Failure Flexural

Profile Support span (in.) Type of the load Deflection at failure (in.) Ratio between 4-pt and 3-pt load deflection at failure Flexural modulus (psi)... 

The tensile strength at -320 F of the most amorphous Kel-F material we could make was approximately 26,000 psi, while that of the most crystalline was approximately 15,000 psi. The more amorphous samples had a measurable elongation (-+5 ) at -320 F, whereas the crystalline samples showed a typical brittle failure. Flexural, torsional, compressive and impact results also show a definite change in properties with a change in crystallinity. 

Abstract To ensure better performance for a range of existing reinforced concrete structures in seismic regions with substandard structural details, seismic retrofit is an economical solution. Hence, this chapter presents some of the available results in which fiber-reinforced polymer (FRP) composites can be used for damage-controllable structures. For example, the performance of existing reinforced concrete structures whose components are vulnerable to shear failure, flexural-compression failure, joint reinforcement bond failure, or longitudinal reinforcement lap splice failure and retrofitted with FRPs is described. Novel concepts of modern constructions with controllability and recoverability using FRP composites are addressed. 

Flexural strength (MPa) Modulus of elasticity (GPa) Strain at failure (%) Flexural strength (MPa) Modulus of elasticity (GPa) Strain at failure (%)... 

Flexural stress SiC mpture curves are shown in Figure 3 (27). AU. the forms tend to be fairly resistant to time-dependent failure by elevated temperature creep. In addition, SiC shows outstanding resistance to oxidation even at 1200°C as a result of formation of a protective high purity siUca surface layer (28). 

Brick wall panel 8 or 12 inch thick (not reinforced) Shearing, flexure failure 0.55 7-8... 

Brick wall panel, 8 or 12 inches thick (not reinforced). Shearing and flexure failures. 7.0-8.0... 

Even plastics with fairly linear stress-strain curves to failure, for example short-fiber reinforced TSs (RPs), usually display moduli of rupture values that are higher than the tensile strength obtained in uniaxial tests wood behaves much the same. Qualitatively, this can be explained from statistically considering flaws and fractures and the fracture energy available in flexural samples under a constant rate of deflection as compared to tensile samples under the same load conditions. These differences become less as the... 

Although the creep behavior of a material could be measured in any mode, such experiments are most often run in tension or flexure. In the first, a test specimen is subjected to a constant tensile load and its elongation is measured as a function of time. After a sufficiently long period of time, the specimen will fracture that is a phenomenon called tensile creep failure. In general, the higher the applied tensile stress, the shorter the time and the greater the total strain to specimen failure. Furthermore, as the stress level decreases, the fracture mode changes from ductile to brittle. With flexural, a test specimen... 

Strength can be measured in compression, in tension, in shear and transversely (flexural strength). However, if we exclude plastic flow as a means of failure, then materials can only fracture in one of two ways (1) by the pulling apart of planes of atoms, i.e. tensile failure, or (2) by the slippage of planes of atoms, i.e. shear failure. Strength is essentially a measure of fracture stress, which is the point of catastrophic and imcontrolled failure because the initiation of a crack takes place at excessive stress values. 

Reinforced concrete is a complex material to model due to the brittle nature of concrete and non-homogenous properties. Although sophisticated methods are available to model crack propagation and other responses, simplified methods are normally used in blast design of facilities. These methods are based on a flexural response and rely on elimination of brittle modes of failure. To achieve a ductile response for concrete, proper proportioning and detailing of the reinforcing is necessary. 

DIF values vary for different stress types in both concrete and steel for several reasons. Flexural response is ductile and DIF values are permitted which reflect actual strain rates. Shear stresses in concrete produce brittle failures and thus require a degree of conservatism to be applied to the selection of a DIF. Additionally, test data for dynamic shear response of concrete materials is not as well established as compressive strength. Strain rates for tension and compression in steel and concrete members are lower than for flexure and thus DIF values are necessarily lower. 

The failure mechanisms of interest in reinforced masonry wall elements include flexural, transverse shear, in-plane shear and in some cases, combined axial compression and flexure. Buckling failure modes of compression elements and connection failures are to be avoided. 

The primary failure mechanisms encountered in reinforced concrete buildings arc flexure, diagonal tension, and direct shear. Of these three mechanisms,. flexure is preferred under blast loading because an extended plastic response is provider prior to failure. To assure a ductile response, sections are designed so that the flexural capacity is less than the capacity of non-ductile mechanisms. 

Ductility limits for structural steel members are established such that gross member collapse due to failure of the member itself or its connections is precluded. It is presumed that local and gross member instabilities are prevented by providing adequate bracing and stiffeners. Shear failure modes are also to be precluded by design. Determination of failure mechanisms and corresponding capacities for flexural members and beam-columns arc adequately covered by the LRFD specifications. 

Strengthening of the connections is often the most cost effective upgrade for existing buildings if it does not require removal of existing interior walls and equipment. For a member to absorb blast energy and be structurally efficient, it must develop its full plastic flexural capacity. This requires a substantial increase in shear capacity at the connections to avoid failure. 

Birger, S., Moshonov, A. and Kenig, S. (1989). Failure mechanisms of graphite fabric epoxy composites subjected to flexural loading. Composites 20, 136-144. 

Davidovitz, M, Mittelman. A., Roman. I. and Marom. G. (1984). Failure modes and fracture mechanisms in flexure of Kevlar-epoxy composites. J. Mater. Sci. 19, 311-294. 

Shih, G.C. and Ebert, L.J. (1986). Interface strength effects on the compressive-flexure/shear failure mode transition of composites subjected to four-point bending. J. Mater. Sci. 21, 3957-3%5. 

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