Research And Numerical Analysis On Impact Resistance Of Basalt Fiber And Polypropylene Fiber Reinforced Concrete

As an important protective structure in the city,civil air defense engineering is of great significance to improve the city security capability.Civil air defense engineering is mainly underground engineering.In addition to bearing static loads such as soil pressure,civil air defense engineering is mainly used to resist dynamic loads such as impact and explosion in wartime.At present,the main material for civil air defense engineering is concrete,which has the advantages of superior compressive performance,poor tensile performance and easy cracking,which affects the overall resistance of civil air defense engineering to a certain extent.Fiber Reinforced Concrete(FRC),as a new material emerging in recent years,is incorporated into the Concrete matrix by virtue of its excellent mechanical properties and plays a filling effect in the Concrete matrix,which significantly improves the tensile properties of Concrete and effectively inhibits the cracking of Concrete.Therefore,in order to improve the anti-impact and antiexplosion ability of civil air defense engineering,the research and application of fiber concrete in civil air defense engineering,and the study of static and dynamic impact load of fiber concrete have a promoting effect on the further development of civil air defense engineering.In this paper,based on the background of civil air defense engineering,Basalt Fiber(BF)and Polypropylene Fiber(PPF)were developed by experimental method.The mechanical properties of concrete(C40)for general civil air defense engineering and concrete(C60)for important civil air defense engineering in air defense basement of civil air defense engineering in urban construction under static and dynamic loads are studied.Ansys finite element method is used to simulate the pendulum of fiber reinforced concrete shear wall and plain concrete wall with different strength.The main research contents are as follows:(1)The service environment of civil air defense engineering in Qingdao was investigated.Qingdao is located on the Yellow Sea,are greatly affected by the Marine environment,in view of the chlorine ions in the Marine environment of Steel Fiber,Steel Fiber,SF)has strong corrosive,Therefore,basalt fiber and polypropylene fiber with good corrosion resistance are selected as reinforcing materials,and the appropriate fiber is selected for two kinds of concrete with different strength,so that the mechanical properties of concrete can be optimized.(2)The experimental study on mechanical properties of BFRC and PPFRC was carried out.The experimental results show that the mixing amount of BF and PPF has a great influence on the mechanical properties of C40 and C60 concrete.For C40 concrete,when the content of basalt fiber content is 0.1%(BFRC-0.1%),the compressive strength loss rate is 8.37%,and when PPFRC-0.3%,the compressive strength increases by 7.49%.The optimal content of splitting tensile strength is BFRC-0.1% or PPFRC-0.3%,and the optimal content of bending strength is BFRC-0.3% or PPFRC-0.5%.For C60 concrete,the compressive strength is the highest when BF and PPF content is 0.3%.The splitting tensile strength of BFRC-0.1% and PPFRC-0.3%improved most remarkably.When the two kinds of fiber content is 0.5,the flexural strength of C60 concrete increases the most.(3)The Hopkinson pressure bar device was used to conduct impact compression tests on BFRC and PPFRC specimens to determine the strain rate range of specimens under different impact pressures.The test results show that: The diameter of broken pieces of fiber reinforced concrete specimen is larger than that of plain concrete,and the content of 0.5% basalt fiber reinforced concrete is more suitable for replacing concrete(C40)in general civil air defense engineering in air defense basement to resist impact dynamic load.The polypropylene fiber concrete with the content of 0.5% is more suitable for replacing concrete(C60)in important civil air defense engineering in air defense basement to resist the impact dynamic load.(4)Finite element simulation of pendulum impact on fiber reinforced concrete shear wall and plain concrete wall is carried out by ANSYS/LS-DYNA software.C40 concrete wall mixed with 0.5% basalt fiber and C60 concrete wall mixed with 0.5%polypropylene fiber are selected.By comparing the damage diagram,impact force,impact energy and displacement with the plain concrete wall,the reliability of the fiber used as reinforcement material in actual civil air defense engineering is verified.