The designer superimposed his aesthetic concepts onto the traditional architectural style.

superimposed 是动词 superimpose 的过去式。superimpose 由前缀 super-（表示"在...之上"）和动词 impose（强加、施加）组成，字面意思是"在原有事物之上施加新事物"，即"叠加、重叠"的意思。