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Abstract
Results of an extensive study aiming to properly extend the well known pushover analysis into 3-D problems of asymmetric buildings are presented in this paper. The proposed procedure uses simple, 3 DOF, one-story models with shear-beam type elements in order to quantify the effects of inelastic torsional response of such buildings. Correction coefficients for the response quantities at the \"stiff\" and \"flexible\" sides are calculated using results from non-linear time history analyses of the simple models. Their values are then applied to the results of a simple, plane pushover analysis of the detailed building models. Results from the application of the new method for a set of three, conventionally designed, five-story buildings with high values of uniaxial eccentricities are compared with those obtained from multiple non-linear dynamic time history analyses, as well as from similar pushover methods addressing the same problem. This initial evaluation indicates that the proposed procedure is a clear improvement over the simple (conventional) pushover method and, in most cases, more accurate and reliable than the other methods considered. The accuracy, however, of all these methods is reduced substantially when they are applied to torsionally flexible buildings. Thus, for such challenging problems, use of inelastic dynamic analyses for a set of two component earthquake motions appears to be the preferable solution.

Key Words
asymmetric buildings; torsional behavior; pushover analysis; shear beam models

Address
Dimitrios K. Baros and Stavros A. Anagnostopoulos: Department of Civil Engineering, University of Patras, Patras, 26500, Greece Dimitrios K. Baros: Department of Civil Engineering, Technological Educational Institute of Western Greece, Patras, 26334, Greece

Abstract
Slender structures like reinforced concrete (RC) chimneys are severely damaged or collapsed during severe wind storms or strong ground motions all over the world. Today, with the improvement in technology and industry, most factories need these slender structures with increasing height and decreasing in shell thickness causing vulnerable to winds and earthquakes. Main objectives in this study are to make structural wind and earthquake analysis of RC chimneys by using a well-known international standard CICIND 2001 and real recorded time history accelerations and to clarify weak points of these tall and slender structures against these severe natural actions. Findings of this study show that maximum tensile stress and shear stress approximately increase 103.90% and 312.77% over or near the openings on the body of the RC chimneys that cause brittle failure around this region of openings.

Key Words
wind; earthquake; reinforced concrete; industrial; opening; chimney; stack

Address
Erdem Turkeli: Vocational School of Technical Sciences, Construction Department, Ordu University, Ordu, Turkey Zeki Karaca: Department of Civil Engineering, Faculty of Engineering, Ondokuz May

Abstract
The Monte Carlo Simulation (MCS) based seismic fragility analysis (SFA) approach allows defining more realistic relationship between failure probability and seismic intensity. However, the approach requires simulating large number of non-linear dynamic analyses of structure for reliable estimate of fragility. It makes the approach computationally challenging. The response surface method (RSM) based metamodeling approach which replaces computationally involve complex mechanical model of a structure is found to be a viable alternative in this regard. An adaptive moving least squares method (MLSM) based RSM in the MCS framework is explored in the present study for efficient SFA of existing structures. In doing so, the repetition of seismic intensity for complete generation of fragility curve is avoided by including this as one of the predictors in the response estimate model. The proposed procedure is elucidated by considering a non-linear SDOF system and an existing reinforced concrete frame considered to be located in the Guwahati City of the Northeast region of India. The fragility results are obtained by the usual least squares based and the proposed MLSM based RSM and compared with that of obtained by the direct MCS technique to study the effectiveness of the proposed approach.

Key Words
seismic fragility analysis; Monte Carlo simulation; response surface method; adaptive moving least squares method

Address
Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, India

Abstract
In this study, result of a field investigation of railway traffic-induced vibrations is provided to examine acceptability levels of ground vibration and to evaluate the serviceability of a liquid-storage tank. Free field attenuation of the amplitudes as a function of distance is derived by six accelerometers and compared with a well-known half-space Bornitz´s analytical solution which considers the loss of the amplitude of waves due to geometrical damping and material damping of Rayleigh. Bornitz´s solution tends to overlap vertical free field vibration compared with in-situ measured records. The vibrations of the liquid-storage tank were compared with the USA, Federal Transportation Railroad Administration (FTA) criteria for acceptable ground-borne vibrations and with the criteria in DIN 4150-3 German standard. Comparing the thresholds stated in DIN 4150-3, absolute peak particle velocities are within the safe limits, however according to FTA velocity level at the top of the water tank exceeds the allowable limits. Furthermore, it is intended to indicate experimentally the effect of the kinematic interaction caused by the foundation of the structure on the free-field vibrations.

