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CONTENTS
Volume 20, Number 5, May 2021
 


Abstract
The limit equilibrium analysis through the horizontal slice method is used to study the seismic stability of reinforced soil slopes by satisfying the equilibrium of the horizontal and vertical forces as well as moments. Unlike the pseudo-static (PS) method, the pseudo-dynamic method consideres the effects of time and phase difference of the P and S waves propagation inside the soil mass. In this paper, the PS, the conventional pseudo-dynamic (CPD), and the modified pseudo-dynamic (MPD) methods are used to study the seismic stability of reinforced soil slopes. In addition, the equivalent linear method is implemented to analyze the site response for the purpose of calculating the soil dynamics parameters required for the seismic stability analysis of soil slopes via the MPD method. A MATLAB code is developed to calculate via the abovementioned methods. Using the log-spiral slip surface, this code considers the distribution of reinforcements as uniform and variable spacing. In addition, the effect of surcharge pressure on the seismic stability of the slope is included in this study. The obtained results showed that, in general, the MPD method combined with the equivalent linear analysis would produce more critical results than other methods.

Key Words
reinforced soil slope; limit equilibrium; modified pseudo-dynamic; equivalent linear analysis; horizontal slice method

Address
Nima Farshidfar:Department of Civil Engineering, Delvar Branch, Islamic Azad University, Delvar, Iran

Amin Keshavarz:Department of Civil Engineering, Persian Gulf University, Bushehr, Iran

Seyyed M. Mirhosseini:Department of Civil Engineering, Arak Branch, Islamic Azad University, Arak, Iran

Abstract
This paper presents the selection and scaling of ground motion of Patna, Bihar (India) using Response Spectra (Rsp) Match technique MATLAB code and soil amplification using Equivalent-linear Earthquake site Response Analyses (EERA) excel macro. North Bihar including Patna is in seismic zone IV hence preventive measure are to be explored to avoid catastrophic earthquake damages. The earthquake ground motion data of Patna is required for economic and effective earthquake resistant constructions in Patna. Five earthquake ground motions obtained from RspMatch2005 technique used to estimate soil movement response for six selected sites in Patna. In present work, the earthquake ground motion data of Patna is generated which is not available earlier in literature. The interpolated shear wave velocity of Patna obtained by SPT test and earthquake ground motion obtained from RSP Match software used as input in EERA to acquire the amplification factor. After that amplification of Earthquake, ground motion using local soil behaviour explored. In present study, it is found the amplification factor is 1.8 to 5 at 5 Hz. This amplified ground motion may be used for linear and nonlinear earthquake structural analysis.

Key Words
RSP match; scaling; selection; amplification factor; EERA; site effects

Address
Raushan Ranjan:Department of Civil Engineering, GCE, Gaya, Bihar, India

Ajay Kumar:Department of Civil Engineering, NIT- Patna, Bihar, India

Abstract
In this paper, a procedure to seismic risk assessment of structures equipped with magnetorheological (MR) damper considering multiple performance criteria has been presented while accounting for uncertainties of the applied excitation, structure and damper properties, and damage state thresholds. The procedure employes the Latin hypercube sampling (LHS) method to generate 30 sample random MR-Structure systems and incremental dynamic analysis (IDA) has been conducted under 20 earthquakes to evaluate engineering demand parameters. Fragilities have been evaluated using the Monte Carlo simulation (MCS) method in each intensity measure and have been integrated with the hazard curve to determine the reliability during lifetime. For numerical analysis, an eight-story nonlinear shear building with bilinear hysteresis behavior has been adopted. The effectiveness of the introduced methodology is illustrated through a seismic risk assessment of the structure equipped with passive-off and passive-on MR dampers. Numerical results have shown the capability of MR dampers in significant mitigation of the seismic risk of the nonlinear structure. Moreover, it is observed that considering multiple performance criteria of the structural system, non-structural components, and MR damper stroke length and the interaction between them has led to increase the seismic risk. Also, the uncertainty of the applied excitation shows more remarkable influence with respect to the other sources of uncertainties.

