【正文】 rmanent and transient . Permanent loads Dead Load : this includes the weight DC of all bridge ponents , appurtenances and utilities, wearing surface DW and future overlays , and earth fill EV. Both AASHTO and LRFD specifications give tables summarizing the unit weights of materials monly used in bridge work . Transient Loads Vehicular Live Load (LL) Vehicle loading for shortspan bridges :considerable effort has been made in the United States and Canada to develop a live load model that can represent the highway loading more realistically than the H or the HS AASHTO models . The current AASHTO model is still the applicable loading. 橋梁工程和橋梁美學(xué) 橋梁工程的發(fā)展概況 早在公元前 1世紀(jì)， Marcus Vitrucios Pollio 的著作中就有關(guān)于建筑材料和結(jié)構(gòu)類型的記載和評(píng)述。 the force method redefined by Mohr。 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 。 外文文獻(xiàn)翻譯 BRIDGE ENGINEERING AND AESTHETICS Evolvement of bridge Engineering,brief review Among the early documented reviews of construction materials and structure types are the books of Marcus Vitruvios Pollio in the first century basic principles of statics were developed by the Greeks , and were exemplified in works and applications by Leonardo da Vinci,Cardeno,and the fifteenth and sixteenth century, engineers seemed to be unaware of this record , and relied solely on experience and tradition for building bridges and aqueducts .The state of the art changed rapidly toward the end of the seventeenth century when Leibnitz, Newton, and Bernoulli introduced mathematical formulations. Published works by Lahire (1695)and Belidor (1792) about the theoretical analysis of structures provided the basis in the field of mechanics of materials . Kuzmanovic(1977) focuses on stone and wood as the first bridgebuilding materials. Iron was introduced during the transitional period from wood to steel .According to recent records , concrete was used in France as early as 1840 for a bridge 39 feet (12 m) long to span the Garoyne Canal at Grisoles, but reinforced concrete was not introduced in bridge construction until the beginning of this century . Prestressed concrete was first used in 1927. Stone bridges of the arch type (integrated superstructure and substructure) were constructed in Rome and other European cities in the middle ages . These arches were halfcircular , with flat arches beginning to dominate bridge work during the Renaissance period. This concept was markedly improved at the end of the eighteenth century and found structurally adequate to acmodate future railroad loads . In terms of analysis and use of materials , stone bridges have not changed much ,but the theoretical treatment was improved by introducing the pressureline concept in the early 1670s(Lahire, 1695) . The arch theory was documented in model tests where typical failure modes were considered (Frezier,1739).Culmann(1851) introduced the elastic center method for fixedend arches, and showed that three redundant parameters can be found by the use of three equations of coMPatibility. Wooden trusses were used in bridges during the sixteenth century when Palladio built triangular frames for bridge spans 10 feet long . This effort also focused on the three basic principles og bridge design : convenience(serviceability) ,appearance , and endurance(strength) . several timber truss bridges were constructed in western Europe beginning in the 1750s with spans up to 200 feet (61m) supported on stone substructures .Significant progress was possible in the United States and Russia during the nieenth century ,prompted by the need to cross major rivers and by an abundance of suitable timber . Favorable economic considerations included initial low cost and fast 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,foc