Software Development And Application Of Asphalt Pavement Structural Reliability Based On The Multi-index Controls

According to the current?Specification for Design of Highway Asphalt Pavement??JTG D50-2107?,the structural design of asphalt pavement calculated with multiple control indexes is based on the reliability theory.However,there isn't still set of structural reliability calculation method to analyze the reliability of asphalt pavement structure based on the control indicators mentioned above,and the reference literature has few.Hence,this subject is studied.In view of different pavement structure types matching different control indexes,it is necessary to select different control indexes according to different pavement structure types to calculate the reliability of pavement structure.In the article,the type with"asphalt surface layer+inorganic binder layer"was studied,a functional function was established with the inorganic binder stability layer fatigue crack check index for asphalt pavement reliability calculation and sensitivity analysis,the corresponding computer program was written,and the program visual software interface was developed.Firstly,the asphalt pavement structure reliability calculation method,which the fatigue cracking check of the sublayer of inorganic binder layer was taken as design control index,was established,the corresponding structural reliability calculation functions Z_awas given,then based on the Monte Carlo method,Matlab software was used to compile the structural reliability program and sensitivity analysis program and software interface design and development.In the reliability calculation,traffic parameters,geometric parameters,material parameters and environmental parameters were selected as random variables.Traffic parameters include directional coefficient DDF,lane coefficient LDF,annual average growth rate?of traffic volume,as well as two-way annual average daily traffic volume AADTT of 2-axle vehicles with 6 or more wheels.The geometric parameters include surface thickness ha,base thickness hb and subbase thickness h_bb.The material parameters include surface layer modulus?E_a?,base layer modulus?E_b?,subbase layer modulus(E_bb)and soil base modulus?E₀?,as well as the flexural tensile strength?Rs?of inorganic binder stabilized material layers.Environmental parameters include annual mean temperature?Ta and monthly mean temperature annual range Ta.mon.Secondly,the GUI interface design module of Matlab software was used to develop the object-oriented program interface,which has many functions from the interface,such as controlling the operation of the program and the collecting of calculation results and other functions.The software for calculating the general reliability of asphalt pavement developed in this paper can set up a maximum of 10 layers structure,among which the surface layer port can be set up to 4 layers,the base layer port can be set up to 3 layers?including 1 subbase?,and the functional layer port can be set up to 2 layers,there has total 10 layers including the soil base.Therefore,the software program developed in this paper can be used to calculate and analyze the pavement structure reliability and sensitivity based on above asphalt pavement structure type within 10 layers.The reliability calculation program developed in this paper has the following functions:?1?Constant value calculation can be realized,such as the calculation of equivalent axial load EALF_m,the calculation of the cumulative effect times of equivalent design axial load N_efixed value,the conversion of equivalent layer thickness and its modulus,the calculation of temperature adjustment coefficient and equivalent temperature,and the fatigue cracking life N_f2of the stable layer of inorganic binder,and so on.?2?The reliability of the stable layer of inorganic binder with fatigue cracking as the design index can be calculated.?3?Sensitivity analysis includes the structural reliability to variation coefficient of random parameters and to mean value of random parameters.Finally,the program software developed in this paper was used to analyze and calculate a practical example,the result verifies the feasibility of the software and the correctness of the calculation result.The order of the influence degree of the variation coefficient and mean value of above four parameters on the structural reliability of asphalt pavement is found.