【正文】 eniently be used for carrying concrete or other building materials. Dumpers have the earth container over the front axle on large rubbertyred wheels, and the container tips forwards on most types, though in articulated dumpers the direction of tip can be widely varied. The smallest dumpers have a capacity of about m 179。此外，由于強(qiáng)度的分布規(guī)律和應(yīng)力的分布規(guī)律之間的相互關(guān)系是困難的。 概率方法，這種方法采用極限狀態(tài)。 （ 2） 概率方法，在這種方法中，主要參 數(shù)被認(rèn)為是隨機(jī)參數(shù)。就目前的趨勢(shì)而言，安全系數(shù)與所使用的材料性質(zhì)及其組織情況無關(guān)，通常把它定義為發(fā)生破壞的條件與結(jié)構(gòu)可預(yù)料的最不利的工作條件之比值。翻斗車的車斗位于大橡膠輪胎車輪前軸的上方，盡管鉸接式翻斗車的卸料方向有很多種，但大多數(shù)車斗是向前翻轉(zhuǎn)的。它能在比較平的地面上挖較深的土（但只能挖機(jī)械本身下面的土），需要時(shí)可以將土運(yùn)至幾百米遠(yuǎn)，然后卸土并在卸土的過程中把土大致鏟平。推土機(jī) 所推運(yùn)的圖的數(shù)量最多，只是運(yùn)輸距離很短。土方設(shè)計(jì)這項(xiàng)工作落到了從事道路設(shè)計(jì)的工程師的身上，因?yàn)橥练焦こ痰脑O(shè)計(jì)比其他任何工作更能決定工程造價(jià)是否低廉。 由于和土木工程中任何其他工種的施工方法與費(fèi)用相比較，土方挖運(yùn)的施工方法與費(fèi)用的變化都要快得多，因此對(duì)于有事業(yè)心的人來說，土方工程是一個(gè)可以大有作為的領(lǐng)域。 設(shè)計(jì)鋼筋混凝土構(gòu)件時(shí)顯然需要處理大量的參數(shù)，諸如寬度、高度等幾何尺寸，配筋的面積，鋼筋的應(yīng)變和混凝土的應(yīng) 變，鋼筋的應(yīng)力等等。對(duì)于梁、柱、墻等構(gòu)件，當(dāng)模板清理干凈后應(yīng)該在其上涂油，鋼筋表面的銹及其他有害物質(zhì)也應(yīng)該被清除干凈。其抗拉強(qiáng)度約為抗壓強(qiáng)度的十分之一。因此，截面的受拉區(qū)必須配置抗拉鋼筋和抗剪鋼筋以增加鋼筋混凝土構(gòu)件中較弱的受拉區(qū)的強(qiáng)度。澆筑基礎(chǔ)前，應(yīng)將坑底土夯實(shí)并用水浸濕 6 英寸，以免土壤 從新澆的混凝土中吸收水分。因此，在選擇混凝土截面時(shí)需要進(jìn)行試算并作調(diào)整，根據(jù)施工現(xiàn)場(chǎng)條件、混凝土原材料的供應(yīng)情況、業(yè)主提出的特殊要求、對(duì)建筑和凈空高度的要求、所用的設(shè)計(jì)規(guī)范以及建筑物周圍環(huán)境條件等最后確定截面。在 1935 年，目前采用的利用輪胎式機(jī)械設(shè)備進(jìn)行土方挖運(yùn)的方法大多數(shù)還沒有 出現(xiàn)。根據(jù)現(xiàn)有的地圖和標(biāo)高，道路工程師應(yīng)在設(shè)計(jì)繪圖室中的工作也并不是徒勞的。拉鏟挖土機(jī)的缺點(diǎn)是只能挖比它本身低的土，不能施加壓力挖入壓實(shí)的土壤內(nèi)，不能在陡坡上挖土，而且挖。在挖掘硬土?xí)r，人們發(fā)現(xiàn)在開挖場(chǎng)地經(jīng)常用一輛助推拖拉機(jī)（輪式或履帶式），對(duì)返回挖土的鏟運(yùn)機(jī)進(jìn)行助推這種施工方法是經(jīng)濟(jì)的。最小的翻斗車的容量大約為 立方米，而最大的標(biāo)準(zhǔn)型翻斗車的容量大約為 179。這個(gè)比值還與結(jié)構(gòu)的破壞概率（危險(xiǎn)率）成反比。 5 此外，根據(jù)安全系數(shù)的不同用途，可以把結(jié)構(gòu)的計(jì)算方法分為： （ 1） 容許應(yīng)力法，在這種方法中，把結(jié)構(gòu)承受最大荷載時(shí)計(jì)算得到的應(yīng)力與經(jīng)過按規(guī)定的安全系數(shù)進(jìn)行折減后的材料強(qiáng)度作比較。 至少在理論上，概率法的主要優(yōu)點(diǎn)是可以科學(xué)的考慮所有隨機(jī)安全系數(shù)，然后將這些隨機(jī)安全系數(shù)組合成確定的安全系數(shù)。 6 這些實(shí)際困難可以采用兩種方法來克服。, and the largest standard types are of about m 179。 early or excessive cracks。 (4) Predicted life of the structure. All these factors are related to economic and social considerations such as： (1) Initial cost of the construction。 (3) Cost of physical and material damage due to the failure of the construction。 and corrosion. Computational methods used to verify structures with respect to the different safety 11 conditions can be separated into: (1)Deterministic methods, in which the main parameters are considered as nonrandom parameters. (2)Probabilistic methods, in which the main parameters are considered as random parameters. Alternatively, with respect to the different use of factors of safety, putational methods can be separated into: (1)Allowable stress method, in which the stresses puted under maximum loads are pared with the strength of the material reduced by given safety factors. (2)Limit states method, in which the structure may be proportioned on the basis of its maximum strength. This strength, as determined by rational analysis, shall not be less than that required to support a factored load equal to the sum of the factored live load and dead load ( ultimate state ). The stresses corresponding to working ( service ) conditions with unfactored live and dead loads are pared with prescribed values ( service limit state ) . From the four possible binations of the first two and second two methods, we can obtain some useful putational methods. Generally, two binations prevail: (1)deterministic methods, which make use of allowable stresses. (2)Probabilistic methods, which make use of limit states. The main advantage of probabilistic approaches is that, at least in theory, it is possible to scientifically take into account all random factors of safety, which are then bined to define the safety factor. probabilistic approaches depend upon : (1) Random distribution of strength of materials with respect to the conditions of fabrication and erection ( scatter of the values of mechanical properties through out the structure )。 and the articulated type of about m 179。 7 2 外文翻譯 Reinforced Concrete Plain concrete is formed from a hardened mixture of cement ,wate