In-plane Stability Analysis Of Three-center Truss-arch

Arched dimensional truss structure is a new type of structure rising in recentyears, which has been widely used in the convention and exhibition centers, largestadiums, airport terminals, industry plants, etc. Dimensional truss can be made intoarbitrary curve forms, such as arch, parabola, catenary. Sectional form could beequilateral triangle, inverted triangle, trapezoid. The specific sectional form can bedetermined according to the conditions of use. Three-center truss-arch is a new formof large-span arched dimensional truss structure, it consists of three truss-arches, that’s,two side arches and one middle arch, one end of the side arch is perpendicular to theground, and the center of the side arch is on the radius of the middle arch. This formof structure is now mainly used in large stadiums. Instability damaging is one of theimportant reasons causing steel structures collapse. Large-span arched dimensionaltruss structure is mainly used in major public buildings, overall or local instability willbe a serious threat to people’s lives and properties safety. With more widespreadapplication of the three-center truss-arch, it is necessary to study the structurestability.This paper firstly analyzes the distribution pattern of internal forces of thethree-center solid-web arch, then studies the buckling mode and the buckling loadvariation of the three-center truss-arch. Then it analyzes relationships among thesecond-order elastic stability bearing capacity of the three-center truss-arch, sectionequivalent inertia moment and the span, thus the formula of structure second-orderelastic stability bearing capacity is obtained, and the second-order elastic overallstability factor K is introduced in the formula, then analysis of shape parameters andcross-sectional parameters influence on the overall stability coefficient K is conducted,and the expression of the overall stability coefficient K is obtained by fittingaccording to the analysis data. Lastly elastoplastic stability analysis on thethree-center truss-arch is conducted. The process of the structure overall and localinstability damaging is studied by using the sectional plastic hinge concept based onthe calculation results of the finite element program ANSYS, and the instabilityfailure mechanism is summed up.Study shows that: The buckling load variation of the three-center truss-arch isopposite to the internal forces variation of the three-center solid-web arch. The impact of section width-depth ratio b/h and angle θ between the upper chord member and theweb member in the panel on the structure overall stability coefficient K is very smalland can be ignored, the web member and upper chord member section area ratio A4/A1has limited effect on the structure overall stability factor K, so it’s not wise to increasethe ultimate bearing capacity by increasing web member section size, depth-span ratioi, rise-span ratio n and middle arch angle α is the main factor to affect the structureoverall stability coefficient K. Elastoplastic instability failure of the three-center truss-arch began with the sectional plastic hinge successive formation at some adversesection. Increasing the chord member section size or the sectional height of theadverse section will be able to reduce the chord member section stress, delaying theformation of the sectional plastic hinge. Thus the structure will postpone entering thestage of instability failure, and the stability bearing capacity of the three-centertruss-arch will be enhanced.