Strength and Stiffness Characteristics of Steel Ladder-Type Cable Traysby W. Johnson, Bechtel Power Corp, Ann Arbor, MI, USA,
P. Shunmugavel, Bechtel Power Corp, Ann Arbor, MI, USA,
J. Chien, Bechtel Power Corp, Ann Arbor, MI, USA,
Abstract: Ladder-type cable trays identical with the as-built are generally tested to establish their strength and stiffness characteristics. Test data for systems in operating plants, however, may be either nonexistent, incomplete, not directly applicable to the as-built configuration, or cannot be acquired through additional testing due to discontinuation of the as-built hardware. In these instances, derivation of the stiffness and strength characteristics using an analysis can provide time and cost savings. Most test lateral load-deformation curves exhibit small deviations from the corresponding initial tangent modulus curves over the load range for which the component is designed. Accordingly, linear Vierendeel truss models are applicable to their stiffness determination. The shear lag dependence of siderail stiffness values for the truss model are investigated in detail using finite element solutions. Equations are developed representing the Vierendeel truss as an equivalent shear-flexure beam to arrive at a theoretical load-deformation expression dependent on the system parameters. These results are compared with test data to verify the model.
Subject Headings: Cables | Stiffening | Field tests | Curvature | Trusses | Power plants | Load tests | Lateral loads
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