Issue 35

W. Xu et alii, Frattura ed Integrità Strutturale, 35 (2016) 481-491; DOI: 10.3221/IGF-ESIS.35.54 486 0 2 2 ( 1) R        (8) When corrosion occurs, corrosion product first fills the space between non-corrosive steel reinforcement and concrete. Then corrosion quantity increases and volume becomes larger, resulting in extrusion on concrete around steel reinforcement [12, 13]. Model of exerting radial displacement on concrete around steel reinforcement is shown in Figure 6. The model exerts displacement load on concrete around steel reinforcement at frame joints by such kind of loading means. Figure 6 : Radial displacement loading model. A NALYSIS OF RESULTS Stress Analysis ephogram of concrete stress (kg/cm 2 ) under different corrosion rate when axial compression ratio is 0.2 is shown in Figure 7. It can be seen from Figure 7(a) that, stress at the intersection of concrete beam column is the maximum when corrosion rate is 0; and at that moment, cracks appear and extend to the core area of joints, leading to shear failure; upper part of left beam and lower part of right beam in the core area of concrete joints shoulders larger stress under the influence from antisymmetric monotonic load. Figure 7(b) demonstrates that, middle part of beam shoulders the maximum stress when corrosion rate is 2%. That is because concrete holes around steel reinforcement shoulders radial displacement load from middle part of left beam to middle part of right beam. Figure 7(c) suggests that, changes of stress on concrete beam when corrosion rate is 5% is basically the same with that when corrosion rate is 2%, but the stress is unevenly distributed. That is because that, joints can still shoulder radial displacement load though protective layer of concrete beam has cracked; stress on concrete column at the moment is much higher than that when corrosion rate is 2%; concrete column shows no obvious stress changes due to the large stress on beam. Figure 7(d) shows the maximum stress on concrete joints when corrosion rate is 10% is smaller than that when corrosion rate is 5%; maximum stress on concrete reaches its peak when corrosion rate is 5% and moreover, stress on concrete column changes sharply (column end shoulders large stress and stress in core area of joints is larger than beam end). We can know from figure 7(e) that, the stress nephogram of concrete joints changes slightly when corrosion rate is 15%; and maximum stress on concrete is approximately equal to that when corrosion rate is 10%. Effect of Changes of Corrosion Rate on Bearing Capacity To discuss over effect of changes of corrosion rate of steel reinforcement on bearing capacity of component under fixed axial compression ratio, we divide fifteen stimulation analysis results into three groups according to axial compression ratio. Figure 8 ~10 give load-displacement curves of different test specimen. N