crack pattern in precast beam

[MikeE55]

I'm trying to figure out what has caused this crack pattern in a precast stadium beam. The cracks do not look like tension or shear cracks - maybe they are just shrinkage. The beam is about 3 feet deep and 14" wide. The predominant pattern is 3 or 4 longitudinal, with some random vertical cracks. The same pattern is on several of the grandstand beams, but always this same upper most span. The lower spans do not appear to be cracked. Any ideas?

 

[Ingenuity]

Corrosion, maybe? Looks like a lot of water staining that may warrant a closer look and tactile inspection.