دانلود رایگان مقاله انگلیسی تحلیلی بر رفتار لرزه ای قابهای مهاربندی شده معکوس - اشپرینگر 2018

Abstract

An inverted V-braced frame is one of the most widely used CBFs (Concentrically Braced Frames) owing to many advantages in constructional design. The seismic behaviors of inverted V-braced frames is that brace buckling occurs due to strong motion generation, and that in turn vertical unbalanced force is created between tension brace and compression brace, resulting in an additional load onto beams. Thus, members of beams should be designed to have enough strength to ensure plastic hinge is not created. In this study, a series of finite element analysis was conducted to evaluate the earthquake-resistant performances of the methods to design the clearance distance of gusset plates in inverted V-braced frames, and to evaluate vertical unbalanced force depending on the cross-section size of beams. It was found that the results of the equation of vertical unbalanced force in the current standards were more conservative than the load generated through the real analysis model. In addition, the model of designing elliptical clearance distance showed higher earthquake-resistant performances than that of designing linear clearance distance, which requires the reconsideration and improvement of the current practices of calculating vertical unbalanced force and setting clearance distance.

6. Conclusions and Recommendations for Future

Work This study aimed to evaluate the influence of the methods of designing clearance distance of connections of gusset plates on the earthquake-resistant performances of inverted V-braced frames, and the vertical unbalanced force of inverted V-braced frames. To do so, 2 variables were applied to 6 specimens for finite element analysis, and the results of this study are as follows:

(1) The validity of the finite element analysis models was verified through the comprehensive comparison using the story shear force-deformation curves obtained from the test results of inverted V-braced frames (Okazaki et al., 2013), and through the local comparison using equivalent plastic strain and equivalent stress.

(2) The Balanced Design Procedure (BDP), a method of designing CBFs (Concentrically Braced Frames), and Ntp elliptical clearance were introduced, and their applicability to the gusset plate connections of inverted V-braced frames was evaluated. While the analysis models with Ntp elliptical clearance applied showed good earthquake-resistant performance, braces were fractured early in the analysis model with 2tp linear clearance applied as stated in the current standards.

(3) As indicated in the analysis results of variations, the smaller the cross section of beams in inverted V-braced frames was, the lower the earthquake-resistant performances were, including the increased deflection at the middle of beams; the decreased rigidity and strength of frames; and the early fracture of braces.

(4) Using the analysis results of all the variations, the real vertical unbalanced force applied to the beams of inverted V-braced frames was studied, and it was approximately 82% of the predicted results calculated using the vertical unbalanced force equation of the current standards.

(5) The analysis results of equivalent plastic strain indicated that the area most affected by vertical unbalanced force in beams was not the middle of beams, but the width end of gusset plates. In addition, depending on the methods of designing the clearance distance of gusset plates, the tension and compression forces of braces were different, which indicates that these factors associated with vertical unbalanced force should be considered in designing members.