Function Analysis Of Short-Round Bridge Pillar Under Axial Loading Reforced By Enlarging Section

In using process of the reinforced concrete bridge, because of continuously aging of the bridge structure with time developing, and continuously raising of traffic loading, which all put forward to request of strengthening original bridge structure, among them , the most needed- resolved problem is strengthening for the bridge pillars. It is a kind of extensive application and economy effectively method that adopting the enlargement of the section. Reinforced bridge pillar is a combination structure subjected to two stages loading,which consists two parts:before reinforced and after reinforced.This paper firstly analyses the whole process of loading.When strengthened,creep of concrete of strengthened columns tends to the stability,passion ratio tends to a stable value. Radial transform coefficient of wrapped parts of concretes outside is smaller, when the secondary loading functions on the strengthened bridge pillars, under equal lengthways strain, horizontal transform of original concrete is bigger than wrapped parts of concretes outside. The concrete of inner bridge pillar functions inflation loading outward on concrete of wrapped parts , Hence the wrapped parts of outside produce the passive binding loading toward to inner original bridge pillar, Just in calculation process of loading capacity of cut section of reinforced bridge pillar. The core concrete's strength should be calculated according to three to press/ press/ press , concrete of wrapped parts should be calculated according to three to pull/ press/ press. According to balanced loading and coordinate horizontal transform at combinary position of new and old concrete, iteratively calculated radial transform at combinary position of new and old concrete of strengthened pillar through program, thus calculating binding force of core concrete and wreath pull of wrapped concrete outside, According to loading process of reinforced bridge pillar , Draw up a piece of software(SBPES) to calculate loading of cross section of reinforced bridge pillar. The factors mainly including: thickness of wrapped part of concrete outside,strength of reinforced concrete,stress level index of the inner bridge pillar,the hoop rate of wrapped part of concrete outside and passion ratio which represents accumulated hurts of the concrete of original bridge pillar .Both augmenting thickness and strength of wrapped parts of concrete outside can enhance limit loading capacity of the strengthed bridge pillar.But the bigger thickness of wrapped part concrete outside leads to the decrease of clean space of infrastructure of bridge that can be used,the utilization of strengths of wrapping parts concrete outside also can't gets fuller exertion, so this thesis suggests not to adopt the bigger thickness of wrapped part outside and larger strength of reinforced concrete.Possibly uninstalling loading when original bridge pillar is reinforced,Decreasing initial strain margin between two parts concrete,when the strengthened bridge pillar subjects to secondary loading,two parts can work together better, the concrete of two parts can reach to extreme of loading capacity at the same time.When pillars strengthened,under the function of deadweight of upper structure,original old bridge pillar has some initial stress.Because of the creep of concrete, initial strain of concrete of old bridge pillar will decrease, initial strain margin between two parts concrete is smaller,so the influence is not obvious that stress level index of the original bridge pillar affects to limit loading capacity.Passion ratio affects limit loading capacity obviously,which represents accumulated hurts and horizontal transform capacity of theconcrete of original bridge pillar, which is in accordance with the result of theory analyse in Chapter two.Because the coefficient of horizontal transform of wrapped parts of concrete outside is smaller,causing radial transform not moderate between the concrete of the new part and the old part.Wrapped parts of concrete outside subjectes to wreaths pulling stess,the utilization of strengths of wrapping parts of concrete outside also can't gets fuller exertion. Wrapping parts of concrete outside also can't produce the valid restriction to the inner concrete.For producing valid restriction to the inner concrete and decreasing the pulling stress of wrapping parts of concrete outside, dense hoop method in wrapped part of concrete outside is suggested in this paper.By contrast, between dense hoop method and common hoop method in wrapped part of concrete outside ,detecting the certain degree exaltation both capacity of loading and ability of transform in the former,Comparing the results coming respectively from the software(SBPES) of this paper,The Norm of Reinforced,Method of ChangShu-Cheng and Method of San Qing-Su,the calculation result of the software(SBPES) of this paper is partial to small.Immediately based the basis principle of finite element method of reinforced concrete,this paper carries on the emulational imitation to reinforced bridge pillar by ANSYS(one of software of finite element method).Aimming at the property of secondary loading of reinforced bridge pillar,this paper uses method of"birth and kill elements",firstly killing elements of the wrapped parts of concrete outside,imitating the loading of original bridge pillar,at the secondary stage,when the two parts of reinforced bridge pillar is loaded together, activating elements of the wrapping parts of concrete outside.In the whole process,the property of reinforced bridge pillar subjected to two stages loading is imitated well.According to results of postprocess of ANSYS,this paper carries on better analysis of secondary loading of the reinforced bridge pillar ,the result is correct that the inner old concrete's stess should be calculated three to press/ press/ press , concrete of wrapped parts should be calculated three to pull/ press/ press.The results of ANSYS keeps in accordance with the theory analysis,and fits together with software(SBPES) results well.In the process of calculating loading capacity of cross section of reinforced bridge pillars,using the strength of axis anti- presses of the concrete of wrapped parts outside is not reasonable,the calculating results is bigger than actual loading capacity of reinforced bridge pillars.This text carries on the theory analysis of reinforced bridge pillars firstly,makes a piece of software(SBPES) for calculating carrying loads of cross section of reinforced bridge pillars,then changes each factors index,Plotting results coming from the software(SBPES),analyzing the influence of every factors to reinforced bridge pillar,then carries on emulational imitation to reinforced bridge pillar by finite element method, in whole process,the property of secondary loading of reinforced bridge pillar is imitated well.The results between finite element method and software(SBPES) meet well. This software(SBPES) is convenient and simple,it is expanded simply in strengthen of old bridge.The part of conclusion and outlook :if dense hoop in wrapped part,or tying up to round carbon fiber to reinforced bridge pillars or using tiny inflation concrete in wrapped part ,which can enhance limit loading capacity of reinforced bridge pillar.The result is influenced,when the creep of concrete of original bridge pillar is not considered,but the influence is tiny,which should be improved on in succedent emulational simulation.In future study,putting emphases on to property of reinforced bridge pillars functioned by variational loading.