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Asynchronous seismic analysis of concrete-faced rockfill dams including dam-reservoir interaction

Bayraktar A. | Haciefendioglu K. | Muvafik M.

Article | 2005 | Canadian Journal of Civil Engineering32 ( 5 ) , pp.940 - 947

Seismic response of concrete-faced rockfill (CFR) dams subjected to asynchronous base excitation is determined by considering dam-reservoir interaction. The equations of motion of the coupled system are obtained using the Lagrangian approach, and the surface sloshing motion is included in the finite element formulation. Torul dam constructed in the city, Gumushane, Turkey, is selected as a numerical example, and its material properties are considered in the analysis. The dam-reservoir interaction system is modelled using the Lagrangian (displacement-based) fluid and solid-quadrilateral-isoparametric finite elements. The east-west co . . .mponent of Erzincan earthquake, which occurred on 13 March 1992, recorded near the region of the dam is used as a ground motion. Propagation velocities of the seismic wave are chosen as 1000 m/s, 3000 m/s, and infinite. Stresses are calculated for empty and full reservoir cases and compared with each other. © 2005 NRC Canada Daha fazlası Daha az

Earthquake response of reinforced concrete frame structures subjected to rebar corrosion

Yüksel I. | Coşkan S.

Article | 2013 | Earthquake and Structures5 ( 3 ) , pp.321 - 341

This paper investigates earthquake response of reinforced concrete regular frames subjected to rebar corrosion. A typical four-story reinforced concrete frame is designed according to Turkish Earthquake Code in order to examine earthquake response. Then different levels of rebar corrosion scenarios are applied to this frame structure. The deteriorated conditions as a result of these scenarios are included loss in cross sectional area of rebar, loss of mechanical properties of rebar, loss in bond strength and variations in damage limits of concrete sections. The frame is evaluated using a nonlinear static analysis in its sound as wel . . .l as deteriorated conditions. The rebar corrosion effect on the structural response is investigated by comparing the response of the frame in each scenario with respect to the sound condition of the frame. The results shows that the progressive deterioration of the frame over time cause serious reductions on the base shear and top displacement capacity and also structural ductility of the corroded frames. The propagation time, intensity, and extensity of rebar corrosion on the frame are important parameters governing the effect of rebar corrosion on earthquake response of the frame. ©2013 Techno-Press, Ltd Daha fazlası Daha az

Response and stability of underground structures in rock mass during earthquakes

Aydan Ö. | Ohta Y. | Geniş M. | Tokashiki N. | Ohkubo K.

Article | 2010 | Rock Mechanics and Rock Engineering43 ( 6 ) , pp.857 - 875

Underground structures are well known to be earthquake resistant. However, the recent earthquakes showed that underground structures are also vulnerable to seismic damage. There may be several reasons such as high ground motions and permanent ground movements. This study attempts to describe various forms of damage to underground structures such as tunnels, caverns, natural caves and abandoned mines during major earthquakes. Results of various model tests on shaking table are also presented to show the effect of ground shaking on the response and collapse of underground structures in continuum and discontinuum. Furthermore, some emp . . .irical equations are proposed to assess the damage to underground structures, which may be useful for quick assessments of possible damage. © 2010 Springer-Verlag Daha fazlası Daha az

Seismo-ionospheric precursors of strong sequential earthquakes in Nepal region

Ulukavak M. | Inyurt S.

Article | 2020 | Acta Astronautica166 , pp.123 - 130

Global Navigation Satellite Systems record the total electron content via their receivers, and total electron content measurements have become popular with the requirement for capturing any ionospheric abnormalities prior to earthquake. Based on space weather conditions, the solar activity and geomagnetic activity indices are critical to monitor the total electron contents in the ionosphere. This study aimed to investigate the ionospheric variations induced by six sequential earthquakes in Nepal in 2015 with magnitude higher than 6.0, examine the total electron content data from Global Ionosphere Maps and Global Positioning Systems . . .and analyze the contributing factors to the abnormal total electron content levels affected by space environment and geomagnetic activity status. We performed moving median analysis for 15 days to determine the pre- and post-earthquake abnormalities. With the static and dynamic time analysis, we concluded that there was likelihood for positive or negative anomalies, earthquake-induced ionospheric anomalies occurred on the previous day or up to six days earlier and even had potentiality for successive earthquakes. Furthermore, the data used in the analysis can be divided into two groups: Global Ionosphere Maps Total Electron Content and Global Positioning System Total Electron Content variations. LHAZ International Global Navigation Satellite System Service station from which we obtained these was close to the earthquakes’ epicenter. We studied three indices, such as geomagnetic storm index (K-planetary), geomagnetic activity index, and solar activity index, depending on space climate and discussed what factors can be influential in this disaster. Hence, we suggest that the earthquake may account for a typical variation in Global Ionosphere Maps Total Electron Content data as well as Global Positioning System Total Electron Content as solar activities and geomagnetic storms leading to abnormalities in the ionosphere. © 2019 IA Daha fazlası Daha az

Assessment of the dynamic stability of the portals of the Dorukhan tunnel using numerical analysis

Geniş M.

