نشریه آنالیز سازه - زلزله
سال نوزدهم شماره 4 (زمستان 1401)

In this research, firstly, three mix designs of alkali-activated concrete containing 92, 96, and 100% blast furnace slag and 8, 4, and 0% nano-silica were made. After performing the compressive strength and modulus of elasticity tests and choosing one design as the optimal design in terms of superior mechanical properties, by adding 1 and 2% polyolefin fibers to the optimal design, two more designs of alkali-activated concrete were made. All concrete samples were subjected to compressive strength and modulus of elasticity, XRF and SEM tests. The results of the tests exhibited superiority in mechanical and microstructural properties of the alkali-activated concrete compared to normal concrete at all processing ages. At the processing age of 90 days (as the best age in performance due to the progress of the chemical process), following the compressive strength test, the lowest (49.94 MPa) and the highest (66.36 MPa) compressive strength values ​​were obtained, respectively, for design 1 including Normal concrete and design 4 including alkai-activated concrete containing 8% nanosilica. At the same processing age, the lowest (32.44 GPa) and the highest (42.51 GPa) modulus of elasticity were achieved in design 1 and 6 of the alkali-activated concrete containing 8% nano-silica and 2% polyolefin fibers, respectively. At this age, addition of 8% nano-silica and 2% fibers in the alkali-activated concrete of design 6 resulted in a decrease of 22.49% in the compressive strength and an improvement of 7.05% in the modulus of elasticity.

In the present research, design of a strong and online adaptive controller in the active cable control system is discussed to overcome the earthquake vibrations of multi-story buildings. Considering all variables as unknown, this study introduces a new type 2 adaptive neuro-fuzzy controller. Using the MLP neural network (multi-layer perceptrons), Jacobian and the structural system estimation are extracted. This estimated structural system model is implemented into the online controller system in the next step. Adaptive controllers are tuned using a post-propagation algorithm and Extended Kalman Filter and are thus able to control and tune the controllers and the cable system. In this method, a PID controller is also used, which increases the strength and stability of the adaptive neural-fuzzy controller system two against earthquake vibrations. The superiority of the proposed controller system over an online simple adaptive controller is also demonstrated. This controller is utilized as an implicit reference model. In this proposed method, Extended Kalman Filter is innovatively used to tune online controllers. In this research, the performance of both controllers is investigated under the far and near fault field pressures. Based on the numerical results, the adaptive neural-fuzzy controller performs about 21% better than the online simple adaptive controller in minimizing the seismic responses of the structure during an earthquake and reaching the control criteria when the parametric characteristics of the structure change.

Zipper bracing system is one of these types of braces. The zipper bracing members transfer the unbalanced tensile forces created in a floor to its upper floor, and this process continues until there is an increase in lateral load and causes the braces of the higher floors to buckle. In this article, the dynamic behavior of the braced structure with zipper under the influence of earthquake records with rocking component and without rocking movement has been studied. SAP2000 software was used for modeling. Seven accelerometer pairs have been utilized for nonlinear dynamic analysis. The studied frames are 6-, 9- and 12- floors with a floor height of 3 meters. In all the studied models, the joint in the bracing part has been damaged. In this part, most of the damages have been at the level of continuous usability, and in the 9- and 12-story structures, the damage is a little wider and at the level of life safety performance. In the structures where rocking movement has been applied in the foundation part, it has caused the movement and shearing of the foundation of the structure to be reduced by 20 to 35 percent because it absorbs some of the earthquake force. Examining the results related to the displacement of the roof of the structure, it has been observed that the displacement of the roof in the structure with CBF bracing was about 10 to 25% less than the structure with zipper bracing.

In the present research, the seismic fragility and collapse capacity of concrete moment frames have been investigated by considering different ratios for the weak beam-strong column rule in the optimization process in the performance-based design framework. In order to implement performance-based optimization, the center of mass metaheuristic algorithm has been applied in this research. The philosophy of design approach based on performance and even traditional design methods allows the structure to suffer damage facing strong and relatively strong earthquakes. Therefore, in order to estimate the level of safety of the structure against earthquakes, it seems necessary to use quantitative indicators of seismic safety and the collapse capacity of the structure. In order to predict the collapse capacity of each optimal structure, using incremental dynamic analysis, the modified collapse safety margin ratio under far and near fault earthquakes has been calculated. Two examples, 3-span three and six floor frames have been studied in this research, which are designed in the performance-based optimization framework and considering the coefficients of 0.8, 1.2 and 1.6 to control the weak beam-strong column rule in the optimization process. The results indicate that increasing the rigidity of the column compared to the beam in this research actually affects the ductility of the structure, and by choosing structures with greater rigidity of the column compared to the beam, it leads to an increase in the collapse capacity and a decrease in the fragility of the structure.

