英文翻译

河北联合大学轻工学院

英文翻译

专业：土木工程

班级：08土木工程1班姓名：蔡建龙

学号：200815110211 指导教师：韩建强

2012 年 5 月 25 日

正文：

建筑材料

建筑材料必须具有对结构有用的某些物理性质。首先，建筑材料必须能够承受荷载或重量，而不会永久改变其原有的形状。当荷载施加到结构单元上时，材料将发生变形，也就是说，线材将伸长或梁将会弯曲。然后卸载后，线材和梁将恢复原状。材料的这种性质称为弹性。如果某种材料是非弹性的，在卸荷后结构将残留变形，重复加荷和卸荷，结构的变形将持续增加，直至最后结构失效。用于建筑结构的所有材料，诸如砖石、木材、钢材、铝材、钢筋混凝土的塑料等，在一定范围的荷载作用下均表现出弹性如果荷载增加超过这个范围，材料将表现出两种类型的性质：脆性和塑性。若为前者，材料将会突然断裂；若为后者，材料在达到某一荷载（屈服强度）开始塑性流动，最后破坏。例如，钢材表现出塑性，石材则是脆性的。材料的最终强度用材料破坏时的极限应力来表示。

建筑材料第二个重要性质是刚度。这一性质用弹性模量来表示，弹性模量是应力（单位面积上的力）和应变（单位长度上的变形）的比值。因而弹性模量是衡量材料在荷载作用下抵抗变形能力的指标。对于相同荷载作用下相同面积的两种材料，弹性模量越高者变形越小。结构钢材，其弹性模量是3*108LB/IN2，或21000000kg/cm2，是铝材刚度的3倍、混凝土刚度的10倍、木材刚度的15倍。

砌体，砌体包含天然材料，如石材、人造产品如混凝土砌块。砌体出现在远古时期。在古巴比轮城市，泥土砖用于建造非宗教性建筑物，而石材被广泛用语尼罗河流域雄伟的寺庙。高及481ft(147m)的埃及大金字塔是最为壮观的石工材料。最初，砌块的叠砌是不用胶粘剂的，但所有现代土砖或页岩砖以及混凝土砌块。

砌体材料基本上属于受压材料，不能承受张拉力，亦即拉力。砌体的极限抗压强度取决于砌体和砂浆。极限强度在1000到4000lb/in2(70~280 kg/cm2)之间变化，其值取决于所有块体和砂浆的具体结合。

木材，木材是一种最古老的建筑材料，是少数具有抗拉性能的天然材料之一。全世界已经发现的木材种类有数百种，每一类都表现出不同的物理特性。只有少数木材在建筑中被用做结构构件。例如，在美国，600多中木材中仅有20种被用于结构。这些木材通常是一些针叶树或软木材，主要因为这两种木材资源丰富以及易于成型。在美国建筑中较为普遍使用的木材树种是花期松、南木松、云杉和红木。这些木材的极限抗拉强度变化范围为5000~8000 lb/in2（350~560 kg/cm2）。硬木材主要用于细木工或用于铺地板之类的室内装修。

由于木材本身有细胞状结构，其顺纹强度要大于其横纹强度，木材顺纹的抗拉强度和抗压强度尤其高，并且有很好的抗弯强度。这些性质使得木材成为建筑结构中柱和梁的理想材料。但是，由于桁架杆件中抗拉强度取决与各种杆件的连接，所以木材不能有效地在桁架中用作受拉构件。尽管为了利用木材的抗拉强度制造出许多金属节点，但很难设计出与顺纹剪切强度或抗裂强度关系不大的接头。

