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CONTENTS
Volume 6, Number 2, March 1998
 

Abstract
Recent test results of steel moment connections repaired with a haunch on the bottom side of the beam have been shown to be a very promising solution to enhancing the seismic performance of steel moment-resisting frames. Yet, little is known about the effects of using such a repair scheme on the global seismic response of structures. When haunches are incorporated in a steel moment frame, the response prediction is complicated by the presence of \"dual\" panel zones. To investigate the effects of a repair on seismic performance, a case study was conducted for a 13-story steel frame damaged during the 1994 Northridge earthquake. It was assumed that only those locations with reported damage would be repaired with haunches. A new analytical modeling technique for the dual panel zone developed by the author was incorporated in the analysis. Modeling the dual panel zone was among the most significant consideration in the analyses. Both the inelastic static and dynamic analyses did not indicate detrimental side effects resulting from the repair. As a result of the increased strength in dual panel zones, yielding in these locations were eliminated and larger plastic rotation demand occurred in,the beams next to the shallow end of the haunches. Nevertheless, the beam plastic rotation demand produced by the Sylmar record of 1994 Northridge earthquake was still limited to 0.017 radians. The repair resulted in a minor increase in earthquake energy input. In the original structure, the panel zones should dissipate about 80% (for the Oxnard record) and 70% (for the Sylmar record) of the absorbed energy, assuming no brittle failure of moment connections. After repair, the energy dissipated in the panel zones and beams were about equal.

Key Words
steel moment-resisting frame, connection, dual panel zone, haunch, repair, seismic

Address
Lee CH, Kyungnam Univ, Coll Engn, Dept Architectural Engn, Masan 631701, Kyungnam, South Korea
Kyungnam Univ, Coll Engn, Dept Architectural Engn, Masan 631701, Kyungnam, South Korea

Abstract
The objective of this present work is to estimate the failure loads, associated maximum transverse displacements, locations and the modes of failure, including the onset of delamination, of thin, square: symmetric laminates under the action in-plane positive (+ve) shear load. Two progressive failure analyses, one using the Hashin criterion and the other using a Tensor polynomial criterion, are used in conjunction with finite element method. First order shear deformation theory along with geometric nonlinearity in the von Karman sense have been employed. Variation of failure loads and failure characteristics with five type of lay-ups and three types of boundary conditions has been investigated in detail. It is observed that the maximum difference between failure loads predieted by various criteria depends strongly on the laminate lay-up and the flexural boundary restraint. Laminates with clamped edges an found to be more susceptible to failure due to transverse shear (ensuing from the out of plane bending) and delamination, while those with simply supported edges undergo total collapse at a load slightly higher than the fiber failure load. The investigation on negative (-ve) in-plane shear load is in progress and will be communicated as part-II of the present work.

Key Words
progressive failure, laminated plate, failure criteria, in-plane positive shear

Address
Singh SB, Indian Inst Technol, Dept Appl Mech, Kanpur 208016, Uttar Pradesh, India
Indian Inst Technol, Dept Appl Mech, Kanpur 208016, Uttar Pradesh, India
Indian Inst Technol, Dept Civil Engn, Kanpur 208016, Uttar Pradesh, India
Indian Inst Technol, Dept Aerosp Engn, Kanpur 208016, Uttar Pradesh, India

Abstract
Reinforced concrete beams possess variable flexural and torsional stiffnesses due to formation of cracks in the tension area along the beam. Zn order to check the stability of the beam, it is thus more appropriate to divide the beam into a finite number of segments for which mean stiffnesses and also bending moments are calculated. The stability analysis is further simplified, by using these mean values for each segment. In this paper, an algorithm for calculating the critical lateral buckling slenderness ratio for a definite load level, in a reinforced concrete beam without lateral support at the flanges, is presented. By using this ratio, the lateral buckling safety level of a slender beam may be checked or estimated.

