Eurocode 3 Masterclass: Dive Deep into Steel Design with RFEM 6!

Opens the course and sets out what it covers: the calculation principles for beam structures, the approach to imperfections, the influence of structural deformation and joint stiffness, and an overview of the verification methods. Also points to the 90-day trial and the free student version of RFEM 6.

Walks through the course outline and places Eurocode 3 among the standards. Explains how EC3 splits into sub-codes: EC3-1-1 for general rules and rules for buildings, EC3-1-5 for plated structural elements. National annexes then change partial safety factors and design approaches through NDPs and NCCI.

Introduces the EC3 safety concept as a comparison of design effect and design resistance, with the characteristic resistance divided by a partial safety factor. Distinguishes gamma M0 for cross section design, gamma M1 for stability and gamma M2 for tension failure, and shows where the German National Annex differs.

Covers the steel grades Eurocode 3 supports and their nominal yield strengths. Opens the RFEM 6 material library, filters by region and material type, and shows where the modulus of elasticity, shear modulus and grade-specific values are already built in.

Introduces the topics of the structural analysis chapter: global analysis for internal forces, the effect of deformed geometry, imperfections and joint stiffness. Sets the alpha-crit limits above which first-order theory is permitted, 10 for elastic and 15 for plastic global analysis. Slides only.

Runs the 2D stability model first order, then reads the critical load factor from an eigenvalue analysis: 33.6, above the limit of 10, so first-order theory is sufficient. Then swaps the section for an IPE 200, where the factor falls to 2.8 and the second-order moment rises from 60 to about 91 kNm.

Extends the stability check from a single load case to load combinations. Creates an imposed load case and builds combinations with the combination wizard through design situations, then reads the minimum critical load factor of 13.46 for combination 3 from the stability analysis results.

Separates geometric imperfections such as sway from structural ones such as residual stresses, and explains why Eurocode 3 covers both with equivalent geometric imperfections. Sets out the sway base value of 1/200 with the factors alpha m and alpha h, and the bow imperfection tables.

Creates an imperfection case in RFEM 6 for the frame used earlier: a new case in the data navigator, the global type, the direction set to global X. The assignment starts with all three members and is then reduced to members 1 and 3, leaving the beam out.

Compares the three methods for stability design from the EC3-1-1 commentary: global and local imperfections with cross section checks only, global imperfections with an equivalent member check, and no imperfections with first-order internal forces. Closes with joints as rotational springs under Eurocode 3 part 1-8.

Applies the calculated rotational stiffness as a spring in the model and shows how parameterizing values in RFEM 6 lets member length, loads and stiffness be changed together from a single window.

Introduces design values of resistance in the ultimate limit state. Explains how a cross section is classified part by part from the c/t ratio of each flange half and the web, and why pure compression pushes a section into the higher classes faster than bending.

Classifies an IPE 300 in S355 under pure compression and under bending in the steel design add-on. Cross-checks the first sub-panel against the 9-epsilon limit, then follows the class 4 web through to the reduced effective area of 52.7 cm2 against the gross 53.81 cm2.

Compares IPE and HEA sections under compression and bending and shows how a higher steel grade moves a section into class 3 or 4 sooner. Sets out the elastic and plastic resistance formulas that follow from the class, including the shear force interaction hidden in the second formula.

Sets up a full cross section design on the ULS section resistance model: activating the steel design add-on, choosing the standard and national annex, and working through the design configurations and the list of members to design in the tables. Also introduces member sets.

Shows the same design settings reached from the member itself rather than the tables. Opens the member dialog and walks through its five tabs, including design types and the design configurations tab where the ultimate, serviceability and fire resistance configurations are assigned.

Runs the design and reads the results: design ratios by member, by design situation and by section. Opens the governing check to see the plastic resistance per Section 6.2.9.1, then forces an elastic design so the von Mises stress criterion is used instead.

Explains why shear buckling has to be verified separately: cross section classification only covers longitudinal stresses, so shear stresses fall outside it. Sets out the two criteria RFEM 6 checks and the slender welded I sections where buckling actually occurs.

Checks a welded slender I section under 200 kN/m for shear buckling. Runs the design, reads why the check is not fulfilled, adds stiffeners to the web and re-runs to see the effect on the result.

Sets out the two routes to a stability design: a cross section check with all imperfections and second-order effects included, or a design method that accounts for what the structural analysis left out. Explains flexural, torsional and lateral torsional buckling and the critical force belonging to each.

Designs a column for stability in the 2D stability model. Activates the steel design add-on and the national annex, then defines effective lengths and nodal supports, including an intermediate node for a lateral support on the weak axis, and reads the buckling lengths from the design details.

Applies the same stability settings to a beam. Divides the member into four sections with three intermediate nodes, then uses the select-member shortcut so the nodal supports table fills automatically, and sets lateral and torsional restraint.

Designs with the general method of Section 6.3.4. Creates boundary conditions for the beam with the select-member shortcut, then shows that a member can carry either boundary conditions or effective lengths but never both, and clears the effective lengths so the general method governs.

Notes that Eurocode 3 leaves the deflection limits to the engineer or the client. Runs the design on the SLS model and fails at a ratio of 1.82, with 24.8 mm against the 13.3 mm limit, then switches the placement reference to the deformed segment ends, which brings it to 12.7 mm and passes.

Corrects the limit values for a beam with a cantilever, where the default L/300 does not apply. Creates a design support at the member start and sets the cantilever limit to L/150 through the design supports and deflection tab.

Opens the first practical example, a tapered half-frame. Reports that the in-plane eigenmodes were checked beforehand against the critical load factor of 10, so no in-plane imperfections are needed, and sets the load position on the profile edge to keep the destabilizing effect.

Runs the stability design of the tapered half-frame with the general method. Combines the beam and column into a member set so the eigenvalue solver captures the real support conditions between them, then defines the boundary conditions and the nodal supports including the intermediate node.

Adds torsional warping to the tapered half-frame so the design accounts for all internal forces including the torsional moment. Activates the torsional warping and structure stability add-ons, generates the imperfections from the buckling mode, and reads a governing design ratio of 0.4.

Opens the platform beam example: two IPE 550 principal beams connected by cross beams, taken from a technical article supplied with the course. Compares the pure stress analysis first, then runs the equivalent member method, which fails: about 450 kNm against a design buckling resistance of 260 kNm.

Explains why fork supports do not represent the crossing beams here: both principal beams can buckle in the same direction, so no horizontal restraint is provided. Defines a member rotational restraint instead, choosing the manual type because the stiffness is already known.

Enters the 348 kNm/rad discrete spring from the literature as a nodal support and reaches a fulfilled ratio of 97.5%. Then redoes the beam with the warping torsion approach: 359 kNm/rad hinge springs, seven degrees of freedom, an imperfection from the buckling mode, and the warping moment in the internal forces.