Abstract
Some of the early probabilistic code calibrations minimized an error term defined as difference between the optimal or target design and the design resulting with the trial partial factors and the code format. In contrast to these design-based calibrations, in recent years, the error was defined in terms of a reliability deviation. Aiming at minimizing societal costs, reliability-based calibrations probably provide more accurate results than design-based code calibrations, however at the cost of a significantly lower computational efficiency.The long duration of reliability-based code calibrations impedes repeated code calibrations, which are needed in the development of a code format or for a more profound understanding of it. This paper compares the reliability-based with the design-based code calibration procedure theoretically and by using an example. The results showed that the design-based code calibration is efficient for the development of a code format. However, the differences between both calibration procedures regarding the calibrated partial factors are significant. As the reliability-based calibration has a more solid theoretical background, it is preferred for the final calibration of the code format.
Highlights
Both calibration procedures are equivalent concerning the code format development, but the design-based code calibration is the pre ferred procedure, as the time consuming reliability analysis is de coupled from the partial factor optimization and it runs within a few seconds after the target designs are precalculated, compared to many minutes in a reliability-based calibration
In contrast to the predominantly used reliability-based code cali bration, the advantage of the design-based code calibration is that in the iterative optimization of the partial factors no computationally costly reliability analyses need to be done and a calibration can be performed within seconds
This was achieved by forcing a large reliability scatter among the reference structures by including structures of four different materials under three different live loads
Summary
The fact that structural codes are not constantly under discussion is the consequence of an appropriate calibration of them. The calibration defines the compromise between the maximization of safety and the minimization of construction costs while keeping the code format simple to avoid unnecessary complexity and errors in its application. Four different complexity levels for code calibration targets and design verification can be distinguished, following [25,1]. Level 4 provides the balancing between safety and construction costs by minimizing the total expected costs of a building Simplified, the total costs consist of the construction costs and the costs associated with a failure and its probability (i.e. the risk). With in creasing safety level, the probability of failure of a structure and the risk reduces roughly inversely proportional, while the con.
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