The Experts below are selected from a list of 24 Experts worldwide ranked by ideXlab platform
Jian Yu Zeng - One of the best experts on this subject based on the ideXlab platform.
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Internal Force System and Current Secondary Moment Concept in Prestressed Structures
Applied Mechanics and Materials, 2014Co-Authors: Jian Yu ZengAbstract:The Internal Forces in a prestressed concrete structure are of special nature due to the existence of tendons. And flaws can be found in the traditional concept of secondary moment such that common computation method of secondary moment may produce unreasonable results. This article aims at getting a better understanding of Internal Forces in prestressed structures and solving the relevant problems. Starting from the basic principles of Internal Force analysis, a new System of Internal Forces is put forward by which the relationship between the compression resultant on concrete cross-section and the sectional Internal Forces is made clear. On this basis, a definition on the concept of current secondary moment (Mcs) is proposed and its superiority pointed out. Finally, theoretical analyses are carried out on the method for calculating Mcs in the posttentioned continuous beams with unbonded and bonded prestressing tendons.
Katalin Bagi - One of the best experts on this subject based on the ideXlab platform.
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When Heyman’s Safe Theorem of rigid block Systems fails: Non-Heymanian collapse modes of masonry structures
International Journal of Solids and Structures, 2014Co-Authors: Katalin BagiAbstract:Abstract Heyman’s Safe Theorem is the theoretical basis for several calculation methods in masonry analysis. According to the theorem, the existence of an Internal Force System which equilibrates the external loads guarantees that the masonry structure is in a stable equilibrium state, assuming that a few conditions on the material behaviour are satisfied: the stone blocks have infinite compressional resistance, and the contacts between them resist only compression and friction. This paper presents simple examples in which the Safe Theorem fails: collapse occurs in spite of the existence of an equilibrated Force System. A theoretical analysis of the stability of assemblies of rigid blocks with frictional contacts is then introduced: the virtual work theorem is derived, and a refined formulation of the Safe Theorem is given.
T.h.g. Megson - One of the best experts on this subject based on the ideXlab platform.
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Stress and Strain
Structural and Stress Analysis, 2014Co-Authors: T.h.g. MegsonAbstract:There are only two types of stresses—one that acts perpendicularly to the cross section of a member and the other that acts tangentially. The former is known as a direct stress, and the latter as a shear stress. The distribution of these stresses over the cross section of a structural member depends upon the Internal Force System at the section and also upon the geometry of the cross section. In some cases, these distributions are complex, particularly those produced by the bending and shear of unsymmetrical sections. This chapter examines the nature of each of these stresses by considering simple loading Systems acting on structural members whose cross sections have some degree of symmetry. A System of shear stresses is induced in a different way in the circular-section bar where the Internal torque (T) tends to produce a relative rotational sliding of the two faces of the cross section. The shear stresses are tangential to concentric circular paths in the faces of the cross section.
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Chapter 7 – Stress and Strain
Structural and Stress Analysis, 2005Co-Authors: T.h.g. MegsonAbstract:Publisher Summary There are only two types of stresses—one that acts perpendicularly to the cross section of a member and the other that acts tangentially. The former is known as a direct stress, and the latter as a shear stress. The distribution of these stresses over the cross section of a structural member depends upon the Internal Force System at the section and also upon the geometry of the cross section. In some cases, these distributions are complex, particularly those produced by the bending and shear of unsymmetrical sections. This chapter examines the nature of each of these stresses by considering simple loading Systems acting on structural members whose cross sections have some degree of symmetry. A System of shear stresses is induced in a different way in the circular-section bar where the Internal torque (T) tends to produce a relative rotational sliding of the two faces of the cross section. The shear stresses are tangential to concentric circular paths in the faces of the cross section.
Martin H. Sadd - One of the best experts on this subject based on the ideXlab platform.
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Force and Stress
Continuum Mechanics Modeling of Material Behavior, 2019Co-Authors: Martin H. SaddAbstract:Abstract Chapter 3 investigated the kinematics of continuum deformation regardless of the Force or stress distribution that produced the motion or deformation. In this chapter, we now wish to examine how these Forces and stresses can be quantitatively described. Following the classical continuum mechanics model, we assume a continuously distributed Internal Force System composed of body and surface Forces. Each of these will be associated with a continuous density function that will represent the Force per unit volume or per unit surface area. For surface Forces, this will lead to the definition and use of the stress or traction vector and stress tensor. Each of these provides a quantitative method to describe both boundary and Internal Force distributions within a continuum. Since stress is related to Force per unit area, we will have to keep track of whether we wish to use reference or current areas for large deformation problems. Stress is very important in continuum mechanics applications, because many materials exhibit some type of failure condition based on this variable. It should be noted that the developments in this chapter will not require a material constitutive assumption and thus they will apply to a broad class of material behavior.
Evangelos I. Stavridakis - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Engineering and Cement–Stabilization Parameters of Clayey–Sand Mixtures under Soaked Conditions
Geotechnical & Geological Engineering, 2005Co-Authors: Evangelos I. StavridakisAbstract:Clay soils, especially clay soils of high or very high swelling potential often present difficulties in construction operations. However, the engineering properties of these clay soils can be enhanced by the addition of cement, thereby producing an improved construction material. Higher strength loss of cement stabilized clay soils after soaking in water is attributed to water absorbing capacity of the clay fraction (e.g. montmorillonite). Kaolinite and illitic soils are largely inert and resist to water penetration. These clays generally develop satisfactory strengths resulting to low strength reduction [Croft, 1967]. The swelling clays such as bentonite soaked in water, due to environmental conditions, result to volume increase causing macro and micro-fracturing in engineering structures. These fractures accelerate water penetration and consequently cause greater strength loss [Sällfors and Öberg-Högsta, 2002]. The water intrusion during soaking creates swelling and disrupts the cement bonds. The development of Internal and external Force Systems in soil mass, due to soaking conditions, establish the initiation of slaking. Internal Force System of a stabilized clayey soil consists of the resultant stresses established by the bonding potential of a cementing agent and the swelling potential of a clay fraction. In an effort to study this influence of soaking conditions and final absorbed water content on the stabilization parameters (cement, compaction, curing time), both unconfined compressive strength and slaking (durability) tests were carried out on two different cement stabilized clayey mixtures consisted of active bentonite, kaolin and sand.