Performance Improvement in Steel Structures, Implementing ADAS Yielding Damper, Using Non-linear Analysis

Abstract The objective of present study is to improve the performance of steel structures, Implementing ADAS yielding damper, by means of non-linear analysis. ANSYS software is utilized to model ADAS damper. 3 buildings of 5, 10 and 15 stories are studied with and without damper. Non-linear method was used to analyze. Load, displacememt, ductility, energy absorption and total strength graphs of different samples were compared. The results represent that in the 5-story structure, addition of ADAS damper leads a 3 time increment of total strength, 57% increment of ductility and 164% increment of energy damping. In the 10-story structure, addition of ADAS damper leads a 143% increment in total strength, a 25% increment in ductility and 104% increment of energy absorption. In 15-story structure, addition of ADAS damper leads a 24% increment in total strength, a 11% increment in ductility and a 40% increment in energy absorption. Maximum ductility is related to the model 6 with a value of 6.03 and the minimum ductility is obtained in model 1 with a value of 3.12. The maximum total strength is related to model 6, equal to 2913 tons and model 1 is related to minimum total strength of 632 tons. When comparing the energy absorption, model 1 and model 6 had the minimum and the maximum values relatively. To conclude, ADAS damper has the highest effect on short structures. The best performance of ADAS damper in comparison with the same sructure without damper is observed in 5-story buildings.

severe eartquakes, generally a vast non-linear behavior takes place in the structures in which the structures with unsufficient strength and ductility may collapse [5,6]. During recent decades, some studies have been performed on structure control. Active control systems are a branch of inactive bahavior control studies in the structures. Through inactive control, the applied energy damps in the structure thererfor the damages minimize. Inactive damping is categorized to different classes such as metallic dampers, friction dampers and liquid dampers. Metallic dampers are widely used by researchers [7][8][9]. Metallic dampers dissipate energy by pre-failure plastic deformations of the material. The advantages of these dampers are stable hysteresis behavior, low sensebility to temprature changes, high reliability and proper cost [9]. The most used energy dissipating dampers are TADAS and ADAS dampers. Thesesdampers are made up of X-shaped plates that present an out of plane bending behavior. The dimensions of such dampers are designed to have a uniform stress distribution in dampers height and all parts of the damper fail simultaneusly [10]. As the dampers dimensions are such important, recently, some studies have been performed to optimize the dimensions and performance of the damper while loading proccesses lead to fatigue [11]. Slit dampers is an innovative type of metallic dampers. These dampers are consisted of slit plates that undergo irreversible deformations. This research is about to study the performance of ADAS dampers [12,13].

Research method
The structures design is performed using EATBS software. The structures are designed and sections and frames'dimensions are calculated and controlled by means of code regulations. After that the results are used for finite element method part of ANSYS software. Modelling was performed 2D, while varying the building height using ANSYS finite element software and analyzed using static non-linear method.

3-1-model verification
To make sure about the results obtained from ANSYS software, a sample of steel structure is selected from an article from Eswaramoorthi et al. [14] and is modeled and compared with experimental sample. A desirable conformation is observed between numerical and experimental results.

3-2-Studied models
Through out this section, the studied models are introducted considering the modelling reliability. In order to study the performance of 3 different types of structures with different dimemsions are utilized. First of all, the structures are designed considering 10th topic of national building regulations code. To study the results betterly, the models are devided in 3 classes considering their story numbers. ADAS damper is assumed to be a four-bladed one and its stiffness is calculated using structure analysis methods. Then the effect of ADAS damper is studied, implementing a composite element in ANSYS software. Tables (2) and (3) represent the characteristics of studied models of this research. The dimensions used in present paper are Meters (m) and Newton (N) for length and force, respectively.

Analysis results
The results of static push-over analysis results are studied in this section. Table (4) represents the seismic parameters for each of the 6 models. As it is apparent, maximum ductility is related to the model 6 with a value of 6.03 and the minimum ductility is obtained in model 1 with a value of 3.12. The maximum total strength is related to model 6, equal to 2913 tons and model 1 is related to minimum total strength of 632 tons. When comparing the energy absorption, model 1 and model 6 had the minimum and the maximum values relatively. As the story number and ADAS damper strength parameters increase, ductility and energy absorption also increase.   Fig. (7) shows the force-displacement curves for 6 models of 5, 10 and 15-story structures with or without damper. Displacement is then studied in the models. Fig. (8) shows the displacement of 5-story structure. The displacement of the 10-story structure with out damper is represented in fig. (9).

4-1-Comparison of structures' seismic parameters
Bar graphs of total strength for 5, 10 and 15-story structures with and without damper are presented.
Considering graph (1)-(a) it is observed that existance of ADAS damper, significantly affects total strength of the system in 5-story structure in such a way that ADAS damper increases the total strength upto 3 times. Thus, the ADAS damper highly improves total strength. Addition of ADAS damper to 10-story structure increases the total strength 143%. Addition of ADAS damper to 15-story structure increases ductility 24%.

4-2-Ductility comparison
Considering graph (2), ADAS damper has a significant effect on ductility of system. As it is obvious, ductility is increased 57% by adding ADAS damper. Using ADAS damper has increased ductility 25% in the 10-story structure. In the 15-story structure, ductility has been increased 11% by addition of ADAS damper.