Widerlager

Widerlager is a structural term used in civil engineering and bridge design to describe the end support of a span that resists the horizontal thrust produced by arches or vaults, as well as transferring vertical loads to the foundation. In arch bridges and similar structures, Widerlager act as the counter-support to the arch thrust, providing lateral restraint and bearing capacity at the ends of the span. They are typically contrasted with Auflager, which are the simple supports that primarily transfer vertical loads without resisting thrust.

Widerlager are usually implemented as abutments or counterfort-type supports. An abutment is a vertical mass, often with wing walls, that carries both the vertical reaction from the deck and the horizontal thrust of the arch. A counterfort arrangement uses vertical walls connected to a common foundation to increase resistance against thrust.

Key components commonly involved in Widerlager include the foundation or footing, the main retaining body, facing elements, wing walls or counterforts, and the bearing surfaces for the deck. Bearings or seating surfaces allow limited movement due to thermal expansion, settlement, or seismic effects, and joints accommodate differential movement between the arch and the foundation.

Design considerations for Widerlager focus on adequate bearing capacity and stability, control of settlements, resistance to horizontal thrust, protection against scour or erosion in hydraulic environments, drainage, frost effects, and durability under soil and groundwater conditions. Materials frequently used are reinforced concrete, masonry, or stone, with modern practices incorporating appropriate bearing interfaces to accommodate movement.

In summary, Widerlager are end supports that resist arch thrust and transfer loads to the ground, forming a critical element in the safe and durable functioning of arch bridges and related structures.