Bar Diameter Research Articles

ФУНКЦИЯ НАДЕЖНОСТИ ПРЕДВАРИТЕЛЬНО НАПРЯЖЕННОЙ КОРРОДИРОВАННОЙ ЖЕЛЕЗОБЕТОННОЙ БАЛКИ ПРИ НЕЛИНЕЙНОМ РАСПРОСТРАНЕНИИ КОРРОЗИИ

The paper considers the limit state function in the context of reliability analysis of corroded beams. Methods for determining the ultimate load limit for corroded beams are discussed. Various approaches to the determination of the limit state function are considered, including those based on statistical data on corrosion and modelling of stresses in a reinforced concrete beam. A general reliability assessment model for reinforced concrete structures should include corrosion propagation. Most previous studies have focused on one-dimensional diffusion problems with an assumed constant corrosion rate. A nonlinear corrosion rate model, unlike linear models, considers the corrosion current density not constant over the service life of a reinforced concrete structure. An approach to reliability analysis together with a nonlinear corrosion growth model is developed. In this paper, the main problems related to reliability under a nonlinear model of prestressed reinforcement rope corrosion of reinforced concrete beams are discussed. A function for the reduction of reinforcing bar diameter from time is presented. Sensitivity analysis is performed to determine the effect of corrosion growth parameters on the reliability index of reinforced concrete T-beam. The nonlinear corrosion growth model, together with other relevant probabilistic models used to describe random variables, was applied to analyze the reliability of a reinforced concrete crane girder. The expression of corrosion current density shows that the corrosion rate increases exponentially as the value of the design parameter of the model increases. To further evaluate the effect of the proposed time corrosion growth model on the reliability of reinforced concrete beam, two specific cases are considered. The first one is with fixed corrosion current density, and the second one is with fixed corrosion growth at a given time.

The capacity of GFRP anchors in concrete and masonry structures

Fiber-reinforced polymer composites, due to their exceptional lightweight and strength characteristics, are now widely used to strengthen reinforced concrete or masonry structures. Among many applications, they are used as anchorage systems using preformed pultruded bars or high-strength fiber ropes to be impregnated in situ. In both cases, the anchoring part is a bar-type dowel component inserted into holes filled with a binder or adhesive material. One of the lesser-studied issues of their use is the pull-out strength of the anchorage system. It depends on several factors, such as the type of substrate, the anchorage bar diameter, the bonding agent, the anchorage length, etc. This paper summarizes the anchorage mechanism of GFRP bars through the analysis of several experimental data. The shortcomings of the current state of knowledge and some useful recommendations for further studies are presented. Thus, the paper is aimed at contributing to a better evaluation of the effectiveness of anchorages in FRP strengthening systems, and in particular of the GFRP bars used for anchoring fiber meshes and fabrics to prevent the overturning of infill walls in reinforced concrete buildings or walls in masonry buildings.

Research on No-bracket Construction of Building Structure Reinforcement

This paper studies the no-bracket construction technology for reinforced concrete reinforcement, and uses planting-bar technology as support to solve the problem that the scaffolding cannot be erected for construction due to site factors. Firstly, the steel bar pullout test was carried out to study the influence of concrete strength, planting bar diameter, planting bar depth, and concrete structure type on the pullout force of the planting-bar. Secondly, the finite element method was used to simulate the selection of formwork and planting-bar parameters under different working conditions. The simulation results were basically consistent with the planting-bar pullout test, which provided appropriate formwork parameters and planting-bar parameters for different construction situations and a theoretical reference for the reconstruction and expansion project under the factors such as insufficient site for erection of supports.

Effect of loading type on RC T-Beam sections involving construction errors

The paper presents the effect of loading type on RC T-beam sections involving construction errors. This study involved 12 RC T- beams specimens divided into two main categories according to loading method. First category were loaded with uniformly distributed load at two-edges of slab while the second, were loaded with two-point concentrated loads at the middle length of beam specimen. The aim of this study is to evaluate, the effect of malposition of slab reinforcement, unequal configuration of slab reinforcement and change in bar diameter of slab reinforcement on the structural behavior of T-beam sections. The results indicated that malposition of slab reinforcement leads to a lower bending moment capacity of the slab. Flexural capacity of T-beams were higher than the rectangular beams where part of slab contributes to the resistance of the loads. Well-arranged distribution of reinforcement improves the ductile behavior of the slab and reduces the corresponding deflections.

