismatic section increased. Moreover, the load–strain capacity of CFRP-strengthened non-prismatic RC beams was higher than the control beams.

The urgent need to find green alternatives to cement concrete in order to reduce the consumption of fossil fuels and non-renewable resources that are used to produce cement. This research aims to study the possibility of using volcanic pumice dust (VPD) waste with cement kiln dust (CKD) or Ordinary Portland cement (OPC) to produce alkaline activated green concrete (HAC). VPD was used to improve the mechanical performance, strength, and engineering properties of HAC. CKD and OPC were used as a partial replacement for VPD in different proportions of 0, 5%, 10%, 20%, and 30% by weight. Na2SiO3 and NaOH were used as alkaline activator solutions to realize the alkaline reaction process in geopolymer paste. Workability, compressive strength, and engineering properties, such as bulk density, porosity, and water absorption, were studied. Results of this research indicated that increasing the replacement rates of CKD or OPC decreased slump flow but increased the strength of HAC and enhanced the values of its engineering properties. Geopolymer concrete with OPC and CKD as partial replacement of 30% by weight of VPD achieved an increase of 23% and 8%, respectively, in compressive strength at a test age of 90 days. Meanwhile, 20% VPD replacement by CKD achieved 11% higher compressive strength for the VPD–CKD samples compared with the control mixture. In addition, water absorption rate decreased by 25% and 20%, respectively, compared with the control samples.

Re-use of recycled aggregates in concrete has become a very sustainable solution owing to its environment-friendly and cost-effective nature. Clay bricks are most widely used in construction all over the world. Subsequently, waste generated from the demolition of clay-brick structures is most troublesome. Inherent porosity of bricks compromises the compressive strength of concrete with clay brick aggregates (C-CBA) that has rendered its use in structural concrete for quite some time. With some external clamping pressures, this deficiency can be countered. This study presents an experimental investigation into the use of steel clamps as a strengthening material for C-CBA. Steel clamps are cost-effective, readily available, and very easy to use. C-CBA were tested in two groups depending upon compressive strength: 15 & 35 MPa. Further, 3, 5, and 11 steel clamps were used in each group. Results suggested that steel clamps can effectively be used in enhancing the compressive strength of C-CBA to a level that is acceptable to be used in structural concrete. Increase in peak compressive strength of C-CBA was found to be proportional with the number of steel clamps employed. Three analytical concrete models were used to predict the compressive strength of C-CBA after strengthening. It was concluded that all three analytical models predicted well C-CBA compressive strength for 3-clamp specimens. However, their pre-diction accuracy was highly compromised as the number of steel clamps were increased.

Masonry structures are used in many parts of the world because of their varying benefits of being low-cost, heat insulations, local availability, and skilled labor. Therefore, to investigate the compressive stress-strain behavior and detailed analysis and assessment of masonry structures made of CCI bricks is imperative. Axial compressive results of 10 hollow cement-clay interlocking (CCI) bricks made masonry walls are presented. 10 masonry walls were tested under concentric compressive load in 2 groups. Bricks of each group had different compressive strength. Five walls in each group comprised of 1 control wall (ungrouted), 1 wall grouted with Ordinary Portland Cement (OPC), 1 wall grouted with non-shrink (NS) cement, 1 wall grouted with OPC and strengthened by steel bars, and 1 wall grouted with NS and strengthened with steel bars. Among 5 walls in each group, control wall created the lower bound in terms of the peak load sustained. While the upper bound was created by the wall grouted with NS cement and further strengthened by steel bars. It was found that the addition of grout (irrespective of its type) significantly improved the peak compressive load. However, increase in peak load over that of the control wall was associated to the grout type. Walls grouted with NS cement attained higher peak loads as compared to those grouted with OPC. It was observed that the addition of cement grout does not guarantee a ductile post-peak behavior. Addition of steel bars not only increased the peak loads, but it also improved the post peak behavior. Accuracy of existing compressive load analytical models was assessed, and it was found that none of the analytical models considered were able to predict close approximations. A linearly regressed model is proposed to predict compressive strength of CCI brick masonry walls with good accuracy.

Many masonry structures are constructed with cement clay interlocking brick (CCIB) due to its added benefits. Recent research has demonstrated the vulnerability of brick masonry walls against seismic loading. Various strengthening materials and techniques are extensively used to improve the structural behavior of brick walls. Carbon fiber-reinforced polymer (CFRP) composites are the most popular strengthening material due to their advantages of easy application, lightweight qualities, and superior tensile strength. The current research work aimed to explore the cost-effective solutions and feasibility of CFRP composite-based strengthening techniques to improve the load-bearing capacity of CCIB walls. Various configurations and combinations of strengthening materials were investigated to customize the cost of repair and strengthening. The experimental results indicated that CFRP composites in combination with cement-sand (CS) mortar are an efficient strengthening material to enhance the strength and ultimate deflection of CCIB walls. The ultimate load-bearing capacity and axial deformation of the strengthened CCIB wall (using two layers of CFRP strips and CS mortar of 10 mm thickness) remained 171% and 190% larger than the unstrengthened CCIB wall. The conclusions of this study are expected to enhance the seismic performance of masonry buildings in developing countries. It should be noted that due to the reduced number of tested specimens, the results to be assumed as general considerations need a wider experimental campaign and a large numbers of tests for each strengthening typology.

