Search results
1 – 10 of 490To make full use of the tensile strength of near surface mounting (NSM) pasted carbon fiber reinforced plastics (CFRP) strips and further increase the flexural bearing capacity…
Abstract
Purpose
To make full use of the tensile strength of near surface mounting (NSM) pasted carbon fiber reinforced plastics (CFRP) strips and further increase the flexural bearing capacity and flexibility of reinforced concrete (RC) beams, a new composite reinforcement method using ultra-high performance concrete (UHPC) layer in the compression zone of RC beams is submitted based on embedding CFRP strips in the tension zone of RC beams. This paper aims to discuss the aforementioned points.
Design/methodology/approach
The experimental beam was simulated by ABAQUS, and compared with the experimental results, the validity of the finite element model was verified. On this basis, the reinforced RC beam is used as the control beam, and parameters such as the CFRP strip number, UHPC layer thickness, steel bar ratio and concrete strength are studied through the verified model. In addition, the numerical calculation results of yield strength, ultimate strength, failure deflection and flexibility are also given.
Findings
The flexural bearing capacity of RC beams supported by the new method is 132.3% higher than that of unreinforced beams, and 7.8% higher than that of RC beams supported only with CFRP strips. The deflection flexibility coefficient of the new reinforced RC beam is 8.06, which is higher than that of the unreinforced beam and the reinforced concrete beam with only CFRP strips embedded in the tension zone.
Originality/value
In this paper, a new reinforcement method is submitted, and the effects of various parameters on the ultimate bearing capacity and flexibility of reinforced RC beams are analyzed by the finite element numerical simulation. Finally, the effectiveness of the new method is verified by the analytical formula.
Details
Keywords
Aya Qatawna, Rabab Allouzi and Samih Qaqish
The primary objective of this study is to produce one-way slabs made of LWFC with low density and sufficient compressive strength suitable for structural purpose then investigate…
Abstract
Purpose
The primary objective of this study is to produce one-way slabs made of LWFC with low density and sufficient compressive strength suitable for structural purpose then investigate their flexural behavior under various types of reinforcement and thickness of the slab and the influence of addition of PP fibers reinforcement on the mechanical behavior of reinforced concrete slabs. The specimens were tested using four-point loading. The results concerning load capacity, deflection and failure mode and crack pattern for each specimen were obtained. Also, an analytical investigation of PP fiber and GFG contribution on the flexural behavior of foamed concrete slabs is studied to investigate the significant role of PP fiber on the stress distribution in reinforced foam concrete and predict the flexural moment capacity.
Design/methodology/approach
The materials used in this study are cement, fine aggregate (sand), water, PP fibers, foaming agent, chemical additives if required, steel reinforcing rebars and glass fiber grid. The combination of these constituent materials will be used to produce foamed concrete in this research Then this study will present the experimental program of one-way foamed concrete slabs including slabs reinforced with GFR grids and another with steel reinforcements. The slabs will be tested in the laboratory under static loading conditions to investigate their ultimate capacities. The flexural behavior is to the interest of the slabs reinforced with GFR grids reinforcements in comparison with that of one with steel reinforcing rebars. Three groups are considered. (1) Group I: two slabs of PP fiber foamed concrete with minimum required reinforcements. (2) Group II: two slabs of PP fiber foamed concrete with glass fiber grids. (3) Group III: two slabs of PP fiber foamed concrete with the minimum required reinforcements and glass fiber grids.
Findings
The experimental results proved the effectiveness and efficiency of this the new system in producing a low density of concrete below 1900 kg/m3 had a corresponding strength of about 17 MPa at least. Besides, the presence of PP fibers had a noticeable improvement on the flexural strength values for all the examined slabs. It was found that the specimens reinforced with steel reinforcement mesh carried higher flexural capacity compared to these reinforced with GFG only. The specimens reinforced with GFG exhibited the lowest flexural capacity due to GFG separation from the concrete substrate. Also, an analytical investigation to predict the flexural strength of all tested specimens was carried out. The analytical results were agreed with the experimental results. Therefore, LWFC can be used as a substitute lightweight concrete material for the production of structural concrete applications in the construction industries today.
Research limitations/implications
Foamed concrete is a wide field to discuss. To achieve the objectives of the project, the study is focused on the foamed concrete with the following limitations: (1) because the aim of this research is to produce foamed concrete suitable for structural purposes, it is decided to produce mixes within the density range 1300–1900 kg/m3. (2) Simply-supported slabs are of considered. (3) This study also looks out by using GFR and without it.
Originality/value
The main objectives of this study were producing structural foamed concrete slabs and investigate their flexural response for residential uses.
