Mode Superposition Analysis of Viscously Damped Nonlinear Structural Systems Using an Incremental Algorithm

1993 ◽  
Vol 115 (4) ◽  
pp. 397-402 ◽  
Author(s):  
Yang-Tai Lin ◽  
Te-Chang Sun
Keyword(s):  
Time Integration ◽  
Computational Cost ◽  
Computational Effort ◽  
Incremental Algorithm ◽  
Structural Systems ◽  
Superposition Method ◽  
Mode Superposition ◽  
Mode Superposition Method ◽  
Nonlinear Structural ◽  
Decomposition Procedure

A mode superposition method for approximately solving the dynamic response of viscously damped nonlinear structural systems is presented, which is characterized by high accuracy and low computational cost. The method is based on an incremental decomposition procedure to formulate the motion of the discrete system, which is established by finite element theory for spatial dependence and both geometric and material nonlinearities are considered. The accuracy and efficiency are studied through two practical problems. By comparing the results using the present method with those using the direct time integration, it is found that the error is negligible and the computational effort can be significantly reduced.

scholarly journals Modeling Traveling Waves Using Mode Superposition

2010 ◽  
Author(s):  
Vivek Jaiswal ◽  
Aditi Sheshadri ◽  
J. Kim Vandiver
Keyword(s):  
Traveling Waves ◽  
Traveling Wave ◽  
Force Model ◽  
Superposition Method ◽  
Mode Superposition ◽  
Response Characteristics ◽  
Excitation Region ◽  
Mode Superposition Method ◽  
Excitation Force ◽  
Measured Response

Analysis of the data from two Vortex-Induced Vibration (VIV) experiments conducted in the Gulf Stream on a 500-foot-long, 1.43 inches diameter, flexible, tension dominated riser model revealed that the response is predominantly characterized by the presence of traveling waves. It was also observed that the location of the VIV excitation region (power-in) affects the characteristics of the response. The conventional method of modeling the excitation force as a standing wave was found inadequate to predict the location of the peak measured response accurately, especially in the cases where the excitation region is close to a boundary (the ends of the riser model). A modified excitation force model consisting of a combination of standing and traveling wave excitation regions is demonstrated to predict the location of the peak response more accurately. This work presents the idea of modifying the VIV excitation model to include traveling wave characteristics and using mode superposition method for computing the response to this modified force. Examples of the implementation of this method are shown for the two distinct cases of the location of the power-in region — the power-in region adjacent to the boundary and the power-in region away from the boundary. Depending on the location of the power-in region, different proportions of standing and traveling wave excitations are used to yield predicted responses that match the measured response characteristics.

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