Wharves or piers of open construction are sometimes acted by upward force due to wave motion under the deck. The cahracteristics and magnitude of such wave force were experimentally stuided with a reducted model.
　The intensity of uplift depends on various factors, such as incident wave height, wave period, tide level, size and shape of superstructures, etc. As a rule, the uplift increases with wave height and decreases with the clearance between deck and still water level. Fairly long wave has more dangerous effect than short peirod wave.Some experimental formulas were presented to estimate the design load.
　This wave force is a kind of shock pressure with very short duration, caused by an impact of water surface against deck slabs or girders. The mode of escape of enclosed air or water mass has a certain effect on the pressure intensity. The phase difference between each local pressure also affects the average intensity over a relatively wide area.
　The stability of structural members shoud be examined considering their response to impulsive force. In the model experiment, the local pressure intensity was measured by pressure cells and the average intensity was evaluated from the strain in model deck slabs, taking into account the similarity in vibration characteristics. Usual slabs or girders in the prototype have fairly high natural frequency and the effective average pressure for design purpose attains to 4～8t/m2, for example, under violent waves and high tide. In case of structural members which resist the uplift with their own gravity, the net weight of 1.5～3t/m2 or so is enough for practically stable state.
　The experimental results in this report will serve the structural design and the layout of wharves, piers and other berthing facilities.