In-plane Creep Buckling Analysis Of Concrete Filled Steel Tubular Archs

Arches with a concrete-filled steel tubular(CFST)cross-section are widely used in engineering structures,particularly in bridges,because of their light weight,high strength,convenience of construction using the steel tube as formwork,and their aesthetic appearance.However,when the concrete is subjected to sustained loading,the long-term performance of concrete decreased and the deformations continue to increase with time,i.e.the material creeps.However,there are few reports on the long-term stability of this kind of arch bridge.Therefore,the Beipanjiang River arch bridge with CFST with span of 445 m was taken as an engineering background.Then,the long-term stability performance is studied,and the relevant theoretical formulas of the circular arch of concrete filled steel tube are derived.The main research work in the thesis is as follows:1.The short-term and long-term stability of CFST arches at home and abroad were reviewed.The existing theoretical derivation methods of CFST columns and arches were discussed.The results show that Bazant and Sun Baojun's creep buckling formula of CFST column have good accuracy.At present,the theoretical derivation of creep buckling of CFST circular arches is mainly studied by foreign Pi team and scholars such as Jiang Wei and Wang Yuyin at home.The derivation of the related formulas of the parabola and catenary CFST arches is less.(Chapter1?2)2.Based on the energy method and age-adjusted effective modulus method,the long-term stability of critical force of CFST column indifferent boundary conditions considering creep was deduced.On the basis of the existing literature,the long-term stability of the circular arch under the radial load was deduced.The derived formula and the existing formula were compared and verified.The results show that the critical load of creep stability of CFST columns is related to the creep coefficient.As time goes on,the creep stability critical force of the three formulae of Jiang Wei,formula 1 and formula 2 decreases rapidly(0-100d),and the latter tends to be stable at the later stage.The formula 2 derived from this paper is consistent with the formula of Bazant,and the formula of creep stability critical force of the formula 1 is similar to the formula 2,and the difference is about 10%.After the critical force is stable,the difference between the critical force of the formula 1 and 2 with the Jiang Wei formula is about 8.5-23%.(Chapter3)3.A simplified calculation method of combination of age-adjusted effective modulus method and ANSYS was proposed and verified.The FEM model of arch rib of Beipanjiang River bridge arch is established,which was analyzed on the long-term stability in the simplified calculation method,and the effect of bearing capacity of creep buckling variation with time was studied.The results show that when the construction of the stiffening skeleton of CFST arch is 360 days,the stability coefficient with the effect of creep is reduced by 10% compared with no creep effect.The effect of creep of concrete on the stability bearing capacity of the structure is mainly in the early stage,and the influence of the later stage has decreased.(Chapter4)...