Key Words
response of liquid-storage tank, railway traffic, in situ measurements, free field vibrations

Address
Fatih Goktepe: Department of Civil Engineering, Engineering Faculty, Bartin University, 74100 Bartin, Turkey Huseyin S. Kuyuk and Erkan Celebi: Department of Civil Engineering, Engineering Faculty, Sakarya University, 54187, Sakarya, Turkey Huseyin S. Kuyuk: Department of Earthquake Engineering, Kandilli Observatory and Earthquake Research Institute, Bogazici University, 34684, Cengelkoy, Istanbul, Turkey

Abstract
This paper presents investigation into the behavior of beam-column joints, with the joint region concrete being replaced by steel fiber reinforced concrete (SFRC) and by ultra-high performance concrete (UHPC). A total of ten beam-column joint specimens (BCJ) were tested experimentally to failure under monotonic and cyclic loading, with the beam section being subjected to flexural loading and the column to combined flexural and axial loading. The joint region essentially transferred shear and axial stresses as received from the column. Steel fiber reinforced concrete (SFRC) and ultra-high performance concrete (UHPC) were used as an innovative construction and/or strengthening scheme for some of the BCJ specimens. The reinforced concrete specimens were reinforced with longitudinal steel rebar, 18 mm, and some specimens were reinforced with an additional two ties in the joint region. The results showed that using SFRC and UHPC as a replacement concrete for the BCJ improved the joint shear strength and the load carrying capacity of the hybrid specimens. The mode of failure was also converted from a non-desirable joint shear failure to a preferred beam flexural failure. The effect of the ties in the SFRC and UHPC joint regions could not be observed due to the beam flexural failure. Several models were used in estimating the joint shear strength for different BCJ specimens. The results showed that the existing models yielded wide-ranging values. A new concept to take into account the influence of column axial load on the shear strength of beam-column joints is also presented, which demonstrates that the recommended values for concrete tensile strength for determination of joint shear strength need to be amended for joints subject to moderate to high axial loads. Furthermore, finite element model (FEM) simulation to predict the behaviour of the hybrid BCJ specimens was also carried out in an ABAQUS environment. The result of the FEM modelling showed good agreement with experimental results.

Key Words
beam-column joint; hybrid joint; steel fiber reinforced concrete; ultra high performance concrete; joint shear strength; finite element model

Address
M.A. Al-Osta, A.M. Al-Khatib, M.H. Baluch, A.K. Azad: Department of Civil Engineering, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia M.K. Rahman: Center for Engineering Research, Research Institute, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia

Abstract
The intent of this paper is to investigate the propagation of Love waves in a dry sandy medium sandwiched between fiber-reinforced layer and prestressed porous half-space. Separate displacement components have been deduced in order to characterize the dynamics of individual materials. Using suitable boundary conditions, the frequency equation has been derived by means of separation of variables which reveals the significant role of reinforcement parameters, sandiness, thickness of layers, porosity and prestress on the wave propagation. The phase velocity of the Love wave has been discussed in accordance with its typical cases. In both cases when fiber-reinforced and dry sandy media are absent, the derived equation of Love type wave coincides with the classical Love wave equation. Numerical computations have been performed in order to graphically illustrate the dependencies of different parameters on phase velocity of Love waves. It is observed that the phase velocity decreases with the increase of parameters pertaining to reinforcement and prestress. The results have certain potential applications in earthquake seismology and civil engineering.

Key Words
Love wave; fiber-reinforced medium; dry sandy medium; prestress; phase velocity; dispersion equation

Address
Shishir Gupta and Mostaid Ahmed: Department of Applied Mathematics, Indian Institute of Technology (Indian School of Mines), Dhanbad -826004, India

Abstract
Foundation plays a significant role in safe and efficient turbo machinery operation. Turbo machineries generate harmonic load on the foundation due to their high speed rotating motion which causes vibration in the machinery, foundation and soil beneath the foundation. The problems caused by vibration get multiplied if the soil is poor. An improperly designed machine foundation increases the vibration and reduces machinery health leading to frequent maintenance. Hence it is very important to study the soil structure interaction and effect of machine vibration on the foundation during turbo machinery operation in the design stage itself. The present work studies the effect of harmonic load due to machine operation along with earthquake loading on the frame foundation for poor soil conditions. Various alternative foundations like rafts, barrette, batter pile and combinations of barrettes with batter pile are analyzed to study the improvements in the vibration patterns. Detailed computational analysis was carried out in SAP 2000 software; the numerical model was analyzed and compared with the shaking table experiment results. The numerical results are found to be closely matching with the experimental data which confirms the accuracy of the numerical model predictions. Both shake table and SAP 2000 results reveal that combination of barrette and batter piles with raft are best suitable for poor soil conditions because it reduces the displacement at top deck, bending moment and horizontal displacement of pile and thereby making the foundation more stable under seismic loading.