Details
Keywords
Nagat Zalhaf, Mariam Ghazy, Metwali Abdelatty and Mohamed Hamed Zakaria
Even though it is widely used, reinforced concrete (RC) is susceptible to damage from various environmental factors. The hazard of a fire attack is particularly severe because it…
Abstract
Purpose
Even though it is widely used, reinforced concrete (RC) is susceptible to damage from various environmental factors. The hazard of a fire attack is particularly severe because it may cause the whole structure to collapse. Furthermore, repairing and strengthening existing structures with high-performance concrete (HPC) has become essential from both technical and financial points of view. In particular, studying the postfire behavior of HPC with normal strength concrete substrate requires experimental and numerical investigations. Accordingly, this study aims to numerically investigate the post-fire behavior of reinforced composite RC slabs.
Design/methodology/approach
Consequently, in this study, a numerical analysis was carried out to ascertain the flexural behavior of simply supported RC slabs strengthened with HPC and exposed to a particularly high temperature of 600°C for 2 h. This behavior was investigated and analyzed in the presence of a number of parameters, such as HPC types (fiber-reinforced, 0.5% steel, polypropylene fibers [PPF], hybrid fibers), strengthening side (tension or compression), strengthening layer thickness, slab thickness, boundary conditions, reinforcement ratio and yield strength of reinforcement.
Findings
The results showed that traction-separation and full-bond models can achieve accuracy compared with experimental results. Also, the fiber type significantly affects the postfire performance of RC slab strengthened with HPC, where the inclusion of hybrid fiber recorded the highest ultimate load. While adding PPF to HPC showed a rapid decrease in the load-deflection curve after reaching the ultimate load.
Originality/value
The proposed model accurately predicted the thermomechanical behavior of RC slabs strengthened with HPC after being exposed to the fire regarding load-deflection response, crack pattern and failure mode. Moreover, the considered independent parametric variables significantly affect the composite slabs’ behavior.
Details
Keywords
Long Liu, Lifeng Wang and Ziwang Xiao
The combination of an Engineered Cementitious Composite (ECC) layer and steel plate to reinforce RC beams (ESRB) is a new strengthening method. The ESRB was proposed based on the…
Abstract
Purpose
The combination of an Engineered Cementitious Composite (ECC) layer and steel plate to reinforce RC beams (ESRB) is a new strengthening method. The ESRB was proposed based on the steel plate at the bottom of RC beams, aiming to solve the problem of over-reinforced RC beams and improve the bearing capacity of RC beams without affecting their ductility.
Design/methodology/approach
In this paper, the finite element model of ESRB was established by ABAQUS. The results were compared with the experimental results of ESRB in previous studies and the reliability of the finite element model was verified. On this basis, parameters such as the width of the steel plate, thickness of the ECC layer, damage degree of the original beam and cross-sectional area of longitudinal tensile rebar were analyzed by the verified finite element model. Based on the load–deflection curve of ESRB, ESRB was discussed in terms of ultimate bearing capacity and ductility.
Findings
The results demonstrate that when the width of the steel plate increases, the ultimate load of ESRB increases to 133.22 kN by 11.58% as well as the ductility index increases to 2.39. With the increase of the damage degree of the original beam, the ultimate load of ESRB decreases by 23.7%–91.09 kN and the ductility index decreases to 1.90. With the enhancement of the cross-sectional area of longitudinal tensile rebar, the ultimate bearing capacity of ESRB increases to 126.75 kN by 6.2% and the ductility index elevates to 2.30. Finally, a calculation model for predicting the flexural capacity of ESRB is proposed. The calculated results of the model are in line with the experimental results.
Originality/value
Based on the comparative analysis of the test results and numerical simulation results of 11 test beams, this investigation verified the accuracy and reliability of the finite element simulation from the aspects of load–deflection curve, characteristic load and failure mode. Furthermore, based on load–deflection curve, the effects of steel plate width, ECC layer thickness, damage degree of the original beam and cross-sectional area of longitudinal tensile rebar on the ultimate bearing capacity and ductility of ESRB were discussed. Finally, a simplified method was put forward to further verify the effectiveness of ESRB through analytical calculation.
Details
Keywords
Maha Assad, Rami Hawileh, Ghada Karaki, Jamal Abdalla and M.Z. Naser
This research paper aims to investigate reinforced concrete (RC) walls' behaviour under fire and identify the thermal and mechanical factors that affect their performance.
Abstract
Purpose
This research paper aims to investigate reinforced concrete (RC) walls' behaviour under fire and identify the thermal and mechanical factors that affect their performance.
