The cable-pylon anchorage zone is a typical D-region in a cable-stayed bridge, for which there has been no uniform simplified design method until now. In this paper, based on the extensive statistics of actual projects, topology optimization techniques and principle of minimum strain energy, two precise strut-and-tie models for the cable-pylon anchorage zone are proposed, which can clearly reveal the load-transmitting mechanism of the anchorage zone. Th e explicit geometric parameters of the strut-and-tie models are derived; thus, the designers can directly use these models. A simple design procedure to deploy prestressing tendons in the anchorage zone is also introduced, whose effectiveness and convenience are demonstrated by two design examples. A new design named the “one-way prestressing tendons PC cable-pylon” is also discussed regarding its application scope.
The prefabricated cement-based partition wall has been widely used in assembled buildings because of its high manufacturing efficiency, high-quality surface, and simple and convenient construction process. In this paper, a general porous partition wall that is made from cement-based materials was proposed to meet the optimal mechanical and thermal performance during transportation, construction and its service life. The porosity of the proposed partition wall is formed by elliptic-cylinder-type cavities. The finite element method was used to investigate the mechanical and thermal behaviour, which shows that the proposed model has distinct advantages over the current partition wall that is used in the building industry. It is found that, by controlling the eccentricity of the elliptic-cylinder cavities, the proposed wall stiffness can be adjusted to respond to the imposed loads and to improve the thermal performance, which can be used for the optimum design. Finally, design guidance is provided to obtain the optimal mechanical and thermal performance. The proposed model could be used as a promising candidate for partition wall in the building industry.
Genetic evolutionary structural optimization (GESO) method is an integration of the genetic algorithm (GA) and evolutionary structural optimization (ESO). It has proven to be more powerful in searching for global optimal response and requires less computational efforts than ESO or GA. However, GESO breaks down in the Zhou-Rozvany problem. Furthermore, GESO occasionally misses the optimum layout of a structure in the evolution for its characteristic of probabilistic deletion. This paper proposes an improved strategy that has been realized by MATLAB programming. A penalty gene is introduced into the GESO strategy and the performance index (PI) is monitored during the optimization process. Once the PI is less than the preset value which means that the calculation error of some element’s sensitivity is too big or some important elements are mistakenly removed, the penalty gene becomes active to recover those elements and reduce their selection probability in the next iterations. It should be noted that this improvement strategy is different from “freezing,” and the recovered elements could still be removed, if necessary. The improved GESO performs well in the Zhou-Rozvany problem. In other numerical examples, the results indicate that the improved GESO has inherited the computational efficiency of GESO and more importantly increased the optimizing capacity and stability.
The anchorage zone of cable-stayed bridge tower is the key zone related to the safety of the bridge. Traditionally, prestress tendons are arranged in the concrete tower, in order to avoid the shortcoming of circumferential tendons, a new layout of prestress tendons named as "one-way prestress tendons" is put forward. This paper analyze the spatial stress state of this new design by the software ANSYS. Three load cases are considered: tensioning the prestress tendons only, loading the designed stay-cable force and the one stay-cable broken condition. The results show that: this new design can ensure the safety of the tower and will be reliable in practice.
The modal of a structure is the natural vibration characteristic of the structure, which is very important for damage identification of the system. To accurately measure the structural modal, it is necessary to perform clock synchronization operations on the vibration sensors at each measuring point of the structure. This paper uses an improved TSPN algorithm for clock synchronization. It is assumed that the delay of the data in the transmission process obeys normal distribution. The fitting degree of a normal distribution is tested by fitting the delay distribution curve. Then, an interval estimation method is used to estimate the delay. The synchronization of multiple sensors and onsite structural modal testing verifies the correctness of the process after synchronization. The method in this paper is suitable for MCU-based vibration sensors to perform clock synchronization for structural modal measurements.
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