A.16mm B.20mm C.25mm D.30mm
A.1/3~1/2 B.1/4~1/3 C.1/20~1/10 D.1/30~1/20
A.高聳鋼結(jié)構(gòu) B.板殼結(jié)構(gòu) C.輕型鋼結(jié)構(gòu) D.大跨結(jié)構(gòu)