There are two methods to make concrete beams in building structures. One is to make them on the ground first, and then hoist them with cranes for installation. This construction method is called "prefabrication"; The other is to support the formwork in the original position of the beam, reinforce the bar and pour it directly with concrete, which is called "cast-in-place". The concrete beam made by cast-in-place is called "cast-in-place beam".
in the drawing, the code name of the beam does not include the information of the construction method of prefabrication or cast-in-place. Then, "XL" means cantilever beam, which is a kind of beam, and refers to a beam with no support at one end and the other end pressed by the weight of the structure.