Enhancement of RC T‐beams toughness using laced stirrups reinforcement for blast response predictions

AbstractThe dynamic behavior of laced reinforced concrete (LRC) T‐beams could give high‐energy absorption capabilities without significantly affecting the cost, which was offered through a combination of high strength and ductile response. In this paper, LRC T‐beams, composed of inclined continuous reinforcement on each side of the beam, were investigated to maintain high deformations as predicted in blast resistance. The beams were tested under four‐point loading to create pure bending zones and obtain the ultimate flexural capacities. Transverse reinforcement using lacing reinforcement and conventional vertical stirrups were compared in terms of deformation, strain, and toughness changes of the tested beams. The inclination angles of the used lacing reinforcement with respect to the longitudinal reinforcement were 45° and 60°. The lacing reinforcement was efficient and participated actively in resisting the bending moments and shear forces at the same time. For the same diameter of lacing reinforcement, the 60° inclination angle imposed more ductility before failure than beams with lacing reinforcement of a 45° inclination angle. Moreover, the lacing bar diameter was more effective in improving the load‐carrying capacities when using the inclination angle of 45°. A finite element (FE) model was developed and validated using the experimental results based on the measured deformations and strains to conduct a parametric study. The investigated parameters included the effect of the arrangements of the applied loads, laced rebar diameter, inclination angle, tension reinforcement ratio, and concrete strength.

Cyclic response of precast concrete columns connected with cast-in-place UHPC in plastic hinge region

Ultra high performance concrete (UHPC) is a promising material for lap splice connection of steel bars in reinforced concrete (RC) precast structures given its high compressive strength, its high toughness, and its high bond strength with steel bars. This paper focuses on the cyclic response of bottom frame columns connected by UHPC in the plastic hinge region. The effect of lap length of longitudinal bars in UHPC (6d, 8d and 12d, d = diameter of longitudinal bar), axial load ratio and stirrup ratio of the UHPC connection region on the global response of the columns were presented and analyzed, and a cast-in-site RC column was prepared for comparison. The behavior of the UHPC connected columns was flexural dominated, but columns with 6d and 8d lap length failed due to the gradual bonding degradation between UHPC and longitudinal bars, and the column with 12d lap length failed due to UHPC crushing. It was demonstrated that a 8d lap length could achieve equivalent lateral bearing capacity and ductility to the control RC column, but the lap length should be greater than 8d when applying UHPC connection technology in seismic regions to ensure the energy dissipation. Column with lower axial load ratio (0.17) exhibited lower ductility because shear sliding occurred between the interface of UHPC and footing at the post-peak stage. The UHPC connected specimens exhibited higher resilience and better damage resistance in earthquake because the ratios of the residual displacements to the corresponding peak displacements were between 17 and 39%. Besides, a flexural capacity model for the columns was developed and the results predicted by the model agreed well with the experimental results.

Experimental study on bond performance between deformed steel bar and coal gangue concrete

AbstractCoal gangue concrete (CGC), a great low cost and environment‐friendly material, is considered to be the most effective substitute for normal concrete. The bond performance of steel bar embedded in CGC determines the feasibility of using CGC as structure material. So, this study presents an experimental program to investigate the bond strength of steel bar embedded in CGC compared to the one in normal‐aggregate concrete. The experimental program contains 75 specimens that are tested using the pull‐out test. In this study, coal gangue coarse aggregate replacement ratios (0%, 25%, 50%, 75%, and 100%), water–cement ratio (0.50, 0.45, and 0.40), and rebar diameters (14 mm, 16 mm, and 18 mm) were considered to analyze the variation law of bond strength. The test results show that the bond strength increased slightly with the decrease of water–cement ratio. The bond strength decreased slightly with the increase the aggregate replacement ratio if the replacement ratio was less than 50%. In contrast, the bond strength decreased significantly when the aggregate replacement ratio was more than 50%. In addition, the bond strength increases first and then reduces with increasing of bar diameters. Lastly, a new model of predicting the bond strength between the deformed steel bar and coal gangue concrete was proposed in this study because the widely used prediction models for the bond strength were not suitable for the coal gangue concrete.

