Abstract:The finite element method and smoothed particle hydrodynamics (SPH) method are used to simulate the high-speed impact of a single raindrop on a prestressed wind turbine blade, and the factors affecting impact pressure and stress in a single raindrop impact, such as impact speed and raindrop diameter, are analyzed. In addition, the coupling generated by the simultaneous high-speed impact of dual raindrops is analyzed, and the effect of the distance between raindrop centers is analyzed. To address the difficulty in calculation due to the large number of impacting raindrops during the rainfall process, based on the calculation results of single raindrop impacts, the method of applying equivalent loads of raindrop impacts is proposed and validated by the stress distribution and the stress at each time point, thus ensuring the simulation accuracy of using the equivalent load of raindrop impact for the actual raindrop impact.

Abstract:Shield tunnel segments are prone to damage in practical use and require reinforcement. In order to test the reinforcement effect of internal adhesive steel plates on the segments, bending static tests were conducted on the standard block segments of shield tunnels. The effects of different burial depths (divided into mid buried segments and ultradeep buried segments) and different initial damage levels (initial loading values of 78% of the failure load of mid buried segments and 90% of the failure load of ultradeep buried segments) on reinforced shield tunnel segments strengthened by steel plates were studied. The changes in the main strain and displacement field of the reinforced shield tunnel standard block segments were measured using the digital image correlation (DIC) method, and the failure characteristics (including strain and crack development laws) of the reinforced shield tunnel were studied. The test results show that there is no significant change in the principal strain of the mid buried pipe segment in the early and middle stages of the bending static test after using internal adhesive steel plates for reinforcement. However, after using steel plates of the same size for reinforcement of the ultradeep buried pipe segment, many cracks and stress increases are evident in the early and middle stages of loading. In the later stage of loading, the strain of both types of reinforced segments at the end of the steel plate will suddenly increase, and the cracks will extend diagonally toward the midspan direction. When the final damage occurs, the steel plate falls off, and the end of the steel plate used to reinforce the pipe segment becomes a weak point. When the bending moment changes from 500 kN to final failure, the displacement field of the buried pipe segment under initial loading to 78% of the failure load changes significantly, with the maximum value being 1.4 times the change in the ultradeep buried pipe segment under initial loading to 90% of the failure load. An internal adhesive steel plate can effectively improve the stiffness of the pipe segment and significantly reduce the displacement in both the X and Y directions of the pipe segment.

Abstract:The comfort of maglev trains is related to the vibration in the passenger area of the vehicle and is determined by the acceleration and impact in three directions as the train passes over the track. The comfort of the maglev track is achieved by limiting the maximum acceleration and impact to not exceed specified limits. Unlike small-span maglev bridges, long-span bridges experience changes in deck alignment under the effects of temperature, wind load, and train load, which directly affect the vertical curve alignment of the bridge track. Based on the existing technical standards and related calculation principles and methods for vertical and horizontal curve minimum radii in current maglev track design, the relationships among the vertical acceleration, impact, and alignment and bending angles of the bridge track at the train operating velocity are determined. By verifying the instantaneous deformation curves of the bridge deck using the representative positions of the train's head, middle (center of the car length), and tail during travel, the technical index for the comfort of the bridge track during instantaneous bridge deformation are established. This paper provides the calculation loading method and results for the comfort of long-span bridges using a specific long-span maglev bridge as an example.

Abstract:Intelligent bridge assembly is currently one of the key directions for bridge development in China. Dif-ferent structures and schemes are suitable for urban and mountainous construction requirements. Taking the Tongzi to Xinpu Expressway as the background engineering, this paper systematically organizes the prefabricated construction-related processes and comprehensively introduces of intelligent prefabrication process of prestressed T-beams.

Abstract:High-pier large-span continuous rigid frame bridges in mountainous areas with high-intensity earth-quakes are characterized by large variations in pier height, heavy weight of the upper structure, and large seismic forces. Therefore, seismic performance is a key design consideration for these bridges. To improve the seismic performance of large-span continuous rigid frame bridges, this paper studies seismic reduction techniques from the aspects of pier type optimization and pier stiffness matching. The results show that (1) the robust framed reinforced concrete pier structure adopted for the main pier can reduce the weight of the lower structure, reduce the stiffness of the pier, and reduce the seismic force on the pier and (2) optimizing the section sizes of the high and low piers and adjusting the pier stiffness can match the bearing capacity of each pier with the seismic force it receives.

Abstract:The post-tensioned bonded prestressing technology has been widely applied in wind power support structures due to its safety, reliability, economic efficiency, and durability. This paper provides a comprehensive introduction and explanation of the construction technology of post-tensioned bonded prestressed tendons based on an actual engineering case. Starting from key procedures such as construction preparation, tendon cutting and fabrication, placement of duct, tendon threading, tensioning and anchoring, and grouting and sealing, this paper details the critical points and precautions based on practical engineering experience. This work can serve as a reference for similar projects, aiming to promote the application and adoption of post-tensioned bonded prestressing technology in the wind power industry.

Abstract:Large-scale wind turbines are one of the development trends of the wind power industry. This article provides an engineering overview and highlights the innovation of the world's first 180 m ultrahigh mixed tower commercial application project and explains the technical advantages of the wind power mixed tower.