Engineers Test Quake
September 22, 2017
bridge deck swayed, cracks circled the support columns and, in 20
seconds, the earthquake ended, and the bridge settled to a stop.
Damaged, but still standing, the 100-ton, 70 foot long bridge was
sitting on three large shake tables in the University of Nevada, Reno
Earthquake Engineering Laboratory, the first large-scale bridge model to
test five principles and techniques of accelerated bridge construction
combined in one bridge model.
Engineers at the University of Nevada, Reno shook the massive model,
mimicking the large ground motions of the deadly and damaging 1994
Northridge, California earthquake but amplified to a magnitude 7.5. The
researchers are working in the lab to devise methods to construct
bridges much faster than ordinary bridges and yet make sure they are
Graduate engineering students at the University of Nevada, Reno inspect
damage to a 100-ton, 70-foot-long concrete bridge that was shaken in a
live simulation to test new materials, connections and construction
techniques with the goal of creating safer structures and quicker
rebuildiung times following earthquakes.
The experiment uses new, leading-edge engineering design that aims to
speed construction and improve earthquake resistance and resiliency.
“Specifically, the objective of the study is to design two large-scale
bridge models incorporating some of the most promising ABC connections
and components and test these under bidirectional earthquakes on massive
shake tables to assess the performance of various components and
connections and the interaction among them,” Saiid Saiidi, principal
investigator of the project, from the Department of Civil and
Environmental Engineering and the director of the Center for Advanced
Technology in Bridges and Infrastructure, said.
The study, funded by The California Department of Transportation,
investigates the seismic response of bridges that are constructed with
precast components and connections at the system level and will help
facilitate the adoption of accelerated bridge construction in the field
and the development of seismic design guidelines for ABC bridges.
The components – the bridge decks, columns and connections, were built
separately outside the lab, and then assembled like an erector set on
top of three 14 by 14 foot shake tables – hydraulically driven tables
programmed to mimic the forces of large earthquakes.
The connections incorporated in the bridge model have been individually
tested through Saiid’s previous research projects and some of the work
by others. But they have never been combined in a realistic bridge model
subjected to realistic earthquake motions.
“The good seismic performance of a component does not guarantee that the
entire bridge will resist the earthquake,” Saiidi said. “That’s why this
test was necessary.”
innovations in this bridge come from connections and an advanced
concrete material known as ultra-high performance concrete (UHPC). The
goal for using these connections and UHPC is to expedite bridge
construction substantially. The five connection types are steel pipe
pins, grouted ducts, UHPC deck joints, high-strength grout pocket
deck-girder connections, and UHPC deck cap beam connections. The
earthquake engineering specialists installed over 400 sensors:
potentiometers, transducers, strain gauges, string potentiometers and
accelerometers to record the forces of the earthquake simulated in the
“This is a big step in getting these techniques and materials adopted by
public agencies for use in the communities,” Saiid said. “The
experiment, with the largest motions at 200 percent of the design
earthquake, was a success, showing the components performed well. Of
course, we have to analyze the huge amounts of data collected through
our sensor network to quantify the results.”
The University’s Earthquake Engineering Laboratory combined with their
Large-Scale Structures Laboratory comprise the biggest, most versatile
large-scale structures, earthquake/seismic engineering facility in the
United States, according to National Institute of Standards and
Technology, and possibly the largest University-based facility of its
kind in the world.