مقالات رزومه دکتر محمدرضا تابش پور

Owing to the common use of infill walls in conventional buildings, it is a practical and important topic to investigate the effect of infill walls on the behavior of structures during earthquakes. One of the disadvantages of infilled frames is the presence of large window openings in some of the reinforced concrete frame buildings, which results in the short column phenomenon. The part of the column that is adjacent to the wall is almost integrated with the wall and leads to a reduction in the height of the column. Therefore, the lateral stiffness increases considerably. With increasing stiffness, the lateral force applied to the column also increases. In this study, a 4-story, 3-span reinforced concrete model with a different arrangement of infill walls in the stories and considering short walls on the ground floor, the short column phenomenon has been investigated in ETABS software. Also, the seismic capacity of the structure has been calculated by valid methods based on the capacity spectrum method proposed by ATC40. The results indicate that with increasing stiffness, the maximum shear force applied to the column due to the presence of the infill wall under the designed earthquake load will increase by about 50% compared to the frame without the infill wall. Furthermore, the amount of stiffness difference in the frame with and without infill wall in the analyzed models is about 70%, which can prevent irreparable damage by predicting this event and proper design.

Confined masonry buildings, in which all or part of gravity loads and all of lateral loads on both main directions of the building are resisted by unreinforced masonry walls, have been widely used in Mediterranean Europe, Latin America, the Middle East, south Asia, and the Far East. Experiences obtained from past earthquakes and experimental results indicate that confined masonry buildings, if properly built, exhibits an adequate seismic response. Consequently, it represents a good choice in those seismic regions where masonry is widely used due to economical or traditional reasons.In this paper, first, the functions of tie beam and tie column and the similarity of seismic behavior of the confined masonry walls and the filled frame have been studied. The structural response of confined masonry and infilled frames under in-plan lateral loading is similar, despite the different construction techniques. In both cases, structural separation occurs at the initial stage. After this separation, a diagonal compressive stress field is formed in the masonry. In the following, the field study of five masonry buildings after the Sarpol-e Zahab earthquake have been presented. The buildings have been selected in such a way that all types according to the scope of this research have been investigated. These types include: 1. Two-story masonry building with tie-beam, 2. Two-story masonry building with tie beam and tie column, 3. Two-story masonry building with tie beam and tie column in first story and tie beam in second story, 4. One-story masonry building with tie-beam, 5. One-story masonry building with tie beam and tie column. The results of this study show that the seismic behavior of confined masonry buildings in comparison with a lot of severely damaged buildings with steel and reinforced concrete structures, is much more desirable. In the following, the behavior of two main types of two-story masonry building in Sarpol-e Zahab including masonry wall with tie-beam and masonry wall with tie-beam and tie-column is analyzed as finite element models in Abaqus. By using finite element linear analysis, the load path and cracks in the confined masonry walls can be studied with good accuracy. In the condition that there are only tie-beams in the building and gravity load and seismic force are applied to the wall, the maximum stress is formed in the diagonal path in the middle of the first story wall. Consequently, the first cracks will form in the same path when seismic force creates a shear stress more than shear strength of the wall under gravity load. In the condition that there are both tie-beams and tie-columns in the building, in the initial earthquake cycles, when the wall and ties have a good connection and seismic force is applied from left to right, the shear stress at the junction of the left side of the tie-columns to the right side of the walls is maximum and as a result, the walls will separate from the ties in these locations. In the next cycle, in which the direction of the earthquake is from right to left, the shear stress at the junction of the right side of the tie-columns to the left side of the walls is maximum and as a result, the walls will separate from the ties in these locations. These changes in direction of the earthquake will lead to the separation of the walls from the tie-columns in the initial earthquake cycles. Therefore, the behaviour of confined masonry wall will be similar to the infilled frame in subsequent cycles. Accordingly, the maximum shear stress path will be formed in the diagonal of the bays confined by the tie-beams and tie-columns. Consequently, the first cracks in the bearing walls of confined masonry buildings will form in this path. The results of the study show that the failure modes obtained from the finite element analyses are well matched to the actual cases damaged in the Sarpol-e Zahab earthquake.

Immersed boundary method is a novel and efficient tool for solving fluid-structure interaction problems. One of important fluid-structure interaction problems is vortex-induced vibrations of cylinders. In this study, we want to introduce immersed boundary method. Philosophy, advantages, disadvantages and applications of the method will be presented. Because of wide range of applications of this method and for not losing focus, we shall limit our study only to vortex-induced vibrations. Next, details of governing equations of immersed boundary method and their discretization will be introduced. Iterative immersed boundary algorithm which has been used for vortex-induced vibrations before, will be used to solve governing equations. Finally, implementation and coding requirements will be discussed. This paper is organized in a way so readers can obtain a comprehensive understanding of the method behavior in fluid-structure interaction problems, especially vortex-induced vibrations. Considering the benefits of immersed boundary method, it has the potential to become the main method for analyzing fluid-structure interaction problems. These benefits are considerable enough that makes the implementation of the method justifiable.

