explores ways to speed up bridge construction
bridge construction projects may be in store for California
through the efforts of a Sacramento State civil engineering
professor. Eric Matsumoto, in conjunction with researchers
from UC San Diego and state departments of transportation
including CalTrans, is exploring the feasibility of constructing
bridges in the seismic regions using precast concrete. The
research focuses on a precast bridge element call the bent
cap which connects the bridge girders to columns.
an approach to rapid bridge construction already used in some
parts of the country but which especially challenges earthquake-prone
areas like California.
is being funded by a $550,000 contract from the National Cooperative
Highway research program, which develops practical solutions
to problems facing transportation agencies.
precast concrete eliminates much of the bulky falsework and
wood forms that currently are used in California bridge construction.
Precasting is less labor-intensive at the construction site,
Matsumoto says, because it removes the concrete forming, pouring
and curing from the work zone, increasing safety for both
construction crews and motorists, and decreasing traffic tie-ups
and traffic control. “Essentially what it does is speed
up construction so there is a reduced impact on the traveling
public,” Matsumoto says.
also improves quality and durability, he says, because the
work is performed in a controlled environment. “Precast
concrete is typically more durable than cast-in-place concrete.
It’s built under controlled plant conditions so higher
quality materials, construction techniques and inspections
can be employed and there is less impact due to adverse weather
conditions,” Matsumoto says.
the most appealing features of precast is speed of construction.
It allows crews to get in, get out and stay out, making it
safer for workers and the traveling public. On the Lake Ray
Hubbard Bridge in Texas, for example, the use of precast bent
caps reduced construction time by one week per bent cap on
a 43-span structure, shortening the total construction time
by 43 weeks.
California research is an extension of Matsumoto’s doctoral
work at the University of Texas at Austin which has been implemented
in several bridges including the Lake Belton Bridge. That
bridge recently won national recognition for its innovative
use of precast concrete.
concern over using pre-cast concrete in California stems from
the state’s high level of seismic activity. California
is the one of the few states that still relies primarily on
site-cast concrete for the entire bridge including the bent
cap. Although this approach ensures the bridge is well connected,
Caltrans and other states are beginning to consider alternative
construction approaches such as bent caps because of the need
to accelerate bridge construction.
goal is to develop new design and construction guidelines
for precast bent cap systems that provide cost-effective seismic
resistance while accelerating construction. “What we
don’t know is how bridge systems using precast bent
caps will behave in a major seismic event,” he says.
I think the research will successfully develop new systems
that will work,” Matsumoto says. And if it does, he
adds, it will affect the way business is done today because
California and other states need to replace bridges in congested
urban environments by the thousands.
and his students previously conducted preliminary on-campus
tests for one type of bent cap connection. The new research
at Sacramento State will involve more complex beam-column
connection tests based on developments of the research team
and information obtained from a nationwide survey currently
under way. Matsumoto’s crew will conduct four of the
six beam-column tests. The other tests will take place at
UC San Diego, where a large-scale bridge system test will
also be performed.