外文翻译-高层建筑结构的发展

广西科技大学土木建筑工程学院 2013 届本科毕业设计外文翻译题目高层建筑结构的发展专 业 班 级 姓 名 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译2学 号 指导教师及职称2013 年 3 月Development of Structural Forms For Tall BuildingsThe first steps towards the modern multistory building appear to have been taken in the Bronge Age, with the appearance of the emergence of proper cities. Even today there appears to be an instrinc relationship between the tall building, and the city. Multistory buildings were considered a characteristic of ancient Rome, and four and five-story wooden tenement buildings were common. Those built after the great fire of Nero used the new burnt brick and concrete materials in the form of arch and barrel vault structures, which replaced the earlier post and lintel construction.Throughout the following centuries, the two basic materials used in building construction were timber and masonry, although the former lacked the strength required for buildings of more than about 16m in height, and always presented a fire hazard. The latter had the advantages of high compressive strength and fire resistance, but suffered from its high weight, which tended to overload the lower supports. The limits of this form of construction became apparent in 1891 in the 16-story Monadnock Building in Chicago which required the lower walls to be over 2m thick, and was the last tall building in the city for which load-bearing masonry walls were employed. The socio-econormic problems which followed the industrialization of the 19th century, allied to the insatiable demand for space in the US cities, gave a big impetus to tall building construction. However, the growth could not have been 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译3sustained without two major technical innovations during the middle of that century, namely, the development of new higher strength and structurally more efficient materials, wrought iron and subsequently steel, and the introduction of the elevator to facilitate vertical transportation. The new material allowed the development of lightweight framed or skeletal structures, permitting greater heights and more and larger openings in the building. The forerunner of the steel frame which appeared in Chicago around 1890 may well have been a seven-story iron-framed Manchester cotton mill, built in 1801,in which the contemporary I-beam shape appears to have been used for the first time. The Crystal Palace, built for the London International Exhibition of 1851, used a completely autonomous iron frame, with columns of cast iron and beams of cast or wrought iron. One of the notable features of this design was the large-scale approach towards mass-production techniques to facilitate fabrication and erection.Although the first elevator appeared in 1851, in a New York hotel, its potential in high-rise building was apparently not realized until its incorporation in the Equitable Life Insurance Company Building in New York in 1870. For the first time, this made the upper stories as attractive a renting proposition as the lower ones, and in so doing made the taller-than-average structure financially viable.Improved steel design methods and construction techniques allowed steel-framed structure to grow steadily upwards, although progress slowed down during the period of the First World War. In 1909, the 50-story Metropolitan Tower Building. This golden age of American skyscraper construction culminated in 1931 in its crowning glory, the Empire State Building. Its 102 stories rose to a height of 381m which has now increased to 449m with the addition of a TV aerial. The building used 57000t (US) of structural steel, nearly 53500m of concrete, and was designed and built in the record time of 17 months.Although reinforced concrete construction began to be adopted seriously 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译4around the turn of the century, it dose not appear to have been used properly for multistory buildings until after the end of the First World War. The inherent advantages of the composite material were not at that time fully appreciated, and the early systems were developed purely as imitations of steel structures. An early landmark was the 16-story Ingalls Building in Cincinnatti, Ohio, (1903), which was not superseded until 1915 when the 19-story Medical Arts Building in Dallas was hailed as the words tallest reinforced concrete building. Thereafter, progress was slow and intermittent, and when the Empire State Building was completed, the Exchange Building in Seattle had attained a height of only 23 stories.The economic depression of the 1930s put an end to the great skyscraper era, and it was not until some years after the end of the Second World War that the construction of high-rise building recommend, bringing with it new structural and architectural solution. However, modern developments have produced new structural layouts, improved material qualities, and better design and construction techniques rather than significant increases in height.Design philosophies altered during the period of recession and war. The earlier tall buildings were characterized by having heavy structural elements and being very stiff due to the high in-plane rigidities of the interior partitions and faade cladding with low areas of fenestrastion. However, modern office blocks tend to be characterized by light demountable partitions to aloe planning flexibility of occupancy, exterior glass curtain walls, and lighter sections as a result of high-strength concrete and steel material, whilst non-load-bearing infills have give way to load-bearing walls which simultaneously divide and enclose space. As a result, much of the hidden reserve of the earlier buildings has disappeared, and the basic structure must now provide both the required strength and stiffness against vertical and lateral loads. Consequently, the last there decades have seen major changes in structural framing systems