Report No.: CCEER-87-2

Title: Lateral and Rotational Stiffness of Pile Groups for Seismic Analysis of Highway Bridges

Authors: G. Norris and R. Sack

Date: June 1987

Sponsoring Agency: National Science Foundation

Performing Organization:
Department of Civil Engineering/258
University of Nevada, Reno
Reno, NV 89557


Methods for the assessment of the lateral and rotational stiffnesses of pile groups as needed for the seismic analysis of pile founded highway bridges are presented. Such methods take into account the nonlinear (i.e. amplitude dependent) variations in uncoupled lateral and rotational stiffnesses, each as a function of soil layering, embedment (including the lateral resistance provided by the pile cap), and pile group and cyclic load effects. Such methods are demonstrated relative to the back calculated response of the pile foundations of the Rose Creek Bridge during high amplitude full-scale push-back quick-release tests.

In addition, a method for assessing the unstable rotational response of a pile group under developing liquefaction conditions is presented. The method is demonstrated relative to the response of the central pier pile foundation of the Meloland Overcrossing during the 1979 Imperial Valley earthquake. This method includes an evaluation of the time rate of development of liquefaction and the ensuing rotationally induced settlement.

The aforementioned materials are presented herein as a collection of papers that have been (or will soon be) published. For completeness, a paper supported in part under subcontract from the Earth Technology Corporation (FHWA under project number DTFH 61-83-C-00138) has also been included (Abstract by authors).