剛性路面路肩設(shè)計畢業(yè)論文文獻翻譯

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1、外文資料 DESIGN OF RIGID PAVEMENT SHOULDERS Most of the information presented in Section 11 .4 on the design of flexible pavement shoulders is also applicable to the design of rigid pavement shoulders . Some of the features of rigid pavement shoulders that are different from those of flexible pavemen

2、t shoulders are presented here . PCC shoulders have been used in urban expressways for many years, but their use on rural highways began only in the mid 1960s . The good performance of thes epavements has made it the standard practice of many agencies to utilize PCC shoulders for rigid pavements .

3、 Advantages of Tied Concrete Shoulders Concrete shoulders must be tied to the mainline concrete pavements. The advantages of tied concrete shoulders are as follows : 1. The placement of a tied concrete shoulder next to the mainline pavement can substantially increase the load-carrying capacity o

4、f the pavement . The tied concrete shoulder provides support to the edge of the pavement and reduces stresses and deflections in the mainline slab . The shoulder is also benefited by receivin gsupport from the mainline slab, so the damage due to encroaching traffic can be greatly reduced . 2. A ti

5、ed longitudinal joint between mainline and shoulder pavements can be easily sealed to reduce the amount of surface runoff infiltrating into the pavemen tstructure . Field studies conducted in Georgia and Illinois showed that sealing the longitudinal joint greatly reduced the amount of inflow from r

6、ainfall into the pavement structure (Dempsey et al., 1982). 3. Pumping beneath the mainline slab is reduced through the reduction of edge an d corner deflections, the reduction of water infiltration through the longitudinal joint, and the draining of water far away from the traffic lane . 4. Tied

7、 concrete shoulders can reduce differential movements at the longitudinal shoulder joint and do not experience the lane/shoulder dropoff type of distress that occurs so frequently in flexible shoulders . Types of Rigid Pavement Shoulders As with mainline pavements, three types of shoulder pavemen

8、ts are available : jointed plain concrete pavement (JPCP), jointed reinforced concrete pavement (JRCP), and con-tinuous reinforced concrete pavement (CRCP) . Generally, the type of shoulder should match the type of mainline pavement . However, some exceptions may be accepted : 1. For mainline JPCP,

9、 only JPCP shoulders with the same joint spacings as the mainline pavement are recommended, because of their low cost . If JRCP shoulders with longer joint spacings are used, the excessive joint movements may cause problems in the adjacent mainline slabs . All transverse joints should b eprovided

10、with an adequate reservoir and sealed similarly to the mainline joints . 2. For mainline JRCP, either JRCP shoulders that match the mainline pavement in design or JPCP shoulders with closer joint spacings may be used.The use of JPCP shoulders is more cost effective, because no steel reinforcement

11、 is needed . They can be placed at the same time as the JRCP mainline pavement by leaving out the reinforcing steel and cutting transverse joints at shorter intervals . 3. For mainline CRCP, either CRCP shoulders that match the mainline pavement in design or JPCP shoulders with short joint spacings

12、 may be used . The use of short joint spacing for JPCP shoulders will reduce potential movements of the joints that might cause cracking in the mainline CRCP. The elimination of steel reinforcement in the JPCP shoulders can save construction cost . Design of Longitudinal Shoulder Joint Adequate

13、load transfer across the longitudinal shoulder joint must be provided to re - duce the stresses and deflections in both mainline and shoulder slabs . Tied and keyed joints have been used most frequently to ensure a high degree of load transfer . Colley et al. (1978) investigated load transfers in

14、 laboratory slabs constructed with keyed, tied and keyed, and tied butt joints and concluded that all three were equally effective in reducing load-induced strains and deflections. However, the use of a keyed joint without tiebars was not recommended, because of the possibility of shoulder joint sep

15、aration . The excellent performance of the tied butt joint suggests that this type o f construction is feasible and can reduce costs . Malleable tiebars of No. 4 or No. 5 size spaced at 18 to 24 in . (457 to 610 mm) are preferable to stiffer short bars spaced at larger intervals. This will substan

16、tially reduce stress concentration and the possibility of joint spall in the vicinity of the bar . When a PCC shoulder is to be constructed adjacent to an existing pavement, tiebars can be installed by drilling holes in the edge of the existing slab . This can be done by using a tractor-mounted d

17、rill that can drill several holes at one time . Tiebars are installed in the holes by using epoxy or cement grout . The bar should be inserte d into the slab over such a length as to develop sufficient bond . To avoid spalling over the base, a minimum insertion of 9 in . (229 mm) is required . In

18、 the case of new construction, tiebars can be inserted into the plastic concrete near the rear of the slip form paver. Bent bars can be installed manually or by mechanical means . The bent portion can be straightened later to tie the shoulder to the mainline pavement . In addition to tiebars, a key