Recently, hemp-fiber-reinforced polymer (HFRP) composites have been developed to enhance the strength and ductility of normal and lightweight aggregate concrete along with recycled brick aggregate concrete. In addition, both experimental and analytical investigations have been performed to assess the suitability of the existing strength and strain models. However, the theoretical and analytical expressions to predict the stress–strain curves of HFRP-confined concrete were not developed. Therefore, the main objective of this study was to develop analytical expressions to predict the stress–strain curves of HFRP-confined waste brick aggregate concrete. For this purpose, a new experimental framework was conducted to examine the effectiveness of HFRP in improving the mechanical properties of concrete constructed with recycled brick aggregates. Depending on the strength of the concrete, two groups were formed, i.e., Type-1 concrete and Type-2 concrete. A total of sixteen samples were tested. The ultimate compressive strength and strain significantly increased due to HFRP confinement. Improvements of up to 272% and 457% in the ultimate compressive strength and strain were observed due to hemp confinement, respectively. To predict the ultimate compressive strength and strain of HFRP-confined concrete, this study investigated several existing analytical stress–strain models. Some of the strength models resulted in close agreement with experimental results, but none of the models could accurately predict the ultimate confined strain. Nonlinear regression analysis was conducted to propose expressions to predict the ultimate compressive strength and strain of HFRP-confined concrete. The proposed expressions resulted in good agreement with experimental results. An analytical procedure was proposed to predict the stress–strain curves of hemp-confined concrete constructed by partial replacement of natural coarse aggregates by recycled fired-clay brick aggregates. A close agreement was found between the experimental and analytically predicted stress–strain curves.

To date a large number of studies have been carried out on the use of different materials such as concrete, steel, fiber reinforced polymer (FRP) composites, to enhance the strength and ductility of the reinforced concrete (RC) members. Among these materials, concrete and steel are heavy weight, whereas FRP are expensive along with skin problems during handling and installations. In this paper, the efficiency of natural sisal fiber reinforced polymer composites is evaluated on strength and ductility of RC members. The salient features of natural sisal FRPs are low density, higher toughness, acceptable strength properties, reduced irritation to the skin and respiratory system, biodegradable and sustainable since they are natural products. The objectives of this research were twofold. The first was to evaluate the compressive and flexural behavior of small-sized concrete specimens (cylinders and beams) strengthened with natural sisal FRPs, considering different resin matrices, FRP thickness and concrete strengths. Whereas, the second objective was to investigate the strengthening effect of natural sisal FRP strengthening on the flexural response of RC beams. Test results showed that externally bonded natural sisal FRPs are significantly effective to increase the strength and ductility of the concrete members. In general, the experimental results demonstrated a higher increase in the load carrying capacity when the thickness of the sisal FRPs was increased. However, RC beams strengthened by natural sisal FRP, may fail by de-bonding of FRP from the concrete surface. To avoid this failure, a new anchoring system has been proposed and tested to evaluate their performance in preventing the de-bonding of FRP from concrete surface. Based on experimental results, proposed anchoring system was found to be effective to prevent the delamination of natural sisal FRPs from concrete surface.

This study presented the results of an experimental program conducted on a newly proposed Full-scale Precast Post-tensioned Continuous (FPPC) girder for straddle monorail. The investigated FPPC girder represents the actual size, design and construction details for a newly designed monorail transit system (Yellow Line and Pink Line Monorail) in Bangkok, Thailand. The salient features of the newly proposed girder system include lightweight, low-cost, easy and fast construction. The newly proposed FPPC girder is mainly comprised of three reinforced concrete (RC) hollow haunched girders, four piers or supports, two pier segments, four wet joints, and four bearings at each support. The FPPC girder was constructed at the casting yard of Sino-Thai Engineering and Construction Public Company Limited (STECON), Thailand. The FPPC girder was tested under different loading conditions (such as service and ultimate loading conditions). Both service and ultimate loads were applied as two-point loadings. Service load in a monotonic manner was applied on the right exterior span (two-point), middle span (two-point), and on the left exterior span and middle span (four-point). Meanwhile, the ultimate load in a monotonic manner was applied only on the left exterior and middle span as a four-point loading scheme. The test results indicate that the behaviour of the FPPC girder under service load conditions is elastic. Further, cracking of the concrete was not observed at any location. The observed maximum deflections under service load conditions were less than the permissible limits at all locations. Further, the maximum ultimate load-carrying capacity was observed to be much greater than the design load under ultimate loading conditions. This is an indication that the design details and construction procedure of FPPC girder are appropriate and further that this system could be used effectively to construct straddle monorail transit systems. Finite element analysis of FPPC monorail bridge girder was also performed by using a computer program ATENA which is a computational tool for nonlinear engineering analysis of bridges and culverts. The finite element analysis results indicate that the computer program ATENA is well capable to predict the ultimate load carrying capacity, displacement and cracking patterns of FPPC girder.

