Learn Farsi: لطفاً ساختمان را به دلیل هشدار تخلیه کنید. - Please evacuate the building because of the warning.

They are connected by the invisible ezafe vowel, making it sound like be dalil-e hoshdâr. The phrase be dalil-e translates to "because of" or literally "for the reason of." Whenever you use it before a noun like hoshdâr (warning), you must add that -e sound.

Could I use be khâter-e instead of be dalil-e here?

Yes, absolutely! be khâter-e hoshdâr also means "because of the warning." Both are very common. be dalil-e can sometimes sound slightly more formal or official, which perfectly matches an instruction to evacuate a building.

Why is the word râ directly after sâkhtmân (building)?

râ marks the specific direct object of the sentence. Since you are being told to evacuate a specific building ("the building"), sâkhtmân gets the râ marker. Notice that râ attaches directly to the object it marks, coming before the "because of" phrase.

How does the verb takhliye konid work here?

This is a compound verb, takhliye kardan (to empty / to evacuate). Here it is in the imperative (command) form for "you" (plural or formal): konid (do). So it literally means "do an evacuation."