Proposed AASHTO Structural Design Properties for Corrugated Polypropylene Storm Sewer Pipe

Transcription

1 0 0 Proposed AASHTO Structural Design Properties for Corrugated Polypropylene Storm Sewer Pipe Corresponding Author: Brent J. Bass, Simpson Gumpertz & Heger Inc., Seyon St., Building, Suite 00, Waltham, MA 0, phone:.0., fax:.0.00, bjbass@sgh.com Bill R. VanHoose, Advanced Drainage Systems Inc., 0 Trueman Blvd. Hilliard, OH 0, phone:.., fax:.., bill.vanhoose@ads-pipe.com Timothy J. McGrath, Simpson Gumpertz & Heger Inc., Seyon St., Building, Suite 00, Waltham, MA 0, phone:.0.0, fax:.0.00, tjmcgrath@sgh.com Submission Date: August 0 Word Count:, Figure Count: Table Count: Total Equivalent Word Count:,

2 0 0 Abstract Corrugated polypropylene (PP) storm sewer pipe has been available in the US market since 00. The manufacturing process and structural design basis are similar to the more widely used high density polyethylene (HDPE) pipe; however PP has advantages over HDPE in applications requiring higher bending resistance and longitudinal beam strength, greater stress crack resistance, and higher operating temperatures. In 0, both the American Society for Testing and Materials (ASTM) and the American Association of State Highway Transportation Officials (AASHTO) adopted corrugated PP pipe material and product specifications for use in non-pressure surface and sub-surface drainage applications. These standards include some requirements for PP material properties related to structural design such as minimum initial modulus and long-term creep modulus, but they do not address all parameters required by AASHTO for structural design of thermoplastic pipe. This paper presents the test methods and sampling conventions required to arrive at structural design properties, presents results of these tests on four candidate PP resins commercially available in the US, and uses these test results as the basis for proposed structural design properties for adoption into the AASHTO Load and Resistance Factor Bridge Design Specifications for the structural design of PP storm sewer pipe.

3 Corrugated high density polyethylene (HDPE) pipe was first commercially introduced in the US in and has gained wide acceptance in surface and subsurface storm water drainage applications. From the original four inch diameter pipe for agricultural drainage applications to sixty inch diameter corrugated pipes produced today, profile wall HDPE has proven to be a durable material for use in many markets. While corrugated HDPE pipes continue to gain acceptance in sewerage and drainage applications, there remains a need for alternate materials in some applications. For example, applications requiring higher bending resistance, thermal stability, and/or higher stress crack resistance may be better suited with a material engineered for this need. The authors began internal research in 000 to consider polypropylene (PP) as an alternate material for corrugated pipe production. PP is a material generally offering a higher modulus of elasticity, resulting in a higher bending resistance and longitudinal beam strength, a higher melt strength, which, under the right conditions, can allow for higher operating temperatures, and inherently higher stress crack resistance than HDPE (). With processing parameters similar to HDPE, PP is readily adaptable to North American corrugated thermoplastic pipe manufacturing techniques and equipment. In 00, the first corrugated PP pipe was commercially sold in the US and has since continued to gain market acceptance in North America. In 00 American Society for Testing and Materials (ASTM) specifications were developed for corrugated PP pipe for use in non-pressure sanitary sewer applications. In 0, both ASTM and the American Association of State Highway Transportation Officials (AASHTO) adopted corrugated PP pipe material and product specifications for use in non-pressure surface and sub-surface drainage applications. While new to the North American pipe market, corrugated polypropylene homo-polymer (PP-h) pipes have been used in Europe since, with polypropylene block copolymer (PP-b) pipes in use since the mid to late 0s (). PP-b resins, including all candidate resins below, allow for the addition of impact modifiers, important in thin-walled corrugated pipes which have a higher likelihood of cracking from impact compared to solid wall thermoplastic pipe. Thermoplastic materials, including HDPE, polyvinyl chloride (PVC), and PP, have duration-dependent response to external loading. The two main forms of loading for these gravity-fed culvert pipes are shortterm loads (e.g. live loads) and long-term loads (e.g. soil and ground water). Existing AASHTO thermoplastic pipe design methods for HDPE and PVC culvert pipe in Section. of the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications (AASHTO LRFD, ), address the load-duration-dependent response in the service and strength limit states by separating the calculations into short- and long-term components, then summing the resulting deflections or strains and comparing the sums to defined deflection or strain limits. Design requirements for the service and strength limit states include checks for total deflection, thrust (compression in the circumferential direction), buckling, and combined thrust and bending. Minimum time-dependent material properties and strain limits for the structural design of HDPE and PVC culvert pipes are found in AASHTO LRFD Table...-. The required properties are: Initial modulus, Initial strength, Long-term creep modulus, Long-term strength, Service long-term tension strain limit, and

