You have javascript disabled. This site uses javascript to enhance the functionality, please consider enabling it to get the best experience possible. Thank you.

  • Logo - SCI. Click to go to website
  • Logo - BCSA. Click to go to website
  • Logo - Tata Steel. Click to go to website

View NCCI for Chapter 5.3: Imperfections

Taken from BS EN 1993-1-1: 2005, Section 5: Structural analysis

Design of out of plane and transverse restraint systems for portal frames  (SN046)
Bracing is required to resist lateral loads, principally wind loads, and the destabilising effects of the imperfections defined in §5.3 of EN 1993-1-1. This bracing must be correctly positioned and have adequate strength and stiffness to justify the assumptions made in the analysis and member checks. It is essential to provide bracing that is both sufficiently strong and sufficiently stiff at all the points that are assumed to be restrained in the design calculations. This is especially true where the inner flange of the portal frame is in compression. Consequently, this document can only give general guidance, not detailed advice. The design criteria given in EN 1993-1-1 are summarised within this document.
Keywords:
5.3; 5.3.2; 5.3.3; portals
Valid until:
Jan 2015
Created by:
SCI
Created on:
Apr 2006
BSI Approval:
Not reviewed by BSI
Simplified approaches to the selection of equivalent horizontal forces for the global analysis of braced and unbraced frames  (SN047)
All structures contain imperfections and for steel structures EN 1993-1-1 §5.3 explicitly defines the allowances in structural analysis to cover their effects. The treatment of imperfections in EN1993-1-1 is very general, in order to be applicable to all forms of steel construction. This NCCI provides a simplified approach to these effects that focuses on the appropriate treatment of imperfections for low and medium-rise multi-storey buildings. It proposes horizontal force coefficients that are simple to apply and will be familiar to experienced users of previous national design standards.
Keywords:
sway; imperfections; frame stability; braced frames; 5.3; 5.3.1; 5.3.2; 5.3.3
Valid until:
Jan 2015
Created by:
SCI
Created on:
Jun 2006
BSI Approval:
Not reviewed by BSI