Restraint of Column/Segment from adjacent ones, as applied in Lift Structural Elements.

Even though in Columns or Beams used in the assembly of Lift Car Frames & Horizontal Structural Members;
When Force(s) are distributed in internal Members and Pin Joints assumptions are made allowances for rotation end restraint is appropriate. Thus the contradiction of the Structure [When Apparent] and using compression members effective lengths that are less than their actual lengths and by using Stability Theory of the Elastic Response the effective length of the critical segments are reduced. For each case in terms of simple Braced Frames with pinned beam-to-column connections are capable of transfering Limited Moments these points are considered explicitly in B.S. 5950 Part 1 for Frames and Trusses.

Regarding Compression Members in rigid-jointed Frames the effective length is directly related to the restaints within the contained / surrounding Members.

For Beams rigidly connected to Columns can when Overloaded lead to significant Plasticity either at a Beam or at either Column prevents the restraints being transferred to the Columns.

The Design of some/or/two Struts require the following additional points; 1) Built-up sections or Compound Struts behave in separate ways 2) Angles, Channels and Tees which are Eccentric loaded can produce more secure Connections 3) Compound Members whose overall slenderness are such that the Axial Resistance are added . 4) Thus in the Design approaches described of BS 5950 Part 1 are set Conditions which when met permit the Compound Members to be designed as Integral Members. 5) Quantitative rules for the determination of the overall slenderness limits the value of the applied Forces. 6). BS 5400: Part 3 contain specific rules for the design of Struts connected by cover plates and Struts consisting of back-to-back components.

John Irwin C Eng M I Mech E --- 22 Princess Court, Queensway, London W2 4RB.