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Hirokazu Iemura Touraj Taghikhany Sarvesh K. Jain 《Bulletin of Earthquake Engineering》2007,5(1):85-103
Seismic isolation is one of the effective methods to protect equipments. It helps to keep seismic response accelerations in
equipment below its allowable limits. Among different types of isolation systems, the combination of restoring spring and
slider, also called as resilient sliding isolation (RSI) system, is the one which has been effectively used for protection
of equipment. Principal design parameters for this type of isolation system are period of system (stiffness of spring) and
friction coefficient of slider. There may be number of combinations of these design parameters which can enable the isolated
equipment to remain functional during and after the predicted seismic event. The optimum design of RSI system can be considered
as the one which maintains the response acceleration in the equipment below its allowable limit and at the same time keeps
the relative displacement between floor and the equipment to the minimum. This study deals with optimum design of resilient
sliding system. First the RSI system is modeled analytically by (i) precise and (ii) simplified SDOF models. The accuracy
of the model is then validated by shaking table tests. The validated simplified SDOF model is then used to determine optimum
design parameters for different levels of allowable accelerations. Results show that the optimum period decreases and the
optimum friction coefficient increases with higher allowable acceleration. 相似文献
2.
Impact of major organophosphate pesticides used in agriculture to surface water and sediment quality (Southern Caspian Sea basin,Haraz River) 总被引：3，自引：3，他引：0
Touraj Nasrabadi Gholamreza Nabi Bidhendi Abdolreza Karbassi Peter Grathwohl Nasser Mehrdadi 《Environmental Earth Sciences》2011,63(4):873-883
Organophosphate pesticides are compounds that are not only toxic to both humans and wildlife but also difficult to degrade
under natural environmental conditions. In Iran, agricultural practices are strongly dependent on the use of pesticides due
to climatic and soil conditions, thus posing a potential risk to groundwater quality standards. Evaluating the concentration
of organophosphate pesticides namely diazinon, fenitrothion, dichlorvos, ethion, profenofos, malathion and azinphos methyl
in water samples in May (low precipitation rate), December (high precipitation rate) as well as the concentration in sediments
along the Haraz River is taken into consideration in this study. Generally the pesticides concentration in water samples are
relatively higher in May in comparison with that in December; this fact may be due to two major reasons: the first reason
is attributed to the prompt raining after the treatment period of most orchards and dry farming lands that will terminate
in more wash out of such pesticides towards the branches and main river channel, while the second reason may be considered
as the less river water dilution rate in May because of lower precipitation rate. Furthermore, the relatively higher concentrations
in downstream stations may be contributed to more intensified agricultural (specially rice paddies), urban and rural land
uses in this region in comparison with upstream areas which contain mainly dry farming, grazing lands and orchards with relatively
lower loads of pesticides. Additionally, as the Henry’s law constant of all pesticides considered in this study are relatively
low, volatilization may not be regarded as an important route of dissipation. Diazinon, azinphos methyl and dichlorvos showed
the highest water concentrations in comparison with other pesticides that may be justified by their extended use within the
basin during last decades. Based on the chemical properties as well as remarkably higher values in sediment samples in comparison
with water ones, it is concluded that the two pesticides, ethion and fenitrothion, persist in the environment due to non-degradable
tendencies. Although the concentration of mentioned pesticides is not so high in the water samples, more precautions must
be considered in their future use. Regarding the sorption coefficient variation alongside the river, the higher values in
upstream and central parts may be attributed to the higher potential of different types of erosion regarding deeper slopes
and also sand, gravel and carbonate mining activities at the banks and also river bed in such regions which is considered
as an anthropogenic disturbance. In case of central parts, in addition to mentioned reasons, the existence of coal outcrops
in the geologic texture of the study area may also be considered as a key role in augmentation of the sorption coefficient.
Finally, the dominant clayey and loamy soils containing more organics may be attributed as the major reason of sorption tendency
in downstream. 相似文献
3.
Near-field ground-motion records affected by directivity may show unusual features in the signal resulting in low-frequency cycle pulses in the velocity time history. Current probabilistic seismic hazard analysis (PSHA) is not able to predict such effects well; recent studies thus have proposed modified frameworks to incorporate pulse effect in modified PSHA. This paper attempts to carry out the seismic hazard mapping of Tabriz city according to modified and ordinary PSHA for different return periods. Tabriz, located in northwest of Iran, is situated in the vicinity of the North Tabriz Fault, which is one of the major seismogenic faults. Disaggregation results indicate that including pulse-like effects in PSHA, increases the relative contribution of close distances and small epsilons (?). Another major probable result is the high contribution of pulse periods close to spectral period. The contributions to each earthquake scenario at long-period spectral acceleration shift to larger magnitudes with including the pulse effects. 相似文献
4.
Ghorbanzadeh Mohammad Khoshnoudian Faramarz Taghikhany Touraj 《Bulletin of Earthquake Engineering》2022,20(2):997-1026
Bulletin of Earthquake Engineering - The main objective of this study is to employ a probabilistic approach to determine the appropriate value of the strong column-weak beam ratio (SCWBR) for three... 相似文献
5.
Touraj Nasrabadi Gholamreza Nabi Bidhendi Abdolreza Karbassi Nasser Mehrdadi 《Environmental Earth Sciences》2010,59(5):1111-1117
The Haraz River flows northwards through the Iranian Alborz mountains in the central region of Mazandaran province and empties
into the Caspian Sea. This area has been a rich source of minerals from times immemorial. About 45 mines (coal, limestone,
sand and gravel, etc.) have been operational for the last eight decades. Towards the estuary, the river receives a discharge
of industrial, agricultural and urban wastes. Eight sediment samples from the Haraz River and its main tributaries were collected
and analyzed for base metals as well as Sr and Fe. The chemical partitioning of metals (Cu, Zn, As, Cd, Pb, Fe, Ni, Cr, Co
and Sr) in each sample was determined in four fractions (acid-soluble, reducible, oxidizable and residual). The total content
of each metal was also determined. The results showed relatively higher concentrations of Cd, As, Sr and Pb in comparison
to that of shale. However, based on the chemical partitioning of metals, it is found that Pb, Co, Cd and Sr are the most mobile
metals. In spite of the high As concentrations in sediments, it is not likely that this element is a major hazard for the
aquatic environment, since it is found mainly in the residual fraction. Cadmium is the metal that showed the highest percentages
in the acid-soluble fraction (the most labile) and the lowest in the residual fraction. However, Fe, Cr and Ni are present
in the greatest percentages in the residual fraction, which implies that these metals are strongly linked to the sediments. 相似文献
6.
Hirokazu Iemura Touraj Taghikhany Yoshikazu Takahashi Sarvesh K. Jain 《地震工程与结构动力学》2005,34(15):1777-1797
In this study, a series of shaking table tests are carried out on scaled models of two seismically isolated highway bridges to investigate the effect of rocking motion and vertical acceleration on seismic performance of resilient sliding isolators. In addition, performance of RSI is compared with system having solely natural rubber bearings. Test results show that variation of normal force on sliders due to rocking effect and vertical acceleration makes no significant difference in response of RSI systems. In addition, analytical response of prototype isolated bridge and the model used in experiments is obtained analytically by using non‐linear model for isolation systems. It is observed that for seismically isolated bridges, dynamic response of full‐scale complex structures can be predicted with acceptable accuracy by experiments using a simple model of the structure. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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