ABSTRACT
Silfwerbrand (4) developed a method to calculate shrinkage stress on overlays based on the following assumptions:
a) Concrete in base and overlay are linear elastic materials
b) Poisson’s ratio ν is set to zero c) Plane sections remain plane after bending
(Bernoulli’s hypothesis) d) The shrinkage of overlay is εsh throughout e) The shrinkage of the base is neglected
complete interaction
g) The movement of concrete edges are free
The shrinkage stress σ occurred in overlay due to restrained shrinkage is estimated using the following equations:
where εsh, E∗ and µ are shrinkage of overlay, modified elastic modulus of overlay and degree of restraint, respectively. The degree of restraint is affected by m and α which are, respectively, ratio of elastic modulus of concrete base E2 to E∗ and ratio of depth of overlay d to total thickness of overlay plus concrete base h. Creep coefficient is used to obtain E∗ from elastic modulus of overlay E1.