钢材，钢材是一种优异的结构材料。与其他材料相比，钢材有高强度质量比（单位质量的强度），即在相同体积条件下其质量是木材的10倍以上。钢材具有较高的弹性模量，这就使得钢筋在荷载作用下变形较小。钢材可被轧制成各种不同的结构形状，如工字型梁、钢板和压型钢板，还能被铸造成复杂形状，也能用以生产出钢丝和钢绞线，用作悬索桥和旋索屋面的钢缆，电梯升运机缆索，或用作预应力混凝土的钢丝绞线。钢制构件可以用多种方法进行连接，如螺栓连接、铆接或焊接。碳素钢易遭氧化导致腐蚀，必须防止其与大气的接触，可采用在其上刷防锈或将其埋入混凝土的办法。当温度高于700F（371℃）时，钢材将迅速丧失其强度，因而必须在其外包裹上防火材料（通常为混凝土）对其加以保护。

合金元素如硅或锰的加入使钢材强度变得更高，其抗拉强度可达250000 LB/IN2（17500kg/cm2）。当结构构件的尺寸变得重要时，如摩天大楼的柱子，就要使用这类合金钢。

铝材，当轻质、强度和防腐蚀能力成为建筑考虑的重要因素时，铝材作为一种建筑材料就显得特别有用。因为纯铝极软，易延展，必须在其中加入锰、硅、锌和铜这些合金元素，使其获得结构所要求的强度。建筑用铝合金表现出弹性，其弹性模量是钢材的1/3，因而在相同荷载作用下，其变形为钢材的3倍。铝合金的密度为钢材的1/3，因而在相似强度条件下，铝合金构件比钢材构件轻。铝合金的极限抗拉强度范围在2000~6000lb/in2(1400~4200kg/cm2)。铝材能被加工成各种状态，可以被挤压成工字型梁，拔成线材和杆件，辊压成铝箔和板材。铝构件可以像钢材一样采用铆接、螺钉连接以及（较少地）焊接等方式进行连接。铝除了用作建筑和预制房屋的框架构件以外，还被广泛地用作窗框，以及幕墙建筑物的幕墙材料。

混凝土，混凝土是水、砂石子和波特兰水泥和混合物。碎石、人造轻骨料、贝壳经常被用以代替天然石料。波特兰水泥，是将由钙质材料和黏土质材料形成的混合物在窑中进行煅烧然后进行粉磨而形成的。混凝土强度即源于磨细的水泥与水混合时经水化而硬化的过程。在理想的混合状态下，混凝土由占其体积大约3/4的砂、石子和占其体积1/4的水泥浆组成。混凝土的物理特性对其组成成分变化是极其敏感的，所以为了获得混凝土在强度和收缩等方面特定的效果，必须

对这些组成材料的配料进行特定的设计。当往模具或模板中浇注时，混凝土中含有大量并非用于水化而是要蒸发掉的水。混凝土硬化时，经过一段时间将蒸发掉多余的水而产生收缩，这种收缩通常将导致细裂缝的发展。为了将这些裂缝减至最少，混凝土硬化时必须保持潮湿状态至少在5天以上。以为混凝土的水化过程能持续进行多年，故其强度能够持续增长。事实上，常把混凝土28天的强度视为标准强度。

混凝土在荷载作用下会发生弹性变形。尽管混凝土的弹性模量是钢材的1/10，但由于其强度也大约是钢材的1/10，所以它们有相似的变形。混凝土主要用作抗拉材料，其抗拉强度可不予考虑。

钢筋混凝土，钢筋混凝土中配有钢筋，用以承受混凝土构件中的拉力。这些钢筋的直径范围在0.25in（0.64cm）~2.25in(5.7cm)，其表面带肋，以保证与混凝土的黏结。尽管钢筋混凝土在很多国家得到发展，但其发展一般归功于约瑟夫，一位法国园丁，他在1868年曾使用钢筋网片来加强混凝土管，因为温度变化时，钢材与混凝土胀缩系数相同，所以这种做法是可行的，如若不然，钢材与混凝土的黏结会因温度的变化导致两者变形不一致而破坏。钢筋混凝土可以浇注成各种形状，如梁、柱、板和拱，因而适用于特殊形态的建筑物。钢筋混凝土的极限强度抗拉强度可能会超过10000lb/in2(700kg/cm2)，尽管产生的大部分商品混凝土的强度低于6000lb/in2(420kg/cm2)。

