High-strength Reinforcement Research Articles

Fabrication of Novel Polyurethane matrix-based Functional Composites with Enhanced Mechanical Performance

Thermoplastic polyurethane (TPU) has gained significant interest in several fields, including automobile steering wheels, and the electronics sector due to their easier processability, abrasive resistance, and self-lubricating performances. However, their strong inherent flammability and significant smoke and heat production during burning limit their industrial applications. Therefore, its applicability can be enhanced with the addition of high-strength reinforcement and making them antibacterial and flame-retardant. This research is designed to examine the influence of zirconium phosphate (ZrP) and zinc oxide (ZnO) nanoparticles on the novel polyurethane/glass fiber reinforced composites for flame retardant and antibacterial applications with improved mechanical performance. Three different types of novel polyurethane (PU1, PU2, PU3) matrices were prepared using different recipes, and 7% ZrP and 5% ZnO nanoparticles were added to the polyurethane matrices separately, and their corresponding composite samples were fabricated using glass reinforcement. Mechanical i.e., Charpy impact, hardness and tensile, and functional i.e., flame retardancy (FR) and antibacterial tests were performed to compare their performance. Mechanical testing results showed that PU3-based composite samples showed the highest values of impact force, hardness, and tensile strength in both ZrP and ZnO nanoparticle-based composite samples. Furthermore, 7% ZrP-PU3 composite exhibited the best performance of flame retardancy due to the presence of hexamethylene diisocyanates (HDI) content. Likewise, the 5% ZnO-PU3-based composite exhibited the highest antibacterial activity along with enhanced mechanical performance.

Методы прогнозирования долгосрочного поведения преднапряженных железобетонных мостов

Purpose: to analyze the causes of long-term deformations of prestressed concrete bridge spans and the problems associated with their prediction. To provide a brief overview of existing methods for predicting the long-term behavior of prestressed concrete bridges. The relevance of the problem is due to the need to ensure the reliability and durability of these structures, which are widely used in modern bridge construction. The objective of this paper is to identify factors that influence the development of long-term deformations and to develop approaches for their accurate prediction. Methods: the study examines the long-term deformations of prestressed concrete bridge spans and the problems associated with their prediction using existing bridge structures as examples. Existing methods for predicting long-term deformations in prestressed concrete are evaluated. In particular, the effects of high-strength reinforcement relaxation and the effects of concrete creep and shrinkage are analyzed. Results: accurate prediction of long-term deformations is a complex task that requires consideration of many factors, such as prestress losses, environmental conditions, material properties, and structural characteristics of bridges. The methods discussed in this paper, including the multiplier method and the approximate time interval method, demonstrate their effectiveness in evaluating long-term deformations. However, further research is needed to improve the prediction methods and increase the efficiency of prestressed concrete bridge design. Practical significance: provides design engineers with specific methods and approaches for evaluating the long-term behavior of prestressed concrete bridges. Application of these methods can reduce the risk of excessive deformations and deflections, ultimately ensuring the safety and reliability of bridge structures.

Hybrid simulation testing of two-storey low-aspect-ratio nuclear RC shear walls with normal- and high-strength reinforcement: Seismic performance evaluation and economic assessment

Low-aspect-ratio reinforced concrete (RC) shear walls have been commonly used in several nuclear facilities in containment and safety-related structures. Despite being a potential alternative to reduce rebar congestion and subsequently minimize complex construction activities typically associated with nuclear facilities, there has been limited experimental research on investigating the impact of using high-strength reinforcement (HSR) on the seismic performance of such walls, particularly in a multi-storey context. This lack of research is mainly due to considerable challenges imposed when testing such multi-storey nuclear RC shear walls in most laboratories. Therefore, the current study presents the experimental results of two two-storey low-aspect-ratio nuclear RC shear walls that were tested utilizing the seismic hybrid simulation testing technique. In this respect, walls W1-NSR and W2-HSR were designed using normal-strength reinforcement (NSR) and HSR, respectively, where the two test walls had comparable capacities to allow for direct comparisons. Both walls were subjected to various ground motion levels, spanning from operational to design and beyond-design earthquake scenarios. The experimental findings are then presented to include the force-displacement responses, the multi-storey effects, ductility capacities, lateral and rotational stiffnesses, rebar strains, and cracking patterns of the test walls. Subsequently, an economic assessment was carried out to quantify the total rebar weights and the corresponding construction costs of such walls. In addition, the expected seismic repair costs were determined based on a three-dimensional digital image correlation technique that provided information on the damage states of the test walls under different earthquake levels. The results show that although W1-NSR and W2-HSR attained similar force and moment capacities, W2-HSR achieved a relatively higher ductility capacity than W1-NSR. However, larger cracks were observed in W2-HSR compared to W1-NSR, which was attributed to the associated larger rebar spacing in the former relative to the latter. The economic assessment results demonstrate that using HSR minimized the rebar weights and construction costs, while both walls had similar seismic repair costs at their design and beyond-design earthquake levels. Both the seismic performance and economic assessment results presented in the current study are expected to aid future editions of relevant design standards in adopting HSR in nuclear construction practice.