Given the excessive demolition of structures each year, the issues related to the generated structural waste are striking. Bricks being a major constituent in the construction industry, also hold a significant proportion of the construction waste generated annually. The reuse of this brick waste in new constructions is an optimal solution considering cost-effectiveness and sustainability. However, the problems related to the substandard peak stress and ultimate strain of concrete constructed with recycled brick aggregates (CRAs) limit its use in non-structural applications. The present study intends to improve the unsatisfactory mechanical characteristics of CRAs by utilizing low-cost glass fiber chopped strand mat (FCSM) sheets. The efficacy of FCSM sheets was assessed by wrapping them around CRA specimens constructed with different concrete strengths. A remarkable increase in the peak compressive stress and the ultimate strain of the CRA specimens were observed. For low, medium, and high strength CRAs, the ultimate strain improved by up to 320%, 308%, and 294%, respectively, as compared to the respective control specimens. Several existing analytical models were utilized to predict the peak compressive stress and ultimate strain of the CRAs strengthened using FCSM sheets. None of the considered models reproduced experimental results accurately. Therefore, equations were formulated using regression predicting the peak stress and ultimate strain of the CRAs confined with FCSM sheets. The predicted values were found to correlate well with the experimental values.

The present study focused on the development and application of two computer numerical models, namely, a seepage model developed using SEEP/W software and a groundwater model developed using Visual MODFLOW software. The seepage model was applied to a 38 km length of the tail reach of the Trimmu–Sidhnai (T-S) link canal passing through a severely waterlogged area of 32,000 ha, with a water table within 0–1.5 m from the ground surface; this was to quantify the canal seepage under the present condition (without any intervention) and with the interventions of a concrete lining of the complete prism of the T-S link canal and concrete side protection of the T-S link canal, with the canal bed unlined. The groundwater model evaluated the effectiveness of three waterlogging management interventions, which included: (i) the rehabilitation of the 43 existing drainage tube wells, (ii) the rehabilitation of the existing surface drains, and (iii) a combination of the rehabilitation of the 43 existing drainage tube wells and the rehabilitation of the existing surface drains. The seepage modeling revealed that the concrete lining intervention can reduce 50% of the seepage of the T-S link canal, whereas the concrete side protection intervention can reduce only 21% of the canal seepage. The groundwater modeling revealed that the waterlogging management intervention of the rehabilitation of the 43 drainage tube wells and surface drains can lower the groundwater level from 139.2 to 138.3 m (0.9 m drop), resulting in the mitigation of waterlogging in 45% (14,400 ha) of the severely waterlogged area. The present study recommends that complete concrete lining of the T-S link canal has a huge potential to reduce seepage from the canal, and the combination of the rehabilitation of the 43 drainage tube wells and surface drains also offers a great potential for controlling waterlogging. This intervention can also be considered to mitigate waterlogging from the severely waterlogged area. Cost-effectiveness analysis of the concrete lining of the T-S link canal, the rehabilitation of the 43 existing drainage tube wells, and the rehabilitation of the existing surface drains need to be performed for decision-making and selection of the most cost-effective intervention for implementation. A study needs to be conducted for the development and evaluation of economical and socio-technically feasible and acceptable preventive waterlogging management interventions, including the improved management of irrigation systems, improved irrigation management practices at the farm, improved conjunctive management of surface and groundwater, and improved management of drainage systems at the primary, secondary, and tertiary canal command levels.

Intrinsically, lightweight aggregate concrete (LWAC) suffers from the low compressive strength and deformation capacity. This restricts the use of LWAC mainly to non-structural applications. Several studies have highlighted the potential of synthetic fiber-reinforced polymer (FRP) jackets for improving the substandard properties of the LWAC. However, the high costs associated with FRP jackets are generally a concern. This study identifies hemp fiber-reinforced rope polymer (FRRP) wraps as a potential alternative to the synthetic FRP jackets. The salient features of hemp FRRP include its low cost and easy availability. Therefore, the main question that needs to be answered is: can hemp FRRP strengthen LWAC as a low-cost alternative to synthetic FRP jackets? To quantitatively explain the effects of lightweight aggregates on concrete compressive strength, 24 concrete cylinders were tested in three groups. Group 1, 2, and 3 cylinders comprised 0, 50, and 100% of lightweight aggregates as natural aggregate replacements. The peak stress of the concrete was reduced by 34% and 49% in the presence of 50% and 100% lightweight aggregates, respectively. It was concluded that a single layer of hemp FRRP on Group 2 cylinders (i.e., 50% aggregate replacement) was sufficient to enhance the peak stress to the same level as that of the control cylinder in Group 1 (i.e., fabricated using natural aggregates only). At the same time, it took two layers of external FRRP on Group 3 cylinders to achieve the same strength. A positive correlation between the peak stress of the LWAC and the number of hemp FRRP layers was observed. Nonetheless, Group 1 and 3 cylinders formed the upper and lower bounds in terms of peak stress for the same level of confinement. Further to the interest, three layers of hemp FRRP shifted brittle compressive stress–strain response to a bi-linear response for all amounts of lightweight aggregates. Several existing analytical peak stress models were assessed in predicting the experimental results. From the results, it was inferred that none of these models predicted the compressive strength of all three groups of cylinders consistently.

