Steel Buildings in Europe

Part 4: Detailed Design of Portal Frames 4 - 79 1 Shear centre of the shallowest cross-section 2 Axis where restraint is provided 3 Intermediate lateral restraints (purlins) 4 Lateral restraints to both flanges, providing torsional restraint 5 Compression flange Figure C.1 Arrangement of tension flange restraints C.3 N cr for uniform members with discrete restraints to the tension flange It is possible to take beneficial account of restraints to the tension flange. This may lead to a greater buckling resistance of the member. Tension flange restraint is usually provided by elements connected to the tension flange of the member (e.g. purlins). C.3.1 General expression For Class 1, 2, and 3 cross-sections, § 6.3.1.2 of EN 1993-1-1 gives cr y N Af   where 2 2 cr π L EI N  for flexural buckling 3 5 5 5 4 4 4 4 4 4 2 2 2 3 3 1 2 L L L s s s s s s a t t t