1、Section 26 METAL CULVERTS 26.1 GENERAL 26.1.1 Description This work shall consist of furnishing, fabricating, and installing metal pipe, metal structural plate pipe, arches, pipe arches, and box structures in conformance with these specifications, the special provisions, and the details shown on the
2、 plans. As used in this specification, long- span structures are metal plate horizontal ellipse, inverted pear and multiple radius arch shapes as well as special shape culverts as defined in Division I, Section 12, “Soil- Corrugated Metal Structure Interaction Systems.” The terms “metal pipe” and “m
3、etal structural plate pipe” shall include both circular pipe arch, underpass and elliptical shapes. “Metal structural plate arches” consist of a metal plate arch supported on reinforced concrete footings at its base (ends) with or without a paved invert slab. “Pipe arches” are constructed to form a
4、pipe having an arch- shaped crown and a relatively flat invert. “Metal structural plate box structures” are conduits, rectangular in cross section, constructed of metal plates. 26.2 WORKING DRAWINGS Whenever specified or requested by the Engineer, the Contractor shall provide manufacturers assembly
5、in- structions or working drawings with supporting data in sufficient detail to permit a structural review. Sufficient copies shall be furnished to meet the needs of the Engi- neer and other entities with review authority. The working drawings shall be submitted sufficiently in advance of proposed u
6、se to allow for their review, revision, if needed, and approval without delay to the work. The Contractor shall not start the construction of any metal culvert for which working drawings are required until the drawings have been approved by the Engineer. Such approval will not relieve the Contractor
7、 of responsi- bility for results obtained by use of these drawings or any of his or her other responsibilities under the contract. 26.3 MATERIALS 26.3.1 Corrugated Metal Pipe Steel pipe shall conform to the requirements of Aluminum pipe shall conform to the requirements of AASHTO M 36. AASHTO M 196.
8、 26.3.2 Structural Plate Steel structural plate shall conform to the requirements Aluminum alloy structural plate shall conform to the of AASHTO M 167. requirements of AASHTO M 219. 26.3.3 Nuts and Bolts Nuts and bolts for steel structural plate pipe, arches, pipe arches, and box structures shall co
9、nform to the re- quirements of AASHTO M 167. Nuts and bolts for alu- minum structural plate shall be aluminum conforming to ASTM F 468 or standard strength steel conforming to ASTM A 307. 26.3.4 Mixing of Materials Aluminum and steel materials shall not be mixed in any installation unless they are a
10、dequately separated or protected to avoid galvanic reactions. Hot-dip galvanizing provides such protection. Hot-dip galvanized steel and stainless steel bolts and nuts are acceptable for aluminum structural plate. 26.3.5 Fabrication Plates at longitudinal and circumferential seams shall be connected
11、 by bolts with the seams staggered so that not more than three plates come together at any one point. 659 660 HIGHWAY BRIDGES 26.3.6 26.3.6 Welding Welding of steel, if required, shall conform to the ANSI/AASHTO/AWS Bridge Welding Code DIS. All welding of steel plates, other than fittings, shall be
12、per- formed prior to galvanizing. Welding of aluminum, if required, shall conform to the AWS D1.2, “Structural Welding Code.” 26.3.7 Protective Coatings When required by the plans or the special provisions, metal pipes and structural plate shall be protected with bi- tuminous coating or have the inv
13、ert paved with bitumi- nous material. Bituminous coatings shall be applied as provided in AASHTO M 190, Type A, unless otherwise specified. Bituminous pavings, if required, shall be ap- plied over the bituminous coatings to the inside bottom portion of pipe as provided in AASHTO M 190, Type C, unles
14、s otherwise specified. The portion of all nuts and bolts used for assembly of coated structural plate project- ing outside the pipe, shall be coated after installation. The portions of the nuts and bolts projecting inside the pipe need not be coated. Polymeric coatings, when called for on the plans
15、or in the special provisions, shall conform to the requirements of AASHTO M 246. The polymeric coating shall be ap- plied to the galvanized sheet prior to corrugating and, un- less otherwise specified, the thickness shall be not less than 0.010 inch. Any pinholes, blisters, cracks, or lack of bond s
16、hall be cause for rejection. Polymeric coatings will not be permitted on structural plate pipes. 26.3.8 Bedding and Backfill Materials 26.3.8.1 General Bedding material shall be loose native or granular ma- terial with a maximum particle or clump) size not to ex- ceed one-half the corrugation depth.