塑料，塑料因其多样性、强度、耐久性和轻质而迅速成为一种重要的建筑材料。塑料是一种合成材料或树脂，能按要求塑造成各种形状，采用有机物作胶粘剂。有机的塑料分为两大类：热固性塑料和热塑性塑料。热固性塑料受热时发生化学变化而变硬，一旦成型，着类塑料不能在塑成型。热塑性塑料在高温时仍保持柔软，冷却后才变硬，这类塑料通常不能用作建筑材料。

译文：

Build materials

Materials for building must have certain physical properties to be structurally useful. primarily ,they must be able to carry a load , or weight , without changing shape permanently . when a load is applied to a structure member , it will deform ; that is , a wire will stretch or a beam will bend . however , when the load is removed ,the wire and the beam come back to the original position ,this material property is called elasticity ,if a material were not elastic and a deformation were present in structure after removal of the load , repeated loading and unloading eventually would increase the deformation to the point where the structure would become useless . all material used in architectural structure , such as stone and brick , wood , steel , aluminum , reinforced concrete ,and plastics , behave elastically within a certain defined range of loading . if the loading is increased above the range , two type of behavior can occur ; brittle and plastic . in the former , the , material will break suddenly . in the latter , the material begins to flow at a certain load (yield strength) , ultimately leading to fracture . as example , steel exhibits plastic behavior , and stone is brittle . the ultimate strength of a material is measured by the stress at which failure (fracture) occurs .

A second important property of a building is its stiffness . this property is defined by the elastic modulus ,which is the ratio of the stress (force per unit area) , to the strain (deformation per unit length) . the elastic modulus , therefore , is a measure of the resistance of a material to deformation under load . for two material to equal area under the same load , the one with the higher elastic modulus has the smaller deformation .structural steel , which has an elastic modulus of 30 million pounds per square inch (psi) , or 2100000 kilograms per square centimeter , is 3 time as stiff as aluminum , 10 times as stiff as concrete , and 15 times as stiff as wood .

Masonry consists of natural materials , such as stone , or manufactured products , such as brick and concrete block . masonry has been used since ancient times ; mud brick were used in the city of Babylon for secular buildings , and stone was used for the great temples of the Nile Valley . the great pyramid in Egypt . standing 481 feet (147 meters) high , is the most spectacular masonry construction . masonry units

originally were stacked without using any bonding agent , but all modern construction uses a cement mortar as a bonding material . modern structural materials include stone , brick of burnt clay or slate , and concrete blocks .

Masonry is essentially a compressive material ; it cannot withstand a tensile force , that is , a pull. The ultimate compressive strength of bonded masonry depends on the strength of the masonry until and the mortar. The ultimate strength will vary form 1000 to 4000 psi (70 to 280 kg/sq cm), depending on the particular combination of masonry unit and mortar used.

Timber is one of the earliest construction materials and one of the few natural materials with good tensile properties. Hundreds of different species of wood are found throughout the world , and each species exhibits different physical characteristics. Only a few species are used structurally as framing members in building construction. In the untied states, for instance, out of more than 600 species of wood, only 20 species are used structurally. These are generally the conifers, or softwoods, both because of their abundance and because of the ease with which their wood can be shaped. The species of their more commonly used in the untied states for construction are Douglas fir, southern pine, spruce, and redwood. The ultimate tensile strength of these species varies form 5000 to 8000 psi (350 to 560 kg/sq cm). Hardwood are used primarily for cabinetwork and for interior finishes such as floors.

Because of the cellular of wood, it is stronger along the grain than across the grain. Wood id particularly strong in tension and compression parallel to the grain. And it has great bending strength. These properties make it ideally suited for columns and beams in structures. Wood is not effectively used as a tensile member in a truss, however, because the tensile strength of a truss member depends upon connections between members. It is difficult to devise connections which do not depend on the shear or tearing strength along the grain, although numerous metal connectors have been produced to utilize the tensile strength of timbers.

