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Thermal/structural response models

Thermal/structural response models are related to field models in that they numerically solve the conservation of energy equation, though only in solid elements. Finite difference and finite element schemes are most often employed. A solid region is divided into elements in much the same way that the field models divide a compartment into regions. Several types of surface boundary conditions are available adiabatic, convection/radiation, constant flux, or constant temperature. Many ofthese models allow for temperature and spatially dependent material properties. [Pg.418]

The structural fire endurance of a structural system is a measure of its ability to resist collapse during exposure to a fire. The thermal/structural response models evaluate the time-temperature history within a solid exposed to a fire environment. The time-temperature history, or design fire exposure, can be a... [Pg.418]

The above problems of fabrication and performance present a challenging task of identification of the governing material mechanisms. Use of nonlinear finite element analysis enables close simulation of actual thermal and mechanical loading conditions when combined with measurable geometrical and material parameters. As we continue to investigate real phenomena, we need to incorporate non-linearities in behavior into carefully refined models in order to achieve useful descriptions of structural responses. [Pg.130]

When exposed to high temperatures and fire, FRP composites experience complex changes in material states involving the interaction of thermal, chemical, physical, mechanical, and structural phenomena. Modeling and predicting aU the coupled responses of FRP stmctures is therefore a complex task. By treating independently only one or two of these phenomena in each model, however, the task becomes more reasonable. The thermal phenomena (heat transfer, temperature distribution, etc.) are mainly determined by the thermophysical properties of the material and the thermal boundary conditions, while the mechanical and stmctural phenomena... [Pg.109]

A one-dimensional thermal response model was developed to predict the temperature of FRP structural members subjected to fire. Complex boundary conditions can be considered in this model, including prescribed temperature or heat flow, as well as heat convection and/or radiation. The progressive changes of thermophysical properties including decomposition degree, density, thermal conductivity, and specific heat capacity can be obtained in space and time domains using this model. Complex processes such as endothermic decomposition, mass loss, and delatnina-tion effects can be described on the basis of an effective material properties over the whole fire duration. [Pg.131]

The time-to-failure of a structure or its components is an important issue for structural safety considerations in fire. On the basis of the strength degradation models for FRP materials under elevated and high temperatures developed in Chapter 5, the time-to-failure is predicted for GFRP tubes and laminates under both thermal and mechanical loading in compression. Temperature responses were again calculated using the thermal response model presented in Chapter 6. [Pg.134]

Based on this understanding, a mechanism based constitutive model incorporating the nonlinear structural relaxation model into the continuum finite-deformation thermoviscoelastic framework was developed as follows. The aim of this effort was to estabUsh a quantitative understanding of the shape memory behavior of the thermally responsive thermoset SMP programmed at temperamres below Tg. To simplify the formulation, several basic assumptions were made in this study ... [Pg.124]

Each of these steps depends on the process before. The software suite starts with the material selection, in which also an individual material can be dehned. Fiber orientations and the number of plies can be selected in a following step. All material parameters must be chosen before the analysis can start. Six structural analysis modules can be differentiated with the CDS software suite. These solid mechanic modules are thick-walled cylinder, thin plate, thin plate impact-fastener modeling, thick plate, discontinuous tile modeling and compliant beam interlayer analysis. The CDS software suite allows changing the parameters of the manufacturing process or the laminate structure in real time. Four result sections for those parameter changes are provided by the software the effective properties, thermal-processing response, stress-strain results and the failure response. The CDS software suite is a complete analysis tool kit which is easy to use for the client. The software also allows export into an external simulation tool. [Pg.201]

A three-dimensional model extending 180° of the reactor vessel support is employed to study the thermal and structural responses of the assembly for various thermal transients (Figure 12.9). The three-dimensional model... [Pg.148]

More complex analyses can be carried out using finite elements analysis. Some authors developed a two-dimensional finite element model to analyze the behavior of masonry structures subjected to fire on one side [20]. This model would serve to give a response to thermal structural walls that almost were not loaded but could not model the walls under high loads due to the difficulty of simulating the effects of bonding and material degradation under these conditions. [Pg.441]

Figure 10-6 Primary Support Structure and RCS Thermal Expansion Comparison 10.2.4.2 Dynamics and Thermal Response Model... Figure 10-6 Primary Support Structure and RCS Thermal Expansion Comparison 10.2.4.2 Dynamics and Thermal Response Model...
The reader may gain better appreciation of the many basic differences responsible for the division into different classes of heteronin by comparing certain representative members, directly or through appropriate models, in terms of the information presented in Table II. First, one notes that the classification of oxonin (24a) as atropic, jV-methylazonine (27a) as nondescript, and 1 //-azonine or its anion as diatropic, originally proposed on the basis of NMR chemical shifts (data shown in first three rows), was confirmed by the determination of solvent shift character (S values)38 39 that revealed 1//-azonine to possess significant diatropic influence (comparable to that of naphthalene +1.3538), the V-methyl counterpart to exhibit a far weaker effect in the same direction, and oxonin to be atropic or mildly paratropic under this criterion, its S value being closely similar to that of the family s 8 --electron polyenic model, all-cis-cyclononatetraene (24 X = CH2). Major differences between oxonin and parent azonine are also seen to exist in terms of thermal stability and 13C NMR and UV spectroscopy, all of which serve further to emphasize the close structural similarity of oxonin with n-... [Pg.68]


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See also in sourсe #XX -- [ Pg.418 , Pg.419 ]




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