1、 外文资料： Prestressed Concrete Buildings Prestressed concrete has been widely and successfully applied to building construction of all types. Both precast pretensioned members and cast-tensioned structures are extensively employed, sometimes in competition with one another, most effectively in combinat
2、ion wit each other. Prestressed concrete offers great advantages for incorporation in a total building. It is perhaps the “integrative”aspects of these, that is, structure plus other functions, which have made possible the present growth in use of prestressed concrete buildings. These advantages inc
3、lude the following: Structural strength； Structure rigidity； Durability； Mold ability, into desired forms and shapes； Fire resistance； Architectural treatment of surfaces； Sound insulation； Heat insulation； Economy； Availability, through use of local materials and labor to a high degree. Most of the
4、 above are also properties of conventionally reinforced concrete. Presrressing, however, makes the structural system more effective by enabling elimination of the technical of difficulty, e.g., cracks that spoil the architectural treatment. Prestressing greatly enhance the structure efficiency and e
5、conomy permitting longer spans and thinner elements. Above all, it gives to the architect-engineer a freedom for variation and an ability to control behavior under service conditions. Although prestressed concrete construction involves essentially the same consideration and practices as for all stru
6、ctures, a number of special points require emphasis or elaboration. The construction engineer is involved in design only to a limited extent. First, he muse be able to furnish advice to the architect and engineer on what can he done. Because of his specialized knowledge of techniques relating to pre
7、stressed concrete construction, he supplies a very needed service to the architect-engineer. Second, the construction engineer may be made contractually responsible for the working drawings； that is, the layout of tendons, anchorage details, etc. It is particularly important that he gives careful at
8、tention to the mild steel and concrete details to ensure these are compatible with his presressing details. Third, the construction engineer is concerned with temporary stresses, stresses at release, stresses in picking, handling and erection, and temporary condition prior to final completion of the
9、 structure, such as the need of propping for a composite pour. Fourth, although the responsibility for design rests with the design engineer, nevertheless the construction engineer is also vitally concerned that the structure be successful form the point of view of structural integrity and service b
10、ehavior. Therefore he will want to look at the bearing and connection details, camber, creep, shrinkage, thermal movements, durability provisions, etc., and advise the design engineer of any deficiencies he encounters. Information on new techniques and especially application of prestressing to build
11、ings are extensively available in the current technical literature of national and international societies. The International Federation of Prestressing(I.F.P)has attempted to facilitate the dissemination of this information by establishing a Literature Exchange Service, in which the prestressing jo
12、urnals of some thirty countries are regularly exchanged. In addition, an Abstract is published intermittently by I.F.P The Prestressed Concrete Institute(USA)regularly publishes a number of journals and pamphlets on techniques and applications, and procedures are set up for their dissemination to ar
13、chitects and engineers as well as directly to the construction engineer. It is important that he keep abreast of these national and worldwide developments, so as to be able to recommend the latest and best that is available in the art, and to encourage the engineer to make the fullest and most effec
14、tive use of prestressed concrete in their buildings. With regard to working drawings, the construction engineer must endeavor to translate the design requirements into the most practicable and economical details of accomplishment, in such a way that the completed element or structure fully complies
15、with the design requirement； for example, the design may indicate only the center of gravity of prestressing and the effective prestress force. The working drawing will have to translate this into tendons having finite physical properties and dimensions. If the center of gravity of pre-stressing is
16、a parabolic path then, for pre-tensioning, and approximation by chords is required, with hold-down points suitably located. The computation of pre-stress losses, form transfer stress to effective stress, must reflect the actual manufacturing and construction process used, as well as thorough knowled
17、ge of the properties of the particular aggregates and concrete mix to be employed. With post-tensioning, anchorages and their bearing plates must be laid out in their physical dimension. It is useful in the preparation of complex anchorage detail layouts to use full-scale drawings, so as to better a
18、ppreciate the congestion of mild steel and anchorages at the end of the member. Tendons and reinforcing bars should be shown in full size rather than as dotted lines. This will permit consideration to be given as to how the concrete can be placed and consolidated. The end zone of both pre-tensioned and post-tensioned concrete members
