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Feb 08, 2005 The presentation shows the new calculation program "Co-Jack" (Computing and Controlling Pipe Jacking) for a structural simulation of pipe jackings. |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Structural Calculations for Self-Supporting Linings in the Shape of Pipes (Image: Depiction of various paths in the load displacement diagram to [Krätz94]) In the analysis of failure the size of the load is calculated in which the structure cannot, or only under conditions of impermissible deformation, accept any further increase of the load. An exact depiction of the theoretical background is given, for example, in [Hibbi95] [Krätz94] [Mehlh95] [Steup66]. The following terms are of great importance (Bild 5.3.2.6.1.1).
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability (Image: Buckling of a free ring under external pressure [Guice94a]) Timoshenko describes the buckling behaviour of the free thin ring under a constant external radial load. In the case of any small starting deformation there develops under critical loading the buckling of the circular ring as is shown in Bild 5.3.2.6.1.2.1. The bending moment M at any point of the circular ring can then be developed from the equilibrium conditions and geometric linkages … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability Gaube, starting from investigations on free pipe in the ground under external water pressure, developed a semi-empirical statement for proving the stability of embedded sewage pipes of plastics [Gaube74]. This takes into account the support effects of the soil as well as also the deformation (ovality) of the pipe attributable to the earth load. First the buckling pressure pk0 of the free un-deformed pipe against external pressure is determined either … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability Glock analysed the stability program of a rigid outside-coated, linearly elastic circular ring under external water pressure with the use of geometric non-linear deformation relationships according to the energy method. Friction between pipe and outside coat, imperfections of the loading and geometry as well as non-linear material behaviour were not considered. Separation of the pipe from the coat is conditioned by the circumferential shortening … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability Cheney [Chene71], like Glock, investigated the buckling behaviour of a ring enclosed within a rigid coat that was subjected to external pressure under the condition of linear elastic material behaviour. His analysis was carried out in similarity to the stability theory of the arched girder [Timos61] [Guice94c]. For small relationships t/Dm there then results the critical buckling pressure of: (Formula: Critical buckling pressure (Cheney)) |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability Also Chicurel [Chicu68] investigated the buckling behaviour of a thin elastic externally coated ring in similarity to the stability theory of the arched girder [Timos61]. However, he assumed that the inner ring experiences the external loading because of a reduction of the diameter as could occur in shrinkage processes. Although this statement does not correspond exactly to the relationship of a liner under external water pressure it seems, up to … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability Lo and Zhang [Lo94] developed, in similarity to the stability theory of the circular arched girder [Timos61], a model for the buckling of the circular liner, which also considers the influence of a small ring gap. The total gap width is comprised of two different parts, the starting ring gap Δ1 and the ring gap Δ2 resulting from the hydrostatic pressure. A difference is made between an unsymmetrical and a symmetrical failure figure (Bild 5.3.2.6.1.2.6) |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability Falter investigated the bearing relationship of liners on the basis of non-linear geometric calculations on rigid frame models [Falte94a]. The calculation was carried out on the assumption of constant loading over the length of the pipe, ignorable friction between liner and old pipe and true-direction loads for "small displacements", whereby also deformation and the formation of gaps were considered. The starting point is the Glock buckling formula (… |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability The formula of the American Society for Testing and Materials F 1216-93 [ASTMF121693] for calculating the critical buckling pressure is the result of investigations of hose liners in steel pipes in which the diameters, the wall thicknesses and the modulus of elasticity were varied. The liners were loaded to failure and the experimental buckling pressures were compared with the critical buckling pressure of the free pipe according to Timoshenko (Formel … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability Wagner carried out short-term buckling experiments in which 135 Insituform pipes of length 3.50 m were loaded with an external radial water pressure up to collapse. Seamless steel pipes with nominal sizes 250 and DN 300 provided rigid outer coats. For determining the buckling loads resulting from the experiments in their applicability in the range 15 < r/ws < 120, Wagner developed the following limited buckling equation: (Formula: Buckling equation … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Empirical and Analytical Statements for Describing the Failure of Stability A stable old system is assumed in general for sizing liners as information or an accompanying effect is not yet reliable. As for the pipe-soil- system to [ATVA127b], so also must proof of stress, of deformation and of stability be provided for the pipe-in-pipe system. Non-linear FEM calculations are always to be preferred to a superimposition of analytical solvents. However, there also exist good approximations that permit a pre-sizing and qualitative … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Structural Calculations for Self-Supporting Linings in the Shape of Pipes In the past, several empirical and analytical solution statements have been developed for defining the critical buckling pressure of pipes of circular cross section under external pressure [Guice94d]. Fundamental links to the buckling behaviour of the free pipe were presented by Timoshenko in [Timos61]. Building on this, Gaube [Gaube74] described the particular failure behaviour of bedded plastics pipes by means of semi-empirical statements. Glock [… |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Calculations with the Aid of the Finite Element Method (FEM) The circular liner is generated about the circumference with a sufficient number of elements, and through the layer thickness with several element layers. The network refinement should be proved to be sufficient to be able to truly model also substantial wall thickness increases [Mielk97]. For instance, 8-node iso-parametric continuum elements (CPE8 [Hibbi95]) with quadratic geometry and displacement statements can be utilised so that also the curvature … |
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Feb 16, 2011 Rehabilitation and Maintenance of Drains and Sewers Calculations with the Aid of the Finite Element Method (FEM)
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Structural Calculations for Self-Supporting Linings in the Shape of Pipes Numerical methods of calculation are very important in many sectors of engineering today. Because of the manifold possibilities of its application, the Finite Element Method is the method used most often even though the border element method (BEM), the Discrete Element Method (DEM) as well as the Finite Difference Method (FDM) in some cases present good alternatives [Schwe94]. In the Finite Element Method, the unknowns within an element are approximated … |
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Nov 23, 2004 There are numerous analytical and empirical statements for describing the bearing and failure behaviour of self-supporting liner with circular cross sections and these have been defined for very different border conditions and thus make their direct utilisation in practice difficult without knowledge of the theoretical backgrounds. As a rule, they only account for the failure of stability of circular, free, or externally coated pipe cross sections … |
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Nov 23, 2004 Rehabilitation and Maintenance of Drains and Sewers Structural Calculations for Self-Supporting Linings in the Shape of Pipes The theories of Glock and Timoshenko present the border cases of buckling failure of circular cross section. From these there results for the free pipe according to Timoshenko: (Formula: Critical buckling load for the full-walled free pipe with a length of "1" (Timoshenko))for the pipe-in-pipe system according to Glock: (Formula: Critical buckling pressure (Glock))In the comparison of the calculations of the buckling load values of the pipe-in-pipe … |
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Nov 23, 2004 In the past, proof of stability for self-supporting liners was generally provided in the Federal Republic of Germany using ATV-M 143 Part 3 [ATVM143-3] and in a manner similar to ATV-A 127 [ATVA127b], although this latter guideline was developed exclusively for new laid pipes and is based on a pipe-soil structural system (elastically bedded circular ring). As its kinematic permissible deformation figures and its resulting loading deviates from that … |
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