Links & Stirrups in RC Detailing

What Are Links and Stirrups?

In reinforced concrete (RC) detailing, links (closed rectangular or polygonal loops) and stirrups (open or closed U-shaped bars) are the transverse reinforcement that confine the longitudinal bars in a structural element. The terms are used interchangeably in many markets; German practice uses Bügel for the closed loop form most common in columns and beams.

Their structural roles are threefold: resisting shear and torsion forces in beams; confining the concrete core in columns to improve ductility and axial capacity; and preventing the longitudinal (main) bars from buckling outward under compression. Without adequate transverse reinforcement, a compression member can fail suddenly — a brittle, catastrophic mode that modern codes work hard to prevent.

Geometry and Shape Codes

Stirrup geometry is defined in the reinforcement schedule by a DIN 488-3 shape code (or BS 8666 equivalent for dual-standard projects). Common forms include:

• Shape code 51 — rectangular closed link, the standard column/beam stirrup
• Shape code 60 — triangular link, used where diagonal ties are needed in wide sections
• Shape code 13 / 14 — U-bar (open stirrup), placed in beams where cage assembly requires an open top
• Shape code 38 — helical (spiral) reinforcement, used in circular columns and pile cages

All bends must respect the minimum mandrel diameters in EN 1992-1-1 Table 8.1N. For B500B bars ≤ 16 mm the internal bend diameter is 4d; for bars > 16 mm it is 7d. Hook tails on links must extend at least 5d (or 50 mm, whichever is greater) beyond the bend to anchor the bar end in the concrete.

Stirrup Sizing: Bar Diameter

Eurocode 2 clause 9.2.2 sets minimum stirrup diameters for beams: not less than 6 mm and not less than 0.25 times the maximum diameter of the longitudinal bars. For columns (clause 9.5.3) the minimum is 6 mm or one-quarter the diameter of the largest longitudinal bar. In practice, 8 mm and 10 mm are the most common stirrup diameters for standard elements; heavily loaded columns or seismic designs may specify 12 mm or 14 mm links.

Spacing Rules Under Eurocode 2

Link spacing (pitch) controls shear resistance and confinement. For beams (EC2 clause 9.2.2), the maximum longitudinal spacing of stirrups is 0.75d (where d is the effective depth) and not more than 400 mm. Within a distance equal to twice the element depth from a support, spacing should normally be halved to account for the higher shear demand. For columns (clause 9.5.3) the maximum pitch is min(20 × minimum longitudinal bar diameter; 400 mm; least column dimension). Near column ends, within a length equal to the larger cross-section dimension, the spacing must be reduced by a factor of 0.6.

These are minimum requirements. The structural engineer’s design may specify closer spacing — particularly in seismic design to DCM (medium ductility class) or DCH (high ductility class) per EN 1998-1.

Grade and Standard Requirements

B500B is the required grade for links and stirrups in virtually all DIN 488 / EN 10080 compliant projects. Its k ≥ 1.08 and Agt ≥ 5.0 % give the ductility to deform without fracture at bends and under cyclic loading. B500A (often used in welded mesh) has lower ductility (Agt ≥ 2.5 %) and is not suitable where bending and cyclic loading are critical. For seismic zones or special ductility requirements (DCH), B500C (k ≥ 1.15, Agt ≥ 7.5 %) is specified. Steel Rebar Germany can supply B500B coils in diameters 6–16 mm for automated stirrup-making machines, or pre-bent stirrups to your shape code and schedule. See also our guide on starter bars and continuity strips and our cut-and-bend service.

Procurement: Cut-and-Bend to Schedule

Stirrups and links are almost always supplied as cut-and-bent elements rather than straight bar. Providing Steel Rebar Germany with your bar-bending schedule (BBS) in standard format allows us to produce elements to:

• DIN 488-3 shape codes (German / European projects)
• BS 8666 shape codes (UK-export or dual-standard projects)
• Any agreed dimensioned sketch for non-standard geometries

Each consignment ships with a Mill Test Certificate (EN 10204 3.1) traceable to the bar heat, plus packing list and, for export, a Certificate of Origin. Bundles are seaworthy packed at approximately 2 t for container or break-bulk shipment. Contact us via our quote page with your schedule and destination port.