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1、Prestressed Concrete Technology 提纲：摘要：预应力混凝土的定义 正文：预应力混凝土的应用、实例应用讨论：预应力混凝土的优点和缺点总结：预应力混凝土的发展的前景IntroductionPrestressed concrete and reinforced concrete in principle are clearly different. In the design of the reinforced concrete beams, regardless of the concrete can be assumed that the tensile stren
2、gth, for bending moment of tension is caused by reinforced to resist, the tension is through between reinforcement and concrete bonding and passed to the steel. For large scale craze and deformation for, although the high strength concrete has good bonding, to a great extent can restore; But in the
3、concrete and steel bonding between poor ordinary concrete, is in fact cant recover. On the other hand, in the prestressed concrete, the purpose of prestressed reinforced by rapping or through the special is the anchorage to exert a force concrete, so all can have the function of concrete structure.
4、Requirements of prestressed steel is used to produce active component in advance to add load, and cracking and deformation in larger extent can be restored.AbstractIn order to avoid reinforced concrete structure of the premature fracture, make full use of high strength steel and high strength concre
5、te, tried to in the concrete structure or structures under load before use, through the force applied, make by the tensile stress components is reduced, and even in pressure stress state of concrete component.Preloading stress is used to reduce or offset load caused by the concrete tensile stress, a
6、nd the structure of the components in the smaller tensile stress control range, and even in the compression state, to delay the generation of crack in concrete and development, so as to improve the anti-cracking performance component and rigidity.Main textPrestressed concrete component to the method
7、 of pretensioned stressing and posttensioned.1.pretensioned stressingIn the concrete pouring, first by steel wire steel strand or will be composed of the prestressed tendon pulled to a specified stress, and the anchorage anchor in a pier at both ends pedestal, then installation template, the structu
8、re, steel and parts, and then pouring concrete and maintenance. When concrete after the specified strength, relax a pier at both ends of the tendons, through the bond will be the prestressed concrete and tension to produce preloading stress. A method based on first relatively advantageous pedestal l
9、ong, the longest useful to more than one hundred meters, so sometimes called long term method.2. Posttensioned.Firstly perfusion components ,then directly on prestressed method in the component. The general method is placed first after prestressed reinforcement of hole into a casing, the structure,
10、steel and parts, then install the template and pouring concrete. Tendons first through the casing can also wear after. Concrete to strength, with a jack will introduces the pull to the stress and load demand anchor at each end of preloading stress at both ends by the anchorage to concrete component.
11、 In order to protect the tendons from corrosion and restore prestressed concrete and between the rapping, prestressed steel casing and the space between the water filling slurry must be real. Water in the mud up preservative effect, but also beneficial to restore prestressed concrete and between the
12、 rapping. In order to facilitate the construction, sometimes also can be used in the prestressed steel surface coating corrosion materials and plastic casing or oiled paper parcel of unbonded post-tensioned pre-stressing concrete muscle.The characteristics of prestressed concrete. (1).Improve the co
13、mponent of crack resistance. Because of a bear before the loading of prestressed concrete structures in the tension zone for preloading stress exists, so outside load, only when the prestressed concrete is all turned to offset the tensile and tensile strain is more than concrete ultimate tensile str
14、ain, component will craze. While general reinforced concrete structure are not present in the prestressing, the cracking of the size of the load only by concrete ultimate tensile strength, compressive strength for about 1/10 of the) have decided, and crack ability is very low.(2). Increase the stiff
15、ness of the component. Because of the prestressed concrete component of normal use, in the load effect under standard combination may not cracking or only a small cracks, concrete was basically in the elastic stage work, and the stiffness of the component than ordinary reinforced concrete member is
16、increased.(3). Make full use of the high strength materials. As mentioned previously, common reinforced concrete members cant make full use of high strength materials. And prestressed concrete component, prestressed reinforced first is expected to pull, and then out load reinforced stress further in
17、creases, and should be always in high tensile stress state, that is, can effectively use high strength reinforced; And the strength of reinforced high, can reduce the need to the section area. At the same time, should as far as possible using high strength grade of concrete, and high strength steel
18、to coordinates, to get better economic component section size.(4). Expand the application range of the component. Because of the prestressed concrete improvement component crack resistance, and can be used for waterproof, permeability and corrosion resistance requirements of the environment; Using h
19、igh strength materials, the structure to be dexterous, rigidity, distortion, and can be used in the large span and heavy load and load under repeated the structure.Prestressed concrete has been widely applied to industrial and civil building and transportation construction. For example, 冂 prestresse
20、d concrete hollow slab shape roof board, roof, roof beam, crane beam, pre-stress Bridges, railway sleeper used in great quantities such as already. In hydraulic structure also has used to build dock, zhanqiao pier, pile, gate, DiaoDuShi, pressure conduit, circular pool, aqueduct, road, bridge, and w
21、ork the roofing beams and hydropower station workshop crane beam structure component, also can used for the method of prestressed reinforced dam, tunnel lining. For some have unique requirements of the structure, such as the need to prevent water corrosion sea platforms, resistance to high temperatu