Steel is an outstanding structural material. It has a high strength on a pound-for-pound basis when compared to other materials, even thought its volume-for-volume weight is more than times that of wood. It has a high elastic modulus, which results in small deformations under load. It can be formed by rolling into various structural shapes such as I-beams, plates, and sheets; it also can be cast into complex shapes; and it is also produced in the form of wire strands and ropes for use as cables in suspension bridges and suspended roofs, as elevator rope, and as wire

for pestering concrete. Steel element can be joined together by various means, such as bolting, riveting, or welding. Carbon steels are subject to corrosion through oxidation and must be protected form contact with the atmosphere by painting them or embedding them in concrete. Above temperatures of about 700F(371℃), steel rapidly loses its strength, and therefore it must be covered in a jacket of a fireproof material(usually concrete) to increase its fire resistance.

The addition of alloying elements, such as silicon or manganese, results in higher strength steels with tensile strengths up to 250000 psi(17500kg/sq cm). These steels are used where the size of a structural member become critical, as in the case of columns in a skyscraper.

Aluminum is especially useful as a building when lightweight, strength, and corrosion are all important factors. Because pure aluminum is extremely soft and ductile, alloying elements, such as magnesium, silicon, zinc, and copper, must be added to it to impart the strength required for structural use. Structural aluminum alloys behave elastically. They have an elastic modulus one third as great as steel and therefore deform there times as much as steel under the same load. The unit weight of an aluminum alloy is one third that of steel, and therefore an aluminum member will be lighter than a steel member of comparable strength. The ultimate tensile strength of aluminum alloys ranges form 20000 to 60000 psi (1400 to 4200kg/sq cm).

Aluminum can be formed into a variety of shapes; it can be extruded to form I-beams, drawn to form wire and rode, and rolled to form foil and plates. Aluminum members can be put together in the same way as steel by riveting, bolting, and (to a lesser extent) by welding. Apart form its use for framing members in buildings and prefabricated housing, aluminum also finds extensive use for window frames and for skin of the building in curtain-wall construction.

Concrete is a mixture of water, sand and gravel, and Portland cement. Crushed stone, manufactured lightweight stone, and seashells are often use in lieu of natural gravel. Portland cement, which is a mixture of materials containing calcium and clay, is heated in a kiln and then pulverized. Concrete derives its strength form the fact that pulverized Portland cement, when mixed with water, hardens by a process called hydration. In an ideal mixture, concrete consists of about three fourths sand gravel (aggregate) by volume and one cement paste. The physical properties of concrete are highly sensitive to variations in the mixture of the components, so a particular combination of these ingredients must be custom-designed to achieve specified results

in terms of strength or shrinkage. When concrete is poured into a mold or form, it contains free water, not required for hydration, which evaporate. As the concrete hardens, it releases this excess water over a period of time and shrinks. As a result of this shrinkage, fine cracks often develop. In order to minimize these shrinkage cracks, concrete must be hardened by keeping it moist for at least 5 days. The strength of concrete in time because the hydration process continues for years; as a practical matter, the strength at 28 days is considered standard.

Concrete deform under load in an elastic manner. Although its elastic modulus is one tenth that of steel, similar deformations will result since its also about one tenth that of steel. Concrete is basically a compressive material and has negligible tensile strength.

Reinforced concrete, Reinforced concrete has steel bars that are placed in a concrete member to carry tensile force. These Reinforced bars, which range in diameter form 0.25 inch(0.64cm) to 2.25 inches (5.7cm), have wrinkles on the surfaces to ensure a bond with the concrete. Although reinforced concrete was developed in many countries, its discovery usually is attributed to Joseph Monnier, a French gardener, who used a wire network to reinforce concrete tuber in 1868. this process is workable because steel and concrete expand and contract equally when temperature change. If this were not the case, the bond between the steel and concrete would be broken by a change in temperature since the two materials would respond differently. Reinforced concrete can be molded into innumerable shapes, such as beams, columns, slabs, and arches, and is therefore easily adapted to a particular form of building. Reinforced concrete with ultimate tensile strengths in excess of 10000 psi (700 kg/sq cm) is possible, although most commercial concrete is produced with strengths under 6000 psi (420 kg/sq cm).