Article | 2010 | International Journal of Rock Mechanics and Mining Sciences47 ( 8 ) , pp.1231 - 1241

Instability problems may arise during the construction and operation of tunnels depending on the quality of the rock mass. In particular, determining instability problems at the portals of a tunnel is of utmost importance during excavation and operation of the tunnel. Slope instability and rockfalls are the most frequent instability problems that may be encountered at tunnel portals. Such instability problems can be triggered by dynamic effects such as earthquakes, blasting, etc. This study investigates the stability of the portals of the Dorukhan Tunnel connecting the provinces of Zonguldak and Bolu in the close vicinity of the Nor . . .th Anatolian Fault Zone (NAFZ), which is a well-known strike-slip 1500. km long fault. The effect of an earthquake that may occur in the NAFZ on the extent of failure has also been studied by numerical analyses. In the analyses, a three-dimensional dynamic analysis computer code, based on the finite difference method, has been used. According to results of the dynamic numerical analyses, the Devrek portal was found to be more stable than the Mengen portal. Moreover, it was found that, for acceleration values of dynamic wave higher than 0.5. g, tunnel portal slopes and the areas as far as 20-50. m from the tunnel entrance may suffer serious damage. Wave propagation perpendicular to the tunnel axis was established to cause more damage around the openings and in the portal slopes as wave compared to propagation parallel to the tunnel axis. © 2010 Elsevier Ltd Daha fazlası Daha az

Earthquake behavior of reinforced concrete frames subjected to rebar corrosion

Yüksel İ. | Coşkan S.

Conference Object | 2013 | Sustainable Construction Materials and Technologies2013-August , pp.1231 - 1241

The aim of this paper is to investigate the earthquake behaviour of reinforced concrete frames subjected to rebar corrosion. A typical two-bay, four-story reinforced concrete (RC) frame is designed. Two different rebar corrosion scenarios and a design spectrum are selected. The deteriorated condition in these scenarios are included which are loss in diameter of rebar, changes of mechanical properties of reinforcement steel bars, bond strength and changes in damage limits of concrete sections. The RC frame is evaluated using a nonlinear static analysis method in sound condition as well as deteriorated conditions. The rebar corrosion . . .effect on the global level is investigated by comparing the responses of each scenario with respect to the response of sound condition of the frame. The result shows that the progressive deterioration of frames over time can cause serious reductions on the load-bearing capacity. Hence the overall seismic behaviour of the frame is adversely affected. © 2013 Sustainable Construction Materials and Technologies. All rights reserved Daha fazlası Daha az

Determination of the 30-year creep trend on the Ismetpaşa segment of the North Anatolian Fault using an old geodetic network

Kutoglu H.S. | Akcin H.

Article | 2006 | Earth, Planets and Space58 ( 8 ) , pp.937 - 942

The Ismetpaşa segment of the North Anatolian Fault was ruptured during both the 1944 (Mw = 7.2) Gerede and 1951 (Mw = 6.9) Kurşunlu earthquakes. The field studies carried out in the aftermath of these two major earthquakes showed that the Ismetpaşa segment had experienced a creep movement. To monitor the surface creep, a geodetic network with six control points was established on the segment. This network was observed three times - in 1972, 1982 and 1992. Based on our evaluations of those observations, the creep on the segment was geodetically determined to be 1.02 cm/year (1972-1982) and 0.93 cm/year (1982-1992) respectively. In 19 . . .99, the North Anatolian Fault experienced two major shocks - the Mw = 7.4 Gölcük and Mw = 7.2 Düzce earthquakes - both on the western part of the Ismetpaşa fault. Using the global positioning system, our surveying team observed the network one more time in 2002 to assess whether these earthquakes affected the creep of the Ismetpaşa segment, or not. The evaluation of the observations revealed a creep of 0.78 cm/year for the period 1992-2002. This result reveals that the creep of the segment has decreased in a linear fashion between 1972 and 2002 and that it had not been triggered by the Gölcük and Düzce earthquakes. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB Daha fazlası Daha az

Statistical characteristics of seismo-ionospheric GPS TEC disturbances prior to global Mw >= 5.0 earthquakes (1998-2014)

