Feng Zhang

To address the technical challenges associated with complex connection configurations and excessively long lap zones in the industrialized and prefabricated construction of reinforcements, this study proposes a novel parallel-lap splice that incorporates a third overlapping reinforcement. This innovative design offers several advantages, including neat ends, ease of construction, and enhanced economic efficiency. An experimental investigation was conducted to evaluate the effects of this new splice on the flexural behavior of reinforced concrete (RC) beams, with lap length (l_l) as the key variable (l_l = 64d, 40d, and 25d). A total of nine simply supported RC beams (three groups of three specimens each), all incorporating parallel-lap splices, were tested under four-point bending. The key mechanical properties were analyzed, including the mechanical characteristics, failure modes, flexural capacity, bending stiffness, and maximum flexural crack width. The experimental and analytical results reveal that RC beams with the new parallel-lap splice exhibit a distinctive “one primary + two secondary” crack pattern, characterized by a dominant flexural crack at midspan and secondary cracks at the ends of the lap zone. At the ultimate limit state, specimens with l_l = 64d experienced concrete crushing at the top surface of the midspan while those with l_l = 40d and l_l = 25d did not. Additionally, the l_l = 64d and l_l = 40d beams showed slight strength hardening, whereas the l_l = 25d beams exhibited rapid strength degradation. In terms of load-bearing capacity, both the l_l = 64d and l_l = 40d beams met the requirements specified in current design codes, while the l_l = 25d specimens showed a reduction in capacity exceeding 20%. Under serviceability limit states, midspan deflections and maximum crack widths for the l_l = 64d, l_l = 40d, and l_l = 25d specimens were found to fully comply with, marginally satisfy, and fail to meet the requirements of the design code, respectively. Based on these findings, as well as regression analysis of the relationship between peak load and lap length, it is recommended that a reasonable lap length for the proposed parallel-lap splice be taken as 60d, with a lap length correction factor of 1.5.

With the continuous advancement in the construction of long-span bridges in China, the application of mass concrete bearing platforms has significantly increased, rendering temperature control a critical technical challenge. The Shiziyang Bridge project features a double-deck steel truss suspension bridge with a main span of 2 180 m. Its main pier employs separated bearing platforms, each circular in plan with a diameter of 40 m and height of 9.0 m. Constructed using C45 concrete, each platform contains over 10,000 m³ of concrete. To mitigate thermal cracking risks and enhance crack resistance, this study implemented comprehensive temperature control strategies through Midas FEA finite element analysis and intelligent field temperature monitoring systems. Key findings revealed that both numerical simulations and field measurements demonstrated the effectiveness of cooling pipe arrangements with horizontal spacing of 100 cm and vertical spacing of 80 cm in reducing thermal gradients. The minimum crack resistance safety factor calculated through finite element methods reached 1.47, exceeding the specified limit of 1.4 and satisfying stress control criteria. Field monitoring recorded a maximum internal temperature peak of 64 ℃, with maximum internal-surface and surface-ambient differentials of 23.4 ℃ and 19.8 ℃ respectively, all complying with design specifications. The intelligent temperature control system successfully achieved precise regulation through automated cooling water flow adjustment, temperature monitoring, and directional water flow reversal, thereby ensuring the realization of seamless bearing platforms for the western pylon of Shiziyang Bridge. This technical approach provides valuable references for thermal management in mega-scale concrete structures, demonstrating that integrated numerical simulation and intelligent monitoring can effectively control hydration heat effects while maintaining structural integrity.

To meet the demands for efficient and high-precision assembly construction of steel reinforcement components in concrete structures, and to address the limitations of steel reinforcement binding methods for concrete box girder structures, two innovative types of steel reinforcement components, namely end-anchored and anchor plate types, were proposed. Their stress reliability was validated through mechanical performance tests. The results indicate that when compared to traditional tooth blocks, the newly proposed end-anchored and anchor plate tooth blocks exhibit minimal differences in their final form at the prestressed design load. Furthermore, they provide safe and reliable bearing capacity, meeting the specified requirements. The load-strain curve for traditional and anchor plate toothed blocks exhibits notable slope changes, whereas the strain in end-anchored toothed blocks consistently rises with increasing load, with their bearing capacity not yet reaching its limit. The anchor plate-type tooth block can enhance its stress-bearing capacity by strengthening the transverse load-bearing steel bar structure. The assembly speed of end-anchored type gear block and anchor plate-type gear block steel parts is fast. The installation time of end-anchored type gear block is 1/4 of that of traditional gear block, and the installation time of anchor plate-type gear block is only 1/12 of that of traditional gear block. Moreover, the bearing capacity is safe and reliable, and it can be promoted and applied in highway bridge engineering.