Research On The Frost Resistance Durability Of Assembled Concrete Bridge Piers Based On ABAQUS Secondary Development

Fabricated bridge structures have now become an important part of promoting the development of new industrialized industries.However,in cold areas in northern my country,bridge structure damage caused by freeze-thaw cycles frequently occurs.Therefore,it is particularly important to study the impact of freeze-thaw cycles on the durability of bridge structures.This research is often carried out by experimental methods.In order to reduce the high cost and time-consuming problems caused by the experimental method,this paper uses the ABAQUS finite element simulation method for research.The main research results are as follows:Starting from the freeze-thaw mechanism of concrete and the factors affecting concrete freeze-thaw,the principle of the damage caused by the freeze-thaw cycle to prefabricated concrete piers is explained,and the important significance of concrete frost resistance and durability in the cold regions of northern my country is explained.Use ABAQUS finite element software to model the fabricated concrete piers,set 50 times,100 times,150 times,200 times of heat conduction analysis and thermal stress coupling analysis,set the ambient temperature to 20℃,and set the temperature cycle interval It is-20℃~20℃.Through software simulation,the temperature change curve diagram under different cycles,the temperature cloud diagram of a cycle,and the temperature change curve diagram at different positions of the bridge pier model are obtained.The results show that the temperature transfer is from the outside to the inside,which is in line with the reality;after many cycles,different temperature cycle curves will be formed at different positions inside and outside the component,that is,the temperature extreme at the center of the component is the lowest and gradually increases outward;At the same time,the temperature difference between the inside and outside of the pier cap,the pier column and the cap is 34.2℃,30.2℃,and 36 ℃ respectively,that is,the larger the component size,the larger the temperature difference between the inside and outside of the component.Through the thermal stress coupling analysis to extract the temperature stress curve,it can be seen that the influence of temperature on the outer surface of the component is greater than the influence on the center point of the component,and the temperature stress change at the center point of the component lags behind the outer surface,which is consistent with the temperature change curve.It is found by comparison that the larger the size of the component,the smaller the temperature stress at the center point of the component,indicating that the temperature effect only has a serious impact on the specimen within a certain size range,which is also one of the reasons for the severe peeling of the outer skin of the specimen.Because the software defaults to import the temperature as the node temperature instead of the integration point temperature,but the damage calculation requires the node temperature to be assigned to the integration point.This article uses the UFIELD subroutine written in the Fortran language to assign the node temperature to the integration point;In the freeze-thaw cycle damage simulation,the damage amount of multiple cycles is the same as the result of a single cycle,so it is not possible to superimpose the damage calculation.In this paper,the USDFLD subroutine is written in the Fortran language to calculate the total damage amount of the freeze-thaw cycle.After 50,100,150,and 200 freeze-thaw cycles are performed on the model,a 5mm displacement is applied to the y direction and a 0.1MP stress is applied to the z direction.The equivalent plastic strain value can be obtained from the equivalent plastic strain cloud diagram obtained after loading.Respectively 2.518e-3,2.533e-3,2.538e-3,2.563e-3,a value greater than zero indicates that plastic strain has occurred at this time.It can be seen from the displacement cloud that the maximum total displacement is 5.506 mm,5.516 mm,5.521 mm,5.539 mm,and the displacement components in the x,y,and z directions also gradually increase.As a result,as the number of freeze-thaw cycles increases,the damage to the piers becomes more and more serious and the performance gradually decreases.The analysis shows that the bridge pier node is the weak part of the bridge pier structure,and reasonable construction and maintenance suggestions are put forward for this phenomenon.