COMPUTING AND USING EFFECTIVE LENGTH IN PORTAL FRAME DESIGN

An exact procedure for analysis including the nonlinear effects of axial forces in members is developed. It is extended to allow computation of the elastic critical load factor, lambda, to be applied to any load set to cause instability using an algorithm readily incorporated in standard computer programs. Lambda is used to determine the correct effective length for each member in the frame. The procedures are used to compare the correct amplification of bending moment with that specified in the beam - column capacity formula of design codes. It is found that bending moments arising out of loads not inducing sway are not amplified by the factor 1/(1 - omega/lambda) used in the design formula, where omega is the load factor. Bending moments associated with sway forces are amplified. For many practical cases the design formula is unduly conservative, and an alternative formula is proposed. (Author/TRRL)

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/14454467
• Corporate Authors:

  Monash University

  Wellington Road
  Clayton, Victoria  Australia  3800
• Authors:
  • Grundy, P
• Publication Date: 1980

Media Info

• Features: Figures; References;
• Pagination: 17 p.
• Serial:
  • Publication of: Monash University, Australia
  • Publisher: Monash University
  • ISSN: 1445-4467

Subject/Index Terms

• TRT Terms: Algorithms; Axial loads; Beams; Bridges; Columns; Computer programs; Elasticity (Mechanics); Frames; Length; Loads; Mathematical analysis; Nonlinear systems; Structural design
• Uncontrolled Terms: Nonlinearity
• Old TRIS Terms: Portal structures
• ITRD Terms: 6471: Analysis (math); 3472: Beam; 3434: Bridge pier; 5912: Elasticity; 6488: Length; 5567: Load; 6482: Non linear system; 3468: Portal frame bridge
• Subject Areas: Bridges and other structures; Design; Highways; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00329692
• Record Type: Publication
• Source Agency: ARRB
• Report/Paper Numbers: Rpt. No. 4
• Files: ITRD, TRIS, ATRI
• Created Date: Oct 28 1981 12:00AM