EFFECTS OF DEAD LOADS IN STATIC BEAMS

Although in Japan the collapse of structures caused by snow loads on roofs occurs every year, the damage is concentrated on steel structures and seldom occurs in reinforced concrete structures. Since the notable difference between both structures is in dead loads, dead loads can be considered to play an important part in causing the collapse of structures by snow loads. Accordingly, the varying deterrent effect of dead loads, which displacements and stress couples produced by live loads decrease by the existence of dead loads, is discussed in terms of its application. Therefore, the governing equation of beams, including the effect of dead loads, is formulated from Hamilton's principle. The existence and effectiveness of the varying deterrent effect can be proven from numerical calculations by the Galerkin method. Also, the key physical factors governing the varying deterrent effect of dead loads for beams, subjected to uniformly distributed static live loads, are shown in the closed-form solution derived by solving, in approximate terms, the proposed governing equation, taking into consideration the effect of dead loads. This paper suggests that to avoid the collapse of beams due to live loads the safety factor for lightweight structures should be raised to coincide with the safety factor for heavyweight structures. This is illustrated in an example. © ASCE.