Dynamic modal responses of wave-excited offshore structures

SURFACE STRUCTURES:DYNAMIC LOADS 945236 Pounding of buildings during earthquakes: a C a n a d i a n perspective A. Filiatrault, M. Cervantes, B. Folz & H. Priori, Canadian Journal of Civil Engineering, 21(2), 1994, pp 251-265. The main objective of this paper is to provide information to structural engineers on how to consider and mitigate the phenomenon o f pounding between adjacent structures during earthquakes. The first part of the paper reviews the problem of seismic pounding. A review of literature on analytical and numermal studies of earthquake pounding is presented along with methods that have been proposed to mitigate pounding. In the second part of the paper, the seismic behaviour of three closely spaced, Canadian code designed, plane steel frames is invesngated. -from Authors 945237 Uniform reliability safety format for seismic design of reinforced concrete structures S . N . Economou & M. N. Fardis, Earthquake Engineering & Structural Dynamics, 23(4), 1994, pp 413-431. A safety format is proposed for the flexural design of reinforced concrete members for the combination of seismic and gravity loads, with load and resistance factors which depend on member type, on the value of the target theoretical probability of failure and on the ratio of the load effect due to gravity loads to that due to the nominal value of the seismic action, both obtained by elastic analysis. The load factor on the seismic action is found to be independent of member type and to increase with the theoretical probability of failure much faster than the elastic spectral value at the structure's fundamental period with probability of exceedance in the structure's lifetime. Simple rules for the dependence of the resistance modification factors on the theoretical failure probability are also derived. -from Authors 945238 Dynamic modal responses of wave-excited offshore structures G. D. Hahn & R. Sanghvi, Journal of Engineering Mechanics - ASCE, 120(4), 1994, pp 893-908. Examinations are made of the dynamic effects associated with modal responses of deep-water, wave-excited offshore structures. Variations in the following parameters are considered: the distributions of the structural volume and projected area, the distributions of the inertia and drag force coefficients, the relative magnitude of the inertia and drag force components, the natural modes of vibration of the structure, and the random phase angles used for the generation of the wave loading. The response is examined for a wide range of values of the natural frequencies of the system, and the relative importance of the effects of changes in the parameters considered is elucidated. The results of the study provide valuable insight into the response of offshore structures to wave forces. -from Authors 945239 Consequences of a strong seismic activity in Costa Rica F. Sauter F., Revista GeoJisica, 36, 1992, pp 69-108. In 1990 and 1991, Costa Rica experienced a period of intense seismic activity. It began with a subductton earthqM~akc~l!°f moderate magnitude (Ms = 6.9), that occurred in 990 with its epicenter in the Nicoya Gulf on the Pacific Coast, and known as the Cobano Earthquake, Costa Rica, 1990. This event apparently activated local faults near the town of Puriscal, resulting in a series of events that lasted from May to June 1990. The rupture of a fault in the same area caused the destructive earthquake of December 1990 (Ms = 5.7). The seismic activity continued and reached its peak on April 22, 1991, with an event of great magnitude (Ms = 7.4). The strong seismic activity in Costa Rica demonstrated the necessity of reviewing the criteria and improve the bridge design practice. Inadequate support devices, lack of horizontal displacement restraint measures, absence of continuity and redundancy in the structural system, and lack of provisions to ensure structural integrity, were the main errors encountered. -from Author

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945240 On seismic h a z a r d assessment of sites of nuclear facilities (in Chinese) Hu Yuxian, Seismology & Geology, 15(4), 1993, pp 308-316. In the first part of the paper, the status and tendency of development of the methodology of seismic hazard assessment are reviewed with reference to recent documents such as Standard Specification ASCE-4-86 and IAEA 1991 Safety Guide, and in the remaining sections three main problems, i.e. the consideration of uncertainties, site effect and earthquake and site-dependent spectrum, are discussed. -from English summary 945241 On the relation of ground motion attenuation in NPP siting (in Chinese) Jin Yan, Seismology & Geology, 15(4), 1993, pp 341-346. The field characteristics and regional features in the data of ground motion, the consistence of definitions of variables and the distribution o f the original data must be considered in fitting ground motion data to the acceleration attenuation relation. Generally, the digital method should be used to get the acceleration attenuation relation through data transform, but the analysis method may be used under special conditions. The special seismic attenuation characteristics should be considered when the seismic intensity anomaly and very large earthquake are presented. -English summary 945242 Seismotectonic a p p r o a c h to evaluation of design basis ground motion (in Chinese) Pan Hua & Yah Jiaquan, Seismology & Geology, 15(4), 1993, pp 347-352. In this paper, the fundamental theory and basic principle of the seismotectonic approach to evaluation of design basis ground motion axe introduced firstly, then the difference between the new Safety Guide of IAEA and the old one is analysed. The defects in this method are discussed, and the actual problems which in using this method appear in nuclear power plants siting are discussed too. Finally, the development and improvement of the seismotectonic approach are suggested. -English summary 945243 The concepts of capable fault and surface faulting and their investigation (in Chinese) Li Yuanjun, Seismology & Geology, 15(4), 1993, pp 359-363. The concepts of capable fault and surface faulting are studied in this paper, and an emphasis is given on the extent of investigauon and requirements for the investigation in concrete seismological geologic siting for nuclear power plants. -English summary 945244 Determination of minimum e a r t h q u a k e magnitude in evaluation of seismic h a z a r d s at nuclear power plant site (in Chinese) Pan Hua & Zhang Xiaodong, Seismology & Geology, 15(4), 1993, pp 369-374. In this paper, the definition of the lower-limit magnitude is recommended, then on the basis of analysis of its determination in connection with real data of some earthquakes, the difference between the lower-limit magnitude and the minimum magnitude considered in seismic hazard evaluation is pointed out. The lower-limit magnitude is commonly 4, but the minimum magnitude may be lower. Thus, for the facilities with specific safety requirement, such as nuclear power plant, a substitution of lower-limit magnitude 4 for the mmimum magnitude may be unsafe. -English summary 945245 A comparison between the results obtained by seismotectonic method and probabilistic method used in the evaluation of ~round motion for design of nuclear power plant (in Chinese) Gao Mengtan, Seismology & Geology, 15(4), 1993, pp 384-388. The results obtained by probahilistic method and those obtained by seismotectomc method are compared. The result suggest that: 1) the result by seismootectonic method is not an upper limit determined by probabilistic method; 2) the relationship between the results obtained by both these methods at certain exceedance probability levels