Prestressing Strands Research Articles

Experimental and numerical analysis of strengthening prestressed concrete cylinder pipes using a post-tensioning method

Prestress loss caused by broken wires can lead to a decline in the carrying capacity of prestressed concrete cylinder pipes (PCCPs). The strengthening of PCCPs using a post-tensioning method is becoming more and more widely utilized to restore strengthened pipes to the needed design capacity and to withstand combined loads. There is no need to drain the pipe during strengthening construction, and this strengthening actively replenishes the prestress loss caused by wire breakage at a cost-effective price. To verify the strengthening effect of this method, a full-scale test and its corresponding three-dimensional finite-element model were established. A three-dimensional numerical model of three continuous prototype pipes was established and accounted for the particularity of the bell and spigot. The numerical model of prestressing wires was optimized in two aspects, which was more in line with the actual situation. The spiral winding method instead of single winding was adopted to apply prestress, and the prestressing wires with a broken point were partitioned into two separate areas due to the bond quality between the mortar coating and the wires. The simulation and the full-scale test both contain the five processes of strengthening with external prestressed strands as follows: pressurized to working pressure→breaking the prestressing wires until visible cracks propagate→gradual depressurization to artesian pressure→the tensioning operation of strands→and pressurized to design pressure. A sensitivity analysis of the related factors of strengthening was performed through finite-element simulation to provide a better understanding of the design. The simulation results were consistent with the data on the full-scale test and indicated the rationality of this process. The strengthening of PCCP with a post-tensioning method can meet the design demand and is a feasible strengthening method. The working pressure and control coefficient of tensioning have the most significant impact on the strengthening effect. Technical recommendations and a better understanding of the application of the post-tensioning method on PCCP are provided in this study.

Response Characteristics of Pre-Stressed Strand Cables Subjected to Low-Velocity Impact: Experiment Test

This paper introduces some experimental data measured from 63 impact tests of pre−stressed strand cables. The test specimens consist of seven steel wires that have a length equivalent to 100 times the outside diameter. To ensure consistency with the engineering service status, the strand cables are fully installed in a specially designed device and are axially pre−stretched to 0% to 40% of the ultimate bearing capacity before being subjected to lateral impact. The mass of the indenter is 50.34 kg, and the maximum impact velocity reaches 13 m/s. Two dimensionless variables, axial force and input kinetic energy, are used to control the experimental parameters. The recorded test data show that input energy and pre−stress level are the key factors governing the impact behavior, which is mainly characterized by plastic deformation controlled by the combination of tension and flexure, and the dynamic fracture concentrated in the impact zone is controlled by the joint effects of compression, tension and shear. As the impact energy increases, the dynamic mode of the test specimen changes from elastic rebound to plastic deformation, and finally evolves into fracture of some or all steel wires, which correspond to slight, partial and total loss of pre−tension, respectively. An increase in the level of pre−stress will significantly reduce the critical displacement of the structural failure but has little effect on the critical failure energy. The present paper provides a basic experimental data and mechanical analysis framework for the analysis, design and evaluation of the mechanical behavior of strands under accidental lateral impact.

Prediction of corrosion-induced retraction slip of prestressing strand in pre-tensioned concrete beams

An experimental study is conducted on ten pre-tensioned concrete (PC) beams with different local corrosion degrees and positions to investigate the effect of corrosion on the transfer length and retraction slip of prestressing strand. A novel model, incorporating the combined effects of Hoyer effect and strand corrosion, is proposed to predict the corrosion-induced retraction slip of prestressing strand in PC beams. The accuracy of the proposed model is validated by experimental results. Results indicate that the transfer length and retraction slip of prestressing strand increase with the increase of corrosion loss, and this effect weakens when the local corrosion position changes from the end of the beam to the mid-span of the beam. The transfer length and retraction slip of prestressing strand increase by 30.6% and 5.18 times, respectively, once the corrosion loss reaches 33.5%. The retraction slip of corroded prestressing strand is positively correlated with the diameter of strand, but negatively correlated with the compressive strength of concrete. The diameter of strand, compared with the compressive strength of concrete, has a more significant effect on the corrosion-induced retraction slip.

