Seismic Response Control of High Rise Mass Varied Structures using Friction Dampers
Abstract
When a seismic event causes unwanted motion in buildings, energy dissipation techniques in civil engineering are required. There are a variety of structures with passive energy dissipation provided by Passive Constant friction damper systems (CFRD). This technique is being used more and more to increase seismic protection for both existing and new constructions. The CFRD system results are explored in order to compare the structural response with and without this device of energy dissipation compared for low and high rise mass varied buildings, the damper put at different storey and altering the slip force has been focused in this study which gives an insight into the variation of slip load and its locations. The CFRD's potential to boost the structure's dissipative capacities without increasing stiffness was discovered. In the case of high-rise buildings, CFRD performance has been examined using top-storey displacements, allowing for a conclusion.
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Introduction
Tectonic plate movement‟s results in shaking of earth crust which will induce the waves like Primary, Secondary and Love waves on the earth‟s surface. Structures subjected to seismic excitation results in inertial forces [1] for mass of structure, inherent damping force of structure and resisting force by material stiffness, will try to curb the oscillation. As per IS 875 (Part-3):2015 based on height of structures classified as low and high rise, low rise structures due to stiffness can withstand and reduce the top storey displacement to some extent but not in the case of high rise or mass varying. Dampers which can be the solution for reducing the top storey displacements which it is classified into 4 categories like passive, semi-active, active and hybrid [2], in this study we focus on passive friction dampers [3]. Passive friction dampers are easy to install, effective in reducing energy from the system and requires frequent maintenance, in passive system of damping doesn‟t require any external power to dissipate seismic energy from the structure, also not required any sensors or external system to monitor, absorption of energy achieved by sliding one plate over another by means of clamping force , clamping force as increases will acts as a strut this phase is called as stick phase once the amount of force is greater than the clamping force from the structure then it will enters to slip phase where the resistance between two plates will be zero, the friction damper is purely displacement dependent device. A 3 [4] low rise and 11 [5] storey high rise benchmark mass varied buildings considered for the study using matlab as a tool by state space [6], frequency of the lumped mass models matches exactly with benchmark problems and hence study focused on reducing the top storey displacement for Elcentro 1940 earthquake for 5 g and 0.3417 g [7] accelerograms both the types of building, using passive friction damper at different location or storey‟s [8] in the building or structure, finding minimum numbers and location of dampers were discussed in this paper.
Conclusion
1. Mass kept same in all storey‟s with CFRD to reduce the top storey displacements required 19 % less force compared to BMP.
2. Mass and stiffness are varied with CFRD to reduce top storey displacements upto 40 %.
3. It is nearly hard to maintain the same mass throughout all storeys in real time.
4. CFRD at two alternate storey in low and high rise cases shows good results when compared to CFRD installed at all storey‟s.