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[en] The aim of the recently completed European research program Meakado is therefore to study design options with requirements proportioned to the actual seismic context of constructions in areas characterized by a low or moderate seismic hazard, contrary to most researches aiming at maximizing the seismic performances. In this general framework, specific investigations have been carried out regarding typical beam profiles commonly used for multi-bay - multi-storey composite frames. In a first stage, experimental tests on class-3 composite beam-to-column connections were performed. The measurement results were evaluated with regard to the development of the hysteretic behavior with particular emphasis on the degradation. These test results have been used as reference for the calibration and validation of numerical model aiming at extending the scope of the experimental outcomes through appropriate parametric variations regarding the behavior of nodal connections as well as towards the global analysis and behavior of structures made of class 3 and 4 profiles. Numerical investigations of the global performance of composite frames with slender cross-sections are then performed resorting to the numerical model previously calibrated with respect to the experimental tests and additional simulations at node level. Results are compared to the performance of an equivalent frame made of compact steel profiles. Attention is paid to the effects of strength and stiffness degradation due to local buckling. The analysis of the results is specifically focusing on the comparison of the rotation capacity of the slender section with the actual rotation demand imposed by a moderate intensity earthquake. Based on the outcomes of these investigations, practical design recommendations are finally derived for multi-storey, multi-bay moment resisting frames with type b (full composite action) beam-to column connections located in low and moderate seismicity regions. (Author)
[en] In this paper the recording materials of seismic waves are listed and the problems of the accuracy of measuring of the coordinates and of the estimates of the energy parameters are discussed
[en] “Disasters” such as seismic events, impact or fire loading to structural elements of crucial importance highlight the significance of structural design for robustness. Consequently, exceptional load scenarios are to be considered. The question whether the joints of structures designed according to the current version of Eurocodes have adequate load bearing and deformation capacity for such load cases arises. The “alternate load path method” plays a key role in structural design for robustness. By using this design approach, redistribution and distribution of the existing and additional loads, respectively, to the intact structural elements should be enabled after a local failure such as “loss of a column”, preventing so the progressive collapse of the structure. In order to pursue the aforementioned goal, sufficient bearing as well as rotational capacity of the joints are required. In particular, for exceptional events, change of the moment’s sign in the area of the joints is often to be observed. However, until today, attention has been paid mainly to the response of composite joints under negative moments. Herein, besides this load case, the corresponding one of positive moments is investigated as well as the development of a membrane action that supports the load redistribution but requires a tension force capacity of the joints. Experimental research for the load case “loss of a column” was undertaken on both single composite joint specimens and composite frames. Also, an integrated design method, the beamline method, is analysed and constructional recommendations for design of ductile composite joints were developed and are herein presented. (paper)
[en] This paper analyzes the rose diagrams of the directions of 439 faults of the Variscian province, 476 faults of the Caledonian province, and 603 presently active faults of Tien Shan. It is shown that more than half of the faults of the Caledonian province of Tien Shan are a result of Late Paleozoic orogenesis, which spanned its entire territory. Our data indicate that seismic events of Tien Shan have resulted in no formation of new disjunctive dislocation in many cases exhibiting displacements along Paleozoic faults. This information should be taken into account during selection of building areas.