Shah, Munawar | Jin, Shuanggen

Article | 2015 | JOURNAL OF GEODYNAMICS92 , pp.42 - 49

Pre-earthquake ionospheric anomalies are still challenging and unclear to obtain and understand, particularly for different earthquake magnitudes and focal depths as well as types of fault. In this paper, the seismo-ionospheric disturbances (SID) related to global earthquakes with 1492 Mw >= 5.0 from 1998 to 2014 are investigated using the total electron content (TEC) of GPS global ionosphere maps (GIM). Statistical analysis of 10-day TEC data before global Mw >= 5.0 earthquakes shows significant enhancement 5 days before an earthquake of Mw >= 6.0 at a 95% confidence level. Earthquakes with a focal depth of less than 60 km and Mw > . . .= 6.0 are presumably the root of deviation in the ionospheric TEC because earthquake breeding zones have gigantic quantities of energy at shallower focal depths. Increased anomalous TEC is recorded in cumulative percentages beyond Mw-5.5. Sharpness in cumulative percentages is evident in seismo-ionospheric disturbance prior to Mw >= 6.0 earthquakes. Seismo-ionospheric disturbances related to strike slip and thrust earthquakes are noticeable for magnitude Mw6.0-7.0 earthquakes. The relative values reveal high ratios (up to 2) and low ratios (up to -0.5) within 5 days prior to global earthquakes for positive and negative anomalies. The anomalous patterns in TEC related to earthquakes are possibly due to the coupling of high amounts of energy from earthquake breeding zones of higher magnitude and shallower focal depth. (C) 2015 Elsevier Ltd,. All rights reserved Daha fazlası Daha az

Statistical characteristics of seismo-ionospheric GPS TEC disturbances prior to global Mw?5.0 earthquakes (1998-2014)

Shah M. | Jin S.

Article | 2015 | Journal of Geodynamics92 , pp.42 - 49

Pre-earthquake ionospheric anomalies are still challenging and unclear to obtain and understand, particularly for different earthquake magnitudes and focal depths as well as types of fault. In this paper, the seismo-ionospheric disturbances (SID) related to global earthquakes with 1492. Mw. ?. 5.0 from 1998 to 2014 are investigated using the total electron content (TEC) of GPS global ionosphere maps (GIM). Statistical analysis of 10-day TEC data before global Mw. ?. 5.0 earthquakes shows significant enhancement 5 days before an earthquake of Mw. ?. 6.0 at a 95% confidence level. Earthquakes with a focal depth of less than 60 km and . . .Mw. ?. 6.0 are presumably the root of deviation in the ionospheric TEC because earthquake breeding zones have gigantic quantities of energy at shallower focal depths. Increased anomalous TEC is recorded in cumulative percentages beyond Mw. = 5.5. Sharpness in cumulative percentages is evident in seismo-ionospheric disturbance prior to Mw. ?. 6.0 earthquakes. Seismo-ionospheric disturbances related to strike slip and thrust earthquakes are noticeable for magnitude Mw6.0-7.0 earthquakes. The relative values reveal high ratios (up to 2) and low ratios (up to -0.5) within 5 days prior to global earthquakes for positive and negative anomalies. The anomalous patterns in TEC related to earthquakes are possibly due to the coupling of high amounts of energy from earthquake breeding zones of higher magnitude and shallower focal depth. © 2015 Elsevier Ltd Daha fazlası Daha az

Assessment of dynamic response and stability of an abandoned room and pillar underground lignite mine

Geniş M. | Aydan Ö.

Conference Object | 2008 | 12th International Conference on Computer Methods and Advances in Geomechanics 20085 , pp.3899 - 3906

The authors have been involved with some abandoned mines in the Tokai Region of Japan and they have been investigating their performance and responses in the long term and during earthquakes. In this article, some examples of stability problems observed in areas of abandoned lignite mines during earthquakes are summarized. Two-dimensional model tests of abandoned room and pillar mines are described and vibration characteristics and instability modes are briefly presented. Ground amplification is investigated at abandoned mine sites by using a series of finite element analyses. In the remaining part of the article, three-dimensional . . .elasto-plastic dynamic stress analyses are presented. In numerical solutions, analyses are performed by using harmonic ground motions. It is found that the ground motions with low amplitudes may also cause significant damage in the surrounding mass around the mine and ground surface, depending on rock mass properties Daha fazlası Daha az

The effect of seasonally frozen soil on stochastic response of elevated water tank under random excitation

Haciefendioglu K. | Kartal M.E. | Karaca Z.

Article | 2013 | Stochastic Environmental Research and Risk Assessment27 ( 4 ) , pp.807 - 818

Significant seismic events have occurred around the world during winter months in regions where cold temperatures cause ground freezing. Current seismic design practice does not address the effects of cold temperatures in the seasonally frozen areas. Since many elevated water tank structures in cold regions are located in seismic active zones, determining the effect of seasonally frozen soil on the stochastic response of elevated water tank structures subjected to random seismic excitation is an important structural consideration. A three dimensional finite element model, which considers viscous boundaries, was built up to obtain th . . .e stochastic seismic behavior of an elevated water tank-fluid-soil interaction system for frozen soil condition. For this model, the power spectral density function represents random ground motion applied to each support point of the three dimensional finite element model of the elevated water tank-fluid-soil interaction system. Numerical results show that the soil temperature affects the seismic response of the elevated water tank; whereas the variation in the thickness of the frozen soil causes insignificant changes on the response. In addition, the effect of the variation in water tank's fullness on the stochastic response of the coupled system is investigated in the study. As a result, the seasonal frost changes the foundation soil stiffness and may impact seismic behavior of the water tank. © 2012 Springer-Verlag Daha fazlası Daha az

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