BULLETIN OF EARTHQUAKE SCIENCE AND ENGINEERING
Year:2018 | Volume:15 | Issue:2|Papers Count:7

The use of concrete in combination with steel in structures can play an important role in improving the structural behavior, ie increase in strength and formability. In many cases, in steel structures that do not meet the considerably shaping criteria. In this study, a solid concrete beam and steady steel beams were modeled using ABAQUS finite element software and verified by a laboratory model. In the following six groups, the difference in specimens was only in the manner of connecting concrete to steel, and for each of the six series, five different thicknesses were considered and investigated, which resulted in the following conclusions. Increasing the number of cutters increases the resistance of composite beams. By increasing the number of simple cut-offs into two rows, 10% of the final bending strength of the composite beams increases. The difference between the studs and the corners is not significantly different. The effect of simple cut-offs and L shapes has been around 2%.

The steel braced frame system is one of the lateral load resisting systems which is used extensively for low-to mid-rise buildings. In this structural system, the braces can be arranged in different forms along the building height due to different reasons such as architectural and structural limitations or design considerations. The bracing arrangement affects the seismic performance of the structural system and each of the elements. In this study, the impact of bracing arrangement along the building height on ultimate failure capacity and collapse fragility curves of steel CBFs is investigated. For this purpose, 4 and 8-story steel CBF buildings with 6 different arrangements of braces were selected and modeled in PERFORM-3D software. The models were then analyzed using the incremental dynamic analysis (IDA) method. Afterwards, the collapse capacity of the models and the uncertainty index were calculated, and the collapse fragility curves were generated. The results show that, by modifying the arrangement of braces without significant changes in lateral stiffness and fundamental period of structure, it is possible to increase the collapse spectral acceleration and decrease the probability of collapse at the maximum considered earthquake intensity.

With increasing research on the operation of the shear walls of the steel walls and increasing the reliability of their operation, the use of these walls has been noticeably expanded, especially in the United States and Japan. Given the relatively comprehensive understanding of the behavior of these walls, design rules have now begun to provide design rules for these walls. The basis of the performance of these structures is based on the operation of the diagonal tensile field after the buckling of the steel plate. Simple implementation is based on the technical advantages of the system without the need to acquire new skills, reduce the dimensions of the foundation, increase the perceptibility of the lateral structure of the structure, reduce the dead load, and, in the meantime, the economy of this system in counteracting the steel frame framing system is considered as the main advantages of this system. Gets The steel shear wall is a new side-impact resistant system that has better performance than other side-impact resistant systems. Considering the importance of using such structures, there is a need for study in this field. In this study, prior to examining the performance of joint wall joints, to verify the numerical results, we verified the laboratory sample and after evaluating and assuring the results of the modeling, 12 steel wall panels with Abaqus software were used. In these samples, parameters such as wall thickness, geometric characteristics of beams and columns, and the degree of opening of the corners of the sheet are investigated. The results of this study showed that with increasing the cross-section of the columns, the stress distribution was uniformly distributed on the surface of the sheet and the entire surface of the sheet buckling to the outside of the sheet, while in the case of an increase in the cross section of the buckler, It is visible on the sheets. However, in the event of an increase in the thickness of the wall plate, the amount of non-elastic strain created is less and is approximately limited to the lower parts of the first sheet. With a 20% increase in wall thickness, the bearing capacity and hardness of the samples increased by an average of 18%, and by increasing the opening rate, from 5 to 15% of the bearing capacity decreased by about 20%, and the amount of strain of plastic in the form of a diameter in the sheets It is visible at the site of the sheet attachment to the perimeter bore in the portions of the columns.

In recent years, considering vertical movement in structures, which is known as self-centering motion, is one of the methods used to dissipate the earthquake energy. In this study, 4-, 8-, and 12-Story steel structures with special concentrically braced frame (SCBFs) and eccentrically braced frames (SEBFs) were considered in order to investigate the effect of selfcentering motion under seven near-field earthquakes using Sap 2000 software. The results of this research indicate that considering the self-centering motion, the behavior of structures are changing in SCBFs and SEBFs. In, 4-, 8-, and 12-Story SEBFs structures with considering the self-centering motion, the column and bracing forces were increased which this was different with SCBFs structures. Considering the self-centering motion, more plastic joints are formed in the beams. Therefore, in the self-centering of the columns, the beams outside the bay are more affected. In general, the results indicate that the self-centering motion is better in the SCBFs.

Diagrid structure is diagonal elements that simultaneously carry the load of horizontal and vertical loads. In diagrid structures, unlike most common systems of high-rise buildings in which incoming loads are transmitted through shear and flexural mechanisms, the diagrid structures, due to their triangular configuration and removal of vertical columns, have a central load transfer mechanism, in other words, they have truss performance. Diagrid structures are developed for effectiveness and beauty of architecture and structure. Diagrid structures as a structural system in high-rise buildings in terms of performance, is an improved system of frame and pipe structure, which reduces the structural weight by decreasing the shear lag. The goal of this research is to optimize the diameter structure of buildings to minimize the weight of the structure, to determine the number of horizontal and vertical segments. Grasshopper graphical programming plugin for Rhino software, with parameterization of the written program, provides algorithm optimization. Optimization in the program written by the genetic algorithm is done through the Galapagos plugin based on the outcomes of the structure analysis engine of the Karamba plugin. The simulation results indicate that for a 40-store diameter structure of 900 square meters in each floor, the optimal mode with the horizontal and vertical divisions of 8, and 26, and the angle of 64 with the horizontal axis will be 21508 tons of the total structure.

Considering that the weight of the structure increases the forces involved, especially the lateral forces such as earthquakes, so for this reason, as far as we can take the building path, we have been able to withstand earthquake resistance to the structure. Since, one of the commonly used methods for producing the light eight concrete, utilizes the light weight aggregates with significant role in the concrete strength, proposing the optimized mix-design for the light weight concrete appears to be important. The result of experiments on 140 samples are representative of achieving to structural lightweight concrete according to ASTM C330 Standard which limits the specific gravity of structural light weight concrete to 1850 kg/cm3 and limits the minimum compressive strength of structural lightweight concreteto170 kg/cm3. Specific gravity and compressive strength of samples could be reached to defined limitation according to ASTM C330 Standard by using the very little particles of pozzolans and by changing in mix design.

In this paper, a 15-story steel building was designed based on Iranian code No. 2800 in order to study the effects of rocking systems on the seismic response of high-rise steel buildings. The selected accelerograms were related to the Chi Chi, Landers, Loma Prieta, Northridge, Parkfield, San Fernando and Tabas earthquakes which were selected and scaled according to Iranian Standard No. 2800. These accelerograms were related to the stations which were registered at the distance of 20 to 60 kilometers from the fault and did not have the near-fault earthquakes characteristics such as forward directivity and fling step and etc. Furthermore, the magnitude of all the selected earthquakes was between 6. 5 and 7. 5 Richter. Then, nonlinear time history analysis was used to investigate and compare the seismic response of the studied building in cases with and without using the rocking system. The results of studies (including base shear, drift, displacement of roof, acceleration of roof and etc. ) indicated that using roc king system in the high-rise steel buildings could cause significantly reduce the seismic response of high-rise steel buildings.