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View NCCI for Chapter 5.2: Global analysis

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

Calculation of αcr  (SN004)
This NCCI sets out the basis for the calculation of αcr, the parameter that measures the stability of the frame.
Keywords:
frame stability; second-order effects; sway effects; imperfections; 5.2.1; 5.2.2
Valid until:
Feb 2015
Created by:
SCI
Created on:
Feb 2006
BSI Approval:
Not reviewed by BSI
Design of roof trusses  (SN027)
The traditional analysis of a truss assumes that all loads are applied in the joints and that all joints in the truss are pinned. Even though this is generally not the case, since the upper and lower chords are normally continuous and the web members are often welded to the chords, it is still a common and acceptable procedure to determine the axial forces in the members. In a situation when the dimensions of the upper chord is very large and the overall depth of the truss is small the moments due to continuous upper chord has to be considered. However, this is rarely the case for roof trusses in industrial buildings that is treated here. Bending moments have to be considered in other cases, which will be explained here.
Keywords:
trusses
Valid until:
Jan 2015
Created by:
SCI
Created on:
May 2006
BSI Approval:
Not reviewed by BSI
Practical analytical models for portal frames (plastic analysis)  (SN039)
Portal frames verified by plastic design are commonly fabricated from hot-rolled I sections. It is generally most economic to have haunches to deepen the rafters at the columns as shown in Figure 1.1 below. It is essential that the section classification is Class 1 at all plastic hinge positions and so it is most common to use Class 1 sections throughout the columns and rafters. It is common to use Class 3 webs and Class 1 flanges for the haunches, provided that in the Class 3 portion of the web either the stress distribution remains elastic or the requirements of EN 1993-1-1 §6.2.2.4 are satisfied and no plastic hinge occurs.
Keywords:
haunch; portal design; 5.2.1; 5.2.2
Valid until:
Jan 2015
Created by:
SCI
Created on:
Mar 2006
BSI Approval:
Not reviewed by BSI
Simple methods for second order effects in portal frames  (SN033)
Second-order effects occur due to sway of the frame. The sway causes eccentricity of vertical loading that generates second-order moments in the columns. The effects of the deformed geometry (second-order effects) shall be considered if they increase the action effects significantly or modify significantly the structural behaviour, see EN 1993-1-1, section 5.2.
Valid until:
Jan 2015
Created by:
SCI
Created on:
Mar 2006
BSI Approval:
Not reviewed by BSI