Bridge standards generally include a load model, deemed to represent the characteristic maximum load to be expected in the return period. In the past, these load models were agreed by standard drafting committees of experts but today, this situation is changing. It is now possible to measure the components of bridge traffic load, to weigh trucks, using weigh-in-motion (WIM) technologies. With extensive WIM databases, it is possible to calculate the maximum expected load effect in the specified return period. This is an active area of research, addressing issues of opposing direction lanes, side-by-side (same direction) lanes, traffic growth, permit/non-permit vehicles and long-span bridges (see below). Rather than repeat this complex process every time a bridge is to be designed, standards authorities specify simplified notional load models, notably HL-93, intended to give the same load effects as the characteristic maximum values. The Eurocode is an example of a standard for bridge traffic loading that was developed in this way.
Bridge standards generally include a load model deemed to represent the characteristic maximum load to be expected in the return period In the past these load models were agreed by standard drafting committees of experts but today this situation is changing It is now possible to measure the components of bridge traffic load to weigh trucks using weigh-in-motion (WIM) technologies With extensive WIM databases it is possible to calculate the maximum expected load effect in the specified return period This is an active area of research addressing issues of opposing direction lanes side-by-side (same direction) lanes traffic growth permit/non-permit vehicles and long-span bridges (see below) Rather than repeat this complex process every time a bridge is to be designed standards authorities specify simplified notional load models notably HL-93 intended to give the same load effects as the characteristic maximum values The Eurocode is an example of a standard for bridge traffic loading that was developed in this way