Evaluating Performance of Concrete Special Moment Resisting Frames with Different Seismic Coefficients Using Endurance Time Method

Hadi Radmanesh,Majid Mohammadi

doi:10.28991/cej-030971

Hadi Radmanesh, Majid Mohammadi

Open Access

https://doi.org/10.28991/cej-030971

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Abstract

This performance-based study was conducted to investigate the effects of seismic coefficients on performance of concrete special moment frames of 5,7, and 10-storey buildings located in Tehran, Iran. The structures are designed three-dimensionally by ETABS 2016 software according to ACI-318-08. Fifteen specimens were designed with different base shears having seismic coefficients of 0.7, 0.85, 1, 1.15, and 1.30 times the proposed value of Iranian Standard 2800, (i.e. decreased by 70 and 85%, and increased by 115 and 130%). Endurance time method (ETA20in series of ET acceleration function) as well as three real earthquake records was employed to evaluate the seismic performance of the modeled structures. The performance of structures was compared by the time of the first plastic hinges formation in beams and columns, the time of entering to nonlinear region and the time of experiencing storey drift of 2% corresponding to the life safety performance level. It was observed that the results of ET records and real records were similar to each other. A procedure was proposed for finding optimum structure with lower weight using ET method through defining efficient ratio (ER) and cost ratio (CR). Based on the results of ER/CR ratio and considering the importance of collapse prevention performance level, optimum structure was a 7-storey structure with lower weight or cost whose seismic coefficient had been reduced by 70%. It was concluded that high safety can not be achieved simply by increasing the seismic coefficient of structures.

Highlights

The stability of the building against earthquakes is a necessity
The studied structures are three concrete special moment frames with 5, 7, and 10 storeys located in Tehran, Iran on soil type C conditions which were three-dimensionally modeled and designed using ETABS 2016 software according to seismic loading requirements of ACI-318-08
According to the time of plastic hinges formation in beams and columns of structures shown in Table 2, it was reported that 5-story with 1.15C, 7-storey with 0.7C, and 10-storey with 1C had better seismic performance at Immediate Occupancy (IO)-Life Safety (LS) level compared to other structures

Summary

Introduction

Many studies have been conducted on estimating the performance of structures during and after earthquakes to prevent destruction and death caused by earthquake This valuable goal has led to the emergence of many regulations and standards aimed to advance previous rules. One of these methods has been developed by SEAOC Vision 2000 Committee in 1995 [1] called performance-based earthquake engineering where structural design criteria are expressed in terms of achieving a set of different performance levels including Collapse Prevention (CP), Life Safety (LS), or Immediate Occupancy (IO). A new technique for time history seismic analysis of structures has been developed where the structure is subjected to accelerograms that impose increasing dynamic demand on the

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