Prestress Level Research Articles

Experimental and numerical investigation on flexural behavior of concrete beams strengthened by different NSM tendons

To comprehensively study the flexural behavior of RC beams strengthened by means of near-surface mounted (NSM) technology, 142 simply supported concrete beams strengthened in flexure with a wide variety of NSM materials, including fiber reinforced polymers (FRPs) and metallic materials were collected from previous experimental studies. The effects of the material properties and number of NSM reinforcements on the failure modes of beams strengthened with the NSM system were analyzed. The enhancements in the load-bearing capacity, ductility, and energy consumption capacity of beams were discussed. By classifying the NSM strengthening materials into brittle reinforcement and ductile reinforcement, the results demonstrated that beams strengthened with brittle NSM reinforcement were prone to premature brittle failure modes, as beams strengthened with only one FRP tendon easily failed through rupture of FRP, and those with more than one tendon were prone to debonding failure. Whereas beams using ductile materials were more likely to fail in a ductile manner. A numerical analysis was performed to predict the maximum strength of beams strengthened with different materials and prestress levels. Conservative prediction was observed for beams that failed by concrete crushing, and overestimated prediction was observed for beams governed by debonding failure or rupture of NSM tendons.

Load-induced blood marker kinetics in patients with medial knee compartment osteoarthritis are associated with accumulated load and patient reported outcome measures

Background: This study aimed to quantify the mechanoresponse of 10 blood marker candidates for joint metabolism to a walking stress test in patients with knee osteoarthritis and to determine the association among marker kinetics and with accumulated load and patient reported outcomes. Methods: 24 patients with knee osteoarthritis completed questionnaires, and a walking stress test with six blood serum samples and gait analysis. Concentrations of cartilage oligomeric matrix protein (COMP), matrix metalloproteinases (MMP)-1, -3, and -9, epitope resulting from cleavage of type II collagen by collagenases (C2C), type II procollagen (CPII), interleukin (IL)-6, proteoglycan (PRG)-4, A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, and resistin were determined by enzyme-linked immunosorbent assays, Joint load (moments and compartmental forces) was estimated using musculoskeletal modeling using gait analysis data. Results: COMP and MMP-3 showed an immediate increase after the walking stress followed by a decrease. MMP-9 and resistin showed a delayed decrease below pre-stress levels. ∆COMP correlated with ∆MMP-3 for most time points. ∆MMP-9 correlated with ∆resistin for most time points. The load-induced increase in blood marker levels correlated among blood markers and time points. C2C and resistin correlated positively and C2C/CPII and MMP2 correlated negatively with load during gait. Immediate relative ∆CPII and ∆MMP1 and delayed relative ∆COMP, ∆IL6, ∆C2C, ∆CPII, ∆MMP1 and ∆MMP3 correlated with the load accumulated during the walking stress. Baseline C2C levels correlated with Knee Osteoarthritis Outcome Score (KOOS) subscales and load-induced changes in MMP-3 with KOOS and Short Form 36 quality of life subscores (P<0.05). Conclusions: The distinct and differentiated physiological response to the walking stress depends on accumulated load and appears relevant for patient reported osteoarthritis outcome and quality of life and warrants further investigation in the context of disease progression. ClinicalTrials.gov registration: NCT02622204

Prestress and size optimization of double-curvature cable domes using an incremental-prestressing iterative technique

