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CONTENTS
Volume 53, Number 2, January25 2015
 

Abstract
After the large destruction of Lisbon due to the 1755 earthquake, the city had to be almost completely rebuilt. In this context, an innovative structural solution was implemented in new buildings, comprising internal timber framed walls which, together with the floors timber elements, constituted a 3-D framing system, known as \"cage\", providing resistance and deformation capacity for seismic loading. The internal timber framed masonry walls, in elevated floors, are constituted by a timber frame with vertical and horizontal elements, braced with diagonal elements, known as Saint Andrew\'s crosses, with masonry infill. This paper describes an experimental campaign to assess the in-plane cyclic behaviour of those so called \"frontal\" walls. A total series of 4 tests were conducted in 4 real size walls. Two models consist of the simple timber frames without masonry infill, and the other two specimens have identical timber frames but present masonry infill. Experimental characterization of the in-plane behaviour was carried out by static cyclic shear testing with controlled displacements. The loading protocol used was the CUREE for ordinary ground motions. The hysteretic behaviour main parameters of such walls subjected to cyclic loading were computed namely the initial stiffness, ductility and energy dissipation capacity.

Key Words
\"Pombaline\" buildings; cyclic loading tests; earthquake

Address
Ana Maria Goncalves, Joao Gomes Ferreiraa, Luis Guerreirob and Fernando Branco: Department of Civil Engineering, Technical University of Lisbon from University of Lisbon, Lisbon 1049-001, Portugal

Abstract
Finite element method (FEM) is an effective quantitative method to solve complex engineering problems. The basic idea of FEM for a complex problem is to be able to find a solution by reducing the problem made simple. If mathematical tools are inadequate to obtain precise result, even approximate result, FEM is the only method that can be used for structural analyses. In FEM, the domain is divided into a large number of simple, small and interconnected sub-regions called finite elements. FEM has been used commonly for linear and nonlinear analyses of different types of structures to give us accurate results of plane stress and plane strain problems in civil engineering area. In this paper, FEM is used to investigate stress analysis of a shear wall which is subjected to concentrated loads and fundamental principles of stress analysis of the shear wall are presented by using matrix displacement method in this paper. This study is consisting of two parts. In the first part, the shear wall is discretized with constant strain triangular finite elements and stiffness matrix and load vector which is attained from external effects are calculated for each of finite elements using matrix displacement method. As to second part of the study, finite element analysis of the shear wall is made by ANSYS software program. Results obtained in the second part are presented with tables and graphics, also results of each part is compared with each other, so the performance of the matrix displacement method is demonstrated. The solutions obtained by using the proposed method show excellent agreements with the results of ANSYS. The results show that this method is effective and preferable for the stress analysis of shell structures. Further studies should be carried out to be able to prove the efficiency of the matrix displacement method on the solution of plane stress problems using different types of structures.

Key Words
finite element method; plane stress problem; constant strain triangle element; ANSYS

Address
Mustafa Ergun and Sevket Ates: Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey

Abstract
A CFPBS (Cone-type Friction Pendulum Bearing System) was developed to control the acceleration delivered to a structure to prevent the damage and degradation of critical communication equipment during earthquakes. This study evaluated the isolation performance of the CFPBS by numerical analysis. The CFPBS was manufactured in the shape of a cone differenced with the existing FPS (Friction Pendulum System), and a pattern was engraved on the friction surface. The natural frequencies of the CFPBS were evaluated from a free-vibration test with a seismic isolator system consisting of 4 CFPBS. To confirm the earthquake-resistant performance, a numerical analysis program was prepared using the equation of the CFPBS induced from the equations of motion. The equation reported by Tsai for the rollingtype seismic isolation bearings was proposed to design the equation of the CFPBS. Artificial seismic waves that satisfy the maximum earthquake scale of the Korean Building Code-Structural (KBC-2005) were created and verified to review the earthquake-resistant performance of the CFPBS by numerical analysis. The superstructural mass of the CFPBS and the skew angle of friction surface were considered for numerical analysis with El Centro NS, Kobe NS and artificial seismic waves. The CFPBS isolation performance evaluation was based on the numerical analysis results, and comparative analysis was performed between the results from numerical analysis and simplified theoretical equation under the same conditions. The validity of numerical analysis was verified from the shaking table test.

