^pof;
Civil;
and;
Transportation;
Engineering,;
South;
China;
University;
of;
Technology,;
Guangzhou;
510640,;
China;
^pof;
Civil;
and;
Environmental;
Engineering,;
Virginia;
Polytechnic;
Institute;
and;
State;
University,;
Blacksburg;
24060,;
USA;