Steel Deck Pavement Research Articles

A Condition Assessment Tool for Steel Bridge Deck Pavement Systems Based on Data Balancing Methods and Machine Learning Algorithms

The primary challenge in the operation of steel deck pavement systems lies in the inspection and assessment of their condition. Traditionally, manual inspection methods are employed. However, these approaches are not only time-consuming and labor-intensive but also prone to human error. As a result, integrating data-driven machine learning technologies into the evaluation of pavement systems presents a significant advantage in addressing these issues. This study proposes a decision-making tool for estimating the condition levels of steel bridge deck pavement systems by employing classification techniques. To address the issue of class imbalance in the dataset, the SMOTE algorithm is utilized. Additionally, seven different machine learning methods—Light Gradient Boosting Machine, Extreme Gradient Boosting, Random Forest, Adaptive Boosting, K-Nearest Neighbor, Multilayer Perceptron, and Logistic Regression—are applied for training. Comparative analysis reveals that the Light Gradient Boosting performs optimally, achieving classification accuracies of 0.841 and 0.929 on the original and synthetic datasets, respectively.

Development and characterization of anti-cracking epoxy asphalt for steel deck pavement

Despite being commonly utilized in long-span steel deck pavement, epoxy asphalt continues to encounter certain obstacles, including excessive strength and insufficient resistance to cracking. This study proposed a novel approach to incorporating epoxy-terminated polyurethane prepolymers (ETPU) as a toughener to prepare an anti-cracking epoxy asphalt binder. The reaction process, viscosity-time behavior, tensile properties, and dynamic mechanical features of the ETPU-modified epoxy asphalt binder were comprehensively evaluated through a series of tests. Additionally, the fundamental pavement performance, fracture resistance, and fatigue resistance of ETPU-modified epoxy asphalt mixtures were thoroughly assessed. The addition of ETPU can significantly enhance the damping properties of epoxy asphalt, while maintaining its strength and construction retention time without any significant compromise. The formation of a chemical bond between epoxy-amine molecules and asphalt molecules significantly enhanced the compatibility between the epoxy resin phase and asphalt, thereby improving its damping properties. Both the fracture resistane and the fatigue resistance of ETPU-modified epoxy asphalt mixtures were found to be superior to that of commonly used epoxy asphalt mixtures in engineering. The modification mechanism was ultimately derived through the integration of infrared spectral analysis, thereby presenting an economically viable and highly efficient toughening pathway for epoxy asphalt. Therefore, this study indicated a wide-ranging potential for application in the realm of steel bridge deck pavement.

Investigation on the Preparation and Performances of Epoxy-Modified Asphalt Binder and Its Mixtures.

Epoxy-modified asphalt binder has been widely used in steel deck pavement due to its excellent properties and it is a potential candidate for long life pavements. However, its short reserve time limits its widespread application in pavement engineering. Therefore, this work developed a novel epoxy-modified asphalt binder composed of a laboratory-made curing agent as a solution. Firstly, optimization of preparation temperature of this new material was studied to balance the requirements of enough construction time and the material strength and elongation. The epoxy-modified asphalt binder, prepared at the optimal temperature of 140 °C, had a reserve time exceeding 120 min, whereas the tensile strength and the elongation at failure were 2.22 MPa and 216%, respectively, which satisfied the standard requirements of paving epoxy material well. Secondly, the asphalt mixture property tests demonstrate excellent high-temperature rutting resistance, water stability and low-temperature anti-cracking ability. Additionally, the compatibility and colloidal stability of this epoxy-modified asphalt binder were analyzed in terms of microphase structure. The uniform microphase distribution of this binder showed by the laser confocal microscope observation in both short-term aging case and long-term aging case, indicates the great compatibility between asphalt and epoxy resin during paving process and service life. Furthermore, fatigue tests were conducted to evaluate the long-term durability. The fatigue life of epoxy-modified asphalt mixtures increased by 435%, 427%, 342%, and 276% under the stress ratios of 0.3, 0.4, 0.5, and 0.6, respectively, compared to those of SBS-modified asphalt mixtures. All these results indicate that the new epoxy-modified asphalt material is promising for applications in pavement engineering, especially suitable for long-life road pavement.

