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CONTENTS
Volume 2, Number 3, July 2017
 

Abstract
Solving a system of linear or non-linear equations is required to analyze any kind of structures. There are many ways to solve a system of equations, and they can be classified as implicit and explicit techniques. The explicit methods eliminate round-off errors and use less memory. The dynamic relaxation method (DR) is one of the powerful and simple explicit processes. The important point is that the DR does not require to store the global stiffness matrix, for which it just uses the residual loads vector. In this paper, a new approach to the DR method is expressed. In this approach, the damping, mass and time steps are similar to those of the traditional method of dynamic relaxation. The difference of this proposed method is focused on the method of calculating the damping. The proposed method is expressed such that the time step is constant, damping is equal to zero except in steps with maximum energy and the concentrated damping can be applied to minimize the energy of system in this step. In this condition, the calculation of damping in all steps is not required. Then the volume of computation is reduced. The DR method for form-finding of membrane structures is employed in this paper. The form-finding of the three plans related to the membrane structures with different loading is considered to investigate the efficiency of the proposed method. The numerical results show that the convergence rate based on the proposed method increases in all cases than other methods.

Key Words
dynamic relaxation method; concentrated damping; form-finding; membrane structures

Address
S. Fatemeh Labbafi, S. Reza Sarafrazi and Hossein Gholami: Department of Civil Engineering, University of Birjand, Birjand, Iran
Thomas H.-K. Kang:
1) Department of Architecture & Architectural Engineering, Seoul National University, Seoul, Korea
2) Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, USA

Abstract
This paper presents a non-destructive testing method for estimating the structural response of cable-stayed footbridges. The approach combines field measurements with a numerical static analysis of the structure. When the experimental information concerning the structure deformations is coupled with the numerical data on the structural response, it is possible to calculate the static forces and the design tension resistance in selected structural elements, and as a result, assess the condition of the entire structure. The paper discusses the method assumptions and provides an example of the use of the procedure to assess the load-carrying capacity of a real steel footbridge. The proposed method can be employed to assess cable-stayed structures including those made of other materials, e.g., concrete, timber or composites.

Key Words
footbridge; cable-stayed footbridge; static tests; numerical simulation

Address
Pawel G. Kossakowski

Abstract
The present work proposes the thermo mechanically induced statistics of nonlinear transverse central deflection of elastically supported functionally graded (FG) plate subjected to static loadings with random system properties. The FG plate is supported on two parameters Pasternak foundation with Winkler cubic nonlinearity. The random system properties such as material properties of FG material, external loading and foundation parameters are assumed as uncorrelated random variables. The material properties are assumed as non-uniform temperature distribution with temperature dependent (TD) material properties. The basic formulation for static is based on higher order shear deformation theory (HSDT) with von-Karman nonlinear strain kinematics through Newton-Raphson method. A second order perturbation technique (SOPT) and direct Monte Carlo simulation (MCS) are used to compute the nonlinear governing equation. The effects of load parameters, plate thickness ratios, aspect ratios, volume fraction, exponent, foundation parameters, and boundary conditions with random system properties are examined through parametric studies. The results of present approaches are compared with those results available in the literature and by employing direct Monte Carlo simulation (MCS).

Key Words
integrated design; evaluation; current practice; integrated platform; online survey; designers

Address
Achchhe Lal: Department of Mechanical Engineering, S.V. National Institute of Technology Surat, 395007, India
Kirankumar R. Jagtap: Department of Mechanical Engineering, Sinhgad Institute of Technology and Science, Pune, 411041, India
Birgu N. Singh: Department of Aerospace Engineering, Indian institute of Technology, Kharagpur, 721302, India

Abstract
Simultaneous optimization of trusses which concurrently takes into account design variables related to the size, shape and topology of the structure is recognized as highly complex optimization problems. In this class of optimization problems, it is possible to encounter several unstable mechanisms throughout the solution process. However, to obtain a feasible solution, these unstable mechanisms somehow should be rejected from the set of candidate solutions. This study proposes triangular unit based method (TUBM) instead of ground structure method, which is conventionally used in the topology optimization, to decrease the complexity of search space of simultaneous optimization of the planar truss structures. TUBM considers stability of the triangular units for 2 dimensional truss systems. In addition, integrated particle swarm optimizer (iPSO) strengthened with robust technique so called improved fly-back mechanism is employed as the optimizer tool to obtain the solution for these class of problems. The results obtained in this study show the applicability and efficiency of the TUBM combined with iPSO for the simultaneous optimization of planar truss structures.

