Effects Of Creep On New Masonry Structures

Creep can affect structures in two ways: deformations typically increase and loads (stresses) can be redistributed among structural components and, within a member, the constituent materials [1]. The effects of creep can be benefi cial, neutral, or detrimental for a structure: benefi cial, for example through the relief of stress concentrations, detrimental through increasing deformations. The latter can lead to a structure no longer meeting serviceability criteria. Stress redistribution can cause cracking, especially in cases where there is deterioration in strength over time due to environmental factors in that element of the structure which carries increasing load due to creep effects. Sometimes the two effects work together. Creep buckling is one example. An initial lateral imperfection in a column subject to axial load, or an initial eccentric load, causes an initial lateral displacement of the column. Consequently, there are higher compressive stresses on the inner curvature than on the outer curvature of the column. The side of the column under the higher stress creeps more than the other side, under the lower stress. The creep strains result in increasing lateral displacement. In turn, the secondary moment (the axial load times the lateral displacement) increases, increasing the stress on the inner curvature. Creep increases with the higher stress, so the lateral displacement increases more and more rapidly with the end result being a buckling failure of the column. An initial applied load less than the Euler buckling load for the end constraints of the column can thus cause a buckling failure sometime after load application. For some materials, the stress to initiate such failure can be as low as 60% of the failure stress in a monotonic