دانلود رایگان مقاله انگلیسی عملکرد لرزه ای ستون های RC مستطیل مقیاس بزرگ CFRP تحت بارگذاری جانبی - الزویر 2018

Abstract:

Considerable studies have been carried out on the seismic performance of fiber-reinforced polymer (FRP) retrofitted reinforced concrete (RC) columns. However, research on the seismic performance of FRP-retrofitted RC columns under lateral loading in different directions remains limited. This paper presents an experimental investigation on both un-retrofitted and carbon FRP (CFRP) retrofitted rectangular RC columns with an emphasis on the effect of the directions of lateral loading on the seismic performance of the columns. A total of ten large-scale cantilever rectangular RC columns were constructed and five of them were retrofitted with CFRP wraps at the potential plastic hinge regions. The overall performance of each specimen is examined in terms of damage evolution, lateral load-displacement hysteretic behavior, lateral strength, ductility capacity, stiffness degradation, and energy dissipation. The direction of lateral loading is found to have significant influence on the seismic performance of both un-retrofitted and CFRP-retrofitted rectangular RC columns. It is also found that the shear strength of the un-retrofitted and FRP-retrofitted rectangular RC columns in nonprincipal directions can be predicted based on the lateral strength in the principal directions by the ellipse equation.

4. Conclusions

An experimental study was carried out on five un-retrofitted and five FRP-retrofitted rectangular RC columns under combined constant axial compression and reverse lateral loading in different directions. Based on interpretations and discussions of the test results, the following conclusions can be drawn: (1) The loading direction had significant effects on the seismic performance of both un-retrofitted and retrofitted rectangular RC columns. The lateral drift, shear resistance and energy dissipation capacities generally decreased with the increase of lateral loading direction angle. The failure of un-retrofitted control columns generally varied from brittle shear failure mode to ductile flexural failure mode when the lateral load direction varied from the strong axis direction (i.e. 0°) to the weak axis direction (i.e. 90°). All the retrofitted specimens exhibited ductile failure mode despite the variation of lateral loading directions. (2) The seismic performance of rectangular RC columns was obviously improved after being retrofitted with CFRP, despite the variation in the loading direction. However, the efficiency of the CFRP retrofitted strategy decreased with the increase of lateral loading direction angle. (3) The shear strength of both un-retrofitted and FRP-retrofitted rectangular RC columns generally agreed with the ellipse-interaction line. The lateral strength of both un-retrofitted and retrofitted rectangular RC columns in nonprincipal directions can be reasonably predicted based on the lateral strength in the principal directions by the ellipse relationship. (4) Both un-retrofitted and CFRP-retrofitted rectangular RC columns generally exhibited worst ultimate lateral deformation and plastic deformation capacities when the lateral loading was in the 60° direction; the performance was even much worse than that in the weak axis direction (i.e. 90°). The 60° direction was shown to be another weak axis or even the critical weakest axis for both un-retrofitted and retrofitted rectangular RC columns.