Techno Press
Tp_Editing System.E (TES.E)
Login Search


eas
 
CONTENTS
Volume 15, Number 4, October 2018
 

Abstract
Energy-based methodology is utilized to design novel timber-steel hybrid core wall system. The timber-steel core wall system consists of cross laminated timber (CLT), steel columns, angled brackets and t-stub connections. The CLT wall panels are stiff and strong, and ductility is provided through the steel t-stub connections. The structural system was modelled in SAP2000 finite element program. The hybrid system is explained in detail and validated using first principles. To evaluate performance of the hybrid core system, a 7-story building was designed using both forced-based design and energy based design (EBD) approaches. Performance of the structure was evaluated using 10 earthquakes records selected for 2500 return period and seismicity of Vancouver. The results clearly served as a good example of the benefits of EBD compared to conventional forced based design approaches.

Key Words
energy-based design; hybrid system; cross laminated timber; connection

Address
Caleb Goertz: Read Jones Christoffersen Ltd., Victoria, BC, Canada
Fabrizio Mollaioli: Department of Structural and Geotechnical Engineering, Sapienza University of Rome, Via Gramsci 53, 00197 Rome, Italy
Solomon Tesfamariam: School of Engineering, University of British Columbia, 3333 University Way, Kelowna, BC, Canada

Abstract
In this paper, dynamic analysis of concrete pipe submerged in the fluid and conveying fluid is studied subjected to earthquake load. The structure is modeled by classical shell theory and the force induced by internal fluid is obtained by Navier-Stokes equation. Applying energy method and Hamilton\'s principle, the motion equations are derived. Based on Navier and Newmark methods, the dynamic deflection of the structure is calculated. The effects of different parameters such as mode number, thickness to radius ratios, length to radius ratios, internal and external fluid are discussed on the seismic response of the structure. The results show that considering internal and external fluid, the dynamic deflection increases.

Key Words
dynamic response; concrete pipe; fluid; numerical method; mathematical model

Address
Mohammad Salkhordeh Haghighi, Reza Keikha and Ali Heidari: Department of Civil Engineering, Faculty of Engineering, University of Zabol, P.B. 9861335-856, Zabol, Iran

Abstract
A free vibration analysis and wave propagation of functionally graded porous beams has been presented in this work using a high order hyperbolic shear deformation theory. Unlike other conventional shear deformation theories, a new displacement field that introduces indeterminate integral variables has been used to minimize the number of unknowns. The constituent materials of the beam are assumed gradually variable along the direction of height according to a simple power law distribution in terms of the volume fractions of the constituents. The variation of the pores in the direction of the thickness influences the mechanical properties. It is therefore necessary to predict the effect of porosity on vibratory behavior and wave velocity of FG beams in this study. A new function of the porosity factor has been developed. Hamilton\'s principle is used for the development of wave propagation equations in the functionally graded beam. The analytical dispersion relationship of the FG beam is obtained by solving an eigenvalue problem. Illustrative numerical examples are given to show the effects of volume fraction distributions, beam height, wave number, and porosity on free vibration and wave propagation in a functionally graded beam.

Key Words
higher-order beam theory; functionally graded beam; free vibration; wave propagation; porosity

Address
Belqassim Ayache: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Riadh Bennai: Department of civil engineering, Faculty of civil engineering and architecture, University of Hassiba Benbouali of Chlef, Algeria
Bouazza Fahsi: Laboratoire de Modelisation et Simulation Multi-echelle, Departement de Physique, Faculte des Sciences Exactes, Departement de Physique, Universite de Sidi Bel Abbes, Algeria
Hocine Fourn: Department of Civil Engineering, Faculty of Civil Engineering and Architecture, University of Hassiba Benbouali of Chlef, Algeria
Hassen Ait Atmane: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; Department of civil engineering, Faculty of civil engineering and architecture, University of Hassiba Benbouali of Chlef, Algeria
Abdelouahed Tounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria; Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

Abstract
In this study, seismic performance of low and medium-rise RC buildings with wide-beam and ribbed-slab were evaluated numerically. Moment resisting systems consisting of moment and dual frame were selected as structural system of the buildings. Sufficiency of moment resisting wide-beam frames designed with high ductility requirements were evaluated. Upon necessity frames were stiffen with shear-walls. The buildings were designed in accordance with the Turkish Earthquake Code (TEC 2007) and were evaluated by using the strain-based nonlinear static method specified in TEC. Second order (P-delta) effects on the lateral load capacity of the buildings were also assessed in the study. The results indicated that the predicted seismic performances were achieved for the low-rise (4-story) building with the high ductility requirements. However, the moment resisting frame with high ductility was not adequate for the medium-rise building. Addition of sufficient amount of shear-walls to the system proved to be efficient way of providing the target performance of structure.

