Abstract :
When we were kids, the puzzle page of the Sunday papers had a drawing containing, say, 20 erroneous or impossible items. In a reasonable length of time most of us could find all 20, and maybe even one or two more that the artist hadn´t intended. Those puzzles came vividly to mind the other day when the newspapers ran a drawing of the support technique for the collapsed bridge in Mianus, Conn. Wouldn´t any intelligent 12-year-old experienced enough to take his bicycle apart and reassemble it have found ¿what´s wrong with this picture¿ in a matter of seconds? Large sections of the bridge (100 by 40 feet) were ¿hung¿ by four shear pins, one at each corner of the section. Several investigating teams were assigned to determine the cause of the bridge failure. Meanwhile, some of us who used to work those Sunday puzzles are ready to blame poor design. And we won´t even invoke an equation to prove our case. We just looked at the mechanical drawing and said it was naive design. Though the official jury is still out, there are hints that we may be right. For example, bridge engineers are now saying that the design is ¿obsolete.¿ Yet the bridge is only 25 years old. (There are 60 more like it still in use in Connecticut alone.) Did the designers of this bridge ever hear of redundancy? The designers may have optimized ease of construction at the expense of reliability.
