Abstract
The paper presents a Bayesian Finite element (FE) model updating methodology by utilizing modal data. The dynamic condensation technique is adopted in this work to reduce the full system model to a smaller model version such that the degrees of freedom (DOFs) in the reduced model correspond to the observed DOFs, which facilitates the model updating procedure without any mode-matching. The present work considers both the MPV and the covariance matrix of the modal parameters as the modal data. Besides, the modal data identified from multiple setups is considered for the model updating procedure, keeping in view of the realistic scenario of inability of limited number of sensors to measure the response of all the interested DOFs of a large structure. A relationship is established between the modal data and structural parameters based on the eigensystem equation through the introduction of additional uncertain parameters in the form of modal frequencies and partial mode shapes. A novel sampling strategy known as the Metropolis-within-Gibbs (MWG) sampler is proposed to sample from the posterior Probability Density Function (PDF). The effectiveness of the proposed approach is demonstrated by considering both simulated and experimental examples.
Key Words
Bayesian model updating; Metropolis-within-Gibbs sampling; model reduction; multiple setups; Transitional Markov Chain Monte Carlo (TMCMC)
Address
Ayan Das, Raj Purohit Kiran and Sahil Bansal: Department of Civil Engineering, Indian Institute of Technology Delhi, 110016, Delhi, India
Abstract
This paper describes the experimental investigation of steel pallet rack beam-to-column connec-tions. Total behavior of moment-rotation (M-q) curve and the effect of particular characteristics on the behavior of connection were studied and the associated load strain relationship and corre-sponding failure modes are presented. In this respect, an estimation of SPRBCCs moment and rotation are highly recommended in early stages of design and construction. In this study, a new approach based on Support Vector Machines (SVMs) coupled with discrete wavelet transform (DWT) is designed and adapted to estimate SPRBCCs moment and rotation according to four input parameters (column thickness, depth of connector and load, beam depth,). Results of SVM-WAVELET model was compared with genetic programming (GP) and artificial neural networks (ANNs) models. Following the results, SVM-WAVELET algorithm is helpful in order to enhance the accuracy compared to GP and ANN. It was conclusively observed that application of SVM-WAVELET is especially promising as an alternative approach to estimate the SPRBCCs moment and rotation.
Key Words
beam end connector; beam-to-column connection; cold formed steel racks; column thickness; support vector
machine; wavelet algorithm
Address
Hossein Hasanvand, Tohid Pourrostam, Javad Majrouhi Sardroud and Mohammad Hasan Ramasht: Department of Civil Engineering, Faculty of Civil & Earth Resources Engineering, Central Tehran Branch, Islamic Azad University, Tehran 1469669191, Iran
Abstract
Critical thermal buckling of functionally graded porous (FGP) sandwich plates under various types of thermal
loading is considered. It is assumed that the mechanical and thermal nonhomogeneous properties of FGP sandwich plate vary
smoothly by distribution of power law across the thickness of sandwich plate. In this paper, porosity defects are modeled as stiffness reduction criteria and included in the rule of mixture. The thermal environments are considered as uniform, linear and nonlinear temperature rises. The critical buckling temperature response of FGM sandwich plates has been analyzed under various boundary conditions. By comparing several numerical examples with the reference solutions, the results indicate that the present analysis has good accuracy and rapid convergence. Further, the effects of various parameters like distribution shape of porosity, sandwich combinations, aspect ratio, thickness ratio, boundary conditions on critical buckling temperature of FGP sandwich plate have been studied in this paper.
Address
Abdelhak Zohra: Civil Engineering Department, University Center of Relizane, Algeria; Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria
Benferhat Rabia, Hassaine Daouadji Tahar: Civil Engineering Department, University of Tiaret, Algeria; Laboratory of Geomatics and Sustainable Development, University of Tiaret, Algeria
Abstract
Any pre-existed delamination defect present during manufacturing or induce during service loading conditions in the wingskin adherend invariably shows a greater loss of structural integrity of the spar wingskin joint (SWJ). In the present study, inter-laminar delamination propagation at the critical location of the SWJ has been carried out using contact and multi-point constraint finite elements available with commercial FE software (ANSYS APDL). Strain energy release rates (SERR) based on virtual crack closure technique have been computed for evaluation of the opening (Mode-I), sliding (Mode-II) and cross sliding (Mode-III) modes of delamination by sequential release of multi point constraint elements. The variations of different modes of
SERR are observed to be significant by considering varied delamination lengths, material properties of adherends and radius of curvature of the SWJ panel. The SERR rates are seen to be much different at the two pre-embedded delamination ends. This shows dissimilar delamination propagation rates. The maximum is seen to occur in the delamination front in the unstiffened region of the wingskin. The curvature geometry and material anisotropy of SWJ adherends significantly influences the SERR
values. Increase in the SERR values are observed with decrease in the radius of curvature of wingskin panel, keeping its width unchanged. SWJs made with flat FRP composite adherends have superior resistance to delamination damage propagation than curved composite laminated SWJ panels. SWJ made with Boron/Epoxy (B/E) material shows greater resistance to the delamination propagation.