4 Factored long-term compression strain limit There is also a minimum cell classification requirement for different HDPE and PVC resins. Previous work by VanHoose and Biesenberger () presented a variety of test results on twelve resins under consideration for PP pipe production and arrived at preliminary recommended structural design properties addressing some of the AASHTO requirements identified above: initial tensile strength of,00 psi, initial modulus of elasticity of,000 psi, 00 year tensile strength of,000 psi, and 00 year creep modulus of,000 psi. The VanHoose and Biesenberger recommendations led to ASTM and AASHTO material and product standards. The provisional AASHTO material standard for PP Pipe, MP - (), includes some requirements for material properties related to structural design, such as minimum initial modulus and long-term creep modulus, but it does not address all parameters required by AASHTO LRFD for structural design of thermoplastic pipe. Based on the VanHoose and Biesenberger recommendations, the twelve resins were reduced to four candidates which are PP extrusion-grade resins readily available in the US and are referred to here as Candidate A, B, C, and D resins. This paper builds on the VanHoose and Biesenberger work by presenting the test methods and sampling conventions required to arrive at structural design properties, presents the results of these tests for the four candidate resins described above, and uses the test results as the basis for proposed structural design properties for inclusion in AASHTO LRFD Table...- for corrugated PP storm sewer pipe. CELL CLASSIFICAION Cell class specification alone is not sufficient to fully identify suitable resin properties for pipe production. Cell classifications for PP pipe resins are not defined in MP -. This specification has material requirements more tailored to pipe production than the AASHTO standards for HDPE or PVC pipe which rely on general cell classifications to set many material properties (for example, AASHTO M for corrugated HDPE () or AASHTO M 0 for profile PVC ()). Thus, for PP storm sewer pipe resin it is proposed to rely on the requirements of MP - and not require a minimum cell class. INITIAL PROPERTIES Initial Modulus As described above, the AASTHO thermoplastic pipe design method separates demands into short- and long-term components. Short-term demands and some failure mode capacities for the service and strength limit states are evaluated using short-term material properties such as initial modulus and initial strength. VanHoose and Biesenberger recommended, and AASHTO MP - requires, the PP resin have a minimum initial modulus of,000 psi and a minimum initial strength of,00 psi. Initial modulus is used to determine short-term (live) load deflections and strain demand in AASHTO LRFD Articles... and...0.c, respectively. It is also used for handling and installation requirements in terms of the flexibility factor in Article... and for global buckling resistance in Article...0.e.

5 0 AASHTO MP - requires the initial modulus for PP pipes to be determined as the % secant flexural modulus in accordance with ASTM D0 (), the same method used to determine the initial modulus of HDPE pipes (AASHTO LRFD Table...-). In general, most short term material properties such as flexural modulus are provided for the base virgin PP resin by the resin supplier on a certificate of analysis (COA). To further validate these results and account for the effect of additives, colorants, UV inhibitors, and stabilizers, flexural modulus should be evaluated routinely on specimens made from compounded resin and occasionally verified with specimens made from the finished product. Specimens from finished pipe are made by grinding up plastic from the pipe wall and compression molding it into a plaque in accordance with ASTM D0 (). Results for initial modulus testing on ten compounded resin specimens from Candidate A resin are compared in Figure with the target minimum value. 0 FIGURE Initial modulus test results for Candidate A PP resins. The individual test results for this resin were consistent with the manufacturer s COA % minimum secant flexural modulus of 0,000 psi and meet the recommended initial modulus of,000 psi. Each of the compounded candidate resins tested resulted in a slightly higher flexural modulus compared to the virgin resin. This may be partly due to an increase in crystallization of the PP molecules from the colorant, emphasizing the need to evaluate compounded resins. Initial Strength Initial strength is determined from tension tests in accordance with ASTM D (). This property is important for the pipe s resistance to stresses from handling, shipping, and installation and is used as a resin acceptance criterion at the pipe manufacturing plant prior to accepting resin from the supplier. Initial strength can be used for design in accordance with AASHTO LRFD Article...0.b if determining effective area from stub compression test data instead of through theoretical effective area calculations.

