نشریه سازه و فولاد
سال چهاردهم شماره 27 (بهار 1399)

Reinforced concrete shear walls have a high out-of-plane stiffness, while the steel shear walls have a slight out-of-plane stiffness. To prevent the buckling, the steel plates are connected to the concrete panel by shear lugs (composite shear walls). In this paper, the behavior of coupled composite shear walls is investigated. The results show that the stresses created in the system of coupled shear walls are reduced in comparison to separate shear walls and that lateral stiffness is increased. However, increasing rigidity of coupled beams more than a specified amount does not significantly affect the elastic behavior of the system. Therefore, a relation that can approximate the the ideal coupled beam is suggested. A dual system of steel moment-resisting frame and composite shear walls was designed, and static nonlinear analysis was performed. In the following, the composite shear walls are assumed to be unchanged, and the dimensions of the coupled beam are calculated by the proposed relationship and static nonlinear analysis has been performed. Comparison of the results shows that the resistance and seismic parameters of the coupled shear walls are more than separate shear walls. The studies show that increasing the rigidity of the coupled beams more than that of the ideal beams does not have a significant effect on the increase of the resistance parameters of the system and, moreover, the ductility of the system decreases. Therefore, the dimensions of the ideal coupled beam cross section are predicted well even in the nonlinear performance of the system.

In the analysis and design of steel frames, there are various factors that the uncertainty of each of them can have a significant effect on structural safety. Hence, the investigation and recognition of these factors is important for understanding the true behavior of the structure. In the meantime, the stiffness beam-to-column connection can be considered as one of the factors due to uncertainties such as how to construct, execute, install and model the parts and joints steel structures. The effect of semi-rigid joint on structural analysis not only changes the moment distribution along the beams and columns, but also increases the frame's displacement due to second-order effects. Therefore, in most advanced specifications, it is allowed to consider semi-rigid joints behavior. Hence, in this paper, first, the effect of stiffness of the connections in the plastic analysis based on plastic hinge will be studied in two steel frames. In the following, by randomly assuming the stiffness of rotation of beam to column and stiffness of column joints to the support and plastic moment of members and joints, and considering several probability distribution with different coefficients of variant, the behavior of the structure in the probabilistic plastic analysis can be investigated. Accordingly, the Monte-Carlo simulation is used to estimate the probability of failure of semi-rigid steel frames. On this Basis, each frame is simulated 840000 times and the load failure capacity on the structure is available. It should be added, the OpenSees software was used to deterministic and probabilistic analysis. The results showed that the rotational stiffness of the joints and restraints and plastic moment of members had a significant effect on the responses of deterministic and probabilistic analysis.

The capability to repair structures after an earthquake by replacing several members can be very economical and practical. In critical situations after the huge earthquakes is so helpful that structures can be repaired and rebuilt while being resistant to the next earthquake. The linked column is an idea of lateral resisting system which creates the ability to repair structures after an earthquake with replacing several members. In previous research, the linked column frame System (LCF) has been evaluated, the results have been shown that this system provides its design purposes. In this research, behavior of linked column with simple frame (LCS) will be evaluated, for this purpose 3, 6 and 9 story models of linked column with simple frame are designed and their behavior has been evaluated using nonlinear static pushover and nonlinear dynamic time history analysis. Based on the results, mean value of maximum interstory drift of models under the 14 ground motion records that scaled to the base design earthquake, is below 2 percent and this system has the capability of structural stability against the earthquake records. The plastic hinges spreading and beginning in nonlinear analysis shows that LCS system has the capability of creation design purposes. Thus, in preliminary evaluation of linked column with simple frame is introduced as a new structural steel frame system that provide fast repair structures after an earthquake.

The purpose of this study is to determine the ratio of the demand to capacity in knee element in the bracing system called Chevron's knee bracing. The overall idea is that the design is to be carried out so that only the knee element is yielding in the severe earthquakes, and the other members remain resilient, or the number of plastic hinges in the beams and columns, and the buckling of the braces, is significantly reduced. In this study, two models of bending and shear elements with 2, 6 and 10 floors and two types of 2 and 4 bays are considered. In the bending mode, the BOX section and in shear mode the IPE sections are used. In this study, the behavior of the structure and the process of forming plastic hinges in frames with design state that the ratio of the demand to capacity smaller than one and state that the ratio of the demand to capacity larger than one has been investigated. The yielding of elements in the nonlinear static analysis is in accordance with what was expected. Knee Elements Before the buckling braces in each story were yielded in all models examined. Hence, it can be guessed that the design of knee element, according to 120 - 140 percent of their elastic capacity, is an appropriate strategy to ensure that the knee elements are the first elements that help to the structure to energy dissipated by forming Plastic hinges.

In this paper effects of the placement of various stiffeners and opening on the interaction behavior of steel plate shear walls and precast concrete frame, has been investigated. Steel plate shear walls has been bolted to concrete frame, by use of embedded plate in boundary concrete elements. Push over and dynamic analysis under seven earthquake acceleration in ABAQUS software, was done.
The results showed that the proposed connection, by keeping up its stability and strength, showed appropriate function in the route of load bearing of shear wall. Also it was observed that adding steel plate shear wall to concrete frame increased initial stiffness, base shear and dissipated energy 4, 4.3 and 340 times, respectively. The sample with opening in diagonal line and horizontal and vertical stiffeners, had maximum dissipated energy (22% increased). This sample showed the maximum relative displacement (increased 2 times) and minimum base shear force (decreased by 10%). Adding horizontal and vertical stiffeners to simple sample, increased dissipated energy by 16% while, the sample with diagonal stiffeners decreased dissipated energy by 25%. This model showed the minimum relative displacement (decreased by 15%) and maximum base shear force (increased by 7%). Placing the opening at the middle of sides in this model, increased dissipated energy by 35%.

In this paper, we investigate the seismic performance of concrete dome filled concrete columns with prism geometry. For this purpose, a number of pillars with a square core, rhomboid, circular, and prism external geometry with a square cross-section that was raised with a 2.5 degree gradient from above up was made. All columns were loaded under the ATC-24 loading protocol and loaded until the rupture of the column continued. The results show that despite the collapse of the columns with the inner section of the square and the rhizosphere, the columns with the inner section of the circle have less damaging effects and rupture more than the columns with the internal section of the square and the rhombus. Also, the rupture pattern of the pillars after 20 cycles has been expanded in diameter belts with a 45 degree angle. The initial hardness and coefficient of ductility of the columns with the interior of the rhizome is about 2 times greater than the other columns. Another point is that due to the softer breakdown of the column with the inner section of the circle than the other columns, its energy loss has not suddenly been.