Reducing eccentricity in plan-irregular buildings through an innovative stiffening solution of the façade frames

Adjusting to architectonic and urbanistic constraints in dense cities frequently require plan irregularities in structures. One recurrent case in many cities is the combination of a frame in the façade, to allow parking access, with structural walls in other perimeter axes, for drift control. In long structures, this solution creates large eccentricities between the mass and stiffness centres. This paper investigates one solution that significantly increases the stiffness of the façade frame, without affecting its functionality. The concept consists on creating vertical elements in the inner spans of the intermittent stories, producing a Vierendeel-effect in the frame. The stiffer frame closes the distance between the centres of stiffness and mass. The behaviour and possible variation of the failure mode are discussed in the paper, and recommendations for the capacity design of the façade frame are given. It is found that the additional vertical element does not contribute in the gravity load system; hence, it should not be considered as an intermittent column irregularity. This concept is applied to a 10-story plan-irregular building, with hypothetical location in Lima (Perú), and its seismic performance is assessed. Compared to the original solution, the maximum floor displacement was reduced up to 30%. The dominant period of vibration was reduced up to 15%. The recommended capacity-design condition allowed ductile behaviour without local collapse for demands larger than the MCE.The authors acknowledge support of the Spanish State Research Agency and the European Funds for Regional Development, through the research project RTI2018-097314-BC21.Postprint (published version