Using Deep Learning-Based Defect Detection and 3D Quantitative Assessment for Steel Deck Pavement Maintenance

Efficient distress detection and identification analysis are of great significances for long-span steel bridge deck pavement maintenance. This paper proposes a pavement distress recognition method based on road quality detection equipment and deep learning. Firstly, the sub-block image is used as the processing unit, and the three-dimensional image is divided into fracture surface element and background surface element. A pavement crack recognition network (PDRNet) based on convolutional neural network is proposed, which is used for automatic recognition of pavement background element and pavement crack element. Then, considering the pixel-level neighborhood characteristics of cracks in 3D pavement images, the PDRNet model is used to detect and quantitatively evaluate pavement cracks, which combines the crack elevation detection method to extract the complete contour of cracks in the crack surface element. Finally, the distress database containing three-dimensional markers is integrated into the pavement maintenance management platform. Results show that the PDRNet proposed in this paper has high prediction accuracy on the verification set and shows good robustness to various distress, and the average accuracy is above 88%. The established spatial-temporal integration platform overcomes the communication bottleneck between different types of data, and is important to improve the maintenance management level and predict the long-term development of distress.

Interfacial performance and bond-slip constitutive model between steel and modified polyurethane concrete composites

In recent years, ecology conservation optimization (ECO) modified polyurethane concrete is becoming popular in steel deck pavement areas. However, it is reported that the interface performance between steel and ECO concrete suffers a significant degradation caused by diurnal and seasonal thermal cycling. In this paper, the interfacial performance of steel and ECO concrete composites at different temperatures was investigated through four groups of oblique tests at the temperature of −10 °C, 15 °C, 40 °C and 60 °C. The digital image correlation (DIC) technique is used to measure the strain distribution. The results show that the interfacial shear strength and stiffness of the specimens decrease with the growth of temperature, while the ultimate relative slip increases. Based on regression analysis, the formulas for calculating the interfacial shear strength, shear stiffness, and ultimate relative slip of steel and ECO concrete composites at different temperatures were established. A temperature dependent bond-slip constitutive model was proposed then by considering the temperature dependency of model parameters, which shows great accuracy in describing the bond-slip behavior between the steel and ECO concrete. Furthermore, a finite element analysis (FEA) model was established based on cohesive behavior, which agrees well with experimental results. Our research results can provide guidance for engineering applications of ECO concrete.

Study on Temperature-Dependent Uniaxial Tensile Tests and Constitutive Relationship of Modified Polyurethane Concrete.

Modified polyurethane concrete (MPUC) is a new material for steel deck pavements. In service, the pavement is often cracked due to excessive tensile stress caused by temperature changes. In order to study the tensile properties of MPUC in the diurnal temperature range of steel decks, uniaxial tensile tests of MPUC were carried out at five temperatures. Three kinds of specimens and a novel fixture were designed and fabricated to compare the results of four different tensile test methods. The deformation of the specimen was collected synchronously by two methods: pasting strain gauge and digital image correlation (DIC) technique. Based on the experiment, the tensile mechanical properties, failure modes, and constitutive relations of MPUC were studied under the effect of temperature. The research results show that the novel fixture can avoid stress concentration. By observing the fracture surface of the specimens, the bonding performance is great between the binder and the aggregate at different temperatures. The tensile strength and elastic modulus of MPUC decrease with increasing temperatures, while the fracture strain, and fracture energy increase with increasing temperatures. The formulas of temperature-dependent tensile strength, fracture strain, and elastic modulus of MPUC were established, and the constitutive relationship of MPUC is further constructed in the rising stage under uniaxial tension. The calculation results show good agreement with experimental ones.

An Experimental Study on the Flexural Performance of a Steel-ECC Composite Bridge Deck Sheet in the Negative Moment Zone

This paper seeks to solve the problem of orthotropic anisotropic steel deck pavement being prone to damage and fatigue, and to study the negative moment performance of steel-ECC concrete composite deck slabs. In this work, four groups of eight specimens were designed for the negative moment four-point bending test study, which included four variables of two ECC slab thicknesses and two bolt spacings. By analyzing the damage mode, crack distribution characteristics, bending load capacity, load-deflection curve, and load-strain curve, the effects of different ECC slab thicknesses and bolt spacings on the bending performance, deformation capacity, and cracking behavior of the steel-ECC composite bridge deck were investigated. The test showed that the combined structure of the ECC and steel plate showed good integrity and good ductility under a negative bending moment, and the damage mode of the member was pure bending of a section of the ECC with concrete cracking damage. When the thickness of the ECC plate increased from 50 mm to 75 mm, the ultimate flexural load capacity of the specimen increased by 92.6%, and when the distance between bolts was reduced from 200 mm to 150 mm, the ultimate flexural load capacity of the specimen increased by 13.4%. The increase in the ECC layer thickness increases the ultimate bearing capacity of the specimen significantly, and the decrease in the bolt spacing increases the ultimate bearing capacity of the specimen less.

