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Results of tests show that a slowly rising condenser-discharge preheat current with a rapidly rising welding current afford no less expulsion than a rapidly rising welding current alone, and was inferior to a slowly rising welding current alone. In one case using slowly rising current for preheating and welding proved beneficial although generally, utilizing a raised electrode welding force to decrease expulsion was more practicable. Postheating had no effect on sheart strength until the current sufficient to remelt the welds, which greatly increased the weld diameter and shear strength.
Damage to structures due to vibrations from pile driving operations is of great concern to engineers. This research has stemmed from the need to address potential damage to concrete-filled pipe piles and recently placed concrete structures that could be affected by pile driving vibrations. The study will focus on two topics: (1) The attenuation of potentially damaging pile driving vibrations with distance from the source, and (2) The effects of distance and curing time of concrete on the quality (unconfined compressive strength) of recentlyplaced concrete exposed to pile driving vibrations. The effects of pile driving vibrations did not cause problems with concrete compressive strength except for the case where concrete had only cured for 4 to 6 hours before vibration.