mohammadjavad hamidia

Structural control mechanisms are used as a reliable and efficient methods to enhance seismic performance and stability of structures. Ensuring the integrity and stability of civil infrastructures such as marine structures, especially oil platforms exposed to difficult environmental conditions, poses challenges that engineers strive to overcome. Introducing innovative methods and improving existing system performance can significantly aid in addressing these challenges. The objective of the present research is to investigate the effect of different levels of pre-stressing on shape memory alloy wires in a passive damper based on shape memory alloy and its impact on reducing the seismic re-sponse of marine structures. For this purpose, a simplified marine structure is modeled, and a struc-tural control system with a passive damper using shape memory alloy is incorporated. The results of different scenarios after applying seven sets of scaled ground motions from far field earthquakes and time history analyses have been evaluated. The obtained results indicate that increasing the cross-sectional area of the wires and increasing their pre-stress level reduces the maximum displacement of the structure and improves the overall performance of the structural control system. Furthermore, considering three different scenarios for the frame, the influence of frame stiffness on the results has been assessed.

The purpose of this study is to quantify the damage of reinforced concrete shear walls after the earthquakes. One of the most important tasks after earthquakes is to assess the buildings and make sure that they are safe to occupy. So far, this assessment is mostly conducted by visual inspection and measuring the crack width that is prone to error. Thus, automation of the damage assessment using image processing techniques can significantly improve the assessment accuracy. In this paper, a database comprising 236 images of 72 damaged walls at various drift levels is collected. The database covers a broad range of structural and geometric properties. The crack pattern associated with each wall and each drift ratio is one by one extracted manually, and the corresponding geometry indices of each crack pattern are calculated. The indices are assessed and the correlation with drift ratio is investigated. Finally, using symbolic regression, empirical equations are proposed that can predict the peak drift ratio that the wall has experienced during an earthquake using the crack pattern. Four scenarios are considered for obtaining the empirical equations. The predicted drift ratio along with fragility curves can finally be used to estimate the damage level of the walls.

Robust estimation of fundamental elastic period of the buildings is essential for obtaining realistic seismic base shear. Seismic design codes provide a variety of equations to calculate the fundamental elastic period of vibration for steel moment frame buildings. The empirical equations are mainly based on the building height and does not take into account the effects of irregularity and soil-structure interaction. In this paper, an empirical predictive equation is developed to estimate the fundamental elastic period of steel moment frames. The predictive equation includes parameters that represent irregularity effects and soil-structure interaction . The database used in this study consists architectural and geotechnical data for 45 building cases. The proposed predictive equation shows satisfactory accuracy. The predicted results are then compared to the values obtained from Iranian 2800 seismic design code, ASCE7-16 and UBC-97. The proposed predictive equation is also verified by 10 fundamental elastic periods obtained from analytical models. The fundamental elastic period obtained using the predictive equations are specifically more accurate for mid- and high-rise buildings compared to seismic design codes. The values obtained from seismic codes are well below the realistic values for the buildings.

Seismic base isolation is a practical solution to reduce the seismic demand on civil infrastructures. In this paper, the maximum displacements of friction pendulum isolators resulting from simplified method pre-scribed by ASCE7-16 are compared with the results from nonlinear response history dynamic analyses for near-field pulse-like and non-pulse-like earthquakes. The maximum displacements of the friction pendulum isolators with four different coefficients of friction and four effective radii have been determined using simplified methods pre-scribed by ASCE7-16. Nonlinear response history dynamic analyses are then performed for the 16 aforementioned cases using OpenSees under seven near-field pulse-like earthquake records and seven near-field non-pulse-like earthquake. Adjustment factors are finally developed for the simplified method of ASCE7-16 to update the predictions. The results show that the values predicted by the code are less than the values obtained from nonlinear time history analysis. In addition, the adjustment factors obtained for pulse-like near-field motions are larger than adjustment factors for non-pulse-like near-field motions.