美国作业代写：Anti-wind design of modern bridge

下面为大家整理一篇优秀的assignment代写范文- Anti-wind design of modern bridge，供大家参考学习，这篇论文讨论了现代桥梁的抗风设计。在桥梁的建设过程中，除了要确保它的质量之外，桥梁的抗风设计也是必不可少。而桥梁的抗风设计必须要考虑近地层强风的作用。在设计过程中，应对桥梁施工地点实际情况与施工高度的强风进行跟踪测量，以此做出相对应的设计，从而增强桥梁的抗风性能。

With the development and progress of China's basic construction, bridge construction, as one of the important components, plays an irreplaceable role. With the increasing proportion of modern long-span bridges, wind load has become an important factor in bridge design. To ensure the quality of bridge construction requirements, the design of wind-resistant bridges is essential. Therefore, it is very useful and necessary to study the wind-resistant theory of modern bridges and its application.

Bridges should be able to ensure the smooth flow of traffic under the action of various natural disasters. With the development of modern bridges, wind as a natural disaster with high frequency has a serious threat to the bridge. In this case, to ensure the quality and safety of the bridge must improve the modern bridge wind resistance theory and application.

The wind-resistant design of the bridge must consider the effect of the near-formation gale. In the design process, we should follow the actual situation of the bridge and the strong wind in the construction height, and the measuring tools include air wind Profiler and ultrasonic anemometer. Through the corresponding measurements to draw the wind mean wind profile sketch map, and then in the bridge construction process more reasonable work, so as to enhance the wind resistance of the bridge.

The statistic analysis of the extreme wind velocity in bridge construction plays an important role in the construction of the bridge. In our country, we usually use three kinds of extremum distribution probability model to analyze. At different locations, the distribution of extreme wind speeds varies in any direction. Most of the bridge engineering structures, especially the modern large-span bridge structure, are more obvious in different spatial orientations.

Wind tunnel simulation of the atmospheric boundary layer near ground wind is an indispensable step in the design of the bridge, and the wind tunnel simulation can be divided into two types, active simulation and passive simulation, in which the passive simulation is mainly controlled by the turbulent boundary layer. The active simulation mainly refers to the controllable motion mechanism. Through the implementation of the above two simulation methods, we can better the rational design of the bridge wind resistance.

Wind tunnel experiment research is not only an important content of aerodynamic effect research, but also a most important means. After the wind-blown accident at Tacoma Narrows Bridge, the engineers began to realize that the wind was not just static, it opened the curtain of the theory of the vibration and aeroelastic of Long-span bridges. The progress of science and technology has produced a variety of wind tunnel experimental methods, mainly full bridge aeroelastic model, tensile elastic model, segmental rigid model. In all types of wind tunnel experiments, the full bridge aerodynamic elasticity is the first model used in the study of wind-resistant bridges in China.

For the numerical wind tunnel identification of the aerodynamic parameters of the two-dimensional bridge section, the method of numerical simulation is widely used at present. There is a complex turbulence in the vicinity of the bridge section, and the turbulent motion is a stochastic process, which presents a great challenge to the numerical simulation. The test methods used in China at present include direct numerical simulation, large eddy simulation and Reynolds time simulation. Tongji University has independently developed FEM―FLUID and rvm―fluid simulation software, and later introduced the fluent commercial software, as the above two software supplements and verification.

According to the different modes of wind-induced vibration, the theory of wind-induced vibration of bridges is divided into chatter theory, chattering theory, relaxation theory and Vortex vibration theory. Because of the small probability of relaxation and vortex, flutter and buffeting are the key points of modern bridge analysis. For the flutter theory, with the advance of time and the development of science and technology, it has undergone the development process from simple to complex, from theory to practice, from approximate to precise. The two-dimensional Flutter theory analysis method is widely used in bridge engineering. However, with the increase of bridge span, the lateral stiffness of the bridge structure decreases sharply, which results in the coupling of the lateral bending and torsional mode. In addition, it is necessary to develop a high precision three-dimensional bridge flutter analysis method for accurate analysis of bridge flutter due to the higher degree of self vibration frequency compliance.

Buffeting is the formation of turbulent structure in a blunt body, and it is a kind of forced vibration without divergence. At present, the general chattering theory includes Davenport buffeting analysis theory, Scanlan shaking vibration analysis theory and Lin's time-domain buffeting analysis theory. By comparing the theoretical calculation with the measured results in the field, it is found that there is a large deflection angle between the strong wind and the bridge span, and the analysis of the buffeting response will result in greater error. Therefore, it is necessary to establish an accurate method for the analysis of buffeting response of a large span bridge under the action of oblique wind.

Since 21st century, a number of modern bridges with large span and high technical content have been built in the field of bridge. To ensure the quality of these Long-span bridge design work, it is necessary to calculate and design the dynamic stability of the bridge. Therefore, in the early stage of construction of large-span bridge, the wind-resistant theory can be used to calculate and design the bridge's resistance and construction strength according to the requirement of modern bridge stability, so as to guarantee the construction quality of the bridge.

In the process of design and application of wind resistance theory of bridges, the calculation and design of static wind equivalent load is an important part, which needs to consider the interaction between the characteristics of wind and the structural characteristics of bridge. The Davenport theory makes the calculation of wind load more accurate, and also puts forward the specific benefit coefficients of gust load coefficient and gust, so that the load of equivalent wind can be extended to a larger field through calculation model. According to the space structure of modern bridge, the static wind equivalent of bridge can be studied, and the static wind replacement scheme of long span bridge is designed according to wind speed in the same time period. After the completion of various equivalent wind calculation schemes, the static wind replacement scheme should be designed by means of linear connection, so that the static wind equivalent load method can be used correctly.

The development of bridge construction in China since the 1980s, after the 1990s of learning and improvement, to 21st century, in the first two periods of development and accumulation, and constantly independent innovation to improve the core competitiveness of bridge construction. It has made great progress in the theory and application of wind resistance of bridges, but there are still some weak links. Therefore, the study of wind-resisting theory of bridge in China should be deepened. Through the continuous improvement of theoretical methods to promote the rapid development of bridge.

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