22、re and high pressure nuclear power plants, large pressure vessel etc, using prestressed concrete structure is more its superiority, instead of other structure can match.Twenty years to build up a large number of prestressed concrete engineering, Among them are representative of the project have 63 l
23、ayer prestressed concrete floor of guangdong international building; 214 meters tall Qingdao boc building; Monomer prestressed concrete is the biggest of the capital international airport new terminal, etc. (2) the prestressed concrete bridge structure development history in 1955, the railway depart
24、ments in our country the successful development of the first piece of 12 m span of prestressed concrete railway bridge, built in 1956 28 hole 24 m new YiHe across the bridge. In 1957, the highway department in Beijing to build the first seat zhoukoudian prestressed concrete road test bridge, for sin
25、gle span 20 meters simply-supported T bridge. Built in 1959 in lanzhou qilihe HuangHeQiao, 7 main hole for 37.5 m cantilever beam bridge. And HuangHeQiao built new town, for five hole 33 m bridge model T simply supported and hole 66 m the bowstring arch bridge.DiscussionsConcrete is brittle material
26、, high compressive strength, tensile/flexural strength but is low. Concrete tension or the bending, in a very small tensile stress/tensile strain state will craze. Ordinary steel reinforced concrete structure, such as beam, plate, general is being bending state, often reinforced havent under great f
27、lexural stress, concrete bending area has by cracking, and may even make reinforced exposure and rust. Therefore, the common reinforced concrete beam slab structure, the bearing capacity of the steel is far from plays out.Prestressed concrete is the high strength steel wire steel or along the flexur
28、al in advance by the direction for tension, and the tension is reinforced concrete in anchorage, so that by the structure of concrete flexural direction on the preloading stress. Control the size of the compressive pre-stress, can ensure that prestressed beams under bending plate design load, concre
29、te bending area by basic do not produce tensile stress, not crack, can greatly improve the bearing capacity of beams and slabs.Technology make full use of the prestressed concrete compressive strength and high tensile strength of reinforced high characteristics, use material foster strengths and cir
30、cumvent weaknesses, greatly broaden the compound material engineering applications. At present, able to build big span reinforced concrete bridge, floor, tall buildings such as TV tower, etc, are all dependent on prestressed concrete technology.待添加的隐藏文字内容2The loss of prestress mainly comes from the
31、creep of engineering materials, namely in long-term stress the influence of permanent deformation. Press press concrete and tension of prestressed reinforced or steel strand, also can produce creep, lead to the loss of prestress. However, in the prestressed concrete structure design and calculation
32、prestress loss of prestress will be taken into account.Prestressed concrete is generally used to build big span structure or decrease the structure building section, and the dimension. Choose high strength concrete and steel material will be, and can only be imposed higher the added stress, effectiv
33、ely increase or decrease the span structure structure section. Resistance to good, rigidity. Because of component prestress, greatly delayed the occurrence of crack, using in the load, component dont crack, or make crack delayed emergence, so improved the stiffness of the component, increased the du
34、rability of structures. Save material, reducing weight. Its structure because must use high strength materials, so it can reduce the dosage of steel and the component section size, save a steel and concrete, reduce weight structure, the large span and heavy load structure has the obvious superiority
35、. Improve the shear capacity component. Test show that the longitudinal prestressed reinforced plays the role of anchor bolts, hindering component of inclined cracks appear and implementation, and because the curve of the prestressed concrete beams reinforced (beam) vertical component of force will
36、be partly offset shear. Improve the stability of the members under. When the members under long fine is large, in be certain pressure then easy is bent, so that lose stability and destruction. If the reinforced concrete column prestress, make the longitudinal force reinforced tension very tight, not
37、 only prestressed reinforced itself is not easy to bending, and help to improve the resistance of concrete bending around the ability.Improve the resistance of the component fatigue performance. Because has strong of prestressed reinforced, in use for add lotus stage or unloading the stress changes
38、caused by relatively small, therefore, can improve the anti-fatigue strength, this to bear the structure of the dynamic loads is very favorable. But, the complicated process of high quality requirements, they need to have a technology is equipped with skilled professional team. Need to have a certai
39、n special equipment, such as drawing machines, grouting equipment, etc. Prestressed concrete structure of the construction cost is larger, the number of components of the project with high cost less.SummaryIn order to adapt to the development of our national economy, ease traffic problem for people
40、from the inconvenience of production and life, the application of prestressed concrete structure will be more wide range, so we should strengthen the improve the technical level of the prestressed scientific research work. And compared with that of the developed countries we prestressed concrete eng
41、ineering of relatively backward. With our existing strong team, and some units in prestressed technique extension of earned income strength can bear and finish the important scientific research task. At the same time, the design and construction of the separation is also effect on our countrys rapid
42、 development of prestressed concrete structures are one of the factors. So it is necessary to established large powerful prestressed concrete engineering company, take on the major prestressed concrete engineering, and new technology for development research, and do well with the design and construction of the relationship between the, in order to improve the level of prestressed technique in our country.References李国平.预应力混凝土结构发展史.建筑,2008陈嘉辉.预应力钢筋混凝土在建筑中的应用研究.建筑技术,2009