The bond-slip constitutive model of retard-bonded prestressing steel strand

The bond property between the retard-bonded prestressing steel strand (RPSR) and concrete is the basis of mechanical behaviour of the retard-bonded prestressed concrete structure, which is of great significance to the theoretical design and engineering application of the retard-bonded prestressed concrete structure. In this paper, the center pullout test of RPSR was carried out, considering the influence of steel strand diameter, concrete strength, bond length and non-bond length. The results showed that the bond strength and peak point slip of RPSR are larger than that of the ordinary steel strand under the same condition. The residual branch of RPSR bond-slip curve was approximately a downward sloping sinusoid. The cylinder specimen had better confinable effect and was less prone to splitting failure. The conditions for pullout failure of RPSR were proposed. By establishing local coordinate system, the whole process bond-slip constitutive model of RPSR was proposed in this paper. It was found that the proposed model was in better agreement with the experimental results, which can reflect the whole process of the bond-slip relation between the RPSR and the concrete.

Research on Flexural Bearing Capacity of Reinforced Hollow Slab Beams Based on Polyurethane Composite Material Positive and Negative Pouring Method

In order to explore the construction technology of prestressed steel strand–polyurethane cement composites for strengthening hollow slab beams, two reinforced test beams (L1, L2) and one unreinforced test beam (L0) were subjected to flexural static load tests. The deflection, ductility, stiffness, strain, and bearing capacity of each test beam were used to summarize the influence of different reinforcement techniques on the flexural performance of hollow slab beams. Research shows the prestressed steel strand–polyurethane composite material was well-bonded to the hollow slab beam, which effectively inhibits the development of concrete cracks and delays the damage process of hollow slab beams, that the reinforcement effect of the test beam L1 under the reverse pouring process was remarkable, and the bending performance of the test beam L2 under the forward pouring process of the simulated real bridge was good, which was much better than that of the unreinforced beam L0. The use of tensile prestressed steel strands and forward casting of polyurethane–cement composite materials effectively improved the flexural bearing capacity of the test beams, and this reinforcement process can be further extended to engineering applications.

Monitoring of prestressed concrete beam under corrosion using embedded piezo sensor based on electro-mechanical impedance technique

<h2>Abstract</h2> The service life and durability of the prestressed concrete (PC) structures mainly depend on the corrosion resistance of the prestressing strands, wires, or tendons. Once corrosion occurs in the strands, identifying the location and quantifying the phases of corrosion is a very challenging task. Thus, this paper presents a novel way to monitor the corrosion process in a PC beam using an embedded piezo sensor (EPS) based on the electro-mechanical impedance (EMI) technique. The accelerated corrosion tests were conducted on a PC beam in which EPS was attached to the prestressing wire inside the beam to monitor the changes in the EMI signature during the corrosion progression. Further, this study identifies the deterioration in mechanical changes such as stiffness, mass, and damping by extracting the equivalent structural parameters (ESPs) from the raw EMI signatures. Based on qualitative and quantitative results, it is found that the EPS effectively senses the changes and identifies the different phases of corrosion. Also, the ESPs are realistically measuring the material deterioration under corrosion. Hence, the EMI technique based on EPS in structural health monitoring of PC beam can accurately assess the deterioration under the effect of corrosion.

Experimental and numerical study on seismic performance of precast segmental CFST bridge columns with non-uniform prestressed steel tendons

A precast segmental concrete-filled steel tube (PSCFST) bridge column set with non-uniform (external and internal) prestressed post-tensioned (PT) steel strands was proposed, then the seismic performance of this type of bridge column was researched in this paper. The external prestressed steel strands are arranged on the outside of the bridge column to provide re-centering force, which can facilitate to observe the damage state of the PT tendons and be rapidly replaced. Pseudo static test was carried out on three scaled specimens, including a reference monolithic reinforced concrete (MRC) column and two PSCFST columns. The test results showed that both PSCFST columns have good seismic and resilience performance, with no visible damage and little residual displacement. The PSCFST column with external and internal PT strands shows better self-centering performance. The external prestressed steel strand will yield earlier than the internal, so it can be used as an early damage warning device for the PSCFST column. Then, a detailed finite-element (FE) model was established and validated using the test specimen. The finite element calculation results are in good agreement with the experimental results, indicating that good applicability of the established FE model. Furthermore, based on the validated FE model, the non-uniform arrangement position and initial prestress level of the prestressed PT steel strand were analyzed. That is, analysis was conducted to investigate the seismic and resilience behaviors of the PSCFST specimen with different arrangements of PT strands and different ratios of initial prestress of the internal and external PT strands. Analytical results indicated that increasing the initial prestress value of the external steel strand can increase the bearing capacity of the PSCFST specimens, while the initial prestress of the external prestressed steel strand has little effect on the initial stiffness, drift ratio, or accumulative energy dissipation. Furthermore, allocating more external PT strands can increase the bearing capacity and initial stiffness of the PSCFST specimen, while decreasing the drift ratio.

