Analysis and design of cable-stayed steel columns using the stiffness probe method

German Gurfinkel, Sudarshan Krishnan

Research output: Contribution to specialist publicationArticle

Abstract

The stiffness probe method (SPM) is a new numerical procedure that calculates buckling loads. SPM probes the local stiffness of a given structure at the point of application of a small transverse perturbation force as the applied load is increased. The local stiffness degrades from a maximum for an unloaded structure to zero at the buckling load. An artifice spring is added to the original structure that eventually absorbs the full perturbation force at a prescribed small deflection, thereby keeping structural deformations small as the buckling load is approached. As a result, using an indicator that approaches zero at buckling rather than having to rely on increasingly larger deflections at buckling as in conventional P-Δ methods, SPM ensures an accurate numerical result for the critical load. We use SPM herein to study the behavior of one and two cross-arm cable-stayed columns under applied load. A formula is given to calculate the minimum slenderness that justifies converting a tube into a cable-stayed column. Various factors such as cable prestrain, cable cross-sectional areas, and tiers of cross-arms affecting column strength are examined for a series of cable-stayed columns. We find that cable-stayed columns may buckle either in a one-lobe symmetrical mode or two-lobe anti-symmetrical mode, the latter case being contrary to conventional thinking. A design example for a given cable-stayed column using the AISC Specification is presented. The effect of optimum cable prestrain to enhance column buckling strengths is discussed. A strength enhancement ratio (SER) is defined that evaluates the additional column strength gained after transforming a given steel tube into a cable-stayed column.

Original languageEnglish (US)
Pages195-210
Number of pages16
Volume54
No3
Specialist publicationEngineering Journal
StatePublished - Jan 1 2017

Fingerprint

Cables
Stiffness
Buckling
Steel
Loads (forces)
Specifications

Keywords

  • Analysis
  • Behavior
  • Buckling modes
  • Cable (slackening, stays, optimum prestraining)
  • Columns
  • Cross-arms
  • Design (ASD, LRFD)
  • Eigenvectors
  • Elastic stability
  • Failure mode
  • Load (applied, external)
  • Numerical methods
  • Residual tension
  • Spring (augmented, parallel, series)
  • Steel
  • Stiffness probe
  • Strength (enhancement, nominal)

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction

Cite this

Analysis and design of cable-stayed steel columns using the stiffness probe method. / Gurfinkel, German; Krishnan, Sudarshan.

In: Engineering Journal, Vol. 54, No. 3, 01.01.2017, p. 195-210.

Research output: Contribution to specialist publicationArticle

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AB - The stiffness probe method (SPM) is a new numerical procedure that calculates buckling loads. SPM probes the local stiffness of a given structure at the point of application of a small transverse perturbation force as the applied load is increased. The local stiffness degrades from a maximum for an unloaded structure to zero at the buckling load. An artifice spring is added to the original structure that eventually absorbs the full perturbation force at a prescribed small deflection, thereby keeping structural deformations small as the buckling load is approached. As a result, using an indicator that approaches zero at buckling rather than having to rely on increasingly larger deflections at buckling as in conventional P-Δ methods, SPM ensures an accurate numerical result for the critical load. We use SPM herein to study the behavior of one and two cross-arm cable-stayed columns under applied load. A formula is given to calculate the minimum slenderness that justifies converting a tube into a cable-stayed column. Various factors such as cable prestrain, cable cross-sectional areas, and tiers of cross-arms affecting column strength are examined for a series of cable-stayed columns. We find that cable-stayed columns may buckle either in a one-lobe symmetrical mode or two-lobe anti-symmetrical mode, the latter case being contrary to conventional thinking. A design example for a given cable-stayed column using the AISC Specification is presented. The effect of optimum cable prestrain to enhance column buckling strengths is discussed. A strength enhancement ratio (SER) is defined that evaluates the additional column strength gained after transforming a given steel tube into a cable-stayed column.

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