دانلود رایگان مقاله تایید دست برای آثار تنزل استحکام خمشی موضوع R.C طبقات موجود

abstract

In the present paper, a simplified model for hand verification of the flexural and shear strength of existing corroded T beams cast in place of lightened R.C. orthotropic slabs forming floors is presented and discussed. Diffused and pitting corrosion on steel bars, compressive concrete strength degradation and concrete bond strength degradation are included in the model. The original contribution of the paper is evaluation of the flexural and shear strength considering both the cases of strain compatibility and absence of compatibility and considering the main parameters governing the corrosion process. An arch-resistant model for the calculus of the flexural and shear strength of the beam was adopted in the absence of strain compatibility, while the plane section theory was adopted for the case of strain compatibility. No punching shear is considered. This approach is simple and can be applied on the basis of the experimental information available (carbonation test, chloride content, measurement of the pitting in the bar, gravimetric method for general corrosion) or by utilizing analytical expressions calibrated on the knowledge of the corrosion current intensity determined by linear polarization resistance measurement (LPR). The model was also verified against experimental results recently obtained by the authors.

9. Conclusions

In the present paper, a simplified analytical model based on arch-resistant mechanism to derive the flexural and the shear strength of corroded T beams cast in place of lightened R.C. slabs forming floors is presented and discussed.Preliminary research on the effects of corrosion on the properties of materials highlights that the main effects due to general corrosion and pitting are: reduction in steel area and ductility; loss of bond strength; concrete compressive strength degradation. The expressions derived for shear strength considered several possible limit states (anchorage failure, concrete crushing of compressed strut) and reduction in the geometrical and mechanical parameters (cross-section area of section, area of steel bar bond and compressive strength). All the expressions derived allow hand calculation and have a clear physical meaning. Finally, comparison with existing experimental data was satisfactory in terms of both strength prevision and failure modes.