Porosity Effects on Folded-Plate Structures by Finite Strip Method and Rheological Dynamics

In this paper, porosity is treated as a long-term phenomenon of composite folded-plate structures (FPS) within the harmonically coupled finite strip method (HSFSM) for finite strains. Large inelastic deformations are analyzed by rheological dynamics, for which a detailed explanation of porosity limit values based on the strain energy density is provided by Milašinović. The characteristics of concrete with zero porosity are specified based on defined porosity limits while changes in the mechanical properties of concrete as a function of porosity are determined only on the basis of the results of non-destructive testing with P and S wave velocities. The reliability of the proposed model was confirmed by comparing the numerically calculated and geodetic measured long-term deflections of the composite wood-lightweight concrete girder under self-weight loading after six years. The difference between the calculated deflection of 15 mm and the measured deflection of 13.15 mm is small. Taking the effect of porosity into account, the increase in deflection due to creep is reduced. The long-term effect of porosity on the stresses in a prestressed beam is also numerically investigated.