I have catalogs filled with single, double and triple head pendants of all shapes size and description. Non of them are designed or approved for outdoor or wet location installations. I assume that the structure has no ceiling... it is open to the sky above and you want to hang these pendants from the beam structure? If there is a ceiling that has a roof deck on it to shed the rain etc, then we are talking a different game and you can make use of the stock pendants. Photos would really help us solve this for you.