By Jessica Bies
Although GRS bridge technology is not suitable for every bridge building scenario, it can be a great option for replacing simple overpasses where severe flooding that could weaken a GRS structure is unlikely to occur. Here are some of the benefits of using GRS technology in appropriate settings.
- Bridges constructed with GRS can cost between 25-60% less than bridges constructed using traditional technology.
- Construction times are drastically reduced and some GRS bridges can be built in as few as 2-3 weeks.
- GRS bridges are designed to avoid the “bump at the end of the bridge” problem that occurs due to differential settling.
- GRS bridges are ductile, flexible, and capable of performing well in earthquakes.
- Because they require fewer parts, GRS bridges
are easy to maintain.
- Environmental permitting can be avoided in many instances by constructing the GRS abutments behind existing scour structures.
- GRS bridges can be built in almost any weather condition and can be adapted to suit unique site conditions.
What you will need
One of the biggest benefits of a GRS integrated bridge system is that it utilizes readily available and relatively low-cost materials. Thanks to numerous case histories and field experiments, the FHWA is capable of making materials recommendations that will optimize this specific design.
Even though the facing blocks are not a structural element of the GRS abutment, they serve an important purpose. Besides providing a form for compaction, they protect the backfill from weathering. The most common facing element used is the split-face concrete masonry unit (CMU). Not only are they lightweight and easy to place, but they provide a more aesthetic look.
Backfill is the major structural component of a GRS abutment and must be compacted to a minimum of 95% of maxim dry density. The backfill will support most of the final load and should be easy to spread, level, and compact.
Almost all GRS bridges in service today were constructed using biaxial woven polypropylene geotextiles. In addition to these three main materials, concrete block wall fill, rebar, flashing, foam board, and bitumen coating are also required.