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CONTENTS
Volume 46, Number 6, June25 2013
 

Abstract
One of the main requirements of the seismic design codes must be its easy application by structural engineers. The use of practically-applicable models or simplified models as single-degree-offreedom (SDOF) systems is a good alternative to achieve this condition. In this study, deterministic and probabilistic response transformation factors are obtained to evaluate the response in terms of maximum ductility and maximum interstory drifts of multi-degree-of-freedom (MDOF) systems based on the response of equivalent SDOF systems. For this aim, five steel frames designed with the Mexican City Building Code (MCBC) as well as their corresponding equivalent SDOF systems (which represent the characteristics of the frames) are analyzed. Both structural systems are subjected to ground motions records. For the MDOF and the simplified systems, incremental dynamic analyses IDAs are developed in first place, then, structural demand hazard curves are obtained. The ratio between the IDAs curves corresponding to the MDOF systems and the curves corresponding to the simplified models are used to obtain deterministic response transformation factors. On the other hand, demand hazard curves are used to calculate probabilistic response ransformation factors. It was found that both approaches give place to similar results.

Key Words
response transformation factors; maximum ductility; maximum interstory drift; steel frames; reliability-based seismic design

Address
Edén Bojórquez, Alfredo Reyes-Salazar, and Juan Velázquez-Dimas : Facultad de Ingeniería, Universidad Autónoma de Sinaloa, Calzada de las Américas y B. Universitarios s/n,
80040 Culiacán, Mexico
Juan Bojórquez, Sonia E. Ruiz : Mecánica Aplicada, Instituto de Ingeniería, Universidad Nacional Autónoma de México, Mexico

Abstract
Deformation analysis is a major concern in many geotechnical applications. In this paper, the deformation behavior of a geocell mattress subjected to symmetric loads was studied. The mattress was idealized as an elastic foundation beam. The horizontal beam-soil interfacial shear resistances at the beam top and bottom sides were taken into account by assuming the resistances to be linear with the relative horizontal displacements. A decoupled iterative method was employed to solve the differential displacement equations derived from the force analysis of a beam element and to obtain the solutions for the deformations and internal forces of the geocell reinforcement. The validity of the present solutions was verified by the existing finite element method and power-series solutions.

Key Words
geocell mattress; Winkler foundation; beam-soil interfacial shear resistance; decoupled iteration method

Address
Ling Zhang, Minghua Zhao and Heng Zhao : College of Civil Engineering, Hunan University, 410082 Changsha, China

Abstract
The main purpose of this paper is to develop seismic fragility curves for existing reinforced concrete, RC, buildings based on the post earthquake field survey and the seismic performance using capacity design. Existing RC buildings constitute approximately 65% of the total stock in Algiers. This type of buildings, RC, was widely used in the past and chosen as the structural type for the future construction program of more than 2 millions apartments all over Algeria. These buildings, suffered moderate to extensive damage after the 2003 Boumerdes earthquake, on May 21st. The determination of analytical seismic fragility curves for low-rise and mid-rise existing RC buildings was carried out based on the consistent and complete post earthquake survey after that event. The information on the damaged existing RC buildings was investigated and evaluated by experts. Thirty four (34) communes (districts) of fifty seven (57), the most populated and affected by earthquake damage were considered in this study. Utilizing the field observed damage data and the Japanese Seismic Index Methodology, based on the capacity design method. Seismic fragility curves were developed for those buildings with a large number data in order to get a statistically significant sample size. According to the construction period and the code design, four types of existing RC buildings were considered. Buildings designed with pre-code (very poor structural behavior before 1955), Buildings designed with low code (poor structural behavior, between 1955-1981), buildings designed with medium code (moderate structural behavior, between 1981-1999) and buildings designed with high code (good structural behavior, after 1999).

Key Words
reinforced concrete; existing building; post earthquake survey; seismic damage assessment; seismic index method; capacity design; fragility curves

Address
Youcef Mehani, Hakim Bechtoula, Abderrahmane Kibboua and Mounir Naili : National Earthquake Engineering Center, CGS, 01, Rue Kaddour RAHIM, BP 252, Hussein Dey, Alger, Algeria

Abstract
In the present study, in reinforced concrete structures, beam-column connections are one of the most critical regions in areas with seismic susceptibility. Proper anchorage of reinforcement is vital to enhance the performance of beam-column joints. Congestion of reinforcement and construction difficulties are reported frequently while using conventional reinforcement detailing in beam-column joints of reinforced concrete structures. An effort has been made to study and evaluate the performance of beamcolumn joints with joint detailing as per ACI-352 (mechanical anchorage), ACI-318 (conventional hooks bent) and IS-456(full anchorage conventional hooks bent) along with confinement as per IS-13920 and without confinement. Apart from finding solutions for these problems, significant improvements in seismic performance, ductility and strength were observed while using mechanical anchorage in combination with X-cross bars for less seismic prone areas and X-cross bar plus hair clip joint reinforcement for higher seismic prone areas. To evaluate the performances of these types of anchorages and joint details, the specimens were assembled into four groups, each group having three specimens have been tested under reversal loading and the results are presented in this paper.

