Assessment of the Nonlinear Behavior of Connections in Water Distribution Networks for Their Seismic Evaluation

Abstract

Connections, used in water distribution networks, have mostly a nonlinear force – displacement or moment – rotation relationship, subjected to extensive ground deformations due to large earthquakes. On the other hand, to evaluate the seismic functionality of water distribution networks, which should be performed with high reliability for seismic risk reduction purposes, the determination of realistic nonlinear behaviors of connections in water distribution networks is very important. In this study the nonlinear behaviors of various types of connections, have been assessed numerically by using finite element analysis (FEA). For this purpose, different sizes of pipes, elbows, and Tees in various combinations have been considered, and their body has been modeled by solid elements, between them contact conditions have been introduced wherever necessary. Special attention has been paid to the rubber gasket used in Tyton joints. For obtaining the nonlinear relationship in each case, one end of the connected parts has been assumed to be fixed, and a force or a moment has been applied incrementally in an appropriate direction or around an appropriate axis, till reaching the ultimate state, which is when the convergence cannot be achieved in FEA anymore. Results show that for rotation values above 0.005rad most of connections enter the nonlinear range, however, with regard to force – displacement behavior the displacement value at which the connection enter the nonlinear range various form less that a centimeter to a few centimeter depending on the connection type and the parts sizes.