【正文】 注意力，開始主要是在德國。在正常使用極限狀態(tài)下，需驗算構(gòu)件得撓度、最大裂縫寬度和疲勞強度。 1954 年，美國聯(lián)邦最高法院認(rèn)為，立法機關(guān)有權(quán)決定公共場所不但要有利于公眾健康，還要做到賞心悅目；不但要干凈，還要寬敞；不但要通暢，還要布局均衡。 荷載及荷載組合 在橋梁下部結(jié)構(gòu)和基礎(chǔ)設(shè)計中要考慮的荷載包括：從上部結(jié)構(gòu)傳下來的荷載和直接作用于下部結(jié)構(gòu)的基礎(chǔ)的荷載。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被 廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。 到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。到目前為止， AASHTO模型仍被廣泛采用。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范 都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總 結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常 用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量 。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。AASHTO及 LRFD規(guī)范都給出了表格，總結(jié)了橋梁工程重常用才兩的單位重量。主要有：恒載、活載、活載沖擊力或動力作用、風(fēng)荷載以及其他力 —— 如縱向力、離心力、溫度力、土壓力、浮力收縮及徐變、拱肋縮短、安裝應(yīng)力、冰及水流壓力、沖撞力及地震應(yīng)力。 盡管在很多土木工程結(jié)構(gòu)中，幾乎是憑直觀考慮美學(xué)問題，尤其在過去，但橋梁工程師們并沒有忽略美學(xué)方面的訓(xùn)練。隨著 Taa 大橋得跨塌，動力穩(wěn)定被作為問題來研究，并取得了顯著得理論成果。概率設(shè)計法是一種新的設(shè)計方法，這種方法有望替代傳統(tǒng)的確定性方法。 另外，在本世紀(jì)初，鋼筋混凝土在多跨框架結(jié)構(gòu)中的應(yīng)用對結(jié)構(gòu)分析 提出了新的分析要求用19 世紀(jì)的古典分析方法不能用來分析高次靜定結(jié)構(gòu)。用板件組合而成的工字形梁在英國逐漸普及并在小跨度橋梁中得到應(yīng)用。 18世紀(jì) 50年代西歐建造了若干座支承于石制橋墩上的木桁架橋，其跨度達到 200英尺（ 61米）。早在 1840年，法國就在 Grisoles 建造了一座跨度為 39 英尺（ 12 米）的橫跨 Garoyne 運河的混凝土橋梁，但鋼筋混凝土橋直到本世紀(jì)初才出現(xiàn)，而預(yù)應(yīng)力混凝土到 1927年才開始使用。 and was formulated by SaintVenant (1870) , The concept of plasticity attracted researchers and engineers after World War Ⅰ , mainly in Germany , with the center of activity shifting to England and the United States after World War Ⅱ .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 Taa 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 ,Tbeams,concrete box girders ), steel beam and plate girders , steel box girders , posite construction , orthotropic plates , segmental construction , curved girders ,and cablestayed bridges . Prefabricated members are given serious consideration , while interest in box sections remains strong . Bridge Appearance and Aesthetics Grimm ( 1975 ) documents the first recorded legislative effort to control the appearance of the built environment . This occurred in 1647 when the Council of New Amsterdam appointed three officials . In 1954 , the Supreme Court of the United States held that it is within the power of the legislature to determine that munities should be attractive as well as healthy , spacious as well as clean , and balanced as well as patrolled . The Environmental Policy Act of 1969 directs all agencies of the federal governmen