|
Lumped Damage Mechanics
Lumped damage mechanics or LDM is a branch of structural mechanics that is concerned with the analysis of frame structures. It is based on continuum damage mechanics and fracture mechanics. It combines the ideas of these theories with the concept of plastic hingeMarante, M.E., Flórez-López, J., “Three-Dimensional Analysis Of Reinforced Concrete Frames Based On Lumped Damage Mechanics” International Journal of Solids and Structures Vol 40, No 19, 5109-5123, 2003. LDM can be defined as the fracture mechanics of complex structural systems. In the models of LDM, cracking or local buckling as well as plasticity are lumped at the inelastic hinges. As in continuum damage mechanics, LDM uses state variables to represent the effects of damage on the remaining stiffness and strength of the frame structure. In reinforced concrete structures, the damage state variable quantifies the crack density in the plastic hinge zone; in unreinforced concrete components and steel beams, it is a dimens ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structural Mechanics
Structural mechanics or mechanics of structures is the computation of deformations, deflections, and internal forces or stresses (''stress equivalents'') within structures, either for design or for performance evaluation of existing structures. It is one subset of structural analysis. Structural mechanics analysis needs input data such as structural loads, the structure's geometric representation and support conditions, and the materials' properties. Output quantities may include support reactions, stresses and displacements. Advanced structural mechanics may include the effects of stability and non-linear behaviors. Mechanics of structures is a field of study within applied mechanics that investigates the behavior of structures under mechanical loads, such as bending of a beam, buckling of a column, torsion of a shaft, deflection of a thin shell, and vibration of a bridge. There are three approaches to the analysis: the energy methods, flexibility method or direct stiffn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Damage Mechanics
Damage mechanics is concerned with the representation, or modeling, of damage of materials that is suitable for making engineering predictions about the initiation, propagation, and fracture of materials without resorting to a microscopic description that would be too complex for practical engineering analysis. Damage mechanics illustrates the typical engineering approach to model complex phenomena. To quote Dusan Krajcinovic, "It is often argued that the ultimate task of engineering research is to provide not so much a better insight into the examined phenomenon but to supply a rational predictive tool applicable in design." Damage mechanics is a topic of applied mechanics that relies heavily on continuum mechanics. Most of the work on damage mechanics uses state variables to represent the ''effects'' of damage on the stiffness and remaining life of the material that is damaging as a result of thermomechanical load and ageing. The state variables may be measurable, e.g., crack den ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fracture Mechanics
Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material's resistance to fracture. Theoretically, the stress ahead of a sharp crack tip becomes infinite and cannot be used to describe the state around a crack. Fracture mechanics is used to characterise the loads on a crack, typically using a single parameter to describe the complete loading state at the crack tip. A number of different parameters have been developed. When the plastic zone at the tip of the crack is small relative to the crack length the stress state at the crack tip is the result of elastic forces within the material and is termed linear elastic fracture mechanics (LEFM) and can be characterised using the stress intensity factor K. Although the load on a crack can be arbitrary, in 1957 G. Irwin foun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plastic Hinge
In the structural engineering beam theory, plastic hinge is the deformation of a section of a Beam (structure), beam where plastic bending occurs. In earthquake engineering plastic hinge is also a type of energy Damping ratio, damping device allowing Plasticity (physics), plastic rotation [deformation] of an otherwise rigid column connection. Plastic behaviour In plastic Limit state design, limit analysis of structural members subjected to bending, it is assumed that an abrupt transition from elastic to ideally plastic behaviour occurs at a certain value of moment, known as plastic moment (Mp). Member behaviour between Myp and Mp is considered to be elastic. When Mp is reached, a plastic hinge is formed in the member. In contrast to a frictionless hinge permitting free rotation, it is postulated that the plastic hinge allows large rotations to occur at constant plastic moment Mp. Plastic hinges extend along short lengths of beams. Actual values of these lengths depend on cross-s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Structural System
