To build the bridges you have different kinds of materials. To start there are just your standard iron rebars, but as you level up you can unlock cables and steel girders. Combining all these elements is sure to yield perfect constructions.
Building a viable bridge for your trucks and buses isn't particularly hard, but that usually only gets you one star. To get each of the three stars available in each level you have to make optimum use of your resources, which is way harder than it sounds.
Bridge Construction Simulator is a highly entertaining puzzle game that boasts loads of levels and great graphics, to boot. You can also swap camera views when the trucks go over your bridge so you can see the action from lots of different perspectives.
Requires Android 4.1 or higher.