Key Words
turbo machinery; raft; barrette; batter pile; dynamic loading; computational analysis

Address
Sungyani Tripathy and Dr. Atul K Desai: Applied Mechanics Department, Sardar Vallabhbhai National Institute of Technology, Surat, Gujarat-395007, India

Abstract
One of the methods to strengthen the structures against the seismic lateral loading is the employment of the composite columns. A concrete-filled tube (CFT) has the cumulative advantages of steel and concrete. Concrete-filled steel tube columns have been widely used in the moment-resisting frame (MRF) structures, located in both non-seismic zones and high-risk seismic zones. In this paper, the results of studies on two important seismic parameters of ductility and the response modification factor (RMF) of the MRFs with CFT columns are submitted. While the studies are carried out, the effects of span length-story height ratio, the strength of materials and seismic behavior of MRFs are considered. In this regard, the ductility, RMF and the strength of 36 models of the steel MRFs with CFTs are analyzed. The fiber plastic hinges numerical simulation and pushover analysis method are used in the calculations. Based on the obtained results, the RMFs suitable for the 5-, 10- and 15- story frames are proposed.

Key Words
response modification factor; ductility, CFT column, pushover analysis, fiber plastic hinge

Address
Seyed Sh. Hashemi, Mohammad Vaghefi: Department of Civil Engineering, Persian Gulf University, Shahid Mahini Street, P.O. Box: 75169-13817, Bushehr, Iran Kabir Sadeghi: Department of Civil Engineering, Near East University, ZIP Code: 99138, Nicosia, North Cyprus, Mersin 10, Turkey Kaveh Shayan: Department of Civil Engineering, Islamic Azad University of Bushehr, Varzesh Street, P.O. Box: 75196-1955, Bushehr, Iran

Abstract
A seismic margin assessment evaluates how much margin exists for the system under beyond design basis earthquake events. Specifically, the seismic margin for the entire system is evaluated by utilizing a systems analysis based on the sub-system and component seismic fragility data. Each seismic fragility curve is obtained by using empirical, experimental, and/or numerical simulation data. The systems analysis is generally performed by employing a fault tree analysis. However, the current practice has clear limitations in that it cannot deal with the uncertainties of basic components and accommodate the newly observed data. Therefore, in this paper, we present a Bayesian-based seismic margin assessment that is conducted using seismic fragility data and fault tree analysis including Bayesian inference. This proposed approach is first applied to the pool-type nuclear research reactor system for the quantitative evaluation of the seismic margin. The results show that the applied approach can allow updating by considering the newly available data/information at any level of the fault tree, and can identify critical scenarios modified due to new information. Also, given the seismic hazard information, this approach is further extended to the real-time risk evaluation. Thus, the proposed approach can finally be expected to solve the fundamental restrictions of the current method.

Key Words
seismic margin assessment; seismic probabilistic risk assessment; fault tree analysis; Bayesian inference; research reactor; fragility analysis; hazard curve

Address
Shinyoung Kwag, Jinho Oh, Jong-Min Lee and Jeong-Soo Ryu:Research Reactor Mechanical Structure Division, Korea Atomic Energy Research Institute, 111 Daedeok-daero, Yuseong-gu, Daejeon 34057, Republic of Korea

Abstract
Cold-formed steel is widely used in steel structures, especially in transmission towers, because of advantages such as low weight, high strength, excellent mechanical properties, etc. However, there is not a special design code for cold-formed steel use in transmission towers in China. For this study, a total of 105 compression members were tested statically to investigate the bearing capacity of cold-formed steel members under different boundary conditions in transmission towers. The test results were compared to the results predicted by the current design codes. For deeper insight, additional coupled members were simulated using finite element analysis. An improved design method was developed based on the experimental and analytical results.

Key Words
bearing capacity; instability; cold-formed steel; transmission tower; boundary condition

Address
Junke Han: Beijing Key Lab of Earthquake Engineering and Structural Retrofit, Beijing University of Technology, Beijing, 100124, China; China Electric Power Research Institute, Beijing 100055, China Xu Zhao, Zhenyun Tang, Hua Ma and Zhenbao Li: Beijing Key Lab of Earthquake Engineering and Structural Retrofit, Beijing University of Technology, Beijing, 100124, China

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