PSI - Issue 64

André Weber et al. / Procedia Structural Integrity 64 (2024) 1959–1966 A. Weber/ Structural Integrity Procedia 00 (2019) 000 – 000

1964

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3.3. Conservative Combination in Annex R of EC2 It seems clear, that both tests test concept in paragraph 3.1. and 3.2 do not deliver comparable results. While the first concept delivers a fulfilment statement for a small strain, the second concept delivers a performance based resistance. But this resistance includes the load safety as well as the material safety factors together. Only with both factors a safe design value can concluded from the failure points and the endurance times till failure only. For Annex R of FprEN1991-1 2023 a transition between both concepts is tried. The characteristic value of the long term strength in wet concrete can be estimated from the following tests. • Durability test without load to represent and quantify the effect of the alkaline environment including residual strength testing • Creep rupture tests in air • Temperature factor for the use in exterior structures with rated long term temperatures up to 40°C and temporary temperatures up to 70°C Each of the test is defined by a residual strength or reduction factor compared to the virgin strength of the material. The multiplication of the three factors is a reduction factor taking account for the three different actions described above, which are seen as the most important actions on the reinforcement. It seems that there might be some doubts if the combination of these three actions in three different tests leads to the same result as if the combination is made in a single test. On the other hand the combination of the minimum values of all three tests seems to lead to uneconomical values. 3.4. Advanced Combined Concept The combined concept is based on long term test with higher load and residual strength tests. The concept is furthermore based on partial safety factors and the known creep rupture curves. Since the transition from the global safety factor to partial safety factors, the material safety factor shall be applied on the resistance side. And the load factor on the load side.