Shear behavior of reinforced concrete beams with high-strength reinforcements after high temperatures

This paper investigates the effect of steel reinforcement configured with different strengths after different high temperatures on the shear performance of the test beams, a total of 20 reinforced concrete (RC) beams, through experiments, numerical analyses and theoretical studies, in order to understand the key factors affecting the shear performance of the beams. The test revealed that the mechanical properties of concrete and steel reinforcement showed a trend of increasing and then decreasing after high temperatures. Increasing the stirrup ratio and stirrup strength can significantly improve the crack resistance and shear capacity of the beams, as well as the deformation performance of the beams. The residual shear strengths of test beams with high-strength stirrups after exposure to high temperatures are significantly greater than those of ordinary reinforced concrete beams. Specifically, the shear capacity of beams with high-strength stirrups after exposure to 800°C increased by 23.7 % compared to ordinary beams, and the mid-span deflection performance increased by 28.7 %. The stresses in the shear span region of the test beams after high temperature were more concentrated at the diagonal and the number of cracks was significantly reduced. In this paper, a simplified formula for calculating the residual shear capacity of RC beams after room and high temperatures is proposed, which can well predict the test results.

Compression and energy absorption of wood-based reinforced 3D Kagome lattice structures

3D Kagome lattice sandwich structure is recognized as the most excellent lattice configuration. However, the preparation method of 3D Kagome is complicated and the raw materials for its preparation are limited to materials with high plasticity. In this study, we developed a wood-based 3D Kagome lattice structure that combines discrete rods into a continuous core using reinforcement. Orthogonal tests, theoretical analysis, and finite element simulations were performed to investigate the correlation between the dimensional parameters, the mechanical properties, and the energy absorption capacity. The damage modes were found to be mainly bending fracture, core shear, and panel rupture, with the use of reinforcement affecting the damage modes. Compressive properties of the 3D Kagome lattice structure are increased by increasing core diameter and inclination degree, decreasing core in-cut diameter, and using high-strength reinforcements. Finite element simulations further confirm that the use of high-strength reinforcements changes the stress distribution of the lattice structure. The 3D Kagome lattice structure with an inclination degree of 65°, a core diameter of 10 mm, a reinforcement wall thickness of 2 mm, and a core in-cut diameter of 2 mm has the optimal compression performance and energy absorption capacity.

Dynamic Response Analysis Method of a High-Strength RC Beam Subjected to Long-Duration Blast Loading

An analysis method of normalized pressure–impulse (P-I) diagrams related to the ductility ratio of structural components is proposed, to quickly estimate the dynamic response of high-strength reinforcement concrete (RC) beams subjected to long-duration blast loading. Firstly, the overall bending deformation mode of RC beams is uncovered via explosion tests in a closed chamber, where the durations of the near-planar blast loadings are varied within 80–105 ms. Then, a single-degree-of-freedom (SDOF) model is established based on the bending deformation mode. The resistance function for the uniform pressure loading is developed using a novel approach, consisting of (1) developing and benchmarking a three-dimensional (3D) improved steel–concrete separated finite-element (FE) model; (2) using the benchmarked FE model to conduct numerical simulations for uniform pressure loading; and (3) idealizing the resistance function for uniform pressure using a bilinear relationship. Finally, the SDOF model is used to conduct parametric analyses and develop a normalized P-I diagram that can be used to analyze or design RC beams for far-field blast effects. This P-I diagram is verified using results from blast load tests that are primarily in the dynamic region. A total of 188 additional 3D nonlinear FE analyses of RC beams are conducted to expand the database in the impulse and quasi-static regions. Considering the limitations of the proposed method in predicting the shear-dominated deformation and the fracture behavior of members, the P-I diagram is applicable to the dynamic response of the bending deformation of members under far-field explosion, which can provide an important reference for the blast-resistant design and analysis of high-strength RC beams.

