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11.
A series of tests on three full-scale substandard exterior beam-column joints were performed to investigate the efficiency of the proposed retrofit configuration, which is the use of externally applied post-tensioned shape memory alloy (SMA) bars. A major group of structural deficiencies resulting from lack of shear reinforcement in the joint, use of low strength concrete and plain round bars were taken into account in the construction of test specimens. While the reference specimen represents the as-built subassembly, the other two were retrofitted by the post-tensioned SMA and steel bars to compare the contribution of superelastic and conventional material on the response. The specimens were exposed to quasi-static cyclic loading up to 8% drift ratio to simulate an intensive level of seismic hazard. The reference specimen underwent a brittle shear failure as excessive cracks mostly concentrated in the joint panel while there was almost no damage in the rest of the RC components. A joint failure with enhanced response quantities was observed in the specimen retrofitted by post-tensioned steel bars. The specimen incorporating the retrofit solution via post-tensioned SMA bars was capable of performing an adequate performance and promoting minimization of the damage in the joint panel, which results in more ductile behavior. The hysteretic response of the SMA retrofitted specimen was validated with a refined numerical model in ATENA Science software. Experimentally observed response was also verified by an analytical model based on fracture mechanics considering the nonlinear behavior of plain concrete under tension. Due to inherent uncertainties in material constitutive laws, the analytical model was evolved to a stochastic level to propose a more advanced model for estimating the capacity of the reference and retrofitted joint. It is found that the experimental results were within the prominent range of Probability Density Functions (i.e. mean ± 1 SD) of the estimated joint tensile stress especially for the shear damaged specimens. 相似文献
12.
Ocean Dynamics - The sea surface temperature (SST) variability is clearly affected by global climate patterns, which involve large-scale ocean-atmosphere fluctuations similar to the El... 相似文献
13.
This study evaluates the performance of two widely used GRACE solutions (CNES/GRGS RL02 and CSR RL04) in deriving annual and
inter-annual water mass variations in the Black Sea for the period 2003–2007. It is demonstrated that the GRACE derived water
mass variations in the Black Sea are heavily influenced by the leakage of hydrological signals from the surrounding land.
After applying the corresponding correction, we found a good agreement with water mass variations derived from steric-corrected
satellite altimetry observations. Both GRACE and altimetry show significant annual water mass variations of roughly 7 cm amplitude
peaking in May and a semi-annual signal of roughly 3 cm peaking in June and in December. The amplitude of the annual water
mass signal varies significantly from year to year and is significantly larger during 2004–2006 than in 2003 and 2007. This
is also in agreement with the steric corrected altimetry. 相似文献
14.
Ali Kiliçoğlu Ahmet Direnç Hasan Yildiz Murat Bölme Bahadir Aktuğ Mehmet Simav Onur Lenk 《Studia Geophysica et Geodaetica》2011,55(4):557-578
Turkish regional geoid models have been developed by employing a reference earth gravitational model, surface gravity observations
and digital terrain models. The gravimetric geoid models provide a ready transformation from ellipsoidal heights to the orthometric
heights through the use of GPS/leveling geoid heights determined through the national geodetic networks. The recent gravimetric
models for Turkish territory were computed depending on OSU91 (TG-91) and EGM96 (TG-03) earth gravitational models. The release
of the Earth Gravitational Model 2008 (EGM08), the collection of new surface gravity observations, the advanced satellite
altimetry-derived gravity over the sea, and the availability of the high resolution digital terrain model have encouraged
us to compute a new geoid model for Turkey. We used the Remove-Restore procedure based on EGM08 and applied Residual Terrain
Model (RTM) reduction of the surface gravity data. Fast Fourier Transformation (FFT) was then used to obtain the residual
quasigeoid from the reduced gravity. We restored the individual contributions of EGM08 and RTM to the whole quasi-geoid height
(TQG-09). Since the Helmert orthometric height system is adopted in Turkey, the quasi-geoid model (TQG-09) was then converted
to the geoid model (TG-09) by making use of Bouguer gravity anomalies and digital terrain model. After all we combined a gravimetric
geoid model with GPS/leveling geoid heights in order to obtain a hybrid geoid model (THG-09) (or a transformation surface)
to be used in GPS applications. The RMS of the post-fit residuals after the combination was found to be ± 0.95 cm, which represents
the internal precision of the final combination. And finally, we tested the hybrid geoid model with GPS/leveling data, which
were not used in the combination, to assess the external accuracy. Results show that the external accuracy of the THG-09 model
is ± 8.4 cm, a precision previously not achieved in Turkey until this study. 相似文献
15.
16.
Sedat İnan Kadriye Ertekin Cemil Seyis Şakir Şimşek Furkan Kulak Aynur Dikbaş Onur Tan Semih Ergintav Rahşan Çakmak Ahmet Yörük Muhiddin Çergel Hakan Yakan Hüseyin Karakuş Ruhi Saatçilar Zafer Akçiğ Yıldız İravul Bekir Tüzel 《Acta Geophysica》2010,58(5):767-813
Warm and hot spring water as well as soil gas radon release patterns have been monitored in the Aegean Extensional Province of Western Turkey, alongside regional seismic events, providing a multi-disciplinary approach. In the study period of 20 months, seven moderate earthquakes with M L between 4.0 and 4.7 occurred in this seismically very active region; two earthquakes with magnitude 5.0 also occurred near the study area. Seismic monitoring showed no foreshock activity. By contrast, hydro-geochemical anomalies were found prior to these seismic events, each lasting for weeks. The anomalies occurred foremost in conjunction with dip-slip events and seem to support the dilatancy and water diffusion hypothesis. Increased soil gas radon release was recorded before earthquakes associated with strike-slip faults, but no soil radon anomalies were seen before earthquakes associated with dip-slip faults. Geochemical anomalies were also noticeably absent at some springs throughout the postulated deformation zones of impending earthquakes. The reason for this discrepancy might be due to stress/strain anisotropies. 相似文献
17.
