| Under shear failure,reinforced concrete structure were destroyed with poor ductility and energy dissipation.There is still no unified understanding of the shear stress mechanism and destruction characteristics.The horizontal earthquake is resisted through columns within reinforced concrete frame structure.The shear stress of bottom frame columns are important structural seismic design parameters.Therefore,the shear stress monitoring is of great significance to explore the shear failure mechanism and to determine the input of seismic action accurately.At present,there is a lack of direct and reliable shear stress monitoring method.The smart aggregate with shear mode piezoelectric ceramics can be used for concrete shear stress monitoring,but its calibration method is not yet mature,and its monitoring error has not been determined,hindering its application.Therefore,the concrete shear stress monitoring method based on smart aggregate was proposed.The main research work are as follows:Firstly,A shear stress field design method for the smart aggregate calibration was proposed.The midpoint between the loading plate and supports of the three-point loading concrete deep beam was using as calibration area.With ABAQUS numerical simulation,the effect of the specimen size and the monitoring area size on the uniformity of shear stress field was analyzed.To maintain concrete linear elasticity and generate larger shear stress,the reinforcement was designed.The optimized design of the deep beam was 450 mm × 900 mm × 2000 mm,and the size of the monitoring area was 100 mm × 100 mm.The sensitivity of the shear stress smart aggregate was determined to be 3.63 × 103 pC/MPa through the loading test.Secondly,the influence of material nonlinearity on the shear stress contour and monitoring accuracy was studied.Considering the influence factors of typical axial compression ratio,reinforcement ratio and crack width,a two-dimensional reinforced concrete compression-bending member ABAQUS finite element model was established to determine the sectional shear stress contour under push-over analysis.And the shear force was obtained through discrete stress contour integration.Studies had shown that the axial compression ratio,cracks and non-linear level of components significantly affect the shear stress contour of,while the reinforcement ratio had a small effect.Shear stress monitoring near the reverse bending point should be selected to ensure that the monitoring error does not exceed 5%.Finally,the feasibility of smart aggregate shear stress monitoring was verified by horizontal cyclic loading test of the bending member.The shear stress smart aggregate was used to monitor the plastic hinge area of the reinforced concrete column under horizontal cyclic loading.Its numerical model was established to verify the monitoring results.Studies had shown that under a small level of non-linearity,the monitoring error does not exceed 30%,which basically verified the effectiveness of the results of the proposed monitoring method. |