A major challenge in designing new forms of cable domes is to keep balance between structural weight and stiffness. Increasing prestress level should decrease the maximum displacement and this, in turn, may lead to heavier structures and higher costs. Accordingly, the required cross sections and prestress level that achieve stability and strength constraints vary whenever this weight-stiffness balance changes, typically as moving along a Pareto front that represents the solution of a two-objective optimization of weight and displacement. Apart from complicated derivation of the gradient of optimization function or using time-consuming gradient-free optimization algorithms, this study proposes a time-efficient iterative technique aims at developing a trade-off curve between the optimized weight and corresponding displacement of cable domes that simulates the Pareto front solution of two-objective optimization. This curve provides insights into the extent to which the optimized weight would increase when decreasing the maximum displacement, giving the designer a decision support tool to select the most preferred solution. The proposed technique is based on prestressing the dome with an appropriate initial level of prestress, then increasing the level of prestress incrementally until reaching the target stiffness. By each increment of prestress level, the dome is designed to the minimum weight that achieves the stability and strength constraints through sub-iterations. The variables of this incremental-prestressing (IP) iterative technique are prestress level and size of elements with constraints on stability of struts and strength of cables. The resulting pairs of optimized weight and corresponding displacement at all increments of prestress level are, then, fitted to a power function formulating the trade-off curve. The proposed IP technique is used to design a simple illustrative example as well as a realistic double-curvature cable dome. The efficiency of the proposed technique is verified by comparing the resulting trade-off curve of cable dome example to the Pareto optimal solutions obtained by a two-objective optimization of weight and displacement using NSGA-II algorithm. Different geometrical parameters are considered to highlight the time-efficiency of the IP technique for further usage as a robust tool in large parametric studies in which surrogate functions are developed to predict the optimized weight and prestress level of cable domes at specific target stiffness.

Flexural strengthening of damaged steel beams with prestressed CFRP plates using a novel prestressing system

This study developed a novel prestressing system of the carbon fiber reinforced polymer (CFRP) plate to strengthen damaged steel beams, which reduced the operation space at the tensioning end, thereby extending the application range of prestressing system. Flexural tests were conducted to verify this system and investigate the effects of the adhesive layer, prestressing level, and CFRP plate area on the strengthening efficiency, and subsequently, a parametric analysis was carried out using finite element modeling to obtain more influencing rules of the unbonded CFRP plate-strengthened steel beams. The results indicated that satisfactory strengthening efficiency could be achieved by the novel prestressing system. The adhesive layer significantly affected the strain distributions of the steel–CFRP composite section, whereas it had a very slight effect on the flexural behavior of the steel beams, and the bonded and unbonded CFRP plates had a similar strengthening efficiency. Nonprestressed CFRP plate exhibited limited improvement in the flexural capacity and stiffness of the damaged steel beams under the normal service state; in contrast, the prestressed CFRP significantly increased the flexural behavior of the beams in the elastic and elastic–plastic stages owing to the high strength utilization of the CFRP plate. In addition, as the prestressing level increased, strengthening efficiency increased. Solely increasing the area or elastic modulus of the CFRP plate improved the strengthening efficiency slightly, whereas applying a prestress simultaneously clearly increases the strengthening efficiency. The strengthening efficiency increases with artificial notch depth.

High-Fat Diet Exacerbates Stress Responsivity in Juvenile Traumatic Brain Injury.