Plastic plastics are rapidly becoming important construction materials because of the great variety, strength, durability, and lightness. A plastic is a synthetic material or resin which can be molded into any desired shape and which uses an organic substance as a binder. Organic plastic are divided into two general groups; thermosetting and thermoplastic. The thermosetting group becomes rigid though a chemical change that occurs when heat is applied; once set, these plastics cannot be remolded. The thermoplastic group remains soft at high temperatures and must be cooled before becoming rigid; this group is not used generally as a structural material.

正文：

预应力混凝土

混凝土抗压但不抗拉，其抗拉强度是其抗压强度的8%~14%。由于混凝土的抗拉能力如此低，在荷载作用早期，混凝土内部即出现弯曲裂缝。为减缓或裂缝发展，可沿结构构件纵向施加轴心力或偏心力。这种力通过消除或尽可能地减少使用荷载作用下跨中临界截面的拉应力，以防止裂缝发展，从而增大了截面抵抗弯曲、剪切和扭转的能力。当全部荷载作用在结构上时，混凝土截面表现出弹性，混凝土的极限抗压能力几乎在混凝土全截面高度得到有效利用。

这种沿纵向施加在混凝土构件上的力，称为预应力，也就是在横向的自重恒载、活载或瞬间的水平活载作用之前，对构件跨度方向的截面预加了压应力。所施加的预应力类型及其大小，主要取决于建筑体系的类型、跨度和设计长细比。由于预应力沿着或平行于构件轴线方向施加在构件上，这种预加应力的原理一般称为线性预加应力法。

用于盛装流体的箱罐、管道、压力反应堆容器的环形预应力，基本上遵循线性预应力的基本原理。作用在圆形或球形结构上的环形箍筋或环抱应力克服了由内部的压力所引起的曲面外层纤维的拉应力。

很明显，为了消除或尽可能减少有全部静荷载和活荷载所引起的纯粹的拉应力，在这些荷载作用之前，预应力结构构件中已经产生了持久的压应力。对于钢筋混凝土，一般设想混凝土中的抗拉强度可以忽略不计。这是因为弯矩引起的拉力由钢筋与混凝土之间产生的粘结力抵抗。因而一旦构件达到其使用荷载作用下的极限状态，钢筋混凝土中的开裂和变形不可恢复。

与预应力钢筋作用不同的是，钢筋混凝土构件中的钢筋没有在构件上施加任何力。为了在预应力构件中产生预应力，预应力筋预先对构件中主动施加荷载，使得裂缝和变形可相对易于控制恢复。一旦超过混凝土的弯曲抗拉强度，预应力构件开始像钢筋混凝土构件一样工作。在相同跨度和荷载条件下，预应力构件比钢筋混凝土构件截面的65%~80%。因此，预应力构件所用混凝土较少，大约是钢筋混凝土中混凝土用量的20%~35%。然而，不幸的是，预应力构件在材料用量上虽然节约了，但其需要高质量材料的代价较高，可以说在造价上与钢筋混凝土持平。另外，不管采用哪种体系，预应力操作本身也会引起费用的增加；由于预应力构件截面通常由翼缘和薄壁腹板组成，所以支模较复杂。

尽管有额外增加的费用，如果生产很多的预制构件，至少预应力体系和钢

筋混凝土体系之间初始费用的差别不是很大。而且由于预应力构件需要的维护费用较少，因混凝土质量控制较好使其可能具有更长的使用寿命，以及上层建筑的累积重量较小使其具用更轻型的基础，因而其间接的长期费用减少是相当可观。

