What distributed load can 2 HEB 240 handle?

[Öhrlund]

Length 4.5 m, freely supported on two supports. They should function as a bridge for a tractor (1570 kg) + single-axle small logging trailer (1000 kg) + a small load of firewood (2000 kg). Total 4600 kg. Tractor's wheelbase (2 m). Distance between tractor's rear axle and trailer's axle (4.2 m). Approximate track width 1.5 m. The beams should be connected with 3 IPE 160 (75 kg) to prevent tipping. The bridge deck is planned to be pine planks (700 kg). What deflection can be tolerated? 1/500, 1/200? Or even more? Total load that the beams should carry = 5.3 tons (distributed load). Does anyone have a calculation of what these 2 HEB 240 can withstand?

 

[huggan]

(5*Q*L^3)/(384*E*I)

Q = Distributed load in Newton
L = Span in
E = 210000 for steel
I = found in beam tables and increases with the beam's dimensions, HEB 240 = 11260 * 10^4

Deflection should be calculated as L/400

These beams have no problem with this load, and if we assume your load of 4600 kg on a beam, it would result in a deflection of 2.3 mm and L/400 gives 11.3 mm maximum deflection.

 

[Öhrlund]

Thank you "huggan" for your calculation and response to my beam consideration. The deflection does not seem to be significant with these loads, but it is a small tractor we're dealing with. It is a Volvo BM 320, a small mosquito compared to the giants many have today. I will take your formula and your calculation, and hope to start the beam project and get across the creek. Once again, thank you for your help!