جستجوی مقالات مرتبط با کلیدواژه « reinforced concrete » در نشریات گروه « مواد و متالورژی »

Using externally bonded (EB) fibre-reinforced composites for the enhancement of reinforced concrete (RC) structures had been addressed in extensive research throughout recent years. Despite the numerous works on the flexural, shear, and axial strengthening of reinforced concrete members, there are not many works on the torsional strengthening. As a result, information about how reinforced RC members under torsion behave in EB composites tends to be rather limited. In this research, the torsional strengthening of RC beams using EB composites will be thoroughly analyzed and reviewed. After a thoroughly literature review, a database of experimental tests is established, containing beams made of EB Fiber Reinforced Polymer (FRP). To ascertain the effectiveness of the strengthening system, the geometric and mechanical features of RC beams, composite kinds, and casing configurations were assessed, along with the investigation of several failure modes for failure beams. It was concluded that, according to the experimental data, the torsional strength of RC beams can be improved by using FRCM composites and EB FRP. A torsional strength increase of the database beams ranged from 0% to 178%, with an average of 51%. Fully wrapped beams showed the greatest increase in torsional strength.

The failure of shear-type beam-column joints in reinforced concrete (RC) frames during severe earthquake attacks is a critical concern. Traditional methods for determining joint shear capacity often lack accuracy due to improper consideration of governing parameters, impacting the behaviour of these joints. This study assesses the capabilities of machine learning techniques in predicting joint shear capacity and failure modes for exterior beam-column joints, considering their complex structural behaviour. An artificial neural network (ANN) model is proposed for predicting the shear strength of reinforced exterior beam-column joints. ANN, a component of artificial intelligence that learns from past experiences, is gaining popularity in civil engineering. The ANN model is developed using a dataset comprising material properties, specimen dimensions, and seismic loading conditions from previous experimental investigations. The model considers twelve input parameters to predict shear strength in exterior beam-column joints. Training and testing of the ANN model are conducted using established design codes, empirical formulas, and a specific algorithm. The results demonstrate the superiority of the proposed Shallow Feed Forward Artificial Neural Network (SFF-ANN) compared to previous approaches. The effectiveness of an Artificial Neural Network (ANN) model was quantitatively assessed in this study, with a focus on its performance in comparison to various design codes commonly used in structural engineering. The model was assessed using the coefficient of determination (R2) and achieved R-squared values of 99%, 94%, and 98% during the training, testing, and validation stages, respectively. The study highlights the significance of beam reinforcement as a key element in estimating shear capacity for exterior RC beam-column connections. Although the proposed models exhibit a high degree of precision, future research should focus on developing improved models using expanded datasets and advanced algorithms for enhanced pattern recognition and performance.

The purpose of this study is to evaluate the behaviour and the performance of reinforced concrete (RC) exterior Beam-Column Joints (BCJ) experimentally under reverse quasi-static cycle displacement test conducted for ductile and non-ductile detailed reinforcement. Two columns (one upper and one lower) and one beam were used to construct the specimen; the beam end is free, while the other ends are fixed. These specimens were subjected to reverse cyclic quasi-static stress till failure. At each cycle, the hysteresis curve, cracking loads, ultimate loads, deflection of the loaded at the free end of the beam, crack patterns, and failure mechanisms of BCJ were recorded and studied. Additionally, all specimens’ energy dissipation and stiffness deterioration were addressed. The experimental results reveal that the ductile joint (DJ) performance is more satisfactory in all the parameters than the non-ductile joint (NDJ). The ultimate load and energy dissipation of DJ is approximately 20% higher than the NDJ. However, expected beam failure occurred in the ductile joint, and the non-ductile joint underwent undesirable joint failure.