Effect of confining stirrups and bar gap in improving bond behavior of glass fiber reinforced polymer (GFRP) bar lap splices in RC beams

Fiber-reinforced polymer (FRP) bars are becoming a popular replacement for steel rebars that are vulnerable to corrosion, especially under harsh corrosive environments. Despite several advantages for using FRP rebars, the bond between FRP bars and surrounding concrete has been a major concern that affects the behavior of FRP-reinforced structural members. The experimental program of this study comprises testing eight full-scale glass FRP (GFRP) reinforced beams under two-point loads. There were two control beams and six beams having rebar lap splices. The beams were reinforced using 2ϕ12 GFRP bars. The first control had continuous GFRP bars, and the 2nd control had GFRP lap splice conforming to the relevant ACI code. The lap splice was 65 times the bar diameter in six beams having lap splice. The contact lap and non-contact laps were used along with the variable spacing of shear stirrups in the lap zone (50, 100 mm, ∞, i.e., no shear stirrups). The lap splice, designed conforming to the ACI code, was found to be very conservative. The reduction in shear stirrups’ spacing in the lap zone and the gap between lapped bars was found to enhance the bond performance of GFRP bars by up to 31 %. The authors’ previous models for predicting development length and bond are found to show good predictions for the experimental results of the present study as well. Analytical models are developed for predicting with sufficient precision the peak load for GFRP reinforced beams with the two types of lap splices (non-contact and contact).

Numerical and theoretical research on flexural behaviour of steel-precast UHPC composite beams

In order to promote the utilization of high strength materials and application of prefabricated structures, flexural behaviour of section steel-precast UHPC (Ultra-High performance concrete) slab composite beams prefabricated with bolt shear connectors are numerically simulated by the finite element (FE) software ABAQUS. The model is verified by three prefabricated steel-concrete composite beams tested. Numerical analysis results are in good accordance with experimental results. Furthermore, parametric studies are conducted to investigate the effects of strength of section steel and concrete of precast slab, thickness of section steel, width and height of precast concrete slab, diameters of steel bars and bolt shear connectors. The flexural behaviour of composite beams, in terms of bearing capacity, deflection, ductility and energy dissipation, are compared. The numerical results indicate that the improvement of strength of section steel results in a decrease of ductility, but a significant increase of the ultimate load and energy dissipation. Compared with composite beam made of section steel with thickness of 10 mm, the ultimate load of beams made of section steel with thickness of 14 and 18 mm improve by 29.0% and 58.8%, respectively, the ductility enhance by 2.8% and 8.3%, respectively, and the energy dissipation improve by 8.0% and 12.3%, respectively. With the increase of concrete strength, the ultimate load, deflection and energy dissipation gradually increase. The ductility of steel-UHPC composite beam is the highest, that of steel-HSC composite beam is the lowest. The effect of reinforcement ratio of concrete slab and diameter of shear bolts on the ultimate load of composite beam is limited. Simplified formulae for two different sectional types of proper-reinforced section steel-precast UHPC slab composite beams occurred bending failure are proposed, and the predicted results fit well with the simulated results. The results can be taken as a reference for the design and construction of section steel-precast UHPC slab composite beams.

Estimating the diameter of reinforcing bars using an ultra-wideband MIMO GPR array

Ground-penetrating radar (GPR) is an effective non-destructive detection technology for locating and characterizing reinforcing bars in concrete structures. However, the accurate quantification of reinforcing bar diameters, especially in small-diameter cases, remains a challenging issue. In this paper, a sizing method based on multiple-input-multiple-output (MIMO) GPR arrays is presented to estimate the reinforcing bar diameter in concrete. The method employs a linear array of ultra-wideband (UWB) antennas to acquire the full-matrix MIMO data of the reinforcing bar embedded in concrete. The diffraction stacking algorithm is applied to the obtained MIMO data to reconstruct the reinforcing bar. The 3 decibels (dB) drop technique is used to measure the chord length that passes through the peak intensity point of the reconstruction image of the reinforcing bar. Following that, the diameter of the reinforcing bar can be determined based on its cover depth and the chord length. Extensive numerical studies and experiments have been conducted to examine the performance of the proposed method in different scenarios. The method shows excellent sizing accuracy for reinforcing bars with different diameters and cover depths.

