Design Simpson Strong-Tie Screws to Eurocode 5

Simpson Strong-Tie supplies structural solutions worldwide, with a portfolio spanning connectors, anchors and fasteners for timber, concrete and masonry construction, backed by in-house technical and design support. The ANZ screw integration is built on European Technical Assessment ETA-13/0796, reissued on 16 February 2022.

The ANZ integration carries seven screw families. Four are assessed under ETA-13/0796 and hold the characteristic data used for Eurocode 5 connection design:

• ESCR, washer head, partial thread, 8 mm, 80 to 320 mm.
• ESCRC, countersunk head, partial thread, 8 mm, 80 to 320 mm.
• ESCRFT, full thread, countersunk head in 8 and 10 mm, 180 to 350 mm, and cylinder head in 10 mm, 450 to 500 mm.
• ESCRFTZ, cylinder head, full thread, 8 mm, 120 to 400 mm.

All four are hardened or heat-treated carbon steel, yellow zinc plated, with a T40 six-lobe drive, in service classes 1 and 2. Characteristic design values are read from the database and applied at calculation time rather than interpolated, so no per-article numbers are printed here.
Three further families sit in the ANZ database outside that assessment: SDWS22 (washer head, 7.8 mm), which the integrated data links to Declaration of Performance DoP-h10/0017 under EN 14592; SDWS27 (flat head, 9.8 mm, 316 stainless steel); and SDWC (cylinder head, full thread, 6 mm). These are handled separately and are not part of the Eurocode 5 connection design set below.

The assessed families support:

• Solid timber, glued laminated timber, cross laminated timber and LVL.
• CLT face fixing and CLT edge fixing.
• Timber-to-steel connections.
• Insertion at an angle.
• Compression and tension reinforcement perpendicular to the grain, using the fully threaded ESCRFT and ESCRFTZ.
• Service classes 1 to 3.

• Lateral capacity follows the screw-to-grain angle. Embedment strength carries the factor 2.5cos²α + sin²α on the angle between screw axis and grain, in both non-predrilled and predrilled members, so a screw driven at an angle is not designed on the perpendicular value.
• Cross laminated timber is treated as its own case. The edge surface has its own embedment expression, 20 divided by the square root of the outer thread diameter, independent of the screw-to-grain angle, and CLT carries its own plane-surface and edge-surface spacing sets for a minimum panel thickness of 10d.
• Spacing departs from the Eurocode 5 defaults in both directions. Laterally loaded screws follow the nail rules across the whole range, keyed to drill tip and pre-drilling rather than diameter, with minimum member thickness of 30 mm at 8 mm and 40 mm at 10 mm. For axially loaded screws a tighter set of a1 = 5d and a2 = 2.5d is allowed where a1·a2 is at least 25d², with the end distance to the centre of gravity of the threaded part at 5d rather than 10d.
• The rope effect is dropped under combined loading. Where a screw carries axial and lateral load together, the rope-effect contribution is left out of the lateral capacity entirely, against the 100 per cent of the Johansen part Eurocode 5 otherwise permits for screws.

The screws assessed under ETA-13/0796 are available in:

• the Screw module;
• the connection detail calculators: panel-to-panel (half-lap, spline and butt joint), slab-to-wall, wall-to-wall, floor-to-wall;
• the rib-deck calculator, for flexible connection design to Eurocode 5.

The fully threaded ESCRFT and ESCRFTZ, which carry the reinforcement marking in the database, additionally appear in the reinforcement connection details: beam notch, beam penetration, and beam compression perpendicular to grain.

Design follows EN 1995-1-1, with axially loaded screws verified to §8.7.2. The withdrawal expression of §8.7.2(4) applies to screws with an inner-to-outer thread ratio between 0.6 and 0.75, and the integrated diameters sit between 0.61 and 0.66. Both the 2004 and 2025 editions are supported. ETA-13/0796 supports CE marking. It is a European assessment and does not cover the AUS or NZ standards: the same product data is used for design in the AUS and NZ markets in accordance with the applicable design standards there.