Out-of-Plane Stability And Design Of Steel Arches

Until recently, the out-of-plane stability theory and strength design of steelarch are not well established and not available for practical use. In this paper,the out-of-plane stability behavior and ultimate load-carrying capacity of steelcircular arches are studied systematically, and practical design methods forout-of-plane ultimate strength and bracing stiffness are presented.Firstly, the out-of-plane elastic stability of circular arches is studied. Bycreating the general equilibrium equations of spatial infinitesimal, thetheoretical solutions and practical concise ones for elastic flexural-torsionalbuckling loads under uniform compression, uniform bending and unequal endmoments are obtained respectively. With FE method the stability behaviors ofarches subjected to combined axial force and bending moment are fullyinvestigated.Secondly, by large deflection elasto-plastic FEM, the out-of-planeload-carrying capacity of circular arches under uniform compression anduniform bending is investigated respectively. With the normalized archslenderness introduced to unify different rise-to-span ratios and boundaryconditions, the stability curves for arches with hot-rolled pipe section, weldedbox section and welded I section are obtained. Next, for bending archessubjected to unequal end moments, methods of equivalent normalizedslenderness and moment modification factors are created to predict the ultimatestrength.Thirdly, the out-of-plane elasto-plastic stability performance and failuremechanism of circular arches subjected to combined axial force and bendingmoment are presented. Subsequently an inner-force-based universal designformula for ultimate load-carrying capacity is established, which is suitable forcomplex load conditions, as well as the design of arch segments in out-of-planebraced arches.Fourthly, for the elastic stability of out-of-plane braced circular arches,theoretic solutions for buckling loads of continuously braced pinned arches under uniform compression and uniform bending are obtained. For discretelybraced arches, FEA is employed to reveal the characteristic of elastic stability.Then the elastic threshold values of bracing stiffness for fully restraint areacquired for equally-spaced lateral-translational braces, as well as therequirement of brace spacing when out-of-plane elastic buckling is prevented.Finally, for elasto-plastic stability of out-of-plane braced circular arches,the efficiency and influence of discrete braces are investigated. Theelasto-plastic threshold stiffness of equally-spaced lateral-translational bracesare obtained for fully restraint, meanwhile design suggestion for arch segmentsbetween bracing point are proposed.