Study on the Probability Distribution of Pitting for Naturally Corroded Prestressing Strands Accounting for Surface Defects

One of the most urgent scientific needs from a technical and economic engineering point of view is the assessment of concrete structures suffering corrosion deterioration. However, the pursuit of this target in the case of corroded prestressed concrete (PC) members is hindered by the lack of (i) consolidated simplified formulations to be used in the engineering daily practice and (ii) works investigating the uncertainties in the correlation between the damage induced by corrosion and the structural resistance. To this aim, the present study adopts a 3D-scanning technique for the pitting morphology evaluation of several corroded prestressing strands retrieved from 10-year-old PC beams. First, the probabilistic distributions of penetration depths have been investigated. Second, the pitting factors α and Ωi have been proposed and discussed to quantify the level of corrosion in longitudinal and transversal direction, respectively. Finally, correlations have been derived between the maximum and average penetration depth as a function of the level of corrosion and the surface defects mapping has been carried out on the corroded PC beams. The results show that the penetration depth of strands subjected to chloride-induced corrosion can be best fitted by a lognormal distribution function. Additionally, the simultaneous consideration of longitudinal and transversal pitting factor is found out to be essential for an exhaustive comprehension of pitting corrosion. Moreover, the outcomes highlight that the presence of longitudinal splitting cracks plays a fundamental role in the corrosion spatial variability of prestressing strands.

A simplified stress–strain relationship for the mechanical behavior of corroded prestressing strands: The SCPS‐model

AbstractThis article presents a simplified stress–strain relationship for the definition of the mechanical behavior of prestressing strands subjected to chloride‐induced corrosion, named SCPS‐model (Simplified Model for Corroded Prestressing Strands). The constitutive law adopts the equivalent spring model, that reproduces the overall behavior of a corroded strand by summing the contributions of each wire, assumed as a spring working in parallel to the others. The SCPS‐model is designed for the application in the daily engineering practice; to this aim, it is based on a single input parameter that is the maximum penetration depth of the most corroded wire. Following a detailed description of the model formulation and parameters, the article shows the validation of the stress–strain relationship through several comparisons with experimental tensile test outcomes coming from scientific literature. Finally, a statistical analysis of the dimensionless ratio of experimental and analytical results in terms of ultimate corroded strength and strain is carried out to demonstrate the effectiveness of the SCPS‐model. Concluding, the accurate and safe side prediction of the residual mechanical behavior of corroded prestressing strands is proposed using the SCPS‐model.

A convenient cable tension estimation method simply based on local vibration measurements to fit partial mode shapes

To apply the tension estimation method based on effective vibration lengths, it has been clarified that the installation of at least one sensor near the high end of a stay cable or a suspender of arch bridge is necessary for attaining good accuracy. Efforts are made in this research to release such an undesirable requirement that may greatly hinder popular applications of this method. re-examination of formulations first reveals that the half-wavelength, rather than the whole effective vibration length, of each considered mode is actually needed in the mode shape based method. Therefore, cable tension estimation simply using local vibration measurements to fit partial mode shapes is a viable alternative as long as the accuracy in determining the half-wavelengths of all the chosen modes can be ensured. Numerical analyses with the finite element models for two stay cables are then conducted to investigate the appropriate covering range of local measurements and the preferred choice of modes. Following those guidelines, the experimental results with a pre-stressed strand are further analyzed to demonstrate that excellent accuracy in tension estimation for the experimental strand with slenderness similar to a short stay cable can be achieved when 1/2 and 1/3 covering ranges are adopted. Finally, by taking vibration measurements on a real stay cable with a length of 100 m, the accuracy for the tension value estimated from 1/4 covering range is persuasively validated with a difference less than 1 % compared to that estimated from full coverage.