Key Words
triangular unit based method; particle swarm optimization; simultaneous optimization; truss structures

Address
Ali Mortazavi: Department of Civil Engineering Ege University, Izmir, Turkey
Vedat Toğan: Department of Civil Engineering, Karadeniz Technical University, 61080, Trabzon, Turkey

Abstract
This research presented a numerical and experimental study on the seismic performance of first-generation base-isolated and fixed-base nuclear power plants (NPP). Three types of the base isolation system were applied to rehabilitate the first-generation nuclear power plants: frictional pendulum (FP), high-damping rubber (HDR) and lead-rubber (LR) base isolation. Also, an Excel program was proposed for the design of the abovementioned base isolators in accordance with UBC 97 and the Japan Society of Base Isolation Regulation. The seismic assessment was performed using the pushover and nonlinear time history analysis methods in accordance with the FEMA 356 regulation. To validate the adequacy of the proposed design procedure, two small-scale NPPs were constructed at Universiti Teknologi Malaysia\'s structural laboratory and subjected to a pushover test for two different base conditions, fixed and HDR-isolated base. The results showed that base-isolated structures achieved adequate seismic performance compared with the fixed-base one, and all three isolators led to a significant reduction in the containment\'s tension, overturning moment and base shear.

Key Words
dynamic relaxation method; concentrated damping; form-finding; membrane structures

Address
Babak Farmanbordar and Azlan Bin Adnan: Engineering Seismology and Earthquake Engineering Research (e-SEER), Department of Structure and Materials, Universiti Teknologi Malaysia (UTM), 81300 Skudai, Johor Bahru, Malaysia
Mahmood Md. Tahir and Iman Faridmehr: UTM Construction Research Centre (CRC), Institute for Smart Infrastructures and Innovative Construction, Universiti, Teknologi Malaysia (UTM), Skudai, Johor Bahru, 81300, Malaysia

Abstract
This paper presents the application of multiple linear regression (MLR) and artificial neural network (ANN) techniques for developing the models to predict the unconfined compressive strength (UCS) and Brazilian tensile strength (BTS) of the fiber reinforced cement stabilized fly ash mixes. UCS and BTS is a highly nonlinear function of its constituents, thereby, making its modeling and prediction a difficult task. To establish relationship between the independent and dependent variables, a computational technique like ANN is employed which provides an efficient and easy approach to model the complex and nonlinear relationship. The data generated in the laboratory through systematic experimental programme for evaluating UCS and BTS of fiber reinforced cement fly ash mixes with respect to 7, 14 and 28 days\' curing is used for development of the MLR and ANN model. The data used in the models is arranged in the format of four input parameters that cover the contents of cement and fibers along with maximum dry density (MDD) and optimum moisture contents (OMC), respectively and one dependent variable as unconfined compressive as well as Brazilian tensile strength. ANN models are trained and tested for various combinations of input and output data sets. Performance of networks is checked withthe statistical error criteria of correlation coefficient (R), mean square error (MSE) and mean absolute error (MAE). It is observed that the ANN model predicts both, the unconfined compressive and Brazilian tensile, strength quite well in the form of R, RMSE and MAE. This study shows that as an alternative to classical modeling techniques, ANN approach can be used accurately for predicting the unconfined compressive strength and Brazilian tensile strength of fiber reinforced cement stabilized fly ash mixes.

Key Words
artificial neural network (ANN); backpropagation algorithm; multiplelinear regression (MLR); fly ash; unconfined compressive strength (UCS); Brazilian tensile strength (BTS)

Address
H. S. Chore: Department of Civil Engineering, DattaMeghe College of Engineering, Sector-3, Airoli, Navi Mumbai,
400708, Maharashtra, India
R.B. Magar: Department of Civil Engineering, School of Engineering Technology, I. Kalsekar Technical Campus,
Panvel, 410206, India

Abstract
This paper introduces the process for Multi-objective Optimization Framework (MOF) which mediates multiple conflicting design targets. Even though the extensive researches have shown the benefits of optimization in engineering and design disciplines, most optimizations have been limited to the performance-related targets or the single-objective optimization which seek optimum solution within one design parameter. In design practice, however, designers should consider the multiple parameters whose resultant purposes are conflicting. The MOF is a BIM-integrated and simulation-based parametric workflow capable of optimizing the configuration of building components by using performance and non-performance driven measure to satisfy requirements including build programs, climate-based daylighting, occupant

Key Words
genetic algorithm; multi-objective optimization; parametric and evolutionary design; BIM

Address
Bomin Kim: Architecture, Sasaki Associates, 64 Pleasant Street, Watertown, Massachusetts, 02472 United States
Youngjin Lee: Department of Architecture, Boston Architectural College, 320 Newbury Street, Boston, Massachusetts, 02115, United States


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