Key Words
RC building; wide-beam; moment resisting frame; dual frame; seismic performance evaluation

Address
Kaan Turker: Balikesir University, Engineering Faculty, Department of Civil Engineering, Balikesir, Turkey
Ilhan Gungor: Boga Engineering Company, Bursa, Turkey

Abstract
Floor location of adjacent buildings may be different in terms of height elevation, and thus, the slab may hit on the columns of adjacent insufficiently separated buildings during severe ground motions. Such impacts, often referred to as midcolumn pounding, can be catastrophic. Substantial pounding damage or even total collapse of structures was often observed in large amount of adjacent low rise buildings. The research on the mid-column pounding between low rise buildings is in urgency need. In present study, the responses of two adjacent low rise buildings with unequal heights and different dynamic properties have been analyzed. Parametric studies have also been conducted to assess the influence of story height difference, gap distance and input direction of ground motion on the effect of structural pounding response. Another emphasis of this study is to analyze the near-fault effect, which is important for the structures located in the near-fault area. The analysis results show that collisions exhibit significant influence on the local shear force response of the column suffering impact. Because of asymmetric configuration of systems, the structural seismic behavior is distinct by varying the incident directions of the ground motions. Results also show that near-fault earthquakes induced ground motions can cause more significant effect on the pounding responses.

Key Words
earthquake; low rise buildings; mid-column pounding; non-linear response; parametric analysis

Address
Shan Jiang, Chunwei Zhang and Ning Ning: School of Civil Engineering, Qingdao University of Technology, Qingdao 266033, P.R. China
Changhai Zhai: School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, P.R. China

Abstract
The choice of attenuation relationships is one of the most important parts of seismic hazard analysis as using a different attenuation relationship will cause significant differences in the final result, particularly in near distances. This problem is responsible for huge sensibilities of attenuation relationships which are used in seismic hazard analysis. For achieving this goal, attenuation relationships require a good compatibility with the target region. Many researchers have put substantial efforts in their studies of strong ground motion predictions, and each of them had an influence on the progress of attenuation relationships. In this study, two attenuation relationships are presented using seismic data ofMazandaran province in the north of Iran by Genetic Expression Programming (GEP) algorithm. Two site classifications of soil and rock were considered regarding the shear wave velocity of top 30 meters of site. The quantity of primary data was 93 records; 63 of them were recorded on rock and 30 of them recorded on soil. Due to the shortage of records, a regression technique had been used for increasing them. Through using this technique, 693 data had been created; 178 data for soil and 515 data for rock conditions. The Results of this study show the observed PGA values in the region have high correlation coefficients with the predicted values and can be used in seismic hazard analysis studies in the region.

Key Words
attenuation relationship; genetic expression programming; earthquake; mazandaran

Address
Hamed Taleshi Ahangari, Ehsan Jahani: Faculity of Engineering and Technology, University of Mazandaran, Babolsar, Iran
Zahra Kashir: Department of Civil Engineering, Tabari University, Babol, Iran

Abstract
To solve the seismic response problem of a vertical floating roof tank with base isolation, the floating roof is assumed to experience homogeneous rigid circular plate vibration, where the wave height of the vibration is linearly distributed along the radius, starting from the theory of fluid velocity potential; the potential function of the liquid movement and the corresponding theoretical expression of the base shear, overturning the moment, are then established. According to the equivalent principle of the shear and moment, a simplified mechanical model of a base isolation tank with a swinging effect is established, along with a motion equation of a vertical storage tank isolation system that considers the swinging effect based on the energy principle. At the same time, taking a 150,000 m3 large-scale storage tank as an example, a numerical analysis of the dampening effect was conducted using a vibration mode decomposition response spectrum method, and a comparative analysis with a simplified mechanical model with no swinging effect was applied.