Abstract Traumatic brain injury (TBI) is one of the leading causes of death for children in the United States. Juveniles are more likely to sustain TBIs than most other age groups, and TBI has been shown to result in increased anxiety and stress behaviors. In addition, the hypothalamic-pituitary-adrenal (HPA) axis has previously been shown to become dysregulated after a TBI. Further, many children consume diets high in saturated fats and refined sugars, which are also connected to alterations in HPA axis function and behavior disorders. The goal of the current study was to identify a potential relationship between high-fat diet (HFD) consumption and TBI on HPA axis function in juvenile rats. In the present study, male juvenile Long-Evans rats were fed either a combination of an HFD with a high-fructose corn syrup solution or a standard chow diet. On post-natal Day 30, subjects sustained either a sham TBI or a TBI via the Closed-Head Injury Model of Engineered Rotational Acceleration (CHIMERA). Subjects participated in a trial of the open field test (OFT) following injury. In addition, some rats performed in an acute restraint stress test. All subjects were euthanized 7 days post-injury. Brain and blood plasma samples were collected for use in real-time polymerase chain reaction (RT-PCR), immunohistochemistry, and corticosterone or adrenocorticotropic hormone (ACTH) assays. Immediately following TBI, injured juveniles had increased time to righting and walking, with HFD-fed TBI rats having increased time to walking over Chow-fed TBI rats. HFD-fed TBI rats had a reduced number of entries to the center of the OFT, in addition to reduced time spent in the center compared with HFD Sham controls and Chow TBI rats. During the acute restraint stress test, HFD-fed TBI rats had elevated pre-stress ACTH and corticosterone and post-stress ACTH levels. Pre-stress ACTH levels were significantly elevated in HFD TBI compared with Chow TBI. Further, pre-stress ACTH:corticosterone ratios were elevated in HFD TBI compared with Chow TBI. cFos immunoreactivity in the paraventricular nucleus (PVN) of the hypothalamus following the acute restraint stress test was elevated in HFD-fed TBI rats. HFD TBI rats had greater activation of cFos in the PVN compared with Chow TBI. In addition, RT-PCR showed significantly reduced expression of relevant HPA axis genes, NR3C1, NR3C2, and CRHR2, in the hypothalamus of TBI subjects compared with Sham subjects. Further, AVP and CRHR2 in the hypothalamus were significantly reduced in HFD TBI compared with Chow TBI. These results offer evidence that TBI paired with high-fat diet consumption can cause HPA axis dysfunction, resulting in more anxiety-like behaviors.

Biaxial prestress and waveguide effects on estimates of the complex shear modulus using optical elastography in a transverse isotropic cornea phantom

Tensile prestress is inherent to the functional role of some biological tissues currently being studied using elastography, such as skeletal and cardiac muscle, arterial walls, and the cornea. Therefore, the impact of prestress coupled with waveguide effects due to small dimensions in one or more directions needs to be better understood. An experimental configuration is designed, fabricated, and experimentally tested using optical elastography. Thin layered isotropic and transversely isotropic phantoms are statically stretched biaxially in plane while simultaneously conducting optical elastography measurements of out of plane motion. Guided by analytical models and numerical finite element simulations, experimental measurements are post-processed to obtain an estimate of the complex (viscoelastic) shear modulus as a function of prestress level and frequency of vibratory motion.

Uniaxial prestress and waveguide effects on estimates of the complex shear modulus using magnetic resonance elastography in a transverse isotropic muscle phantom and excised muscle

Tensile prestress is inherent to the functional role of some biological tissues currently being studied using elastography, such as skeletal and cardiac muscle, arterial walls, and the cornea. Therefore, the impact of prestress coupled with waveguide effects due to small dimensions in one or more directions needs to be better understood. An experimental configuration is designed, fabricated and experimentally tested using magnetic resonance elastography (MRE). Cylindrically-shaped isotropic and transversely isotropic phantoms, as well as the excised cat soleus muscle are statically stretched along their main axis to specific prestrain levels while simultaneously conducting MRE measurements that enable synchronous motion-encoding in all three dimensions (polarization directions). In the case of the excised cat soleus, diffusion tensor imaging is also performed to enable a co-registered mapping of fiber structure. Guided by analytical models and numerical finite element simulations, experimental measurements are post-processed to obtain an estimate of the complex (viscoelastic) shear modulus as a function of prestress level and frequency of vibratory motion.

Study the Influence of Grid-Jumping Layout on Spatial Cable-Truss Structure Without Inner Ring Cables with Rupture of Local Cables (STRUTS)

