句子的意思是在建造房屋和桥梁上最常见的受压构件类型是圆柱,一个垂直构件,它的主要的功能就是支持垂直荷载。主语:type,谓语:is,宾语:the coium。 定语: of compression member occurring in buildings and bridges 修饰type,the most common也是修饰type,后面的是一个定语从句,主语是a vertical member, 定语是 whose primary function ,谓语是 is ,宾语是 to support vertical loads。