Bonding of Carbon Steel Bars in Concrete Produced with Recycled Aggregates: A Systematic Review of the Literature

Civil construction is essential for the world economy and the largest generator of construction and demolition waste (CDW), mainly due to a lack of planning, technological control, and restoration execution, among other factors. While efforts are made to minimize this waste generation, one possible application for CDW is its incorporation into Portland cement-based materials as recycled aggregates, in partial or total replacement of natural aggregates. However, for CDW use to be feasible, the structure performance and safety must be assured, and the adherence between concrete and reinforcement bars, in this context, is a fundamental mechanism. With this perspective, this paper aims to investigate the influence of recycled aggregate on steel–concrete bonding. To this end, the SREE (Systematic Review for Engineering and Experiments) method was employed as a novelty, including a methodology quality analysis, to search and analyze relevant scientific articles published in the last ten years. The results revealed that the use of CDW as recycled aggregates in concrete worsens the steel–concrete bonding, and that ribbed steel bar seems to be the best option when employed in RC structures built with CDW-concrete, although the bar diameter and the anchorage length still need further investigations, and that CDW-concrete’s use can significantly contribute to reducing the emission of greenhouse gases and to capturing CO2 from the atmosphere. Therefore, further investigations should focus on the real influence of recycled aggregate type and replacement content, bar diameter, anchorage length, and CDW’s potential to capture CO2.

Tensile behavior of GFRP bar at quasi-static and high strain rate

In order to better use GFRP bar in civil engineering applications, a clearer knowledge of its mechanical properties under static and dynamic loadings is necessary. In this study, quasi-static experiments were carried out on glass fiber and GFRP bars with different diameters. High strain rate experiments (102 ∼ 103s−1) were carried out on GFRP bars with a diameter of 6 mm. The results show that GFRP bar has size effect at quasi-static. The tensile strength, elastic modulus decrease with increasing diameter of GFRP bar. GFRP bar has strain rate effect. The tensile strength and maximum strain increase with increasing strain rates. The elastic modulus decrease with increasing strain rates. The distribution function of failure probability of GFRP bar is obtained by Weibull analysis. The difference between static tensile failure mode and high strain rate tensile failure mode of GFRP reinforcement is analyzed by SEM.

Bond-slip behaviours between preplaced aggregate concrete (PAC) and steel bars

In this article, 54 specimens with diverse types and strength grades of concrete and various embedded lengths and diameter of steel bars were prepared and the bond-slip behaviours between preplaced aggregate concrete (PAC) and steel bars was evaluated by pull-out tests. Then, a bond stress-slip constitutive relationship was proposed on the basis of the thick-walled cylinder model. Finally, the accuracy of the proposed bond-slip constitutive relationship was verified by finite element analysis (FEA) simulation. The results indicated that the bond stress-slip curves could be roughly divided into four sections. The bond strength for PAC under different concrete strength grades were all superior to those for normal concrete (NC). The proposed theoretical model provided a good prediction of bond strength for PAC with reasonable parameters selection. The simulated bond stress-slip curves for PAC were basically in accordance with the testing results which illustrated that the proposed bond-slip constitutive relationship was reasonable. In the future, the accuracy of the evaluation of the bearing capacity of precast concrete structures composed of PAC will be significantly improved by introducing the proposed bond-slip constitutive model.