6 Ultimate short term tensile strength for the virgin resin can be obtained from the resin supplier s COA, but as with initial modulus, it should also determined from the compounded resin including all additives and stabilizers. Results for initial strength testing on ten compounded specimens of Candidate A resin are shown in Figure. 0 0 FIGURE Initial strength test results for Candidate A PP resin. Individual test results in Figure were consistent with manufacturer s COA ultimate tensile strength value of,00 psi. As with flexural modulus, each candidate resin showed a slightly higher value for the compounded resin when compared to the virgin resin. However the ultimate strains were slightly less than the value reported in the COA. Due to the relationships between strength, modulus, and ultimate strain, for a given material strength, if the initial modulus is higher than listed on the COA, the ultimate strain will be lower. This further emphasizes the need to fully characterize the properties for a particular resin and not to rely on COA values in design. All test results meet the recommended initial strength value of,00 psi proposed by VanHoose and Biesenberger and required by AASHTO MP -, which is proposed as the design value for initial strength for PP in AASHTO LRFD Section.. LONG-TERM PROPERTIES One of the most important aspects of designing with thermoplastics is to account for thermoplastic creep by accurately estimating the material properties for the entire design life of the structure, here 0,, or 00 years. Long-term demands and some failure mode capacities are evaluated using long-term material properties such as long-term modulus of elasticity (here referred to as a creep modulus) and long-term strength. AASHTO MP - requires a minimum year modulus of elasticity of,000 psi and year strength of,000 psi.

7 0 0 Creep Modulus The long-term thermoplastic creep modulus is used to determine long-term deflections in AASHTO LRFD Article... In the strength limit state, it is used to determine long-term soil load demand on the pipe through the vertical arching factor in AASHTO LRFD Article..., long-term strain demand in Article...0.c, and the pipe s resistance to global buckling in Article...0.e. Assuming the thermoplastic has adequate stress crack resistance and antioxidant capacity, the material is undergoing ductile deformation for the majority of its life and has not progressed into the brittle/stress cracking phase or material degradation phase. Stress cracking would occur under sustained tension; when the pipe is installed properly, the primary design condition is for axial compression and there is typically no net tension in the pipe wall, therefore stress cracking should not be a concern. During the ductile deformation phase, thermoplastic creep typically occurs in three stages (Figure ): Primary, Secondary, and Tertiary as discussed in Appendix X of ASTM D0 (0). Primary (Stage I) creep occurs over the initial stages of loading and results in some relaxation of the material, but with the creep rate decreasing with time. Secondary (Stage II) creep is during the middle stage of loading with the creep rate reaching a steady state. Tertiary (Stage III) creep occurs when the creep rate increases rapidly and the material heads toward fracture. Material creep tests are used to determine the material response during the secondary creep phase, and the resulting material properties are used to design for this behavior. FIGURE Typical thermoplastic creep response curve. (Reference: ASTM D 0) Traditionally for HDPE and PVC pipe design there has been no requirement to determine the material s actual long-term creep modulus (,, ). As discussed in the commentary to AASHTO LRFD Article..., no product standard for HDPE or PVC pipe requires determination of the actual longterm properties, however relaxation test data for HDPE and PVC from parallel plate tests performed over two years shows the modulus of elasticity reduces approximately linearly with the logarithm of time and that the values in AASHTO LRFD Table...- are reasonably conservative.