17、 Backfill for metal culverts shall be granular material as specified in the plans and specifications and shall be free of organic material, stones larger than 3 inches in the greatest dimension, frozen lumps, or moisture in excess of that permitting thorough compaction. As a minimum, backfill materi
18、als shall meet the requirements of AASHTO M 145 for A-1, A-2. or A-3. 26.3.8.2 Long-Span Structures Bedding and backfill materials shall meet the general requirements of Article 26.3.8.1. As a minimum backfill materials for structures with less than 12 feet of cover shall meet the requirements of AA
19、SHTO M 145 for A-1, A-2-4, A-2-5, or A-3. Minimum backfill requirements for stnic- tures with 12.0 feet or more cover shall meet AASHTO M 145 requirements for A-1 or A-3. 26.3.8.3 Box Culverts Bedding and backfill materials shall meet the general requirements of Article 26.3.8.1. As a minimum, backf
20、ill shall meet the requirements of AASHTO M 145 for A- 1, A-2-4, A-2-5, or A-3. 26.4 ASSEMBLY 26.4.1 General Corrugated metal pipe and structural plate pipe shall be assembled in accordance with the manufacturers instruc- tions. All pipe shall be unloaded and handled with rea- sonable care. Pipe or
21、plates shall not be rolled or dragged over gravel or rock and shall be prevented from striking rock or other hard objects during placement in trench or on bedding. Corrugated metal pipe shall be placed in the bed start- ing at the downstream end. Pipes with circumferential seams shall be installed w
22、ith their inside circumferential sheet laps pointing downstream. Bituminous coated pipe, polymer coated pipe, and paved invert pipe shall be installed in a similar manner to corrugated metal pipe with special care in handling to avoid damage to coatings. Paved invert pipe shall be in- stalled with t
23、he invert pavement placed and centered on the bottom. Structural plate shall be assembled and installed in ac- cordance with the plans and detailed erection instructions. Copies of the manufacturers assembly instructions shall be furnished as specified in Article 26.2. Bolted longitu- dinal seams sh
24、all be well fitted with the lapping plates parallel to each other. The applied bolt torque for %inch diameter high-strength steel bolts (A 449) for the assem- bly of steel structural plate shall be a minimum of 100 ft- lbs and a maximum of 300 ft-lbs. Aluminum structural plate shall be assembled usi
25、ng Ya-inch diameter aluminum bolts (F 468) or standard strength steel bolts (A 307) which shall be torqued to a minimum of 100 ft-lbs and a maximum of 150 ft-lbs. When seam sealant tape or a shop applied asphalt coating is used, bolts should be retight- ened no more than once. Generally, retightenin
26、g is done within 24 hours. There is no structural requirement for residual torque; the important factor is the seam fit-up. 26.4.2 Joints Joints for corrugated metal culvert and drainage pipe shall meet the following performance requirements. 26.4.2.1 DIVISION II-CONSTRUCTION 66 1 26.4.2.1 Field Joi
27、nts Transverse field joints shall be of such design that the successive connection of pipe sections will form a con- tinuous line free from appreciable irregularities in the flow line. In addition, the joints shall meet the general per- formance requirements described in Articles 26.4.2.2 and 26.4.2
28、.3. Suitable transverse field joints, which satisfy the requirements for one or more of the subsequently defined joint performance categories can be obtained with the fol- lowing types of connecting bands furnished with the suit- able band-end fastening devices: (a) Corrugated bands. (b) Bands with
29、projections. (c) Flat bands. (d) Bands of special design that engage factory re- formed ends of corrugated pipe. (e) Other equally effective types of field joints may be used with the approval of the Engineer. 26.4.2.2 Joint Types Applications may require either “Standard” or “Spe- cial joints. Stan
30、dard joints are for pipe not subject to large soil movements or disjointing forces; these joints are satisfactory for ordinary installations, where simple slip type joints are typically used. Special joints are for more adverse requirements such as the need to withstand soil movements or resist disj
31、ointing forces. Special designs must be considered for unusual conditions as in poor foundation conditions. Downdrain joints are required to resist longitudinal hydraulic forces. Examples of this are steep slopes and sharp curves. 26.4.2.3 Soil Conditions (a) The requirements of the joints are depen
32、dent on the soil conditions at the construction site. Pipe backfill which is not subject to piping action is classified as “nonerodi- ble.” Such backfill typically includes granular soil (with grain sizes equivalent to coarse sand, small gravel, or larger) and cohesive clays. (b) Backfill that is su
33、bject to piping action, and would tend to either infiltrate the pipe or to be easily washed by exfiltration of water from the pipe, is classified as “Erodi- ble. Such backfill typically includes fine sands and silts. (c) Special joints are required when poor soil conditions are encountered such as w
