Cracks in new house concrete foundation
It's hard to say if it's a structural problem without more information.  The crack in the photo is not necessarily a structural problem.  Most likely it's related to less than ideal subgrade, concrete mix, control joint spacing, or concrete curing conditions.  Concrete is always going to crack.  That crack is excessive, but most likely not a structural concern.  If you notice something translating up the structure -- cracks in the walls, or sloping floors -- then it would be a greater concern.