Recycled aggregate concrete (RAC) is more sustainable, eco-friendly, and cost-effective as compared to natural aggregate concrete (NAC). Among recycled aggregates (RAs), clay brick aggregate (CBA) has the potential of being the most widely used RAs because of the considerable amount of clay brick waste generated in many countries. The compressive behavior and mechanical properties of RAC with CBA are highly influenced by the mechanical properties of bricks. The stiffness and compressive strength of RAC with CBA are reported marginally lower than the natural aggregate concrete (NAC). In the past, different types of fiber reinforced polymer (FRP) composites such as carbon FRP, glass FRP, and aramid FRP have been investigated to enhance the strength and stiffness of the RAC with CBA. However, the behavior of hybrid FRP confined RAC with CBA is not yet clear. In this study, the performance of a new, low-cost and high-performance hybrid composite to enhance the strength and stiffness of the RAC with CBA is investigated. Hybrid composite is developed by using natural Basalt fiber and E-glass fibers (Chopped Strand Mat) along with the use of high-performance polyester resin. Three types of bricks (having different strength and water absorption) were used to produce CBA. Other research parameters included were the strength of RAC with CBA and the number of layers of hybrid basalt/E-glass fiber reinforced polymer (BE-FRP) composite. A total number of 36 concrete cylinders (12 un-confined and 24 confined with BE-FRP) were tested under pure axial compressions. The results indicate that the BE-FRP composites are highly suitable to enhance strength, stiffness, and ductility of the RAC with CBA. Also, there was found a significant increase in strength and ductility with an increase in the confinement level. In the end, the efficiency of existing strength and stain models was assessed to predict the ultimate strength and strain of the BE-FRP confined RAC with BAC.

Full-scale testing of multiple span girders is scarce in the literature, often related to the complexity of loading setup and time constraints. The importance of full-scale tests is manifested in the fact that useful information regarding failure mechanisms can be obtained. In addition, important guidelines can be established for structural designers. Further, results from full-scale tests can help establish constitutive laws for various mechanisms involved in the response of actual structures. The structural performance of individual members can be assessed by monitoring their strains at service and ultimate loads. This study presents a comparison of experimentally monitored strains on longitudinal steel bars, stirrups, and prestressing tendons embedded in single and multi-span full-scale precast pre-tensioned girders. These girders were constructed and detailed to simulate the response of newly proposed straddle-type monorail girders. Single-span girders were tested under monotonic two-point service and ultimate loads, whereas multi-span girders were tested under both two- and four-point service and ultimate load. It was revealed that longitudinal steel and prestressing tendon strains monitored within single-span girders at service and ultimate loads were significantly higher than those recorded at corresponding locations in multi-span girders.

Salient features of lightweight aggregate concrete (LAC) include noticeable fire resistance, high strength-to-weight ratio, and low magnitude of dead loads. Further, LAC has a low cost, eases construction practices, and possesses an environment-friendly nature. On the downside, LAC has substandard mechanical properties in comparison to normal aggregate concrete. Natural fiber-reinforced polymers (FRPs) have shown their potential in ameliorating the mechanical properties of natural aggregate concrete. So far, no study has been conducted to assess the efficacy of hemp rope confinement to strengthen lightweight aggregate concrete especially comprising rectilinear sections. This study aimed to overcome the substandard nature of LAC. A low-cost, sustainable, and environmentally green solution in the form of natural hemp rope layers is proposed. Twenty-four square concrete specimens were tested in three groups depending upon the presence and quantity of lightweight aggregates. It was found that concrete constructed with lightweight aggregates demonstrated lower ultimate compressive strength and strain as compared to normal aggregate concrete. Hemp rope-confined LAC showed enhanced ultimate compressive strength and strain. This enhancement was found to increase with the number of hemp rope layers. Several existing ultimate stress models were assessed to predict the ultimate compressive strength of the hemp rope-confined specimens. Only a single model was able to predict the ultimate compressive strength of the hemp rope-confined specimens with reasonable accuracy.

