With the increase of knowledge in seism city and subsequent need to modify the earthquake engineering design specification for buildings, it would be essential to investigate the behavior of such buildings and structures and the probable need for seismic retrofitting. On the other hand there are construction problems in strengthening and retrofitting methods using bracing system that reduces the owners wish to do so. In this paper an attempt has been made to investigate the behavior of existing building designed by second version of standard for seismic design of buildings and retrofitting of such structures using ADAS Added Damping and Stiffness. For this purpose steel buildings are retrofitted once using bracing members alone and then using both bracing and ADAS dampers. The behavior of the steel frames was compared using non linear time history analysis. The behavior factor 'R' was calculated for each case.
|Published (Last):||28 December 2010|
|PDF File Size:||4.51 Mb|
|ePub File Size:||5.7 Mb|
|Price:||Free* [*Free Regsitration Required]|
Nonlinear static analysis of the frames indicates that by increasing ADAS stiffness, frame ductility does not change significantly, polynomial of second order relationship. Introduction Usage of dissipating energy devices against earthquake input energy is increasing in earthquake resistance design of structure.
These systems are categorized into the following groups : a Base isolation systems, b Active and semi-active systems, c Passive systems. Structural designer are encouraged to use metallic dampers as passive control systems for seismic design of structures due to several reasons.
First of all, no complicated technology is needed to manufacture them. They can easily be integrated in structures, and they show stable behavior in earthquakes and no environmental temperature, humidity, etc. These dampers increase energy dissipation capacity and stiffness of structures.
Adding metallic dampers to the structures can cause concentration of energy dissipation in dampers and after earthquakes they can be easily replaced for strengthening structure for future earthquakes. ADAS elements, as a metallic damper, can be designed to be installed in both new and existing buildings. If correctly designed and implemented, ADAS elements can: o increase the strength, stiffness and usable energy dissipation capacity of a conventional MRF, and o Substantially increase the energy dissipation capacity, per unit interstory drift, of a non- ductile CBF.
Two types of steel plates are more prevalent in ADAS elements, X bent in double curvature and triangular bent in single curvature type. These plates yield uniformly and the plastic deformation distribute uniformly over the height of the plate. Using steel plates for absorbing and dissipating energy was first used exclusively in nuclear installation .
Kelly et al. Whittaker et al. Xia et al. Tsai et al. ADAS Stiffness formulation  The stiffness matrix of an elastic nonprismatic element, such as the plates that compose the ADAS device, can be defined using the flexibility method. The geometry of the ADAS device is closely represented by the exponential functions.
The width of the device is slightly underestimated near the fixed ends and at midspan. This underestimation should not be critical because the curvatures on those regions are small, as computed and reported by Whittaker et al. Then, using trial and error, the calculation must be modified in order to find an optimum value of SR. The force-displacement diagram in Fig. The specifications of used dampers are presented in Table 1.
This element is based on Timoshenko beam theory and Shear deformation effects are included. Elasticity, creep, and plasticity models are supported in this model . SHELL43 is well suited to model linear, warped, moderately-thick shell structures. The element has six degrees of freedom at each node: translations in the nodal x, y, and z directions and rotations about the nodal x, y, and z axes.
The element has plasticity, creep, stress stiffening, large deflection, and large strain capabilities . The results of von misses stress and plastic strain are illustrated in Fig. Fig 5: Results of von misses stress and von misses plastic strain 5.
Analysis of the Results Fig. These results indicate that, by increasing ADAS stiffness, ductility of the frame does not change significantly, but frame force level increases.
The results indicate that U decreases while SR value increase. According to Fig. Conclusion ADAS dampers play significant role in reducing the earthquake forces and in increasing the ductility of the structures. Using finite element analysis and parametric study, the main focus in this paper is on establishing a logical relationship between design parameters of ADAS.
Acknowledgement The Author would like to gratefully acknowledge the Islamic Azad University, Rasht Branch for supporting this research. Society for Earthquake Engineering, , Ctr, Univ. Related Papers. By Mahendra Umare. By Taksiah Majid. A passive metallic damper with replaceable steel bar components for earthquake protection of structures.
By Reza Aghlara. Seismic response of structures with coupled vertical stiffness—strength irregularities. By fardin shirkosh. Innovative strategies for seismic retrofitting of steel and composite structures. By luigi di sarno. Download pdf. Remember me on this computer. Enter the email address you signed up with and we'll email you a reset link. Need an account? Click here to sign up.
RETROFITTING OF EXISTING STEEL BUILDINGS USING ADAS DAMPERS