Dowel for pavement joints

• US 4,449,844 A
• Filed: 09/24/1982
• Issued: 05/22/1984
• Est. Priority Date: 05/11/1981
• Status: Expired due to Fees

• Current Assignee: Torbjorn J. Larsen
• Original Assignee: Torbjorn J. Larsen
• Inventors: Larsen, Torbjorn J.
• Primary Examiner(s): Purser, Ernest R.
• Assistant Examiner(s): DelSignore, Mark J.
• Application Number:
  US06/422,672
• Time in Patent Office: 606 Days
• Field of Search: 404/56, 404/61, 404/59, 404/62, 404/63, 404/60, 404/70, 52/573, 52/586, 52/396
• US Class Current: 404/60
• CPC Class Codes: E01C 11/14 Dowel assembly ; Design or construction of reinforcements in the area of joints coupling devices for prefabricated units E01C5/005; combined with characteristic packings E01C11/08 - E01C11/12; removable holders E01C23/045

Abstract

A device for transferring vertical shear stress and bending moments across transverse joints in concrete pavement slabs and the like, and for simultaneously controlling the joint gap width. A dowel is formed from a continuous length of steel bar, treated to cause its outer ends to bond to concrete and its central portion treated to prevent bonding to concrete. The outer ends of each bar is formed to permit the center portion to be disposed near either the top surface or bottom surface of the slab sections and the outer ends along the neutral axis of the slab sections. The bars are used in pairs with one center portion adjacent the top surface and the other one adjacent the bottom surface. A multiplicity of such dowels is embedded in the concrete of a continuously-poured concrete slab aligned with the roadway and in a spaced relationship across the slab. The concrete is grooved before curing across the slab and over the central portions of the dowels. As the concrete cures, the outer ends of the dowels bond to the concrete while the central portions remain unbonded causing a joint crack and strain produced in the concrete due to shrinkage which is partially transferred to the unbonded steel which acts as a latent spring to subsequently control the gap width. The dowels additionally serve to transfer bending moments and vertical shear stresses from live loads across the pavement joint.

Claims

1. A device for simultaneously controlling the width of a joint between concrete pavement slab sections, transferring vertical shear stresses across said joint, and transferring bending moments across said joint, comprising:

a pair of elastic bars, each of said bars having two end portions and a central portion and having a length short relative to the length of the slab sections, said pair of bars disposed symmetrically and longitudinally across said joint wherein one bar of said pair is disposed with its central portion near the top surface of the slab sections, and the other one of said pair is disposed with its central portion near the bottom surface of the slab sections, and arranged to transfer vertical loads and bending moments caused by a traffic load of a desired maximum value applied to one slab section across said joint to the adjacent slab section, said pair of bars selected to withstand such vertical loads and bending moments without deformation, each of said pair of elastic bars formed to dispose said end portions of said bars essentially along the neutral axis of the concrete slab sections; and

means for partially transferring longitudinal stress comprising bonding means associated with said end portions of said bars for bonding said end portions to the concrete slab sections along the neutral axis, and bonding prevention means associated with said central portion of said bars for allowing movement of said central portion with respect to the concrete slab sections, said stress transferring means partially transferring longitudinal stress in the concrete slab sections due to contraction and expansion of said pair of elastic bars, said elastic bars also selected to operate within their elastic limit over a desired stress range in such concrete slab sections to limit the joint gap width to a selected value.

2. A non-reinforced jointed concrete pavement slab having a controlled transverse contraction joint gap width comprising:

a multiplicity of independent elastic load transfer dowels formed from lengths of concrete-reinforcing bars short relative to the length of a section of said concrete slab, said dowels embedded longitudinally in said slab and arranged to symmetrically span the joint, said dowels disposed in an essentially parallel relationship over the extent of the joint, with the number and cross-sectional areas of said dowels selected to transfer vertical traffice loads of a desired maximum value across the joint without deformation on said dowels, said dowels arranged in pairs with one of each of said pair having its center section disposed near the top surface of said slab, and the other one of said pair having its center section disposed near the bottom surface of said slab; and

means for partially transferring longitudinal stresses in the sections of said concrete slab to said elastic dowels comprising deformation of the ends of each of said bars causing said ends to bond to the concrete to said slab, and a plastic covering of the center sections of each of said bars for preventing said center sections from bonding to the concrete thereby allowing said center sections to move relative to the surrounding concrete, with the number and cross sectional areas of said dowels also selected to operate in tension within their elastic limits over a desired stress range sufficient to maintain a selected joint gap width, in which said ends of each of said pair of dowels formed to lie and bond along the neutral axis of said slab, with the numbers and cross-sectional areas of said dowels also selected to additionally transfer bending moments caused by desired maximum traffic loads applied to one of said slab sections across the joint to the adjacent one of said slab sections without deformation of said dowels.