Papers by Keyword: Neutral Axis

Abstract: With high resolution, electronic speckle pattern interferometry (ESPI) technique can be useful in measuring full-filed deformation of laboratory specimens. In this study, ESPI was applied to measure the full-field displacements of mortar beam subjected to three-point bend. Load-displacement curves measured by ESPI were compared to that measured by clip gauge and LVDTs. Satisfactory agreement was observed in all the comparisons, demonstrating the effectiveness and accuracy of ESPI measurement. Furthermore, load versus crack tip opening displacement curve was obtained from ESPI results. Finally, extent of the fracture process zone and neutral axis of the mortar beam were analyzed based on full-filed displacement contour measured by ESPI.

Abstract: The compressive height of reinforced concrete flexural members in service stage is generally obtained by equations based on the concept, moment-of-area of conversion area with respect to the neutral axis in tension zones equaling to that in compression zones. In this paper a specific calculation method of compressive height for singly or doubly reinforced rectangular and T-shaped cross sections is proposed.

Abstract: The equation to determine the neutral axis of concrete filled steel tube(CFST) component with round section is presented in this paper. The geometric equation, physical equation and static equilibrium equation of CFST are analyzed to determine its section neutral axis. The compressed mechanical properties of CFST component are analyzed with the concrete material properties divided into tension and compression parts.Comparing the numerical results with the experimental results it can be verified that the equation to determine the neutral axis of CFST component with round section is useful to solve the problems that the tension and compression material properties of concrete are different.

Abstract: In order to study the bearing capacity and section stress-strain distribute on the steel tube filled with steel-reinforced concrete (STSRC) compression-flexure column, four compression-flexure members of STSRC were tested and theoretical researched. The major parameters of the test were axial compression ratio (n=0.5~0.85). The result of the study showed that: load-deformation() typical curve includes three stages, elastic characteristic, elastic-plastic characteristic, and disruption; Along with the increase of axial compression ratio, the bearing capacity and ductility reduced, but the peak displacement had not change enough; The composite column conformed to plane section, and the larger the axial compression ratio, the further distance of neutral axis of section to the centric axis and closer to the tensile region. ; During the loading process, the steel skeleton in compressive zone yield, but in tensile region never yielded. According to the test results and the limit equilibrium method, the formula for calculating the compression-flexure member of STSRC was established. A good agreement between the calculation results and testing results illustrates, which is feasible to using the calculating formula to calculate the bearing capacity of STSRC.

Abstract: We have already considered the problem of joint work of structure, foundation slab and basis in [1, 2] (two-layer beam or slab on elastic basis). The distinctive paper is devoted to analysis of two-layer beam-strip on elastic basis, which corresponds to the problem of the plane deformed state. Nonlinear dependence of internal forces on structure height is presented.

Abstract: The stress distribution on the midsection of a pure bending beam where tensile strain localization band initiates on the tensile side of the beam and propagates within the beam is analyzed. Using the static equilibrium condition on the section of the midspan of the beam and the assumption of plane section as well as the linear softening constitutive relation beyond the tensile strength, the expressions for the length of tensile strain localization band and the distance from the tip of the band to the neutral axis are derived. After superimposing a linear unloading stress distribution over the initial stress distribution, the residual stress distribution on the midsection of the beam is investigated. In the process of strain localization band’s propagation, strain-softening behavior of the band occurs and neutral axis will shift. When the unloading moment is lower, the length of tensile strain localization band remains a constant since the stress on the base side of the beam is tensile stress. While, for larger unloading moment, with an increase of unloading moment, the length of tensile strain localization band decreases and the distance from the initial neutral axis to the unloading neutral axis increases. The neutral axis of midsection of the beam will shift in the unloading process. The present analysis is applicable to some metal materials and many quasi-brittle geomaterials (rocks and concrete, etc) in which tensile strength is lower than compressive strength. The present investigation is limited to the case of no real crack. Moreover, the present investigation is limited to the case that the length of strain localization band before unloading is less than half of depth of the beam. Otherwise, the residual tensile stress above the elastic neutral axis will be greater than the tensile strength, leading to the further development of tensile strain localization band in the unloading process.