In a chloride environment, taking reinforced concrete structures as the research object, the corrosion rate of reinforcement determines its corrosion expansion because multiple coupling parameters will affect the corrosion rate of reinforcement, which is extremely difficult to effectively predict. In this paper, 144 sets of experimental data were collected and sorted out by reading the relevant literature, and six empirical models for predicting the corrosion rate of steel bars were compared and analyzed based on these experimental data. Based on the investigations, a new empirical model is proposed for predicting the corrosion rate of reinforcement, and the relevant influencing factors are considered in the new model. By comparing the 144 sets of experimental data and 90 experimental data for this paper, the new prediction model can well predict the corrosion rate of reinforcement. Furthermore, the time variability of the new prediction model is verified. The probability distribution characteristics of seven prediction models are obtained through model error analysis, which provides a theoretical basis for the next step of concrete cover cracking and reliability analysis.

Prestressed concrete box girders are commonly employed in the development of high-speed railway bridge constructions. The prestressed strands in the girder may corrode due to long-term chloride erosion, leading to the degradation of its flexural performance. To examine the flexural performance of corrosion-affected simply supported prestressed concrete box girders, eight T-shaped mock-up beams related to the girders used in the construction of high-speed railway bridges were manufactured utilizing similarity theory. Seven of the beams underwent electrochemical accelerated corrosion, and then each beam was subjected to failure under the four-point load test method. Measurements recorded and analyzed in detail during the loading process included the following: crack propagation, crack width at various loads, crack load, ultimate load, deflection, and concrete strain of the mid-span section. The results demonstrate that a corrosion rate of just 8.31% has a considerable impact on the structural integrity of the beams, as evidenced by a pronounced reduction in flexural cracks and a tendency towards reduced reinforcement failure. Furthermore, the corrosive process has a detrimental effect on mid-span deflection, ductility, and ultimate flexural bearing capacity, which could have significant implications for bridge safety. This study provides valuable insights for the assessment of flexural performance and the development of appropriate maintenance strategies for corroded simply supported box girders in high-speed railways.

In the present study, 104 sets of flexural tests on corroded prestressed concrete (CPC) beams were gathered from different publications. A flexural strength database for CPC beams was created by incorporating standardized concrete strength and the corrosion rate of prestressed steel. This database enables the analysis of the impact of different factors on the flexural capacity, such as the beam’s width and effective depth, concrete compressive strength, shear span ratio, the prestressed steel’s corrosion level, prestressing ratio (PPR), and the effective prestress. The findings show that the flexural strength of the CPC beams is notably influenced by variations in beam width, shear span ratio, and the prestressed steel’s corrosion level and prestressing ratio compared to other parameters. Furthermore, a comparison was conducted of the Chinese code, Eurocode and ACI standard for evaluating the flexural strength of CPC beams using the established database. It shows that the three design codes overestimate the flexural strength of CPC beams, and it is unsafe to predict flexural strength using these three codes without taking into account the impact of corrosion. Finally, a practical model based on the ACI standard is suggested to provide precise and reliable predictions across a diverse set of test data.

For this study, we conducted a detailed examination and comprehensive comparative analysis of the structural responses and mechanical behavior of bolted sleeve connections in precast circular semi-continuous steel tubular concrete (PCSCFST) columns. The research involved fourteen specimens, and we considered the impacts of various parameters, including eccentricity, external steel sleeve thickness, bolt diameter, and slenderness ratio. The findings revealed that the external steel sleeve significantly enhances the protection of the connection area, enabling the bolts to effectively withstand eccentric loads. However, sleeves that are too thick may lead to premature bolt failure, reducing their ultimate load-bearing capacity. Using bolts to transfer loads to the concrete significantly strengthens the restraining effect of the steel sleeve. Nonetheless, increasing the bolt diameter beyond a certain threshold may diminish this beneficial impact, potentially leading to connection failure and a decrease in ultimate load-bearing capacity. A new ‘cooperative value q’ measures component collaboration at ultimate capacity, showing that shorter columns offer less effective coordination than longer ones. Through regression analysis, we formulated a prediction for axial ultimate bearing capacity, closely aligning with the experimental data (N_pre-a/N_u average value of 1.003, variance 0.00248). Three N–M curves, including the Eurocode 4 method, offered conservative predictions, with Eurocode 4 closely matching the experimental results. A refined prediction method following Eurocode 4 was developed, yielding an average P_pre-U/P_u value of 0.971 and a variance of 0.0107.

Concrete-filled round-ended steel tubes (CFRTs) are a unique type of composite stub columns, which have the advantage of aesthetics and a well-distributed major–minor axis. Thus, the structure has been widely employed as piers and columns in bridges. To improve the mechanical performance of CFRTs with a large length–width ratio and to enhance the restraint effect of steel tubes on concrete, this study investigates the compressive property of multi-chamber, concrete-filled, round-ended steel tubular (M-CFRT) stub columns using a combination of experimental and numerical analyses. A detailed compression test on eight specimens is conducted to examine the compressive property of M-CFRT stub columns. The study focuses on understanding the influence of some key parameters on ultimate bearing capacity, failure stage, damage modes, and ductility. Additionally, the accuracy of the finite element modeling method in simulating the ultimate bearing capacity of the structure is verified. Finally, the calculating formula for the ultimate bearing capacity of M-CFRT stub columns is proposed on the basis of the experimental and numerical findings. Results of the formula calculation are consistent with the experimental data. These research findings serve as a valuable reference for designing similar structures in engineering practice.

To study the mechanical performance of bolted connections with different structural forms of reinforced rings, based on the results of monotonic loading tests on two bolted connections between a concrete-filled steel tubular column and a steel beam with an outer reinforcing ring, this article uses ABAQUS v.2020 software to establish a three-dimensional refined finite element analysis model of such connections using appropriate constitutive models for concrete and steel. Subsequently, the effect of the dimensions of the steel beam, reinforcing ring, and cover plate on the load-bearing properties and the failure mechanism of the connections is investigated, and the numerical model is consistent with the verification test results. Then, the numerical simulations comparing bolted exterior reinforced rings under seven different construction measures (i.e., number of bolts, stiffeners) based on a conventional welded exterior reinforced rings with rigid connections (i.e., CGJ) are standardized. The research results indicate that when four rows of bolts are introduced on exterior reinforced rings, the web of steel beam is welded with stiffeners, and the top and bottom reinforced rings are also added with stiffeners; this bolted connection with an external reinforcing ring (i.e., GZ-7) can achieve the rigidity and load-bearing capacity of a fully welded external reinforcing ring rigid connection. At the same time, the reinforcing ring plate is bolted to the flange of the steel beam, and the force transmission path at the connection is changed to avoid the brittle fracture easily caused by the welded flange joints. It is also in line with the development trend of sustainable construction of “assembly” and “disassembly”.