ACROSS the transverse joint and they keep the two slabs at the same height.They are of mild steel round bars, bounded on one side and free on the other side.Normally have 25 mm to 40 mm diameter and 400 - 500 mm length.The stress in dowel bars is given by Bradbury analysis. Tie bars: Tie bars used for holding faces of rigid slabs in contact to keep AGGREGATE interlock. They are ALSO used in the plain jointed concrete pavement to connect two lanes.They are used to reduce transverse cracking.Tie bars avoid separation and differential deflection in lanes.They are not designed to work as a load transfer device.