Issue 46

H. Zhu et alii, Frattura ed Integrità Strutturale, 46 (2018) 361-370; DOI: 10.3221/IGF-ESIS.46.33 364 Materials Compressed rebar Tension rebar Stirrup Specification HRB4002  10 HRB4002  14 HPB300  8 Elasticity modulus s E ( 5 2 10 / N mm  ) 2.00 2.00 2.20 The design value of tensile strength 2 ( / ) y f N mm 360 360 280 The design value of compressive strength ' 2 ( / ) y f N mm 360 360 280 Table 1 : The parameters of rebars. CFRP plate and binding material CFRP plate and binding material were regarded as a whole and simulated using SOLID45 element. The ultimate tensile strength of CFRP plate fu f was 2860 N/mm 2 , elasticity modulus cf E was 1.47 ×10 5 N/mm 2 , and Poisson's ratio was 0.3. The Poisson's ratio and elasticity modulus of binding material was 0.25 and 3500 N/mm 2 respectively. Cushion block To prevent stress concentration induced local damage, rigid cushion blocks were used at the support and loading points. It was simulated using SOLID45 element. The Poisson's ratio and elasticity modulus of cushion block was 0.3 and 2.0 × 10 5 N/mm 2 . Modeling and solution process Mapping meshing was used. The position of node generation should ensure the sharing nodes of different materials were at the same position after connection. Taking the position of rebars and the size of groove as an example, concrete, resin and cushion blocks were divided into hexahedral element. Nodes were established in the space firstly. Then rebars generated via the nodes. Plane net was established on the plane which the top of the beam and cushion blocks lie; after stretching, concrete and cushion blocks were established, and the position of groove should be left. After merging of the nodes, CFRP element was established at the pre-aside position for groove. Then mid-span symmetry was performed to simulate the whole beam. Displacement control was used in the simulation process, and the maximum displacement value was 0.05 m. After modeling, data were analyzed using finite element solver via Static. The calculation results were extracted using POST1. Design of component The size of the component was 150 mm * 300 mm * 2300 mm. The calculated net span of the beam was 2100 mm. The size of tension rebar of the test beam and erection rebar was 2  25 (A s =980 mm 2 ) and 2  6.5 (A s =65 mm 2 ) respectively. Unilateral stirrup reinforcement was used, and the reinforcement zone was  6.5@50, and the non- reinforcement zone was  6.5@200. The thickness of the protective layer at the lower layer of the concrete beam was 30 mm, and the protective layer at the upper layer was 20 mm. F INITE ELEMENT ANALYSIS RESULTS Analysis of concrete failure he failure process of the strengthening beam was as follows. In the initial stage, the tension on the beam is shared by rebars, concrete and CFRP plate. With the increase of load, concrete in the tension zone fractured. In the middle stage, the stress on the rebars and CFRP plate became layer, and the tension mainly relied on rebars and CFRP plate. With the increase of the load, the rebars reached the yield stress. In the late stage, the strain on the CFRP T