Influence of short-term heat treatment on the second-order curing epoxy tack coat in steel deck pavements

Second-order curing epoxy tack coat (SCETC) is widely used as a waterproof bonding layer on epoxy steel bridge deck because it solves the problems of inadequate bonding and damage caused by the construction machine at the same time. In this paper, simulated short-term heat treatment (SHT) was carried out on SCETC after first-order curing. The reaction process and microstructure evolution of SCETC before and after SHT were analyzed by Fourier transform infrared spectroscopy, differential scanning calorimetry, and polarized light microscopy. The influence of SHT on mechanical properties of SCETC was comprehensively analyzed through tensile test, pull-off test, bonding behavior test and shear resistance test. The SCETC reaction process before and after SHT was revealed for the first time in this paper. At room temperature, amine curing agent (ACA) reacts with epoxy groups, and latent curing agent (LCA) dissolved in ACA gradually seeded out as fibrous crystals. Under the action of the high temperature of hot mixture, the LCA crystals melts and further reacts with the residual epoxy groups. When the melt volume-flow rate (MFR), tensile and pull-off properties of SCETC were compared before and after SHT, the two-stage curing mechanism of SCETC was further deduced. The fibrous LCA crystals seeded out during first-stage curing can enhance the solidified material. The LCA crystal melts under SHT, and its strengthening effect on the solidified material weakens or even disappears. Based on the unique reaction process of SCETC, the effective bonding time of SCETC under different curing conditions can be further determined by testing the bond performance between steel and epoxy asphalt concrete (EAC), and provide guidance for field construction. The effective bonding time of SCETC are 24 h at 60 °C, 48 h at 40 °C and>72 h at 23 °C, respectively.

Influence of resin asphalt pavement on stress behaviors of double-side welded rib-to-deck joints in orthotropic steel decks

Resin asphalt is one of the best choices for steel deck pavements owing to its excellent performance characteristics, such as high rigidity, excellent high-temperature stability, and convenient construction. Recently, resin asphalt has been increasingly used in orthotropic steel decks (OSDs), significantly influencing their stress levels. To determine the effect of a resin asphalt pavement on the stress behaviors and fatigue performance of double-side welded rib-to-deck (RTD) joints, experimental and numerical approaches were combined. A full-scale OSD specimen with a steel deck pavement was fabricated and tested under different temperature conditions. The experimental results indicated that the transverse bending rigidity of the deck could be improved by laying the resin asphalt pavement, and the stress ranges of the double-side welded RTD joints were significantly reduced. The stress behaviors of double-side welded RTD joints are sensitive to the pavement temperature. Thus, the stress ranges of the double-side welded RTD joints increased significantly with the temperature of the resin asphalt pavement. Furthermore, the numerical results showed that the maximum equivalent stress range of the double-side welded RTD joints occurred at crack type T2, under the transverse loading location of e = −150 mm. The equivalent stress range of the four crack types in the double-side welded RTD joints decreased significantly as the thickness of the resin asphalt pavement increased. The findings of this study suggest that the influence of resin asphalt pavements and their temperature effect must be considered to accurately evaluate the fatigue performance of RTD joints.

A Novel Cold-Mixed Epoxy Concrete and Its Comparison with Hot-Mixed Epoxy Asphalt Concrete

A novel cold-mix epoxy (CME) concrete was developed to meet the urgent demand of quick maintenance in long-span steel deck pavement. Considering that the CME is a thermosetting resin, a differential scanning calorimeter (DSC) was employed to evaluate the curing behavior of the CME binder. Dynamic mechanical analysis (DMA) was used to investigate the viscoelasticity of the CME binder. The semicircular bending test and the three-point bending test were used to evaluate the crack resistance of CME concrete. Long-term performance was investigated by comparing the fatigue behavior of the CME concrete and hot-mixed epoxy asphalt (HMEA) concrete. The results showed that the curing reaction order of CME is similar to that of HME (hot-mixed epoxy) and the activation energy of CME is slightly higher than that of HME which means that the reactivity of the latter is higher. The bimodality that occurs in tanδ curve means that there are two phases existing in the CME and HMEA microstructure, while the secondary phase ensures that the CME and HMEA have good damping behavior. CME concrete has a better crack resistance than HMEA concrete at low temperature, and a similar crack resistance compared with HMEA concrete at high temperature. From the residual ratio of flexural stiffness after 1 million load cycles, the CME concrete shows better fatigue resistance than the HMEA concrete.

