The bicycle industry has to build bikes for a variety of riders of a variety of weights, riding styles, etc. Standard production bikes have to be able to withstand a certain weight or rider and gear in order to prevent problems with people suing when their 110 carbon frame breaks under their weight, etc. There are not a whole lot of numbers out there but I would feel it would be safe to assume that a bike itself should be able to support a rider up to about 300# on a normal frame. The amount of weight it can theoretically support says nothing though on how the bike will actually ride, frame and wheel flex.

Have you ever noticed that big frames (over 60 cm, like my 63 cm) are at an extreme nearly 1 pound heavier than smaller frames. That is because after a certain size more material needs to be placed in the tubes (thicker walled) to prevent flexing, cracking, etc for the rider that rides such a big bike (like me 6'6", 225 pounds). I have riden nothing more than a 24 spoke wheel and have had no problems even with potholes, etc. Now most of the reason for this is my technique, i.e. getting off the saddle before impacts of the sort.

Some parts though like Ti pedals, certain carbon wheels, etc have strick weight limits. In the effort to make the parts lighter the tubing of the part must get thinner and for some parts like pedals the material way crack or fail above certain forces. For example speedplay Ti pedals are rated at no more than I believe 180 pounds. Just like with PSI and rims, you can excede that value but it according to the manufacturer may not be safe. You will never see me riding a Ti speedplay pedal system.

To get a true bike designed for a riders weight or style custom is the only way to go. You can get tube sizes, frame sizes, etc that are designed for your weight.

Your bike is not going to fall apart, unless it is built incorrectly. I have put 2k hard miles on my road bike this season with no problems and I would not consider myself a lite rider.