Effect of high-strength and stainless steel reinforcement on the flexural behavior of UHPC beams

Ultra-high performance concrete (UHPC) is an advanced cement-based composite which shows remarkable properties including very high compressive strength, increased tensile resistance, impressive toughness and excellent durability. One promising application of UHPC is in heavily-loaded beams and slabs where its use can allow for increased design efficiency and improved durability. Conversely, the high bond capacity of UHPC can lead to early bar fracture failures, especially when using low amounts of ordinary steel reinforcement. This paper examines the influence of reinforcement grade on the flexural ductility of UHPC beams. As part of the study, three beams built with either Grade 400 MPa ordinary steel reinforcement, Grade 690 MPa high-strength reinforcement or Grade 520 MPa stainless steel reinforcement, are tested under flexural loading. The key test parameters include the influence of concrete type (UHPC vs. conventional high-strength concrete) and steel type (high-strength or stainless steel vs. ordinary steel). The results show that the flexural strength and ductility of the UHPC beams is influenced by the steel grade/type. The beam with ordinary steel shows a well-defined yield point but fails by bar rupture. Increased resistance by 47% is observed when using high-strength bars, however bar rupture occurs owing to the low strain-capacity of this steel type. Combining UHPC with higher ductility stainless steel does not increase capacity, but leads to remarkable ductility by 75%. As part of the numerical study the behaviour of the beams is predicted using FE modelling and the effects of tension steel ratio, UHPC tensile strength and high-strength or stainless steel type are investigated.

Experimental investigation of uncertain factors on the mechanical properties of half-grouted sleeve connected with large-diameter high-strength reinforcement

The half-grouted sleeve connection (HGSC) is widely used to connect reinforcement in precast concrete (PC) structures. While some studies have examined the mechanical behavior of the HGSC, there is still a lack of research on uncertain factors with large-diameter high-strength reinforcement. To fill this gap, an extensive experimental study was conducted to investigate the mechanical properties of the HGSC under monotonic tensile loads. The impact of various uncertain factors, including the embedded length, water-binder ratio (w/b) of the grouting material, eccentricity of rebar, thread diameter, and thread length, was investigated. It was found that the HGS connected with large-diameter high-strength reinforcement has four damage modes, i.e., thread fracture, thread pullout, reinforcement fracture, and bond-slip failure. Notably, to obtain the target of equivalent reinforcement, the dispersion ratio of the w/b should be controlled within 0.3, the embedded length should be greater than 6d, and the thread diameter and the thread length should not be less than 1d. Based on the HGSC investigated in this paper, a model for predicting the axial force and circumferential confining strain was presented, and a method was provided to calculate the elastic and plastic lengths for the embedded reinforcement. This study provides valuable guidance for the application of large-diameter high-strength rebar in PC structures.

Seismic performance and flexural strength prediction of high-strength bar reinforced UHPFRC walls under high axial load ratio

