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1、外文资料DESIGN OF RIGID PAVEMENT SHOULDERSMost 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 t sh
2、oulders 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 .Advanta
3、ges of Tied Concrete ShouldersConcrete 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 cansubstantially increase the load-carrying capacity of the pavement
4、. The tied concreteshoulder 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 tied longitudinal joi
5、nt between mainline and shoulder pavements can be easilysealed 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 rainfall into the pave
6、ment structure (Dempsey et al., 1982).3. Pumping beneath the mainline slab is reduced through the reduction of edge an dcorner deflections, the reduction of water infiltration through the longitudinal joint, and the draining of water far away from the traffic lane .4. Tied concrete shoulders can red
7、uce differential movements at the longitudinalshoulder joint and do not experience the lane/shoulder dropoff type of distress that occurs so frequently in flexible shoulders .Types of Rigid Pavement ShouldersAs with mainline pavements, three types of shoulder pavements are available : jointed plain
8、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, only JPCP shoulders with the same
9、joint spacings as themainline pavement are recommended, because of their low cost . If JRCP shoulderswith longer joint spacings are used, the excessive joint movements may cause problems in the adjacent mainline slabs . All transverse joints should b eprovided with an adequate reservoir and sealed s
10、imilarly 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 JPCPshoulders is more cost effective, because no steel reinforcement is needed . They can be placed at the same
11、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 may be used . The use of shortjoint spacing f
12、or JPCP shoulders will reduce potential movements of the joints that might cause cracking in the mainline CRCP. The elimination of steel reinforcementin the JPCP shoulders can save construction cost .Design of Longitudinal Shoulder JointAdequate load transfer across the longitudinal shoulder joint m
13、ust be provided to re -duce the stresses and deflections in both mainline and shoulder slabs . Tied and keyedjoints have been used most frequently to ensure a high degree of load transfer . Colleyet al. (1978) investigated load transfers in laboratory slabs constructed with keyed, tied and keyed, an
14、d 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 separation . The excellent performance of the tied butt joint s
15、uggests that this type o fconstruction is feasible and can reduce costs . Malleable tiebars of No. 4 or No. 5 sizespaced at 18 to 24 in . (457 to 610 mm) are preferable to stiffer short bars spaced at larger intervals. This will substantially reduce stress concentration and the possibility of joint
16、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 bedone by using a tractor-mounted drill that can drill several holes at one time . Tiebarsare installed i
17、n the holes by using epoxy or cement grout . The bar should be inserte dinto 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 the case of new construction, tiebars can be inserted into the plastic conc
18、retenear 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 keyway can be formed to provide additional load transfer capability.The longitudi
19、nal 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 to cause joint spall and reduce the amount of water and deicing salts entering in
20、to the joint and corroding the tiebars .Shoulder Thickness DesignThe thickness design concepts presented in Section 11 .4 .3 for flexible pavement shoulders are also applicable to rigid pavement shoulders . One major difference is that the inner edge is always more critical for flexible shoulders, b
