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considered the probability of spalling, other types of damage or ductility limits could be
used to develop target displacement values. The average probability of spalling was close
to the target values for both the CIP emulation and hybrid piers. There was still
considerable scatter in the amount of damage experienced by inpidual piers because of
variation in the response of the inpidual piers to ground motions.
Both the ELFD and DDBD procedures produced acceptable designs of CIP
emulation and hybrid pier systems that were not prone to excessive damage. The DDBD procedure has the advantage that the expected amount of damage is predicted in design;
however, relationships between the response reduction factor and expected amount of
damage for a particular level of seismic risk could be developed for the ELFD procedure
to provide similar estimates.
This research suggests that the CIP emulation and hybrid piers should experience
similar amounts of damage during earthquakes. However, the models used to estimate the
seismic response of the piers and the damage models for the hybrid piers were not
calibrated with experimental results. Future calibration of the design procedures using
experimental test results is necessary to ensure that the design procedures are accurate.
Additional work is also required to expand the design procedures to consider
multiple-degree-of-freedom bridge systems and soil-structure interaction. CHAPTER 1
INTRODUCTION
Bridge construction in the Puget Sound region and other metropolitan areas can
severely exacerbate traffic congestion, resulting in costly delays to motorists and freight.
Bridge types that can be constructed and/or reconstructed rapidly are needed to reduce
these delays. The use of precast concrete components in bridges presents a potential
solution, because the components can be fabricated off-site in advance of construction,
reducing the amount of time required to complete the bridge and the number of
construction tasks that must be completed on-site.
Precast, prestressed concrete girders are currently used widely; however, the use
of precast components for other portions of a bridge has been limited. Precast
components for bridge substructures have been used mainly in non-seismic regions
because difficulties creating moment connections between precast components have
hindered their use in seismic regions.
Two precast concrete bridge pier systems developed for use in the seismically
active portion of Washington State are presented in this report. In order to use these
systems, design procedures are required to ensure that the precast pier systems will
exhibit acceptable performance in earthquakes and not experience excessive damage.
This report focuses on the development and evaluation of these design procedures.
1.1 MOTIVATION FOR RAPID CONSTRUCTION
Disruption of highway traffic flow due to bridge construction is becoming less
tolerable as the amount of congestion in metropolitan areas increases. The direct costs
(traffic control, barricades, etc.) and indirect costs (delays to motorists) from partial or
full closure of a roadway to accommodate bridge construction can be staggering. A recent
study in Houston found that the indirect costs associated with closing a highway bridge
near the city center were over $100,000 a day (Jones and Vogel 2001). Bridge designs
that can be constructed rapidly are needed to reduce these costs and better serve
motorists. Rapid construction can be considered in two contexts. Optimal rapid construction
solutions should meet both of these needs.
1. Reduced Construction Time. Rapid construction can significantly reduce the
amount of time required to construct a bridge, allowing traffic to return to its