Spatial cable-truss structure without inner ring cables (SCSWIRC) is a new type of cable-truss tension structures (CTTS), and its anti-collapse ability is strong, but its construction forming is difficult. The main reason is that there are a lot of struts (or compression struts) when the span of SCSWIRC is larger and struts are easy to cause winding and collision during its construction. In order to solve the difficulty of construction forming, the grid-jumping layout was proposed to simplify SCSWIRC to delete the redundant struts. It is necessary to further study whether the anti-collapse ability of the remaining structure after the grid-jumping layout is affected by grid- jumping layout. Based on transient dynamic theory, the rupture of local cables (struts) of SCSWIRC with grid- jumping layout is studied. The research results show that self-weight has a little influence on the SCSWIRC; the initial prestress only increases the internal forces of components and the same proportion of feasible prestress levels do not amplify the response of SCSWIRC with rupture of local cables (struts); the anti-collapse ability of the remaining structure after the grid-jumping layout of SCSWIRC is still strong and the ability to resist the external loads is good at the same time. The rupture of local cables (struts) for the original scheme and grid- jumping layout schemes do not cause the progressive collapse. The research contents offer useful reference for the safety design of SCSWIRC.

Stress Detection of Precast Pipe Piles Based on the Low-Loss Slotting Method

Tilting of buildings due to uneven settlement, construction quality issues or other problems is one of the critical accidents threatening the safety of buildings. In order to determine a reasonable solution with respect to the rectification of the tilting building, detection of the stresses of the substructure is necessary. In this study, a stress release method to test the stress of prefabricated pipe pile under loading is studied by combining experimental research and finite element numerical simulation. Based on various measurements, such as traditional strain gauges, vibrating wire strain gauges, and three-dimensional digital image correlation (DIC) tests, the relationship between local residual stress and actual stress of the slotted area at different load levels is determined. Meanwhile, the stress release process in slotted precast pipe pile was numerically simulated with ABAQUS to investigate the influence of the slotting dimension parameters on the stress release rate at different load levels. Based on 1042 sets of finite element modeling results of multi-parameter combination, the quantitative relationship between slot width, depth, spacing, prestress level and stress release rate is studied. An explicit prediction model of the stress release rate is given by regression analysis of combined test results and simulation data. With the prediction model, the stress condition of a loaded precast pipe pile can be accurately predicted based on low-loss slotting. Compared to the traditional stress release method, the proposed method has better controllability and applicability, less damage to the structure, and stronger anti-disturbance ability.

An Image-Based Framework for Measuring the Prestress Level in CFRP Laminates: Experimental Validation.

Image-based methods have been applied to support structural monitoring, product and material testing, and quality control. Lately, deep learning for compute vision is the trend, requiring large and labelled datasets for training and validation, which is often difficult to obtain. The use of synthetic datasets is often applying for data augmentation in different fields. An architecture based on computer vision was proposed to measure strain during prestressing in CFRP laminates. The contact-free architecture was fed by synthetic image datasets and benchmarked for machine learning and deep learning algorithms. The use of these data for monitoring real applications will contribute towards spreading the new monitoring approach, increasing the quality control of the material and application procedure, as well as structural safety. In this paper, the best architecture was validated during experimental tests, to evaluate the performance in real applications from pre-trained synthetic data. The results demonstrate that the architecture implemented enables estimating intermediate strain values, i.e., within the range of training dataset values, but it does not allow for estimating strain values outside those range. The architecture allowed for estimating the strain in real images with an error ∼0.5%, higher than that obtained with synthetic images. Finally, it was not possible to estimate the strain in real cases from the training performed with the synthetic dataset.

Experimental study on the collapse-resistant performance of unbonded prestressed PC beam-column sub-assemblages with pinned connections