The oxidation of pyrite results in sulphate concentrations from 1,300 to 2,000 mg/l in the dump water of the open cast mine
Inden, which is located in Germany. Under near-neutral pH and reduced redox conditions, precipitation of siderite (FeCO3) retains up to 85% of the pre-liberated ferrous iron, so that iron concentrations in the dump water are relatively low as
compared to the concentrations of sulphate. The highly mineralised dump water will enter the aquifer system northwards of
Inden during the next centuries. This area is used intensely for water extraction. Model calculations show that there will
be no problem of acidification in the adjacent aquifer system and, therefore, no problem of high heavy metal concentrations
during the next centuries. The most important problem will be high sulphate concentrations in the groundwater. Besides dispersion
and diffusion, there are no chemical mechanisms that lower the sulphate concentrations downstream. On the basis of the simulations,
sulphate plumes of about 1–2 km in width and up to 15 km in length are expected. Within the core of these plumes, sulphate
concentrations will be above the drinking water limits. 相似文献
18.
Lynn Margulis Betsey Dexter Dyer Grosovsky John F. Stolz Elizabeth J. Gong-Collins Susan Lenk Dorothy Read Alejandro Lpez-Corts 《Precambrian Research》1983,20(2-4)
The live and sedimentary components of the flat laminated microbial mat at Laguna Figueroa have been studied since the late sixties. This paper reports the observation and isolation of a variety of micro-organisms, both prokaryotes and eukaryotes. The microbes were taken from the flat laminated mats submerged under at least one meter of water due to the spring rains of 1979 and 1980. Both in situ and enrichment culture observations were made using light and electron microscopic techniques. New strains of the following microbes are reported here: Bacillus megaterium, Bacillus licheniformis, Arthrobacter simplex and Paratetramitus jugosus. Several pseudomonads were isolated, some of which form distinctive subsurface colonial structures. Regular distinctive colony morphologies and desiccation resistant cysts were often observed, several types of which grow to characteristically large sizes and resemble objects found in the pre-Phanerozoic fossil record.Some colonies of manganese oxidizing bacilli and other bacteria are reminiscent of microfossils of the 2 Ga-old Gunflint Iron formation such as Metallogenium, Eosphaera tyleri, Eoastrion and Huronispora. Some manganese oxidizing bacteria form colonial structures that might be mistaken for individual organisms in the tens to hundreds of microns size range. The diversity of microbial structures, including those with preservation potential, must be kept in mind when interpreting the microfossil record. 相似文献
19.
Measuring streambank erosion due to ground water seepage: correlation to bank pore water pressure,precipitation and stream stage 总被引：1，自引：0，他引：1
Garey A. Fox Glenn V. Wilson Andrew Simon Eddy J. Langendoen Onur Akay John W. Fuchs 《地球表面变化过程与地形》2007,32(10):1558-1573
Limited information exists on one of the mechanisms governing sediment input to streams: streambank erosion by ground water seepage. The objective of this research was to demonstrate the importance of streambank composition and stratigraphy in controlling seepage flow and to quantify correlation of seepage flow/erosion with precipitation, stream stage and soil pore water pressure. The streambank site was located in Northern Mississippi in the Goodwin Creek watershed. Soil samples from layers on the streambank face suggested less than an order of magnitude difference in vertical hydraulic conductivity (Ks) with depth, but differences between lateral Ks of a concretion layer and the vertical Ks of the underlying layers contributed to the propensity for lateral flow. Goodwin Creek seeps were not similar to other seeps reported in the literature, in that eroded sediment originated from layers underneath the primary seepage layer. Subsurface flow and sediment load, quantified using 50 cm wide collection pans, were dependent on the type of seep: intermittent low‐flow (LF) seeps (flow rates typically less than 0·05 L min?1), persistent high‐flow (HF) seeps (average flow rate of 0·39 L min?1) and buried seeps, which eroded unconsolidated bank material from previous bank failures. The timing of LF seeps correlated to river stage and precipitation. The HF seeps at Goodwin Creek began after rainfall events resulted in the adjacent streambank reaching near saturation (i.e. soil pore water pressures greater than ?5 kPa). Seep discharge from HF seeps reached a maximum of 1·0 L min?1 and sediment concentrations commonly approached 100 g L?1. Buried seeps were intermittent but exhibited the most significant erosion rates (738 g min?1) and sediment concentrations (989 g L?1). In cases where perched water table conditions exist and persistent HF seeps occur, seepage erosion and bank collapse of streambank sediment may be significant. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
20.
The scope of this paper is to develop the nonlinear meta-models for seakeeping behaviour, considering the fishing vessels. These models are intended to be inserted either in a multiattribute design selection process or in a comprehensive multiobjective optimization procedure. For this purpose, seakeeping data of fishing vessels in regular head waves are used to develop meta-models of transfer functions of heave, pitch and vertical acceleration by nonlinear analysis. A home-made software considers two databases; the first is composed by the ship dimensions and coefficients of fishing vessels, and the second is their ship motion data obtained by employing a strip-theory calculation. The meta-models are proposed to predict the vertical motion characteristics for given ranges of speed and wave length during the concept design stage. The independent variables are hull size (Δ), main dimensions (L, B, T), and some hydrostatic parameters (CWP, CVP, LCB, LCF, etc.). The results estimated by the software show good correspondences with the ones achieved by direct computations. The study provides additional insight on the influence of hull form parameters on seakeeping performance of small vessels having form properties and parametric range corresponding to the investigated vessels. 相似文献