Deformed Bar

Summary

Deformed Bar - A deformed bar is a type of dowel used in a formed joint when minimal movement is desired in the joint.

Technical Information

A deformed bar can be used to create a formed restrained-movement joint. It provides load transfer across the joint in the same way a dowel does. Movement in the joint occurs when the bars yield.

During installation, the bars are set into the formwork when the first slab is cast, then the second slab is cast around them as they protrude from the first slab.

The bars bond well to the surrounding concrete due to their ribbed shape, improving their resistance to being pulled out of the slabs they are cast in. If the bars were to slide out of the slab with little resistance, the joint would widen more than the designer intended and the joint could not be considered as fully tied.

The bar dimensions are chosen so that the total cross sectional area of the bars across a joint is roughly equal to that of the fabric reinforcement in the rest of the slab. This helps to maintain uniform strength properties across the whole floor. The bars also need an area of 0.08-0.125% of the cross sectional area of the slab. Any less than this and there is a risk of a joint opening too wide. Any more than this and the risk of mid-panel cracking increases.