توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱EFFECT OF WELL– KNOWN CHARACTERISTICS OF NEAR FAULT GROUND MOTION ON SEISMIC RESPONSE OF BRIDGES
اطلاعات انتشار: دومین کنفرانس بین المللی پیشرفتهای اخیر در مهندسی راه آهن، سال
تعداد صفحات: ۸
Ground motion records from recent earthquakes have shown that near–fault records are different from far–fault ground motions. Failures of modern engineering bridges, observed within the near–fault region in recent earthquakes, such as 1999 chi–chi, revealed the vulnerability of existing bridges against pulse–type ground motions. Although current seismic design criteria consider this damaging effects by amplifying the design spectra, this methods do not adequately represent consequence of well–known characteristics of near–fault ground motion on seismic response of bridges.<\div>

۲NEAR– FIELD EARTHQUAKES EFFECT ON HORIZONTAL AND VERTICAL RESPONSE SPECTRA
اطلاعات انتشار: دومین کنفرانس بین المللی پیشرفتهای اخیر در مهندسی راه آهن، سال
تعداد صفحات: ۷
Strong earthquakes of the past decade have revealed destructive effects of motions in vicinity of faults. Hence, in this paper, characteristics of near field ground motions have been considered in horizontal and vertical directions. In this consideration, the record averages have been compared with Uniform Building Code (1997): International Conference of Building Officials, Structural Design Provisions (UBC97) and European Standard (2001): Design of Structures for Earthquake Resistance (Eurocode 8) spectra in 2 levels. In addition, the ratio of vertical to horizontal spectra has been computed and compared with the assumed value of 2\3 in some code provisions.<\div>

۳Ovaling deformations of circular urban tunnels under seismic wave propagation
اطلاعات انتشار: نهمین کنگره بین المللی مهندسی عمران، سال
تعداد صفحات: ۸
The urban tunnels under severe earthquake excitations are very important lifelines because of the number of facilities and the beneficiaries in progressive countries. Historically, underground facilities have experienced a lower rate of damage than surface structures. Nevertheles some underground structures have experienced significant damage in recent large earthquakes, including the 1995 Kobe, Japan earthquake, the 1999 Chi–Chi, Taiwan earthquake and the 1999 Kocaeli, Turkey earthquake.In This study the analytical solutions for the thrust and moment in the lining of a circular tunnel due to seismic induced ovaling deformation Is considered . The discrepancy among the existing solutions in the thrust and moment for interface with Different conditions is investigated . The analytical solutions are compared to numerical analyses using finite element method with Plaxis to validate which of the solutions providethe correct solution.The three circular tunnels with different thickness for finite element modeling have been developed .Comparison of the solution methods shows that the calculated forces and displacements are identical for the condition of full slip between the tunnel lining and ground. However, the calculated lining thrusts differ by an order of magnitude when assuming no–slip between the tunnel lining and the ground.<\div>

۴Effect of Triple Friction Pendulum Isolators and Supplemental Viscous Dampers on Seismic Isolated RC Buildings under Near–Fault Excitations
نویسنده(ها): ،
اطلاعات انتشار: کنفرانس بین المللی دستاوردهای نوین پژوهشی در مهندسی عمران، معماری و شهرسازی، سال
تعداد صفحات: ۷
The isolating system absorbs part of the earthquake energy before transferring it to the structure, by shifting the natural period of the isolated structure. This period shift results in a reduction in the inertial forces. It is clear that the effects of near–fault (NF) ground motions with large velocity pulses can bring the seismic isolation devices to critical working conditions. In this study, two three–dimensional RC buildings which are supported by TPB isolators are idealized. Various triple friction pendulum bearing configurations are selected for isolation systems. There are also viscous dampers to limit the excess deformation of isolators. Nonlinear time history analyses were performed by using Opensees to study the influence of supplemental dampers on structural responses such as isolator displacements and max drifts under ten near–fault ground motion records. The results show noticeable reduction in isolator displacement when using dampers. However, maximum drift rise considerably. Moreover by increasing the period range or reducing the damping ratio of isolation system maximum drift reduces but the displacement of isolators increase.<\div>