GFRP composite bars for splicing prestressed precast concrete piles: Design and experimental investigation

Glass Fiber Reinforced Polymer (GFRP) composite bars were investigated in this study as a corrosion-resistant dowel for splicing prestressed precast concrete piles (PPCPs). In addition to their durability and good mechanical performance, GFRP bars show cost advantage when compared to other corrosion-resistant material. Using available design guides for FRP-reinforced concrete sections, a typical epoxy bonded dowel splice using GFRP bars was designed for an 18 × 18 in (457 × 457 mm) PPCP. In order to validate the adopted design procedure and to investigate the effectiveness of GFRP reinforcing bars as bonded dowels for pile splice design, 10 full-scale PPCP specimens of 18 × 18 in (457 × 457 mm) cross-section with a total length of 28 ft (8.5 m) were designed, fabricated, and tested at the Florida Department of Transportation (FDOT) Structures Research Center. In these specimens, three different materials for dowels; GFRP reinforcing bars, Carbon Fiber Reinforced Polymer (CFRP) strand, and traditional carbon-steel reinforcing bars were used in combination with CFRP and steel prestressing strands for PPCPs for both unforeseen and preplanned drivable splicing cases. The focus of this study was on the flexural performance at the splice. The experimental results show that the proposed epoxy GFRP dowel pile splice can match the required design flexural resistance for a preplanned PPCP carbon-steel pile splice. The laboratory tests performed in this research validates the new design procedure for the GFRP dowel splice. The design flexural resistance for the GFRP dowel splice calculated by the new procedure provides 68 % of 245 kip-ft (332.2 kNm), the flexural resistance required by the FDOT design specifications for mechanical preplanned splices. This research will help to improve the standard designs and construction specifications.

Damage simulation and strengthening of main girder after the fire-induced fracture of stay cables during construction

The fire-induced fracture of stay cables damages the main girder of a cable-stayed bridge during the cantilever construction. A scaled-down girder was designed in the laboratory to simulate the mechanical behavior of the damaged main girder. A special loading system, consisting of external prestressing strands and two actuators, was designed to simulate the damage of the main girder. A strengthening strategy, consisting of anchor bolts and steel plates, was presented to improve the stiffness and flexural capacity of the damaged girder. The results showed that the special loading system and the strengthening strategy could effectively achieve their respective goals. After strengthening, the vertical and transverse bending stiffness and the positive and negative torsional stiffness of the girder increased by 42%, 31%, 78%, and 68%, respectively, from those of the damaged girder. The findings of the present study can provide an effective basis for the damaged simulation of main girder after the fire-induced fracture of stay cables and the selection of strengthened method for damaged main girder during the cantilever construction.

Experimental Study on Seismic Performance of Precast Pretensioned Prestressed Concrete Beam-Column Interior Joints Using UHPC for Connection.

The traditional connections and reinforcement details of precast RC frames are complex and cause difficulty in construction. Ultra-high-performance concrete (UHPC) exhibits outstanding compressive strength and bond strength with rebars and strands; thus, the usage of UHPC in the joint core area will reduce the amount of transverse reinforcement and shorten the anchoring length of beam rebars as well as strands significantly. Moreover, the lap splice connections of precast columns can be placed in the UHPC joint zone and the construction process will be simplified. This paper presented a novel joint consisting of a precast pretensioned prestressed concrete beam, an ordinary precast reinforced concrete (RC) column, and a UHPC joint zone. To study the seismic performance of the proposed joints, six novel interior joints and one monolithic RC joint were tested under low-cyclic loads. Variables such as the axial force, the compressive strength of UHPC, the stirrup ratio were considered in the tests. The test results indicate that the proposed joints exhibit comparable seismic performance of the monolithic RC joint. An anchorage length of 40 times the strands-diameter and a lap splice length of 16 times the rebar-diameter are adequate for prestressed strands and precast column rebars, respectively. A minimum column depth is suggested as 13 times the diameter of the beam-top continuous rebars passing through the joint. In addition, a nine-time rebar diameter is sufficient for the anchorage of beam bottom rebars. The shear strength of UHPC in the joint core area is suggested as 0.8 times the square root of the UHPC compressive strength.

