DEFLECTION, SHORTENING AND CRACKING CAUSED BY SHRINKAGE IN REINFORCED SECTIONS, IN-SITU TOPPINGS AND COMPOSITE SLABS

Concrete shrinks. Steel doesn't, and the action of concrete shrinking and being resisted by steel reinforcement causes deflection of slabs and beams and shortening of columns and walls. A simple visualisation is given, and used to derive formulae for analysis. Current methods of calculating shrinkage curvature and deflection in reinforced sections are examined and a new method is proposed. The differential contraction between an in-situ concrete topping and an older substrate produces curvature and deflection of the composite unit. A method for calculating this is given, and the resulting effects are found to be significant in certain circumstances. The method is extended to consider shrinkage in in-situ slabs in composite construction. The deflection from shrinkage is found to be approaching span/750, and cracking in the slabs is predicted in some cases.

• INTRODUCTION

• SYMMETRICALLY REINFORCED CONCRETE SECTIONS

• SHRINKAGE DEFLECTION IN REINFORCED MEMBERS

• CONTRACTION OF IN-SITU CONCRETE TOPPINGS

• CONTRACTION OF IN-SITU SLABS IN COMPOSITE CONSTRUCTION

• CRACKING IN COMPOSITE CONCRETE SLABS

• REFERENCES