一旦钢筋混凝土梁跨超过70~90in（1.3~27.4m），梁自重变得过大，使构件粗大，从而使构件长期变形和裂缝增大。对于大跨度的情况，建造拱形结构的费用昂贵，且因存在较大的长期收缩和徐变使其性能不理想。因此，大跨度结构，如分段拼装式桥或斜拉桥只能采用预应力结构来建造。

预应力混凝土不是一个新概念，这一概念可以追溯到1872年，当时加州的一名工程师P.H.Jackson申请了预应力系统的专利，其预应力系统采用了拉杆和砌块来建造梁或拱。从那以后相当时间里，预应力的发展进程缓慢，这是由于当时没有能够克服预应力和损失的高强钢材。直到内布拉斯加州的R.E.Dill亚历山大认识到混凝土的收缩和徐变（横向的材料流动）引起预应力损失，随后发展了一种观念，提出对无粘结预应力筋实施逐级张拉可以补偿钢筋与时间相关的应力损失，这种应力损失由徐变和收缩使构件长度缩短而引起。在20世纪20年代早期，明尼阿波利斯市的W.H.Hewett提出了环形预应力理论，通过应用螺旋扣，在混凝土箱壁四周环绕水平钢筋施加环向应力，以防止由容器内部流体压力所引起的开裂，从而获得水密效果。其后，箱罐和管的预加应力在美国获得加速发展，在后来的20~30年时间里，人们建造了成千上万个用作用水、液体或气体容器的箱罐，铺设了数英里长的预应力管道。

线性预应力在欧洲和法国继续发展，尤其通过Eugene Freyssinet 富有独创性的工作，他在1926~1928年提出通过使用高强度和高延性的钢材来克服预应力损失的方法。在1940年，他提出了现在被广泛接受的著名的弗式（预应力）体系。

20世纪30~60年代，英国的P.W.Abeless提出和发展了部分预应力的概念。德国的F.Leonhardt、俄罗斯的V.Mikhailov和美国的T.Y.Lindui对预应力混凝土的技术和科学的设计做出了贡献。在这点上，T.Y.Lin的荷载平衡方法特别值得一提，因为它大大地简化了设计过程，尤其是在连续结构中。这些20世纪预应力的发展使得预应力在全世界尤其是在美国得到了广泛的应用。

今天，预应力混凝土被应用于建筑物、地下结构、电视塔、流体容器、海上结构、发电站、核反应堆容器，以及包括分段拼装式桥梁和斜拉桥在内的无数类型的桥梁体系。他们展示了预应力概念的多面性和应用的广泛性。所有这些结构的发展和建造的成功很大程度上归功于材料科学的进步，尤其是预应力钢筋的发展，一级估计预应力短期和长期损失的知识积累。

译文：

Prestressed Concrete

Concrete is strong in compression, but weak in tension: its tensile strength varies from 8 to 14 percent of its compressive strength. Due to such a love tensile capacity ,flexural cracks develop at early stages of loading .In order to reduce or prevent such cracks from developing, a concentric or eccentric force is imposed in the longitudinal direction of the structural element. This force prevents the cracks from developing by eliminating or considerably reducing the tensile stresses at the critical misspend and support sections at service load, thereby raising the bending,shear,and torsion capacity of the concrete in compression can be efficiently utilized across the entire depth of the concrete sections when all loads act on the structure.

Such an imposed longitudinal force is called a prestressing force,i.e.,a compressive force that priestesses the sections along the span of the structural element prior to the application of the transverse gravity dead and live loads or transient horizontal live loads. The types of prestressesing force involved, together with its magnitude, are determined mainly on the basis of the type of system to be constructed and the span length and slenderness desired. Since the prestressing force is applied longitudinally along or parallel to the axis of the member, the prestressing principle involved is commonly known as linear prestressing.

Circular prestressing, used in liquid containment tanks, pipes, and pressure reactor vessels, essentially follows the same basic principles as does linear prestressing, The circumferential hoop, or”hugging” stress on the cylindrical or spherical structure, neutralizes the tensile stresses at the outer fibers of the curvilinear surface by the internal contained pressure.

