• EN 1991-1-1: Actions on Structures - General Actions
• EN 1991-1-4: Actions on Structures - Wind Actions
• EN 1991-1-5: Actions on Structures - Thermal Actions
• EN 1991-1-7: Actions on Structures - Accidental Actions
• EN 1991-2: Actions on Structures - Traffic Loads on Bridges
• EN 1993-1-1: Design of Steel Structures - General Rules
• EN 1993-1-5: Design of Steel Structures - Plated structures without
• EN 1993-1-7: Design of Steel Structures - Plated structures with out-of-
• EN 1993-1-8: Design of Steel Structures - Joints
• EN 1993-1-9: Design of Steel Structures - Fatigue
• EN 1993-1-10: Design of Steel Structures - Material toughness
• EN 1993-1-11: Design of Steel Structures - Tension members
• EN 1993-2: Design of Steel Structures - Bridges
• Each document is accompanied by a National Annex
• BS 499: Welding terms and symbols
• BS 4395: Specification for high strength friction grip bolts and associated
nuts and washers for structural engineering metric series
• BS 5400 Part 2: Specification for Loads
• BS 5400 Part 3: Code of Practice for the Design of Steel Bridges
• BS 5400 Part 10: Code of Practice for Fatigue
• BS EN 10025 Parts 1 to 6: Hot rolled products of structural steels
Design Manual for Roads and Bridges
• BA9: Use of BS5400 Part 10
• BD13: Design of Steel Bridges
• BD37: Loads for Highway Bridges
• BA53: Bracing Systems for the Use of U-Frames in Steel Highway Bridges
Box girders have a clean, uninterrupted design line and require less maintenance because more than half of their surface area is protected from the weather. The box shape is very strong torsionally and is consequently stable during erection and in service; unlike the plate girder which generally requires additional bracing to achieve adequate stability.
The disadvantage is
that box girders are more expensive to fabricate than plate girders of
the same weight and they require more time and effort to design.
Box girders were very popular in the late 1960's, but, following the collapse of four bridges, the Merrison Committee published design rules in 1972 which imposed complicated design rules and onerous fabrication tolerances. The design rules have now been simplified with the publication of BS5400 and more realistic imperfection limits have been set.
The load analysis and stress checks include a number of effects which are generally of second order importance in conventional plate girder design such as shear lag, distortion and warping stresses, and stiffened compression flanges. Special consideration is also required for the internal intermediate cross-frames and diaphragms at supports.