A new-type shear wall built with high-strength reinforcement and ultra-high performance fiber reinforced concrete (UHPFRC) is proposed in this paper, aiming to solve the problem of too large cross-section size of bottom shear wall members of high-rise and super high-rise buildings. Four UHPFRC wall specimens built with high-strength reinforcement were tested under cyclic loading to examine the influence of the parameters of fiber volume fractions (0 vs. 1.5% vs. 2.5%) and the spaces of horizontal distribution reinforcing bars (150 mm vs. 300 mm) on the seismic performance. In addition, a calculation method of flexural strength of UHPFRC shear wall is established. The research results show that: the UHPC wall specimen without fibers failed in the axial compression brittle mode, and the UHPFRC wall specimens with fibers failed in flexure-dominated ductile mode. The bridging effect of steel fibers at the cracks kept the integrity of the UHPFRC. The drift ratio capacities of the UHPFRC wall specimens under high axial compression ratio of 0.5 were 3.56%. Increasing the fiber volume fractions can improve the strength, initial stiffness, and cumulative energy consumption of the wall specimens, reduce the damage degree of the UHPFRC at the toes of the wall specimens, and can also reduce the reinforcement ratio of horizontal reinforcement without influence on the seismic performance. The proposed method of flexural strength of UHPFC walls shows reasonable prediction accuracy.

Moment Redistribution in UHPC Continuous Beams Reinforced with High-Strength Steel Bars: Numerical Investigation and Prediction Model

Considering moment redistribution in the design of ultra-high-performance concrete (UHPC) statically indeterminate structures can fully exploit the load-bearing potential of members, simplify reinforcement details, and save construction costs. Due to the excellent properties of ultra-high-performance concrete (UHPC) that distinguish it from conventional concrete, new characteristics of the moment redistribution manifest in UHPC structures. In this study, a finite element (FE) analytical model was developed to simulate and analyze the bending behavior and moment redistribution of UHPC continuous beams reinforced with high-strength steel bars. The simulation and test results exhibited excellent agreement with the experimental research. Based on the FE model, a fine analysis for nine simulated two-span UHPC continuous beams was conducted with a detailed discussion of the failure modes, load-displacement curves, variations of support reaction forces, tensile strains of steel bars, and the whole process of moment redistribution. Subsequently, the variation rules of moment redistribution in UHPC continuous beams were explored by an extensive parametric study of 108 simulated beams. The studied parameters included a neutral axis depth factor, concrete strength, yielding strength of reinforcement, beam depth, span–depth ratio, reinforcement ratio between the mid-span and intermediate support section, as well as load forms. According to the numerical results, new formulas for estimating the two-stage moment redistribution in UHPC continuous beams with high-strength reinforcement were established. Finally, a comparison of moment redistribution between normal concrete continuous beams and UHPC continuous beams was performed. It can be observed that the elastic moment distribution in UHPC continuous beams was comparatively smaller, while the plastic moment distribution was relatively larger than those of normal concrete continuous beams. Overall, the degree of the total moment distribution in UHPC structures was greater than that of normal concrete structures due to the high ductility of UHPC. The research in this study may provide a technical reference for the practical engineering of UHPC.

Formation of structure and physical and mechanical properties of reinforcing steels during high-temperature thermomechanical treatment

The effect of high-temperature thermomechanical treatment (HTMT) modes on the formation of the structure and physical and mechanical properties of reinforcing St5 steel is considered. It is shown that with HTMT in the mode of intensive (interrupted) cooling, there is a significant difference in hardness (47 HRC on the surface versus 31 HRC in the core) and a significant change in mechanical properties (σв, σ0,2, δ5). It is established that under conditions of maximum intensive cooling, the reinforcing bar does not have time to completely calcinate. The use of continuous cooling mode allows for a more uniform distribution of mechanical properties. The production of high-strength reinforcement of А800, А1000, Аt1200 strength classes after the HTMT is ensured by the formation of a dispersed martensitic-troostite structure in steel.

Experimental Study on Crack Width of HRB600 Grade High-Strength Steel Bar Reinforced Concrete Beams

High-strength reinforcement is an important direction in the development of civil engineering. In order to fill the gap that the current concrete structure code GB50010 has no standard regulations applicable to HRB600-grade high-strength reinforcement, this paper conducted an experimental investigation on the crack width of eight concrete beams reinforced with HRB600-grade high-strength reinforcement. The study examined various parameters to understand the crack development process, crack spacing, and factors influencing crack width in the pure bending section. The results revealed that the damage mode and crack development process of high-strength reinforced concrete beams were similar to those observed in ordinary reinforced concrete bending members. The crack spacing in the pure bending section was independent of the concrete strength, and the average crack width in the pure bending section exhibited a proportional relationship with the reinforcement strain. Moreover, both were mathematically related to the ratio of reinforcement diameter and ratio. A calculation formula for the maximum crack width suitable for HRB600-grade reinforced concrete beams was developed and fit. The HRB600-grade high-strength reinforcement had an obvious yield stage and good ductility, and the test study provides a powerful reference for promoting the application of high-strength reinforcement in concrete structures.