8 The thermoplastic creep modulus can be determined through a creep modulus test in accordance with ASTM D0 for up to 0,000 hours and then extrapolated to 0,, or 00 years, with the results able to be compared to the values in AASHTO LRFD Table...- on a logarithmic time scale. In this method, a series of at least five tension tests are performed at different stress levels selected in even increments up to 00 psi, which is the approximate service-level long-term stress magnitude in the pipe wall. Specimens for creep modulus tests are typically made from virgin resin, however results should be verified with results from specimens cut from plaques made from compounded pipe wall resin, or taken directly from the pipe wall where dimensionally practical. As discussed above, a low amount of additives will typically result in a higher creep modulus than that of virgin resin. For this reason, a more conservative creep modulus (a lower modulus for long-term creep) will likely be obtained from plaques made from virgin resin. Once testing is conducted at various stresses or temperatures, the Boltzmann superposition principle () is used to shift data and generate a master curve. Estimations of long-term creep behavior and mechanical properties for design can then be made. One of the drawbacks of this test is that for evaluation of every new resin, a new 0,000 hour test must be undertaken at the five different stress levels. If an approved resin is in short supply requiring the use of a different supplier, the new resin could not be evaluated in less than 0,000 hours, or would have to have been previously evaluated. Also, this lengthy test cannot be used to reevaluate a resin with simplicity; if a resin supplier changes blends, there is no efficient method to reevaluate long-term behavior. This leads to the desire of a more efficient, shorter-term test. In 00 (), the geosynthetic community first published ASTM D (), a standard test method for determining accelerated tensile rupture and creep behavior of geosynthetic materials. This method uses a series of constant stress tensile tests at elevated temperatures and superimposes the results to determine material properties for the product life using time-temperature superposition methods. The test method is commonly referred to as the SIM test, referring to the stepped isothermal method used for timetemperature superposition. For pipe, the constant stress is 00 psi, similar to the traditional 0,000 hour creep test, which is the approximate magnitude of service level stresses expected in buried thermoplastic pipe. This test method is referenced in AASHTO MP - and allowed as an alternative to ASTM D0, and has been used to qualify material for and in the design of PP thermoplastic stormwater retention chambers for about ten years in accordance with ASTM F (). Results from the ASTM D test must be validated with traditional creep test results for a given material prior to relying on results from the SIM test alone. After validation, the SIM test may be used to efficiently evaluate the long-term effects of changes in resin or resin blends. This validation work has been performed on Candidate D resin at a stress level of 00 psi, with the traditional creep test results (Figure a) compared to the SIM test results (Figure b).

9 0 (a) Traditional 0,000 hr Creep test results. (b) SIM Creep test results. FIGURE Comparison of traditional creep data to SIM test creep data for Candidate D resin. Results in Figure show the traditional 0,000 hour creep test had a 0,000 hour creep modulus of about,000 psi compared to the SIM test results with an average 0,000 hour creep modulus of about,000 psi for three specimens. This data shows less than % difference in results between the two methods at 0,000 hours thereby validating the SIM test as an acceptable method for predicting ductile long-term creep behavior of PP pipe resins. SIM tests have been conducted on all four candidate resins with the results shown in Figure. FIGURE 00 psi SIM test creep modulus results for four candidate resins. The minimum creep modulus shown in Figure for 0,, and 00 year design lives are, psi,, psi, and, psi, respectively. All data in Figure exceeds the minimum requirements for longterm creep modulus in AASHTO MP -, and is in line with the 00 year creep modulus of,000 psi proposed by VanHoose and Biesenberger. From the above test data and VanHoose and Biesenberger recommendations, the proposed minimum creep modulus requirements for the PP thermoplastic pipe

10 0 0 0 design in AASHTO LRFD Section. are,000 psi,,000 psi, and,000 psi for 0 year, year, and 00 year design lives, respectively. Long-Term Strength Traditional creep rupture tests and SIM tests can both be used to determine long-term tensile strength. Long-term strength is used indirectly in the design when estimating the effective area from stub compression test data, an alternative to the theoretical calculations for effective area, as discussed in AASHTO LRFD Article...0.b, and for assurance that the pipe can resist the long-term tensile stresses present in the pipe wall for the life of the installation. The SIM test can be used to evaluate the thermoplastic s ultimate tensile strength in two ways: (a) by developing a rupture envelope for the material by performing SIM tests at a variety of stress levels, or (b) by performing a constant stress SIM test to show the material would not rupture when subjected to that stress for the product design life. The former approach would be used to evaluate design properties of candidate resins while the latter approach would be used as a QA test on resins for production. For the first method, a series of SIM tests are performed at several different stress levels until rupture and the rupture stress versus time is plotted in a rupture envelope as shown for Candidate A resin in Figure. A similar rupture envelop can be developed using ASTM D0 where time to rupture for specimens tested at various stress levels is plotted versus the actual applied stress to develop a master curve. From the master stress rupture curve, rupture time can be extrapolated at the known design stress. FIGURE SIM test rupture envelope for Candidate A resin. Figure demonstrates that Candidate A resin has 0,, and 00 year rupture strengths of, psi,, psi, and, psi, respectively.

