Study On Control Technology And Limitation Of Verticality For Super High Piers

With the development of highway in mountainous area, the prestressed concretecontinuous rigid frame bridges have become the main form of the structure acrossvalley and river. By the limits of the topography and geology conditions, the piers ofprestressed concrete continuous rigid frame bridges become more and more high, andeven many continuous rigid frame bridges with more than meters high piers have beenappeared. Verticality of large-span bridges with high piers, not only affects the stabilityof high piers, but also becomes an important index of the bridges construction level.The universal calculated formulas and the limitation for verticality of piers are notgiven in the current specification. Although the finite element method can be used tocalculate the bearing capacity and verticality of the high piers more accurately, it haslow computational efficiency and weak applicability. This paper base on the theory ofelastic stability, and has carried out the following research work:①During construction period, in the influence of construction error andtemperature difference and wind load and construction load, piers of bridge willemerge various defects which can affect the pier verticality. In the influence of defects,piers will be in eccentric loading condition, and the stability of piers will be greatlyreduced. The effect of initial geometrical imperfection and multiple loads areconsidered at the same time. First, the two defects’ influence law for bridge verticalityis analyzed, through the theoretical derivation considering the geometry nonlinear;then, the stability and bearing capacity influence of piers with different defects isanalyzed, through the finite element calculation considering the geometricalnonlinearity and the material nonlinear at the same time.②The constant section piers of continuous rigid frame bridges on the cantileverphase are taken as object, the effect of geometrical initial imperfection and multipleloads for high piers geometric nonlinear stability are considered at the same time. Thedisplacement of pier top and the bending moment of pier bottom under complexoperating condition are solved, through two methods of establishing elastic stabilitydifferential equation and second-order analysis.③The variable section piers of continuous rigid frame bridges on the cantilever construction stage are taken as object, the effect of geometrical initial imperfection andconstruction loads for high piers geometric nonlinear stability are considered. Basingon the Rayleigh-Ritz method of energy approach, calculated formulas for thedisplacement of pier top and the displacement amplification factor are derived.④Combining the investigated content, models are established by the software ofANSYS, which are directed against piers of related projects and compared with thesolution of formulas. On the basis of theory analysis results, further research for theverticality limitation of high and super high piers is done.⑤Super high piers will give the construction of continuous rigid frame a lot ofproblems. This paper has compared with different construction plans and verticalitycontrol methods, and gives parts of verticality control suggestions for high piers andsuper high piers.