当主句与从句主语相同时，so that可以换成so as to do sth。如：

He studied hard so that he could go to college.

= He studied hard so as to go to college.

但如主句与从句主语不相同呢？so that可以换成so as for sb to do sth。如：

He worked hard so that his family could live a happy life.

可以换成下面这样吗？

He worked hard so as for his family to live a happy life.