The investigation of damaging earthquake effects during recent years has demon- strated that the statical analysis of buildings and other structures must be replaced by dynamical analysis, taking into consideration the additional forces and deform- ations of elastic and plastic character which are due to ground motions. Examples were cited from different countries concerning the effects of strong earthquakes on various kinds of structures, including specially designed earth- quake-resistant structures, and data were presented on the corresponding studies. It was emphasized that a necessary condition for further progress in designing earthquake-resistant structures is the acquisition of a greater volume of instru- mental data provided by standardized strong-motion instruments. Unesco was asked for assistance in organizing a working group to study and propose an appropriate network of strong-motion observations and the most suitable form of standardization of instruments.

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