Flexural behavior of prestressed concrete-filled steel tubular flange beams

This research presents a numerical and analytical investigation on the structural characteristics of concrete-filled steel tubular flange beams (CFSTFBs) prestressed using steel strands under bending. CFSTFBs are found to benefit from higher flexural and shear strength compared to those of I-section beams with flat flanges. The geometrical configurations of these sections provide them with higher web local buckling resistance due to a larger flange depth-to-width ratio. A large number of existing structures, constructed with steel–concrete composite beams, need to be retrofitted due to many factors such as loss of strength as a result of service loads and environmental conditions. A potentially economical and feasible approach to strengthening these beams is upgrading them using steel prestressing strands. The finite element (FE) approach was utilized to develop a three-dimensional numerical model considering both material and geometrical nonlinearity. Accordingly, the effects of concrete strength, tubular flange shape and dimension, steel yield stress, and quantity and eccentricity of strands were included in the analysis. A simplified model, on the basis of the plastic stress distribution method (PSDM), was used to estimate the ultimate moment capacity. In order to visualize the influence of steel and concrete strength and tubular flange size on the moment capacity of CFSTFBs, several artificial intelligence (AI) algorithms were employed and a partial dependence analysis was also conducted accordingly. The ultimate capacities obtained by analytical and FE models, considering the effect of confinement, were verified by comparing the predictions with the results from experimental studies. Both analytical and FE results indicated that the prestressing strands are significantly capable of enhancing the stiffness and strength of CFSTFBs under flexural loading. It was demonstrated that the tube geometric properties can significantly control the overall performance of prestressed CFSTFBs. The results also indicated a negligible effect of the concrete compressive strength.

Long-term performance of a continuous box-girder bridge constructed using precast segments with wet ultra-high-performance concrete (UHPC) joints

Although the precast segmental construction (PSC) technique can relieve age-dependent difficulties and accelerate bridge construction as compared to the cast-in-situ construction (CSC) technique for long-span prestressed concrete box-girder bridges (LSPCBB), the ordinary concrete joints between adjacent precast segments are risky. In order to improve the bond strength at the joint interface and enhance structural reliability, ultra-high-performance concrete (UHPC) can be used to fill joints as a new cementitious material with high strength, ductility, and durability. Thus, the effect of the naturally cured UHPC shrinkage and creep on the bridge's long-term performance should be evaluated. The present study numerically investigates the long-term bridge performance constructed by the PSC technique with wet UHPC joints. One cast-in-place segment using the CSC technique is replaced by one precast segment and one cast-in-place UHPC joint using the PSC technique in the bridge model. A creep coefficient equation in an existing code and a shrinkage strain equation fitted from the test data for the UHPC are verified, and an equivalent temperature drop method is used for simulating pretension forces of the prestressing strands in the numerical model. Through comparison with the CSC technique, the technical advantages in reducing long-term deflection, rotation, prestress losses, and improving normal cross-sectional stresses are quantitatively highlighted for the UHPC enhanced PSC bridge.

Prestressed Concrete Box Girder with High-Capacity Strands-Monitoring and Analysis during Fabrication

Despite the attractive merits of high-capacity strands, the application in bridge girders is limited due to concerns, including concrete cracking, excessive stress, and cambers. An efficient and defect-free production is the first step to wide application. The objective of this research was to alleviate the production concerns of prestressed concrete bridge girders using high-capacity strands. A gigantic prestressed concrete box girder using 18-mm strands was produced; its entire fabrication process (from strand stressing to detension) was introduced. Sixteen temperature gauges were embedded in the girder to monitor the hydration of the large volume of concrete and the adjacent environmental temperature. Moreover, displacement transducers were used to measure the camber at detension; load cells were installed to monitor the variations of the prestressing strand tensile forces during fabrication. Monitoring and analysis showed that the timing of the detension is determined by the hydration of the concrete, the compressive strength of the concrete, and its modulus of elasticity or age. Since the tensile forces in strands are affected by the concrete’s internal temperature, the detension is conducted after the concrete temperature falls back (close to its initial value); otherwise, unfavorable and considerable prestress losses are caused. Finally, a 4-d detension was suggested since the hydration was not a concern at the time; the predicted prestress loss and camber were acceptable and the concrete material properties at 4 d satisfied the requirements.

Aspects affecting the nonlinear behavior of precast prestressed hollow‐core units failing in shear

AbstractDue to the extrusion manufacturing process, hollow‐core units in New Zealand do not have transverse shear reinforcement. The prestressing strands will not be fully developed near the ends of the hollow‐core units, which significantly affects the shear capacity and makes them prone to transverse and web cracking under deformation demands. In addition, initial end slip of the strands caused during cutting of the units in the production process may exacerbate this effect. This vulnerability of hollow‐core slabs was remarked during the 2016 Kaikōura earthquake, where an estimated 22% of the damaged buildings presented transverse cracking to hollow‐core units, sometimes accompanied by evident web cracking. The observed damaged, produced by earthquake‐imposed deformations, highlighted the urgency to advance the understanding of the behavior of hollow‐core floors. Subsequently, an experimental testing program was initiated to investigate the properties of extruded concrete and the shear strength of hollow‐core units under different shear span‐to‐depth or aspect ratios. The 200 mm deep specimens were loaded well beyond the peak shear force to study the postpeak behavior of the hollow‐core units. Additionally, the present study evaluates the effect of initial end slip of the prestressing strands on the pre and postpeak capacity of the units. The results obtained are compared against the formulations provided by commonly used design standards such as the New Zealand concrete standard NZS3101:2006, the ACI 318‐19, as well as the fib Model Code 2010 and the BS EN 1168:2005.

