الفهرس 
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Abstract
The common type of a truss bridge generally consists of two main girders, an upper and a. lower wind bracing and an adequate number of cross frames.
In traditional bridge design, the usual method for determing the for¬ces in the members of the bridge, is based on the assumption that the bridge is to be built up ofa group of vertical and horizontal plane trusses acting independently on each other. Where the vertical loads are transmi¬tted by the vertical main girder, the horizontal loads are resisted by the horizontal wind bracing then transmitted through the end transverse bracing to the bearings of the bridge.
In reality, the whole bridge acts as a space structure. The vertical loads develop axial forces not only in the main girders, but also in the horizontal wind bracing as well as in the transverse bracing. This explains why the planar analysis may lead in many cases to erroneous results.
Thus, it is important in structural design to consider the behaviour of the truss bridges as space structures rather than a group of individual planar elements, otherwise the wind bracing will be overstressed by addi¬tional axial force which was ignored in their design, while the main gir¬ders may have cross sections different from those required.
This thesis is intended to discuss the behaviour of simply supported and continuous br dges when they are treated as space structures. Also the
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