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The effects of transient foundation uplift on the earthquake response of flextole structures are investigated. The structural idealization chosen in this study is rełatively simple but it incorporates the most im porta nt features of foundation uplift. In rts fixed basa condition the structure rtself is idea ii zad as a single-degree-of-freedom system artached to a rtgkJ foundation mat which is flexibly supportad. The flexi-bility and damping of the supporting soil are represented by a Winkler foundation with spring-damper element* dis-tributed over the entire width of the foundation. Based on the response spectra presented for several sets of system parameters, the effects of foundation-mat uplift on the maximum response of structuret are identified. The influence of earthquake intensity, structural slenderness ratio, ratio of foundation mass to structural mass, foundation flexibility and p~B effects on the response of uplifting structures is also investigeted.

A finite element method is presented to analyze the effects of airbtast-induced ground shock on shallow-touried, flat-roofed, reinforced concrete structures. A finite element based on Timoshenko beam theory is adopted. Materiał properties are defined in terms of nonlineer stress-strain retetions in eech of several layers through the thickness of the element. Elastic, idee lly-ple stic constitutive properties for plain concrete are cast in terms of shear-stress/normel-stress variables. Elastic, strain-hardening constitutive properties are assumed for Steel. Dynamie explicit and implicit and static solution algorithms are available.

POWER PLANTS

(Also see Nos. 1753, 1757)

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UNDERGROUND STRUCTURES

84-1593

Dynamie Response of Twin Circular Tunnels Due to Incident SH-Waves

T. Balendra, D.P. Thambiratnam, Chan Ghee Koh. and Seng-Lip Lee

Natl. Univ. of Singapore, Singapore. Earthquake Engrg. Struć. Dynam.,J2J2), pp 181-201 (Mar/Apr 1984) 12 figs, 2 tables, 10 refs

Key Word*: Tunnels. Underground structures, Wave reflec-tion

The staady-state solution for two parallel underground tunnais of circular cross-section subjected to incident piane harmonie SH-wavet is obtained in closed form, by using the method of weve function expensk>n. The image technique it amployad to account for the reflection of waves at the ground surface. NumerkaI studies are carried out to deter-mine the influence of sparing between the tunnels on the shear stretaes in concreteand Steel linings.

84-1594

R/C Structures under Impulsńe Loading

J. Ghaboussi. W.A. Mil(avec, and J. Isenberg Univ. of Illinois, Urbana, IL, ASCE J. Struć. Engrg., 110 (3). pp 505-522 (Mar 1984) 15 figs, 1 table, 14 refs

Key Words: Underground structures. Reinforced concrete. Aerlel expłosions, Ground shock, Expk>sion effects

84-1595

Suitability of Syntheaized Wayeforma for Ścianie QuaIification of Equipment

D.D. Kana and D.J. Pomerening Southwest Res. Inst., San Antonio, TX 78284, J. Pressure Vessel Tech., Trans. ASME. 106 (1), pp 63-68 (Feb 1984) 15 figs. 14 refs

Key Words: Nucłear power plents. Equipment response. Seismk response, Quelifkation tests

Qualification of nuclear plant equipment and components can be performed by analysis, test, or a combination of both. It is often required to synthesize artificial time historie* which represent earthquake excitation at either ground level, or some eleveted level of a structure. A set of parameters appropriate for the synthesis of acceleration time historie* is developed. The parameters are based on a study of six typical earthquake accelerograms, and include generał charac-teristics of the motion, a definition of strong ground motion, frequency content, statronarity, coherence between orthog-onal components. and amplitudę probebility densłty. It is concluded that the strong ground motion can be approxi-mated by a stationary Gaussian random proces*, whose frequency content depends on the ground or ele>«ted posi-tion of concern.

OFF-SHORE STRUCTURES

84-1596

Hydrodynamic Korce8 on Klexible Offahore Struć turea    *

E.J. Laya, J.J. Connor, and S.S. Sunder

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