Analytical model for predicting prestress transfer bond-related parameters of 18 mm prestressing strands

The bond between prestressing strand and concrete is necessary for the composite-action of the two materials. This study develops an analytical model to investigate the bond performance of 18-mm prestressing strands. The model considers the concrete compressive strength for both conventional and self-consolidating concrete. It is then used to determine the short- (at prestress transfer) and the long-term (after all prestress losses) transfer length and strand end slip. The predicted short-term transfer length and strand slip values were validated with the experimental results obtained from several pretensioned concrete beams and girders, which had various geometric configurations, concrete compressive strength, and number of prestressing strands. The results showed that the model provided a reasonable prediction of bond performance. From the analysis of the predicted long-term transfer length and strand end slip values, the long-term transfer length is on average 33% longer than the short-term transfer length, whereas the increase in strand end slip is on average 24% from the short-to the long-term stage. Regardless of concrete compressive strength and concrete type (conventional and self-consolidating concrete), both the ACI-318 and AASHTO LFRD codes provided a conservative limit for the predicted long-term transfer length values.

Numerical and analytical studies of flexural behaviour of prestressed UHPC joints

This study numerically and analytically investigates flexural behaviour of precast ultrahigh performance concrete (UHPC) segments connected by post-tensioned prestressing strands with or without epoxy on keyed joint surfaces. The analytical formulas are proposed for calculation of joint opening load and ultimate flexural capacity, and a numerical model is established to investigate flexural behaviour of the jointed beam. The joint surfaces without epoxy are simulated by a pair of contact elements with a friction coefficient of 0.6. For the joint surfaces with epoxy, besides the contact elements, a spring element is defined for consideration of the epoxy and an optimized force–displacement relationship is first proposed and input for the spring property. The previous test data and data from one intact beam with low reinforcement ratio tested in the present study are used for validation of the analytical and numerical calculations. The numerical results agree well with the test results in terms of load-midspan deflection, load-joint opening displacement as well as failure modes. Based on the validated numerical model, the effect of number of prestressing strands and beam depth on the flexural behaviour of the prestressed jointed beam is investigated. This study will promote prestressed UHPC joints’ application in practical engineering.

Fatigue Behavior of Heavy-Haul Railway Prestressed Concrete Beams Based on Vehicle-Bridge Coupling Vibration.

Due to the demand for increasing trainload and enhancing some existing heavy-haul railways, the low reserve value of bearing capacity is a problem for the 32 m-span simply supported beam. The fatigue behavior of prestressed concrete beams in a heavy-haul railway loaded by 33 t and larger axle weight of trains was experimentally investigated. The experimental results of the fatigue behaviors, including fatigue deformation, crack propagation behavior, and strains of classical materials were obtained and analyzed. A fatigue behavior assessment model was established to investigate the residual stiffness and yield point degradation of the beams loaded by the trainload. The effects of train fatigue cycles and prestress loss on the residual stiffness and yield point degradation models of the beams were analyzed. The results indicated that the crack development process had three stages during the fatigue process: the derivative stage, gradual development stage, and fatigue failure stage. Trainload was the main external factor influencing the fatigue behavior of prestressed concrete beams. The increase in trainload accelerated the degradation rate of the residual stiffness of the beams and yield point, reducing the fatigue life. The prestressing strand was primarily used to delay the concrete cracking in the tension zone. When the beam was not cracked, the prestressed concrete beam showed good fatigue performance, and the degree of prestressing did not affect the fatigue life of the beams. When the maximum fatigue load exceeded the cracking load of the beam, prestress loss in beams became a critical issue that accelerated the degradation rate of fatigue strength and reduced fatigue life. The higher the fatigue damage degree, the more pronounced the effect of prestress loss on the fatigue strength of the beams. The fatigue failure of prestressed concrete beams occurred in the bottom tensile steel bar. Therefore, when the trainload of a heavy-haul railway is greater than the cracking load of the beam, it is recommended to strengthen the beam by prestressing and strictly control the trainload to avoid yield failure.