11 0 A second means of demonstrating long-term strength using the SIM test is to perform a SIM test at a constant stress level to determine the times to the onset of tertiary creep or rupture under the sustained stress. If there is no tertiary creep or rupture during the test for the design life of the pipe, the test demonstrates a rupture strength greater than the test stress at its design life. This method does not arrive at a specific rupture strength for the resin but can qualify a particular resin as exceeding a minimum rupture strength. A,000 psi SIM test strain versus time curve is shown in Figure for Candidate A resin with a log-time scale on the x-axis. The results show that the specimen has not experienced tertiary creep (i.e. there is no rapid increase in strain with time) and the specimen has not ruptured, thus demonstrating the resin has a rupture strength greater than,000 psi for over 00 years. Strains at an estimated 00 years under a constant stress of,000 psi from SIM test rupture envelopes are shown for all four candidate resins in Table. 0 FIGURE PP Candidate A resin,000 psi SIM test strain vs. time curve. TABLE 00-year PP creep strain at,000 psi. Candidate Resin 00-Year Creep Strain (%) A.0 B.0 C. D. The four candidate resins demonstrate greater than,000 psi long-term creep strength through SIM testing. AASHTO MP - has a required minimum year creep strength of,000 psi. VanHoose and Biesenberger recommended a minimum 00 year creep strength of,000 psi. From the requirements of MP -, work by VanHoose and Biesenberger, and the test results presented here, a minimum longterm (0 year, year, and 00 year) rupture strength of,000 psi is proposed for PP thermoplastic pipe design in AASHTO LRFD Section..

12 0 0 0 STRAIN LIMITS Service Long-Term Strain Limit The SIM test data can be used to determine the service long-term tension strain limit, used in AASHTO LRFD Article...0.b for combined thrust plus bending. Since the resin will have a minimum longterm strength of,000 psi, it will be able to undergo at least the magnitude of strain achieved at the design life during the,000 psi SIM test. Figure shows, for example at 0 years, this resin will have the ability to undergo at least.0% strain without rupture under a sustained stress of,000 psi, with the strain at an estimated 00 years still higher without the specimen demonstrating tertiary creep. Using a design factor of (note that the AASHTO load factor for thermoplastic pipe under earth load is.) gives a service level long-term tension strain of.% using the 0 year results. This value is proposed for use as the service long-term tension strain limit for the design of PP pipes in AASHTO LRFD Section.. Factored Compression Strain Limit The factored compression strain limit is used in determining the effective width of individual corrugation elements in AASHTO LRFD Article...0.b, and as compressive strain capacity when evaluating adequacy for thrust in Article...0.d. It is also used when checking adequacy for combined thrust and bending for the compression zone of the cross-section in AASHTO LRFD Article...0.b. National Cooperative Highway Research Project (NCHRP) Report () recommended the factored compression strain limit be determined as the ratio of long-term strength to modulus. For the proposed minimum long-term strength of,000 psi and long-term modulus of ksi above, the compression strain limit from these minimum values would be.%. More recently, NCHRP Report () found that a fixed strain limit for each thermoplastic is more appropriate than values from test results for individual resins. The recommendations of NCHRP Report were based on extensive laboratory testing during the development of the Stub Compression Test, AASHTO T -0 (). In the stub compression test (Figure ), a specimen taken as a chord of the circumference of the corrugated pipe is compressed between two load plates at a constant rate of advancement and the load and displacement (strain) are recorded. The specimen is nominally three corrugation periods in length. The strain at maximum load can be determined from the data, and the data can also be used to determine the effective area of the corrugation under compression load in AASHTO LRFD...0.b instead of the theoretical calculations for effective area. When evaluating strain at maximum load, machine flexibility must be accounted for in the results.

13 FIGURE Stub compression test. Results from stub compression tests on nine specimens of corrugated PP pipe manufactured from Candidate A and B resins are shown in Figure. These results are from four inch diameter pipe specimens, one inch diameter pipe specimen, and four inch diameter pipe specimens taken from different circumferential positions around the pipe (0, 0, 0, or 0 ). Load is shown in pounds per length of each specimen along the longitudinal axis of the pipe.

14 FIGURE Stub compression test load vs. strain plots for nine corrugated PP pipe specimens. Strains at maximum load after adjusting for initial specimen seating (toe compensation) and machine flexibility ranged from.% to.% for the nine specimens, all greater than.% strain calculated from the minimum long-term strength and modulus. Based on the minimum long-term strength and modulus values and as demonstrated by stub compression tests, a factored compression strain limit of.% is proposed for corrugated PP pipe in AASHTO LRFD Section..

