A numerical analysis of the initially clamped bolt joint subject to the working pressure is presented in the paper. Special, hexahedral 21- and 28-node isoparametric finite elements have been employed to model the contact zone. In this model, one takes into account loading due to the working pressure in the gap between the gasket and the flange arising as an effect of the progressing joint opening, what has not been considered in recent papers. Nonlinear stiffness characteristics of the bolt and the flange with the gasket are developed. Working pressure corresponding to the critical bolt force resulting in the joint leakage (complete opening between the gasket and the flange) is determined. FE computational results are compared with the available experimental results. The numerical results are presented using the authors' own graphical postprocessor.

Many gas companies build and operate gas distribution system in the city country and around the world. The traditional open-cut excavation requires the ground to be broken up by heavy equipment, the soil and asphalt need to be removed. Traditionally, a technician requires a minimum of 60 cm by 180 cm excavation to perform routine procedures. Often the trench must be temporarily supported using some type of shoring before a utility worker can enter the hole to perform the repairs to the utility pipe. This process is costly, time consuming, dangerous and is inconvenient to traffic patterns. We propose a new solution called keyhole technology which minimizes labor and restoration costs compared with conventional practices. In our design, the same construction and maintenance procedures can be accomplished through a 45 cm diameter circular holes above the utility pipe to be repaired. However, specially designed, long handled tools that operate remotely are necessary. This process is more cost-efficient, less dangerous and less disruptive to traffic patterns because there is no additional milling and overlaying of the road. The small hole requires little replacement materials to fill the hole. Because the concept is relatively new to the public utility sector, there is a lack of equipment/tools available that could perform the required services. The finite element analyses using commercial package Abaqus will be employed to obtain the force needed to close the pipe. As a final example, we will show the topology optimization of squeeze–off tool as the act of an iterative process. The correctness of the numerical calculations was verified by a pipe compression experiment on Instron 8850 testing machine.