Question

Why do we make an assumption of the structural number (SN) and slab thickness (D) "first" when using traditional AASHTO Pavement Design method?

Answer 1

lwhile designing a paement, ldt of factors ae to be conadered and mot of thoie paraneters ae verų tedious to ftnd out For that Auork to be made eaier, some empecal velalion are gen I traditional AASHTO Pavement design vth ed shb thieknex ede asume structuwal umber CaN) and Fiysty, SN loa acually called a thicknes Index. st ii an absamber expretting the tuctral strenth of a pavement vequined -for qiven comlkindt -ions of soil support cng),total traffic expressed in ESAL. ,teminal erviceaiy and environment Jerviceabiltu and environment s a single nuhnber repverenting these facbrs, it pley' prominent t design, If this sN' is aumed r each load type , the calaulation become e tedious and later SN Canbe Converted to achual role. in pavemen กาเ thcknes uing a layer coeffraent that Teprelert, the veltive strength of the cnduction material, n that layer

structural number ựợiven where ai ะ ith layer coefficient D; - h layer thickneii Cin incher) Ym tb lauer drainage Coetfeient. Often, drainage cefAcert aunumedat 1 baued on the soil condthone. Layer coeffraent data. pre-avoilable rainaqe. e Coeffciern 淋 Yeaard to thickness, from the evolubonop parenent stiucure , it hat been Aunded that fom ascuminq thicknes hich neu of pavement U mortly vanging is the onl unknown in SN、 ae can calculate SN' uohich i futher uedin other emperi cal relations mentroned tn AAsHTo P method