Keywords: double-layer grids, performance-based design, reliability, uncertainty, incremental dynamic analysis, confidence level.

There are various types of space structures, differing in their behavior under load and requiring different methods of analysis [1]. Double-layer grids are typical examples of prefabricated space structures and also one of the most popular forms of space frames. Nowadays, they are frequently used all over the world for covering large-span industrial buildings, exhibition centers, stadiums, auditoriums and hangars.

Recently, the concept of performance-based design (PBD) has become popular for many types of structures subjected to seismic loading. Structural performance in recent earthquakes has revealed the weakness of current design codes and has shown the need for new concepts and methods for performance evaluation and design. However, in earthquake engineering, precisely modeling the true behavior of a structural system under the action of future seismic excitations for design purposes is very difficult. This is mainly due to the uncertain nature of the expected earthquake ground motions on a site, assumptions made in structural analysis and lack of knowledge in structural behavior modeling. A reliability-based framework for analysis and design is most suitable in the evaluation and design process.

In structural performance evaluation the most important limit state is collapse. Here, the dynamic behavior of the structures near collapse is complicatedly nonlinear so that the capacity against collapse is very complex and highly dependent on the excitation. The incremental dynamic analysis (IDA) has been used to determine the capacity against incipient collapse of frame structural systems [2].

In this paper, the IDA method is applied to evaluate and quantify the seismic performance of double-layer grids within a probabilistic-based framework. The basic procedure consists of the evaluation of demand and capacity of structural responses for the desired performance level. Then, the ratio of demand to capacity is calculated with the uncertainty factors. This ratio is used to evaluate the confidence level of the probability that the structure would experience it in its worst state performance level. The results show that these structures satisfy the selected performance objective, even under large ground motions.

1

Z.S. Makowski, "Analysis, Design and Construction of Double-layer Grids", London, Applied Science, 1981.

2

D. Vamvatsikos, C.A. Cornell, "Incremental Dynamic Analysis", Earthquake Engineering and Structural Dynamics, 31(3), 491-514, 2002. doi:10.1193/1.1737737

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