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A Model for the Rigid Body Motions of Skew Bridges


Maragakis, Emmanuel (1985) A Model for the Rigid Body Motions of Skew Bridges. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/YWES-NJ36.


This thesis investigates the rigid body motions of skew bridges, concentrating on the in-plane translational and rotational displacements of the bridge deck induced by impact between the deck and the abutments. Experience in the San Fernando Earthquake of February 9, 1971 demonstrates that this feature is particularly important for skew bridges.

A simple model, in which the bridge deck is represented by a rigid rod restricted by column and abutment springs is examined first. This model illustrates the mechanism by which in-plane rotational vibrations is triggered after the closure of the gap between the bridge deck and the abutment. It also shows that the force-deflection relations of the columns and the abutments are particularly important features for the response of the bridge. Methods for the exact and approximate estimation of the elastic stiffness of elastically founded, tapered bridge columns with octagonal cross section are presented next. The methods are applied to a bridge used later as an example. In addition, the yielding of the columns is examined and the force-deflection relations for bending about two orthogonal axes are estimated.

The abutments are treated as rigid bodies and the soil embankments as Winkler Foundations with elastic spring constants increasing with depth. For the examination of the yielding of soil the Rankine theory is used. Based on these assumptions an approximate force deflection relation for the abutments is constructed.

The response of a more complicated bridge model applied to a bridge near Riverside, California is examined at the end of the thesis and examples of the results are given. This model, in which the bridge deck is still represented as a rigid rod, has three in-plane degrees of freedom: two orthogonal displacements and a rotation, and is capable of capturing many of the more important features of the nonlinear, yielding response of skew bridges during strong earthquake shaking.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Civil Engineering
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Civil Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Jennings, Paul C.
Group:Earthquake Engineering Research Laboratory
Thesis Committee:
  • Jennings, Paul C. (chair)
  • Beck, James L.
  • Hall, John F.
  • Knowles, James K.
  • Wu, Theodore Yao-tsu
Defense Date:21 December 1984
Other Numbering System:
Other Numbering System NameOther Numbering System ID
EERL Report85-02
Funding AgencyGrant Number
Record Number:CaltechTHESIS:02132019-102055741
Persistent URL:
Related URLs:
URLURL TypeDescription ItemTechnical Report EERL 85-02 in CaltechAUTHORS
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11391
Deposited On:13 Feb 2019 22:06
Last Modified:21 Aug 2021 00:12

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