Key Words
reinforced concrete structure; beam-column connection; seismic; ductility; mechanical anchorage

Address
S. Rajagopal and S. Prabavathy : Department of Civil Engineering, Mepco Schlenk Engineering College, Sivakasi, Tamil Nadu 626 005, India

Abstract
In this paper, the wave propagation in generalized thermo elastic plate immersed in fluid is studied based on the Lord-Shulman (LS) and Green-Lindsay (GL) generalized two dimensional theory of thermo elasticity. Two displacement potential functions are introduced to uncouple the equations of motion. The frequency equations that include the interaction between the plate and fluid are obtained by the perfectslip boundary conditions using the Bessel function solutions. The numerical calculations are carried out for the material Zinc and the computed non-dimensional frequency, phase velocity and attenuation coefficient are plotted as the dispersion curves for the plate with thermally insulated and isothermal boundaries. The wave characteristics are found to be more stable and realistic in the presence of thermal relaxation times and the fluid interaction.

Key Words
solid-fluid interface; wave propagation; vibration of thermal plate; plate immersed in fluid; generalized thermo elastic plate; ultrasonic transducers and resonators

Address
R. Selvamani : Department of Mathematics, Karunya University, Coimbatore,Tamil Nadu, India
P. Ponnusamy : Department of Mathematics,Government Arts College (Autonomous), Coimbatore, Tamil Nadu, India

Abstract
This paper presents results of the effect of different bolt tightening sequences and methods on the performance of gasketed bolted flange joint using nonlinear finite element analysis. Bolt preload scatter due to elastic interactions, flange stress variation and bolt bending due to flange rotation and gasket contact stress variation is difficult to eliminate in torque control method i.e. tightening one bolt at a time. Although stretch control method (tightening more than one bolt at time) eradicates the bolt preload scatter, flange stress variation is relatively high. Flange joint\'s performance is compared to establish relative merits and demerits of both the methods and different bolt tightening sequences.

Key Words
bolted flange joint; assembly process; torque control; stretch control; elastic interaction; tightening sequence; finite element analysis

Address
Muhammad Abidand Yasir Mehmood Khan : Faculty of Mechanical Engineering, Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi, Pakistan

Abstract
The comparison of the effectiveness of artificial neural network (ANN) and linear regression (LR) in the prediction of strain in tie section using experimental data from eight high-strength-self-compactconcrete (HSSCC) deep beams are presented here. Prior to the aforementioned, a suitable ANN architecture was identified. The format of the network architecture was ten input parameters, two hidden layers, and one output. The feed forward back propagation neural network of eleven and ten neurons in first and second TRAINLM training function was highly accurate and generated more precise tie strain diagrams compared to classical LR. The ANN\'s MSE values are 90 times smaller than the LR\'s. The correlation coefficient value from ANN is 0.9995 which is indicative of a high level of confidence.

Key Words
strain; deep beams; artificial neural network; STM; linear regression

Address
Mohammad Mohammadhassani, Meldi Suhatril and Mahdi Shariati : Department of Civil Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
Hossein Nezamabadi-pour : Department of Electrical Engineering, Shahid Bahonar University of Kerman, Iran

Abstract
This work presents an experimental methodology specially developed for the nonlinear largeamplitude free vibration analysis of a clamped-free thin-walled metal column under self-weight. The main contribution of this paper is related to the developed experimental methodology which is based on a remote sensing technique using a computer vision system that integrates, on-line, the digital image acquisition and its treatment through special image processing routines. The main importance of this methodology is that it performs large deflections measurements without making contact with the structure and thus, not introducing undesirable changes in its behavior, for instance, appreciable changes in mass and stiffness properties. This structure presents, in most cases, highly non-linear responses, which cannot be reproduced by conventional finite-element softwares due, mainly, to the simultaneous influence of geometric and inertial non-linearities. To capture the non-linearities associated with large amplitude vibration and be able to describe the buckling process, the structure is discretized as a sequence of jointed coupled elastic pendulums. The obtained numerical results are favorably compared with the experimental ones, in the preand post-buckling regimes.

Key Words
nonlinear vibrations; large deflection behavior; softening phenomenon; dynamic experimental analysis; digital image processing; non-contact displacement measurements

Address
Paulo B. Gonçalves : Department of Civil Engineering, Catholic University, PUC-Rio, 22453-900, Rio de Janeiro, RJ, Brazil
Daniel Leonardo B.R. Jurjo, Carlos Magluta and Ney Roitman : Department of Civil Engineering, Federal University of Rio de Janeiro, COPPE/UFRJ, Rio de Janeiro, RJ, Brazil


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