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Buffeting response of a suspension bridge - a frequency domain approach

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The dynamic response of a suspension bridge to wind turbulence is computed in the frequency domain



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The estimation of the displacement response of a large civil engineering structure to wind turbulence is based on the buffeting theory [1, 2, 5]. Ref. [5] contains the theoretical background I have used for the function dynaRespFD3. In the present script, the structure in question is a suspension bridge modelled using the theory of continuous beams [3]. The buffeting response is computed in the frequency domain using the quasi-steady theory. Modal coupling was assumed negligible, which is general well verified for most of the wind velocities recorded in full scale [4]. The present script is a simplified version of the one used in [6].

The present script computes the lateral, vertical and torsional displacement response. A multi-modes approach is used. Some knowledge in the field of random vibration analysis and wind loading on structures are advised for a proper use of this script.

The present submission contains
• dynaRespFD3.m : Function that calculates the displacement response spectrum of the bridge
• 2 example files Example_1.m and Example_2.m
• 2 .mat files bridgeModalProperties.mat and DynamicDispl.mat that are used in the 2 examples.

Any question, comment or suggestion to improve the submission is welcomed.


[1] Davenport, A.G., The response of slender line – like structures to a gusty wind, Proceedings of the Institution of Civil Engineers, Vol. 23, 1962, pp. 389 – 408.
[2] Scanlan, R. H. (1978). The action of flexible bridges under wind, II: Buffeting theory. Journal of Sound and vibration, 60(2), 201-211.
[4] Thorbek, L. T., & Hansen, S. O. (1998). Coupled buffeting response of suspension bridges. Journal of Wind Engineering and Industrial Aerodynamics, 74, 839-847.
[5] Hjorth-Hansen, E. (1993). Fluctuating drag, lift and overturning moment for a line-like structure predicted (primarily) from static, mean loads. Wind Engineering, Lecture note no, 2.
[6] Cheynet, E., Jakobsen, J. B., & Snæbjörnsson, J. (2016). Buffeting response of a suspension bridge in complex terrain. Engineering Structures, 128, 474-487.

Comments and Ratings (2)

E. Cheynet

E. Cheynet (view profile)

To include modal coupling, you would need to significantly modify the function dynaRespFD3. In the present case, the lateral, vertical and torsional displacement responses of the bridge girder are computed separately. To consider modal coupling, you need (1) to compute the displacement response in a single matrix, which includes, for example, the vertical and torsional motion (2) to consider off-diagonal terms that come from the aerodynamic added mass and damping. If the modal coupling is accounted for, the computation time is increased. Note that for a single-span suspension bridge and the wind conditions usually recorded (mean wind velocity lower than 25-30 m/s), the modal coupling is generally negligible.


broad (view profile)

Really nice code. Only one question:Based on your program, how can i consider Modal coupling . thinks!



Description updated


-File uploaded properly


-Description updated


Largest update since the first submission of this script. The function dynaResp is renamed dynaResp3 and is considerably simplified (see Example 1)


Description updated and simplified code


Correction of a bug in the torsional response


- summary updated


Description, new examples




- typo




- IMPORTANT update: computing error have been corrected
- Reduction of the number of files recorded to carry out the simulation (nested functions are used instead)
- 2 examples files are included


- description


- typo

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