19、way can be formed to provide additional load transfer capability. The longitudinal joint between the traffic lane and the shoulder should be provided with a sealant reservoir and sealed with an effective sealant . This will minimize the possibility of foreign materials collecting inside the joint t

20、o cause joint spall and reduce the amount of water and deicing salts entering into the joint and corroding the tiebars . Shoulder Thickness Design The thickness design concepts presented in Section 11 .4 .3 for flexible pavement shoulders are also applicable to rigid pavement shoulders . One major

21、 difference is that the inner edge is always more critical for flexible shoulders, because of encroaching traffic,but the outer edge can be more critical for rigid shoulders, because of parking traffic .There is also some question about whether a separately designed shoulder is really needed. Lokken

22、 (1973) reviewed the performance of 16 projects located in 12 states and recommended the use of a 6-in . (152-mm) slab with an alternative tapered slab varying from roadway pavement depth at the longitudinal joint to 6 in . (152 mm) at the outside edge of the shoulder. Slavis (1981) reported on the

23、performance review of these same projects in 1980 and indicated that the vast majority performed extremely well . The only notable deficiency identified in the field investigation was some faulting in one project due to inadequately covered tiebars . It is impossible to place the tiebars at the midd

24、epth both of a 6-in. (152-mm) shoulder and of a thicker mainline pavement ,so it was recommended in the 1980 review that the shoulder thickness be equal to the mainline slab at the longitudinal joint. This thickness can be used for the entire width of the shoulder or tapered to 6 in. (152 mm) at the

25、 outside edge . The use of the same thickness for both mainline and shoulder pavements is not only easier to construct, especially in installing the longitudinal joint, but has the further advantages of improving drainage by the elimination of bathtub trench and reducing differential frost heave. I

26、f it is necessary to use thinner shoulder sections, for economic or other reasons , the thickness of the inner edge can be based on the encroaching and parking traffic combined, that of the outer edge on the parking traffic alone . The design method used for the mainline pavement can also be used

27、 for the shoulder, except that the traffic on the shoulder is much lighter . The following example illustrates how the PCA method can be used for determining the thickness of shoulder. In applying the PCA method t o real situations, various weights of single- and tandem-axle loads must be analyze

28、d separately,because each has a different effect on the mode of failure. However, for simplicity,only the 18-kip (80-kN) single-axle loads will be used in the example . 譯文： 剛性路面路肩設(shè)計 11.4節(jié)提出的許多關(guān)于柔性路面路肩設(shè)計的資料，也適用于剛性路面路肩設(shè)計。這里介紹剛性路面路肩與柔性路面路肩不同的一些特點。 PPC路肩用于市區(qū)高速公路已有許多年，但在60年代中才開始

29、將其用于郊區(qū)公路。由于這些路面良好的工作性能，現(xiàn)在許多部門將剛性路面采用PPC路肩作為設(shè)計標準。 有拉桿的混凝土路肩特點 混凝土路肩必須用拉桿與主車道混凝土路面相連接。有拉桿混凝土路肩的優(yōu)點如下： 1.在靠近主車道路面設(shè)置有拉桿的混凝土路肩，可大幅度增加路面的承載能力。有拉桿混凝土路肩給路面邊緣提供了支承，使主車道路面板的應(yīng)力和撓度減小。路肩也得到了主車道路面板支承的好處，因此由于侵占交通產(chǎn)生的損傷大為降低。 2.主車道和路肩的鋪面之間沒拉桿的縱縫易于封縫，減少了滲入路面結(jié)構(gòu)的表面徑流量。在佐治亞州和伊利諾伊州所作的野外研究表明，封填的縱縫使降水進入路面結(jié)構(gòu)的數(shù)量明顯減少（Dempse

30、y 等，1982）。 3.由于板邊和板角撓度減小、通過縱縫滲入的水量減少和將水排除至遠離車道之外，主車道路面板下的唧泥現(xiàn)象也減少。 4.有拉桿的混凝土路肩可減少路肩縱縫兩側(cè)的位移差，不會產(chǎn)生車道和路肩脫離的損壞，而這種損壞在柔性路面是常有的。 剛性路面路肩的類型 與主車道路面一樣，路肩的鋪面有三種類型：有接縫的普通混凝土路面（JPCP）、有接縫的鋼筋混凝土路面（JRCP）和連續(xù)配筋混凝土路面（CRCP）。通常，路肩的類型與主車道路面類型相匹配。然而，也可以有一些例外： 1.對于主車道是JPCP，由于其造價低，建議采用與主車道路面具有同樣接縫間距的JPCP路肩。若采用長接縫間距的JPC

