It could be either. Tandem simply means that the power unit has two drive axles which operate in tandem. It's common in both articulated and straight trucks.
You need to be more specific about the configuration. Is a single axle straight truck, a tandem axle straight truck, a tandem axle straight truck with additional lift axles, a tractor trailer...?
The "tandem" part means it has two drive axles, although it is possible for a tandem truck to be a 6x2 vehicle, and have only one of those be a live axle.
It sounds to me like you're describing a straight truck, rather than a semi-tractor. I'd need to know the model number before I gave you an answer... what you're describing could be either be a single or a tandem axle truck.
A tandem truck is a truck with two drive axles.
Yes. A Class 7 single axle straight truck exceeds the 26000 lb. GVWR. A semi truck is a Class 8 truck.
26000 lbs of cargo? A tandem straight truck, such as a flatbed or a dump, could haul that amount of weight legally.
Five
The length from the middle of the steer wheels to the center point between the drive tandems (for a tandem truck) or center of the single drive axle (on a single axle truck).
The average tandem axle truck can carry about 12 cubic yards of soil. Generally, a tandem axle truck has three axles.
A dump truck with two drive axles.
They're typically allowed, in the US, a gross vehicle weight of 54.000 lbs. How much that equates to in freight tonnage depends on the tare weight of the vehicle. A tandem dump truck can typically haul 15 tons. A tandem roll off with a 30 yard container is typically only good for 9 - 11 tons.
The FMCSR applies to all commercial vehicles, including straight trucks, vehicles under 26,000 lbs. GVWR, etc.