While studying a weld failure on a tower crane section, it was discovered that the weep(drain) holes were plugged. As a result, there was standing water that froze and split the weld. The failure mode was ductile overload that started at a stress concentrator created by the weld meniscus The destructive force is created by the ice forming a plug and the growth of the ice into the remaining water. The ice has a larger volume than the water from which it is formed. The water is non-compressable; therefore, force is created. In addition, it increases as the ice grows. In this case the force generated was sufficient to rupture the weld along the leg. The failure was discovered during the daily inspection, and the crane was taken out of service to be repaired.