###### Abstract  
A proposal to control the structural bounding hazard imposed on multistory reinforced concrete (RC) structures is presented. The main goal is to guarantee the seismic performance of a structure with an acceptable (predefined) risk-targeted parameter without the need to eliminate structural bounding collisions. The key target parameters of this study are the annual probability of exceeding an engineering demand parameter (EDP) capacity level and the separation distance \(\mathrm{d_{g}}\) between adjacent structures. In this direction, a method that ensures the performance level of critical EDPs due to structural bounding conditions is proposed. The new method involves two decision frameworks that define (a) the optimal separation gap distance \(\mathrm{d_{g,min}^{P_{i}}}\)) at a targeted value of bounding risk (probability per year) \(\mathrm{P_{t}}\) (Decision A) and (b) the minimum acceptable structural bounding risk \(\mathrm{P_{min}^{d_{g}}}\) at a targeted value of separation gap distance \(\mathrm{d_{g,t}}\) (Decision B). The demand parameters that are incorporated in the proposed method are the peak relative displacement \(\mathrm{\delta_{max}}\) at the top level of colliding without considering bounding conditions and any other critical EDP due to the structural bounding effect. The overall method is based on two distinct acceptable performance objectives, the POs-\(\mathrm{\delta_{max}}\) and the POs-EDP, defined as a function of P vs. \(\mathrm{d_{g}}\). For this purpose, a seismic hazard curve compatible with Eurocode's 8 hazard zone is adopted, and the corresponding demand hazard curves of \(\mathrm{\delta_{max}}\) and EDP are developed. The proposed method is implemented to study the floor-to-floor structural bounding hazard of an eight-story RC frame taking into account different risk-targeted scenarios. The results show that the seismic risk (probability per year) of exceeding the EDP's capacity level is significantly increased due to structural bounding in comparison to the case of no bounding. Calibration of the structural bounding risk can be obtained by adjusting the separation gap distance \(\mathrm{d_{g}}\) between the adjacent structures based on the acceptable POs. The POs-\(\mathrm{\delta_{max}}\) is not always an accurate criterion for verifying the capacity level of the critical EDP. Finally, with the proposed method, a variety of POs-EDPs can be used to control the structural bounding risk in terms of \(\mathrm{d_{g,min}^{P_{i}}}\) and/or \(\mathrm{P_{min}^{d_{g}}}\). structural bounding; separation distance; MAF; probability per year; bounding risk; performance objective; inelastic demands; multistory reinforced concrete structure; Eurocode 8 20242020242  
separation distance is estimated based on a uniform hazard spectrum that inaccurately results in the assumption of uniform-collapse capacity of structures [13; 14]. Further, recent deterministic-based results indicate less conservative demands on separation gap distance at certain levels of seismic hazard in comparison to the Eurocode 8 provisions [11]. The probabilistic evaluation of the structural bounding has also been the objective of several researchers [15]. The first studies included reliability methods between adjacent linear or bilinear SDOF or MDOF structural systems [16; 17; 18; 19; 20; 21; 22]. Thereafter, fragility-based assessment methods were used to evaluate the seismic demands of adjacent structures (RC or steel) due to the bounding effect [15; 23; 24]. In these studies, displacement-based EDPs (e.g., maximum interstory drift ratio) accounting for different limit states have been examined. [PERSON] and [PERSON] [15] introduced new outcomes in the fragility analysis of the structural bounding effect comprising the interstory (floor-to-column) interaction case and the inelastic demands of critical RC structural members. For structural bounding conditions, linear and bilinear PSDMs have also been developed to accurately describe the relationship between the EDPs and the seismic intensity measures (IMs).