The document discusses a new composite beam technology that could reduce costs and speed up bridge replacement projects for railroads. The Hillman Composite Beam combines steel bars, a concrete arch, and a fiber-reinforced plastic shell. It has been tested on a 30-foot span by the Transportation Technology Center, undergoing forces equivalent to over 70 million tons of traffic. Initial testing found no signs of degradation, and the beam withstood stresses well over code requirements in other tests. The new beam technology holds potential to replace aging bridges more affordably and quickly compared to traditional materials.

1. TECHNOLOGY By OttO M. VOndrak
>> TECHNOLOGY BRIEFS
Crossrail project
sparks fire safety
Beam of hope for bridge updates Engineers on London’s new Crossrail
tunnel project are taking advantage of
The Hillman Composite Beam shows potential to reduce costs, speed schedules the opportunity to integrate fire safety
innovations from the start. Fire-resis-
The problem is universal. Railroads tant materials can be introduced at
need to replace aging bridges, either to han- any stage, but fail to address the larg-
dle heavier railcars or because the bridges er threats of panic and train immobili-
themselves have failed or deteriorated to the Steel shear connectors ty. Project managers are considering
point of needing significant repair [see how the heating, ventilation, and air
“Bridging the Gap,” Trains, December 2007]. conditioning systems handle smoke,
But bridges are among the most expensive as well as how they might redesign
infrastructure components to replace. At the train and building interiors.
same time, capital budgets have decreased,
along with the number of domestic structural
steel suppliers, forcing supply costs skyward. Castle, Del. As he watched crews inject
A possible solution lies in a blending of resin into a mold, he considered combining
technologies. The Hillman Composite Beam steel and concrete within a composite shell.
combines less-expensive and more-readily After that, he designed the specific logis-
available steel bars (instead of steel plates) tics, validated its structural integrity, and
with the time-tested strength of an arch, and developed a process to manufacture it con-
encases it all in a lighter-than-concrete and sistently and cost-effectively. “So far, we’ve
weather-resistant plastic composite shell. Concrete arch been able to do both,” Hillman says.
(compression
While it looks like any other concrete reinforcement) Engineers at the Transportation Technol-
beam from the outside, inside it’s a revolu- ogy Center Inc. in September 2008 installed
Steel bar
tionary mix of materials and design (see (tension a 30-foot-long, 17-foot-wide test span com-
drawing at right). Bridges must overcome reinforced) prising eight composite beams on the cen-
two major forces: tension and compression. ter’s Facility for Accelerated Service Testing
Imagine a cardboard box with the flaps Low-density test loop in Pueblo, Colo.
foam core
open placed on the floor on its side. Then “We’ve run over 70 million gross tons
imagine putting something heavy on top of over the composite span, equal to a year’s
it. Obviously, the box would collapse to one worth of traffic on a busy main line,” says
side or the other. The corners of the box far- Duane Otter, a 20-year veteran bridge engi-
thest from one another succumbed to ten- neer at TTC. After 20 million gross tons, en-
sion (or stretching); the corners of the two gineers excavated down to the bridge deck
sides that are now lying on top of one an- and took measurements, looking for signs of
other succumbed to compression (flatten- Fiber-reinforced
deflection or degradation. Finding none,
ing). In bridge engineering, those compet- plastic shell they replaced the ballast, and continued test-
ing forces create shears, or cracks, in the ing. The test train runs with 80 loaded cars,
bridge material angling upward and toward each weighing 315,000 pounds, which is a 10
the middle of the beam’s length. beam, increasing shear strength. The con- resin around low-density foam, filling ev- percent greater load than the current typical
In the composite beam, steel bars laid nectors also ensure that when the beams ery crevice. Because the entire structure is weight limit. One night’s operation is equal
across the interior bottom and sides hold are in place (on the underside of the bridge encased in a composite shell of fiber-rein- to running 130 trains over the span, and this
tension in check. The concrete arch coun- and running perpendicular to it), and the forced plastic, the beam resists weathering, is done four nights a week. Testing will con-
ters compression naturally by design, and concrete deck is poured, the beams and corrosion, and moderate impact. The re- tinue throughout 2009.
shear connectors (steel rebar embedded in deck become an inseparable structure. sulting structure is strong, flexible, and Meanwhile, engineers at the University of
the arch) extend up through the top of the Composite beam builders inject plastic one-third the weight of a common-use pre- Maine’s Advanced Structures and Compos-
stressed concrete beam. Of the myriad ad- ites Center are using hydraulic cylinders to
vantages this beam presents, the availability load and unload a 70-foot beam to simulate
and affordability of the steel bar are major 2 million crossings of typical highway traf-
factors that will help keep projects on fic. In that test, the beam withstood shear
schedule and within budget. capacity in excess of 230 percent of the engi-
John Hillman, the beam’s creator and se- neering code requirements, and bending
nior engineer at Teng & Associates in Chi- capacity of 170 percent of code.
cago, estimates the average composite beam Although testing at TTC is confined
lifespan to be 80 to 100 years. This number to the current 30-foot span, Hillman pre-
is double that of traditional concrete beams, dicts railroad structures of 50- to 60-foot
and triple that of timbers. Also, one Hillman spans are feasible using the Hillman
beam span can replace up to three typical Composite Beam. That could be good
timber spans at a fraction of the cost. news for cost-conscious railroads.
Hillman first considered this merger of
concrete and steel in 1997 during construc- OttO VOndrak is a graphic designer,
BNSF GP39M 2801 leads the way over the first railroad bridge constructed using the Hill- tion of the Magazine Ditch Bridge in New writer, and photographer living in new York
man Composite Beam, shown on the right with the arch painted on the side. t tCI: Brian doe state. This is his first trains byline.
>> Former NASA illustrator Les Bossinas
hand-rendered the drawing featured above.
16 Trains JULY 2009 Read the whole story at www.TrainsMag.com
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