31、P路肩，過大的接縫位移會使相鄰的主車道路面板產(chǎn)生問題。所有的橫縫都應(yīng)該保持適當?shù)木嚯x，并和主車道接縫一樣，予以填封。 2.對于主車道是JRCP，在設(shè)計中可以采用與主車道路面相匹配的JRCP路肩，或者采用接縫間距小的JPCP路肩。采用JPCP路肩較經(jīng)濟，因為不需要用鋼筋。它可以乘鋪設(shè)鋼筋的間隙與JRCP主車道路面同時鋪筑，并且在短一些的間距內(nèi)作橫向切縫。 3.對于主車道是CRCP，而在設(shè)計中為了與主車道路面相匹配，可采用CRCP路肩，或者采用接縫間距小的JPCP路肩。采用接縫間距小的JPCP路肩，可減小導(dǎo)致主車道CRCP開裂的接縫位移。JPCP路肩中不設(shè)鋼筋可節(jié)省施工費用。 路肩縱縫設(shè)計

32、 路肩縱縫處必須有合適的傳荷裝置，以減小主車道和路肩板的應(yīng)力和撓度。應(yīng)用最廣泛的是有拉桿和企口的接縫，能夠保證荷載的有效傳遞。Colley等（1978）對有企口、設(shè)有拉桿和企口、設(shè)有拉桿的平縫試驗板的傳荷情況作了研究，結(jié)論認為所有三種接縫在減小荷載產(chǎn)生的應(yīng)力和撓度方面效果相同。然而，不推薦采用無拉桿的企口縫。因為路肩接縫有可能分開，有拉桿的平縫具有優(yōu)良的工作性能，建議采用這種易于施工，并能降低費用的接縫。間距在457~610mm（18~24in），編號為NO.4或NO.5有延性的拉桿，要優(yōu)于長間距勁性大的短拉桿。這樣可極大地減小應(yīng)力集中和在拉桿附近產(chǎn)生接縫剝落的可能性。 在現(xiàn)有路面旁修筑PP

33、C路肩時，可在現(xiàn)有板邊鉆孔放置拉桿。這可以用安裝在拖拉機上的鉆孔機，一次可鉆數(shù)個孔。拉桿可以環(huán)氧樹脂或水泥漿安裝在孔中。拉桿放入孔中應(yīng)有一定的長度，保證足夠的粘結(jié)。為了防止底部碎裂，最少需要插入229mm（9in）。 對于新建工程，可將拉桿插入靠近滑模攤鋪機后面的塑性混凝土中。彎曲的鋼桿可以用人工的或機械的方法放置。隨后可將彎曲部分拉直，使路肩與主車道路面拉在一起。除了拉桿外，也可以用企口的方法增加傳荷能力。 車道與路肩之間的縱縫應(yīng)采用有效密封材料填封。最大限度地降低外來材料進入接縫導(dǎo)致接縫剝落，并減少水和除冰鹽進入接縫腐蝕拉桿的可能性。 路肩厚度設(shè)計 11.4.3節(jié)介紹的關(guān)于柔性路面

34、路肩厚度設(shè)計的概念，也適用于剛性路面路肩。一個主要的差別在于：柔性路肩由于越占交通，內(nèi)邊總是最不利，而剛性路肩由于停放交通，外邊可能最不利。還有一個問題，路肩是否需要另外設(shè)計。洛根（Lokken）于1973年對12個州的16個項目的工作情況作了考察，建議采用152mm（6in）變截面板，從縱縫處的路面厚度變至路肩外邊緣的152mm(6in)厚。史拉維斯（Slavis）于1980年同樣對這些項目作了考察，于1981年指出絕大多數(shù)工作情況很好。野外調(diào)查中發(fā)現(xiàn)值得注意的唯一缺點是有一個項目，由于拉桿保護層不當而產(chǎn)生錯臺。由于不可能將拉桿放置在152mm（6in）路肩和厚一些的主車道路面的中間，在19

35、80年的考察中，建議路肩厚度與縱縫處主車道路面板厚相等。整個路肩寬度內(nèi)采用此厚度，或者用變截面至外邊緣的152mm（6in）。主車道和路肩鋪面兩者均采用同樣厚度不僅施工方便、特別是制作縱縫，還有一個優(yōu)點是消除了存水溝，改善了排水，減少了不均勻凍脹。 如果由于經(jīng)濟或其他原因必須采用較薄的路肩截面時，內(nèi)邊緣厚度可按越占交通和停放交通綜合設(shè)計，而外邊緣只考慮停放交通。用于主車道路面的設(shè)計方法也能用于路肩設(shè)計，只是路肩上的車輛較輕。用以下例子說明如何應(yīng)用PCA法確定路肩寬度。實際應(yīng)用PCA法時，對于不同重量的單軸和雙軸荷載必須分別考慮，因其對破壞模式的影響不同。然而為了簡化起見，例題中只用了80KN（18kip）單軸荷載。