The term structural system or structural frame in structural engineering refers to the load-resisting sub-system of a building or object. The structural system transfers loads through interconnected elements or members. Commonly used structures can be classified into five major categories, depending on the type of primary stress that may arise in the members of the structures under major design loads. However any two or more of the basic structural types described in the following may be combined in a single structure, such as a building or a bridge in order to meet the structure's functional requirements.Kassimali, A. (1999). ''Structural analysis''. 2nd edition. Pacific Grove, C.A.: PWS Publication. * Tensile structures: Members of tensile structures are subject to pure tension under the action of external loads. Because the tensile stress is uniformly distributed over the cross-sectional area of members, the material of such a structure is utilized in the most efficient ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
State Variables
A state variable is one of the set of variables that are used to describe the mathematical "state" of a dynamical system. Intuitively, the state of a system describes enough about the system to determine its future behaviour in the absence of any external forces affecting the system. Models that consist of coupled first-order differential equations are said to be in state-variable form. Examples *In mechanical systems, the position coordinates and velocities of mechanical parts are typical state variables; knowing these, it is possible to determine the future state of the objects in the system. *In thermodynamics, a state variable is an independent variable of a state function. Examples include internal energy, enthalpy, temperature, pressure, volume and entropy. Heat and work are not state functions, but process functions. *In electronic/electrical circuits, the voltages of the nodes and the currents through components in the circuit are usually the state variables. In an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reinforced Concrete
Reinforced concrete, also called ferroconcrete or ferro-concrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars (known as rebar) and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials. In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion. Description Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and/or structural failure. Modern reinforced concrete can contain varied reinforcing materials made o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Energy Release Rate
In fracture mechanics, the energy release rate, G, is the rate at which energy is Energy transformation, transformed as a material undergoes fracture. Mathematically, the energy release rate is expressed as the decrease in total potential energy per increase in fracture surface area, and is thus expressed in terms of energy per unit area. Various Conservation of energy, energy balances can be constructed relating the energy released during fracture to the energy of the resulting new surface, as well as other Dissipation, dissipative processes such as plasticity (physics), plasticity and heat generation. The energy release rate is central to the field of fracture mechanics when solving problems and estimating material properties related to fracture and fatigue (material), fatigue. Definition The energy release rate G is defined as the instantaneous loss of total potential energy \Pi per unit crack growth area s, : G \equiv -\frac , where the total potential energy is wri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stress Intensity Factor
In fracture mechanics, the stress intensity factor () is used to predict the Stress (mechanics), stress state ("stress intensity") near the tip of a Fracture, crack or Notch (engineering), notch caused by a remote load or residual stresses. It is a theoretical construct usually applied to a homogeneous, linear Elasticity (physics), elastic material and is useful for providing a Material failure theory, failure criterion for Brittleness, brittle materials, and is a critical technique in the discipline of damage tolerance. The concept can also be applied to materials that exhibit ''small-scale yield (engineering), yielding'' at a crack tip. The magnitude of depends on specimen geometry, the size and location of the crack or notch, and the magnitude and the distribution of loads on the material. It can be written as: :K = \sigma \sqrt \, f(a/W) where f(a/W) is a specimen geometry dependent function of the crack length, , and the specimen width, , and is the applied stress. Lin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continuum Mechanics
Continuum mechanics is a branch of mechanics that deals with the deformation of and transmission of forces through materials modeled as a ''continuous medium'' (also called a ''continuum'') rather than as discrete particles. Continuum mechanics deals with ''deformable bodies'', as opposed to rigid bodies. A continuum model assumes that the substance of the object completely fills the space it occupies. While ignoring the fact that matter is made of atoms, this provides a sufficiently accurate description of matter on length scales much greater than that of inter-atomic distances. The concept of a continuous medium allows for intuitive analysis of bulk matter by using differential equations that describe the behavior of such matter according to physical laws, such as mass conservation, momentum conservation, and energy conservation. Information about the specific material is expressed in constitutive relationships. Continuum mechanics treats the physical properties of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