for tall building.The building frame was traditionally designed to resist the gravitational loads 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译5which are always present and form the reason for its very existence. These loads derive from the self-weight of the vertical and horizontal structural components, including the cladding, and the superimposed floor loadings. There will give rise to necessary minimum cross-sectional areas, based on allowable stress levels, for the vertical column and wall elements, in the design.In the past three decades, therefore, designers have sought to evolve structural systems which will reduce as far as possible the cost and weight of materials, while simultaneously fulfilling the primary building function. A suitable arrangement of the vertical column and wall elements, allied to the horizontal floor system, is required which will provide an economic method of resisting lateral forces and minimizing the additional height premium.Although the provision of load paths for gravitational forces is limited, there is considerable scope for organizing the structural system to resist lateral forces as efficiently as possible. This may be achieved by the judicious disposition of the vertical elements and their interconnection by horizontal structural components in order to resist moment by axial forces rather than bending moments in these vertical elements.In general, different structural systems have evolved for residential and office buildings have been constructed in which the two categories have been mixed, in a deliberate attempt to revitalize moribund city center areas.The basic functional requirement of a residential building is the provision of discrete dwelling units for groups of individuals. These have common requirements of living, sleeping, cooking and toilet areas, which must be separated by partitions which offer fire and acoustic insulation between dwelling.Framed structures may be usefully employed for residential buildings, since the presence of permanent partitions allows the column layout to the correspond to the architectural plan. However, these depend on the rigidity of the joints for their 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译6resistance to lateral forces, and tend to become uneconomic at heights above 20-25 stories, depending on the overall dimensions, when wind forces begin to control the design, and it becomes increasingly difficult to meet stiffness requirements. Since their introduction in the late 1940s, shear walls, acting either independence or in the form of core assemblies, have been used extensively as additional stiffening elements for traditional frame structures.In order to provide adequate fire and acoustic insulation between dwellings, infill panels of brickwork or blockwork are introduced into the frames. Although techniques exist for assessing the influence of these infill panels on the strength and stiffness of the frame, they are generally assumed to be non-load-bearing, in view of the designers fear that they may be either removed or perforated for a change of function at some future date, as well as the difficulty of achieving a tight fit between an infill panel and the surrounding frame. Consequently, later trends were to utilize the walls which are required for space division in a structural context, and omit the relatively heavy infills which could not be employed in a load resisting capacity. This has led to the development of the shear wall building, in which structural walls are used to divide and enclose space, while simultaneously resisting both vertical and horizontal loads. These walls are generally of precast large panel or reinforced concrete in-situ construction, but concrete blockwork and brickwork have also been employed, allied to precast floor slab construction. Since the functional plan requires a large number of division walls between dwellings, it is frequently found that the minimum thickness required for fire and acoustic insulation will be adequate for structural requirements also.Functional requirements for this form of building have given rise to the slab block of cross-wall construction, in which horizontal movement of occupants is achieved by long corridors running along the length of the building, with apartments positioned on either side, or to point blocks in which apartments are grouped around the area of vertical transportation, lifts and stairwells. In each case, 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译7the basic structure consists of orthogonal systems of shear walls, connected by floor slabs and perhaps lintel beams spanning across door, window or corridor openings, to form a stiff structure. Structural cores, which consist of assemblies of walls along their vertical edges to form open or partially closed box sections enclosing lift shafts and stair wells act as additional strong points in such buildings, and can play a major role in resisting lateral forces.In a design, the shear walls must be sufficiently stiff to meet the imposed deflection criterion, and in addition, should be so arranged that tensile stresses caused by wind forces are less than the compressive stresses produced by the weight of the building. A careful arrangement of walls can improve structural efficiency which consists of a series of cross-walls and two flank walls running across the width of the building. As a reasonable approximation, each wall will carry the vertical loads associated with the surrounding tributary area shown hatched in the figure, so that the compressive stresses in the cross walls will be roughly twice those in the flank walls, if they are of the same thickness, However, if all walls deflect equally under the action of the wind forces, as a result of the high in-plane rigidity of the floor slabs, the bending moment and associated stresses in each wall will be proportional respectively to its moment of inertia and section modulus. Consequently, the maximum tensile stresses in the flank walls will be roughly four times those in the cross-walls. The flank walls may then be subjected to unacceptable tensile stresses. A more efficient structure could be achieved by splitting each flank wall into two units, perhaps by forming an architectural feature by having them out of alignment. The flank walls would then be subjected to roughly the same wind moments as the cross-walls, and the tensile wind stresses reduced by a factor of more than four.Shear wall structures are well suited for resisting seismic loadings, and have performed well in recent disasters. They tend to become economical as soon as lateral forces affect the design and proportioning of flat plate or framed systems. 