Experimental Study on the Interfacial Bonding Performance of a New Steel Bridge Deck Interface-Bonding Agent

The construction of steel deck pavements is still considered difficult worldwide, and interfacial bonding is a major factor influencing this construction. With the recent developments in the field of pavement materials, high-performance cement-based concrete is used to construct steel bridge deck pavements. However, ensuring adequate interface-bonding strength remains particularly complex and difficult. In this study, with the aim of striking the right balance between rigidity and flexibility, an interface-bonding material was formed using modified epoxy resin, cement, and rubber powder. Polymer lattice porous concrete was used as the paving material, and the interface-bonding effect was studied experimentally by employing three methods using the material: pull-off, dual-interface shear, and flexural tensile tests. The results showed that (1) the interface pull-off strength was higher than 4 MPa, that is, higher than twice that of epoxy asphalt pavements used currently on steel bridge decks, and the failure surface was located on the pavement material rather than on the bonding interface; (2) the interface flexural strength and tensile strength were significantly higher than those of epoxy asphalt at room temperature and those of the ordinary epoxy resin; (3) the dual-interface shear strength was nearly four times higher than that of epoxy asphalt. Therefore, the modified epoxy resin composite interface-bonding material suggested in this study is an excellent bonding material that can serve as a reference for interface-bonding of steel bridge deck pavements.

Experimental Study of the Factors Influencing the Performance of the Bonding Interface between Epoxy Asphalt Concrete Pavement and a Steel Bridge Deck

The bonding between pavement and a steel bridge deck is a key component affecting the structural integrity of steel deck pavement and delamination is a major cause. The bonding interface of steel deck pavement was systematically investigated to evaluate the interactive influences of factors, such as the air void of the asphalt concrete pavement, the surface roughness of the steel deck, the thickness of the zinc-rich epoxy primer, and the waterproof bonding membrane, on the bond strength of the pavement interface, through simulated loading, brine immersion, pull-off, and interface observation experiments. The results show that a low air void (<3.0%) was a necessary condition for the corrosion resistance and bonding reliability of the steel deck pavement structure, and a zinc-rich epoxy primer provided an additional guarantee for corrosion resistance of the steel deck pavement; additionally, the combination of steel deck plate roughness in the range of 120–140 μm and zinc-rich epoxy primer thickness in the range of 80–110 μm led to a high bond strength, which was also conducive to the corrosion resistance of the steel bridge plate. The steel deck pavement structure should be designed through combinatorial optimization of multiple factors to create an integrated waterproof and anticorrosion bonding system.

Influence of Short-Term Heat Treatment on the Second-Order Curing Epoxy Tack Coat in Steel Deck Pavements

Influence of Short-Term Heat Treatment on the Second-Order Curing Epoxy Tack Coat in Steel Deck Pavements

Influencing factors and mechanisms of blistering in epoxy asphalt mixtures for steel deck pavements

The epoxy asphalt mixture applied on a steel bridge deck usually experiences blisters in summer construction, which seriously shortens the service life of the pavement structure. In order to reduce the frequency of blisters and improve the construction quality, three main influencing factors of blistering (environment temperature, curing time of epoxy asphalt mixture, and initial debonding area) and the deformation characteristics and growth mechanisms of blistering were investigated. A simulation test of pavement blistering was first designed, and the test parameters were obtained by analyzing the thermodynamic process of droplet evaporation; then, the displacement sensor was used to measure the growth of blistering, and finally the influence of the three main factors on blistering for pavements was analyzed. The main conclusions are as follows: (a) temperature has the greatest influence on the blistering growth, while the initial debonding area has the least influence on the blistering growth; (b) blistering growth in a pavement layer reaches its limit within 30 to 90 min during the curing period; (c) the deformation of blistering is a rapid process if the ambient temperature exceeds 30℃; and (d) the ability of epoxy asphalt mixtures to resist deformation positively correlates with curing time. It is hard to observe blistering at low temperature (30℃) if the epoxy asphalt mixture was paved for more than 48 h. Finally, effective measures would be proposed for improvement from three dimensions are respectively prevention, detection time, and detection method.