Key Words
cone-type friction pendulum bearing; friction pendulum system; seismic performance; seismic isolation; shaking table test

Address
Bub-Gyu Jeon, Sung-Jin Chang, Sung-Wan Kim and Nam-Sik Kim:
Department of Civil & Environmental Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735, Republic of Korea

Abstract
Damage detection based on a reference set of measured data usually has the problem of different environmental temperature in the two sets of measurements, and the effect of temperature difference is usually ignored in the subsequent model updating. This paper attempts to identify the structural damage including the temperature difference with artificial measurement noise. Both local damages and the temperature difference are identified in a gradient-based model updating method based on dynamic response sensitivity. The sensitivities of dynamic response with respect to the system parameters and temperature difference are calculated by direct integration method. The measured dynamic responses of the structure from two different states are used directly to identify the structural local damages and the temperature difference. A single degree-of-freedom mass-spring system and a planar truss structure are studied to illustrate the effectiveness of the proposed method.

Key Words
response sensitivity; damage detection; model updating; temperature difference

Address
J.J. Wei: Department of Construction Engineering, Changzhou Institute of Engineering Technology, Changzhou, Jiangsu, P.R. China
Z.R. Lv: Department of Applied Mechanics and Engineering, Sun Yat-sen University, Guangzhou, Guangdong, P.R. China

Abstract
Structural damage and moving load identification are the two aspects of structural system identification. However, they universally coexist in the damaged structures subject to unknown moving load. This paper proposed a dynamic response sensitivity-based model updating method to simultaneously identify the structural damage and moving force. The moving force which is equivalent as the nodal force of the structure can be expressed as a series of orthogonal polynomial. Based on the system Markov parameters by the state space method, the dynamic response and the dynamic response derivatives with respect to the force parameters and elemental variations are analytically derived. Afterwards, the damage and force parameters are obtained by minimizing the difference between measured and analytical response in the sensitivity-based updating procedure. A numerical example for a simply supported beam under the moving load is employed to verify the accuracy of the proposed method.Structural damage and moving load identification are the two aspects of structural system identification. However, they universally coexist in the damaged structures subject to unknown moving load. This paper proposed a dynamic response sensitivity-based model updating method to simultaneously identify the structural damage and moving force. The moving force which is equivalent as the nodal force of the structure can be expressed as a series of orthogonal polynomial. Based on the system Markov parameters by the state space method, the dynamic response and the dynamic response derivatives with respect to the force parameters and elemental variations are analytically derived. Afterwards, the damage and force parameters are obtained by minimizing the difference between measured and analytical response in the sensitivity-based updating procedure. A numerical example for a simply supported beam under the moving load is employed to verify the accuracy of the proposed method.

Key Words
structural damage identification; response sensitivity; system Markov parameters; moving load

Address
Hongping Zhu: School of Civil Engineering and Mechanics, Huazhong University of Science and Technology, Wuhan, Hubei, P.R. China
Ling Mao: School of Civil Engineering and Mechanics, Huazhong University of Science and Technology, Wuhan, Hubei, P.R. China
Shun Weng: School of Civil Engineering and Mechanics, Huazhong University of Science and Technology, Wuhan, Hubei, P.R. China
Yong Xia: Department of Civil & Structural Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

Abstract
The objective of this paper is to investigate the surface waves in fibre-reinforced anisotropic thermoelastic medium subjected to gravity field. The theory of generalized surface waves has firstly developed and then it has been employed to investigate particular cases of waves, viz., Stoneley waves, Rayleigh waves and Love waves. The analytical expressions for displacement components, force stress and temperature distribution are obtained in the physical domain by using the harmonic vibrations. The wave velocity equations have been obtained in different cases. The numerical results are given and presented graphically in Green-Lindsay and Lord-Shulman theory of thermoelasticity. Comparison was made with the results obtained in the presence and absence of gravity, anisotropy, relaxation times and parameters for fibrereinforced of the material medium. The results indicate that the effect of gravity, anisotropy, relaxation times and parameters for fibre-reinforced of the material medium are very pronounced.

