History of Strength of Materials [antikvár]

IntroductionFrom the earliest times when people started to build, it was found necessary to have information regarding the strength of structural materials so that rules for determining safe dimensions of members could be drawn up. No doubt the Egyptians had some empirical rules of this kind, for without them it would have been impossible to erect their great monuments, temples, pyramids, and obelisks, some of which still exist. The Greeks further advanced the art of building. They developed statics, which underlies the mechanics of materials. Archimedes (287-212 b.c.) gave a rigorous proof of the conditions of equilibrium of a lever and outlined methods of determining centers of gravity of bodies. He used his theory in the construction of various hoisting devices. The methods used by the Greeks in transporting the columns and architraves of the temple of Diana of Ephesus are shown in Figs. 1 to 3.The Romans were great builders. Not only some of their monuments and temples remain, but also roads, bridges, and fortifications. We know something of their building methods from the book by Vitruvius,' a famous Roman architect and engineer of the time of Emperor Augustus. In this book, their structural materials and types of construction are described. Figure 4 shows a type of hoist used by the Romans for lifting heavy stones. The Romans often used arches in their buildings. Figure 5 shows the arches in the famous Pont du Gard, a bridge which is in service to this day in southern France. A comparison^ of the proportions of Roman arches with those of the present time indicates that nowadays much lighter structures are built. The Romans had not the advantages provided by stress analysis. They did not know how to select the proper shape and usually took semicircular arches of comparatively small span.Most of the knowledge that the Greeks and Romans accumulated in the way of structural engineering was lost during the Middle Ages and only since the Renaissance has it been recovered. Thus when the famous Italian architect Fontana (1543-1607) erected the Vatican obelisk at the order of Pope Sixtus V, (Fig. 6), this work attracted wide attention from^ Vitruvius, "Architecture," French translation by De Bioul, Brussels, 1816.' For such a comparison, see Alfred Leger, "Les Travaux Publics aux temps dea Romains," p. 135, Paris, 1875,1