A new method for assessing tortional effects in irregular buildings

Abstract eng:
Many researchers have dealt with the concept of torsion in reinforced concrete buildings, since many buildings have been damaged due to the eccentric arrangement of the vertical resisting elements in the floor plan. Although in many articles design and/or evaluation criteria have been proposed [1-3], there is not a commonly accepted one, able to manage the effects of torsion in the elastic and the inelastic range of response. In this work, it is investigated the common problem in all buildings that depicts torsional phenomena and to formulate this in a mathematical expression so as to have a useful tool in evaluating and designing structures against torsion. It is proposed the so called ratio of torsion (rot) that can be used for evaluating the behaviour of structural systems. The results proved that structures with low values of rot develop low values of base torque and so better BST curves [3]. Test examples are considered: (i) a symmetrical structure with respect to the stiffness’s and the strength. (ii) a structure with symmetrical distribution of strengths but with stiffness eccentricity and (iii) a symmetrical structure with reference to the stiffness’s but with strength eccentricity. The results showed clearly that designs with lower values of rot bring better shape of the corresponding BST curves. Furthermore, it was found that there is a linear correlation between base torque and the ratio of torsion. References [1] Wai K. Tso, Static Eccentricity Concept for Torsional Moment Estimations. Journal of Structural Engineering, 116, 1199-1212, 1990 [2] Nikolaos D. Lagaros, Manolis Papadrakakis and Nikolaos Βakas, Automatic Minimization of the Rigidity Eccentricity of 3D Reinforced Concrete Buildings. Journal of Earthquake Engineering 10, 533-565, 2006 [3] Juan C de la Llera, Anil K Chopra, Understanding the inelastic seismic behaviour of asymmetric plan buildings. Earthquake Engineering and Structural Dynamics, 24, 549-572, 1995

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