Key Words
wave propagation; fibre-reinforced medium; thermal stresses; thermo-elastic medium; gravity field

Address
A.M. Abd-Alla: Mathematics Department, Faculty of Science, Taif University, Saudi Arabia; Mathematics Department, Faculty of Science, Sohag University, Egypt
S.M. Abo-Dahab: Mathematics Department, Faculty of Science, Taif University, Saudi Arabia; Mathematics Department, Faculty of Science, Qena, Egypt, Qena 83523, Egypt
F.S. Bayones: Mathematics Department, Faculty of Science, Taif University, Saudi Arabia

Abstract
The purpose of this work is to analyze the effect of structure parameter disturbance on the dynamic characteristics of a hydropower station powerhouse. A vibration model with a head-cover system is established, and then the general disturbance problem analysis methods are discussed. Two new formulae based on two types of disturbances are developed from existing methods. The correctness and feasibility of these two formulae are validated by analyzing the hydropower station powerhouse vibration model. The appropriate calculation method for disturbance of the hydropower station powerhouse vibration dynamic characteristics is derived.

Key Words
hydropower station; transfer path; stochastic perturbation method; Hadamard product; linear stochastic structure; time-invariable parameters; dual disturbances; dynamic characteristics

Address
Baoping Zhi: School of Hydraulic Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, No.2 Linggong Road, Dalian, Liaoning Province, 116023 China; University Engineering Technology Research Center of Small Watershed Conservancy of Henan Province, No.1 Dongjing Avenue, Kaifeng, Henan Province, 475004 China
Zhenyue Ma: School of Hydraulic Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, No.2 Linggong Road, Dalian, Liaoning Province, 116023 China

Abstract
The purpose of this study was to investigate experimentally the fatigue performance of reinforced concrete (RC) beams with hot-rolled ribbed fine-grained steel bars of yielding strength 500MPa (HRBF500). Three rectangular and three T-section RC beams with HRBF500 bars were constructed and tested under static and constant-amplitude cyclic loading. Prior to the application of repeated loading, all beams were initially cracked under static loading. The major test variables were the steel ratio, crosssectional shape and stress range. The stress evolution of HRBF500 bars, the information about crack growth and the deflection developments of test beams were presented and analyzed. Rapid increases in deflections and tension steel stress occured in the early stages of fatigue loading, and were followed by a relatively stable period. Test results indicate that, the concrete beams reinforced with appropriate amount of HRBF500 bars can survive 2.5 million cycles of constant-amplitude cyclic loading with no apparent signs of damage, on condition that the initial extreme tensile stress in HRBF500 steel bars was controlled less than 150 MPa. It was also found that, the initial extreme tension steel stress, stress range, and steel ratio were the main factors that affected the fatigue properties of RC beams with HRBF500 bars, whose effects on fatigue properties were fully discussed in this paper, while the cross-sectional shape had no significant influence in fatigue properties. The results provide important guidance for the fatigue design of concrete beams reinforced with HRBF500 steel bars.

Key Words
HRBF500 steel bar; fatigue performance; RC beam; constant-amplitude cyclic loading

Address
Ke Li: Department of Civil Engineering, Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast University, Nanjing 210096, P.R. China
Xin-Ling Wang: Department of Civil Engineering, Zhengzhou University, Zhengzhou 450002, P.R. China
Shuang-Yin Cao: Department of Civil Engineering, Key Laboratory of Concrete and Prestressed Concrete Structures of the Ministry of Education, Southeast University, Nanjing 210096, P.R. China
Qing-Ping Chen: Department of Civil Engineering, Kaifeng University, Kaifeng 475000, P.R. China

Abstract
This paper presents a study based on the damage due to the fatigue life of thrust ball bearings using vibratory analysis. The main contribution of this work lies in establishing a relation between modal damping and the rolling contact fatigue damage of the thrust ball bearing. Time domain signals and frequency spectra are extracted from both static and dynamic experiments. The first part of this research consists in measuring the damping of damaged thrust ball bearings using impact hammer characterization tests. In a second part, indented components representing spalled bearings are studied to determine the evolution of damping values in real-time vibration spectra using the random decrement method. Dynamic results, in good agreement with static tests, show that damping varies depending on the component

