Zakariya Waezi

The structural control of the building is a critical part of mitigating the catastrophic consequences of the earthquakes. The active control of structures has gained popularity in the construction industry because of its ability to adapt to different ground motion characteristics. The active tuned mass damper (ATMD) is one of the most versatile devices used for active structural control. This paper uses the ATMD and variable fractional order fuzzy PID (VFOFPID) controller for improving the performance of building structures subjected to horizontal ground motions. Having obtained the response of an 11-story shear building with this controller, the optimized control forces are determined through the pattern search algorithm and the performance indices of the system subjected to 100 different ground motions are evaluated. The performance indices are compared with those of uncontrolled as well as genetic fuzzy and fuzzy PID controlled structure. The results indicate that the VFOFPID controller proposed here can effectively reduce the drift and the absolute acceleration of the structure.

In this paper, we introduce a semi-analytic procedure for deriving the response spectrum of the synthetic acceleration records generated using the Double Frequency Model (DFM). DFM is a filtered white noise method for fully non-stationarity synthetic acceleration records. The proposed semi-analytic procedure is based on the theory of the first passage problem, which precludes time and computationally extensive methods e.g. Monte Carlo simulations. Assuming a slowly-varying envelope and evolutionary transfer functions, the procedure for estimating the elastic response of a structure is implemented in both time and frequency domains. Comparing the results of our model with previous models and approximations, we conclude that for a set of 10000 realizations of the DFM model, the semi-analytic model produces less than 10% error for 92% of the realizations. The accuracy of estimations is higher in the short-period compared to the long-period ranges of the response spectrum. Comparing the accuracy of approximations used to arrive at peak factors, results show that Michaelov et al's approximation executed in the frequency domain yields the best results compared to Poisson or Vanmarcke’s procedures.

Since the friction dampers possess constant friction forces, they cannot play a significant role in mitigating the strong earthquakes' demands. The application of the variable-force friction dampers is one way of circumventing this problem. In this paper, the design parameters of a specific force-variable friction damper namely Arc-Surfaced Friction Dampers (ASFD) have been investigated and their effect on the efficiency of their performance has been assessed. To this end, a 4-story structure designed according to Iranian Building Code Standard-2800 equipped with an ordinary frictional damper (LSB) and an ASFD has been excited by an ensemble of near- and far-field ground motions. To determine the optimal ASFD parameters, which in here reflected as the initial sliding force and the radius of curvature of the ASFD, the response of the structure due to 44 FEMA-p695 ground motions scaled to the elastic design spectra corresponding to 10% of exceedance in 50 years are estimated. The nonlinear dynamic analysis has provided a basis to define the optimal parameters concerning the life-safety and collapse-prevention performance. The results showed that implementing the ASFD as a control device has significantly reduced the median spectral acceleration corresponding to the onset of collapse compared to the uncontrolled structures.

This paper illustrates a novel method for stochastic simulation of the vertical components of the near-field pulse-less earthquakes. The model parameters are estimated for 120 near-field records and regressed against the scenario parameters including moment magnitude, epicentral distance, hypocentral depth, and the shear-wave velocity. The model is verified by simulating records for nine different scenarios and the 50^th and 84^th percentile values of the resulted spectrum are compared with the NGA-West2 vertical attenuation results. The results show that the proposed model can generate vertical records according to scenario cases in which their response spectrum is compatible with those of NGA-West2 GMPEs.

This paper investigates the seismic behavior of the rectangular-reinforced concrete columns subjected to pure flexure, pure torsion, and combined flexural-torsional loadings using 4 quarter-scaled experimental specimens. During flexural-torsional loading, the axial rotation to the relative displacement ratios were considered to be 2 and 4. The ultimate displacement capacity and the flexural moment capacities of the specimens under combined flexural-torsional loadings were found to be decreased compared to the pure-flexural case for different rotation over drift ratios. An equation expressing the interaction curve between the flexural and torsional moment strength capacity of rectangular-reinforced concrete sections is proposed.

In this paper, the effectiveness of using nonlinear fluid/structure interaction for controlling the seismic response of the structures under near-field earthquake is investigated. For this purpose an SDOF Structure is considered which is equipped with the circular cylindrical liquid tank. Considering its fundamental mode of vibration, the structure is an idealised model of multi-degree of freedom system. Under 72 horizontal near-field earthquake excitations, the dynamic response of this system is examined studying three liquid sloshing modes. The dynamic response is investigated in the neighbourhood of 1:1 resonance between first unsymmetrical sloshing mode and SDOF structural mode. For this matter, most of the pulse-like earthquakes identified by Baker from NGA-West2 database and some other well-known near-field earthquakes have been used as base excitation. The Energy flow from the structural mode to the first unsymmetrical liquid sloshing mode is explored, and the proficiency of the appended liquid tanks in reducing the dynamic response of the structural system under pulse-liked earthquake is shown. The results show appropriate response reduction using the fluid oscillations for the structure subjected to pulse-like excitations.