Abstract
This paper presents a simplified method for the design and analysis of non-prestressed, partially prestressed, and fully prestressed concrete beams subjected to pure torsion. The proposed model relates the torsional strength to the concrete compressive strength and to the amounts of transverse and longitudinal reinforcement. To check the adequacy of this simple method, the calculated strength and mode of failure are checked against the experimental results of 17 prestressed concrete 66 reinforced concrete beam tests available in the literature, and very good agreement is found. The simplicity of the method is illustrated by two examples, one for design and another for analysis.
Key Words
beams; code methods; design; mode of failure; prestressed concrete; reinforced concrete; shear; strength; torsion.
Address
Khaldoun N. Rahal, Department of Civil Engineering, Faculty of Engineering and Petroleum, Kuwait University, P.O. Box 5969, Safat 13060, Kuwait
Abstract
In this paper, a finite element with embedded displacement discontinuity which eliminates the need for remeshing of elements in the discrete crack approach is applied for the progressive fracture analysis of concrete structures. A finite element formulation is implemented with the extension of the principle of virtual work to a continuum which contains internal displacement discontinuity. By introducing a discontinuous displacement shape function into the finite element formulation, the displacement discontinuity is obtained within an element. By applying either a nonlinear or an idealized linear softening curve representing the fracture process zone (FPZ) of concrete as a constitutive equation to the displacement discontinuity, progressive fracture analysis of concrete structures is performed. In this analysis, localized progressive fracture simultaneous with crack closure in concrete structures under mixed mode loading is simulated by adopting the unloading path in the softening curve. Several examples demonstrate the capability of the analytical technique for the progressive fracture analysis of concrete structures.
Key Words
embedded displacement discontinuity; progressive fracture analysis; concrete structures; finite element method; discontinuous displacement shape function; softening curves; fracture process zone.
Address
Ha-Won Song, Byul Shim , Seung-Min Woo and Ja-Choon Koo, Department of Civil Engineering, Yonsei University, Seoul 120-749, Korea
Abstract
The purpose of this study is to investigate the effect of the shear wall location in rigid frames on the dynamic behavior of a roof structure due to vertical and horizontal earthquake motions. The study deals with a gabled long span beam supported by two story rigid frames with shear walls. The earthquake response analysis is carried out to study the responses of the roof: vibration mode, natural period, bending moment and horizontal shear force of the bearings. The study results in the following conclusions: First, a large horizontal stiffness difference between the side frames is caused by the shear wall location, which results in a large vertical vibration of the roof and a large shear force at the side bearings. Second, in this case, the seismic design method for ordinary buildings is not useful in determining the distribution of the static equivalent loads for the seismic design of this kind of long span structures.
Key Words
long span structure; earthquake response; horizontal rigidity; interaction of long span beam and bearing structure.
Address
Koichiro Ishikawa, Yoshizo Kawasaki and Kengo Tagawa, Department of Architecture and Civil Engineering, Fukui University, Fukui-shi 910-8507, Japan
Abstract
For the potential application of smart materials to seismic structural control, this paper reviews seismic control techniques for civil engineering structures, and developments of smart materials for vibration and noise control. Analytical and finite element methods adopted for the design of distributed sensors/ actuators using piezoelectric materials are discussed. Investigation of optimum position of sensors/actuators and damping are also outlined.
Key Words
smart materials; seismic vibration control; finite element.
Address
S. Valliappan and K. Qi, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia
Abstract
A structural analysis of cracked R.C. members under instantaneous or sustained loads and imposed displacements is presented. In the first part of the paper the problem of deriving feasible moment-curvature diagrams for a long term analysis of R.C. sections is approached in an exact way by using the Reduced Relaxation Function Method in state I uncracked and the method suggested by CEB in state II cracked. In both states the analysis of the main parameters governing the problem has shown that it is possible to describe the concrete creep behaviour in an approximate way by using the algebraic formulation connected to the Effective Modulus Method. In this way the calculations become quite simple and can be applied in design practice without introducing significant errors. Referring to continuous beams, the structural analysis is then approached in a general way, applying the Force Method and the Principle of Virtual Works. Finally, considering single members, the structural analysis is performed by means of a graphical procedure based on the application of feasible moment-rotation diagrams which allow to easily solve various structural problems and to point out the most interesting aspects of the long term behaviour of cracked R.C. members with rigid or elastically deformable redundant restraints.
Key Words
creep; cracking; relaxation; curvature; rotations; structural analysis.
Address
F. Mola, Department of Structural Engineering, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy M.C. Gatti, Rocksoil Consulting Engineering, Piazza San Marco 1, 20121 Milano, Italy G. Meda, INPRO Consulting Engineering, Viale Certosa 34, 20155 Milano, Italy
Abstract
In order to investigate the seismic behavior and seismic design methods in the transverse direction of a shield tunnel, a series of model shaking table tests and a two-dimensional finite element dynamic analysis on the tests are carried out. Two kinds of static analytical methods based on ground-tunnel composite finite element model and beam-spring element model are proposed, and the validity of the static analyses is verified by model shaking table tests. The investigation concerns the dynamic response behavior of a tunnel and the ground, the interaction between the tunnel and ground, and an evaluation of different seismic design methods. Results of the investigation indicate that the shield tunnel follows the surrounding ground in displacement and dynamic characteristics in the transverse direction; also, the static analytical methods proposed by the authors can be used directly as the seismic design methods in the transverse direction of a shield tunnel.
Address
Chuan He, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031, China Atsushi Koizumi, Department of Civil Engineering, Waseda University, Tokyo 169-8555, Japan
Abstract
Numerous failures in welded connections in steel moment-resisting building frames (SMRF) were observed when buildings were inspected after the 1994 Northridge Earthquake. These observations raised concerns about the effectiveness of such frames for resisting strong earthquake ground motions. The behavior of SMRFs during an earthquake must be assessed using nonlinear dynamic analysis, and such assessments must permit the deterioration in connection strength to capture the behavior of the frame. The uncertainties that underlie both structural and dynamic loading also need to be included in the analysis process. This paper describes the analysis of one of approximately 200 SMRFs that suffered damage to its welded beam-to-column connections from the Northridge Earthquake is evaluated. Nonlinear static and dynamic analysis of this SMRF in the time domain is performed using ground motions representing the Northridge Earthquake. Subsequently, a detailed uncertainty analysis is conducted for the building using an ensemble of earthquake ground motions. Probability distributions for deformation-related limit states, described in terms of maximum roof displacement or interstory drift, are constructed. Building fragilities that are useful for condition assessment of damaged building structures and for performance-based design are developed from these distributions.
Address
Jianlin Song and Bruce R. Ellingwood, Applied Insurance Research, 101 Huntington Ave., Boston, MA 02199-8001, U.S.A School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332, U.S.A
