The Structural Engineer's Corner

Eng. Onorio Francesco Salvatore

Traffic loads on road bridges: the Load Model 2 (LM2) in Eurocodes

Written By: Lexatus - Nov• 10•13

Traffic loads 9 - Onorio

The Load Model 2 (LM2) is a single axle model, which is applied when a local verification for short structural elements is required. Such elements can be crossbeams, upper flange stiffeners of othotropic decks or deck panels of composite slabs with steel sheeting. The internal forces due to LM2 may then be more critical compared to those of LM1. This can also happen at the vicinity of the expansion joints.

LM2 is applied at any location of the carriageway and consists of a single axle load with a magnitude equal to βQ x Qak, where βQ is an adjustment factor whose value may be defined in the National Annex. The EN 1991-2 recommend:

βQ x Qak = αQ1 x Qak = 400 kN

However, when relevant, only one wheel of 200 βQ (kN) may be taken into account.

The contact surface of the wheels is of rectangular shape with dimensions 0.35 x 0.60 m² corresponding to twin tires. Therefore, LM2 wheels result in different stress distributions in the deck slab than LM1 ones.

In the vicinity of expansion joints, an additional dynamic amplification factor should be applied.

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Eng. Onorio Francesco Salvatore

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