It is plain that permanent stresses in the prestressed structural member are created before the full dead and live loads are applied in order to eliminate or considerably reduce the net tensile stresses caused by these loads. With reinforced concrete, it is because the tensile forces resulting from the bending moments are resisted by the bond created in the reinforcement process. Cracking and deflection are therefore essentially irrecoverable in reinforced concrete once the member has reached its limit state at service load.

The reinforcement in the reinforced concrete member does not exert any force of its own on the member, contrary to the action of prestressing steel. The steel required to produce the prestressing force in the prestressed member actively preloads the member , permitting a relatively high controlled recovery of cracking and deflection. Once the flexural tensile strength of the concrete is exceeded, the prestressed member starts to act like a reinforced concrete element.

Prestressed member are shallower in depth than their reinforced concrete counterparts for the same span and loading conditions. In general, the depth of a prestressed concrete member is usually about 65 to 80 percent of the depth of the equivalent reinforced concrete member. Hence, the prestressed member requires less concrete,and about 20 to 35 percent of the amount of reinforement. Unfortunately, this saving in material weight is balanced by the higher cost of the higher quality materials needed in prestressing. Also, regardless of the system used, prestressing operations themselves result in an added cost: formwork is more complex, since the geometry of presstressed sections is usually composed of flanged sections with thin webs.

In spite of the these additional costs, if a large enough number of precast units are manufactured, the difference between at least the initial costs of prestressed and reinforced concrete systems is usually not very large. And the indirect long-term savings are quite substantial, because less maintenance is needed, a longer working life is possible due to better quality control of the concrete, and lighter foundations are achieved due to the smaller cumulative weight of the superstructure.

Once the beam span of reinforced concrete exceeds 70 to 90 feet (21.3 to 27.4m), the dead weight of the beam becomes excessive, resulting in heavier members and, consequently, greater long-term shrinkage and creep they undergo. Very large spans such as segmented bridges or cable-stayed bridges can only be constructed through the use of prestressing.

Prestressed concrete is not a new concept, dating back to 1872, when P.H.Jackson, an engineer from California, patented a prestressing system that used a tie rod to construct beams or arches from individual blocks. After a long lapse of time during which little progress was made because of the unavailability of high-strength steel of the shrinkage and creep (transverse material flow) of concrete on the loss of prestress. He subsequently developed the principles of circular prestressing. He hoop-stressed horizontal reinforcement around walls of concrete tanks through the use

of turnbuckles to prevent cracking due to internal liquid pressure, thereby achieving water tightness. Thereafter, prestressing of tanks and pipes developed at an accelerated pace in the United States, with thousands of tanks for water, liquid, and gas storage built and much mileage of prestressed pressure pipe laid in the two to three decades that followed.

Linear prestressing continued to develop in Europe and in France, in particular through the ingenuity of Eugene Freyssined, who proposed in 1926~28 methods to overcome pretress losses through the use of high-strength and high-ductility steels.In1940, he introduced the now well-known and well-accepted Freyssinet system.

P.W.Abeles of England introduced and developed the concept of partial prestressing between the 1930s and 1960s. F.Leonhardt of Germany,V.Mikhailov of Russia, and T.Y.Lin of the United States also contributed a great deal to the art and science of the design of prestressed concrete.Lin’s load-balancing method deserves particularl mention in this regard, as it considerably simplified the design process,particularly in continuous prestressing throughout the world, and in the United States in particular.

Today, prestressed concrete is used in buildings, undergroud structures, TV towers, floating storage and offshore structures, power stations, nuclear reactor vessels, and numerous types of bridge system including segmental and its all-encompassing application. The success in the development and construction of all these structures has been due in no small measures to the advances in the technology of materials, particularly prestressing steel, and the accumulated knowledge in estimating the short-and long-term losses in the prestressing forces.