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From page 9... ... - 7 - CHAPTER 3 FINDINGS AND APPLICATIONS The research findings are presented in the six following areas: • Overview of joint types and the key quantities required for structural design; • Information regarding the field performance of culvert joints; this was undertaken by collecting information from State DOTs, and through field testing six culverts in Ohio; • Laboratory testing was undertaken of six representative buried pipe joint systems to capture culvert joint performance under surface live load, to assess the influence of surface load position, and to investigate different levels of construction quality; laboratory testing was also undertaken to assess the strength of joints in three representative pipe systems; • Computer analyses were conducted to examine the potential for exploring local effects in pipe joints and the potential for using beam-on-elastic-spring analysis of joint behavior; • Simplified design equations were developed using beam-on-elastic-spring analysis of two pipes interacting at a joint, for both rigid and flexible culverts responding to earth loads and surface live loads; • Design specifications were developed for a simplified design method based on approximate equations and an alternative approach based on finite element analysis of pipes represented as beams on elastic springs; example calculations are provided based on the simplified design method. Overview of joint types and structural design requirements There are essentially two kinds of joints, which differ in how they treat the longitudinal bending that arises from surface loads and variations in bedding stiffness along the pipes: • those designed to permit rotation of one end of the pipe relative to the next, thereby releasing the longitudinal bending moments; these are designated throughout this report as ‘moment-release joints'; examples include gasketted bell and spigot joints, gasketted tongue in groove joints, and those two joint types used without gaskets; • those designed to limit rotation of the two pipe ends relative to each other, and transfer longitudinal bending moments from one pipe to the next; these are designated throughout this report as ‘moment-transfer joints'; examples include band joints and welded connections. Read the entire page →
From page 10... ... - 8 - • the bending moment that acts across moment-transfer joints; • the axial force that acts across moment-transfer joints (it is assumed that momentrelease joints have very limited ability to transfer axial tensions) ; and • the expected rotation of one pipe relative to the other across moment-release joints. Read the entire page →
From page 11... ... - 9 - • 48 inch (1.2 m) diameter reinforced concrete pipe with bell and spigot joint, tested without a gasket, representing the performance of joints assembled without seals • 36 inch (0.9 m) Read the entire page →
From page 12... ... - 10 - Laboratory testing Buried pipe tests Laboratory tests on culvert joints consisted of two testing programs. The objective of the first was to examine the six different jointed culvert systems selected for testing (as discussed in the previous section) Read the entire page →
From page 13... ... - 11 - Top left (first CSP) , Top Middle (first RCP) Read the entire page →
From page 14... ... - 12 - a. 24 inch (0.6 m) Read the entire page →
From page 15... ... - 13 - a. Longitudinal cross-section showing three surface load positions (compacted bedding excavated and filled with loose material to accommodate protruding bells, denoted ‘void' here) Read the entire page →
From page 19... ... - 17 - These experimental results are for vehicle loads, and earth loads are also important. While it is not straightforward to simulate deep burial in the large scale testing facility at Queen's, earth load effects on joints are important nevertheless. Read the entire page →
From page 20... ... - 18 - a. Illustration of the experimental configuration b. Read the entire page →
From page 21... ... - 19 - Rotations commenced once the vertical force reached about 2.5 kips (12 kN) , the load needed to support the pipe weight. Read the entire page →
From page 22... ... - 20 - representing the circular shape of the pipe, total section properties A (the total area of the crosssection) and I (the second moment of area of the cross-section) Read the entire page →
From page 23... ... - 21 - The assumptions associated with beam-on-elastic-spring analysis greatly simplify the analysis, and make it straightforward to consider situations involving just two pipes interacting across a joint, or a whole series of pipes connected by joints. However those approximations: • Mean that the analysis provides no input on changes in shape or stresses and strains around the circumference of the joint • Violate the normal restrictions for use of thin beam theory where beam (i.e. Read the entire page →
From page 24... ... - 22 - Simplified design equations Simplified design equations have been developed for rigid and flexible pipes based on the observations made in the earlier section reporting on vertical deformation patterns along the springlines of buried culverts as a result of surface live load. Appendix E summarizes background concepts for the simplified design, and Appendix F provides details of the derivation of the equations. Read the entire page →