Key Words
risk assessment; fragility curves; reliability during lifetime; multiple performance criteria; nonlinear structure; MR damper uncertainty; MR damper damage state

Address
Mohtasham Mohebbi:Faculty of Engineering, University of Mohaghegh Ardabili, 56199-11367, Ardabil, Iran

Sina Bakhshinezhad:Faculty of Engineering, University of Mohaghegh Ardabili, 56199-11367, Ardabil, Iran

Abstract
In this paper, the dynamic behaviour and seismic damages of concrete cylindrical water storage tanks are investigated. Furthermore, by modeling the reservoirs, using normal concrete and engineered cementitious composite (ECC), the effects of ECC on reducing the seismic damages of reservoirs are investigated. For this purpose, ANSYS software is used to perform the nonlinear dynamic analysis of the tanks and different parameters including the hoop force and bending moment of the wall and cracking or crushing of the concrete were examined. According to the results, the relationships and criteria provided in the ACI standard for design of tanks are recommended to be revised in certain parts. Unlike the normal concrete tanks, in those made of ECC, concrete fracture is not observed and the crack width remains very small at a level that is not problematic. Finally, the use of ECC in cylindrical water storage tanks is suggested as a strategy for reducing the seismic vulnerability of this type of hydraulic structures.

Key Words
concrete tanks; ECC; dynamic analysis; nonlinear; hysteresis; ANSYS

Address
Pouria Sheikh Bahaei: Department of Civil Engineering, Isfahan University of Technology, Isfahan 8415683111, Iran

Farhad Behnamfar:Department of Civil Engineering, Isfahan University of Technology, Isfahan 8415683111, Iran

Abdolreza Kabiri Samani:Department of Civil Engineering, Isfahan University of Technology, Isfahan 8415683111, Iran

Abstract
Several seismic analysis procedures in the latest standards have been developed for structural design and assessment. Since these methods have different advantages and limitations, a comprehensive comparison of these procedures is required to select the most effective one. The three most common methods are the Equivalent Lateral Force (ELF) method, Modal Response Spectrum (MRS) analysis, and Linear Response History (LRH) analysis. This research intends to present a comparative study of these methods, according to ASCE 7-16 standard by utilizing ETABSR software. They were examined in terms of base shear and distribution of story shear forces for a sixth-story reinforced concrete (RC) building, designed according to ACI 318-19 standard. Building code requirements for RC structures with the dual lateral force-resisting system in a high seismic zone are discussed. The results show that the ELF procedure's base shear for the building under consideration is conservative compared to the MRS or LRH analysis. The vertical distribution of the ELF procedure is just a function of the structure's fundamental period; however, the advantage of the MRS and LRH analysis is that they provide information as to how the distribution of mass and stiffness of a structure influences the member forces and displacements.

Key Words
seismic analysis; equivalent lateral force; modal response spectrum analysis; linear response history analysis; story drift

Address
Reza Latifi:Civil Engineering, University of Bologna, 40136, Italy

Marijana Hadzima-Nyarko:University J. J. Strossmayer of Osijek, Faculty of Civil Engineering and Architecture Osijek, Vladimira Preloga 3, 31000 Osijek

