well, i didn't look into dictionary, but i think i can make a conclusion. 上originally means 'upward', and in this case, it is a tendency where a result(mostly positive, like being enrolled, promoted or getting into a new house) is achieved. It is suffixed in its adverb form. With this meaning it carries a sentimental mood, and is usually pronounced in neutral tone or liaison. On interpreting, you may regard it as 'be able to'. On saying tendency, this is because 得 means achieving when percepted as a verb, especially in classical Chinese. Whereas there are also 买得起、买得到、行得通、弄得出来、吃得下

表示有了结果或达到目的. 《现代汉语词典》的解释： shàng 用在动词后。 ①表示由低处向高处：爬～山顶。 ②表示有了结果或达到目的：锁～门│考～了大学│那时他家穷得连饭都吃不～。 ③表示开始并继续：爱～了农村。

1.考上大学 is a phrase, so 考得上大学 means being admitted to a university. 2.当上经理 上means taking office. So 当上+position means taking the job of some position. 3.住上新房 is also a phrase. living in a new house.

“上”用在动词后面，表示“趋向”、“完成”的意思，跟英语的“up”用法相像，比如“锁上”--lock up、关上--close up，表示一种状态。