PSI - Issue 64

André Weber et al. / Procedia Structural Integrity 64 (2024) 74–80 André Weber/ Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 2: creep rupture resistance chart of rebars under high loads in wet concrete for different temperatures

2.1. State of the art design regarding live loads and dead loads Design is commonly based on characteristic or guaranteed short term strength and several factors for indoor and outdoor applications as well as a factor for the failure mode. Only at the serviceability design the creep rupture check is performed. For this check in ACI as well as CSA the maximum load, neglecting the variable loads as well as the load safety factors, is taken into account. It should be discussed in which applications and for which products this approach gives enough safety. As a general factor for all products and applications is used and no specific values for the products used there is an additional unknown safety margin. 2.2. Safety Concept from abZ and FprEN1992-1 All loads and safety factors are included in the test load. Test loads are high. All specimens are tested till failure occurrence, No residual strength testing is needed. Extrapolation as well as time-temperature shifting is possible. Variable factors can be taken into account as in fib bulletin 40 shown. The approach is conservative. Some researchers as well as manufacturers criticize this approach as over conservative and uneconomic. But this design procedure is simple and safe. Even values from other testing and safety systems can be taken into account.

Figure 3: Safe and simple safety concept including all loads and safety factors