In this study, a total of 24 cylindrical concrete specimens were constructed and strengthened using locally available and Low-Cost Glass Fiber Reinforced Polymer (LC-GFRPs) composites. The considered research parameters were the strength of un-confined concrete (5 MPa and 15 MPa) and the confinement level (one, two, and three layers of LC-GFRP). The specimens were tested to failure under pure axial compression. The results indicate that LC-GFRPs are very beneficial to modify the ultimate load-carrying capacity and ductility of the confined concrete. In the end, the existing expressions, developed mainly for special purpose traditional FRPs to estimate the ultimate strength and strain of the confined concrete, were utilized to assess their application to the LC-GFRP confined concrete. It was found that all considered models are well capable to estimate the ultimate strength of LC-GFRP confined concrete but those models were not able to accurately predict the ultimate strain of the LC-GFRP confined concrete.

The aim of this research work is to investigate the efficiency of newly developed Natural Fiber Rope Reinforced Polymer (NFRRP) composites to enhance the shear strength of reinforced concrete (RC) beams. Two types of NFRRP composites were made using low-cost hemp and cotton fiber ropes. The effectiveness of this NFRRP confinement in increasing the shear, energy dissipation, and deformation capacities of concrete beams was studied. The effect of these natural fiber ropes with different configurations on beams was investigated. The responses of seven RC beams with different spacing arrangements of natural fiber ropes were evaluated in terms of shear enhancement, deflection, energy dissipation capacity, effect of strengthening configuration, rope types, and ultimate failure modes. The NFRRP composites exceptionally enhanced the load carrying abilities, energy dissipation, and deformation capabilities of RC beams as compared to the control beam. The ultimate load carrying capacities of natural hemp and cotton Fiber Rope Reinforced Polymer (FRRP) composite confined beams were found to be 63% and 56% higher than that of the control beam, respectively. Thus, the shear strengthening of RC beams using natural fiber ropes is found to be an effective technique. Finite Element Analysis was also carried out by using the Advanced Tool for Engineering Nonlinear Analysis (ATENA) software. The analysis results compare favorably with the tests’ results.

Reinforced concrete is used in the construction of bridges, buildings, retaining walls, roads, and other engineered structures. Due to seismic activities, a lot of structures develop seismic cracks. The rehabilitation of such structures is necessary for public safety. The overall aim of this research study was to produce a high-performance hybrid fiber-reinforced concrete (HPHFRC) with enhanced properties as compared to plain high-performance concrete and high-performance fiber-reinforced concrete (HPFRC) for the rehabilitation of bridges and buildings. Kevlar fibers (KF) and glass fibers (GF) with lengths of 35 mm and 25 mm, respectively, were added and hybridized to 1.5% by mass of cement to create hybrid fiber-reinforced concrete mixes. Eight mixes were cast in total. The compressive strength (f′c), flexural strength (fr), splitting tensile strength (fs), and other mechanical properties, i.e., energy absorption and toughness index values, were enhanced in HPHFRC as compared to CM and HPFRC. It was found that the concrete hybridized with 0.75% KF and 0.75% GF (HF-G 0.75 K 0.75) had the most enhanced overall mechanical properties, illustrating its potential to be utilized in the rehabilitation of bridges and structures.

Over the last two decades, considerable attention has been devoted to the strengthening of sub-standard flat-slab constructions. With the evolution of composite materials and an increasing emphasis on the economical and sustainable use of natural fibers, many researchers have utilized them in the strengthening of flat flabs mitigating punching failures. This study aims at investigating and comparing the behavior of flat slabs strengthened with post-installed composite and natural reinforcements. An experimental program was devised consisting of eight flat-slab specimens. One specimen was tested in as-built condition to provide a reference. The remaining specimens were strengthened with Carbon Fiber-Reinforced Polymer (CFRP), Aramid Fiber-Reinforced Polymer (AFRP), and sisal rods. The pattern of post-installed rods was varied as single line, double line, and star shapes around the column. The results indicated that the single-line pattern could only enhance the maximum sustained load by up to 6% compared to that of the reference specimen. On the contrary, double line and star shape configurations resulted in a substantial increase in the maximum sustained load. An analytical assessment of ACI 318-19 provisions resulted in an over-estimation of the shear strengths of CFRP- and AFRP-strengthened slabs. Furthermore, the same provisions led to lower yields than experimental shear strengths for sisal-strengthened slabs.

