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CONTENTS
Volume 3, Number 6, November 1995
 

Abstract
The rigid-plastic yield-line analysis of isotropically reinforced concrete slabs acting in conjunction with torsionally weak supporting beams is developed as the lower-bound form of a linear programming formulation. The analysis is extended to consider geometric variation of chosen yield-line patterns by the technique of sequential linear programming. A strategy is followed of using a fine potential yield-line mesh to identify possible collapse modes, followed by analysis using a coarser, simplified mesh to refine the investigation and for use in conjunction with geometric optimization of the yield-line system. The method is shown to be effective for the analysis of three slabs of varying complexity. The modes detected by the fine and simplified analyses are not always similar but close agreement in load factors has been consistently obtained.

Key Words
reinforced concrete, slab-beam systems, automated yield-line analysis, sequential linear programming

Address
Johnson D, NOTTINGHAM TRENT UNIV,DEPT CIVIL & STRUCT ENGN,NOTTINGHAM NG1 4BU,ENGLAND

Abstract
The determination of the stress intensity factors is investigated by using the surface integral defined around the crack tip of the structure. In this work, the integral method is derived naturally from the standard path integral J. But the use of the surface integral is also extended to the case where body forces act. Computer program for obtaining the stress intensity factors K-I and K-II is developed which prepares input variables from the result of the conventional finite element analysis. This paper provides a parabolic smooth curve function. By the use of the function and conventional element meshes in which the aspect ratio (element length at the crack tip/crack length) is about 25 percent, relatively accurate K-I and K-II values can be obtained for the outer integral radius ranging from 1/3 to 1 of the crack length and for inner one zero.


Key Words
stress intensity factor, J-integral, surface integral, smooth curve function

Address
Jin CS, PUSAN NATL UNIV,DEPT CIVIL ENGN,PUSAN 609735,SOUTH KOREA
PUSAN NATL UNIV,DEPT CIVIL ENGN,PUSAN 608080,SOUTH KOREA
PUSAN NATL UNIV,IND TECHNOL RES INST,PUSAN 609735,SOUTH KOREA

Abstract
Design curves have been prepared for prestressed rectangular beam section based on BS 8110, for determining area of steel for any given cross section, for stresses in concrete and steel and for the design moment. The design moment and the area of steel have been expressed in dimensionless form in terms of cross sectional dimensions and the characteristic strength of concrete. The choice and combination of design parameters result in considerably less number of curves as aid for design of rectangular prestressed beam sections, than those reported in CP 110 (Part 3).

Key Words
prestressed, concrete, beam, rectangular, design curves

Address
Subramaniam KVL, INDIAN INST TECHNOL,DEPT CIVIL ENGN,NEW DELHI 110016,INDIA

Abstract
In this paper, the seismic behavior of a 10-story building equipped with viscoelastic dampers is analyzed. The effects of ambient temperature, the thickness, the total area, and the position of the viscoelastic dampers are studied. Results indicate that the energy-absorbing capacity of viscoelastic damper decreases with increasing the ambient temperature. The thickness and the total area of viscoelastic dampers also affect the seismic mitigation capacity. The thickness cannot be too small, which is not effective in vibration reduction, nor can it be too large, which not only increases the cost but also reduces the seismic resistance. The total area of viscoelastic dampers should be determined properly for optimum damper performance at the most economical design. The mounting position of viscoelastic dampers also influences the structure\'s seismic performance. Numerical results show that, if properly equipped, the VE dampers can reduce the structural response both floor displacement and story shear force and increase the overall level of damping in structures during earthquakes.

Key Words
energy-absorbing device, viscoelastic damper, earthquake engineering, seismic mitigation, energy dissipation, structural dynamics, time-history analysis

Address
Pong WS, SUNY BUFFALO,DEPT CIVIL ENGN,BUFFALO,NY 14260

Abstract
The concept of \'\'Saturation Impulse\'\' for rigid, perfectly plastic structures with finite-deflections subjected to dynamic loading was put forward by Zhao, Yu and Fang (1994a). This paper extends the concept of Saturation Impulse to the analysis of structures such as simply supported circular plates, simply supported and fully clamped square plates, and cylindrical shells subjected to rectangular pressure pulses in the medium load range. Both upper and lower bounds of nondimensional saturation impulses are presented.


Key Words
structures, rigid, perfectly plastic, finite-deflections, rectangular pressure pulse, saturation impulse, lower bounds, upper bounds

Address
Zhao YP, CHINESE ACAD SCI,INST MECH,LNM,BEIJING 100080,PEOPLES R CHINA
HONG KONG UNIV SCI & TECHNOL,DEPT MECH ENGN,HONG KONG,HONG KONG
BEIJING UNIV,DEPT MECH,BEIJING 100871,PEOPLES R CHINA

Abstract
The presence of reinforcement has a significant influence on the stress-strain behaviour of reinforced concrete structures, expecially when the failure stage of the structures is approached. In the present paper, the constrained and non-constrained zones of concrete due to the presence of reinforcement is developed and the stress-stress-strain behaviour of concrete is enhanced by a reinforcement confinement coefficient, Furthermore, a flexible method for the modelling of reinforcement with arbitrary orientation and not passing the nodes of concrete element is also proposed. Numerical examples and laboratory tests have shown that the coefficient and the modelling technique proposed by the author are satisfactory.

Key Words
concrete, reinforcement, confinement, finite element

Address
Cheng YM, HONG KONG POLYTECH,DEPT CIVIL & STRUCT ENGN,HONG KONG,HONG KONG

Abstract
This paper is concerned with inelastic load carrying capacity of tapered steel members with or without accumulated plastic strains resulted from previous loading histories. A finite element program is developed using stiffness matrices of tapered members and is applicable for analyses with material and geometric nonlinearity. Results of analyses are compared with other available solutions and with experimental results.

Key Words
tapered member, inelastic buckling, accumulated strain

Address
Kim MC, SUNY BUFFALO,DEPT CIVIL ENGN,BUFFALO,NY 14260
NATL TAIWAN UNIV,DEPT CIVIL ENGN,TAIPEI 10764,TAIWAN


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