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CONTENTS
Volume 12, Number 2, February 2017
 

Abstract
The analytical method is used to develop new models for an elevated tank to estimate its natural period. The equivalent mass- spring method is used to configure the developed analytical models. Also direct method is used for numerical verification. The current study shows that developed models can have a good estimation of natural period compared with concluded results of finite elements. Additional results show that, the dependency of impulsive period to soil stiffness condition is higher than convective period. Furthermore results show that considering the fluid- structure- soil interaction has remarkable effects on natural impulsive and convective periods in case of hard to very soft soil.

Key Words
elevated tanks; fluid- structure- soil interaction; analytical method; impulsive; convective

Address
Pouyan Abbasi Maedeh: International Campus, Kharazmi University, Tehran, I.R. Iran

Ali Ghanbari: Faculty of Engineering, Kharazmi University, Tehran, I.R. Iran

Wei Wu: Faculty of Engineering, University of Bodenkultur, Wien, Austria

Abstract
The underlying goal of the present paper is to investigate soil and structural uncertainties on impedance functions and structural response of soil-shallow foundation-structure (SSFS) system using Monte Carlo simulations. The impedance functions of a rigid massless circular foundation resting on the surface of a random soil layer underlain by a homogeneous half-space are obtained using 1-D wave propagation in cones with reflection and refraction occurring at the layer-basement interface and free surface. Firstly, two distribution functions (lognormal and gamma) were used to generate random numbers of soil parameters (layer´s thickness and shear wave velocity) for both horizontal and rocking modes of vibration with coefficients of variation ranging between 5 and 20%, for each distribution and each parameter. Secondly, the influence of uncertainties of soil parameters (layer´s thickness, and shear wave velocity), as well as structural parameters (height of the superstructure, and radius of the foundation) on the response of the coupled system using lognormal distribution was investigated. This study illustrated that uncertainties on soil and structure properties, especially shear wave velocity and thickness of the layer, height of the structure and the foundation radius significantly affect the impedance functions, and in same time the response of the coupled system.

Key Words
impedance function; circular foundation; cone model; Monte Carlo simulations

Address
Geomaterials Laboratory, Civil Engineering Department, Hassiba Benbouali University of Chlef, P.O Box 151, Chlef 02000, Algeria

Abstract
This paper studies soil properties uncertainty and its implementation in the seismic response evaluation of structures. For this, response sensitivity of two 4- and 12-story RC shear walls to the soil properties uncertainty by considering soil structure interaction (SSI) effects is investigated. Beam on Nonlinear Winkler Foundation (BNWF) model is used for shallow foundation modeling and the uncertainty of soil properties is expanded to the foundation stiffness and strength parameters variability. Monte Carlo (MC) simulation technique is employed for probabilistic evaluations. By investigating the probabilistic evaluation results it

Key Words
soil uncertainty; soil structure interaction; seismic response; probabilistic assessment

Address
Faculty of Civil and Environmental Engineering, Tarbiat Modares University, Jalal-al-Ahmad Highway, Tehran, Iran

Abstract
For energy-based seismic design, a simplified normalized cumulative hysteretic energy spectrum proposed for obtaining hysteretic energy as energy demand is the main objective in this paper. The dimensionless parameter, βEh, is presented to express hysteretic energy indirectly. The βEh spectrum is constructed directly through subtracting the hysteretic energy of single degree-of-freedom (SDOF) system energy equation. The simplified βEh spectral formulation as well as pseudo-acceleration spectrum of modern seismic provisions is developed based on the regression analysis of the large number of seismic responses of SDOF system subjected to earthquake excitations, which considers the influence of earthquake event, soil type, damping ratio, and ductility factor. The relationship between PGV and PGA is established according to the statistical analysis relied on a total of 422 ground motion records. The combination of βEh spectrum and PGV/PGA equation allows determining the cumulative hysteretic energy as a main aseismic design indicator.

Key Words
nonlinear SDOF system; hysteretic energy; response spectrum; damping ratio; ductility

Address
School of Civil Engineering, Suzhou University of Science and Technology, Suzhou, Jiangsu, 215011, China

Abstract
In this paper, the seismic performance of reinforced concrete braced frames (RC-BF) under far- and near-fault motions was investigated. Four-, eight-, 12- and 16-story RC-BFs were designed on the basis of a code-design method for a high risk seismic zone. Nonlinear static and dynamic analyses of the frames have been performed using OpenSees software. To consider diverse characteristics of near-fault motions, records with forward-directivity and fling-step effects were employed. From the results obtained in the analytical study it is concluded that the used design method was reasonable and the mean maximum drift of the frames under all ground motion sets were in acceptable range. For intermediate- and high-rise buildings the near-fault motions imposed higher demands than far-faults.

Key Words
reinforced concrete; steel-brace; dual system; nonlinear analysis; far- and near-fault motions

Address
Reyhaneh Eskandari, Davoud Vafaei: Department of Civil Engineering, Chabahar Maritime University, Chabahar, Iran

Javid Vafaei: Department of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran

Mohammad Ebrahim Shemshadian: Department of Civil, Environmental, and Geo-Engineering, University of Minnesota (Twin Cities), Minneapolis, USA

Abstract
This paper experimentally investigates the effect of yield strength of reinforcing bars and stirrups on the seismic performance of reinforced concrete (RC) circular piers. Reversed cyclic loading tests of nine-large scale specimens with longitudinal and transverse reinforcement of different yield strengths (varying between HRB335, HRB500E and HRB600 rebars) were conducted. The test parameters include the yield strength and amount of longitudinal and transverse reinforcement. The results indicate that the adoption of high-strength steel (HSS) reinforcement HRB500E and HRB600 (to replace HRB335) as longitudinal bars without reducing the steel area (i.e., equal volume replacement) is found to increase the moment resistance (as expected) and the total deformation capacity while reducing the residual displacement, ductility and energy dissipation capacity to some extent. Higher strength stirrups enhance the ductility and energy dissipation capacity of RC bridge piers. While the product of steel yield strength and reinforcement ratio (fyρs) is kept constant (i.e., equal strength replacement), the piers with higher yield strength longitudinal bars are found to achieve as good seismic performance as when lower strength bars are used. When higher yield strength transverse reinforcement is to be used to maintain equal strength, reducing bar diameter is found to be a better approach than increasing the tie spacing.