[en] The present work investigates on the influence of small geometrical defects on the behavior of slender rigid blocks. A comprehensive experimental campaign was carried out on one of the shake tables of CEA/Saclay in France. The tested model was a massive steel block with standard manufacturing quality. Release, free oscillations tests as well as shake table tests revealed a non-negligible out-of-plane motion even in the case of apparently plane initial conditions or excitations. This motion exhibits a highly reproducible part for a short duration that was used to calibrate a numerical geometrically asymmetrical model. The stability of this model when subjected to 2 000 artificial seismic horizontal bidirectional signals was compared to the stability of a symmetrical one. This study showed that the geometrical imperfections slightly increase the rocking and overturning probabilities under bidirectional seismic excitations in a narrow range of peak ground acceleration. (authors)
[en] Full text: CMP data resolution and wave pattern analysis has been conducted with objective to apply seismic stratigraphic interpretation for seismic survey conducted in the Central Hadramuta.Seismic data resolution is one of important implication while seismic stratigraphic interpretation.Wireline data derived from available wells (Gabrhood-1, Wadi Sana-1 Washa-1) have been compared to those of seismic sections shot across these wells with objective to determine seismic data resolution.Both Fresnel zone and wavelength dimensions have been verified through well velocity data.Elastic wave frequency range derived from those sections indicates that Central Hadramuta formations are characterized by frequency range around 40-70 Hz,which diminishes down to 10 Hz with depth.Velocities of intermediate formations between Fartag suite and basement have been averaged, with proper seismic attributes typical for respective formations were used to define seismic wavelength and Fresnel zone radii.Available data analysis indicates that seismic wavelength at the sequence top portion in Fartag suite (arrival time 0.3-0.6 ms) is around 35 m length, whereas it increases 10 times to achieve up to 350 m within carbonate formation (arrival time is over 1.6-1.7 ms).The adequate pattern has been observed for the Fresnel zone which radii amount to 170m and 1650-1700 m at the Fartag suite top and carbonate formation respectively.An attached figure shows that there is a systematic trend associated with Fresnel zone increment axcept of Gishen suite occurrence depth where velocity variation is insignificant within the terrigenous rocks.Analysis of consistent primaries derived from time-sections shot within Gabrhood, Wadi Sana and Washa areas indicate that variability of primary wavelets below the Fartaga horizon can be caused by the following factors:1.Wavelet signature change with offset due to incident angle increment as well as dependent on the stacking formation thickness relationship and investigation depth;2.Internal heterogeneity of the target horizons-heterogeneity dimension,faulting pattern and forth on;3.Change of incident pp pulse signature caused by unstable excitation and receiver site conditions;4.Subjective factors associated with geophysical signal analyst's skill used while processing.Each of these factors should be considered and studied separately,as some of them being taken into account and precluded would facilitate to improve seismic data quality and make seismic-stratigraphic interpretation easier.
[en] During the development of new seismic data processing methods, the verification of potential events and associated signals can present a nontrivial obstacle to the assessment of algorithm performance, especially as detection thresholds are lowered, resulting in the inclusion of significantly more anthropogenic signals. Here, we present two 14 day seismic event catalogs, a local–scale catalog developed using data from the University of Utah Seismograph Stations network, and a global–scale catalog developed using data from the International Monitoring System. Each catalog was built manually to comprehensively identify events from all sources that were locatable using phase arrival timing and directional information from seismic network stations, resulting in significant increases compared to existing catalogs. Here, the new catalogs additionally contain challenging event sequences (prolific aftershocks and small events at the detection and location threshold) and novel event types and sources (e.g., infrasound only events and long–wall mining events) that make them useful for algorithm testing and development, as well as valuable for the unique tectonic and anthropogenic event sequences they contain.
[en] A minimum 1-D seismic velocity model for routine seismic event location purposes was determined for the area of the western Barents Sea, using a modified version of the VELEST code. The resulting model, BARENTS16, and corresponding station corrections were produced using data from stations at regional distances, the vast majority located in the periphery of the recorded seismic activity, due to the unfavorable land–sea distribution. Recorded seismicity is approached through the listings of a joint bulletin, resulting from the merging of several international and regional bulletins for the region, as well as additional parametric data from temporary deployments. We discuss the challenges posed by this extreme network-seismicity geometry in terms of velocity estimation resolution and result stability. Although the conditions do not facilitate the estimation of meaningful station corrections at the farthermost stations, and even well-resolved corrections do not have a convincing contribution, we show that the process can still converge to a stable velocity average for the crust and upper mantle, in good agreement with a priori information about the regional structure and geology, which reduces adequately errors in event location estimates.