抄録
Stresses and strains are induced in built-up roof membranes by joint movement in the substrate. In this papar, the stresses and strains are analysed under constant temperatures, introducing the visco-elasticity of a roofing felt and a bonding asphalt. The modulus of the material in a small element in the membrane is determined by its stress and strain at the moment and is not equal to that of the other element. Therefore the membrane is replaced by the equivalent model which consists of tensile elements for the roofing felt and shearing elements for the bonding asphalt. Assuming that the materials obey the power rule, visco-elastic behavior of the built-up roof membrane is analysed by the simulation method under constant temperatures, 0, 20, 40 and 60℃. It is almost impossible to measure the induced stresses or strains, then the validity of the analysis method is discussed by the comparisons of the calculated tensile loads with the observed ones in the substrate joint opening tests of the membranes. This visco-elastic analysis method can be regarded as useful at low temperature when the joint gaps in the substrates open wider and larger strains are induced, because the observed and calculated tensile loads acceptably agreed with each other at 0 and 20℃. The equation expressing strains based on the theory of elasticity can be used as the simplified calculating method of the strains when substituting the moduli of the materials at the elapsed time of concern.
