Consideration of Net Cross-Section for Tensile Stress According to EN 1993-1-1

Design of Tension Resistance According to EN 1993-1-1

According to DIN EN 1993‑1‑1, Chapter 6.2.3 (2), the tension resistance of a cross-section weakened by holes results from the minimum of the following design values:

The net cross-section area is to be determined from the gross cross-section area minus all openings and holes for fasteners. Depending on the arrangement of the bolt holes, the hole deduction area to be applied is adjusted to the critical crack line.

Entering Data in RF-/STEEL EC3

By default, the design of the tension resistance in the add-on module is only performed considering the plastic tension resistance of the gross cross-section (Formula 1). The design according to Formula 2 can be activated by selecting the "Net Cross-Sectional Area" option in the "Parameters of Members" input window. You can enter a net cross-section area A_net for member start (x = 0) and member end (x = l). To enter the same net cross-section area for several members at the same time, we recommend using "Set input for member no."

Entering Net Cross-Section Area in Add-on Module

Then, both design values of the tension resistance are calculated and the design is performed according to DIN EN 1993‑1‑1 with the minimum value.

Modification for Design of Angle Sections Connected on One Side

For asymmetrically connected components, such as angle sections connected on one side to a leg, DIN EN 1993‑1‑8 provides additional regulations. Accordingly, the angle connected on one side for tensile loading may be designed like a centrally loaded angle if the load-bearing capacity is determined with an effective net cross-section.

The effective net cross-section can be determined by means of modification factors depending on the number of bolts and the hole spacings. An additional reduction factor of 0.9, as in Equation 1, is no longer required for the design with the net cross-section. The input window in RF‑/STEEL EC3 does not allow you to enter the effective net cross-section directly, but the net cross-section area to be entered can be adjusted to the design in the add-on module by means of a simple conversion.

Design with Effective Net Cross-Section in Add-on Module

Example

Flat bars 60 x 8 mm were selected as crossings in the Y-direction. The net area results for the fastening with an M20 screw in the critical crack line

A_net = 4.8 cm² - 2.2 cm × 0.8 cm = 3.04 cm²

The following design resistances result for the S235 material:

N_pl,Rd = (4.8 cm² ⋅ 23.5 kN/cm²) / 1.0 = 112.8 kN

N_u,Rd = (0.9 × 3.04 cm² × 36 kN/cm²) / 1.25 = 78.8 kN

Result for Crossing 1 in RF-STEEL EC3

For the crossing in the X-direction, isosceles angle sections L 75 x 8 were selected in S355. The connection is to be realized on an angle leg with two M20 screws, one behind the other. The dimensions are selected as follows:

e₁ = 40 mm

p₁ = 60 mm

e₂ = 30 mm

The effective net cross-section area for this connection situation results from the factor β2 according to EN 1993‑1‑8

β2 = 0.44

A_net,eff = β2 ⋅ A_net = 0.44 ⋅ (11.4 cm² - 2.2 cm ⋅ 0.8 cm) = 4.21 cm²

The following design resistances result for the S355 material:

N_pl,Rd = (11.4 cm² × 35.5 kN/cm²) / 1.0 = 404.7 kN

N_u,Rd = (4.21 cm² ⋅ 49 kN/cm²) / 1.25 = 164.9 kN

The input in RF‑STEEL EC3 is carried out with the equivalent net cross-section area:

A_net* = 4.21 cm² / 0.9 = 4.67 cm²

Result for Crossing 2 in RF-STEEL EC3

Knowledge Base

KB 000565 | Consideration of Net Cross-Section for Tensile Stress According to EN 1993-1-1