ABSTRACT
The structural performance of concrete columns with multispiral reinforcement (MSR) developed in Taiwan is significantly superior to conventionally reinforced columns. The increased strength and ductility stem from the passive confinement produced by the partially overlapping spirals which cover almost the entire cross-section. Because of the complex structural behavior and insufficient experimental data, which are limited to monotonic axial compression or cyclic lateral drift with increasing magnitude under constant compression, and due to the novelty of this reinforcement layout, the MSR is not recognized in the design codes. To utilize its full potential, the carrying capacity can be determined computationally for arbitrary loading history via the nonlinear finite element method and the design strength can be obtained by employing the global safety factor approach. The interaction diagram (ID) is a strength envelope surrounding all admissible states of the internal forces and is perfect for assessing the safety and efficiency of the structural design of columns. The ID can be constructed by processing repeatedly run simulations with different loading combinations. This approach is computationally demanding, but the analyses can be defined automatically, run in parallel, and the results for different combinations of material properties and reinforcement layout can be precomputed and stored in a database.
One of the objectives of the current bilateral Czech-Taiwanese project is to develop this approach for the columns with MSR. In summer 2021, within the scope of the present project, the Taiwanese laboratories MOST tested 5 geometrically identical specimens with MSR subject to compression with different values of eccentricity. The aim of this conference contribution is to compare the global behavior of these specimens expressed in the M-N diagram with the blind prediction using FEM and to construct the corresponding ID. In the simulations, concrete is described with CDPM2, the second generation of the well-known Concrete Damage Plastic Model originally proposed by Grassl and Jirásek.
