Ali Bagherkhani

Derivation of Trilinear Spring Models for Typical Regular and Irregular Multi-Story Reinforced Concrete Structures

   Abstract   The Beyglar Beygi Mansion is a historically significant structure from the Qajar era. It was constructed in 1276 AH (1859 AD) in the Feyzabad neighborhood of Kermanshah. Between 1311 and 1315 AH (1893-1897 AD), the mansion underwent expansions, during which the Takyeh was added to the original structure. In 1326 AH (1908 AD), intricate plasterwork and mirror decorations were incorporated. Today, the mansion serves as the Museum of Calligraphy and the Zagros Paleolithic Museum. Recent seismic events in Kermanshah province, especially the Sarpol-e-Zahab earthquake on November 21, 2017, have highlighted the need for a comprehensive seismic assessment of this historic monument. This study aims to evaluate the seismic response of the Beyglar Beygi Mansion and Takyeh under design-level earthquake conditions. A finite element model of the structure was developed using ABAQUS software, which incorporated validated material properties and geometric characteristics based on frequency analyses and historical documentation. The results indicate that the numerical model accurately represents the existing structural conditions. The findings reveal that the structure maintains stability under gravity loads, despite localized weaknesses in the masonry piers and brick components. Additionally, dynamic time-history analyses were conducted using acceleration time history records from the 2017 Sarpol-e-Zahab earthquake in Kermanshah. The modelled damage patterns were compared with observed structural damage to validate the analytical results. Seismic behavior was analyzed using one scaled ground motions that represented the design of the earthquake. The results highlight that the western and northern facades are particularly susceptible to seismic loads, with maximum displacements of up to 70 mm observed in these regions. Such vulnerabilities could lead to localized failure and progressive damage accumulation during future seismic events. Ultimately, this study identifies the critical weak points and seismic response characteristics of the Beyglar Beygi Mansion and Tekyeh, providing valuable insights for future conservation and retrofitting strategies. Keywords: Beyglar Beygi Mansion and Takyeh, Historical Structures, Nonlinear Dynamic Analysis, Seismic Vulnerability, Kermanshah.

   The tra  ortation industry‌is one of the fundamental industries in human societies that has undergone many changes from the past to the present. This industry is of such great importance that its absence can cause many problems in life. Therefore, with the advancement of science and technology, the structural complexity of this industry has increased day by day.Cars are among the vehicles in this industry that have the most users, so that over time their complexity, diversity, and number have increased. Despite the widespread use of cars, we should not be unaware of their disadvantages and vulnerability. Accidents are one of the most important causes of death in the world, always claiming many victims. In fact, during an accident, a lot of energy is released as a result of the collision of cars with each other, which causes damage and injury to the occupants of the car by transferring this energy to them. If the collision speed is higher, the consequences will be more fatal.Therefore, the importance of vehicle safety in the field of accidents is not hidden from anyone, and for this reason, it is necessary for engineers and researchers in this field to focus their attention on this issue and try to solve this problem. A lot of research and experimental work has been done in this field, which has ultimately led to the introduction of energy-absorbing structures. Energy absorbers are actually structures that are installed in the front of vehicles and absorb the kinetic energy of the collision during an accident by changing their plastic shape and preventing it from being transferred to the passengers. The use of this type of structure is not limited to the field of automobiles, and these structures can be used wherever there is a need to absorb irreversible energy.In this study, the sandwich panel structure was investigated as an energy absorber. In fact, the sandwich panel structure consists of two composite shells with carbon fibers in 7 cylindrical layers and corrugated aluminum cores. In this research, corrugated cores in eight states were used, whose cross-sectional area is a function of a sinusoidal relationship and changes according to the amplitude and number of waves created. The composite shells and corrugated cores were simulated in the Abaqus finite element software and after assembling them together and forming the sandwich panel, they were placed between two rigid plates, one of which is fixed and the other with a mass of 100 kg and a speed of 20 m/s hits the sandwich panel, causing the axial collapse of the sandwich panel. By obtaining the force-displacement diagram resulting from the collapse of the sandwich panel for each of the eight core states mentioned, the amount of energy absorbed and other indicators of the impact resistance of the sandwich panel, including the initial peak crushing force (IPCF), the average force (MCF), crushing force efficiency (CFE), and specific energy absorption (SEA). To validate the materials and simulations performed in this study, existing experimental and numerical research in this field was used. According to the results obtained from the simulation process of low-velocity impact on sandwich panels for different corrugated cores (eight states), it can be concluded that by increasing the number of waves and the amplitude of the cross-sectional area function of corrugated cores, the amount of energy absorbed and the impact capability evaluation indices also increase, so that among the eight states of the aluminum corrugated core, the core with amplitude A = 2.5 mm and wave number N = 10 has the highest energy absorbed and the highest values ??of the impact capability evaluation indices compared to other corrugated cores.

In this numerical study, heat transfer and fluid flow in circular microchannels with porous and solid ribs were investigated. Water was used as the cooling fluid. A total of 23 circular ribs were analyzed across 8 porous and 6 solid cases in the microchannel. The rib volumes were kept constant across all cases, and in each case, increasing the inner diameter resulted in increased rib thickness. Due to the small size of the channel, laminar flow was used to avoid excessive pressure drop, with the Reynolds number ranging from 100 to 800. The Darcy–Brinkman–Forchheimer equations were applied to simulate the porous regions. The Nusselt number, pressure drop, and figure of merit (FOM) were calculated for all cases and compared. For the same inner diameter, solid ribs exhibited a higher pressure drop. The first solid case achieved the highest heat transfer among all cases. For the same inner diameter, porous cases demonstrated better FOM, with the first porous case having the highest FOM. This case was identified as optimal, as it provided satisfactory heat transfer without imposing excessive pressure drop on the system. The effects of porosity, permeability, and Al?O? nanofluid concentration were analyzed for the optimal case. Both solid and porous ribs improved the FOM compared to a ribless channel. For systems where both heat transfer and pressure drop are critical, porous ribs are a suitable choice. For systems where pressure drop is of greater concern, porous ribs are preferable. The third, fourth, and fifth solid cases, as well as the sixth, seventh, and eighth porous cases are recommended for systems prioritizing heat transfer performance.