Reliability Assessment of Steel Structural Elements in Wind Excited Buildings

Abstract

One of the basic principles of the design of structures is that they must be sufficiently safe and meet the required reliability requirements. In Eurocode NEN-EN 1990 specific minimum reliability index values are defined, which depend on a certain reference period and reliability class. To ensure that the structures meet the reliability requirements, partial factors are applied in the Eurocode. The aim is to steer the design to the minimum reliability requirements in a relatively simple way without a complete reliability assessment. Since such a reliability assessment is much more complex and requires more time and knowledge of the engineer. This research investigates how the reliability of a steel main bearing structure in a wind excited building can be determined, taking into account all uncertainties on both the resistance and load side. A new method is developed in which wind tunnel measurements, wind speed models and a finite element model of the building can be directly linked. This is an improvement on recent studies. With this method it is possible to determine the load effects of the wind in specific elements of the building. This can then be used to determine the reliability of the steel main bearing structure in a wind excited building.

First of all, all probabilistic models concerning the resistance side of the reliability assessment are identified by means of an extensive literature study. In this way all material properties and uncertainties are included in the reliability assessment. In addition, wind speed models, boundary layer wind tunnel pressure measurements and a FEM of the case study building are used. A wind load effect model quantifies the forces that occur in the structure due to the given wind load (based on the wind tunnel research) on the structure. This wind load effect model consists of several deterministic and stochastic parameters as input. All these data and models are linked to each other to determine the peak load effects and associated sampling uncertainties in various elements of the case study building. To further use the wind load effects in the reliability assessment, extreme value theory must be applied to determine the extreme value distributions of these peak load effects. It should be taken into account that the extremes extracted from the data are independent and identically distributed.

To demonstrate that the method works, it is applied to a case study building. This case study building is initially designed in a deterministic Eurocode manner. Next, the reliability of a number of elements of the steel main bearing structure is extensively determined. For this particular case study building, it is evident that the design can be further optimised compared to the Eurocode design. In conclusion, this method shows that the possibilities in the field of a reliability-based design are certainly worthwhile for the further optimisation of a structure. And the use of this new method in which all data and models can be linked makes the application of a reliability-based design a lot more efficient, more accurate and therefore more interesting.