HYDRODYNAMIC PRESSURES GENERATED DURING EARTHQUAKES ON STRUCTURES. SURROUNDED BY WATER.

Abstract

1 * 1. II LRO9!JC TI O 1.1.1. Nearly, all of Northern India is vulnerable to earthquakes, Speotally some parts of Aenas, Jasoa and Kashmir and Gujarat cone under the zone of very strong earthquakes. A glance to the map of setsato soning of 1n4la (1) will atone. Indicate the Vulnerability of a place to earthquake* The design of any important @true . tur. In such zones has to be earthquake resistant design from standpoint of safety. 1,,1, 2 Mi earthquake way occur at a pl aa+o where the sstreaoes (due to tectonic farces) that had been building up along a f ult over many years when exceed the strength of the rooks, the fault break@ up resulting In an earth-quake. The energy released by the earthquake is trans-a! ttod to the earth crust through elasticwaves. There are two major #rtento raves (1) Longitudinal or 'P' waves nd (ii) Transverse or Shear or '3' waves. In the longt~. tudtnal waves, the parti ales pushed by the seismic die -turbanoo move back and forth in the direction of propa gation of the wave. In the transverse wares, a particle Notes The numeral an the parentheses represents the reference numberIvon. In the end. 2 which is pulled sideways by the disturbance pulls its neighbour aside to turn and the disturbance is propagated by a ware in which the individual part . ioles Hove at right aadl es to the path of propagation, A l ong.i tadt nal wave travels twi +mar as fast as a trans, verse wave, and therefore, roaches the earth cruet fi rat, The transverse waves have greater amplitudes and deetr. uotivo power than longitudinal waves. 191,03 The safety of a structure in eeieaic region denanda that it should be designed for earthquake forces aloof, The earthquake resistant design of sti uotures Is based on the thorough understanding of earthquake foroes and their e aluati on. In particular reference to hydraulic structures nicli as doss,, reservoir intake towers and bridge piers, the major forces Imposed by earthquake on au+ah structures are inertial forces and hydro-dynamo forces. In earth dame, increase in pear pressures any also be a factor* The evaluation of inertial force presents no difficulty and is, In favt, very einpl., but the evaluation of bydrodynae is force requires a knowledge of the distribution of hydrodynamic prassuree1 Per dams with vertical upstream face, the classical theory developed by U.K,Weeterd ►erd(2)*ty be used for the determination of hydrodynamic force. For dame with sloping upetrean faces, the expressions developed by C,N,Zangsr~ }provide the necessary tools for the evaluation of dynasto water pressures. N 1.1.4 lowsysr, for structures surrounded by water such as reservoir Intake towers and bridge piers, hero is no theory developed So far for hyda dyna*to pressures so exact and well recognised as that for dams, Thouo the mathematical theory developed by L,S,Jaoobsen(d for circular cylinders provides a basis for the evaluation of hydrodynamic pressures, it still stands for experimental verification.. i.a scope OF 1NY ?MMATX0N 1,2,1 The author has studied sxtiertWentahly the variation of hydrodynesiu pressure on a otroniar cylinder of 80 diameter and St high and also in reotaiutar model 9zl8*x3 o aOh model was placed in the contra of the Snook vibration table (sire 8*3ux1m). The vibration table was tilled with water isad the tests were carried out at tiro ' different water depths (l)2'6"`, and (2) ,alb".. The table was given tapulaive motion with the help of a pendulum. The acceleration of the table, so Imparted, was measured by, anise ration pick-up and recorded on a pen recorder, The tests wart carried out a two different aced+ matt ens of the table (1)io4%, and (11) 50% of gravity, The dyeo pressures were measured by a diaphragm type pressure pick up and recorded on a pen recorder, 1.2,2 The author has mods tied the + soobeents equation • 28(b) into dimensionless form, equation (37), The dimensionless equation (37) has made it possible to develop a don--dimensional plot for the hydrodynnmio pressure distribution for circular oyrlinlers, and i o presented In Chapter IV, article 4,4, 5