Seismic reliability analysis of steel moment-resisting frames retrofitted by vertical link elements using combined series–parallel system approach

AbstractThe eccentric bracing system equipped with vertical links is capable of providing high levels of stiffness, strength and ductility, and therefore, can be efficiently used for seismic retrofit of existing structures. This study aims to investigate the seismic reliability of steel moment-resisting frames retrofitted by this system using a novel combined series–parallel system approach. The seismic response of 4, 8 and 12-storey steel moment-resisting frames (MRFs) are evaluated under a set of design basis earthquakes (DBE) before and after retrofitting intervention. Adopting an engineering demand parameter approach (EDP-Based) for reliability assessment and development of analytical models for the frames using systems consisting of the series–parallel elements are the major distinctions between the present study and the other similar works. To estimate the global reliability of the frames, first, the reliability of each storey is individually derived based on various probable damage levels for the lateral-load resisting members. Then, the seismic reliability of the frame is globally obtained by combining the reliability of each storey for different damage levels in the lateral load-resisting subsystems. The results indicate significant impact of this type of bracing system on improvement of the performance level and load-carrying capacity of the frames along with reduction of the lateral displacements. It is shown that application of the vertical links can reduce the maximum inter-storey drifts by at least 60%, while it leads to at most 17% increase in the base shear. All retrofitted frames exhibited a performance level higher than the Life Safety (LS) when subjected to the DBE hazard level records (earthquakes with return period of 475 years). At the same level of earthquake intensity, in the cases when the drift corresponding to the LS performance level is used as the target, the reliability of the retrofitted frames was improved by more than 90% compared to the original frames for all damage states developed in the vertical links.

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Effect of Standard No. 2800 Rules for Moment Resisting Frames on the Elastic and Inelastic Behavior of Dual Steel Systems

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.1040 ◽

2017 ◽

Vol 7 (6) ◽

pp. 2139-2146 ◽

Cited By ~ 1

Author(s):

H. Veladi ◽

H. Najafi

Keyword(s):

Steel Structures ◽

Lateral Load ◽

Nonlinear Static Analysis ◽

Inelastic Behavior ◽

Braced Frame ◽

Moment Resisting Frames ◽

Seismic Design Code ◽

Moment Resisting ◽

Bracing System ◽

Steel Braced Frame

According to most valid Design Codes including the Iranian Seismic Design Code (Standard No. 2800), moment resisting frames in dual systems must have the ability of resisting the 25% of the total lateral load of the dual system independently. This study is conducted to investigate the implementation of this rule for dual steel structures with two types of steel braced frame. Also, its effect on the strength of the structure and the distribution of lateral load between the frames and the bracing system is evaluated. In order to investigate the effect of that rule, structural models with 5, 10 and 15 floors are modeled. Nonlinear static analysis is employed and results are discussed. Following the Standard No. 2008 seems to increase the structure’s lateral resistance and decrease the number of elements entered into the inelastic behavior stage. In general, the structure has a more desirable inelastic behavior.

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Seismic Reliability Assessment of Steel Moment-Resisting Frames using Bayes Estimators

Proceedings of the Institution of Civil Engineers - Structures and Buildings ◽

10.1680/jstbu.20.00211 ◽

2021 ◽

pp. 1-32

Author(s):

Vahid Mohsenian ◽

Iman Hajirasouliha ◽

Reza Filizadeh

Keyword(s):

Reliability Assessment ◽

Bayes Estimators ◽

Seismic Reliability ◽

Steel Moment Resisting Frames ◽

Moment Resisting Frames ◽

Moment Resisting

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An improvement of direct displacement-based design approach for steel moment-resisting frames controlled by fluid viscous dampers

Advances in Structural Engineering ◽

10.1177/1369433221992496 ◽

2021 ◽

pp. 136943322199249

Author(s):

Mahsa Noruzvand ◽

Mohtasham Mohebbi ◽

Kazem Shakeri

Keyword(s):

Performance Level ◽

Design Approach ◽

Excellent Performance ◽

Steel Moment Resisting Frames ◽

Moment Resisting Frames ◽

Earthquake Records ◽

Direct Displacement Based Design ◽

Moment Resisting ◽

Displacement Based ◽

Spectral Velocity

Direct displacement-based design (DDBD) method is one of the most effective methods for performance-base design of structures that has been also employed to design structures controlled by fluid viscous damper (FVD). In previous studies, a modified DDBD has been developed to apply the higher mode effects as well as difference between spectral velocity and pseudo-spectral velocity on the design velocity of FVD. To this end, two constants were defined to correct the damping coefficient of FVD that these correction constants had been determined in a non-classical and iterative manner. In this study, a new classical method is proposed for determining these constant such that no iteration is required in DDBD. In order to be able to introduce this design approach as a reliable framework, its performance is validated under different sets of earthquake records and this design approach is also developed for structures controlled by nonlinear FVD. Steel moment-resisting frames with different numbers of stories have been designed using this method. For comparison, structures have been also designed based on DDBD proposed in previous researches. The results show that DDBD approach improved in this study is capable to achieve the design performance level under different sets of earthquake records and this design approach has more effective performance than previous design methods. Performance of steel moment-resisting frames equipped with nonlinear FVD also shows excellent performance of this design approach in achievement of desirable performance level. Therefore, DDBD approach proposed in this study can be introduced as a new classical and reliable framework because of its simplicity and excellent performance under different sets of earthquakes.

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