۵An experimental study on shear strengthening of RC lightweight deep beams using CFRP
اطلاعات انتشار: Journal of Rehabilitation in Civil Engineering، دوم،شماره۲، ۲۰۱۴، سال
تعداد صفحات: ۱۱
This paper presents the results of an experimental investigation on shear strength enhancement of reinforced concrete deep beams externally reinforced with fiber reinforced polymer (FRP) composites. A total of six deep beam specimens of two different classes, as–built (unstrengthened) and retrofitted were tested in the experimental evaluation program. Two composite systems namely carbon\epoxy laminates and carbon\epoxy sheets were used for retrofit evaluation. A comparative study of the experimental results with published analytical models, including the ACI 440 model, was also conducted in order to evaluate the different analytical models and identify the influencing factors on the shear behavior of FRP strengthened reinforced concrete deep beams. Experimental results indicated that the composite systems provided substantial increase in ultimate strength of strengthened beams as compared to the as–built beam specimen. The strength gain caused by the CFRP sheets was in the range of 30–58% Analytical Comparison indicated that the shear span–to–depth ratio (a\d) is an important factor that actively controls the shear failure mode of beam and consequently influences on the shear strength enhancement.

۶Probabilistic Assessment of PGA and UHS for Bojnurd city, the Capital of North Khorasan Province, Iran
اطلاعات انتشار: Journal of Seismology and Earthquake Engineering، چهاردهم،شماره۱، ۲۰۱۲، سال
تعداد صفحات: ۱۶
Probabilistic seismic hazard assessment (PSHA) of horizontal peak ground acceleration (PGA) and Uniform Hazard Spectra (UHS) on bedrock for different hazard levels is conducted in this study for Bojnurd city, the capital ofNorth Khorasan province, Iran. Therefore, all historical and instrumental earthquakes in a radius of 200 km of the center of Bojnurd city are gathered and after elimination of the aftershocks and foreshocks, the main earthquakes are identified in order to calculate the seismic parameters byKijko (2000)method. The seismotectonic model of the considered region and the seismic sources of the region have been modeled. Bojnurd city and its vicinity are meshed by 8 vertical and 11 horizontal lines. PGAs and UHS are calculated for all 88 points of the mesh using the logic tree method and different attenuation relationships with different weighted coefficients. These calculations are performed for two hazard levels of 10% and 2% probability of being exceeded in 50 years (hazard levels 1 and 2 respectively). Regional seismic hazard maps for PGAs andUHS for different locations ofBojnurd city and its vicinity are provided.

۷Retrofitting I–Beam to Double–I Built–up Column Connections Using Through Plates and T–Stiffeners
اطلاعات انتشار: Scientia Iranica، بيستم،شماره۶، ۲۰۱۳، سال
تعداد صفحات: ۱۹
Double–I built–up sections were extensively used in Iran according to the previous versions of Iranian building codes. Despite the recent developments in steel moment connections, based on studies for I–beam to H–shaped column connections, there are not enough documents available for I–beam to double–I built–up column connections. Recent studies have revealed that connections with double–I built–up columns exhibit different behaviors comparing to the connections with H–shaped columns. Due to excessive out–of–plane deformations of the cover plate in the non–retrofitted moment connections, they have semi–rigid behavior. The objective of this study is to build on previous studies and to investigate strain distribution pattern and load transfer mechanism in the retrofitted I–beam to double–I built–up column connections using through plates and T–stiffeners. In this paper, both horizontal and vertical elements of the T–stiffeners were modified and studied. Analytical models were designed and analyzed under cyclic and monotonic loadings. Three different indices were computed in the connection region in order to assess the local failure potential; and the moment–rotation hysteretic curves were employed to evaluate the seismic performance of the connections. With the proposed configurations, strain is uniformly distributed within the critical elements. Moreover, excessive deformations of the column cover plate are eliminated.
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