Response analysis of orthotropic steel deck pavement based on interlayer contact bonding condition

In this research the interlayer contact condition was considered between the adjacent layers of orthotropic steel deck pavement, and an interface contact bonding model was applied to simulate the interlayer bonding condition and evaluate the response of deck pavement under vehicle loads. An advantage of this model is that it can simulate not only the full-bond condition but also the debonding condition at somewhere between adjacent layers. The responses of the orthotropic steel deck pavement were calculated and analyzed by the model, and it found that this model is reasonable and credible to evaluate the responses of the deck pavement comparing with the previous researches. The full-bond condition was an ideal condition between adjacent layers, which was prone to underestimate the responses and deformation of the deck pavement. Moreover, the position and size of the disengaging area have a notable influence on the tensile strain at the top of SMA layer and the bottom of GA layer, and the tensile strain of them also increase with the increase of the disengaging area. Finally, the responses of the steel deck pavement changed obviously when the vehicle speed increase, so the suitable speed limit may reduce the responses and deformation for prolonging the service life of the orthotropic steel deck pavement.

Deformation recovery characteristics of asphalt pavement material on steel bridge decks under nondestructive conditions

The composition and properties of high-performance asphalt materials for steel bridge deck pavements are quite different. At present, research on the properties of steel bridge deck pavements mainly focuses on the strength law and damage behavior at the loading stage; however, little research exists on the deformation recovery characteristics of materials during unloading. In order to evaluate the deformation recovery ability of steel bridge deck pavement materials in the unloading stage, the repeated creep and step-load recovery test is herein put forward as an alternative to the deficient creep step-load test. The internal stress and residual strain of three typical steel deck pavement materials—a gussasphalt mixture, an epoxy asphalt mixture, and a stone mastic asphalt mixture—were tested. By comparing the results of CSR test and RCSR test, it is found that RCSR test is more suitable for steel bridge deck paving materials.The recovery modulus under three different creep stress levels was calculated to evaluate the ability of the three materials to drive deformation recovery. At the same time, based on the basic theory of viscoelasticity, the fitting parameters of creep compliance were determined, and the strain recovery rates of three kinds of materials under different interval times were calculated. The results reveal that the recovery modulus of the epoxy asphalt mixture is the largest, about 7 times and 4 times as much as stone mastic asphalt and gussasphalt, respectively, and the self-driving ability of epoxy asphalt mixture is better than that of gussasphalt and stone mastic asphalt. Moreover, within the same time interval, the strain recovery rate of the gussasphalt mixture is the fastest; in 3.6 s, the strain recovery rate can reach 82%.

Experimental study of the deformation recovery characteristics of steel deck pavement materials

Steel deck pavement material and steel decks require good cooperative deformation ability. The deck system of a long-span steel bridge is flexible, and its pavement is repeatedly subjected to tensile stress and compressive stress; therefore, the steel deck pavement material requires a strong capability to recover from the deformation. The internal stress of the pavement material is the force driving its deformation and recovery. In this study, based on the characteristics of steel deck pavement materials, a repeated creep progressive loading recovery test (RCSR) was proposed to measure the internal stress. In addition, the theoretical solution of the internal stress of the material in the nondestructive stage was derived. The test results show that the RCSR test is effective and accurate in determining the internal stress of the steel deck pavement materials. The recovery modulus of a material can be defined by measurement and calculation of the internal stress. Moreover, different materials can be used to characterize the recovery modulus of a steel deck. Based on the theoretical solution of internal stress, the theoretical solution of the recovery modulus was deduced and calculated. The test value was used to determine the accuracy of the theoretical solution of the recovery modulus. The results were used to verify that the recovery modulus is the inherent property of the material in the nondestructive stage and is not affected by the additional conditions of the test. The internal stress and recovery modulus of three typical steel deck pavement materials were measured and calculated in this study. The test results show that an epoxy asphalt mixture has the largest recovery modulus, which indicates that under the same stress level, the internal driving force for the deformation recovery of this mixture is greater, and its deformation recovery ability is strongest.

