The structure must be designed so that it can safely carry the design ultimate dead, wind and imposed loads. The possible modes of failure are compression, tension, shear or punching, torsion and buckling. Approaches for determining the resistance of beams, columns etc are given in the design codes (e.g. BS 8110 or Eurocode 2 for buildings).
Appropriate safety factors are applied to the loads and the strengths of the materials. Typically dead and live loads are multiplied by 1.4 and 1.6 respectively; concrete and steel strengths are divided by 1.5 and 1.05 respectively. The layout of the structure and the interaction between the structural members should provide a robust and stable design.
In addition, structures should be planned and designed so that they are not unreasonably susceptible to the effects of accidents. In particular situations where damage to small areas of the structure or failure of a single element may lead to collapse of major parts of the structure should be avoided.