Predicting transverse crack properties in continuously reinforced concrete pavement

Transverse crack properties (crack spacing and crack width) are important indicators of service life performance of continuously reinforced concrete pavements (CRCP). Crack properties are related to concrete material properties, reinforcement ratio, interface friction between both the concrete-base layer and concrete-steel, and the local climatic conditions. An improved analytical model with a bilinear concrete-base friction relationship is presented to predict crack spacing and crack width from concrete drying shrinkage and temperature contraction. The proposed 1D model was validated with test section data from a continuously reinforced concrete beam resting on asphalt base layer, which contained two reinforcement ratios, a standard paving concrete, and a lightweight aggregate concrete. A sensitivity study of model determined the bond stiffness coefficient between the concrete and reinforcement, bar spacing and diameter, elastic modulus of the reinforcement, and concrete drying shrinkage had the greatest impact on both crack spacing and crack width.

Analysis and Modelling of Reinforced Concrete Beams

The work is to understanding the behaviour of structural components like beams and columns during loading is crucial for the development of efficient and safe structures. In this report, the reinforced concrete beam has been analyzed and modelled when subjected to two-point loads and single-point load conditions, using the Finite Element Analysis tool, popularly called ANSYS software. The analyzed and modelled beam has a dimension of 500mm × 100 mm × 100 mm with 2 numbers of 8mm diameter bars are main reinforced, and 2 numbers of 8 mm diameter are hanger bars. The behaviour of the analysed beam has been observed regarding the shear behavior, crack widths and displacement for various static loading. According to the analysis carriedout on the Reinforced Concrete beams using ANSYS, it is observed that results are more profound to reinforcement size, materials properties, load percentage increment, etc.

Experimental investigation of bond performance between BFRP and different strength recycled-aggregate concrete

In recent years, there has been a large number of studies on recycled-aggregate concrete as a potential solution to the problem of a scarcity natural resources. This study investigated the bonding performance of a new reinforcement material employed in medium and high-strength recycled aggregate concrete. The pull-out test was carried out by employing basalt fiber-reinforced polymer (BFRP) bars with different diameters (12, 14, and 20 mm) in medium and high-strength concrete with different ratios of recycled coarse aggregate replacement (0, 25, 50, 75, and 100%). Based on the concrete bond damage, the failure modes were identified, the corresponding bond mechanism was analyzed and the bond stress–slip characteristics were summarized. The effect of each parameter on the failure mode, bond strength, and the bond-slip curve between recycled-aggregate concrete and BFRP bars was evaluated. Results indicated that as the diameter of the BFRP bar increased, the failure mode was shifted, the uneven distribution of bond stress became more pronounced, and the bond strength showed a decreasing trend. Two distinct situations of medium to high-strength concrete with very different relative bond strengths at different replacement ratios were found. The relative bond strength of medium-strength concrete increased at first and then decreased with the increase of the replacement ratio of recycled coarse aggregate. A non-linear relationship between the bond strength of recycled concrete and its compressive strength was found. The two-stage model was proposed to describe the bonding behaviour more accurately between BFRP bar and medium to high-strength recycled aggregate concrete.

Enhancing Sustainability of Corroded RC Structures: Estimating Steel-to-Concrete Bond Strength with ANN and SVM Algorithms

The bond strength between concrete and corroded steel reinforcement bar is one of the main responsible factors that affect the ultimate load-carrying capacity of reinforced concrete (RC) structures. Therefore, the prediction of accurate bond strength has become an important parameter for the safety measurements of RC structures. However, the analytical models are not enough to estimate the bond strength, as they are built using various assumptions and limited datasets. The machine learning (ML) techniques named artificial neural network (ANN) and support vector machine (SVM) have been used to estimate the bond strength between concrete and corroded steel reinforcement bar. The considered input parameters in this research are the surface area of the specimen, concrete cover, type of reinforcement bars, yield strength of reinforcement bars, concrete compressive strength, diameter of reinforcement bars, bond length, water/cement ratio, and corrosion level of reinforcement bars. These parameters were used to build the ANN and SVM models. The reliability of the developed ANN and SVM models have been compared with twenty analytical models. Moreover, the analyzed results revealed that the precision and efficiency of the ANN and SVM models are higher compared with the analytical models. The radar plot and Taylor diagrams have also been utilized to show the graphical representation of the best-fitted model. The proposed ANN model has the best precision and reliability compared with the SVM model, with a correlation coefficient of 0.99, mean absolute error of 1.091 MPa, and root mean square error of 1.495 MPa. Researchers and designers can apply the developed ANN model to precisely estimate the steel-to-concrete bond strength.