Design/methodology/approach
A three-dimensional (3D) finite element (FE) model is developed to predict the response of RC walls under fire and is validated through experimental tests on RC wall specimens subjected to fire conditions. The numerical model incorporates temperature-dependent properties of the constituent materials. Moreover, the validated model was used in a parametric study to inspect the effect of the fire scenario, reinforcement concrete cover, reinforcement ratio and configuration, and wall thickness on the thermal and structural behaviour of the walls subjected to fire.
Findings
The developed 3D FE model successfully predicted the response of experimentally tested RC walls under fire conditions. Results showed that the fire resistance of the walls was highly compromised under hydrocarbon fire. In addition, the minimum wall thickness specified by EC2 may not be sufficient to achieve the desired fire resistance under considered fire scenarios.
Originality/value
There is limited research on the performance of RC walls exposed to fire scenarios. The study contributed to the current state-of-the-art research on the behaviour of RC walls of different concrete types exposed to fire loading, and it also identified the factors affecting the fire resistance of RC walls. This guides the consideration and optimisation of design parameters to improve RC walls performance in the event of a fire.
Details
Keywords
Maria Ghannoum, Joseph Assaad, Michel Daaboul and Abdulkader El-Mir
The use of waste polyethylene terephthalate (PET) plastics derived from shredded bottles in concrete is not formalized yet, especially in reinforced members such as beams and…
Abstract
Purpose
The use of waste polyethylene terephthalate (PET) plastics derived from shredded bottles in concrete is not formalized yet, especially in reinforced members such as beams and columns. The disposal of plastic wastes in concrete is a viable alternative to manage those wastes while minimizing the environmental impacts associated to recycling, carbon dioxide emissions and energy consumption.
Design/methodology/approach
This paper evaluates the suitability of 2D deterministic and stochastic finite element (FE) modeling to predict the shear strength behavior of reinforced concrete (RC) beams without stirrups. Different concrete mixtures prepared with 1.5%–4.5% PET additions, by volume, are investigated.
Findings
Test results showed that the deterministic and stochastic FE approaches are accurate to assess the maximum load of RC beams at failure and corresponding midspan deflection. However, the crack patterns observed experimentally during the different stages of loading can only be reproduced using the stochastic FE approach. This later method accounts for the concrete heterogeneity due to PET additions, allowing a statistical simulation of the effect of mechanical properties (i.e. compressive strength, tensile strength and Young’s modulus) on the output FE parameters.
Originality/value
Data presented in this paper can be of interest to civil and structural engineers, aiming to predict the failure mechanisms of RC beams containing plastic wastes, while minimizing the experimental time and resources needed to estimate the variability effect of concrete properties on the performance of such structures.
Details
Keywords
Prathamesh Gaikwad and Sandeep Sathe
The purpose of this paper is to study and analyze the effects of fly ash (FA) as a mineral admixture on compressive strength (CS), carbonation resistance and corrosion resistance…
Abstract
Purpose
The purpose of this paper is to study and analyze the effects of fly ash (FA) as a mineral admixture on compressive strength (CS), carbonation resistance and corrosion resistance of reinforced concrete (RC). In addition, the utilization of inexpensive and abundantly available FA as a cement replacement in concrete has several benefits including reduced OPC usage and elimination of the FA disposal problem.
Design/methodology/approach
Reinforcement corrosion and carbonation significantly affect the strength and durability of the RC structures. Also, the utilization of FA as green corrosion inhibitors, which are nontoxic and environmentally friendly alternatives. This review discusses the effects of FA on the mechanical characteristics of concrete. Also, this review analyzes the impact of FA as a partial replacement of cement in concrete and its effect on the depth of carbonation in concrete elements and the corrosion rate of embedded steel as well as the chemical composition and microstructure (X-ray diffraction analysis and scanning electron microscopy) of FA concrete were also reviewed.
Findings
This review provides a clear analysis of the available study, providing a thorough overview of the current state of knowledge on this topic. Regarding concrete CS, the findings indicate that the incorporation of FA often leads to a loss in early-age strength. However, as the curing period increased, the strength of fly ash concrete (FAC) increased with or even surpassed that of conventional concrete. Analysis of the accelerated carbonation test revealed that incorporating FA into the concrete mix led to a shallower carbonation depth and slower diffusion of carbon dioxide (CO2) into the concrete. Furthermore, the half-cell potential test shows that the inclusion of FA increases the durability of RC by slowing the rate of steel-reinforcement corrosion.
Originality/value
This systematic review analyzes a wide range of existing studies on the topic, providing a comprehensive overview of the research conducted so far. This review intends to critically assess the enhancements in mechanical and durability attributes (such as CS, carbonation and corrosion resistance) of FAC and FA-RC. This systematic review has practical implications for the construction and engineering industries. This can support engineers and designers in making informed decisions regarding the use of FA in concrete mixtures, considering both its benefits and potential drawbacks.
