Many buildings had stopped their service due to damage to non-structural members including ceilings, partition walls and piping after large-scale earthquakes. In particular, piping-failure-caused water leakage damaged electronic equipment and resulted in a loss of functionality of the building. Cyclic bending tests are conducted of carbon steel pipes for water supply piping with nominal diameters of 25A, 40A, 50A and 80A to evaluate their deformation capacity and strength. The results are summarized as follows.
1. The failure pattern depends on the pipe diameters. The pipes with a nominal diameter of 25A crack at the thread part and then fracture. On the other hand, the screw part of the 40A, 50A and 80A pipes are deformed and eventually come loose.
2. The bending strength begins to decrease when the deformation angle reaches about 0.03-0.07rad independent of the pipe diameters.
3. The skeleton curves of moment-deformation angle relation are obtained for pipes with different diameters. The maximum deformation angle of the pipe joint needs to keep under about 0.03 rad to prevent fractures.