Key Words
storage tank; swinging; isolation; seismic response

Address
Jiangang Sun, Lifu Cui, Xiang Li, Zhen Wang, Weibing Liu: College of Civil Engineering, Dalian Minzu University, Dalian, China
Yuan Lv: Institute of Road and Bridge Engineering, Dalian Maritime University, Dalian, China

Abstract
The seismic vulnerability analysis of multi-span bridges can be based on the response of the piers, provided that deck, bearings and foundations remain elastic. The lateral response of an RC bridge pier can be affected by different mechanisms (i.e., flexure, shear, lap-splice or buckling of the longitudinal reinforcement bars, second order effects). In the literature, simplified formulations are available for mechanisms different from the flexure. On the other hand, the flexural response is usually calculated with a numerically-based Moment-Curvature diagram of the base section and equivalent plastic hinge length. The goal of this paper is to propose a simplified analytical solution to obtain the Moment-Curvature relationship for hollow circular RC sections. This based on calibrated polynomials, fitted against a database comprising 720 numerical Moment-Curvature analyses. The section capacity curve is defined through the position of 6 characteristic points and they are based on four input parameters: void ratio of the hollow section, axial force ratio, longitudinal reinforcement ratio, transversal reinforcement ratio. A case study RC bridge pier is assessed with the proposed solution and the results are compared to a refined numerical FEM analysis, showing good match.

Key Words
Moment-Curvature; hollow circular cross-sections; reinforced concrete; RC members optimisation; RC bridge piers; seismic vulnerability

Address
Roberto Gentile and Domenico Raffaele: Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, Bari, Italy

Abstract
This study provides fragility-based assessment of seismic performance of reinforced concrete bridges. Seismic fragility curves were created using nonlinear analysis (NA) and artificial neural networks (ANNs). Nonlinear response history analyses were performed, in order to calculate the seismic performances of the bridges. To this end, 306 bridge-earthquake cases were considered. A multi-layered perceptron (MLP) neural network was implemented to predict the seismic performances of the selected bridges. The MLP neural networks considered herein consist of an input layer with four input vectors; two hidden layers and an output vector. In order to train ANNs, 70% of the numerical results were selected, and the remained 30% were employed for testing the reliability and validation of ANNs. Several structures of MLP neural networks were examined in order to obtain suitable neural networks. After achieving the most proper structure of neural network, it was used for generating new data. A total number of 600 new bridge-earthquake cases were generated based on neural simulation. Finally, probabilistic seismic safety analyses were conducted. Herein, fragility curves were developed using numerical results, neural predictions and the combination of numerical and neural data. Results of this study revealed that ANNs are suitable tools for predicting seismic performances of RC bridges. It was also shown that yield stresses of the reinforcements is one of the important sources of uncertainty in fragility analysis of RC bridges.

Key Words
fragility curves; seismic performance; artificial neural network; bridge

Address
Mehran S. Razzaghi, Mehrdad Safarkhanlou, Parisa Hosseini: Department of Civil Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran
Araliya Mosleh: CONSTRUCT-LESE, Department of Civil Engineering, Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal

Abstract
In this paper the new intensity measures (IMs) for probabilistic seismic analysis of RC high-rise buildings with core wall structural system are proposed. The existing IMs are analysed and the new optimal ones are presented. The newly proposed IMs are based on the existing ones which: 1) comprise a wider range of frequency velocity spectrum content and 2) are defined as the integral along the velocity spectrum. In analysis characteristics of optimal IMs such as: efficiency, practicality, proficiency and sufficiency are considered. As prototype buildings, RC high-rise buildings with core wall structural system and with characteristic heights: 20-storey, 30-storey and 40-storey, are selected. The non-linear 3D models of the prototype buildings are constructed. 720 non-linear time-history analyses are conducted for 60 ground motion records with a wide range of magnitudes, distances to source and various soil types. Statistical processing of results and detailed regression analysis are performed and appropriate demand models which relate IMs to demand measures (DMs), are obtained. The conducted analysis has shown that the newly proposed IMs can efficiently predict the DMs with minimum dispersion and satisfactory practicality as compared to the other commonly used IMs (e.g., PGA and Sa(T1)). The newly proposed IMs overcome difficulties in calculating of integral along the velocity spectrum and present adequate replacement for IMs which comprise a wider range of frequency velocity spectrum content.

Key Words
RC high-rise building; intensity measure; demand measure; optimality; non-linear time-history analysis; velocity spectrum; regression analysis

Address
Jelena R. Pejovic, Nina N. Serdar and Radenko R. Pejovic: The Faculty of Civil Engineering, University of Montenegro, Podgorica, Montenegro


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2018 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com