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译8However, they do possess the disadvantage of an inherent lack of flexibility for future modifications, while discontinuities are frequently required at the critical ground level area to provide a different architectural function on the ground floor, and special detailing becomes necessary. A relative recent innovation which is particularly suitable for residential blocks is the staggered wall-beam system. The structure consists of a series of parallel bents, each comprising columns with perforated story-height walls between them, in alternate bays. Each wall panel acts in conjunction with, and supports, the slab above and below to form a composite I-beam. By this device, large clear areas are created on each floor, yet the floor slabs span only half the distance between adjacent wall beams, from the bottom of one to the top of the next. The wind shears are transmitted through the floor slabs from the wall beams on one story to shoes on the next. Similar systems are possible with staggered trusses rather than stagtered walls.The essential functional requirement of an office building is the provision of areas unobstructed as possible by walls or columns to allow each occupant to design the partitioning and space enclosure most suitable for his particular business organization. The partition layout will generally alter when tenants change, and this necessitates flexibility in the distribution of the various services to any particular floor. As a result, services tend to be carried vertically within one or more service cores, and a distribution network run beneath the structural floor slab to the entire floor area.By judicious planning of the column layout to maximize the open floor areas, shear wall-frame interactive structures may also be employed for office blocks, although the presence of the columns may make it difficult to achieve the desired planning flexibility.Possibly the simplest method of creating open floor areas is to use a central 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译9concrete shear core, which carries all essential services and which is designed to resist all lateral forces. The floor system spans between the central core and the exterior faade columns, and a large unobstructed floor area is created between the two vertical components. The exterior columns can be designed to be effectively pin-connected at each floor level, so that they transmit vertical forces only, in conjunction with the interior core. These exterior columns are frequently precast to form a sculptured faade. Another possibility is to provide a core at each end, especially if the building is slender. However, in order to support the floor slabs in the interior, it is then necessary to provide a spine beam running between the cores, which will require additional supporting interior columns. If the floor spans are long, it may become economic to introduce additional columns in the interior to reduce the span of the slabs.In some situations, a different architectural arrangement is desired at ground level, which precludes the columns being taken right down to ground level. In that case, heavy cantilevers are required to collect the column loads from the levels above and transmit then to the central core.An alternative approach is to introduce a roof truss in either prestressed concrete or steel construction, at the top of the core. The floor slabs may then be supported between the core and a system of steel hangers suspended from the roof truss. The system has the architectural advantage of lightness of faade, and can simplify construction on a congested city site. The core may be slipformed, and the floor slabs cast on site and simply hoisted into position. However, there is the inherent structural disadvantage that the core is subjected to the entire weight of the building , compressive forces are high at roof level, and settlement may pose problems. Intermediate level trusses will assist in carrying the external tie forces and reduce the extensions of the hangers. A further increase in lateral stiffness can be achieved if the central core or shear wall system is tied to the exterior columns by deep (usually story height) flexural 广西科技大学土木建筑工程学院 2013 届毕业设计外文翻译10members or trusses at the top and possibly at other intermediate levels. The effect of these connections is to create an overall framed system, which mobilizes the axial stiffness of the exterior columns to resist wind forces. The objective is to cause the structure to act more as a vertical cantilever beam, and so resist the wind by axial forces in, rather than by bending of. The larger lever arm involved ensures that large moments of resistance may be produced by relatively low column forces.The first reinforced concrete building to utilize this concept was the 51-story Place Victoria Building in Montreal (1964) , in which an X-shaped core is linked at four levels by story-high graders to the massive corner columns.As building become taller, the use of a core on its own to resist lateral forces will lead to unusually large cores, occupying too large a ratio of a given floor area, and leading to uneconomic solu