Nonlinear shape analysis for constructional multiwire cable structures with clamps considering multi-stiffness properties

Abstract

Multiwire cable structures equipped with clamps are widely used in civil engineering, such as suspension bridges, and their bending stiffness is always neglected in design. However, in practice, bending can be important locally when the sudden changes of cable curvature occur due to hanger forces loaded group by group during construction. Moreover, the main cable, composed of high-strength steel wires, has a secondary sectional bending stiffness that changes and with its tension state, being small (flexible) at the first stages and increasing gradually until reaching a notable rigidity (stiff). This, along with the effect of clamps leads to a Flexible-Stiff Coupling Multi-stiffnesses (FSCM) properties with geometrical and mechanical nonlinearities. Ignoring this might introduce uncontrollable shape errors during installation. To fill the gap of a shape analysis considering the FSCM, an analytical method as Chord Substitution Method (CSM) is proposed. The chord line geometry of the structure is taken as an independent object, and then the system equilibrium can be represented with a set of chain pole equations based on an established physic model of cable segment. The extension of each chord rod is modeled with a composite-chord-spring considering both axial and bending geometric stiffnesses. The cable curvature effect at clamps can be modeled by correcting external forces to satisfy a bending compatibility condition. The effectiveness of the CSM is validated by a previous model test found in the literature, and a real example is used for comparative studies. This method might be promising for a refined construction design and monitoring control of such structures.