浅谈桥梁工程发展史

浅谈桥梁工程发展史内容摘要：

ast construction . The transition from wooden bridges to steel types probably did not begin until about 1840 ,although the first documented use of iron in bridges was the chain bridge built in 1734 across the Oder River in Prussia . The first truss pletely made of iron was in 1840 in the United States , followed by England in 1845 , Germany in 1853 , and Russia in 1857 . In 1840 , the first iron arch truss bridge was built across the Erie Canal at Utica . The Impetus of Analysis The theory of structures The theory of structures ,developed mainly in the niheenth century,focused on truss analysis, with the first book on bridges written in 1811. The Warren triangular truss was introduced in 1846 , supplemented by a method for calculating the correcet forces .Ibeams fabricated from plates became popular in England and were used in shortspan bridges. In 1866, Culmann explained the principles of cantilever truss bridges, and one year later the first cantilever bridge was built across the Main River in Hassfurt, Germany, with a center span of 425 feet (130m) . The first cantilever bridge in the United States was built in 1875 across the Kentucky most impressive railway cantilever bridge in the nieenth century was the First of Forth bridge , built between 1883 and 1893 , with span magnitudes of 1711 feet (). At about the same time , structural steel was introduced as a prime material in bridge work , although its quality was often poor . Several early examples are the Eads bridge in。 the Brooklyn bridge in New York。 and the Glasgow bridge in Missouri , all pleted between 1874 and 1883. Among the analytical and design progress to be mentioned are the contributions of Maxwell , particularly for certain statically indeterminate trusses。 the books by Cremona (1872) on graphical statics。 the force method redefined by Mohr。 and the works by Clapeyron who introduced the threemoment equations. The Impetus of New Materials Since the beginning of the twentieth century , concrete has taken its place as one of the most useful and important structural materials . Because of the coMParative ease with which it can be molded into any desired shape , its structural uses are almost unlimited . Wherever Portland cement and suitable aggregates are available , it can replace other materials for certain types of structures, such as bridge substructure and foundation elements . In addition , the introduction of reinforced concrete in multispan frames at the beginning of this century imposed new analytical requirements . Structures of a high order of redundancy could not be analyzed with the classical methods of the nieenth century .The importance of joint rotation was already demonstrated by Manderla (1880) and Bendixen (1914) , who developed relationships between joint moments and angular rotations from which the unknown moments can be obtained ,the so called slopedeflection method .More simplifications in frame analysis were made possible by the work of Calisev (1923) , who used successive approximations to reduce the system of equations to one simple expression for each iteration step . This approach was further refined and integrated by Cross (1930) in what is known as the method of moment distribution . One of the most import important recent developments in the area of analytical procedures is the extension of design to cover the elasticplastic range , also known as load factor or ultimate design. Plastic analysis was introduced with some practical observations by Tresca (1846)。 and was。