Function of 开了 in 我开车开了半天了

Question

I am currently studying Basic Mandarin Chinese by Cornelius C. Kubler and encountered the following sentence in Unit 8 Part 4:

我开车开了半天了，我们换个人开，行不行？

Without 开了 the first part of sentence makes sense to me - the person tells that he/she drove car for a long time. However, the function of 开了 is unclear. Does it describe the duration of driving 半天 or the action 开车 itself? Or maybe it is redundant but helps sentence sound more natural? Is there a kind of construction verb+object+verb+了 and if so, what are the other use cases?

Answer 1

grammar topic:complements of duration with object, raised at this site several times (still searching locations),anyhow here is an excerpt from Yufa! A Practical Guide to Mandarin Chinese Grammar 13 The complement of duration

(b) The verb-repetition pattern

The verb-repetition pattern is: verb + object + verb + complement. When the verb has an object, the verb must be repeated before the complement of duration appears.昨天他跳舞跳了一个晚上，所以今天早上起得很晚。 He danced all night last night, so he got up late this morning. 张：王老师教书教了多长时间了？ Zhang: How long has Teacher Wang been teaching? 李：他教了快十五年了。Li: He has been teaching for almost 15 years

Answer 2

1. Basic SVO form: "我开车" (I drive) = [我(s)+ 开(v) + 车(o)] or [我(s)+开车(v)]

2. Add description of the duration : [我开(半天)车] = [I drive (half a day)]

3. Add verb particle '了' to indicate the verb is completed : [我开(了)半天车] = [I (have driven) half a day]

4. repeat the verb 'drive' to emphasize it : [(我)(开车)(开)(半天)] = [(I) (drive), (drive) (half a day)]

5. Add verb particle '了' to indicate the verb is completed: [我开车开(了)半天] = [I drive, (have driven) half a day]

6. Add particle '了' at the end to indicate the duration has been completed : [我开车开了半天(了)] = [I drive, have driven half a day (already)]

Is there a kind of construction verb+object+verb+了 and if so, what are the other use cases?

Yes:

The following Examples' structure are the same as above

游泳--> 游一小時泳--> 游了一小時泳--> 游泳游了一小時--> 游泳游了一小時了

打工--> 打一天工--> 打了一天工--> 打工打了一天--> 打工打了一天了

吃飯--> 吃飯十分鐘--> 吃了十分鐘飯--> 吃飯吃了十分鐘--> 吃飯吃了十分鐘了