Those who paid attention in math class early in life can have a leg up when it comes to hauling construction and demolition materials or the equipment needed to handle those materials. From calculating the weight of material or equipment to considering the geometry (camber angle) of a loaded trailer, precise calculations are essential for transport.
Safety considerations outweigh all others when it comes to ensuring loads are not too heavy or out of balance.
In addition to safety, there can be financial penalties involved when trucks deemed too heavy or otherwise out of compliance head out on public highways and roads before all necessary measures—and calculations—have been taken.
Built for the task
Among the problems that can befall contractors and their drivers when taking part in a major demolition, construction or road building project is using equipment that is too light duty for the job at hand.
Moving soil, sand or even uniform-sized gravel is commonly done with aluminum dump trailers. Those same trailers, however, may be less than ideal to handle the large chunks of concrete with rebar that are often generated at demolition sites.
The more metal in the rubble, the less likely an aluminum dump trailer is sufficient for hauling, says Greg Brown of Romulus, Michigan-based Benlee Inc. “Most demo guys use roll-off trailers and roll-off trucks, not dump trailers for demo [site] metal,” says Brown.
Cost is important also, says Brown. “Putting roll-off boxes that cost $6,000 at a site that can carry what a $50,000 [aluminum] trailer costs is a major savings for the demo guy,” he comments.
Brown says Benlee, like other companies, builds both roll-off containers and dump beds and trailers it markets as heavy duty to sell to those seeking durable equipment in either format.
Makers of hauling equipment say buyers need to shop responsibly for such heavy-duty supplies to ensure they are getting what they expect. “The definition of ‘heavy duty’ is in the eye of the beholder, as there is no industry standard for heavy-duty or extra-heavy-duty roll-off containers,” says Kirk Warren, director of product management in the steel division of Charlotte, North Carolina-based Wastequip.
Despite no industry standard definition, Warren says investing in more durable containers is important. “Roll-off containers are revenue-producing assets provided they are in the field in use, and not in your yard awaiting repairs.”
Warren says his definition of what traits can be considered heavy duty in a roll-off container include a substructure with sturdy main rails, supporting cross members and thick sheet steel on the floor. The container’s sidewalls should include stout vertical bars and a top rail for reinforcement.
In addition to shopping for sturdiness because of the type of material that will be put in the container, Warren says buyers also should consider whether materials loaded inside will be distributed evenly or in the form of a concentrated load. The latter could put stress on certain parts of the container.
Also to be considered is what types of machinery will be loading and operating near the container. Large excavators, cranes or dozers can inadvertently cause structural damage to a less sturdy container all too easily.
A sturdy container will inevitably weigh more, which requires contractors to do the calculations pertaining to container and highway hauling aspects of the job.
Calculating the mass
Contractors and hauling firms become as knowledgeable about federal, state and local highway and street weight regulations as any segment of the population in the United States. Knowing the weight of a loaded truck or towed trailer has created a demand for scales and other measuring systems that serve the construction, demolition and road building industries. (See the sidebar “Avoiding a weight problem.”)
How much material by weight is going to or from a job site also contributes to knowing how many containers or trucks will be needed on a daily basis or throughout the course of a job. That is where more math comes into play, but there are resources out there that can help contractors, according to Warren.
“There are many demolition and material density calculators available to estimators to determine the correct size containers to use,” says Warren.
He continues, “Generally, the GVWR (gross vehicle weight rating, as determined by pertinent regulations) minus the weight of equipment (chassis, hoist and container) equals the maximum payload.” To determine that payload by volume, one needs to know the material density as measured by pounds per cubic yard, he adds.
As an example, Warren says if the pertinent equipment weighs 36,000 pounds and a 66,000 pound GSVR limit is in effect, then 30,000 pounds of material can be loaded.
In this example, if crushed concrete has a material density of 2,025 pounds per cubic yard, then 15 cubic yards is the approximate volume limit per loaded truck.
Concludes Warren, “So, for crushed concrete, the recommended container size would be a 20-cubic yard container filled only to 75 percent full.” In this example and others like it, he says, “Purchasing and placing the appropriate roll-off containers based on application yields the best return on investment.”
While hauling materials requires one set of formulas, the challenge of bringing off-road equipment to and from a job site introduces another set of considerations, according to a maker of specialized trailers.
A question of balance
Rensselaer, Indiana-based Talbert Manufacturing makes what it calls heavy-haul and specialized trailers most commonly used to transport equipment and components for the commercial, industrial, military and government sectors.
Troy Geisler, the company’s vice president of sales and marketing, says in these applications, “load concentration” is a critical factor that can help buyers or renters make sure they have the correct trailer for the job.
“There is no one-size-fits-all [solution] when it comes to trailers,” states Geisler. “It’s not enough to know a 55-ton lowbed can carry 55 tons. Informed operators also know just how much of the deck can handle that weight based on the manufacturer’s capacity rating. While some trailers will need the entire deck length to haul 55 tons safely, a trailer from another manufacturer might only need half the deck length for the same weight.”
Calculating the best fit, says Geisler, is partly a matter of safety. “Having a trailer rated in half-deck capacity gives operators a more realistic indication of what the trailer will be able to handle safely and without structural failure,” he comments.
Compliance is another key factor, says Geisler, and it is not always an easy one to determine. “The intended area of operation is almost as important as capacity when selecting a trailer,” he remarks. “Dealers, manufacturers and industry associations, such as the Specialized Carrier and Rigging Association (SCRA), have a wealth of information on this subject that they are willing to share with operators and managers, but operators are encouraged to submit a configuration to states they plan to operate in to ensure proper permitting,” he adds.
The longevity of the trailer also can be at stake when it is overloaded, says Geisler. “A single overload might not cause the trailer to fail, but it reduces the manufacturer’s safety factors and puts unnecessary stress on the trailer components, putting it at risk of future failure.”
Off-road equipment is likely to have an uneven weight distribution, adding yet more factors into this specialty hauling equation. Geisler says Talbert is among the manufacturers who “designs with a two-point rigid load base that accounts for the tire spacing—or hot spots—of large equipment and heavy machinery. This makes trailers with a half-deck rating more versatile and efficient for these loads.”
Geometry comes into play when trailer makers and users consider the camber angle of the trailer. “Camber is the term used to describe the arc that forms in the center of a well-designed trailer,” says Geilser. “It helps prevent excessive deflection in the main beams. When properly loaded to capacity, the arc will flatten, resulting in the trailer’s loaded deck height. A top-tier manufacturer can adjust camber in custom designs to meet the operator’s specific needs. In general, though, a trailer that presents a slight upward arc in the center has positive camber which will flatten with a full load.”
Between considerations tied to safety, compliance and return on investment, companies shopping for trailers and containers have numerous reasons to do their homework.