Key Words
High-Strength Steel (HSS) reinforcement; HRB500E; HRB600; seismic performance; ductility; energy dissipation

Address
Junsheng Su,Junjie Wang: Department of Bridge Engineering, Tongji University, 1239 Siping Rd., Shanghai 200092, PR China

Junsheng Su, Rajesh Prasad Dhakal: Department of Civil and Natural Resources Engineering, University of Canterbury, Private Bag 4800, Christchurch 8140, New Zealand

Wenbiao Wang: Shanghai Municipal Engineering Design Institute (Group) Co., Ltd., 901 North Zhongshan No.2 Rd., Shanghai, 200093, PR China

Abstract
Cancelled

Key Words


Address
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Abstract
Seismic assessment and rehabilitation of Monumental Buildings constitute an important issue in many regions around the world to preserve cultural heritage. On the contrary, many recent earthquakes have demonstrated the high vulnerability of this type of structures. The high nonlinear masonry behaviour requires ad hoc refined finite element numerical models, whose complexity and computational costs are generally unsuitable for practical applications. For these reasons, several authors proposed simplified numerical strategies to be used in engineering practice. However, most of these alternative methods are oversimplified being based on the assumption of in-plane behaviour of masonry walls. Moreover, they cannot be used for modelling the monumental structures for which the interaction between plane and out-plane behaviour governs the structural response. Recently, an innovative discrete-modelling approach for the simulation of both in-plane and out of-plane response of masonry structures was proposed and applied to study several typologies of historic structures. In this paper the latter model is applied with reference to a real case study, and numerically compared with an advanced finite element modelling. The method is applied to the St.Venerio church in Reggiolo (Italy), damaged during the 2012 Emilia-Romagna earthquake and numerically investigated in the literature.

Key Words
cultural heritage; monumental; structures; masonry churches; macro-element approach; discrete element approach; non-linear finite element model; seismic vulnerability; HiStrA software; ABAQUS software

Address
Bartolomeo Pantò,Ivo Caliò: Department of Engineering and Architecture, University of Catania, Viale A. Doria 6 - 95125 Catania, Italy

Linda Giresini: Department of Energy Systems Territory and Costruction Engineering, University of Pisa, Largo Lucio Lazzarino - 56122 Pisa, Italy

Mauro Sassu: Department of Civil, Environmental Engineering and Architecture, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy

Abstract
There has been increasing attention in many countries on seismic retrofit of old fashioned RC structures in recent years. In such buildings, the joints lack transverse reinforcement and suffer inadequate seismic dimensional requirements and the reinforcement is plain bar. The behavior of the joints is governed by sliding of steel bars and diagonal shear failure is less influential. Different methods to retrofit beam-column joints have been proposed in the literature such as wrapping the joint by FRP sheets, enlargement of the beam-column joint, and strengthening the joint by steel sheets. In this study, an enlargement technique that uses external prestressed cross ties with steel angles is examined. The technique has already been used for substructures reinforced by deformed bars and has advantages such as efficient enhancement of seismic capacity and lack of damage to the joint. Three reference specimens and two retrofitted units are tested under increasing lateral cyclic load in combination with two levels of axial load. The reference specimens showed relatively low shear strength of 0.15ꇮ(fc) and 0.30ꇮ(fc) for the exterior and interior joints, respectively. In addition, relatively brittle behavior was observed and large deformations extended into the panel zone of the joints. The retrofit method has increased ductility ratio of the interior beam-column joints by 63%, and energy dissipation capacity by 77%, relative to the control specimen; For external joints, these values were 11%, and 94%. The retrofit method has successfully relocated the plastic joints far from the column face. The retrofit method has improved shear strength of the joints by less than 10%.

Key Words
seismic retrofit; old fashioned RC structures; exterior and interior beam-column joints; plain bars, steel angles prestressed by cross ties

Address
School of Civil Engineering, College of Engineering, University of Tehran, Iran

Abstract
The present research intends to study the effects of the seismic soil-foundation-structure interaction (SFSI) on the dynamic response of various buildings. Two methods including direct and Cone model were studied through 3D finite element method using ABAQUS software. Cone model as an approximate method to consider the SFSI phenomenon was developed and evaluated for both high and low rise buildings. Effect of soil nonlinearity, foundation rigidity and embedment as well as friction coefficient between soil-foundation interfaces during seismic excitation are investigated. Validity and performance of both approaches are evaluated as reference graphs for Cone model and infinite boundary condition, soil nonlinearity and amplification factor for direct method. A series of calculations by DeepSoil for inverse earthquake record modification was conducted. A comparison of the two methods was carried out by root-mean-square-deviation (RMSD) tool for maximum lateral displacement and story shear forces which verifies that Cone model results have good agreement with direct method. It was concluded that Cone method is a convenient, fast and rather accurate method as an approximate way to count for soil media.

Key Words
soil-foundation-structure interaction; finite element method; Cone model; seismic excitation; infinite boundary condition

Address
Faculty of Engineering and Technology, Razi University, Kermanshah, Iran


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