Earthquake Resistant Structure Base Isolation

In past few years, passive control mechanisms including base isolation systems are gaining large attention as mean to protect structures against seismic hazard. The effectiveness of an isolation system depends upon the dynamic characteristics of earthquake ground motion and the building superstructure. The base isolation system separates the structure from its foundation and primarily moves the natural frequency of the structure away from the dominant frequency range of the excitation via its low stiffness relative to that upper structure. In order to verify the effect of base isolation system, the structure is presented as symmetrical building in which the seismic responses of the 'fixed-base' and 'base-isolated' conditions have been compared using a well-known computer program SAP2000 version 14. The aim of this study is to reduce the base shear, story drifts and story acceleration due to earthquake ground excitation, applied to the superstructure of the building by installing base isolation devices at the foundation level and then to compare the different performances between the fixed base condition and base-isolated condition of symmetrical building. The high damping rubber isolation system has been used at the foundation level. Non linear time history analysis has been performed on El-Centro earthquake. Comparing the results of the base -isolated condition with those obtained from the fixed-base condition has shown that the base isolation system reduces the base shear force, story drifts and storey acceleration, also increasing the storey displacement and time period.

Base isolation is a mechanism that provides earthquake resistance to the new structure. The base isolation system decouples the building from the horizontal ground motion induced by earthquake, and offers very stiff vertical components to the base level of the superstructure in connection to substructure (foundation). It shifts the fundamental lateral period, dissipates the energy in damping, and reduces the amount of the lateral forces that transferred to the building, inter-story drift, and the floor acceleration. The work deals with modelling and finite element analysis of a high damping rubber bearing in ANSYS 12.0. A displacement controlled transient analysis was done to analyse the behaviour of the isolator during earthquakes.

International Journal of Engineering Research and Technology (IJERT), 2021

https://www.ijert.org/behaviour-of-building-under-earthquake-with-or-without-base-isolation-by-varying-thickness-of-lead-rubber-bearing https://www.ijert.org/research/behaviour-of-building-under-earthquake-with-or-without-base-isolation-by-varying-thickness-of-lead-rubber-bearing-IJERTV10IS080052.pdf A base-isolated building may sometimes show signs of an undesirable large response to long-duration, longperiod earthquake ground motion and an connected building system without base-isolation may show a large response to a near-fault earthquake ground action. The installation of base isolation in building at base level significantly increases the time period of the structure, this means it reduces the possibility of resonance of the building giving rise to well seismic performance of the building. The research study is performed to compare the effectiveness of base Isolation in plan unbalanced and vertical multi-storied RC frame building. For this research study, number of Storied RC frame building is well thought-out and time times gone by analysis is conceded out using ETABS Software. The lead rubber bearing is designed as per IS code and the same was used for psychotherapy of base isolation system. The outcomes obtained from the analytical analysis were time period, base reaction, story drift and story acceleration. Time period for the base isolated buildings are higher than that of the permanent base building. Due to the existence of base isolation, base shear is significantly Reduced in each direction (x and y direction) as compared to fixed base structure. It has been found that when related to plan base isolated structure gives better performance in high Seismic prone zone by using isolators at the base of the building.

Lecture Notes in Civil Engineering, 2019

Seismic isolation is one of the most efficient techniques to protect structures against earthquakes. Rubber bearings are suitable for low-rise and medium-rise buildings due to its durability and easy fabrication. This paper presents the horizontal response of a six-storey base-isolated building using high damping rubber bearings (HDRBs) under two ground motions of earthquakes as types I and II in JRA (2002) by finite element analysis. In this analysis, these bearings are modelled by the bilinear hysteretic model which is indicated in JRA and AASHTO. Comparison of horizontal response including base shear force and roof level acceleration between the two cases: base-isolated building and fixed-base building is carried out to evaluate the effectiveness of the use of HDRBs on the protection of buildings from earthquakes. The numerical results show that the peak value of roof floor acceleration of the fixed-base building is two times higher than that of the base-isolated building, and the floor accelerations depend on the peak values of ground acceleration. In addition, the step-bystep design procedure for determining the size of HDRBs used for buildings is also presented in this paper.

