Toader Balan - Academia.edu (original) (raw)

Papers by Toader Balan

Earthquake Spectra, Nov 1, 1998

Strength of Materials, Jul 1, 1985

Strength of Materials, Oct 1, 1986

This report documents the installation and testing of a remote structural monitoring system and i... more This report documents the installation and testing of a remote structural monitoring system and its integration with modern finite element software to better assess the in-service performance of fatigue prone details on fracture critical bridges.

Roads and bridges, May 1, 2008

This article discusses some of the history and evolution of structural monitoring technologies, s... more This article discusses some of the history and evolution of structural monitoring technologies, starting with the first stand-alone systems, conceived in academia nearly 20 years ago. Ten years after that, commercial products began to come on the market. They integrated wireless data transmission and presentation of the captured data over the Internet. This made it possible to carry out near-real-time management. The latest generation of monitoring system uses finite-element modeling (FEM). Key components of a successful deployment of an FEM are described. FEMs must be properly calibrated and coupled with advanced monitoring techniques. When they are, they can reduce liability exposure, enhance a structure's life span and expand the safety envelop of older structures while lowering life-cycle costs. An FEM must also be closely integrated with a well-designed monitoring system.

Engineering Structures, Apr 1, 2001

This paper presents a hypoplastic model for three-dimensional analysis of concrete structures und... more This paper presents a hypoplastic model for three-dimensional analysis of concrete structures under monotonic, cyclic, proportional and non-proportional loading. The constitutive model is based on the concept of equivalent uniaxial strains that allow the assumed orthotropic model to be described via three equivalent uniaxial stress-strain curves. The characteristics of these curves are obtained from the ultimate strength surface in the principal stress space based on the Willam-Warnke curve. A cap model is added to consider loading along or near the hydrostatic axis. The equivalent uniaxial curve is based on the Popovics and Saenz models. The post-peak behavior is adjusted to account for the effects of confinement and to describe the change in response from brittle to ductile as the lateral confinement increases. Correlation studies with available experimental tests are presented to demonstrate the model performance. Tests with monotonic loading on specimens under constant lateral confinement are considered first, followed by biaxial and triaxial tests with cyclic loads. The triaxial test example considers non-proportional loading.

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Roads and bridges, May 1, 2006

International Applied Mechanics, Mar 1, 1985

Satisfying the boundary conditions in Eq. (1.3), the system of linear algebraic equations in Eq. ... more Satisfying the boundary conditions in Eq. (1.3), the system of linear algebraic equations in Eq. (i.ii) is obtained; solving Eq. (i.i!), the unknown values of contour functions are found and then the approximate solution of the initial problem is found from Eq. (I.i0). The central axis of the element may be written in the normalized coordinates ~ in the form

Strength of Materials, 1986

CONCLUSIONS i. Equations were derived for the quantitative determination of the accuracy of the m... more CONCLUSIONS i. Equations were derived for the quantitative determination of the accuracy of the method of prediction of the endurance of the structural member in the creep conditions. The method is based on the application of the criteria of linear fracture mechanics.

This paper discusses enhancements to an existing concrete constitutive model for the 3-D finite e... more This paper discusses enhancements to an existing concrete constitutive model for the 3-D finite element analysis of reinforced concrete structures. The model is based on the concept of equivalent uniaxial strain that allows the use of a uniaxial constitutive law for concrete. The main features of the constitutive law are presented. The focus is on the cyclic uniaxial constitutive law and on the post-peak behavior necessary to describe the response of concrete under triaxial states of stress. Unconfined and confined compression tests on concrete specimens are used to validate the material law under different levels of confinement.

Bridges, Nov 1, 2006

In 2005, the Pennsylvania Turnpike Commission (PTC) agreed to implement a pilot remote health mon... more In 2005, the Pennsylvania Turnpike Commission (PTC) agreed to implement a pilot remote health monitoring (RHM) system on the Hawk Falls Bridge in Beaver County, Pennsylvania. This article describes the RHM system and explains how its data can be used in asset management applications. The proposed system consisted of three fundamental components: (1) permanent dual-channel strain sensors with memory capability to record both peak strain and active strain; (2) a secure, hard-wired installation and onsite data acquisition control box that records sensor data and then transmits it via wireless communication technology; and (3) a remote network operations center where data is received and stored and made available to PTC management through a password-protected Internet connection. Coupling the RHM system data stream with a three-dimensional finite element model of the structure resulted in Pennsylvania's first "smart bridge." Major benefits of the smart bridge system include assurance of reliable bridge performance, more predictable bridge response and better allocation of financial resources for maximum return on investment.

1. Stress. 2. Strain. 3. Axial Deformation of Bars: Statically Determinate Systems. 4. Axial Defo... more 1. Stress. 2. Strain. 3. Axial Deformation of Bars: Statically Determinate Systems. 4. Axial Deformation of Bars: Statically Indeterminate Systems. 5. Generalized Hooke's Law: Pressure Vessels. 6. Torsion. 7. Beam Statics. 8. Symmetric Beam Bending. 9. Unsymmetric (Skew) Beam Bending. 10. Shear Stresses in Beams. 11. Stress and Strain Transformation. 12. Yield and Fracture Criteria. 13. Elastic Stress Analysis. 14. Beam Deflections by Direct Integration. 15. Beam Deflections by the Moment-area Method. 16. Columns. 17. Energy and Virtual Work. 18. Classical Energy Methods. 19. Elastic Analysis of Systems. 20. Plastic Limit Analysis. Tables. Answers to Odd-numbered Problems. Index. Conversion Factors between U.S. Customary and SI Units.

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Earthquake Spectra, 1998

After the 1994 Northridge earthquake a tremendous amount of research activity was generated in th... more After the 1994 Northridge earthquake a tremendous amount of research activity was generated in the United States. In this paper on introducing the basic concepts of seismic design, and illustrating a typical pre-Northridge earthquake steel connection, the fundamental reasons of the poor behavior of the connections are discussed. Then the development of the so-called Dog Bone connection is brought in. Experimental results on two connections of this type are discussed in detail. The reasons for good behavior of Dog Bone connections are then explained using three-dimensional von Mises yield criterion. This new analytical demonstration provides solid evidence as to why the Dog Bone connections behave well. The problem of torsional instability of these connections is not considered.

Roads Bridges, May 1, 2008

Journal of Structural Engineering, 1998

International Applied Mechanics - INT APPL MECH-ENGL TR, 1985

Journal of Engineering Mechanics, 1997