The behaviour of integral bridges under
vertical and horizontal earthquake ground motion

Masrilayanti

Abstract

Integral bridges are monolithic and are known to possess good earthquake resistance when
founded on a stable soil. One important consideration is the relative displacements which
can occur at the support points on structures where there is significant spacing between, i.e.
bridges. Factors such as soil, foundation types etc. can all influence the dynamic response,
and the stiffness of the bridge can influence how relative displacements affect the internal
force actions within the structure. In this study, the effect of earthquakes on integral bridges
built on several different soil types is examined, through computer simulation of an integral
abutment bridge. The study is made based on Eurocode 8 recommendations, which provides
data for different types of soil to be used for earthquake analysis. A symmetrical medium
length integral bridge obtained from an existing structure is used for the analysis. Artificial
EC8 spectrum compatible time histories (with a 0.35 g peak ground acceleration) are applied
to the structure for a range of soil stiffnesses. In conjunction with this, both static and
dynamic relative displacement studies are carried out to develop insight as to the significance
or dominance of either dynamic or relative displacement effects.

The final aim of this study is to propose a simplified approach for design/appraisal which can
allow predictions of dynamic response based on the results of static relative displacement
studies coupled with simple computer models, without having to resort to full nonlinear
integration time-history analysis. Synthetic time histories for 5 different types of soil were
created using Mathcad. The synthetic acceleration time history was validated using
Seismospect (by Seismosoft). The time histories were then used to carry our full integration
time history analyses in ANSYS (engineering simulation software) to simulate the dynamic
response of the bridge.

The results show that relative displacements play an important role in overall structural
response of the integral bridge, compared to the pure dynamic response. The results also
confirm that lower stiffness soils suffer a more detrimental effect of the earthquake compared
to a soil of higher stiffness.

Citation

vertical and horizontal earthquake ground motion. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Mar 7, 2014
• Publicly Available Date: Mar 7, 2014