Design and Performance Investigation of Drainage Ultra-Thin Wearing Course Based on Diatomite-Supported Epoxy-Modified Asphalt Mixture

Abstract The high-performance epoxy resin–modified asphalt has been widely applied in the development of steel deck pavement and roads with heavy traffic. However, the poor compatibility between the epoxy resin and matrix asphalt has never been solved completely. In this study, epoxy resin was supported on diatomite with a large pore structure, so that epoxy resin was evenly dispersed into asphalt for improving the compatibility. The diatomite-supported epoxy-modified asphalt (DEA) binder was prepared and applied to the drainage ultra-thin wearing course mixture (DUWM). Six different DEA-DUWM were designed with a 2.36-mm sieve size, which was the key sieve size. The general asphalt content was calculated by the asphalt film thickness test. The optimal asphalt content was determined by the Cantabro test and the Schellenberg binder drainage test. The best curing time was determined by the Marshall test. Taking the Japanese epoxy resin–modified asphalt (TAF) as the comparison group, the high-temperature rutting test, low-temperature bending beam test, immersion Marshall test, freeze-thaw splitting test, immersion Cantabro test, water seepage test, surface friction coefficient test, and Manual sand laying test were carried out for DEA-DUWM and TAF-DUWM under the same gradations and test conditions. The results indicate that DEA-DUWM has excellent high-temperature rutting resistance; the maximum low-temperature bending strain is nearly 25 % less than that of TAF-DUWM, but the low-temperature cracking resistance can still meet the specification requirements of China. The addition of diatomite and the air void of the mixture have an effect on the low-temperature anticracking performance of DUWM, and DEA-DUWM has a remarkable high-temperature and low-temperature moisture resistance, drainage, and skid resistance. The air void of the mixture has a great influence on the freeze-thaw resistance of DUWM. The asphalt type has a marginal effect on the drainage and antiskid properties. It is suggested that the DUWM design’s target air void content should not be less than 17 %, and it can be improved properly in an area with heavy rainfall.

Study on performance of new type cold mix epoxy asphalt and mixture for steel deck pavement

In order to improve the performance of steel bridge deck pavement material, improve the construction efficiency and reduce the cost of steel bridge deck pavement, this paper introduces a new type of cold mixed epoxy asphalt, and studies the mechanical properties and curing law of the material through Marshall test. The results show that it has good mechanical properties, and the curing days at room temperature are 2-3 days. Based on the test data, compared with the United States and Japan, this paper analyzes the remarkable characteristics of the cold mix epoxy asphalt, which has the advantages of normal temperature construction, long retention time, good operability, low construction cost, less curing days, early opening of traffic, low material cost and reducing energy consumption. If it is used as the paving material for steel bridge deck, it has a broad application prospect.

Static and fatigue test on lightweight UHPC-OSD composite bridge deck system subjected to hogging moment

A cost-effective Lightweight Composite Bridge Deck (LCBD) system, including Orthotropic Steel Deck (OSD) and lightweight Ultra-High Performance Concrete (UHPC) layer is proposed to increase the stiffness and fatigue performance of conventional OSD. Static and fatigue tests on two full-scale strip models subjected to four-point bending were carried out. The static nominal cracking stress of the UHPC layer with reinforcement spacing of 80 mm is 24.59 MPa, while it increases to 35.68 MPa when the reinforcement spacing is reduced to half (40 mm); both values are far greater than the nominal stress of 12.7 MPa obtained in the prototype bridge. Increasing the reinforcement ratio can increase the bending stiffness of LCBD and decrease the tensile strain of the UHPC layer, while the change in range is relative slight. Furthermore, the flexural strength of UHPC and the reinforcement ratio are important factors affecting the fatigue life of the UHPC layer. When the reinforcement spacing increases from 40 mm to 80 mm, the fatigue life of the UHPC layer still satisfies related code requirements. Thus, for reduction in the engineering cost and construction complexity, the reinforcement spacing can be set as 80 mm. However, the application of the UHPC as the steel deck pavement, the rib-to-diaphragm welded joint is still prone to fatigue cracks. In addition, the existing S-N curves are hard to directly use for fatigue life prediction of the UHPC layer because of the great differences in the definition of stress level and evaluation index of failure in the fatigue test, which need to be modified in further studies.