مقاله انگلیسی رایگان در مورد استحکام خمشی الاستیک ستون کامپوزیت های بتن فولادی – الزویر 2018

Building structures are typically designed with the expectation that they will experience inelasticity during their design life. Different forms of inelastic behavior will occur at different levels of loading. In steelconcrete composite members, concrete cracking may occur under relatively low loads, slip may occur at moderate loads, and steel yielding and concrete crushing may occur relatively high loads. Despite the increasing use of inelastic analysis, which can track this behavior explicitly, elastic analysis remains prevalent in design. Thus, the expected inelasticity must be accounted for implicitly in the elastic analysis. One way of accomplishing this is through appropriate modifications of the geometric and material properties assumed in the analysis. In elastic analyses with frame elements, the behavior of cross sections is represented by elastic rigidities which define the stiffness of cross sections in various modes of deformation, for example the axial stiffness, EA, the flexural stiffness, EI, the shear stiffness, GA, and the torsional stiffness, GJ. For moment frame systems, the dominant mode of deformation is typically bending, thus EI is of prime importance. Elastic analyses are used for many different purposes in the design of building structures, and the appropriate elastic geometric and material section properties may differ depending on the purpose of the analysis. For strength design, appropriate elastic section properties typically reflect the level of inelasticity at the “ultimate” limit state. Alternatively, when computing deflections due to wind loading for story drift checks, appropriate elastic section properties typically reflect the level of inelasticity at a “service loading” level. The elastic section properties used for service loading level design checks are often greater than those for the determination of required strengths. For example, in the ACI Code, the moment of inertia is permitted to be increased by a factor of 1.4 for service load analysis [2] and in the AISC Specification, the stiffness reductions associated with the direct analysis method are not intended for determining deflections [3]. While a variety of potential uses for elastic flexural rigidity exist, they are not all equally common in practice. All structures are evaluated for strength which typically includes using an elastic flexural rigidity within design equations to determine the compressive strength of columns and within a second-order analysis to determine required strengths. The appropriate effective flexural rigidity for these uses was the subject of recent research and changes to code provisions [3,8].