Enhancing performance and sustainability: CRB600H high-strength reinforcement in recycled concrete

This paper addresses the urgent need for high-performance, eco-friendly construction materials due to increasing urbanization. It introduces CRB600H high-strength reinforcement to enhance recycled aggregate concrete (RAC) beam performance. Comparative analysis with conventional concrete (CC) beams demonstrates RAC's inferior shear performance, which CRB600H reinforcement effectively improves. A novel optimization method for high-strength reinforcement is established based on equal strength principles, demonstrating cost-efficiency. Economic analysis reveals that despite rising production costs with increased recycled aggregate replacement ratios, CRB600H reinforcement substantially reduces expenses, even when more expensive than HRB400 reinforcement. The environmental analysis reveals that the CRB600H reinforcement significantly influences the environmental performance of reinforced concrete beams. Utilizing 100% RAC beam with CRB600H as an illustrative example, the contribution rates of steel bars to Global Warming Potential (GWP), Acidification Potential (AP), Eutrophication Potential (EP), and Cumulative Energy Demand (CED) are determined as 39.30%, 56.85%, 51.87%, and 55.76%, respectively. In comparison to CC beam with HRB400, the 100% RAC beam with CRB600H exhibit reductions of 10.27%, 18.59%, 19.03%, and 16.93% in terms of GWP, AP, EP, and CED, respectively. In conclusion, CRB600H reinforcement offers cost-effective, eco-friendly solutions, promising significant advancements in RAC applications.

Seismic Behavior of High-Strength Recycled Aggregate Concrete Columns with High-Strength Reinforcement

ABSTRACT This study investigated the seismic performance of high-strength recycled aggregate concrete (RAC) columns with high-strength reinforcement under cyclic loading. Five full-scale columns were carried out, and the results revealed that the lateral loading capacity of RAC column was slightly lower than that of natural aggregate concrete column. Increasing the axial load, the lateral loading capacity of RAC columns increased significantly. Increasing the concrete strength under the same axial load, the lateral loading capacity was slightly increased. Based on the test results, a numerical simulation model was established. Finally, a flexural capacity calculation model and an N–M curve calculation model are proposed.

Application of the Deformation Theory in Section Analysis of Reinforced Concrete Members with High-Strength Reinforcement

Application of the Deformation Theory in Section Analysis of Reinforced Concrete Members with High-Strength Reinforcement

Seismic fragility and post-earthquake reparability of concrete encased-and-filled steel tubular bridges columns with debonded high-strength reinforcements

Seismic fragility and post-earthquake reparability of concrete encased-and-filled steel tubular bridges columns with debonded high-strength reinforcements

Seismic Performance and Nonlinear Strain Analysis of Mechanical Splices for High-Strength Reinforcement in Concrete Structures.

This study investigates the strain development in reinforcing bars within the plastic hinge regions of beams and columns, with the main objective of modifying the current acceptance criteria for mechanical bar splices to accommodate high-strength reinforcement. The investigation utilizes numerical analysis based on moment-curvature and deformation analysis of typical beam and column sections in a special moment frame. The results indicate that the use of higher grade reinforcement, such as Grade 550 or 690, results in lower strain demands in the plastic hinge regions compared to Grade 420 reinforcement. To validate the modified seismic loading protocol, over 100 samples of mechanical coupling systems were tested in Taiwan. The test results demonstrate that the majority of these systems can successfully complete the modified seismic loading protocol and are suitable for use in critical plastic hinge regions of special moment frames. However, caution is advised for slender mortar-grouted coupling sleeves, as they were unable to fulfill the seismic loading protocols. These sleeves may be conditionally used in plastic hinge regions of precast columns, provided they meet specific conditions and demonstrate seismic performance through structural testing. The findings of this study offer valuable insight into the design and application of mechanical splices in high-strength reinforcement scenarios.