Buildings located in coastal regions are prone to tsunami dangers, which often carry debris in the form of shipping containers and boats. This paper presents an approach for the design of fender structures to minimize debris impacts on buildings. The impact of shipping containers, which are categorized as large debris, is considered in the study. Since the weights of shipping containers are standardized, the impact energy can be related to other debris. For a fender structure, cone-type rubber fenders are used to resist the impact of the shipping container. Various fender reactions are considered as parameters to study the efficiency of the fenders. The displacement-controlled nonlinear static analysis is carried out to determine the building capacity. The energy approach for shipping container impact is used to evaluate the resistance of the building. Capacity curves, energy absorptions, inter-story drift ratios of the buildings with and without a fender structure, and the efficiency of the fender are presented. The buildings with a fender structure can absorb the energy from the impact of a loaded shipping container. Conversely, the building without a fender structure cannot resist the impact of a loaded shipping container. From the obtained results, a recommendation is given for buildings with a fender structure. The hydrodynamic force on the fender structure is transferred to the main building through the fender. Hence, the yield force of the fenders affects the performance of the main building that must be considered in the design.

Fiber-reinforced concrete (FRC) is a competitive solution for the durability of reinforced structures. This paper aims to observe the moment redistribution behavior occurring due to flexural and shear loading in Glass Fiber-Reinforced Polymer- (GFRP) reinforced continuous concrete beams. A rectangular cross-section was adopted in this study with dimensions of 200 mm in width and 300 mm in depth with a constant shear span-to-depth ratio of 3. The reinforcement ratio for the top and bottom were equal at sagging and hogging moment regions. A finite element model was created using Analysis System (ANSYS) and validated with the existing experimental results in the literature review. Based on the literature review, the parametric study was conducted on twelve beam specimens to evaluate the influence of concrete compressive strength, transversal GFRP stirrups ratio, and longitudinal reinforcement ratio on the redistribution of the moment in beams. Several codes and guidelines adopted different analytical models. The Canadian Standards Association (CSA) S806 adopted the modified compression field theory in predicting the shear capacity of the simply supported beams. Recently, various researchers encountered several factors and modifications to account for concrete contribution, longitudinal, and transverse reinforcement. A comparison between the predicting shear capacity of the generated finite element model, the analytical model, and the existing data from the literature was performed. The generated finite element model showed a good agreement with the experimental results, while the beam specimens failed in shear after undergoing significant moment redistribution from hogging to sagging moment region. The moment distribution observed about 21.5% from FEM of beam specimen GN-1.2-0.48-d, while the experimental results achieved 24% at failure load. For high strength concrete presented in beam specimen GH-1.2-0.63-d, the result showed about 20.2% moment distribution, compared to that achieved experimentally of 23% at failure load.

An experimental program was conducted to ascertain the efficiency of Carbon Fiber Reinforced Polymer (CFRP) in enhancing the flexural response of hollow section reinforced concrete (RC) beams. Nine beams were tested under four-point bending in three groups. Beams were categorized to reflect the presence or configuration of the CFRP sheet. Each group consisted of three beams: one with a solid section, one with a square 50×50 mm × mm opening and 1 with 100×100 mm × mm opening. Beams in 1st group were tested in as-built conditions. Beams in the 2nd group were strengthened with a single CFRP sheet bonded to their bottom sides. Configuration of CFRP sheet was altered to U-shape applied to the tension side of 3rd group beams. The inclusion of openings, regardless of their size, did not result in degradation of ultimate load and corresponding deflections. However, cracking loads were found to decline as the opening size increased. Regardless of the opening size and CFRP configuration, ultimate loads of beams increased with the application of CFRP. However, this improvement was limited to the debonding and rupture of CFRP in group 2 and 3 beams, respectively. A comparison in the behavior of group 2 and 3 beams revealed that the application of the U-shape CFRP sheet yielded better flexural performance in comparison with the flat-CFRP sheet bonded to the bottom of beams. In the end, In order to further evaluate the economic and performance benefits of these beams, the cost-benefit analysis was also performed. The analysis showed that the feasibility of the hollow section RC beams is more than the solid section RC beams.

In the past, fiber-reinforced polymer (FRP) composites have been extensively used to modify the structural response of masonry brick walls. The promising advantages of FRP composites are easy application, lightweight, and very high tensile strength. However, FRP composites are very expensive, and their availability is an issue, especially in developing countries. The use of bricks is widespread in developing countries due to their low price and easy availability. Recent earthquakes and research results have demonstrated the vulnerability of existing masonry structures. In this study, we aimed to investigate the use of low-cost and readily available strengthening materials, i.e., cement-sand mortar and wire mesh, to enhance the flexural capacity of cement-clay interlocking brick (CCIB) masonry walls. The proposed strengthening materials were applied in different configurations and thicknesses. The experimental results indicated that using CS mortar and wire mesh is promising to enhance the flexural capacity of CCIB masonry walls. The flexural capacity and energy absorption capacity of the CCIB masonry wall (strengthened with 20 mm thick CS mortar and three layers of wire mesh) were 87% and 46% higher than the reference CCIB masonry wall. The results of this study can be used to improve the performance of masonry structures against earthquakes in the developing regions.