15 0 0 CONCLUSION The AASHTO LRFD Bridge Design Specifications, Section., include provisions for the structural design of thermoplastic culvert pipe. Established minimum values of mechanical properties required for the structural design of HDPE and PVC pipes are presented in AASHTO LFRD Table...-. Corrugated PP culvert pipe has been used in Europe for several decades and has more recently become available in the United States. The AASHTO Materials Subcommittee recently published a material and product standard for corrugated PP thermoplastic pipe, AASHTO MP -. This standard has minimum material requirements for some mechanical properties used in the structural design based on properties recommended by Vanhoose and Biesenberger; however, the properties presented in AASHTO MP - do not address all of the mechanical properties required for structural design AASHTO LRFD Section.. This work presents the test methods and sampling procedures used to determine the mechanical properties for thermoplastic pipe design, and specifically to arrive at minimum mechanical property requirements for corrugated PP pipe. These recommended minimum properties for structural design are from test results on specimens made from four candidate resins readily available in the U.S. for the manufacture of PP pipe. Recommended minimum mechanical properties for corrugated PP pipe in AASHTO LRFD Table...- are as follows: Service Long-Term Tension Strain Limit, ε yt :.%. Factored Compression Strain Limit, ε yc :.%. Minimum Initial Strength and Modulus:,00 psi and,000 psi, respectively. Minimum 0 Year Strength and Modulus:,000 psi and,000 psi, respectively. Minimum Year Strength and Modulus:,000 psi and,000 psi, respectively. 0 Appropriate values for 00 year strength and modulus, where required for 00 year design life, are,000 psi and,000 psi. In lieu of proposing a minimum cell classification for the resins used in corrugated PP pipe, it is proposed to rely on the material requirements found in AASHTO MP - which are more tailored specifically to pipe resins than traditional cell classifications.

16 References:. Lars-Eric Janson, Plastics Pipes for Water Supply and Sewage Disposal, rd Edition, Lars-Eric Janson and Borealis - Stockholm. AASHTO LRFD Bridge Design Specifications, th Edition, Interim 00. American Association of State Highway and Transportation Officials, 00.. VanHoose, B., and J. Biesenberger. Long Term Material Design Properties for Polypropylene Pipe Grade Resins. Presented at Plastic Pipes XV Conference, Vancouver, CANADA, September 00.. AASHTO MP -. Standard Specification for Corrugated Polypropylene Pipe, 00- to 00 mm (- to 0-in.) Diameter. American Association of State Highway and Transportation Officials, 0.. AASHTO M -0. Standard Specification for Corrugated Polyethylene Pipe, 00- to 00- mm Diameter. American Association of State Highway and Transportation Officials, 00.. AASHTO M 0-0 (00). Standard Specification for Poly(Vinyl Chloride) (PVC) Profile Wall Drain Pipe and Fittings Based on Controlled Inside Diameter. American Association of State Highway and Transportation Officials, 00.. ASTM D 0-0. Standard Practice for Compression Molding Thermoplastic Materials into Test Specimens, Plaques, or Sheets. ASTM International, 00.. ASTM D 0-0. Standard Test Methods for Flexural Properties of Unreinforced and Reinforeced Plastics and Electrical Insulating Materials. ASTM International, 00.. ASTM D -0. Standard Test Method for Tensile Properties of Plastics. ASTM International, ASTM D 0-0. Standard Test Methods for Tensile, Compressive, and Flexural Creep and Creep Rupture of Plastics. ASTM International, 00.. Nielsen, L.E. Mechanical Properties of Polymers. Reinhold Publishing Corp., New York,.. ASTM D Historical Standard Database. ASTM International. P+DESIGNATIO+D+/usr/htdocs/astm.org/DATABASE.CART/historicalpick.frm. Accessed July, 0.. ASTM D -0 (00). Standard Test Method for Accelerated Tensile Creep and Creep- Rupture of Geosynthetic Materials Based on Time-Temperature Superposition Using the Stepped Isothermal Method. ASTM International, 00.. ASTM F -. Standard Specification for Polypropylene (PP) Corrugated Wall Stormwater Collection Chambers. ASTM International, 0.. McGrath, T. J., and V. E. Sagan. Recommended LRFD Specifications for Plastic Pipe and Culverts. Report, National Cooperative Highway Research Program (NCHRP), McGrath, T. J., I. D. Moore, and G. Y. Hsuan. Updated Test and Design Methods for Thermoplastic Drainage Pipe. Report, National Cooperative Highway Research Program (NCHRP) Report, 00.. AASHTO T -0. Standard Method of Test for Determination of Compression Capacity for Profile Wall Plastic Pipe by Stub Compression Loading. American Association of State Highway and Transportation Officials, 00.