Design complex timber connections to Eurocode 5 (EN 1995) and the latest FprEN drafts. Analyze Shear, Axial, and Moment actions on multi-plate configurations in seconds.
Connection design is often the bottleneck in mass timber engineering. The complexity of the Johansen Yield Equations, combined with strict spacing rules and brittle failure modes, makes manual calculation slow and error-prone.
The SPEC Toolbox Dowel & Bolt Module is a complete transformation of how engineers handle connection complexity. It moves beyond simple “Shear Capacity” to a true Combined Actions Analysis. Whether you are designing a double-shear truss node, a moment-resisting portal frame knee, or a heavy beam-to-column bracket, this tool provides instant verification to EN 1995-1-1 and prepares you for the future with FprEN 1995:2025 checks.
This tool utilizes a dynamic visual engine to optimize dowels, bolts, and steel plates in real-time. It performs a rigorous analysis of:
1. The Johansen Yield Theory (Automated)
Eurocode 5 requires checking multiple failure modes—from timber embedment failure to fastener yielding (plastic hinge formation).
Our calculator runs the full matrix of equations for every load case. It automatically identifies whether the failure is ductile (steel yield) or brittle (wood crushing) and applies the correct “Rope Effect” contribution ($F_{ax,Rk}/4$) where applicable.
2. Combined Actions (Shear + Axial + Moment)
Real-world connections rarely see pure shear. A truss chord connection sees shear and tension. A portal frame knee sees moment.
We use an Elastic Analysis method to distribute forces to individual fasteners based on their stiffness and distance from the center of rotation. This gives you the “True Behavior” of the group, ensuring no single bolt is overloaded.
3. Steel Plate Verification
A strong bolt is useless in a weak plate. The module integrates Eurocode 3 (Steel Design) checks for the metal components.
It verifies:
Load Carrying Capacity ($F_{v,Rd}$):
$$F_{v,Rd} = \min \left( \text{Johansen Yield Modes} \right) + \Delta F_{v,rope}$$
The tool automatically limits the rope effect contribution to the strict Eurocode limits (max 15% or 25% depending on the fastener type).
Group Effect ($n_{ef}$):
$$n_{ef} = n^{0.9} \sqrt[4]{a_1 / (13d)}$$
For fasteners in a row parallel to the grain, the effective number of bolts is reduced to account for uneven load distribution. The tool calculates this automatically based on your spacing ($a_1$).
Interaction Formula (Combined Loads):
For bolts subject to combined shear ($F_{v,Ed}$) and axial tension ($F_{ax,Ed}$):
$$\left(\frac{F_{v,Ed}}{F_{v,Rd}}\right)^2 + \left(\frac{F_{ax,Ed}}{F_{ax,Rd}}\right)^2 \le 1.0$$
In Eurocode 5, Bolts have nuts/washers and rely on the “Rope Effect” for extra strength. Dowels are tight-fitting smooth pins with no rope effect. Our calculator supports both, plus fitted bolts.
Yes. Block Shear (tearing out a “chunk” of wood) is often the governing failure mode for groups of bolts loaded parallel to grain. We apply the rigorous checks from Annex A of Eurocode 5.
Yes. We have integrated the latest draft provisions from the “Second Generation Eurocode,” allowing you to future-proof your designs or compare current EC5 results against the upcoming standard.
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