Key Words
rolling fatigue contact; modal damping; thrust ball bearing; modal analysis

Address
Toumi M.Yessine, Bolaers Fabricea, Bogard Fabienb, Murer Sebastien: GRESPI/MAN, University of Reims Champagne-Ardenne, UFR Sciences Exactes et Naturelles,Campus du Moulin de la Housse -51687 Reims Cedex 2, France

Abstract
In this article, free vibration of functionally graded (FG) elliptic plates subjected to various classical boundary conditions has been investigated. Literature review reveals no study has been performed based on functionally graded elliptic plates till date. The mechanical kinematic relations are considered based on classical plate theory. Rayleigh-Ritz technique is used to obtain the generalized eigenvalue problem. The material properties of the FG plate are assumed to vary along thickness direction of the constituents according to power-law form. Trial functions denoting the displacement components are expressed in simple algebraic polynomial forms which can handle any edge support. The objective is to study the effect of geometric configurations and gradation of constituent volume fractions on the natural frequencies. New results for frequency parameters are incorporated after performing a test of convergence. A comparison study is carried out with existing literature for validation in special cases. Three-dimensional mode shapes for circular and elliptic FG plates are also presented with various boundary conditions at the edges.

Key Words
vibration; elliptic functionally graded plate; Rayleigh-Ritz method; classical plate theory; mode shapes

Address
K.K. Pradhan, S. Chakraverty: Department of Mathematics, National Institute of Technology Rourkela, Odisha 769008, India

Abstract
This paper identifies the effects of infill wall existence and arrangement in the seismic response of steel frame structures. The methodology followed was based on the utilisation of overall seismic response indicators that distil the complexity of structural response in a single value hence enabling their straightforward comparative and statistical post process. The overall structure damage index after Park/Ang (OSDIPA) and the maximum inter-story drift ratio (MISDR) have been selected as widely utilized structural seismic response parameters in contemporary state of art. In this respect a set of 225 Greek antiseismic code (EAK) spectrum compatible artificial accelerograms have been created and a series of non-linear dynamic analyses have been executed. Data were obtained through nonlinear dynamic analyses carried on an indicative steel frame structure with 5 different infill wall topologies. Results indicated the significant overall contribution of infill walls with a reduction that ranged 35-47% of the maximum and 74-81% of the average recorded OSDIPA values followed by an overall reduction of 64-67% and 58-61% for the respective maximum and average recorded MISDR values demonstrating the relative benefits of infill walls presence overall as well as localised with similar reductions observed in 1st level damage indicators.

Key Words
infill wall topology; dynamic analysis; overall structural damage; seismic response; nonlinear behaviour; frame structure

Address
N. Nanos: School of Civil Engineering & Surveying, University of Portsmouth, PO13AH Portsmouth, UK
A. Elenas: Department of Civil Engineering, Institute of Structural Mechanics and Earthquake Engineering, Democritus University of Thrace, GR-67100 Xanthi, Greece

Abstract
In the present work, structural joints have been modeled as a pair of translational and rotational springs and frequency equation of the overall system has been developed using sub-structure synthesis. It is shown that using first few natural frequencies of the system, one can obtain a set of over-determined system of equations involving the unknown stiffness parameters. Method of multi-linear regression is then applied to obtain the best estimate of the unknown stiffness parameters. The estimation procedure has been developed first for a two parameter joint model and then for a three parameter model, in which cross coupling terms are also included. Two cases of structural connections have been considered, first with a cantilever beam with support flexibility and then a pair of beams connected through lap joint. The validity of the proposed method is demonstrated through numerical simulation and by experimentation.

Key Words
vibration; sub-structure synthesis; joint stiffness identification; linear parameters; multi-linear regression; cantilever; single lap joint

Address
Sanjay B. Ingole: Government Polytechnic, Nagpur, 440 001, India
Animesh Chatterjee: Visvesvaraya National Institute of Technology, Nagpur 440 010, India

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