Pushover Analysis for Plan Irregular Building Structures

Abstract

Nonlinear static procedures (NSPs), also known as "pushover methods", represent the most used tool in the professional practice for assessment of seismic performance of building structures. Most of the methods subscribed by major seismic codes for seismic analysis of new or existing buildings have been originally defined for simple regular structures.Nevertheless, perfect regularity is an idealization that very rarely occurs and, in principle, the concept of irregularity itself is a fuzzy one. Most codes attempt to give a definition to the concept of "regularity", considering issues related to the distribution of mass, stiffness and strength in the building, both in plan and in elevation. Real buildings rarely comply with these regularity requirements, resulting in a barely reliable application of the basic NSPs. Code specifications concerning irregular structures are in need of improvement and they do not provide for clear and specific guidelines for the seismic analysis of such structures. Therefore the problem of the seismic evaluation of irregular structures is still an open one and basic issues need to be further explored.The present paper aims at providing a wide outlook on the problem of the seismic assessment of plan irregular building structures. Firstly, a brief review of the elastic and inelastic methods for the assessment of the torsional effects induced by in-plan irregularity is presented, mainly aimed at the definition of the variables governing the problem. Then, the basic features of the most important NSPs are discussed, followed by the description of the recent improvements developed for irregular structures. Since there is not yet a fully satisfactory solution, pros and cons of the various approaches are outlined, highlighting the most promising methods and the issues that are yet to be investigated. Finally, recommendations for code improvement are suggested.

Overview on the Nonlinear Static Procedures and Performance-Based Approach on Modern Unreinforced Masonry Buildings with Structural Irregularity

“…In general terms, the definition is based on the distribution of mass, stiffness and strength. However, the criteria given for the definition of irregularity are not sufficient to capture a variety of cases, such as irregularity due to progressive damage, or a combination of both plan, and vertical irregularities [32]. It should be noted that the definition of structural irregularity differs in different codes, as listed in Tables A1 and A2 in Appendix A.…”

A sustainable material for sustainable architecture: wood in parasite architecture

“…In both cases, the increase in masses, the displacement of the center of gravity of the stiffnesses and the modification of the shape ratios determine a modification of the seismic behavior of the system in the post-operative configuration. In the latter case, in-depth assessments of the torsional behavior of the building as a whole are required (De Stefano et al, 2014;Faella et al, 2010). Figure 5 shows an example of an isolated parasitic volumetric addition.…”

Pushover analysis of unreinforced irregular masonry buildings: Lessons from different modeling approaches

“…According to past research, the application of the displacement-based design to masonry structures is not straightforward, and the same has been mostly applied on frame systems, such as reinforced concrete and steel buildings [21][22][23][24]. Thus, further investigation is required to adopt pushover analysis in a more systematic strategy for masonry structures with box behavior, particularly for buildings with structural irregularities to consider torsional effects imposed by its own configuration under seismic actions [19,25,26]. Such consideration is crucial because the seismic design and analysis codes are directed to regular structures whose dynamic behavior is governed mostly by translation, and they do not represent the response of the structural systems with irregularities [25].…”

“…Thus, further investigation is required to adopt pushover analysis in a more systematic strategy for masonry structures with box behavior, particularly for buildings with structural irregularities to consider torsional effects imposed by its own configuration under seismic actions [19,25,26]. Such consideration is crucial because the seismic design and analysis codes are directed to regular structures whose dynamic behavior is governed mostly by translation, and they do not represent the response of the structural systems with irregularities [25]. [1] Within this framework, it is important to define appropriate modeling strategies to perform nonlinear analysis of URM buildings under seismic actions.…”