In precast concrete frame structures, it is imperative that beam-to-column connection has appropriate robustness and reliable axial resistance to defense against progressive collapse. Hence, a method of using pinned connection and unbonded posttensioning strands (UPSs) to mutually improve the collapse-resistant performance of precast concrete structures was proposed in this study. The pinned connections are used for connecting precast beams with columns at precast beam ends, and UPSs with straight profile are placed at the bottom of beam cross-section. In order to investigate whether the proposed method can enhance collapse-resistant capacity of precast concrete structures, static progressive collapse tests were conducted for the newly proposed precast concrete frame substructures with UPSs (UPPC frame substructures) and without UPSs (PC frame substructure). Moreover, influences of effective prestress level upon the collapse-resistant capacity of UPPC substructure were also investigated. Test results demonstrated that, similar to conventional RC frame structure, the compressive arch action (CAA) and catenary action (CTA) could also develop in the proposed UPPC substructures to avert progressive collapse. The UPPC substructure was able to develop 32% higher CAA capacity and 162% larger CTA capacity as compared to the PC substructure, indicating that the UPSs play a positive role in enhancing both its CAA and CTA. The CTA capacity of the PC substructure was 53.8% higher than that of CAA, which signifies that the pinned connection can be employed to improve structural robustness to mitigate progressive collapse. In addition, the increase of effective prestress level of UPSs is beneficial to the enhancement of CAA capacity of the UPPC substructure. However, higher effective prestress level is limited to improve its CTA capacity due to lower deformation capacity of UPSs. Subsequently, three-dimensional finite element models (FEMs) of the UPPC and PC substructures were developed by using ABAQUS software. By comparing experimental data with FEM results, it was concluded that the FEM could accurately predict the load–displacement curves, crack patterns and reinforcing ruptures of all the test specimens.

Probing in situ capacities of prestressed stayed columns: towards a novel structural health monitoring technique.

Prestressed stayed columns (PSCs) are structural systems whose compressive load-carrying capacity is enhanced through pre-tensioned cable stays. Much research has demonstrated that PSCs buckle subcritically when their prestressing levels maximize the critical buckling load of the theoretically perfect arrangement. Erosion of the pre-tensioned cables' effectiveness (e.g. through creep or corrosion) can thus lead to sudden collapse. The present goal is to develop a structural health monitoring (SHM) technique for in-service PSCs that returns the current structural utilization factor based on selected probing measurements. Hence, PSCs with different cable erosion and varying compression levels are probed in the pre-buckling range within the numerical setting through a nonlinear finite element (FE) model. In contrast to the previous work, it is found presently that the initial lateral stiffness from probing a PSC provides a suitable health index for in-service structures. A machine learning-based surrogate is trained on simulated data of the loading factor, cable erosion and probing indices; it is then used as a predictive tool to return the current utilization factor for PSCs alongside the level of cable erosion given probing measurements, showing excellent accuracy and thus provides confidence that an SHM technique based on probing is indeed feasible. This article is part of the theme issue 'Probing and dynamics of shock sensitive shells'.

Finite Element Analysis of Residual Stress Distribution Patterns of Prestressed Composites Considering Interphases

New finite element analysis procedures are developed in this study to obtain the precise stress distribution patterns of prestressed composites. Within the FEM procedures, an equivalent thermal method is modified to realize the prestress application, and a multi-step methodology is developed to consider coupling effects of polymer curing and prestress application. Thereafter, the effects of interphases' properties, including the elastic modulus and coefficient of thermal expansion (CTE), on the stress distribution patterns are revealed. Analytical methods for residual stress prediction are modified in this study to demonstrate the finite element analysis procedures. From the residual stress results, it is found that the increase in the prestress level tends to contribute to the initiation of interphase debonding. The increase in the elastic modulus or CTE of the interphase results in very large circumferential and axial stress values appearing in the interphase. When the elastic modulus in the interphase is heterogeneous, the predicted stress values in the fiber and matrix are similar to the results predicted with the equivalent elastic modulus of the interphases. However, the heterogeneous elastic modulus results in serious circumferential and axial stress gradients in the interphase.

