A comparative study of target reliability index derivation for reinforced concrete structures governed by serviceability limit state

Abstract

Typical design of reinforced concrete structures is governed by the ultimate limit state (ULS), while serviceability limit state (SLS) is checked. The target reliability index for ULS is recommended based on cost optimization and back calibration of existing practice. Many design cases, such as prestressed concrete, are, however, governed by serviceability conditions and the background for the current recommendations for target reliability index of irreversible SLS as provided by ISO 2394 is unclear. This contribution reviews previously developed generalized framework for determination of SLS target reliability by taking into account a cost ratio and statistical parameters of action‐resistance variable. Target reliability index βt,SLS can be then obtained from the previously introduced table with a minimum effort. A case‐specific approach to the cost optimization with FORM analysis is introduced in order to validate the results of the generic approach. It is found that there is a discrepancy in terms of the obtained value of target reliability index. This can be attributed to the influence of the decision parameter d in the cost optimization process. It affects the probability of failure pf(d) at the different rates for different formulations of SLSs. The nearly linear assumption in the generic formulation may not necessarily apply in other cases, and care should be taken when specifying target reliability index βt,SLS as the effectiveness of the decision parameter must be observed.

A Wiener degradation process with drift‐based approach of determining target reliability index of concrete structures

“…Describe the degradation process of relative dynamic elastic modulus (E s ) using a Wiener process with drift Calculate the drift coefficient μ and the diffusion coefficient Equation (14) shows the relationship between the concrete compressive strength and the degradation amount of relative dynamic elastic modulus. Then, the initial dynamic elastic modulus of C40 concrete is taken as 𝐸 0 = 42.5𝐺𝑝𝑎 and let 𝐸 𝑠 = 𝑥.…”

Effect of decision parameter efficiency on target reliability

“…2 to 5, the efficiency of the decision parameter at increasing safety is dependent on the limit state equations for ULS and SLS. Previous research by Van Nierop et al [7][8][9] investigated target reliability in reinforced concrete (RC) structures where the design is governed by SLS considerations. This work indicated that discrepancies exist between the target reliability derived using the generic cost optimization and that derived from a case-specific cost optimization.…”

“…The optimal reliability is found at the decision parameter value that minimizes the structural cost function. Previous research [7][8][9] has shown that in RC structures governed by SLS design, the efficiency of the decision parameter at increasing safety in the limit state equation also plays a role in the determination of the optimum reliability.…”

Permit checking of overloaded customized transport vehicle based on serviceability limit state reliability of concrete bridges

“…Attributed to the different potential failure consequences, the target reliability index of SLS is obvious lower than that of ULS (Lenner et al, 2019;Roubos et al, 2018). According to the suggestion of ISO, the lifetime target reliability index can be taken as 0 and 1.5 when SLS is reversible and irreversible, respectively (ISO2394, 1998).…”