NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers - common casesNCCI: Effective lengths and destabilizing load parameters for beams and cantilevers - common cases SN009a-EN-EU NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers - common cases This NCCI presents values for the effective length parameter k and the destabilizing parameter D for beams and cantilevers with or without intermediate lateral restraints, for use with NCCI document SN002. Created on Thursday, May 30, 2013 This material is copyright - all rights reserved. Use of this document is subject to the terms and conditions of the Access Steel Licence Agreement Contents 1. General 2 2. Destabilizing load condition 2 3. Simple beams without intermediate restraint 2 4. Simple beams with intermediate lateral restraint 3 5. Cantilevers without intermediate restraints 4 6. Cantilevers with intermediate lateral restraints 4 Page 1 the mean value of k should be taken. rotational movements).1. If the restraint conditions at each end differ. the destabilizing parameter D should be taken as 1. Page 2 . Destabilizing load condition The destabilizing load condition should be taken into account where a load is applied to the top flange of a beam or cantilever. Use of this document is subject to the terms and conditions of the Access Steel Licence Agreement λz = is a parameter to allow for the effect of destabilising loads λz λ1 and λz L = kL in which iz for a beam is the distance between points of restraint to the compression flange for a cantilever is the length of the cantilever k is the effective length parameter dependant on the restraint conditions at the supports and expressions for the other parameters are given in SN002.common cases SN009a-EN-EU 1. 2. 2013 This material is copyright .NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers .0.all rights reserved. f y Mcr 1 C1 which.e. For the destabilizing load condition. 3. Simple beams without intermediate restraint The effective length parameter. may be obtained from Table 4. λ LT is given by: λ LT = λ LT = Wy. k for lateral-torsional buckling of a simple beam with restraints at the ends only. General The general expression for non-dimensional slenderness. may also be expressed as: UVDλ z βw Where D Created on Thursday.common cases NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers . May 30. and both the load and the flange are free to deflect laterally and relative to the shear centre of the cross section (i. as shown in SN002.2 otherwise D should be taken as 1. 0. 4.common cases NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers .0.8 Compression flange partially restrained against rotation on plan. for lateral torsional buckling of a simple beam with intermediate restraints should be taken as 1.2 otherwise D should be taken as 1.7 Compression flange fully restrained against rotation on plan. 0. 2013 This material is copyright . K Both flanges fully restrained against rotation on plan. account should be taken of the restraint conditions at the support. The effective length parameter k should be taken as the mean of the value given above and the value given by Table 4. k. the destabilizing parameter D should be taken as 1. 0.0 Page 3 .all rights reserved.0. k Conditions of restraint at supports Compression flange laterally restrained. Use of this document is subject to the terms and conditions of the Access Steel Licence Agreement For the segment between a support and the adjacent intermediate lateral restraint. 0. Nominal torsional restraint against rotation about longitudinal axis. Simple beams with intermediate lateral restraint The effective length parameter. May 30. 1.NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers . Table 4. Created on Thursday.1 for the restraint conditions at the support.common cases SN009a-EN-EU The conditions of restraint against rotation on plan of flanges at member supports should be assessed taking into account the stiffness of the connections as well as the stiffness of the supporting members or other construction supplying restraint at the supports.85 Both flanges free to rotate on plan.75 Both flanges partially restrained against rotation on plan. For the destabilizing load condition.1 Effective length parameter. unless the top flange also has intermediate restraints. Page 4 . Created on Thursday.0. and L should be taken as the length of the relevant segment between adjacent lateral restraints.3. May 30. whichever is the greater. For all other support conditions k and D should be obtained from Annex A and L should be taken as the length of the cantilever. lateral and torsional restraint at the support (the common case) and with no intermediate lateral restraint may be obtained from Table 6.all rights reserved.NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers .1 or Annex A should be increased by 30% or by 0. For the destabilizing load condition. If a bending moment is applied at its tip the effective length parameter k from Table 6. 