Monitoring Test Of Arch-beam Combination System During Steeve Tension Period Of Changchun Light Rail Third Period Project

The construction of arch bridges has a long history in our country,Zhao Zhou bridge in He Bei province built in 606 BC is the most typical representative one among arch bridges.Because of its economy and beauty,arch bridges are usually used.In recent years,with the development and completion of design technology and construction methods,and the use of new type construction material and construction methods,traditional arch bridges start to develop to large span bridges,and at the same time some new type bridges appear. Arch-beam combination system steeve arch bridges are the most typical representative one among arch bridges. Concrete filled steel tube is usually used as steel rib in arch-beam combination system steeve arch bridges.It's because concrete filled steel tube has the advantages of light weight,high stiffness,high anti-deformation capacity.and it can solve many problems such as needing a little material,light weight when being setted,simple construction and high weight capacity.Therefore, concrete filled steel tube is one kind ideal material of large span arch bridges.What's more,confinement effect of steel pipe on canal concrete can give full play to mechanical properties of canal concrete material,and improve weight capacity of arch rib.Although arch-beam combination system steeve arch bridges are widely used,but its theoretical research is relatively backward.Until now,it's still lack of design and construction code of this bridge type in our country.At present,the design and construction of this bridge type mainly depand on experience.Because the characteristics such as slenderness ratio,curved bars,compression bending,alternating moment is far different from the characteristics of building under stress.Therefore,the mechanical characteristics of arch-beam combination system steeve arch bridges can not be compelely taken into consideration by this mean.While steeve stretching is the key of this bridge type.Its reasonable design and correct construction are the key to bridge quality and safety.The design method at present of arch-beam combination system steeve arch bridges is not perfect.On today of building lots of arch-beam combination system steeve arch bridges,it is needed to do research on steeve cable force design and optimization theory.Meanwhile,because of the great influnce of steeve cable force difference on mechanical charicteristics of the whole bridge,it is of great significance of steeve tension construction quality to safety and usage of arch-beam combination system steeve arch bridges.But in existing research results,monitoring technology of steeve stretching construction is relatively backward,and can not meet the demand of the bridge development.Therefore, construction monitoring technology of steeve arch bridges needs to be further improved.In a word,in order to make sure the construction safety and quality of arch-beam combination system steeve arch bridges,more advanced methods are needed to monitor and control bridge construction.Main work in this paper is according to construction monitor of prestressed concrete arch-beam combination system steeve arch bridges of Chang Chun rapid rail transit light rail the third period project (southern section of No.4 line)double line 22+25+22m during steeve stretching adjustment period.Finite element analysis model is established,firstly.Basis on finite element analysis model,construction order of steeve stretching is calculated by trial method,and each period is theoretically analyzed.Monitoring scheme during stretching adjustment period is setted up,and monitoring methods of each mechanical factor are cleared.Real time monitor is carried out,and monitoring results are compared with calculation results and analyzed.Main research work in this paper is as follows:1.Finite element models of arch rib,steeve and main beam are established,respectively.So finite element analysis models are formed.Based on finite element analysis models,construction order of steeve stretching is determined by using trial method,and theoretical analysis is carried out in each stage.It can make sure the structure safety of the steeve stretching during adjustment phase,and the consistency of completion state and design results.2.Based on theoretical analysis,the monitoring process during the construction period of steeve stretching adjustment is settet out,firstly.Mechanical characteristics of arch-beam combination system are deeply analyzed.And the monitoring content,measuring point layout location and monitoring methods are determined.The real time monitor is carried out to measure steeve stretching by using advanced vibration test technology.Based on understanding measuring theory of each monitoring equipment, apparatus which is needed of monitoring mechanical factors is selected.3.Triple control standard which mainly consists of vibration test of steeve force and supplemented with deformation of main members and stress increment is used this time.And steeve stretching and adjustment of cable force are monitored during the construction period.The stress of main forced members during periods of steeve stretching and cable force adjustment equal to theoretical calculation results,and meet corresponding codes.Displacement increment of main forced members during each period equal to theoretical calculation results.It's known from the monitoring results of stress and displacement increment,the monitoring scheme is reasonable and effective.The test value of steeve cable force during the completed bridge period equals to that provided in design decument.The maxium relative error is less than 2.5%.It can make sure that adjustment scheme of steeve cable force is reasonable,monitoring methods are scientific and effective.