Cement–clay Interlocking Hollow Brick Masonry (CCIHBM) walls are characterized by poor mechanical properties of bricks and mortar. Their performance is observed to be unsatisfactory under both gravity and seismic loads. There is an urgent need to develop sustainable, environmentally friendly, and low-cost strengthening materials to alter the structural behaviour of brick masonry walls in terms of strength and ductility. The results of an experimental investigation conducted on the diagonal compressive response of CCIHBM walls are presented in this study. In this experimental study, a total of six CCIHBM walls were constructed using cement–clay interlocking hollow bricks. One was tested as a control or reference wall, whereas the remaining walls were strengthened using cement mortar. In some walls, the cement mortar was also combined with the wire mesh. The research parameters included the type of Ordinary Portland Cement (OPC) (Type 1 and Type 2), thickness of cement mortar (10 mm and 20 mm), and layers of wire mesh (one and three layers). The experimental results indicate that control or unstrengthened CCIHBM walls failed in a very brittle manner at a very low ultimate load and deformation. The control CCIHBM wall, i.e., W-CON, failed at an ultimate load of 247 kN, and corresponding deflection was 1.8 mm. The strength and ductility of cement mortar and wire mesh-strengthened walls were found to be higher than the reference CCIHBM wall. For example, the ultimate load and deformation of cement-mortar-strengthened wall were found to be 143% and 233% higher than the control wall, respectively. Additionally, the ultimate failure modes of cement mortar and wire mesh strengthened were observed as ductile as compared to the brittle failure of reference wall or unstrengthened CCIHBM wall, which increased by 66% and 150% as compared with the control wall.

Experimental evidence have proved that punching shear capacity of flat slabs deteriorate with the presence of openings located within the critical perimeter around columns. It is understood that this deterioration varies inversely with the distance of openings from column’s face. However, effect of the shape of openings on punching shear capacity is not well known. This study presents experimental results of 14 flat specimens to investigate the effects of the number (2 and 4), shape (circular, square, and rectangular), and location (1 and 4 times of slab’s thickness from column’s face) of openings on punching shear strength. It was found that circular openings had least influence on punching capacity followed by square and rectangular openings, respectively. Further, placing openings at a distance of four times the slab’s thickness from column’s face had minimal impact on punching capacity. Further, increasing the number of openings from 2 to 4 substantially reduced the punching capacity. An effort was made to predict the punching capacities of all specimens using the descriptive equations of ACI 318-19 and Eurocode 2. Mean of the ratio of experimental to analytical results and standard deviation of ACI equations were found to be more accurate than those of Eurocode 2 predictions.

Experimental and finite element analysis results of reinforced concrete beams under monotonic loading were presented in this study. In the experimental program, one beam was tested in an as-built condition. The other two beams were strengthened using natural hybrid FRP layers in different configurations. The natural hybrid FRP composite was developed by using natural jute FRP and basalt FRP. One of the most appealing advantages of natural fiber is its beneficial impact on the environment, which is necessary for the sustainability recognition as an alternative to synthetic FRP. The hybrid FRP was applied to the bottom concrete surface in one beam, while a U-shaped strengthening pattern was adopted for the other beam. The flexural behavior of each beam was assessed through strain measurements. Each beam was incorporated with conventional strain gages, as well as the Brillouin Optical Time Domain Analysis (BOTDA) technique. BOTDA has its exclusive advantages due to its simple system architecture, easy implementation, measurement speed, and cross-sensitivity. The experimental results revealed that the beam strengthened with the U-shaped hybrid FRP composite pattern had a better flexural response than the other counterpart beams did both in terms of peak loads and maximum bottom longitudinal steel bar strains. Beams B-01 and B-02 exhibited 20.5% and 28.4% higher energy dissipation capacities than the control beam did, respectively. The ultimate failure of the control beam was mainly due to the flexural cracks at very low loads, whereas the ultimate failure mode of FRP composite-strengthened beams was due to the rupture of the hybrid FRP composite. Further, strain measurements using BOTDA exhibited similar patterns as conventional strain gage measurements did. However, it was concluded that BOTDA measurements were substantially influenced by the bottom flexural cracks, ultimately resulting in shorter strain records than those of conventional strain gages. Nonlinear structural analysis of the beams was performed using the computer program ATENA. The analytical results for the control beam specimen showed a close match with the corresponding experimental results mainly in terms of maximum deflection. However, the analytical peak load was slightly higher than the corresponding experimental value.

This research investigates the behavior of square concrete columns externally wrapped by low-cost and easily available fiber rope reinforced polymer (FRRP) composites. This study mainly aims to explore the axial stress-strain relationships of FRRP-confined square columns. Another objective is to assess suitable predictive models for the ultimate strength and strain of FRRP-confined square columns. A total of 60 square concrete columns were cast, strengthened, and tested under compression. The parameters were the corner radii of square columns (0, 13, and 26 mm) and different materials of FRRP composites (polyester, hemp, and cotton FRRP composites). The strength and deformability of FRRP-confined specimens were observed to be higher than the unconfined specimens. It was observed that strength gains of FRRP-confined concrete columns and corner radii were directly proportional. The accuracy of ultimate strength and strain models developed for synthetic FRRP-confined square columns was assessed using the test results of this study, showing the need for the development of improved predictive models for FRRP-confined square columns. Newly developed unified models were found to be accurate in predicting the ultimate strength and strain of FRRP-confined columns.