Effects of Using High-Strength Reinforcement in the Seismic Performance of a Tall RC Shear Wall Building

Chile’s reinforced concrete (RC) design is based on ACI 318-08, where high-strength reinforcement is not allowed in seismic force-resistant members. In 2019, new requirements adopted by ACI 318 permitted the incorporation of high-strength reinforcement in walls. This study compared the seismic performance of two Chilean 20-story residential buildings on soft soil, one designed with traditional Grade 60 and the other with high-strength Grade 80 reinforcement. The performance was assessed in terms of the probability of exceeding the ASCE 41 limit states during a 50-year lifecycle. Analyses showed that both buildings had similar seismic performance. However, the reduction in reinforcement in the Grade 80 building was close to 18%. It is concluded that using high-strength reinforcement in a typical wall building implies a significant reduction in the reinforcement used without affecting the seismic performance.

Experimental evaluation on the seismic performance of high-strength reinforcement beam-column joints with different parameters

This paper reports the results of cyclic load tests and analysis of full-scale beam-column joints using 600 MPa high-strength reinforcement as beam longitudinal reinforcements. The focus was on evaluating the effect of the relative length of beam bars through the joint (hc/d) on the seismic performance of the high-strength reinforcement beam-column joints, while the effects of variables such as axial compression ratio, shear compression ratio, and transverse reinforcement ratio were also discussed. The failure pattern, strength, stiffness, ductility, energy dissipation, and bond performance of each specimen under reciprocal loading were analyzed. The test results showed that applying high-strength steel bars improved the failure pattern, load-bearing capacity, and energy dissipation of the joints. The increase in hc/d improved the bond degradation of the high-strength reinforcement, which positively influenced the seismic performance of the joint. Conversely, high axial compression ratios and high shear compression ratios had a clear negative effect on the bond degradation and failure patterns when high-strength reinforcement used. A proposed equation for adjusting the hc/d in a high-strength reinforcement joint was also presented, which considered the effect of concrete strength and reinforcement strength on the bond performance of beam reinforcement.

Studies of spun concrete poles for electric power transmission line supports reinforced with Au1000P rebars

Introduction. In connection with the present volumes of electrification in central Russia, the need for the construction of new electric power transmission lines (EPTLs) has decreased considerably. At the same time, the natural degradation of EPTL supports in time, as well as the prospects for developing the vast expanses of the northern, Siberian and Far Eastern regions, caused by the reorientation of Russia’s economic relations from the West to the East, make it urgent to increase production volumes and technical and economic efficiency of using spun reinforced concrete poles for EPTL supports.Aim. Industrial implementation of spun reinforced concrete poles with the high-strength innovation profile reinforcement by replacing A800 rebars with four-row-profile Au1000P rebars.Materials and methods. The article provides data on the full-scale tests of spun reinforced concrete poles for EPTL supports according to the GOST 22687.1-85 “Centrifugal cylinder reinforced concrete posts for high-voltage transmission lines. Structure and dimensions” [1]. Three pole samples with a length of 26 m were prepared and tested. One sample consisted of prestressed A800 rebars according to GOST 22687.1-85, while the other two prototypes include the prestressed Au1000P rebars with the four-row profile. In the second sample, the reinforcement scheme (diameters and rebar quantity) repeats the standard option, increasing the bearing capacity of the pole. Having the same bearing capacity as the pole, manufactured according to the GOST, the third sample promoted for the reduction in the quantity of non-stressed rebars.Results. A new scheme for reinforcing the pole sample using Au1000P rebars was developed. The results of the sample testing are presented; a comparative evaluation of the pole strength and deformation characteristics is given; technical and economic indicators, as well as the recommendations regarding the reinforcement of the prestressed spun concrete poles with Au1000P rebars are provided.Conclusion. According to the results of the performed study, an economic effect was established due to a reduction in the quantity of non-stressed rebars by 28 %. Poles with Au1000P prestressed rebars have an increased corrosion resistance and durability due to the closing of cracks formed during the impact of short-term dynamic loads from wind gusts, wire breaks, etc. In terms of a recommendation, it is proposed to update the GOST 22687.1-85 in order to use new types of high-strength reinforcement rolled products and higher strength concrete.