Flutter And Buffeting Analysis Of Long Span Bridges

Flutter and buffeting analysis of long-span bridges is the major basis for the design of wind resistance. Simulation of wind field and identification of flutter derivatives are the two essential prerequisites to carry out flutter and buffeting analysis. Based on summarizing the relevant situation of flutter and buffeting analysis, identification of flutter derivatives and wind field simulation at home and abroad, this dissertation has done the works about the three mentioned before, which including:1. According to three different coherence functions, the variation of the statistical characteristics of the simulated wind has been researched. Contrastive analysis of computational efficiency has also been made among the wind field simulation methods about prototype spectral representation, Proper Orthogonal Decomposition (POD) and linear filtering method (AR). The results have showed that the turbulent wind simulated with coherence function of the modified exponential expression for has a negative correlation. By using the modified exponential expression, problem of non-positive definite of spectral density matrix can be better solved. The prototype spectral representation method is the better one in simulating the wind field of bridges.2. The wavelet method of identifying flutter derivatives, were proposed, has broader applicability and simple thought. The method of identification of flutter derivatives based on data-driven Stochastic Subspace has also been improved. Their procedures are programmed, and the validity of which are verified by numerical examples.3. The bi-modal and multi-modal couple flutter analysis of long-span bridges has been developed. By using which coupled flutter analysis of several typical bridge structures have been done. Their effectiveness was verified by comparison between the results by different methods and exact solutions or test results.4. Based on intrinsic mode coordinates of structure, the finite element procedure of CQC(Complete Quadratic Combination) for calculating coupled buffeting response of long-span bridges has been programmed according to Scanlan’s multimode coupled buffeting theory. Meanwhile three dimensional buffeting analysis software of bridge structures in time domain has been programmed based on ANSYS finite element software, by using which the reliability of the program CQC for multi-mode coupled buffeting analysis were proven. The results of buffeting response analysis of the Dalian bay Bridge at construction state have pointed out that the result obtained by the approximation method of traditional first-order fundamental frequency for estimation of buffeting response may be too large.5. A new alternative revised step-by-step analysis method has been proposed, compared with Matsumoto’s revised step-by-step analysis method, its physical meaning is clearer. An intensive study about the flutter mechanism of several typical bridge decks was done by this method. Meanwhile it is the first time to explain why the flutter branch switches after the critical flutter velocity.6. Considering cable vibration and additional attack angle, the results of the static wind response analysis of Jinzhou Bay Bridge showed that additional angle of attack has no influence on the result and Lateral wind load on cable system is about 20 percent of the total wind load. The results of aerostatic analysis of Dalian strait Bridge show that self-anchored cable-suspension bridge exhibits different instability forms in different locations with different initial angle of attack.