34、hen the backfill or foundation material is characterized by large soft spots or voids. If construction in such soil is unavoidable, this condition can only be tolerated for relatively low fill heights, because the pipe must span the soft spots and support imposed loads. Backfills of organic silt, wh
35、ich are typically semi-fluid dur- ing installation, are included in this classification. 26.4.2.4 Joint Properties The requirements for joint properties are divided into the six categories given on Table 26.4. Properties are de- fined and requirements are given in the following para- graphs (a) thro
36、ugh (0. The values for various types of pipe can be determined by a rational analysis or a suitable test. (a) Shear Strength-The shear strength required of the joint is expressed as a percent of the calculated shear strength of the pipe on a transverse cross-section remote from the joint. (b) Moment
37、 Strength-The moment strength required of the joint is expressed as a percent of the calculated mo- TABLE 26.4 Categories of Pipe Joints Soil Condition Nonerodible Erodible Joint Qpe Joint Type Standard Special Standard Special Downdrain Shear 2% 5% 2% 5% 2% Moment” 5% 15% 5% 15% 15% Tensile O in. -
38、42 in. dia. O 5,000 lbs - 5,000 lbs 5,000 lbs 48 k-84 in. dia. - 10,000 Ibs - 10,OOO Ibs 10,OOO Ibs Joint Overlapb (min.) 10-1/2 in. NA 10-1/2 in. NA NA Soiltightness NA NA 0.3 or 0.2 0.3 or 0.2 0.3 or 0.2 Watertightness See Article 26.4.2.4(f) “Article 26.4.2.4(b). bAlternate requirement. See Artic
39、le 26.4.2.4(e). Structurai plate pipe, pipe-arches, and arches shall be installed in accordance with the plans and detailed erection instructions. Minimum ratio of Der soil size to size of opening 0.3 for medium to fine sand and 0.2 for uniform sand. 662 HIGHWAY BRIDGES 26.2.4 ment capacity of the p
40、ipe on a transverse cross section re- mote from the joint. (c) Tensile Strength-Tensile strength is required in a joint when the possibility exists that a longitudinal load could develop which would tend to separate adjacent pipe sections. (d) Joint Overlap-Standard joints which do not meet the mome
41、nt strength alternatively shall have a minimum sleeve width overlapping the abutting pipes. The mini- mum total sleeve width shall be as given in Table 26.4. Any joint meeting the requirements for a special joint may be used in lieu of a standard joint. (e) Soiltightness-Soiltightness refers to open
42、ings in the joint through which soil may infiltrate. Soil tightness is influenced by the size of the opening (maximum di- mension normal to the direction that the soil may infil- trate) and the length of the channel (length of the path along which the soil may infiltrate). No opening may ex- ceed 1
43、inch. In addition, for all categories, if the size of the opening exceeds y8 inch, the length of the channel must be at least four times the size of the opening. Fur- thermore, for nonerodible or erodible soils, the ratio of Dss soil size to size of opening must be greater than 0.3 for medium to fin
44、e sand or 0.2 for uniform sand; these ratios need not be met for cohesive backfills where the plastic- ity index exceeds 12. As a general guideline, a backfill material containing a high percentage of fine grained soils requires investigation for the specific type of joint to be used to guard agains
45、t soil infiltration. Alternatively, if a joint demonstrates its ability to pass a 2-psi hydrostatic test without leakage, it will be considered soil tight. NOTE: Joints that do not meet these requirements may be made soil tight by wrapping with a suitable geotextile. (f) Watertightness-Watertightnes
46、s may be specified for joints of any category where needed to satisfy other criteria. The leakage rate shall be measured with the pipe in place or at an approved test facility. The adjoining pipe ends in any joint shall not vary more than 0.5 inch in di- ameter or more than 1.5 inches in circumferen
47、ce for wa- tertight joints. These tolerances may be attained by proper production controls or by match-marking pipe ends. 26.4.3 Assembly of Long-Span Structures Long-span structures may require deviation from the normal good practice of loose bolt assembly. Unless held in shape by cables, struts, o
48、r backfill, longitudinal seams should be tightened when the plates are hung. Care must be taken to align plates to ensure properly fitted seams prior to bolt tightening. This may require temporary shoring. Follow the manufacturers instructions. The vari- ation before backfill shall not exceed 2% of
49、the span or rise, whichever is greater, but shall not exceed 5 inches except for horizontal ellipse shapes having a ratio of top to side radii of 3 or less where only the 2% restriction shall apply. The rise of arches with a ratio of top to side radii of three or more should not deviate from the specified di- mensions by more than 1% of the span. Reinforcing ribs, when required to satisfy the structural design, shall be attached to the structural plate corrugation crown prior to backfilling using a bolt spacing of not more than 12 inches. Legible identifying letters or numbers shall
