جستجوی مقالات مرتبط با کلیدواژه « collapse prevention » در نشریات گروه « فنی و مهندسی »

The new techniques in seismic design of structures are usually attributed to highdamping ratios. Mass isolation of structures is one of the new techniques in seismicdesign of structures that focuses on the mass of the structure as the main target forseismic isolation and reducing earthquake effects on buildings. Mass IsolationSystem (MIS) consists of two stiff and soft substructures connected by a viscousdamper. The mass subsystem comprises the main mass of the structure, which isattached to a frame with a low stiffness by a separation mechanism at the height ofthe structure including viscous dampers to a stiffness subsystem consisting of amoment or braced frame system with great stiffness. In this paper, the aim is topresent a simple preliminary design method based on the normalized pushovercurve. The most important problems for increasing the period of the soft structureare deformation and structural stability. This paper presents a preliminary designsolution for a soft substructure of the Mass Isolation System (MIS) with considerationof stability constraints. To this end, the paper presents mathematicalrelationships to calculate the period of the structure followed by proposing a simplesolution for the design of the soft substructure.

Vertical mass isolation is one of the new techniques in the seismic design ofstructures that consists of two stiff and soft substructures connected by viscous dampers.Adding to the flexibility and energy dissipation potential of the system is the mainfeature of some new approaches in the seismic design of structures. Extra flexibilityhelps to reduce earthquake-induced forces and accelerations in the building andprovides higher energy dissipation potential for the system (by creating largerelative deformations in the structure). Mass subsystem possesses low lateralstiffness but carries the major part of the mass system. Stiffness subsystem, however,controls the deformation of the mass subsystem and attributes with much higherstiffness. In this paper, the aim is to find the limitation of the stability of asoft structure and to obtain the maximum period available for a soft structure.According to the studies, the most important obstruction in increasing the periodof the soft structure, assuming control of its deformation by connecting to thestiff substructure, is to maintain the stability of the structure. In this paper, first, arelationship has been presented to calculate the period of the structure in terms ofthe stability factor that estimates the period of structure with good agreement byanalytical results. This paper deals with presenting a procedure for designing theMass Isolation System (MIS) with consideration of stability constraints. To this end,the paper presents mathematical solutions to calculate the period of the structurefollowed by proposing a design procedure of the soft substructure.

The research leading to this paper was prompted by the need to estimate strength and stiffness of Rigid Rocking Cores (RRCs) as essential elements of resilient earthquake resisting structures. While a limited number of such studies have been reported, no general study in terms of physical properties of RRCs, their appendages and adjoining structures have been published. Despite the growing knowledge on RRCs there are no design guidelines on their applications for seismic protection of buildings. The purpose of the present article is to propose effective rigidity limits beyond which it would be unproductive to use stiffer cores and to provide basic guidelines for the preliminary design of RRCs with a view to collapse prevention, re-centering and post-earthquake repairs/replacements. Several examples supported by computer analysis have been provided to demonstrate the applications and the validity of the proposed solutions.

This paper introduces a novel design concept for the development of efficient, sustainable Rocking-Wall Moment Frames (RWMFs) under seismic conditions. The proposed concepts lead to a novel structural configuration with provisions for Collapse Prevention (CP), Self-Centering (SC), reparability, performance control (PC), damage reduction, and energy based seismic analysis. It introduces the merits of design led analysis (DLA) over the traditional methods of approach, followed by the development of a lateral resisting system that is more efficient than its conventional counterparts. The fundamental idea behind the proposed methodology is that seismic structural response is mainly a function of design and construction, rather than numerical analysis. In design led analysis the rules of mechanics and structural design are induced rather than followed .The new system is a combination of grade beam restrained moment frames and articulated shear walls, tied to each other by means of post tensioned (PT) stabilizers and Gap Opening Link Beams (GOLBs).

The paper introduces a new earthquake resistant rocking-wall moment frame (RWMF) that is capable of damage reduction, collapse avoidance and self-centering due to strong ground motion. The system consists of a grade beam restrained moment frame, (GBRMF) attached to a co-planar, post tensioned (PT) rigid rocking core (RRC) by means of gap opening link beams (GOLBs) and buckling restrained braces (BRBs). Several practical details aiming at damage reduction have been presented. Worked examples have also been provided to demonstrate the validity of the proposed solutions. All results have been verified by independent computer analysis. The proposed formulae are ideally suited for preliminary design and teaching purposes.