Deformed vs plain welded wire reinforcement: D-wire, W-wire and 80 ksi design

Two distinct wire geometries: W-wire vs D-wire

Structural drawings designate welded wire reinforcement using either a W or a D prefix:

• W-wire (Plain / Smooth Wire): Smooth, cylindrical cold-drawn steel wire. Used in standard flat sheets (such as 6×6 W2.9/W2.9 and 6×6 W4.0/W4.0) for temperature and shrinkage crack control in slabs on ground, composite deck, and precast utility structures.
• D-wire (Deformed Wire): Cold-worked steel wire with indented surface deformations (ribs or dimples) rolled into the wire shaft. Used in engineered precast structural panels, bridge girders, tilt-up shear walls, and foundation mats requiring shorter embedment and lap lengths.

The table below contrasts physical, mechanical, and code provisions across both wire types per ASTM A1064 and WRI WWR-500-R-26:

Concrete bond and development mechanics

The fundamental difference between W-wire and D-wire lies in how each transfers tensile stress to the surrounding concrete:

1. Plain W-wire anchorage

Because smooth cold-drawn wire develops minimal friction along its length, W-wire depends entirely on its welded cross wires. Under tension, the wire attempts to pull through the concrete, causing the transverse welded wires to bear directly against the concrete paste like miniature deadman anchors (Becker, 1949).

For this reason, building codes mandate that every development length and lap splice in plain welded wire reinforcement must contain at least one or two welded cross wires within the embedment zone (ACI 318-25 Section 25.4.7).

2. Deformed D-wire anchorage

Deformed wire incorporates cold-rolled surface indentations spaced along the perimeter of the wire. These deformations grip concrete mechanically along the entire length of the wire, identical to deformed rebar.

Because D-wire develops continuous bond along its shaft, it does not rely exclusively on welded cross wires for development. Under WRI Detail WWR.3 and CSA A23.3, structural lap splices with D-wire require shorter overlap distances, saving steel weight on large commercial projects.

High-strength 80 ksi design under ACI 318-25

Modern concrete codes increasingly prioritize material efficiency to reduce embodied carbon.

Under ACI 318-25 Table 20.2.2.4(a) and WRI Tech Fact TF 208-R-21, structural engineers can specify high-strength welded wire reinforcement with design yield strengths up to:

• fy = 550 MPa (80,000 psi) for non-prestressed flexure, axial, and temperature/shrinkage reinforcement.
• fy = 550 MPa (80,000 psi) for shear stirrups and shear reinforcement in beams and columns.

Specifying 80 ksi deformed welded wire reinforcement in place of standard Grade 400W (60 ksi) rebar allows designers to decrease total steel cross-sectional area by up to 25%, significantly reducing material costs and transport weight.

Ductility considerations for cold-drawn steel

Engineers must understand the stress-strain curve of cold-drawn wire compared with hot-rolled rebar.

Cold drawing increases yield strength through strain hardening, but reduces ultimate uniform strain before necking (Carrillo, Rico & Alcocer, 2016). ASTM A1064 requires cold-drawn wire to achieve a minimum reduction in area of 30% at failure, ensuring sufficient ductility for standard bending, handling, and flexural crack redistribution in slabs on ground. In high-seismic moment frames or seismic shear wall plastic hinge zones where ductile elongation exceeding 10% is mandated, Grade 400W rebar remains the designated choice under CSA A23.3 Chapter 21.