Issue 35

W. Xu et alii, Frattura ed Integrità Strutturale, 35 (2016) 481-491; DOI: 10.3221/IGF-ESIS.35.54 482 reinforced concrete in China and abroad [7] mainly focuses on beam and column, and few concerns joints of corroded reinforced concrete framework. On this account, we made a simulation study on mechanical performance of framework joints without stirrup under statistic load and obtained degeneration rule of bearing capacity of reinforced concrete framework under the influence of different corrosion rate of steel reinforcement which can help guiding repair and reinforcement of old framework joints. F INITE ELEMENT MODEL AND ANALYSIS METHOD Concrete Constitutive and Corroded Steel Reinforcement Relationship nilateral compressive stress-strain relationship reflects mechanical property of concrete under stress [8]. Its expression is as follows: (1 ) c c d E     (1) If disturbance effect in coal yielding is considered, introduce disturbance factor d into the formula, then the formula change to: 2 1 , 1 1 1 , 1 ( 1) c n c c c n x n x d x x x                  (2) , , c r c c c r f E    (3) , , , c c r c c r c r E n E f     (4) , c r x    (5) , c r f (N/mm 2 ) 25 30 35 40 45 50 , c r  (10 -6 ) 1560 1640 1720 1790 1850 1920 c  1.06 1.36 1.65 1.94 2.21 2.48 cu  / , c r  2.6 2.3 2.1 2.0 1.9 1.9 , c r f (N/mm 2 ) 55 60 65 70 75 80 , c r  (10-6) 1980 2030 2080 2130 2190 2240 c  2.74 3.00 3.25 3.50 3.75 3.99 cu  / , c r  1.8 1.8 1.7 1.7 1.7 1.6 Note: cu  refers to the compressive strain of concrete when the stress in descending branch of stress-strain curve is equal to 0.5 , c r f . Table 1: Reference values of parameters relating to concrete single-axial compressive stress - strain curve. In the formula, c  refers to parameter value of descending branch of single-axial compressive stress - strain curve of concrete (refer to Table 1); , c r f refers to representative value of axial compressive strength of concrete, and its concrete value is determined based on actual structural analysis; , c r  refers to peak compressive strain of concrete corresponding to U