Key Words
reinforced concrete beams, slenderness, lateral buckling

Address
Aydin R, Osmangazi Univ, Dept Civil Engn, Fac Engn & Architecture, TR-26030 Eskisehir, Turkey
Osmangazi Univ, Dept Civil Engn, Fac Engn & Architecture, TR-26030 Eskisehir, Turkey

Abstract
In the shape design of flexible structures. it is useful to predict the initial shape from the desirable large deformed shapes under some loading conditions. In this paper, we present a numerical procedure of an initial shape determination problem for hyperelastic materials which enables us to calculate an initial shape corresponding to the prescribed deformed shape and boundary condition. The present procedure is based on an Arbitrary Lagrangian-Eulerian (ALE) finite element method for hyperelasticity, in which arbitrary change of shapes in both the initial and deformed states can be treated by considering the variation of geometric mappings in the equilibrium equation. Then the determination problem of the initial shape can be formulated as a nonlinear problem to solve the unknown initial shape for the specified deformed shape that satisfies the equilibrium equation. The present approach can be implemented easily to the finite element method by employing the isoparametric hypothesis. Some basic numerical results are also given to characterize the present procedure.


Key Words
initial shape determination, incompressible hyperelasticity, arbitrary Lagrangian-Eulerian, finite element method

Address
Yamada T, Sci Univ Tokyo, Fac Engn, Dept Architecture, Shinjuku Ku, 1-3 Kagurazaka, Tokyo 162, Japan
Sci Univ Tokyo, Fac Engn, Dept Architecture, Shinjuku Ku, Tokyo 162, Japan

Abstract
Space truss design usually involves two main assumptions: that truss members are pin-ended, and compression members possess brittle post-buckling characteristics. The validity of these assumptions in the design of a new group of space trusses with continuous chords and eccentric joints is questionable. With chord member continuity and the consequent improvement in compression member behaviour, current design practice might be too conservative. In this paper, it is shown that substantial improvements in overall truss strength have resulted when the true member end conditions are considered, thus indicating potential savings in truss weight with considerable magnitudes.

Key Words
space trusses, jointing systems, design

Address
El-Sheikh A, Univ Dundee, Dept Civil Engn, Dundee DD1 4HN, Scotland
Univ Dundee, Dept Civil Engn, Dundee DD1 4HN, Scotland

Abstract
The structural behavior of reinforced concrete frame infilled with a masonry wall is investigated by the method of discontinuous deformation analysis (DDA). An interface element is developed and it is incorporated into DDA to analyze the continuous and discontinuous behavior of the masonry structure. The numerical results are compared with previous research and possess satisfactory agreement. Then the structural behavior and stress distribution of a reinforced concrete frame infilled with a masonry wall subjected to a horizontal force are studied. In addition, the justification of equivalent strut is assessed by the distribution of principal stresses. The results show that the behavior of the masonry structure is highly influenced by the failure of mortar. On the basis of the distribution of principal stress of the masonry wall in the reinforced concrete frame, the equivalent strut can be approximately substituted for the masonry wall without separation and opening. However, the application of equivalent strut to the masonry wall with separation and opening needs further study.

Key Words
discontinuous deformation analysis, reinforced concrete building, masonry wall

Address
Chiou YJ, Natl Cheng Kung Univ, Dept Civil Engn, Tainan 701, Taiwan
Natl Cheng Kung Univ, Dept Civil Engn, Tainan 701, Taiwan

Abstract
An elasto-plastic finite element procedure using degenerated shell element with assumed strain field technique considering both material and geometric nonlinearities has been developed. This assumes von-Mises yield criterion, von-Karman strain displacement relations and isotropic hardening. A few numerical examples are presented to demonstrate the correctness and applicability of the method to different kinds of engineering problems. From present study, it is seen that there is a considerable improvement in the displacement valuse when both material and geometric nonlinearities are considered. An example of the spread of plastic zones for isotropic and anisotropic materials has been illustrated.

Key Words
elasto-plastic, shell element, FEM, non-linear and Lagrangian in blank space

Address
Prasad NS, Indian Inst Technol, Dept Mech Engn, Madras 600036, Tamil Nadu, India
Indian Inst Technol, Dept Mech Engn, Madras 600036, Tamil Nadu, India

Abstract
In this study, a theoretical method to analyze the vibration of a T-type Timoshenko frame is proposed. The effects of axial inertia, rotatory inertia and shear deformation of each branch are considered. The orthogonality of any two distinct sets of mode shape functions is also demonstrated. Vibration of the frame due to moving loads is studied by the method and the response characteristics of the frame are investigated. Furthermore, the effect of column length on the response of the frame is also studied.


Key Words
Timoshenko frame, orthogonality, moving loads

Address
Wang RT, Natl Cheng Kung Univ, Dept Engn Sci, Tainan 70101, Taiwan
Natl Cheng Kung Univ, Dept Engn Sci, Tainan 70101, Taiwan


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