Details
Keywords
Steel-reinforced concrete-filled steel tubular (SRCFST) columns have been increasingly popular in engineering practice for the columns' excellent seismic and fire performance…
Abstract
Purpose
Steel-reinforced concrete-filled steel tubular (SRCFST) columns have been increasingly popular in engineering practice for the columns' excellent seismic and fire performance. Significant design progress guidance has been made through continuous numerical and experimental research in recent years. This paper tested and analysed the residual loading capacity of SRCFST columns under axial loading after experiencing non-uniform ISO-834 standard fire.
Design/methodology/approach
The experimental research covered the main parameter of heating conditions, 1-side and 2-side fire, through two specimens. Two specimens were heated and loaded simultaneously in the furnace for 240 min. After cooling, the columns were moved to the hydraulic loading system and loaded to failure to determine the columns' residual capacity.
Findings
The experimental results indicated that the non-uniform heating area plays an essential role in the overall performance of SRCFST columns, the increasing heating area of columns results in lower residual loading capacity and stiffness. The SRCFST columns still had a high loading capacity after heating and loading in the fire.
Originality/value
The comparison of experimental data against design results showed that the design method generated a 16% safety margin for S2H4 and a 39% safety margin for S1H4.
Details
Keywords
Jun Zhao, Hao Zhang, Junwei Liu, Yanfen Gong, Songqiang Wan, Long Liu, Jiacheng Li, Ziyi Song, Shiyao Zhang and Qingrui Li
Based on the weak seismic performance and low ductility of coupled shear walls, engineered cementitious composites (ECC) is utilized to strengthen it to solve the deformation…
Abstract
Purpose
Based on the weak seismic performance and low ductility of coupled shear walls, engineered cementitious composites (ECC) is utilized to strengthen it to solve the deformation problem in tall buildings more effectively and study its mechanical properties more deeply.
Design/methodology/approach
The properties of reinforced concrete coupled shear wall (RCCSW) and reinforced ECC coupled shear wall (RECSW) have been studied by numerical simulation, which is in good agreement with the experimental results. The reliability of the finite element model is verified. On this basis, a detailed parameter study is carried out, including the strength and reinforcement ratio of longitudinal rebar, the placement height of ECC in the wall limb and the position of ECC connecting beams. The study indexes include failure mode and the skeleton curve.
Findings
The results suggest that the bearing capacity of RECSW is significantly affected by the ratio of longitudinal rebar. When the ratio of longitudinal rebar increases from 0.47% to 3.35%, the bearing capacity of RECSW increases from 250 kN to 303 kN, an increase of 21%. The strength of longitudinal rebar has little influence on the bearing capacity of RECSW. When the strength of the longitudinal rebar increases, the bearing capacity of RECSW increases little. The failure mode of RECSW can be improved by lowering the casting height of the ECC beam in a certain range.
Originality/value
In this paper, ECC is used to strengthen the coupled shear wall, and the accuracy of the finite element model is verified from the failure mode and skeleton curve. On this basis, the casting height of the ECC casting wall limb, the strength and reinforcement ratio of longitudinal rebar and the position of the ECC beam are studied in detail.
Details
Keywords
Yasser M. Mater, Ahmed A. Elansary and Hany A. Abdalla
The use of recycled coarse aggregate in concrete structures promotes environmental sustainability; however, performance of these structures might be negatively impacted when it is…
Abstract
Purpose
The use of recycled coarse aggregate in concrete structures promotes environmental sustainability; however, performance of these structures might be negatively impacted when it is used as a replacement to traditional aggregate. This paper aims to simulate recycled concrete beams strengthened with carbon fiber-reinforced polymer (CFRP), to advance the modeling and use of recycled concrete structures.
Design/methodology/approach
To investigate the performance of beams with recycled coarse aggregate concrete (RCAC), finite element models (FEMs) were developed to simulate 12 preloaded RCAC beams, strengthened with two CFRP strengthening schemes. Details of the modeling are provided including the material models, boundary conditions, applied loads, analysis solver, mesh analysis and computational efficiency.
Findings
Using FEM, a parametric study was carried out to assess the influence of CFRP thickness on the strengthening efficiency. The FEM provided results in good agreement with those from the experiments with differences and standard deviation not exceeding 11.1% and 3.1%, respectively. It was found that increasing the CFRP laminate thickness improved the load-carrying capacity of the strengthened beams.
Originality/value
The developed models simulate the preloading and loading up to failure with/without CFRP strengthening for the investigated beams. Moreover, the models were validated against the experimental results of 12 beams in terms of crack pattern as well as load, deflection and strain.
Details