Three prestressed concrete portal frames (span=2.6m, height=O.9m)were loaded horizontally. Resistance against lateral force, ductility, and dynamic behaviours of these frames were examined.

As the results of the experiment, the following facts were clarified:

1. Ultimate design method is applicable for prestressed concrete portal frame.
2. Deterioration of deflection characteristics under repeated loading is not considerable.
3. Ample ductilities are guaranteed.
4. Increment of period of natural vibration,and of fraction of critical damping, in accordance with increment of load are small.

* Manuscript received on July 27, 1964.
** Research Member of B.R.I , Ministry of Construction