Regarding the emergency exit doors in the buidlings, does it require to be with a push bar or a normal door handle is sufficient?. Can someone please advise the design requirement for emergency exit door for building?

In England, for a non-dwelling, Building Regs Approved Document B volume 2 says "Doors should be readily openable to avoid undue delay to people escaping. " (para 5.6) and para 5.7 says:

"In general, doors on escape routes (whether or not the doors are fire doorsets) should be either of the following. a. Not fitted with a lock, latch or bolt fastenings. b. Fitted only with simple fastenings that are all of the following. i. Easy to operate; it should be apparent how to undo the fastening. ii. Operable from the side approached by people escaping. iii. Operable without a key. iv. Operable without requiring people to manipulate more than one mechanism. "Doors may be fitted with hardware to allow them to be locked when rooms are empty. "In places such as hotel bedrooms, locks may be fitted that are key operated from the outside and manually opened from the inside. "If a secure door is operated by code or combination keypad, swipe or proximity card, biometric data, etc., a security mechanism override should be possible from the side approached by people escaping."

So I read that as saying you don't have to have a crash bar, you could just have a handle, as long as it is easy to operate and obvious (and is the sole mechanism that needs operating, and no key, bolt, etc).  If it's obviously an ordinary door handle, I don't think it needs posted instructions.  In fact, if it needs posted instructions, I don't think it meets the requirements of the regs.

(I'm quoting from 2019 edition incorporating 2020 amendments).

User profile indicates they are probably asking about the UAE not UK