A design procedure for suspended zipper‐braced frames in the framework of Eurocode 8

Rossi

2018

Self Cite

Summary The paper describes a design procedure for a special type of chevron braced frame endowed with ties between the upper ends of the braces of adjacent storeys. Unlike conventional or suspended zipper braced frames, the braces on one side of the braced span—along with the adjacent columns and ties—are part of a vertical truss system that is hinged at the base and designed to remain elastic until the near collapse limit state has been reached. The braces on the other side of the braced span consist of buckling‐restrained braces and are designed to provide energy dissipation. The design procedure stems from a design method proposed in the past for rocking eccentrically braced structures and applies capacity design principles. The accuracy of the procedure is proved by means of nonlinear dynamic analysis of multistorey systems with different geometric and mechanical properties. To highlight further the qualities of the examined type and evaluate the cost‐effective range of application, a comparison is made with other braced types in terms of cost of structural steel and seismic performance.

Section: Rbrbfs Vs Other Braced Framesmentioning

confidence: 99%

Section: Rbrbfs Vs Other Braced Framesmentioning

confidence: 99%

Section: Rbrbfs Vs Other Braced Framesmentioning

confidence: 99%

See 1 more Smart Citation

A design procedure for pin‐supported rocking buckling‐restrained braced frames

Rossi

2018

Self Cite

“…Assuming that the existing braced system needs to be retrofitted to perform properly for an assigned level of the earthquake ground motion, pin‐supported rocking walls are added to the existing system. Based on the results of past research studies, the retrofitted system is designed to fulfil the NC limit state requirements when subjected to ground motions with peak ground acceleration (PGA) characterised by 2% probability of exceedance in 50 years ( a gd,NC ).…”

Section: Outline Of the Proposed Design Proceduresmentioning

confidence: 99%

“…If the maximum positive and negative horizontal displacements of the beam are equal, the horizontal displacement u f corresponding to the achievement of the ductility capacity of the brace μ f may be calculated as proposed in Rossi and Quaceci

u_{f} = \frac{1}{2 ζ} ({}, + italicLζ + \sqrt{L^{2} ζ^{2} - 4 ζ ([], \frac{L^{4}}{4 δ_{u}^{2}} - \frac{L^{2}}{2} + \frac{δ_{normalu}^{2}}{4} - {(h - v_{normalb})}^{2})}) - \frac{L}{2}

where h is the interstorey height, δ u is the axial displacement capacity of the brace (ie, μ f times the elongation at yield δ y ),

ζ = L_{d}^{2} / δ_{u}^{2} + 1

, and L d is the length of the brace.…”

Section: Concentrically Braced Frames + Pin‐supported Rocking Walls (mentioning

confidence: 99%

Seismic retrofitting of braced frame buildings by RC rocking walls and viscous dampers

Barbagallo

et al. 2018

Self Cite

Summary A design procedure for seismic retrofitting of concentrically and eccentrically braced frame buildings is proposed and validated in this paper. Rocking walls are added to the existing system to ensure an almost uniform distribution of the interstorey displacement in elevation. To achieve direct and efficient control over the seismic performance, the design procedure is founded on the displacement‐based approach and makes use of overdamped elastic response spectra. The top displacement capacity of the building is evaluated based on a rigid lateral deformed configuration of the structure and on the ductility capacity of the dissipative members of the braced frames. The equivalent viscous damping ratio of the braced structure with rocking walls is calculated based on semi‐empirical relationships specifically calibrated in this paper for concentrically and eccentrically braced frames. If the equivalent viscous damping ratio of the structure is lower than the required equivalent viscous damping ratio, viscous dampers are added and arranged between the rocking walls and adjacent reaction columns. The design internal forces of the rocking walls are evaluated considering the contributions of more than one mode of vibration. The proposed design procedure is applied to a large set of archetype braced frame buildings and its effectiveness verified by nonlinear dynamic analysis.

Proposal and validation of a design procedure for concentrically braced frames in the chevron configuration

Barbagallo

et al. 2021

Self Cite

In the recent past, several research studies have highlighted that the prescriptions reported in codes for the design of structures with concentric braces in the chevron configuration are often not effective in preventing yielding or buckling of non‐dissipative members and in ensuring collapse mechanisms characterised by uniform damage of braces. To investigate the reasons of these deficiencies, in this paper the seismic response of concentrically braced structures designed according to procedures reported in the literature and in the European seismic code is first examined. Then, a new design procedure is proposed, in which the innovative aspects are mainly related to the estimation of the bending moments in columns and to the formulation of requirements on the stiffness of braced beams and columns. The impact of the proposed procedure on the structural costs is computed on a large number of buildings characterised by different occupancy types and geometric properties. The seismic performance of these structures is evaluated by incremental nonlinear dynamic analysis and discussed at the achievement of the significant damage and near‐collapse limit states.