Experimental and analytical study of RC beams strengthened with prestressed near-surface mounted 7075 aluminum alloy bars

Recently developed high-strength aluminum alloys (AA) have great potentials for strengthening and repairing RC structures because of their merits in high strength-to-weight ratio, high ductility, and inherently corrosion-resistant behaviors. However, few studies have been conducted on taking advantage of AA bars for rehabilitation. This study was therefore carried out to reveal the feasibility of 7075 AA bars on near-surface mounted (NSM) applications for flexural strengthening of reinforced concrete (RC) beams. Experiments of four-point flexural tests were presented to assess the performance of NSM AA bar strengthened beams through eight concrete beams, including a control specimen without strengthening, a specimen strengthened by conventional basalt fiber reinforced polymer (BFRP) bars served as reference, and other six ones using NSM AA strengthening technique with various prestress level and bar arrangement. Results indicate that the application of the strengthening system was able to prevent premature debonding failure and increase the load-bearing capacity by up to 102.1%, but reduced the deformability. In addition, an analytical model for capturing the load–deflection behavior of various strengthening schemes was developed. Good agreements between the results from observations and predictions validated the proposed model, suggesting its potential for guiding the design of the AA strengthening schemes.

Experimental and numerical response of unbonded post-tensioned rocking wall under lateral cyclic loading

This study examined the experimental behavior of three unbonded post-tensioned (PT) single rocking wall (SRW) specimens with varied initial prestressing levels and cross-sectional areas of PT strands subjected to a series of quasi-static cyclic lateral loadings. To investigate the cyclic performance of the specimens, the damage patterns, force-displacement relationship, stiffness degradation, stress of PT strands, and neutral axis depths were compared and evaluated. In addition, the prestress losses of the PT strands experienced in the test were also measured and estimated using a theoretical equation. The test results show that the SRW specimens exhibited low damage, good self-centering, and large deformation capacity with a minor residual drift. Moreover, the low energy dissipation capacity indicates that the SRWs without damping elements cannot be recommended in high seismic zones. In addition, the experimental and predicted results demonstrate that the prestress losses of PT strands in SRWs resulted from wedge seating before they achieved the proportional limit. Finally, a multi-spring model based on the idea of a nonlinear macro element was adopted to simulate the rocking walls in OpenSees software, and the calculated results were consistent with the experimental results.

Numerical Investigation into the Mechanical Behaviours and Energy Characteristics of Hard Coal Subjected to Coupled Static-Dynamic Loads

In practical engineering, coal burst is usually caused by the combination of high geo-stress and dynamic loading. To study the dynamic response of coal in geo-stress conditions, numerical models of a coupled static–dynamic split Hopkinson pressure bar (SHPB) test system were established, based on which impact tests for coal specimens at different impact speeds and static pre-stress levels were conducted. The mechanical properties, energy characteristics and failure patterns of coal specimens under coupled static and dynamic loads were analyzed. The results show that when the pre-stress is constant, peak stress, the maximum strain energy and the maximum kinetic energy increase significantly with impact speed. Nevertheless, they are less affected by the static pre-stress, increasing linearly with a pre-stress level under lower impact speeds but becoming stable under higher impact speeds. In addition, weak dynamic loads may trigger the instability of the coal specimen in a high pre-stress condition. Overall, both the impact speed and static pre-stress have influence on the mechanical behavior and energy characteristics of coal specimens under coupled static and dynamic loads, but the influence of the impact speed outweighs that of the static pre-stress.

Computational model on influence of prestress level on vehicle-bridge coupled vibrations

Computational model on influence of prestress level on vehicle-bridge coupled vibrations

Shear strengthening of concrete deep beams using pre-fabricated strain-hardening cementitious composite plates

