TEN PRINCIPLES The following ten principles are taken from Abeles (Ref. 2.32) and applicable not only to prestressing concrete but to any endeavor that the engineer is called upon to undertake: 1. You cannot have everything. (Each solution has advantages and disadvantages that have to be tallied and traded off against each other.) 2. You cannot have something for nothing. (One has to pay in one way or another for something which is offered as a "free gift" into the bargain, notwithstanding a solu- tion's being optimal for the problem.) 3. It is never too late (e.g., to alter a design, to strengthen a structure before it col- lapses, or to adjust or even change principles previously employed in the light of in- creased knowledge and experience). 4. There is no progress without considered risk. (While it is important to ensure suffi- cient safety, overconservatism can never lead to an understanding of novel struc- tures.) 5. The proof of the pudding is in the eating. (This is in direct connection with the pre- vious principle indicating the necessity of tests.) 6. Simplicity is always an advantage, but beware of oversimplification. (The latter may lead to theoretical calculations which are not always correct in practice, or to a fail- ure to cover all conditions.) 7. Do not generalize, but rather qualify the specific circumstances. (Serious misunder- standings may be caused by unreserved generalizations.) 8. The important question is how good, not how cheap an item is. (A cheap price given by an inexperienced contractor usually results in bad work; similarly, cheap, unproved appliances may have to be replaced.) 9. We live and learn. (It is always possible to increase one's knowledge and experi- ence.) 10. There is nothing completely new. (Nothing is achieved instantaneously, but only by step-by-step development.) Choose one principle and explain it in relation to prestressed concrete design.