A Caltech Library Service

Modal Coupling and Earthquake Response of Tall Buildings


Hoerner, John Brent (1971) Modal Coupling and Earthquake Response of Tall Buildings. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/0H45-NM32.


The major dynamic features of tall buildings are within the scope of a shear beam model. Herein the usual one-dimensional model is extended to three dimensions to include modes with translational and rotational components. The analysis is restricted to the continuous model with linear response.

A class of models for tall buildings is presented which possesses three sets of mutually orthogonal coupled modes. The amount of modal coupling is related to the eccentricities divided by the translational-torsional frequency differences. Strong modal coupling can occur if the eccentricities and frequency differences are small, as in a rectangular building with a smooth distribution of columns. A perturbation scheme is developed for buildings almost in this class. The perturbation method is applicable to buildings with nearly vertical mass and rigidity centers and with ith-modes of nearly the same shape.

Rotational components of earthquake response in buildings primarily results from modal coupling, and it is shown that modal coupling can increase response on the building's perimeter. Furthermore, rectangular buildings with modal coupling can show a beating-type frequency response, for which the more usual r.m.s. combination should be replaced by an absolute sum. These effects can significantly increase certain response parameters. The corners of a rectangular building can have a 95% increase in shear, as compared with 30% implied by a 5% eccentricity in the codes. Base shears and overturning moments can be increased by 40%.

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:
  • Unknown, Unknown
Defense Date:24 May 1971
Other Numbering System:
Other Numbering System NameOther Numbering System ID
EERL Report71-07
Record Number:CaltechThesis:10192017-153501109
Persistent URL:
Related URLs:
URLURL TypeDescription ItemTechnical Report EERL 71-07 in CaltechAUTHORS
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10533
Deposited By: Kathy Johnson
Deposited On:19 Oct 2017 22:42
Last Modified:17 Aug 2021 19:36

Thesis Files

PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page