Reinforced concrete moment resisting frame (RCMRF) is one of the most popular structural systems. Conventionally, buildings with RCMRF systems are designed to satisfy the relative displacement, resistance, and flexibility requirements defined by the design codes. Structural design codes have given different ranges of design parameters that the designers and engineers must consider in the design process of structures and the values selected for these parameters affect the seismic behaviour of the structures. However, performance assessment of the RCMRF under the earthquake loading to limit the probable levels of damage has a complicated and difficult procedure that is time-consuming for designing of ordinary buildings. In this study, to prevent this time-consuming process, tighter ranges for design parameters have been attempted to improve the seismic performance of the RCMRFs. In this regard, databases of RCMFs were created for different ranges of design parameters. The Particle Swarm Optimization (PSO) algorithm is used to create these databases and RCMRFs are optimally designed according to ACI 318-14 code. Then, nonlinear time history analysis according to ASCE/SEI 7-16 code was performed on the RCMRFs in each one of the databases and the statistical analysis of local and global results acquired from the nonlinear time history analysis is carried out. Finally, tighter ranges of design parameters have been determined to achieve more robust structures without involvement in time-consuming processes.

This study investigates the bond strength behaviour of plain surface wave type configuration (PSWC) rebars in comparison to mild steel (MS) and high yield strength deformed (HYSD)  rebars of varied rib configuration as per BIS and ASTM standards. The variables in the rebar include plain surface, curved surface, parallel rib, diamond rib and Nano modified cement polymer anticorrosive coating (CPAC). Total of 30 pull-out specimens and 12 beam-end specimens were put to a pull-out test following BIS and ASTM standard respectively. The load corresponding to 0.025mm free end (FE) slip and 0.25mm loaded end (LE) slip were carefully observed. The load-deflection behaviour, appearance of the first crack in the specimens and ultimate failure load was recorded. The experimental results showed that as compared to MS rebars, HYSD rebars offer an approximately threefold increase in ultimate bond strength and 1.5 times increase in usable bond strength irrespective of varied rib configuration. PSWC rebars with 4mm offset and 80mm pitch offered 2.4 times increase in ultimate strength and 76.2% increase in usable bond strength as compared to MS rebars. The ultimate pull-out load of PSWC rebars was around 25% and the usable bond strength was only 8.6% lesser than HYSD rebars with parallel ribs. The adopted coating enhanced the corrosion resistance and the reduction in bond strength with any surface configuration was less than the permissible maximum reduction of 20% as specified in IS 13620-1993. Hence it can be concluded that PSWC rebars offered promising bond strength results and upon further optimization and study in other aspects,  PSWC rebars can be a way to replace HYSD rebars in future for enhancing concrete durability at zero added cost.

Reinforced concrete hollow-core slab (HCS) is a new type of lightweight slabs in which the longitudinal voids provide the ability to reduce the concrete amount. Reducing the concrete amount causes a reduction of the dead loads which consequently leads to cost-saving, fast construction, and getting long-span. The experimental program includes constructing and testing slab species with dimensions 1700×435×125mm to investigate the effect of eliminating concrete ratio by changing the size of the longitudinal void and the number of longitudinal voids on the performance of HCS. The experimental results showed that elimination of the concrete with percentages 10.83, 17.20 and 24.37% from the hollow-core high strength slabs using three longitudinal voids of diameters 50, 63, and 75mm, respectively, resulted in saving the ultimate strength by 90.06, 87.84 and 85.07%, and increasing the ultimate deflection by 5.48, 10.80 and 17.44%. While, elimination of the concrete with percentages 16.25, 24.37 and 32.50% from the hollow-core high strength slabs using two, three, and four longitudinal voids of 75mm diameter resulted in saving the ultimate strength with percentages 89.29, 85.07 and 80.61%, and increasing the ultimate deflection with percentages 7.57, 17.44 and 22.81% respectively when compared with the reference solid slab.

In recent years, fiber-reinforced polymer-polyvinyl chloride (FRP-PVC) tubular columns have been used increas-ingly in civil engineering applications. Concrete-filled RP-PVC tubes possess high durability, high strengthening performance, satisfactory bond strength, and compressive behavior. It has been observed that these cost-effec-tive tubular columns are promising materials for enhancing strain capacities, strength, and stiffness of structures containing reinforced concrete (RC). These composite tubular columns are composed of FRP and PVC and are used for strengthening concrete. FRP enhances strength capacity while PVC improves the corrosion resistance of concrete piles in harsh environments. This review focuses on the properties of FRP-PVC tubular columns, their application in civil engineering, and the recent advancements in this field.©2020 jourcc. All rights reserved.