The dowel effect in hybrid bonded fiber reinforced plastic (HB-FRP) to concrete joints is difficult to quantify and make the anchoring joint instability. A new HB-FRP joint was built, which eliminates bonding between steel and FRP plates. Based on an empirical model of external bonding FRP (EB-FRP) to concrete joints and the new model of slip at debonding, the new unified bond-slip model of the HB-FRP joints is proposed. The parameters that affect the bond-slip model are analyzed. Pull-off tests are conducted for eight specimens with different numbers of mechanical fasteners, which has verified the proposed model. The load-slip relationship at the loaded end of the FRP plate was well predicted by the partial interaction numerical calculation and further verify the theoretical model.

This research produced five hybrid-bonded fiber-reinforced plastic (HB-FRP)-reinforced beam specimens, and different fatigue load amplitudes were used as parameter variables for the fatigue performance tests of the FRP–concrete interface. The results show that FRP sliding with the number of cycles can be roughly divided into fatigue initiation stage, fatigue development stage, and fatigue damage stage, and finally, because the load is too large and friction, pin, and bonding cannot provide a greater inhibition effect, FRP adhesive length is not enough to withstand the stripping load and failure. FRP slip increases with increasing fatigue load amplitude for the same number of fatigue cycles; for the specimens with fatigue damage, the interfacial stiffness of FRP–concrete decreases with the increase in the number of cyclic, and the rate of stiffness damage at the FRP–concrete interface accelerates with increasing fatigue load amplitude. For fatigue load magnitudes higher than 0.6, the slopes of fatigue bond–slip curves decrease with the increase in the number of cycles. When the fatigue load magnitude is lower than 0.4, the slope of the fatigue bond–slip curve increases with the number of cycles and is close to the slope of the monotonically loaded curve. Due to the difference in load class, the bond strength of HB-F-1 continues to decrease with the increase in fatigue times, decreasing by 26% after 100 fatigue cycles and decreasing to 7.33 MPa after 5000 fatigue cycles. The bond strength of the sample HB-F-2 first increased and then decreased with the increase in fatigue times. After 10,000 fatigue cycles, the bond strength decreased by 8%, and at 11,133,300 fatigue breaks, the bond strength of the sample HB-F-3 continued to increase with the increase in fatigue times. At 2 million fatigue load cycles, the bond strength increased to 7 MPa, far from reaching the peak strength. The empirical formulas for the fatigue life curve of HB-FRP-reinforced specimens under single steel fasteners are proposed.

Camber in high-speed railway prestressed concrete (PC) girders increases with service time and affects profile control, ride comfort, and durability; reliable long-term midspan camber prediction is therefore required. Building on established hybrid physics–data modeling and discrepancy-correction ideas, we present a monitoring-oriented two-layer strategy for long-term camber prediction. In the physics layer, a physics-informed neural network (PINN) is formulated in a quasi-static, stage-aware manner to capture the physics-consistent low-frequency trend governed by creep, shrinkage, prestress loss, and staged loading. In the data layer, an XGBoost model learns a bounded, measurement-level residual correction from monitoring features to account for additional effects not explicitly represented in the physics layer, without altering the underlying physics-driven trend. The approach is evaluated using monitoring data from five 1:4 scaled specimens of a 24 m post-tensioned simply supported box girder and is compared against a theoretical calculation and a standalone PINN. Across prediction stages and specimens, the proposed strategy reproduces the measured camber evolution more closely than the benchmarks while preserving physically plausible trend behavior and yielding more consistent errors among girders. These results indicate that, under the present scaled-specimen and independently calibrated setting, a stage-aware physics baseline combined with bounded residual correction can provide closer agreement with the observed camber evolution than the benchmark models under sparse-monitoring conditions. Its engineering applicability can be repeatedly demonstrated across girders with different construction-condition combinations after girder-wise calibration.

A three-dimensional time-dependent finite element model is developed to investigate the short-term and long-term mechanical behavior of prestressed concrete beams subjected to combined freeze–thaw deterioration, tendon corrosion, and sustained loading. The proposed framework integrates smeared cracking and tension stiffening of concrete with concrete creep and shrinkage, prestressing tendon relaxation, freeze–thaw-induced degradation of concrete mechanical properties, and corrosion-induced deterioration of reinforcing steel and prestressing tendons. These mechanisms are incorporated into a unified incremental time-stepping analysis to capture the progressive deformation and prestress loss of the beams. The model is validated against experimental results for corroded prestressed concrete beams, freeze–thaw-damaged concrete beams, and long-term sustained-loading tests. Parametric analyses are subsequently performed to investigate the effects of concrete strength, freeze–thaw cycles, tendon corrosion rate, and prestress level. The results show that increasing the concrete strength from C35 to C50 reduces the 1000-day long-term deflection from 24.1 mm to 18.0 mm. Freeze–thaw deterioration has the most pronounced effect: the 1000-day deflection increases from 13.0 mm at 0 cycles to 42.9 mm at 150 cycles. In contrast, increasing the tendon corrosion rate from 0% to 12% increases the 1000-day deflection only from 21.6 mm to 21.8 mm, although the corresponding long-term prestress loss increases from 188.2 MPa to 198.0 MPa. Increasing the prestress level from 0.45 f_ptk to 0.75 f_ptk reduces the long-term additional deflection from 11.4 mm to 8.8 mm. The results demonstrate that freeze–thaw deterioration and concrete time-dependent effects dominate the long-term deformation response, whereas the influence of tendon corrosion on global deflection is comparatively limited within the investigated corrosion range. The proposed framework provides a numerical approach for assessing the time-dependent mechanical response of prestressed concrete beams under combined environmental and mechanical deterioration.