1 Influence of Fracture and Delayed Effects on Steel-Concrete Composite Structures 3 Table 1.1 (a) Characteristic of the profile HEM 700. (b) Characteristics of the concrete in B1/B2 phases (a) Mechanical characteristic of steel HEM700 A= 383 cm2 h= 716 mm b= 304 mm tf = 40 mm tw = 21 mm y cdg= 358 mm Avz = 169,8 cm2 ly = 329278 cm4 Wel,y = 9198 cm3 Mel = 2299 kN.m fyk = 275 MPa Ea = 210000 MPa (b) Characteristic of concrete Concrete B1 Concrete B2 Resistance class C50/60 Resistance class C25/30 Class of cement ClassN Class of cement ClassN AcB1= 184000 mm2 Ac B2= 576000 mm2 uB1 = 2060 mm uB2= 5280 mm ts B1= 1 jour ts B2= 1 jour fck B1= 50 MPa fck B2= 25 MPa fctm B1 = 4,1 MPa fctm B2= 2,6 MPa Ecm B1= 37000 MPa Ecm B2= 31000 MPa Table 1.2 Preflex beam manufacturing steps Stapes Tasks Days 1 Profile preflexion 0 2 Consideration of delay effects of concrete B1 29 3 Relaxation of the preflexion loads 30 4 Consideration of delay effects of concrete B2 59 5 Loading 60 6 Consideration of delay effects at 100 years 36,500 • Step 1. First, we list the lower and upper fiber stresses in concrete B1 at 100 years. • Step 2. It is then checked whether these values exceed the admissible stress. • Step 3. If this is the case, we are looking for the date on which concrete B1 is completely cracked. If this is not the case, we go directly to step 6. • Step 4. Two load cases are created: one before cracking and one after the removal of concrete B1 by adding its own weight. • Step 5. We relaunch the calculations and we list the stresses suffered by concrete B2 at 100 years because removing concrete B1 increases the stresses in the profile and in concrete B2. • Step 6. We check that concrete B2 does not reach its admissible limit, and we proceed the same way as for B1 if this is the case. Finally, we list the maximum stress in the steel profile and check that it remains acceptable.
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