620 Ingenieurwissenschaften und zugeordnete Tätigkeiten
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Struktural design of linings
(2001)
The German Worksheet ATV-M 127-2 published in January 2000 after a seven years period of preparation and discussion is now well accepted in design practice for lining systems made of different materials and installed in various methods. The concept based on stress, deformation and stability analyses supports simple formula and diagram usage in standard cases like circular pipes up to ND 600 and more elaborate analyses for non-circular cross sections. Beside a short description of the design code the theoretical background is presented. Experimental test configurations are discussed regarding restrictions such as test specimen length, friction and load distribution. There is need of further research projects in co-operation with other universities to solve the problems left in theory and in practical use.
With the assessment of sewers and drains generally recognised criteria such as tightness, stability, hydraulic capability and efficiency are valid. For the assessment of the stability, however, there are often uncertainties. In this connection the ATV-DVWK Advisory Leaflet ATV M 127-2 represents a practical development of the system of rules and standards for the stability of earth-bedded pipelines that is called upon in the case of dimensioning for rehabilitation procedures. Nevertheless, further assumptions about the pipe-soil system are necessary which often are based on individual appraisals and experiences of the designer. To that end, in the years 1999 to the beginning of 2002, extensive experiments and theoretical investigations were carried out at the Universities of Bremen and Muenster as well as at the Bremen hanseWasser GmbH in order to assess more reliably the load-carrying capacity in particular of damaged host pipes in the ground. The research was supported by the Federal Ministry for Education and Research (BMB+F) under the short title ASSUR. The paper gives a view of the essential contents of the research; further information can be taken from the final report to ASSUR.
The German Code ATV-M 127-2 published in 2000 for the design of linings to rehabilitate sewers has proved itself a helpful guideline to find the optimum wall thickness of any liner material, e.g. CIPP or stainless steel sleeves. Many rehabilitation projects in different European countries have been performed successfully using this code. The code differentiates between three host pipe states: State I for untight sewers without cracks, state II for sewers with longitudinal cracks but a stable soil pipe system and state III for cracked pipes with larger deformations and considerable risk to collapse in the near future. State II sewers but installed close to the traffic surface must be calculated as a state III situation too. According to the code stress, deformation and stability tests are necessary. For many practical cases charts with stress factors and imperfection reductions allow to design without a computer. Numerous theoretical and experimental papers are available which mainly deal with circular linings. An evaluation of design codes carried out by experts of different countries shows a fairly good coincidence of the required wall thicknesses, but the assessment of pipeline damages by engineers is sometimes resulting in quite different assumptions necessary for the design input parameters. The paper reports about the progress in liner design since the 1st edition of the code. Additional clauses have to be introduced into the 2nd edition for non circular geometries (e.g. for hood and rectangular profile), imperfections describing practical and theoretical situations and new applications (e.g. railway crossings). International discussion can be useful to find safe and resources saving constructions.