From page 25... ... - 23 - either side of the joint being considered, and neglects the resistance provided by all the other pipe segments beyond those two adjacent pipes. Appendix F includes additional discussion of the conservative nature of the ‘two beam'-on-elastic-spring approximation compared to finite element solutions for beam-on-elastic-springs involving more pipe segments. Read the entire page →
From page 26... ... - 24 - length L0 along the pipe and width W0 across the pipe. As with earth load, the depth considered here is that to the springline of the pipes (since use is being made of beam-on-elastic spring theory, and the springline is the location equivalent to the beam ‘centroid') Read the entire page →
From page 28... ... - 26 - Figure 9. Design principles for two flexible pipes connected by a moment-release joint. Read the entire page →
From page 29... ... - 27 - Simplified design of moment-transfer joints connecting flexible culverts The development of design equations for flexible pipes connected by a moment-transfer joint is very similar to the process used for moment-release joint. Now, however, earth loads lead to expressions for shear force and bending moment which must consider compatibility of both vertical deformation and rotation at the point connecting segments of pipe resting on soil with changing stiffness. Read the entire page →
From page 30... ... - 28 - diameter. However, at present there are no experimental data to demonstrate that this modeling approach works successfully for these cases. Read the entire page →
From page 31... ... - 29 - The data in Figure 10 is back-calculated using the tests reported in Appendix C for pipes placed in sandy gravel backfill. Terzaghi (1955) Read the entire page →
From page 32... ... - 30 - Table 1. Values of for beams 1 ft (0.3 m) Read the entire page →
From page 33... ... - 31 - Design specifications and design examples Draft revisions for the AASHTO LRFD Bridge Design Specifications are provided in Appendix G This includes the following material: • Strength limit states in 12.5.2 are augmented to include joint failure • Values of resistance factors in 12.5.5 are augmented to include values for joint failure; resistance factors of 0.67 are suggested to match those already present for the longitudinal seam strength of corrugated steel structures; this relatively low resistance factor also reflects the fact that pipes are joined in the field (without the control associated with pipe manufacturing) Read the entire page →
From page 34... ... - 32 - These specifications will: - provide product manufacturers with the requirements for structural capacity of joints (so they can ensure their jointing systems have adequate capacity to transfer shear force and longitudinal moment) , or so they can determine what restrictions on burial depths are needed for specific products and joint systems (minimum and maximum burial depths that ensure factored demand is less than factored resistance) Read the entire page →
From page 35... ... - 33 - with moment-transfer joint, indicate that these existing systems have joints satisfying the structural design requirements being proposed. Read the entire page →

From page 9...

... - 7 - CHAPTER 3 FINDINGS AND APPLICATIONS The research findings are presented in the six following areas: • Overview of joint types and the key quantities required for structural design; • Information regarding the field performance of culvert joints; this was undertaken by collecting information from State DOTs, and through field testing six culverts in Ohio; • Laboratory testing was undertaken of six representative buried pipe joint systems to capture culvert joint performance under surface live load, to assess the influence of surface load position, and to investigate different levels of construction quality; laboratory testing was also undertaken to assess the strength of joints in three representative pipe systems; • Computer analyses were conducted to examine the potential for exploring local effects in pipe joints and the potential for using beam-on-elastic-spring analysis of joint behavior; • Simplified design equations were developed using beam-on-elastic-spring analysis of two pipes interacting at a joint, for both rigid and flexible culverts responding to earth loads and surface live loads; • Design specifications were developed for a simplified design method based on approximate equations and an alternative approach based on finite element analysis of pipes represented as beams on elastic springs; example calculations are provided based on the simplified design method. Overview of joint types and structural design requirements There are essentially two kinds of joints, which differ in how they treat the longitudinal bending that arises from surface loads and variations in bedding stiffness along the pipes: • those designed to permit rotation of one end of the pipe relative to the next, thereby releasing the longitudinal bending moments; these are designated throughout this report as ‘moment-release joints'; examples include gasketted bell and spigot joints, gasketted tongue in groove joints, and those two joint types used without gaskets; • those designed to limit rotation of the two pipe ends relative to each other, and transfer longitudinal bending moments from one pipe to the next; these are designated throughout this report as ‘moment-transfer joints'; examples include band joints and welded connections.