Life performance of 40-year-old RC beams with different concrete covers and bar diameters in natural corrosion environments

This study entailed an experimental evaluation of the life performance of 40-year-old reinforced concrete (RC) beams with different concrete cover depths and tensile bar diameters. Beams that were naturally corroded in a marine environment were used in this study, and no artificial process was employed to accelerate the corrosion. Most existing evaluations of beams employ electrical acceleration, admixture, or exposure to designed chloride environments to aid corrosion. Given the paucity of studies on naturally corroded beams, this study is of significance regarding the design, service, and life assessment of RC structures. Two-point load bending test was employed to examine the residual mechanical performance. The corroded bars were extracted to assess the corrosion properties, while the mechanical properties were evaluated via a tensile test. The focus of this study was on evaluating the progress of deterioration and capacity loss in naturally aged beams. The results indicated that a concrete cover of 50 mm satisfies the requirements of a design service life of 50 years. Furthermore, the cross-sectional loss–ultimate capacity loss relationship is consistently linear for the RC beams. Thus, the estimation of ultimate capacity loss based on cross-sectional loss is acceptable in case of natural corrosion of the RC beams. Hence, the findings can contribute to the prediction of the life performance and maintenance of existing structures as well as to designing new structures.

Ultimate Bearing Capacity Analysis of Pile Caps with New Socket Connections

Socket connection need a groove reserved in the cap to accommodate a bridge pier, which greatly weaken the vertical bearing capacity of the cap. The conventional treatment measure is to increase the thickness of the cap, and the corresponding cost will increase. The measures to enhance the vertical bearing capacity of socket caps without increasing the thickness of the cap were discussed in this paper, including a rough interface at the bottom of the pier, additional hanging bars, high-strength grouting material in the seam, and large-diameter metal corrugated pipes, etc. Based on a previous test, the finite element analysis of the vertical bearing capacity of pile caps with new socket connections was carried out. The analysis parameters included the construction method, steel bar diameter in the bottom of the cap, socket depth, thickness of the bottom plate, pile length, and friction coefficient, etc. The bearing capacity M–N relation of the full-scale model was also analyzed. Research indicated the vertical bearing capacity of the cap is mainly provided by rough interfaces, the bottom plate, and the additional hanging bars, and the contribution of the three parts was about 40%, 34%, and 26%; the vertical bearing capacity was proportional to the areas of steel bars on the cap and the thickness of the bottom plate, and was inversely proportional to the length of the pile. To obtain the vertical bearing capacity of the overall cast-in-place plan for the socket cap, the thickness of the cap needs to be increased by 27%. At last, a design formula for the calculation of the vertical bearing capacity was proposed.

Effect of Heat Treatment on the Resulting Dimensional Characteristics of the C45 Carbon Steel after Turning

The presented article deals with the influence of the heat treatment of C45 steel on the surface quality after turning. Turning is a machining technology used to prepare specific geometrical characteristics of surface and dimensional quality. In the present paper, the same turning conditions were used for the turning treatment of differently heat-treated steels. The soft annealed state, normalized state, hardened state, quenched and tempered at 530 °C state and quenched and tempered at 660 °C state have been analyzed. By using this approach, it has been possible to evaluate the effects of hardening and machining on the resulting parameters after turning (roughness, cylindricity and circularity). The highest hardness was observed in the steel after the hardening process (694 ± 9 HV 10). The hardening has negatively influenced the surface quality. The high hardness was related to martensite formation and caused a damage to the cutting edge of the cut insert used, leading to a significant change in geometrical accuracy. The cylindricity change achieved 0.15 ± 0.03 mm which was significantly higher compared to the theoretical value of the diameter of the machined steel bar. An inaccuracy was also observed in diameter dimension. These inaccuracies were caused by the wear of the cutting edge of the tool used in cutting parameters setting.