The results of an experimental program on shear-strengthening of flat slabs using Glass Fiber Reinforced Polymer (GFRP) rods are presented. A total of seven specimens were tested under an upward concentric monotonic loading until failure. One specimen served as a control and was tested without any modification. The remaining six specimens were strengthened with post-installed GFRP rods in single (SG), double (DB), and radial (RD) patterns within shear critical parameters around the centric column. The results of this experimental study suggest that GFRP rods are capable of enhancing both the peak load and deformation capacity. Furthermore, brittle failure associated with punching shear failure was successfully avoided by all strengthening patterns. Of all of the patterns, the RD pattern resulted in maximum peak load increase and corresponding deformation capacity while the lowest bound was created by the SG pattern. The results suggested that SG, DB and RD patterns enhanced ultimate loads up to 9.1, 11.3 and 15.7% while corresponding deflections increased up to 109, 136 and 154%. Strain measurement on flexural reinforcement suggested that all strengthened specimens were able to withstand higher longitudinal strains than yield. It was further shown that reducing the spacing between the GFRP rods efficiently enhanced peak loads, nevertheless, neither this change was proportional, nor did it result in an enhanced energy dissipation capacity. In the end, recommendations of American Concrete Institute (ACI) for the shear strength of two-way systems were modified to incorporate the contributions from GFRP rods. The results indicate that the proposed analytical approach provides an excellent match with the experimental results.

The strengthening and rehabilitation of concrete members is an important issue which arises worldwide. Carbon, aramid and glass fiber reinforced polymer (FRP) composites are mainly used for strengthening and rehabilitation. However, its use is limited on a small scale because of its high price, lack of availability and environmental impacts. The solution of this issue gives rise to the use of locally available natural fibers and low-cost synthetic fibers. This paper presents the experimental and analytical results of circular and square concrete columns confined with jute−polyester hybrid FRP composites. The main objective of this study is to evaluate the viability and performance of concrete confined with the hybridization of jute and polyester (FRP) composite sheets to utilize its superior properties. A novel hybrid technique has been applied for the wrapping of fiber sheets. The fiber sheets were applied in such a way that a uniform bond between the inner and outer layer was achieved. A total of 32 plain, standard size circular and square concrete specimens, externally wrapped with a jute−polyester FRP (JPFRP) composite, were tested under monotonic axial compressive loads. The result shows that JPFRP confinement increased the strength, strain and ductility index ranged between 1.24 and 2.61, 1.38 and 8.97, and 4.94 and 26.5 times the un-jacketed specimen, respectively. Furthermore, the wrapping has a significant effect on the low-strength specimens, having a circular cross-section. For high strength specimens, the post-peak stress-strain behavior was dominated by the outer polyester jacket because of its large rupture strain. Additionally, the test results were used to evaluate the existing strength-strain models derived for conventional FRPs. The models predicted values either underestimating or overestimating the compressive strength and strain of JPFRP-confined specimens. However, the strength models performed better than the strain models. The JPFRP wrapping significantly enhanced the strength, fracture energy, ductility index, and post-peak response. Therefore, JPFRP confinement can be used for a small-scale application, where little strength and high ductility is demanded. Moreover, it can be used to prevent the peeling of the concrete cover and moisture penetration into the concrete.

AbstractThis paper presents the finite element analysis conducted on SFRP strengthened reinforced concrete (RC) deep beams. The analysis variables included SFRP material (glass and carbon), SFRP thickness (3 mm and 5 mm), SFRP configuration and strength of concrete. The externally applied SFRP technique is significantly effective to enhance the ultimate load carrying capacity of RC deep beams. In the finite element analysis, realistic material constitutive laws were utilized which were capable of accounting for the non-linear behavior of materials. The finite element analysis was performed using computer software WCOMD. In the analysis, two dimensional eight-node reinforced concrete planar elements for concrete and planar elements with elastic-brittle behavior for SFRP were used to simulate the physical models. The concept of smeared cracking in concrete and steel was adopted over the element. The calculated finite element results are found to be in good agreement with the experimental results and to capture the structural response of both un-strengthened and SFRP strengthened RC deep beams. A comparison between the finite element results and experimental data proved the validity of the finite element models. Further, the finite element models were utilized to investigate the behavior of RC deep beams strengthened with different directions of SFRP Strips (vertical and horizontal). The vertical SFRP strips are found to be more effective than horizontal ones.