JUST-IN-CASE FACTOR.

With the preciseness of computer analyses at hand, engineers no longer have to rely on instinct and prior experience to incorporate factors of safety into their structural designs. They have to be reminded of the guiding principle that there be multiple load paths in any given structure 'just in case. ' The AASHTO Standard Specification for Highway Bridges, the only bridge code that refers specifically to redundancy at all, compresses a definition between dashes in one sentence: 'Main load carrying components subject to tensile stresses that may be considered non-redundant load path members-that is where failure of a single element could cause collapse-shall be designed for lower allowable stress ranges. ' The analysis made to prove redundancy can also prove that multiple elements aren't always enough. It's the multiple paths that count, and each path must be thoroughly checked out.