Research On PCN Value Analysis Method Of Rigid Pavement Based On Residual Strength

The Pavement Classification Number?PCN?value of the pavement is an important parameter for the bearing performance of the airport pavement.International Civil Aviation Organization?ICAO?mandates that member states can use their own methods to analyze this value.The current calculation methods including the equivalent single wheel load method,the critical aircraft method based on the wheel load conversion,and the critical aircraft method based on CDF?Cumulative Damage Factor?conversion all have different results.And even for the same method,the calculation results will have a difference of up to 3 times due to different parameter values.In order to study the reasonable method of PCN value analysis and solve its uniqueness problem,the main research contents and achievements of this paper are as follows:1.The finite element software is used to simulate 41 types of models,17 types of relative stiffness radius,considering two critical load positions parallel and vertical to the edge of the panel.The response of the pavement structure under 1394 conditions is calculated.The database is established and programmed with Matlab software to realize the program of aircraft load stress of each model under different road conditions.2.Based on the theoretical analysis and the collected fatigue test data of cement concrete,a new non-linear analysis model of residual flexural strength for airport concrete pavement is proposed.First,based on the residual strength theory,the residual flexural strength formula used in airport pavement in China is analyzed,which does not meet the objective law of the residual strength attenuation of concrete,residual strength decays too quickly,and underestimates the carrying capacity of the pavement.It is the main reason for the low PCN value of the current rigid pavement;Second,based on the theory of material residual strength and the collected fatigue test data of cement concrete,a nonlinear calculation model of residual flexural tensile strength of pavement cement concrete is proposed:f_rm=f_cm(1-0.37457×S^26.3296×n)^0.03798The average error between the experimental value and the theoretical value is just 1.7%;Third,the method of high-low loading and equal damage ratio conversion is proposed to calculate the residual strength under multi-stage aircraft load,and the calculation formula is clarified.Finally,by a given example demonstrates the feasibility of the formula for calculating the residual strength of concrete in airport pavement.3.Based on the basic principle of ACN-PCN method,and the analysis of the existing problems of the two major types of PCN calculation methods,combining the advantages of the two types of methods,combined with the new model for calculating the residual strength of airport pavement,a PCN evaluation method based on residual strength calculation is proposed.The original equivalent single wheel load method is improved,and the value of the original residual flexural strength in the formula is optimized,which not only solves the uniqueness of the PCN value of the pavement,but also solves the shortcoming of the low PCN result of the traditional evaluation method.A PCN value calculation program for airport rigid pavement is compiled using Matlab platform.A comparative analysis of the 4C/4D/4E airport pavement examples show that the PCN evaluation method proposed in this paper can increase the PCN value by 20%?40%compared with the traditional evaluation method.