Buckling-restrained braces are able to provide significant energy dissipation along with large ductile capacity through their excellent hysteretic behavior. However, due to their lack of recentering capability, buckling-restrained braced frames experience large residual drifts following a strong earthquake, leading to enormous repair costs. To overcome this shortcoming, super-elastic shape memory alloy braces with excellent recentering capacity have been introduced as a viable alternative to steel braces. Nevertheless, their energy dissipation capacity is usually low for seismic applications. This article proposes a robust self-centering energy-dissipative brace to be used in structural frames. The brace is capable of providing adequate energy dissipation capacity in the structure while simultaneously bringing the structure to its original configuration after the earthquake.
Use of composite steel shear walls (CSSW) in earthquake-resistant structures has grown in recent years. However, no thorough information exists on their performance, especially in cases where openings are present. In the present study, in order to first validate the analysis method, ABAQUS was used to model the studied composite shear wall with gap at UC-Berkeley, according to the results of which, a good agreement between the experimental and analytical models was observed. Then, the effect of the position and number of the openings on the performance of the walls was addressed. To this end, models with various openings, including openings close to the beam/column, horizontal/vertical openings and distributing opening, were prepared and analyzed. The results indicate that the maximum reduction in stiffness and strength occurred in walls with single openings. The size of opening and the opening’s area significantly affect shear wall performance. Ultimately, artificial neural network and fitness function tools were employed to obtain predictive models for shear wall performance. A neural network has proven an appropriate alternative method for predicting the displacement, stress, and strength of the composite shear wall.
The primary objective of this research was to study the transmission of gamma radiation from heavyweight concrete containing barite aggregates. For this purpose, cylindrical and cubic specimens were produced for 10 mix designs. The mix designs containing different percentages of barite aggregates were calculated; five mix designs were also calculated for the compressive strength of 25 MPa, while five of them were designed for the compressive strength of 35 MPa to study the influence of the compressive strength rate on the reduction in gamma radiation transmission. The results indicated that both compressive and tensile strength was decreased by increasing the ratio of barite aggregates. The rate in reduction of compressive strength and especially tensile strength in concrete C35 was less than in concrete C25. The use of barite aggregates increased the attenuation coefficient of concrete. The attenuation coefficient in C35 concrete increased more than that in C25 upon increasing the amount of barite aggregate. By increasing the thickness of concrete with different percentages of barite, the rate of radiation loss in different samples was closer. The difference in the rate of radiation loss at a thickness of 150 mm was not much different from that at a thickness of 100 mm, whereas it was considerably decreased at a thickness of 300 mm. The test results indicated that the reduction in the gamma transmission rate is significantly dependent on the density of concrete.
This study aimed to apply sandwich panel in a two-story steel building to improve its behavior. Sandwich concrete panels consist of three basic components including wires, insulating layer and concrete cover. This research studied the behavior of sandwich panels by changing the Young's modulus of the concrete with Finite Element Method and evaluated the displacement, acceleration, and panel stresses. According to the results, increasing the Young's modulus of the concrete, the frame seismic behavior was improved. Using sandwich panels instead of conventional brick increased the building resistance against seismic load while decreasing the structure drift and acceleration. Increasing the Young's modulus of the shotcrete layer enhanced the behavior of the seismic panel. In addition, the results showed that the two-story building, which comprised of sandwich panels, had an appropriate performance against the seismic load. Ultimately, ANFIS was used to predict the response of the building under seismic loads. The effects of some variables such as Young's modulus of concrete, variations on the elevation and panel's number on displacement and acceleration have been presented.
As one of the most widely used materials in different structures, concrete is a material evaluated and categorized based on compressive strength criterion. In addition, national and international codes (INBC- part 9) and standards determine the tensile strength of concrete based on its compressive strength. The purpose of this research is to determine the relationship between compressive strength and tensile strength of C20, C30 and C40 grades. In this laboratory research, a total of 42 cubic specimens of 150 × 150 × 150 mm and 42 cylindrical specimens of 300 × 150 mm were assessed under compressive and tensile tests, respectively. Based on the results of this study, the relationships presented in Ninth Article of Iranian National Building Codes, ACI-318 and Euro Code 2 have been evaluated.
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