This study investigates the efficiency of near surface embedded (NSE) pre-fabricated strain-hardening cementitious composite (P-SHCC) plates for shear strengthening of reinforced concrete deep beams (RC-DBs) through testing 12 identical specimens. For this purpose, P-SHCC plates of 20 mm thickness have been prepared according to the test variables, cured for about 30 days, and then dipped into the concrete cover of the strengthened DBs at the critical shear span. The use of pre-fabricated plates is intended to alleviate any volumetric change issues associated with SHCC material. The studied parameters were the net spacing between the P-SHCC plates (0, 75, 112, and 150 mm), the width of the strengthening plates (60, 75, and 90 mm), and the ratio of steel reinforcement embedded inside the P-SHCC plates (0 %, 0.67 %, 1.50 %, and 3.00 %). Furthermore, the prestressing level relative to the yielding strain of the steel reinforcement embedded inside the P-SHCC plates was of interest. Experimental results exhibited a successful employment of the P-SHCC plates in enhancing the ultimate load capacity of RC deep beams, especially when prestressing was introduced. The gain in the ultimate capacity reached up to 68.5 %, relative to the un-strengthened control beam (BC), depending on the test parameters. Besides, incorporating steel reinforcement inside the P-SHCC plates had a pronounced effect on both the serviceability and ductility characteristics of the strengthened DBs. Specimens strengthened by reinforced P-SHCC plates demonstrated around 1.57-times improvement in energy absorption capacity when compared to their counterparts strengthened by plain P-SHCC plates. Finally, a strut-and-tie model (STM) in addition to a simpler equation based on regression analysis were used to assess the shear capacity of the strengthened DBs, considering the contribution of P-SHCC plates. The proposed two equations were in good accord with the experimental results.

Plasma Hydrogenation of High-Carbon Structural Steel Wires under Different Prestressing Levels

High-carbon structural steel wires were prestressed to various levels in a plasma hydrogenation environment and then pulled in a slow strain rate test (SSRT). The effect of plasma hydrogenation under different prestressing levels on the material's tensile response and hydrogen embrittlement was noted. It was found that the ultimate tensile strength (UTS), yield strength, and ductility of the steel wire samples are decreased by plasma hydrogenation and prestressing levels. The more drastic decrease in the UTS, yield strength, and ductility is found in the plasma hydrogenated prestressing steel to a higher prestressing level. Moreover, the hydrogen embrittlement index of the steel wire samples is significantly increased by plasma hydrogenation and prestressing level. The highly plasma hydrogenated prestressing steel wire samples exhibit complete brittle fracture. A mixed mode of fracture, i.e., ductile and brittle, was observed at the surface of the plasma hydrogenated prestressing steel wire samples at lower levels. The hydrogen embrittlement areas at the fracture surfaces of steel wire samples are observed to increase with plasma hydrogenation and prestressing levels. More severe hydrogen cracking and blistering resulted in the fracture surfaces of plasma-hydrogenated prestressing steel wire samples with higher levels.

Experimental Study on Steel‒Concrete Composite Beams Strengthened by Externally Prestressed CFRP Strips

PDF HTML XML Export Cite reminder Experimental Study on Steel‒Concrete Composite Beams Strengthened by Externally Prestressed CFRP Strips DOI: 10.59238/j.pt.2023.01.004 Author: Affiliation: (Department of Construction Engineering, School of Civil Engineering, Tongji University, shanghai 200092, China) Clc Number: Fund Project: Article | Figures | Metrics | Reference | Related | Cited by | Materials | Comments Abstract:This paper mainly studies the mechanical properties of simply supported bridges of steel?concrete composite structures strengthened with externally prestressed CFRP plates. The introduction of the prestress of the CFRP plate from the support rods can not only apply prestress to the main beam but also provide an upward lifting force at the bottom end of the main beam to reduce the deflection of the original structure. Therefore, the CFRP board is prestressed by the support rods, which can improve the speed and efficiency of rein-forcement construction. The effects of the CFRP amount, prestress size, support rods amount and other parameters on the stiffness and bearing capacity of composite beams were studied by a static test of the scaled model. In the flexural test of the tensioned combination beam, by increasing the prestressing level and the number of CFRP plates, the flexural moment of inertia of the combination beam section was effectively improved, the reinforcement effect on the yield bearing capacity and ultimate flexural bearing capacity of the combination beam was obvious, and the reinforced specimens still had good ductility. For the third com-bination beam, a CFRP plate with a 15% prestressing level and 3 mm thickness was used for reinforcement. The ultimate load carrying capacity of the combined beam was increased by 47.9%; the yield load of the lower flange was increased by 39.8%; and the stiffness in the elastic phase was increased by 21.66%. Reference Related Cited by