Buff strength is a design term used in the certification of rail rolling stock. It refers to the required resistance to deformation or permanent damage due to loads applied at the car's ends, such as in a collision. Particular emphasis on buff strength is placed in the United States, with buff strength requirements there being higher than in Europe.
United States
Buff strength requirements grew out of best-practice design standards during the latter part of the nineteenth century. By the twentieth century, a design limit of was required by federal approval agencies. This was upped to for certain categories in 1945.
Federal requirements for buff strength were set in 1999 at for all passenger-carrying units, unless reduced by waivers or special order. The Federal Static and Strength Regulation (49 Code of Federal Regulations § 238.203) requires that a passenger rail car be able to support a longitudinal static compressive load of without permanent deformation.
There are other strength requirements associated with end-structure design. 49 CFR § 238.211 specifies that the cab ends of locomotives, cab cars, and self-powered multiple-unit cars have lead ends capable of supporting longitudinal force at the top of the underframe, and of force above the top of the underframe.
Europe
There are multiple certifying and approving agencies in Europe, so universal agreement on strength standards is not guaranteed. A 1977 German standard (VÖV 6.030.1/1977) presented values which have been followed by some other countries. The document was revised in 1992 and is presently known as VDV Recommendation 152 - Structural Requirements to Rail Vehicles for Public Mass Transit in Accordance with BOStrab.
In 1995 the European Common Market Committee for Standardization issued a draft document, Structural Requirements of Railway Vehicle Bodies. It mandated differing design loads for vehicles in differing categories, ranging from for tramways to for passenger coaches and locomotives.
In general the European approach to crashworthiness of passenger coaches puts more emphasis on
crumple zone
Crumple zones, crush zones or crash zones are a structural safety feature used in vehicles, mainly in automobiles, to increase the time over which a change in velocity (and consequently momentum) occurs from the impact during a collision by a ...
s rather than buff strength, meaning that the required design loads are less than those in the United States. This is generally agreed to reduce construction costs.
See also
*
Compressive strength
In mechanics, compressive strength (or compression strength) is the capacity of a material or Structural system, structure to withstand Structural load, loads tending to reduce size (Compression (physics), compression). It is opposed to ''tensil ...
*
Container compression test
The container compression test measures the compressive strength of packages such as boxes, drums, and cans. It usually provides a plot of deformation vs compressive force.
It is commonly used to evaluate shipping containers made of corrugated f ...
*
Crashworthiness
Crashworthiness is the ability of a structure to protect its occupants during an impact. This is commonly tested when investigating the safety of aircraft and vehicles. Different criteria are used to figure out how safe a structure is in a crash, ...
*
Deformation (engineering)
In engineering, deformation (the change in size or shape of an object) may be ''elastic'' or ''plastic''.
If the deformation is negligible, the object is said to be ''rigid''.
Main concepts
Occurrence of deformation in engineering application ...
*
Headstock (rolling stock)
A headstock of a Railroad car, rail vehicle is a transverse structural member located at the extreme end of the vehicle's underframe. The headstock supports the railway coupling, coupling at that end of the vehicle, and may also support Buffer ( ...
*
Railworthiness
References
Rail transport
Deformation (mechanics)
{{loco-stub