Seasonal effects on unbound materials

Two types of seasonal effects on unbound materials may be considered. One is a sinusoidal variation with time during the year given as:

E = Emean * (1 + ERange/2*sin(2p(Day – MaxDay)/365 + p/2))

where Emean is the modulus given in the structural data form,

 ERange is the relative range in modulus during the year,

 Day is the day number counted from the start of the year, and

 MaxDay is the day with maximum modulus.

The values are stored in the table “Moisture factors”.

The other variation is for thawing of a material. If a material has been frozen and then thaws, the modulus is multiplied by a factor, R:

R = 1 - (1 - Ro) * exp(A * days since frost)

where Ro is the maximum frost reduction, and

 A is the recovery rate.

These values are also stored in the table “Moisture factors”.