Adopting risk management is a must, inevitable in all construction projects. Risk management is very important in retrofitting of the projects. Strengthening the reinforced concrete beams with respect to their type and how they are made is assessed in this study. Although both of the near-surface mounted (NSM) and externally bonded reinforcement (EBR) methods have advantages and disadvantages and it depends on the reinforced member and the project conditions, but in general, the NSM method outperforms the EBR while somehow (EBR) is adopted more. A researcher-designed questionnaire consists of ten restrictive factors regarding NSM implementation. The responding persons consist of skilled experts with at least five years of experience in this field. The execution of risk management in NSM, obstacles on the way of implementation, and the effect of risk management on the functionality of these factors are of concern here. The obtained data is assessed through statistical tests. The factors of more execution time, lack of experts, high volume, low knowledge on the client, uninformed employers, consultants and contractors about the existence of this method, complexities in the calculation, big calculating mass, concrete cover 5-7 cm, FRP rebar needed in NSM, high implementation cost and high FRP implementation cost are considered as the restrictive factors affecting NSM implementation. The initial assumption that the ten factors were restrictive as to NSM implementation led to proving that the factor of lack of information about this method within the client, contractor, and consultant was the most effective as a restriction. This proof was obtained through the statistical tests conducted on the assumptions.

The effect of topography on the seismic response of structures, owing to the construction of adjacent buildings, has been a challenging issue in recent decades. In this study, while considering the behavioral characteristics of the soil, the effect of topographic slope and height on the seismic response of the structures in their vicinity has been investigated. and the effect of earthquakes with different frequency content on the response of structures up and down the slope has been evaluated. Also, the effect of earthquakes with different frequency content on the response of the structures at the top and down the slope was evaluated. At the end, the effect of soil flexibility on the response of structures adjacent to the slope was investigated. Considering the soil-structure interaction in soft soils can increase the maximum displacement to about 100% of the initial value, but it reduces the maximum base shear to approximately 10% of the initial value. Consequently, the analysis with topographical interaction strongly affects the answers. The change of response with the change of the earthquake record is sometimes observed up to 40% in the results. Therefore, for correct interpretation, full dynamic analyses should be based and the maximum value alone cannot be relied upon in the analysis of soil topographies

Earthquake is considered as one of the most destructive phenomena and natural hazards, which has become very important due to the increase in the growth and development of cities and the concentration of capital. Earthquakes, in addition to the acceleration caused by the passage of the wave, also carry the risk of earth rupture. The experience of destructive earthquakes indicates that the structures located in the boundaries of the earthquake fault suffered the most damage when the earthquake occurred. The maximum acceleration of ground movement can be calculated and its damages can be controlled by engineering measures, but it is difficult to control large displacements and prevent its transfer to the structure in the seismic fault zone. In the fourth edition of the 2800 Code, based on the study of the zoning committee of this Code, more than 300 main and large faults have been mapped for the territory of Iran, and in addition to that, there are other hidden faults that need to be accurately identified and located by more detailed studies. An important point in the seismicity of Iran, in addition to the relatively low depth of the earthquakes, is the adaptation of the hypocenters of the earthquakes to the location of the population centers. The method of evaluating and estimating damages caused by earthquakes is an important tool for dealing with earthquakes and also estimating building insurance. The present research is a review study in which the evaluation of the researches conducted from 1998 to 2023 related to the economic damages of urban constructions in the fault zones has been done. Among the many quantitative and qualitative methods, five effective methods for estimating and evaluating the economic damages of earthquakes are analyzed in order to predict the crisis and timely management of the crisis during the occurrence of the earthquake in the constructions located on the fault zones. Considering the issue that the geometrical characteristics of the faults and the engineering boundaries of the faults in each fault zone are specific to that area, therefore, in order to predict and accurately estimate the economic losses, it is suggested to implement a combination of the proposed methods.