2013 This material is copyright . Cantilevers without intermediate restraints The effective length parameter k for lateral-torsional buckling of a cantilever with moment continuity.1 and the load is not destabilising. Use of this document is subject to the terms and conditions of the Access Steel Licence Agreement 6. the effective length parameter k for lateral torsional buckling of a cantilever with intermediate restraints to its compression flange should be taken as 1.common cases SN009a-EN-EU 5.1. Cantilevers with intermediate lateral restraints Provided that the end restraint conditions correspond with Table 6. k and D should be obtained from Annex A and L should be taken as the length of the cantilever.common cases NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers . 7 1. May 30.9 4) Internal and torsional restraint 0.0 2.7 Examples of restraints to cantilever supports.8 3) Torsional restraint 0. at same level as continuous supporting beam Cantilever supported from flange of column Page 5 .common cases NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers .all rights reserved. Restraint to cantilever tips k D 1) Free 1. with effective restraint at the support. 2013 This material is copyright .common cases SN009a-EN-EU Created on Thursday. all providing effective moment continuity and lateral and torsional restraint Cantilevered beam continuous over supporting beam. Discontinuous cantilever.NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers . Use of this document is subject to the terms and conditions of the Access Steel Licence Agreement Table 6.9 2.8 1.1 Effective length parameter k and destabilizing parameter D for a cantilever without intermediate restraint.5 2) Lateral restraint to top flange 0. with lateral and torsional restraint. 8 2.7 1) Free 2) Lateral restraint to top flange 3) Torsional restraint 4) Lateral and torsional restraint 0. Use of this document is subject to the terms and conditions of the Access Steel Licence Agreement b) Continuous.common cases NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers .8 0.5 2.0 0.8 1. with partial torsional restraint 1.8 0.7 1) Free 2) Lateral restraint to top flange 3) Torsional restraint 4) Lateral and torsional restraint 1. for a range of restraints at the support.0 L Created on Thursday.9 1. Restraint conditions k D At support At tip a) Continuous.0 0.6 0.1 1.all rights reserved. 2013 This material is copyright .0 1.75 2.9 1. with lateral restraint to top flange 1) Free 2) Lateral restraint to top flange 3) Torsional restraint 4) Lateral and torsional restraint 3.5 2.NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers .0 2.8 2. May 30.5 2.4 L c) Continuous.7 1) Free 2) Lateral restraint to top flange 3) Torsional restraint 4) Lateral and torsional restraint 2.9 2.7 1.9 1.8 0.common cases SN009a-EN-EU Annex A: Effective length parameter k and destabilising D for cantilevers without intermediate restraint. torsionally and against rotation on plan L Tip restraint conditions 1) Free (not braced on plan) 2) Lateral restraint to top flange 3) Torsional restraint 4) Lateral and torsional restraint (braced on plan in at least one bay) (not braced on plan) (braced on plan in at least one bay) Page 6 .0 1.7 2. with lateral and torsional restraint L d) Restrained laterally.6 1.7 1.5 1.4 2. France A Bureau CTICM 17/8/05 3. Spain J Chica Labein 12/8/05 G W Owens SCI 25/4/06 Editorial content checked by Created on Thursday. UK G W Owens SCI 7/7/05 2. Germany C Muller RWTH 10/8/05 5.common cases Reference(s) ORIGINAL DOCUMENT Name Company Date Created by James Way The Steel Construction Institute 22/4/05 Technical content checked by Charles King The Steel Construction Institute 11/5/05 1. May 30.NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers .all rights reserved. Sweden A Olsson SBI 8/8/05 4. 2013 This material is copyright .common cases SN009a-EN-EU Quality Record RESOURCE TITLE NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers .common cases NCCI: Effective lengths and destabilizing load parameters for beams and cantilevers . Use of this document is subject to the terms and conditions of the Access Steel Licence Agreement Technical content endorsed by the following STEEL Partners: Resource approved by Technical Coordinator TRANSLATED DOCUMENT This Translation made and checked by: Translated resource approved by: Corrigendum 26/02/08 Reference to SN002 corrected Page 7 .
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