آرش محمدی فارسانی

Although steel plate shear walls have been used to resist lateral loads in recent decades, its complex behavior has brought about difficulties in employing this system. In this study, the lateral behavior of unstiffened steel plate shear walls is investigated via nonlinear static analysis (i.e., pushover analysis). Three different special steel moment frames having 1, 5, and 10 stories are designed based on the codes criteria. Then, the finite element models incorporating both the plastic behavior of steel material and large displacement of the steel plate due to buckling are developed as exact models. In addition, simplified equivalent strip models are created as a more practical code-based approach to modeling for comparison against the exact method. The effects of different parameters including applying gravitational loads, the lateral loads distribution pattern, modeling technique, and rectangular opening in shear wall panel are evaluated. Results of the analyses show that in monotonic loading, results of the strip model are consistent with those of the more rigorous finite element model; of note, results of the former were achieved faster than the latter. Also, it is observed that use of the design method promoted by the design code results in the formation of plastic hinges first on the columns rather than walls. When the wall contains rectangular openings, it is shown that they must be accompanied with perimeter stiffeners on the edges of the opening. Otherwise, a large stress concentration would occur at the corners of the opening. Even with the peripheral stiffeners, the presence of an opening reduces the lateral stiffness and strength of the wall system more or less linearly with regard to variation in the opening size. Eventually, semi-analytical relations are proposed to estimate the lateral stiffness and strength reduction due to the presence of an opening.

The present paper focused on experimental and analytical study for evaluating the behavior of three-dimensional welded steel moment connection of I beam to box column under constant axial load on the column, cyclic loading in one direction and constant gravity load on the other orthogonal direction of the connection. Box columns are suitable sections for bearing loads on buildings because they have the same geometrical properties in two directions due to the symmetry around the two orthogonal axes and on the other hand they facilitate the joining of the orthogonal beams. However, due to the lack of easy access to the inside of the box sections and the need to use continuity plates or stiffeners that can perform the duty of continuity plates, the relevant solutions under different conditions and proper understanding of the behavior of connection components are still under investigation. In this research, first four specimens, including two internal and two external three-dimensional joints, are made and tested. The internal specimens consist of a cold-formed steel box column (HSS) and connected beams from four sides with the external diaphragm, and the other one with a built-up steel column and inner diaphragm. The external specimens are also the same as the internal samples include two types of inner and two types of the outer diaphragm. In all joints with the outer diaphragm, the steel cover plate connected to the column as a collar by groove welding and the web of beams by fillet welding. Then after, based on the experimental results, analytical finite element models are developed using ABAQUS software and the effect of three parameters such as the axial load of the column, the column steel plate thickness, and the thickness of cover plates on the behavior of internal joints with external diaphragm are studied analytically. Generally, experimental results of all specimens showed that the seismic behavior of samples with the external diaphragm is more close to the other one with the inner diaphragm and the failure mode followed by occurring plastic hinge in the beam precisely at the end of cover plate. However, there is a little bit different due to the experience of smaller strains than the yield limit of the panel zone in the internal joint specimen with the outer diaphragm compared to the inner diaphragm. The results extracted from the nonlinear analysis also illustrated suitable accuracy with the experimental results. Each of the parameters mentioned above could change the failure mode and ductility of the connection system‏. In other words, increasing the ratio of the axial load to the nominal capacity of the column to the value of 0.42, the failure mode transfers from beam to the column despite the growing of ratio of energy dissipation. Meanwhile, for the column bearing load ratio more than 0.58, global buckling of the column and brittle failure will happen. Moreover, by decreasing the plate thickness of the column less than 15 mm, the failure mode transfers from beam to column and the energy dissipation of the specimens reduces. Also, for cover plates, less than 20 mm thick, the mode of failure will take place in the column. However, if higher strength is used for both cover plates and plate thickness of the column, the lower thickness of the cover plate will be required in order to create the failure mechanism in the beam.

The corroded reinforcement bars are the important issue of the concrete permanence due to reduction of the safety factor of the structure against the applied external loads. Corrosion of steel reinforcement has a complex process which due to the reduction in the resistance crass sectional area of the reinforced bars and degradation of concrete structure. Therefore, there are more important that the reinforced concrete structures are evaluated under corrosion at service loads due to an optimum and robust design to achieve a good durability and assessed the time-life service. The reinforced concrete beams are a one of most component that implemented for constructing the reinforced concrete. In the period-times the corrosion, the concrete beams have variety uncertainties such as model uncertainty, load and resistance uncertainty. These uncertainties can be considered using a probabilistic model based on the basis of random variables. The random variables in probabilistic models can be given by several statistical characteristics including probability density functions and their parameters (e.g. mean and standard deviation). The various methods including the first-order reliability method (FORM) and the second-order reliability method (SORM) methods, simulation approach and surrogate-based modeling are used to evaluate the probabilistic model in reliability analysis [1]. The Monte Carlo simulation (MCS) is widely used in reliability analysis due to simplicity and more accurately.

Hammers or presses commonly used in modern manufacturing facilities produce remarkable vibrations during their operation. Foundations supporting these machines experience powerful dynamic effects which may extend to the surrounding areas and affect workers, sensitive machines within the same facility, or the neighboring residential areas. To control free-field impact-induced vibrations, wave barriers may be constructed in the vicinity of the vibration source. This paper examines the efficiency of soft barriers (open trenches) on screening pulse-induced waves for foundations resting on a deep elastic layer or a layer of limited thickness underlain by rigid bedrock. The effectiveness of open trenches as wave barriers is examined for different cases of soil layer depth, arrangement for double trenches, and trench location.A 2D finite element model is constructed and some parametric analyses are performed in the time domain. Different arrangements of wave barriers in vibration isolation for shock-producing equipment are assessed for their efficiency. The results show that using the second trench could remarkably reduce the vibration amplitude. Finally, some guidelines are defined for their use.