The Behavior of eccentrically braced frame (EBF) in terms of stiffness and ductility is between moment resisting frame and concentrically braced frame. EBF should be designed in such a way that yielding is only concentrated in the link beam at the non-linear stage. Field survey after the Sarpol-e Zahab earthquake shows that despite several defects in structural design and construction of EBFs, they have remained stable. In this study, one of the damaged buildings in the Sarpol-e Zahab earthquake, in the form of a three-story four-bay frame was modeled in Etabs and its seismic behavior in two cases; with and without infill walls was studied. The results of the analyses show that the presence of diagonal struts of infill walls reduces the axial force of the braces, the shear force, and the bending moment of the link beams. Infill walls also reduce lateral displacement and period of EBF, and they increase the lateral stiffness. Therefore, in the condition that there are several defects in the design and construction of link beams and braces, connecting the infill walls to the structure has a positive achievement. In this condition, if there were not infill walls, there would be a possibility of structural collapse.

Experimental measurements of dynamic instabilities in water environments are challenging due to their fluctuation and small amplitude. Most of studies use electrical circuits, this paper aims to use only mechanical methods to measure vortex induced vibrations. Measuring the fluctuations amplitude can help designing mechanisms for movement and for mechanical energy harvesting. This paper uses the novel particle image velocimetry method. The test comprises of a cylinder moving in water with different velocities. Uniform and tapered cylinders are used. Study of tapered cylinder is unprecedented. Output data is in the form of dimensionless amplitude-velocity graphs. From this test velocity for producing largest amplitude is obtained. It is also seen that in the efficient velocity, amplitude of uniform cylinder is larger. While tapered cylinder is suitable for using in currents with variable velocities.

Recorded earthquakes on near fields have special characteristics different from other usual records. Buildings placed near faults should be designed for the effects of such faults. Because of existing such faults in some cities in Iran such as Tehran and Tabriz, the effect of them should be considered in seismic codes in Iran. In this paper a comparison among various seismic design codes has been carried out almost this effect leads to increase the base shear using a separate coefficient that implies to design spectrum. This coefficient is a combination and a function of distance and period being larger in more near distance and longer periods. This effect has been considered in seismic design codes in some countries such as Taiwan, New Zealand and United States. In this paper a brief review of some seismic design codes and the new version of the Iranian seismic code of practice is presented.

Now a days using catamaran vessel in passenger, military and commercials is increasing.one of the concept design that attracted many researchers is HARTH (high aspect ratio twin hull) vessel. The advantages of this vessel in addition to large deck, this kinds of vessels have good stability and can maintain speeds in harsh seas. However slamming in high waves can create some problems for these kind of vessels. Some different method have used by designers to decrease the impacts of slamming.one of this methods is adding Centre bows in these kind of vessels. Centre bows can decreased the impacts of slamming.one of the more applicable methods to studying the slamming is the drop test.in this research by using this method, we are testing the different Centre bow cross-sections and the acceleration of them are compared. The cross-sections are set in two categories of 1 and 2 from dimensions view.it is recognized that categories 1 have lesser accelerations than categories 2.

Based on numerous studies, using weak and fragile building materials such as traditional brick due to their high weight, low strength, and low ductility during earthquake will cause the most casualties and losses. Observations from past earthquakes indicate that many structures have undergone remarkable damage even in moderate earthquakes. Low ductility and strength, high weight and severe strength degradation under seismic loads are responsible for these buildings failures. In this paper, behavior of a modern reinforced composite gypsum panel is evaluated and compared with corresponding panels made with traditional materials. The cheap and accessible basic materials used for making these panels result in favorable performance including a significant increase in the tensile and compressive strength as well as providing panels with integrity. So that when it breaks down, its particles do not disintegrate. In order to determine the basic mechanical properties of such panels, numerous standard tensile, compressive, and shear tests have been performed on various panel specimens at the materials laboratory of the faculty of mechanical engineering, Sharif University of Technology. Considerable ductility, strength, energy dissipation capacity, minimum cost, and fast construction are among the features of the proposed panel. Applying the finite element simulation, the buckling force of these composite gypsum panels were determined, which shows high buckling capacity. Subsequently, parametric studies were performed to evaluate the effects of openings on the behavior of these panels as load-bearing walls. The results of experimental tests for this type of panel presented that tensile strength is 4.3 Kg/Cm2 and compressive strength of panel is 18 Kg/Cm2, which are more considerable in comparison with the other traditional masonry materials.

Inverse problem for spring-mass systems called shear structures is presented in this paper. Shear structure is a system with spring and mass after each other and there is a spring between two masses. Damping effects are neglected here. The aim is determining the mass and stiffness of the system with pre assigned frequencies. There is a method for solving such a problem that is presented here. Some examples are discussed. Such a problem can be used for several important problems.