21、ecause 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 (1973) reviewed the performance of 16 projects located in 12 states and recommended
22、 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 performance review of these same projects in 1980 and indicated that the vast majori
23、ty 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 middepth both of a 6-in. (152-mm) shoulder and of a thicker mainline pavement ,so it was
24、 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 outside edge . The use of the same thickness for both mainline and shoulder pavemen
25、ts 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.If it is necessary to use thinner shoulder sections, for economic or other reasons ,the
26、 thickness of the inner edge can be based on the encroaching and parking trafficcombined, that of the outer edge on the parking traffic alone . The design method usedfor the mainline pavement can also be used for the shoulder, except that the traffic onthe shoulder is much lighter . The following ex
27、ample illustrates how the PCA methodcan be used for determining the thickness of shoulder. In applying the PCA method t oreal situations, various weights of single- and tandem-axle loads must be analyzed separately,because each has a different effect on the mode of failure. However, for simplicity,o
28、nly the 18-kip (80-kN) single-axle loads will be used in the example .译文：刚性路面路肩设计11.4节提出的许多关于柔性路面路肩设计的资料，也适用于刚性路面路肩设计。这里介绍刚性路面路肩与柔性路面路肩不同的一些特点。PPC路肩用于市区高速公路已有许多年，但在60年代中才开始将其用于郊区公路。由于这些路面良好的工作性能，现在许多部门将刚性路面采用PPC路肩作为设计标准。有拉杆的混凝土路肩特点混凝土路肩必须用拉杆与主车道混凝土路面相连接。有拉杆混凝土路肩的优点如下：1.在靠近主车道路面设置有拉杆的混凝土路肩，可大幅度增加路面的承
29、载能力。有拉杆混凝土路肩给路面边缘提供了支承，使主车道路面板的应力和挠度减小。路肩也得到了主车道路面板支承的好处，因此由于侵占交通产生的损伤大为降低。2.主车道和路肩的铺面之间没拉杆的纵缝易于封缝，减少了渗入路面结构的表面径流量。在佐治亚州和伊利诺伊州所作的野外研究表明，封填的纵缝使降水进入路面结构的数量明显减少（Dempsey 等，1982）。3.由于板边和板角挠度减小、通过纵缝渗入的水量减少和将水排除至远离车道之外，主车道路面板下的唧泥现象也减少。4.有拉杆的混凝土路肩可减少路肩纵缝两侧的位移差，不会产生车道和路肩脱离的损坏，而这种损坏在柔性路面是常有的。刚性路面路肩的类型与主车道路面一样
30、，路肩的铺面有三种类型：有接缝的普通混凝土路面（JPCP）、有接缝的钢筋混凝土路面（JRCP）和连续配筋混凝土路面（CRCP）。通常，路肩的类型与主车道路面类型相匹配。然而，也可以有一些例外：1.对于主车道是JPCP，由于其造价低，建议采用与主车道路面具有同样接缝间距的JPCP路肩。若采用长接缝间距的JPCP路肩，过大的接缝位移会使相邻的主车道路面板产生问题。所有的横缝都应该保持适当的距离，并和主车道接缝一样，予以填封。2.对于主车道是JRCP，在设计中可以采用与主车道路面相匹配的JRCP路肩，或者采用接缝间距小的JPCP路肩。采用JPCP路肩较经济，因为不需要用钢筋。它可以乘铺设钢筋的间隙与
31、JRCP主车道路面同时铺筑，并且在短一些的间距内作横向切缝。3.对于主车道是CRCP，而在设计中为了与主车道路面相匹配，可采用CRCP路肩，或者采用接缝间距小的JPCP路肩。采用接缝间距小的JPCP路肩，可减小导致主车道CRCP开裂的接缝位移。JPCP路肩中不设钢筋可节省施工费用。路肩纵缝设计路肩纵缝处必须有合适的传荷装置，以减小主车道和路肩板的应力和挠度。应用最广泛的是有拉杆和企口的接缝，能够保证荷载的有效传递。Colley等（1978）对有企口、设有拉杆和企口、设有拉杆的平缝试验板的传荷情况作了研究，结论认为所有三种接缝在减小荷载产生的应力和挠度方面效果相同。然而，不推荐采用无拉杆的企口缝
32、。因为路肩接缝有可能分开，有拉杆的平缝具有优良的工作性能，建议采用这种易于施工，并能降低费用的接缝。间距在457610mm（1824in），编号为NO.4或NO.5有延性的拉杆，要优于长间距劲性大的短拉杆。这样可极大地减小应力集中和在拉杆附近产生接缝剥落的可能性。在现有路面旁修筑PPC路肩时，可在现有板边钻孔放置拉杆。这可以用安装在拖拉机上的钻孔机，一次可钻数个孔。拉杆可以环氧树脂或水泥浆安装在孔中。拉杆放入孔中应有一定的长度，保证足够的粘结。为了防止底部碎裂，最少需要插入229mm（9in）。对于新建工程，可将拉杆插入靠近滑模摊铺机后面的塑性混凝土中。弯曲的钢杆可以用人工的或机械的方法放置。
33、随后可将弯曲部分拉直，使路肩与主车道路面拉在一起。除了拉杆外，也可以用企口的方法增加传荷能力。车道与路肩之间的纵缝应采用有效密封材料填封。最大限度地降低外来材料进入接缝导致接缝剥落，并减少水和除冰盐进入接缝腐蚀拉杆的可能性。路肩厚度设计11.4.3节介绍的关于柔性路面路肩厚度设计的概念，也适用于刚性路面路肩。一个主要的差别在于：柔性路肩由于越占交通，内边总是最不利，而刚性路肩由于停放交通，外边可能最不利。还有一个问题，路肩是否需要另外设计。洛根（Lokken）于1973年对12个州的16个项目的工作情况作了考察，建议采用152mm（6in）变截面板，从纵缝处的路面厚度变至路肩外边缘的152mm
34、(6in)厚。史拉维斯（Slavis）于1980年同样对这些项目作了考察，于1981年指出绝大多数工作情况很好。野外调查中发现值得注意的唯一缺点是有一个项目，由于拉杆保护层不当而产生错台。由于不可能将拉杆放置在152mm（6in）路肩和厚一些的主车道路面的中间，在1980年的考察中，建议路肩厚度与纵缝处主车道路面板厚相等。整个路肩宽度内采用此厚度，或者用变截面至外边缘的152mm（6in）。主车道和路肩铺面两者均采用同样厚度不仅施工方便、特别是制作纵缝，还有一个优点是消除了存水沟，改善了排水，减少了不均匀冻胀。待添加的隐藏文字内容3如果由于经济或其他原因必须采用较薄的路肩截面时，内边缘厚度可按越占交通和停放交通综合设计，而外边缘只考虑停放交通。用于主车道路面的设计方法也能用于路肩设计，只是路肩上的车辆较轻。用以下例子说明如何应用PCA法确定路肩宽度。实际应用PCA法时，对于不同重量的单轴和双轴荷载必须分别考虑，因其对破坏模式的影响不同。然而为了简化起见，例题中只用了80KN（18kip）单轴荷载。