Key Words
delamination; finite element modelling; multi point constraint; spar wingskin joints; strain energy release
rates; virtual crack closure technique
Address
P.K. Mishra: Department of Mechanical Engineering, Biju Patnaik University of Technology, Rourkela, Odisha, India
A.K. Pradhan, M.K. Pandit: School of Mechanical Sciences, Indian Institute of Technology, Bhubaneswar, India
S.K. Panda: Department of Mechanical Engineering, Biju Patnaik University of Technology, Rourkela, Odisha, India
Abstract
Response spectrum method is still an effective approach for the design of buildings with supplemental dampers. In practice, complex complete quadratic combination (CCQC) rule is always used in the response spectrum method to consider the effect of non-classical damping. The conventional CCQC rule is based on exact complex mode vectors. Sometimes the calculated complex mode vectors may be not excited by the external loading and errors in the structural responses always arise due to the mode truncation. Load-dependent Ritz (LDR) vectors are associated with the external loading and LDR vectors not excited can be automatically excluded. Also, contributions of higher modes are implicitly contained in the LDR vectors in terms of static responses. To improve the calculation efficiency and accuracy, LDR vectors are introduced in the CCQC rule in the present study. Firstly, the generation procedure of LDR vectors suitable for non-classical damping system is presented. Compared to the conventional LDR vectors, the LDR vectors herein are complex-valued and named as complex LDR (CLDR) vectors. Based on the CLDR vectors, the CCQC rule is then rederived and an improved response spectrum method is developed. Finally, the effectiveness of the proposed method in this paper is verified through three typical non-classical damping buildings. Numerical results show that the CLDR vector is superior to the complex mode with the same number in the calculation. Since the generation of CLDR vectors requires less computational cost and storage space, the method proposed in this paper offers an attractive alternative, especially for structures with a large number of degrees of freedom.
Address
Xiangxiu Li: Institute of Geophysics, China Earthquake Administration, Beijing, China
Huating Chen: Earthquake Engineering Research & Test Center, Guangzhou University, Guangzhou, China
Abstract
The use of steel pipe dampers (SPD) as fuses or interchangeable elements in the steel moment-resisting frames (MRF) is one of the newest methods for improving seismic performance. In the present study, the performance of steel pipe dampers in MRF has been investigated. Evaluation of MRF with and without SPD models were performed using the finite element method by ABAQUS. For validation, an MRF and MRF with steel pipe dampers were modeled that had been experimentally tested and reported in previous experimental research and a good agreement was observed. The behavior of these dampers in frames of 3, 6, and 9 stories was studied by modeling the damper directly. Nonlinear time history dynamic analysis was used. It was observed that by increasing the number of stories in the buildings, steel pipe dampers should be used to perform properly against earthquakes. The installation of steel pipe dampers in steel moment-resisting frames shows that the drift ratio between the floors is reduced and the seismic performance of these frames is improved.
Key Words
fuses, numerical method; performance level; steel moment-resisting frames (MRF); steel pipe dampers (SPD); time history analysis
Address
Ali Mohammad Rousta: Department of Civil Engineering, Yasouj University, Yasouj, Iran
Abstract
In the present work, thermal buckling and post-buckling behaviors of imperfect graphene platelet reinforced metal foams (GPRMFs) doubly curved shells are examined. Material properties of GPRMFs doubly curved shells are presumed to be the function of the thickness. Reddy' shell theory incorporating geometric nonlinearity is utilized to derive the governing equations. Various types of the graphene platelets (GPLs) distribution patterns and doubly curved shell types are taken into account. The nonlinear equations are discretized for the case of simply supported boundary conditions. The thermal postbuckling response are presented to analyze the effects of GPLs distribution patterns, initial geometric imperfection, GPLs weight fraction, porosity coefficient, porosity distribution forms, doubly curved shell types. The results show that these factors have significant effects on the thermal post-buckling problems.
Key Words
doubly curved shells; graphene platelet; initial geometrical imperfection; metal foam; thermal post-buckling
Address
Jia-Qin Xu and Gui-Lin She: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China
Abstract
This paper investigates the dynamic response of a functionally graded material (FGM) coated half-plane excited by distributed time harmonic loading. Three types of typical distributed surface loads, including uniform load, Hertz load, and square-root singular load, are considered. The mass density and elastic modulus of the FGM coating are supposed to be described by the exponential function. The material damping is modelled by a linearly hysteretic damping which is expressed by a complex modulus in the time harmonic motion. Using Fourier integral transform technique and numerical integral method, the effects of the excitation frequency, gradient index, damping, and load type on the dynamic stresses and displacements are discussed.
Key Words
dynamic response; graded coating; hysteretic damping; time harmonic loading
Address
Xiao-Min Wang: Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing 100044, China
Liao-Liang Ke: Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing 100044, China; School of Mechanical Engineering, Tianjin University, Tianjin 300350, China
Yue-Sheng Wang: School of Mechanical Engineering, Tianjin University, Tianjin 300350, China
