Ambient vibration tests on a 19 – story asymmetric steel building

H. Shakib,N. Parsaeifard 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.1

Ambient vibration tests were carried out to evaluate the dynamic properties of an asymmetric steel building with semi-rigid connections. The test case has many non-structural elements, constructed in the city of Tehran (Iran). The tests were conducted to obtain natural frequencies, mode shapes and damping ratio of the structure and then Fourier transform were used to analyze the velocity records obtained from the tests. The first and second natural periods of the building were obtained as 1.37 s and 1.28 s through the test and damping ratio for the first mode was calculated as 0.047. However, Natural periods obtained from finite element model have higher values from those gained from ambient vibration. Then the model was calibrated by modeling of the in-fill masonry panels at their exact locations and considering the boundary conditions by modeling two blocks near the block No. 3, but the differences were existed. These differences may be due to some hidden stiffness of nonstructural elements in the low range of elastic behavior, showing the structure stiffer than it is in reality.

Ambient vibration tests on a 19 - story asymmetric steel building

Shakib, H.,Parsaeifard, N. Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.1

Ambient vibration tests were carried out to evaluate the dynamic properties of an asymmetric steel building with semi-rigid connections. The test case has many non-structural elements, constructed in the city of Tehran (Iran). The tests were conducted to obtain natural frequencies, mode shapes and damping ratio of the structure and then Fourier transform were used to analyze the velocity records obtained from the tests. The first and second natural periods of the building were obtained as 1.37 s and 1.28 s through the test and damping ratio for the first mode was calculated as 0.047. However, Natural periods obtained from finite element model have higher values from those gained from ambient vibration. Then the model was calibrated by modeling of the in-fill masonry panels at their exact locations and considering the boundary conditions by modeling two blocks near the block No. 3, but the differences were existed. These differences may be due to some hidden stiffness of nonstructural elements in the low range of elastic behavior, showing the structure stiffer than it is in reality.

Seismic Response Evaluation of the RC Elevated Water Tank with Fluid-Structure Interaction and Earthquake Ensemble

F. Omidinasab,H. Shakib 대한토목학회 2012 KSCE JOURNAL OF CIVIL ENGINEERING Vol.16 No.3

In this paper, a reinforced concrete elevated water tank, with a capacity of 900 cubic meters and height of 32 meters, has been utilized and subjected to an ensemble of earthquake records. Finite element model has been employed to model elevated water tank system. Fluid-structure interaction for modeling is considered by Eulerian method. Also the behaviors of concrete and steel material were considered to be nonlinear. Seismic responses of the elevated water tank such as base shear force, overturning moment,displacement and hydrodynamic pressure have been assessed for ensemble earthquake records. The obtained result revealed that scattering of responses in range of the mean minus standard deviation and mean plus standard deviation are approximately 60 to 70percents. Also, responses of elevated water tank are dependent with earthquake characteristics and frequency of elevated water tank. The maximum response of base shear force, overturning moment, displacement and hydrodynamic pressure occurred in different case of vessel filling.

On a Reliability-Based Method to Improve the Seismic Performance of Midrise Steel Moment Resisting Frame Setback Buildings

M. Pirizadeh,H. Shakib 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.1

A framework is proposed to improve seismic performance of special steel moment resisting frame (SMRF) setback structures based on the reliability-based approach. In this procedure, seismic design of midrise setback structures is modifi ed to improve the confi dence level of meeting the life safety performance level in these structures to a reliable level. To achieve this, based on the results of the incremental dynamic analysis, an algorithm is proposed to introduce more accurate equations to predict the maximum inelastic inter-story drift ratio of setback structures in linear force-based design methods. It is observed that by applying the proposed relations in the seismic design of setback buildings, this type of structures demonstrates more reliable seismic performance compared to the code-designed approach. The proposed method is economically eff ective in reducing the possible losses during the lifetime of SMRF setback buildings located in seismic prone areas.

Distribution of strength and stiffness in asymmetric wall type system buildings considering foundation flexibility

Gh.R. Atefatdoost,H. Shakib,B. JavidSharifi 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.3

Architecture constraints in buildings may typically cause irregularities in the distribution of stiffness and mass and consequently causes non-compliance of centers of mass, stiffness and strength. Such buildings are known as asymmetric buildings the distribution of strength and stiffness is one of whose main challenges. This distribution is more complicated for concrete buildings with RC shear walls in which stiffness and strength are interdependent parameters. The flexibility under the foundation is another subject that can affect this distribution due to the variation of dynamic properties of the structure and its constituting elements. In this paper, it is attempted to achieve an appropriate distribution pattern by expressing the effects of foundation flexibility on the seismic demand of concrete shear walls and also evaluate the effects of this issue on strength and stiffness distribution among lateral force resistant elements. In order to understand the importance of flexibility in strength and stiffness distribution for an asymmetric building in different conditions of under-foundation flexibility, the assigned value to each of the walls is numerically calculated and eventually a procedure for strength and stiffness distribution dependencies on flexibility is provided.

Distribution of strength and stiffness in asymmetric wall type system buildings considering foundation flexibility

Atefatdoost, Gh.R.,Shakib, H.,JavidSharifi, B. Techno-Press 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.3

Architecture constraints in buildings may typically cause irregularities in the distribution of stiffness and mass and consequently causes non-compliance of centers of mass, stiffness and strength. Such buildings are known as asymmetric buildings the distribution of strength and stiffness is one of whose main challenges. This distribution is more complicated for concrete buildings with RC shear walls in which stiffness and strength are interdependent parameters. The flexibility under the foundation is another subject that can affect this distribution due to the variation of dynamic properties of the structure and its constituting elements. In this paper, it is attempted to achieve an appropriate distribution pattern by expressing the effects of foundation flexibility on the seismic demand of concrete shear walls and also evaluate the effects of this issue on strength and stiffness distribution among lateral force resistant elements. In order to understand the importance of flexibility in strength and stiffness distribution for an asymmetric building in different conditions of under-foundation flexibility, the assigned value to each of the walls is numerically calculated and eventually a procedure for strength and stiffness distribution dependencies on flexibility is provided.