Abstract:Shear failure in reinforced concrete (RC) structures, characterized by their sudden and brittle nature, often results from inadequate shear reinforcement or degradation due to aging or increased loading demands. To enhance shear capacity, various retrofitting techniques have been developed, with external prestressing bars recognized as an effective solution. These bars apply an active clamping force to improve shear resistance and delay the formation and propagation of diagonal cracks. This review presents a comprehensive analysis of experimental investigations and numerical models, such as strut-and-tie and damage-plasticity approaches, to evaluate shear strengthening with external prestressing bars. In this review, early exploratory studies, the evolution of experimental programs, and the development of analytical and finite element models for predicting the behavior of strengthened beams are examined. Particular attention is given to validating numerical models against experimental data, focusing on load-sharing mechanisms, ductility, failure modes, and serviceability. Practical design implications are evaluated, research gaps are identified, and recommendations for future studies are proposed to advance the implementation of this technique. Findings from authoritative sources are integrated to provide a definitive reference for researchers and engineers seeking sustainable and efficient shear retrofit solutions.

Abstract:This paper presents an experimental investigation into the shear capacity of prestressed concrete (PC) hollow core slabs with and without pre-existing oblique crack damage. A salvaged hollow core slab from Taihe Road Viaduct was selected for testing, with one end exhibiting in-service crack damage (T-A side) and the other end remaining intact (T-B side). Both ends were subjected to static loading to failure, and their shear performance was compared. The results indicate that the ultimate shear capacity of the damaged T-A side was approximately 16% lower than that of the undamaged T-B side. The damaged end also exhibited a lower cracking load, greater ultimate deflection, and greater torsional deformation. Both ends failed in a "bond-shear" mode, but the presence of pre-existing cracks on the T-A side exacerbated crack propagation and led to a wider main failure crack. The experimental results were used to evaluate the accuracy and applicability of several shear capacity calculation methods, including JTG 3362—2018, AASHTO LRFD Specifications 2020, ROSS, Naji, and Zhang''s models, and the Response2000 program. The comparison reveals that Zhang''s model and the ROSS model provided the most accurate predictions relative to the experimental values. The AASHTO LRFD method was found to be slightly unconservative for the damaged side (V_t/V_pre = 0.94) while providing a conservative prediction for the undamaged side. This study highlights the detrimental effects of in-service cracks and reveals limitations in some conventional codes for assessing damaged members.

Abstract:This study investigates the construction quality and potential defects of grouted sleeve connections in a prefabricated bridge pier dismantled from a project in Shanghai using section-cutting inspection. Ten samples were examined with a focus on grout compactness, reinforcement anchorage length, and centering accuracy. The results show that the grout within the sleeves was highly compact, and all mechanical performance indices satisfied the relevant specifications and design requirements, indicating overall reliable construction quality. Minor deficiencies, including slightly insufficient anchorage length and deviations in reinforcement centering, were identified but are considered to have negligible effects on load-bearing and deformation capacities on the basis of existing research. The findings suggest that the current construction process generally meets quality requirements; however, improvements in grout mix proportion, construction procedures, and the addition of external threading on the sleeve surface are recommended to enhance bonding with surrounding concrete. This work provides experimental evidence from an actual engineering case to support the safety and durability assessment of grouted sleeve–connected piers and supplements nondestructive testing by revealing internal defects that are otherwise difficult to detect.

Abstract:To evaluate the bonding behavior between ribbed steel bars and ultra-high-performance concrete (UHPC), several pull-out samples were experimentally investigated and presented. The influences of bar diameter and embedment length on the bond failure mode, ultimate bond stress, stress?slip curve and bond stress distribution were investigated. Compared with that of ordinary reinforced concrete, the ultimate bond stress between steel bars and UHPC was increased by 74% under the same conditions. In addition, the bond-slip curve showed a relatively large slope before the ultimate bond stress was reached, and at the same time, the curve showed better ductility after the ultimate bond stress was exceeded. When the sample experiences steel bar yielding or pull-out failure, the bond stress distribution curve exhibits typical multipeak features. As the bar embedment length increased, the bond stress distribution became increasingly heterogeneous, and the increase in the peak number in the bond stress distribution curve reflected this trend. Under appropriate concrete cover thickness, the critical embedment length was between 4d and 6d.

Abstract:To address two critical challenges in the numerical modeling of precast segmental structures—namely, post-tensioned prestress simulation and adhesive joint representation—this study proposes a refined finite element modeling approach. This method incorporates a nearest point matching algorithm during prestress application, resolving issues such as modeling complexity and low computational efficiency in traditional tendon–concrete node matching. For adhesive joint simulation, a cohesive contact element based on fracture mechanics is adopted, enabling the characterization of tensile-shear coupled failure under combined loading conditions. To validate the method, a precast segmental prestressed cap beam from a real-world project was analyzed under prestressing and service load scenarios. The results demonstrate that the proposed approach is efficient, rational, and practically applicable, providing reliable technical support for high-fidelity numerical simulations of prefabricated structures.

Abstract:The Jiasong Highway Bridge over the Huangpu River is located in Songjiang District, Shanghai. It is planned as a secondary highway with six lanes in both directions and non-motorized lanes on both sides. The main bridge design adopts a (130 + 336 + 130)-m self-anchored suspension bridge. In this paper, the bridge construction plan is systematically analyzed and compared with alternative designs, considering aspects such as the overall scheme, main bridge design, and main bridge construction methods. These evaluations are based on construction conditions, such as hydrology, geology, navigation, and the environment. The aim of this study is to provide a reference for the design and construction of similar bridges in the future.