桥梁工程的发展概况-毕业论文外文文献翻译.docx

装订线毕业设计报告外文翻译Evolvement of bridge Engineering,brief reviewAmong the early documented reviews of construction materials and structure types are the books of Marcus Vitruvios Pollio in the first century B.C.The basic principles of statics were developed by the Greeks , and were exemplified in works and applications by Leonardo da Vinci,Cardeno,and Galileo.In 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 bridge-building 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 half-circular , 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 accommodate 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 pressure-line 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 fixed-end 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 nineteenth 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 completely 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 ninetheenth 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 .I-beams fabricated from plates became popular in England and were used in short-span 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 River.A most impressive railway cantilever bridge in the nineteenth century was the First of Forth bridge , built between 1883 and 1893 , with span magnitudes of 1711 feet (521.5m).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 St.Louis ; the Brooklyn bridge in New York ; and the Glasgow bridge in Missouri , all completed 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 three-moment equations.The Impetus of New MaterialsSince 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 nineteenth 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 slope-deflection 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 elastic-plastic range , also known as load factor or ultimate design. Plastic analysis was introduced with some practical observations by Tresca (1846) ; and was formulated by Saint-Venant (1870) , The concept of plasticity attracted researchers and engineers after World War , mainly in Germany , with the center of activity shifting to England and the United States after World War .The probabilistic approach is a new design concept that is expected to replace the classical deterministic methodology.A main step forward was the 1969 addition of the Federal Highway Adiministration (FHWA)”Criteria for Reinforced Concrete Bridge Members “ that covers strength and serviceability at ultimate design . This was prepared for use in conjunction with the 1969 American Association of State Highway Offficials (AASHO) Standard Specification, and was presented in a format that is readily adaptable to the development of ultimate design specifications .According to this document , the proportioning of reinforced concrete members ( including columns ) may be limited by various stages of behavior : elastic , cracked , and ultimate . Design axial loads , or design shears . Structural capacity is the reaction phase , and all calculated modified strength values derived from theoretical strengths are the capacity values , such as moment capacity ,axial load capacity ,or shear capacity .At serviceability states , investigations may also be necessary for deflections , maximum crack width , and fatigue .Bridge Types A notable bridge type is the suspension bridge , with the first example built in the United States in 1796. Problems of dynamic stability were investigated after the Tacoma bridge collapse , and this work led to significant theoretical contributions Steinman ( 1929 ) summarizes about 250 suspension bridges built throughout the world between 1741 and 1928 .With the introduction of the interstate system and the need to provide structures at grade separations , certain bridge types have taken a strong place in bridge practice. These include concrete superstructures (slab ,T-beams,concrete box girders ), steel beam and plate girders , steel box girders , composite construction , orthotropic plates , segmental construction , curved girders ,and cable-stayed bridges . Prefabricated members are given serious consideration , while interest in box sections remains strong .LOADS AND LOADING GROUPSThe loads to be considered in the design of substructures and bridge foundations include loads and forces transmitted from the superstructure, and those acting directly on the substructure and foundation .AASHTO loads . Section 3 of AASHTO specifications summarizes the loads and forces to be considered in the design of bridges (superstructure and substructure ) . Briefly , these are dead load ,live load , iMPact or dynamic effect of live load , wind load , and other forces such as longitudinal forces , centrifugal force ,thermal forces , earth pressure , buoyancy , shrinkage and long term creep , rib shortening , erection stresses , ice and current pressure , collision force , and earthquake stresses .Besides these conventional loads that are generally quantified , AASHTO also recognizes indirect load effects such as friction at expansion bearings and stresses associated with differential settlement of bridge components .The LRFD specifications divide loads into two distinct categories : permanent and transient .Permanent loads Dead Load : this includes the weight DC of all bridge components , 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 commonly used in bridge work .Transient Loads Vehicular Live Load (LL) Vehicle loading for short-span 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.Size Effects and the Dynamic Response of Plain ConcreteIn the last couple of decades, there have been numerous reports Baant 1984; Carpinteri and Chiaia 1997; Karihaloo 1999; Jenq and Shah 1985 about the specimen size effects in quasi-brittle materials. For these materials, Baant states that the source of the size effect is a mismatch between the size dependence of the energy release rate and the rate of energy consumed by fractureBaant 2000 . Whereas a significant portion of the former in- creases as the square of the specimen size, the latter increases linearly. Thus, the reduction in the nominal stress is seen as a means of compensating for this variance by reducing the energy release rate of the specimen.Unlike with quasi-static loading, the study of specimen size effects in the dynamic domain has not received much attention. Such attempts are confined largely to fiber-reinforced polymers Morton 1998; Qian et al. 1990; Liu et al. 1998; Han 1998 . The data with respect to cement-based materials is extremely scarceBaant and Gettu 1992; Oh and Chung 1988; Krauthammer et al.2003; Elfahal et al. 2004; Banthia and Bindiganavile 2002 and attention towards impact rates is very recent. A lack of design codes or even a standard method for laboratory testing hinders our ability to characterize building materials for constructing impact and blast resistant facilities. Moreover, impact testing in- troduces several extraneous influences such as the inertia Banthia et al. 1987 and test machine effects Banthia and Bindiganavile2002 . Perhaps the most serious impediment is the inherent stress- rate sensitivity of cement-based composites. Morton states that it is not possible to produce an exact scale model for rate-sensitive materials Morton 1998 . Further, the suitability of known scaling models under dynamic rates is still under scrutiny. In this context, a special emphasis must be assigned to explaining the issues of scaling for cement-based materials under high stress rates.In this paper, the size effect on the impact response of concrete is presented through an assessment of recently published data by the writers and others. Familiar scaling laws developed for quasi- static loading are examined in the context of dynamic stress rates. This paper discusses the interplay between the specimen size, matrix strength, stress rate sensitivity, and loading configuration.Scaling Laws for Quasi-Brittle SystemsIt is well known that the quasi-static response of plain concrete is affected by the size of the specimen. Evidence gathered over decades reveals a strong dependence on size for structural con- crete behavior under compression Sabnis and Mirza 1979 , ten- sion Baant et al. 1991; van Mier and van Vliet 2002 , flexureWright 1952; Baant and Li 1995; Jueshi and Hui 1997 , shear Baant and Sun 1987 , and torsion Zhou et al. 1998 . Three approaches dominate the study of size effects in quasi-brittle ma- terials Baant and Chen 1997 :1.The statistical theory of random strength;2.The theory of stress redistribution and fracture energy release caused by large cracks; and3.The theory of crack fractality.Baants Size Effect Law Baant 1984According to Baant, the size effect in solids is a smooth transi- tion from the strength criterion of plasticity applicable to small size specimens to the crack size dependence of linear elastic fracture mechanics LEFM as seen in much larger specimens . The failure stress of a series of geometrically similar specimens of concrete is described by the following infinite series:Multifractal Scaling Law Carpinteri and Chiaia 1997Carpinteri and his associates used the concept of self-similar morphologies with noninteger dimensions called fractals to de- scribe the microstructure of quasi-brittle materials such as con- crete. With an increase in the scale of observation, the topological fractality is thought to vanish. As the microstructure of a hetero- geneous material remains the same regardless of size, they pro- posed that the influence of macroscopic size on the mechanical properties was a result of the interaction between the dimension b and a characteristic length lch for the specimen. On the basis of this hypothesis, the following multifractal scaling law MFSL was proposed:where f t = asymptotic value of the nominal strength u at infinite sizes. As opposed to BSEL, MFSL appears to suit unnotched specimens, as they