Abstract
Seismic isolation is widely used in the structures to dissipate the destructive energy of an earthquake by decoupling the superstructure from the ground. High-damping rubber (HDR) devices, as a type of energy dissipating device, used in structural systems to control the structural response under energetic excitations such as earthquakes. This paper uses the Weakening and Damping (WeD) scheme to realize a modified approach in reducing all of the structural responses simultaneously. By this modification, Negative Stiffness Devices (NSDs) are used for the weakening phase to lessen lateral strength. The HDR device is used as a part of NSDs components. HDR generates a high damping force to establish a modified "Weakening and High Damping" (WeHD) concept and gain optimal performance in the overall structural responses. Use of the HDR in seismic base isolation not only prevents permanent deformation under strong motions but also works as an energy dissipating device even during the small ambient vibrations. Since the structure could be unstable by using NSDs, MR dampers are added to preserve stability. An inverse model is employed to command MR dampers by adjusting the voltage and generating the desired control forces. To further verify the proposed WeHD device, a smart base-isolated benchmark building framework is used. Based on the results, the proposed Weakening and High Damping (WeHD) approach not only reduces base displacements, accelerations, and shear but also leads to a reduction in the accelerations and inter-story drifts of the superstructure.

Key Words
high damping rubber; weakening and damping; negative stiffness device; inverse model; velocity control algorithm; smart base-isolated

Address
Arash Bahar:Department of Civil Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran

Mohsen Salavati-Khoshghalb:Department of Civil Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran

Seyed Mehdi Ejabati:Department of Civil Engineering, Babol Noshirvani University of Technology, Babol, Iran

Abstract
Experimental studies reveal that weakness in joint core leads to the formation of a shear hinge in this area, loss of load carrying capacity in the both regions of cyclic curve and decrease of ductility. Generally, the recent mentioned results are related to the previous studies, in which the effect of slabs and lateral beams (2D joints) have been neglected. However, these effects can lead to different responses in real joints compared to ideal 2D joints, in the term of changes in capacity and demand. Consequently, in this study the effect of slab and lateral beam has been considered (3D joints). Four 3D external joints with a scale of 1/2 are made in the laboratory. Specimens include two control joints and two damaged joints retrofitted by stiffened angles and post-tensioned bars. The results show that the use of retrofit method for damaged joints results in the formation of a flexural plastic hinge in the beam and shift of the shear hinge out of the joint core. Furthermore, the effect of slab and lateral beam in the bare non-seismic joint may lead to the increase of the ductility, compared to the similar 2D joints in previous studies.

Key Words
damaged RC joint; hysteresis curves; joint enlargement; dissipated energy

Address
Gholamreza Morshedijoo:Department of Civil Engineering, Semnan Branch, Islamic Azad University, Semnan, Iran

Ali Golafshar:Department of Civil Engineering, Semnan Branch, Islamic Azad University, Semnan, Iran

Mohammad hossein Saghafi:Department of Civil Engineering, Semnan Branch, Islamic Azad University, Semnan, Iran

Abstract
According to the PEER probabilistic seismic loss assessment methodology, a structure-level seismic risk assessment method was proposed and implemented for a set of RC frames designed according to Chinese seismic code. These frames were designed for fortification intensities of 6,7 and 8 and classified into 4,6 and 8 stories. Through incremental dynamic time history analysis (IDA), the statistical relationships of the maximum inter-story drift ratio with the seismic spectral acceleration were obtained and used to determine fragility curve for each damage states. The site seismic hazard model was established based on Chinese seismic code, and the probability distribution of each discrete intensity levels was derived. Using loss index from the Chinese standard and Hazus, the structure means annual frequency of collapse, the Expected Annual Financial Loss (EAL) and the Expected Annual Fatalities (EAF) were calculated. The variation trends of these performance metrics with seismic fortification intensities and structure heights were evaluated, and the weaknesses of the current seismic code of China were pointed out. It was concluded that the method proposed in this paper is simple and reliable for practical applications.

Key Words
seismic loss assessment; seismic hazard; structure-level; loss index; fragility analysis; Hazus

Address
Shuhe Wang:School of Civil and Resource Engineering, University of Science and Technology Beijing, No.30 Xueyuan Road, Beijing, China

Ximing Li:School of Civil and Resource Engineering, University of Science and Technology Beijing, No.30 Xueyuan Road, Beijing, China

Jubing Zhang:School of Civil and Resource Engineering, University of Science and Technology Beijing, No.30 Xueyuan Road, Beijing, China


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