Kelio istorija. Tiltų statybos raida nuo arkų iki santvarų

Abstract

The bridge was' built by Bernabe Visconti in 1377 and was destroyed in 1416. The Chinese had used iron for making suspension bridge chains and for ties between voussoirs in their masonry arches. The idea of using iron in bridge building slowly percolated to the West and was used in England early in the eighteen century. As in many other cases, the theory of arch action lagged behind, rather than led, construction practice. The Romans developed simple empirical relationships that permitted the depth to be determined once the span was known. The relation- " ships were retained through the Dark Ages, "built into secret books of the Masonic lodges". In about 1500 Leonardo da Vinci looked at the failure modes of arches and at different shapes and came close to producing a correct analysis of arch behavior. He also correctly recognized that the key to the continued functioning of the arch lay in its foundations. After some two millennia of arch construction, the theoretical analysis of the structural behavior of arch bridges began in 1675 with the work of Robert Hooke, who saw the reciprocal analogy between the arch and the loaded cable-Simple timber beams could span up to 7 m or 10 m with the addition of a little technology and 20 m if larger tree trunks could be maneuvered into place. To cross greater distances, it was necessary to either use additional piers or develop a more effective structural form. An alternative structural form to the arch and the beam is the truss, which uses the geometric rigidity of the triangle to produce a manufactured member by greatly enhancing the bending and buckling strength available from given amount of material.