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Transverse connection strengthening prestressed concrete T‐girder bridge is an effective method to enhance the integrality of the T‐girder bridge. In a previous work, a new kind of diaphragm transverse connections (DTCs) has been proposed and its validity has been proved. Aiming to study the influential parameters for the strengthening effect, finite element analysis is carried out based on a 30 m prestressed concrete T‐girder bridge in this study. The considered influential parameters are T‐girder spacing, T‐girder height, brace thickness, and installation location of the DTCs. The deflections and load distribution factors of the prestressed concrete T‐girder bridge are calculated to evaluate the impact of each parameter on the strengthening effect. Furthermore, the influence of brace thickness and T‐girder height on axial forces of the DTCs and connection force is studied. The results show that the strengthening effect with DTCs installed at midspan is the best option. With T‐girder height increasing, the deflections of the T‐girder reduce and the maximum load distribution factor increases. Besides, increasing the brace thickness of DTCs or decreasing the T‐girder spacing improves the strengthening effect. By comparing the axial force with the buckling critical force, it shows that the stability of the braces is adequate. Finally, design recommendations are given for the 30 m prestressed concrete T‐girder bridge strengthening.

The shear behaviors of reinforced concrete (RC) beams externally strengthened with engineered cementitious composite (ECC) layers were studied and the strengthening effect was evaluated based on a truss and arch model. The beams were designed without web reinforcement in the middle part and ECC was sprayed onto both sides of the beams to the designed thicknesses, which were 20 mm and 40 mm. A series of four-point bending experiments were conducted and analyzed. The development of the shear strain in each side of the beams was recorded by strain rosettes formed with three fiber Bragg grating (FBG) sensors. The thickness of ECC layers, reinforcement ratios, and shear span-to-depth ratios were considered and analyzed. This is an effective way to shear strengthen RC beams with ECC layers. The ultimate load of the strengthened specimen can be improved by 89% over the control specimen. Strengthening an RC beam into an under-reinforced beam should be avoided. The FBG sensors are suitable to measure and monitor the development of shear strain in the side of the strengthened specimen. Based on the truss and arch model, an evaluation of the shear strengthening effect was established and the results agree well with the experimental results.

To solve the problem of insufficient transverse connection of T-girder bridges, this paper investigated the strengthening method of two composite trusses symmetrically installed in mid-span. The composite truss included two top plates, four diagonal braces, and one horizontal brace. An experimental investigation was carried out to study the mechanical properties of reinforced concrete T-girder using single-point loading method under four load cases. The experimental results showed that the maximum transverse stiffness of T-girder specimens strengthened with composite trusses improved by 12.4% compared with control beams. Simultaneously, it had an excellent restraining effect on the cracks development. The maximum percentage decrease in the deflection corresponding to the maximum load when the reinforced concrete T-girder strengthened with composite trusses over the control beam of up to 39.7 was observed. In addition, the load transverse distribution coefficient was investigated according to rigid-jointed slab (girder) method. The composite trusses were chosen as intermediate diaphragm to calculate moment of inertia. The analytical model was in an accurate with the experimental result under the same loading condition. The optimize spacing of composite trusses was given from 600 mm ( L/10) to 1200 mm ( L/5), and thickness of top plate was 30 mm when the load transverse distribution coefficient was homogeneously distributed. Finally, a three-dimensional finite element model was used to evaluate the effectiveness of composite trusses.

A type of self-sensing prestressed carbon fiber–reinforced polymer reinforced concrete composite structure was proposed and studied, composed of reinforced concrete beam, prestressed carbon fiber–reinforced polymer plate, and long-gauge fiber Bragg grating sensors. The carbon fiber–reinforced polymer plate was prestressed and bonded to the bottom of the reinforced concrete beam. Two types of anchorage systems were compared and studied. The long-gauge fiber Bragg grating sensors were used as active elements for the self-sensing of mechanical responses, which were installed on the tensile rebars, carbon fiber–reinforced polymer plates, and concrete. A series of static and fatigue 4-point flexural experiments were carried out to study the bending and fatigue performances of the composite structures. After a prescribed number of fatigue loading cycles, monotonic flexural bending was performed to investigate the deterioration of properties. The results showed that the long-gauge fiber Bragg grating sensor is valid for the mechanical response sensing of the proposed structures. The compatibility of the prestressed carbon fiber–reinforced polymer plate and concrete in the pure bending zone is excellent even under fatigue loading. The load-carrying capacities were improved by more than 30% due to the application of prestressed carbon fiber–reinforced polymer plates. The stiffness was also improved remarkably and generally decreased with the accumulation of fatigue cycles linearly.

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