单项选择题
A.垫板长度不小于3跨,厚度不小于50mm B.垫板长度不小于2跨,厚度不小于50mm C.垫板长度不小于2跨,厚度不小于30mm D.垫板长度不小于3跨,厚度不小于30mm
A.不应小于4跨,且不应小于6m B.不应小于3跨,且不应小于4.5m C.不应小于3跨,且不应小于5m D.不应大于4跨,且不应大于6m
A.300mm B.350mm C.400mm D.450mm