Jurnal Teknologi, 2013

Nowadays the main cause of damage of reinforced concrete frames in the countries which are located on the seismic line area is earthquake even though they are designed due to the enactment of seismic codes. To provide a solution to these problems, Lead Rubber Bearing (LRB) system has been utilized in the construction of the buildings. Hence, the objective of this study is to determine the best configuration of the LRB in the structure by calculating the response of the structure, roof level acceleration and interstory displacement based on the ground motion records. The study consists of determining the structure, calculating the weight of structure, modelling the LRB in the structure and obtaining the output from the dynamic analyses. The comparison of the inter-story displacement, drifts frames and top level acceleration response of the LRB system with the Fixed Base System (FBS) using spectrum and time history analysis shows that the base shear reduces by 65-75% in response spectrum analysis, while in time history analysis base shear reduces by 75-85%. The proposed method is based on the LRB system that reduces the response of the structure because of high damping and stiffness used in the Base Isolation System (BIS) and capable to be used for super structure located in the seismic line area. This system would help in reducing the cost in the long time and increase the safety of the structure.

International Journal for Numerical Methods in Engineering, 1999

A ÿnite element formulation modelling hyperelastic quasi-incompressible rubber-like materials (elastomers) is developed which takes into account large displacements and large elastic strains as well as inelastic e ects. The capacity of laminated rubber-like materials to support high loads in compression and large displacements in shear is the principal reason for their use in devices for seismic base isolation of structures. The energydissipation capacity of these devices is increased by using high damping rubber, which is an elastomer incorporating carbon black particles, or having lead-plug insertion. The Ogden strain energy function has been used as a basis for the material model implemented in a total Lagrangian formulation, the strain being decomposed into its deviatory and volumetric parts and the pressure variable being condensed at element level. Mooney-Rivlin and neo-Hooke strain energy functions can also be used by simply changing the parameters of the model. The stress-strain hysteresis, which appears when these devices are subjected to dynamic or quasistatic cyclic loads, has been modelled by frequency dependent viscoelastic and plastic constitutive models. The bearings have been modelled by means of an equivalent single element capable of describing the composite behaviour of the actual isolation system. The proposed model is validated using available experimental results and it is proved to be a powerful tool in dealing with di erent bearings. Finally, results for a six-storey base isolated building subjected to the El Centro earthquake are given.

IRJET, 2022

The damage to structures, when shaken by an earthquake, is due to factors like too much load on the structure (caused by post plan approval modification- like a 10 storey building in Ahmedabad which had a terrace garden cum pool and so it collapsed in the Jan 2000 Gujarat earthquake- though all equally tall structures all around it did not collapse); poor distribution of structural load creating joints or walls which give way under the sudden excess load due to vibration; poor foundations- too shallow for the height of the structure, built on land reclaimed from water bodies but soil not compacted etc. This shows how necessary it is to follow the building code prescribed for a given area/ region by the government. In earthquake prone areas like Japan, Indonesia, California etc. some techniques have been used which enable the structure to reduce the amplitude of vibrations by making the foundation or load bearing structure move as if Lead rubber bearing is used. There are also prescribed designs for the RCC framework and the way load is transmitted to the foundations by interlinking etc. The earthquake resistant structure has made possible to guarantee a better performance of buildings, when they are subjected to seismic actions. Therefore it is convenient that current codes for design of building become conceptually when defining the various parameters governing the structure exposure conditions, geological conditions of proposed site, topographical parameters, geological parameters that includes: soil type, bearing capacity of soil The purposed of this work is to study analysis, design and estimate of high rise structure in various zones. And also compare the earthquake resistant structure and lead rubber bearing structure for same zones, if we can compare this building structure we can find out difference in construction cost also which is economical safe for us.

Conventional seismic design attempts to make buildings that do not collapse under strong earthquake shaking, but may sustain damage to non-structural elements and to some structural members in the building. This may render the building non-functional after the earthquake, which is not acceptable for important buildings, like hospitals, fire stations, etc. Special techniques are required to design buildings they remain practically undamaged even in a severe earthquake. Buildings with such improved seismic performance usually cost more than normal buildings. However, this cost is justified through improved earthquake performance. One of the technologies used to protect buildings from damaging earthquake effects is-Base Isolation‖. The idea behind base isolation is to separate (isolate) the building from the ground in such a way that earthquake motions are not transmitted up through the building, or at least greatly reduced. The work undertaken is an attempt to understand the fundamentals of Base Isolation, its design &behavior under seismic loading. A RCC building of Basement + GF +4 has been considered with basement constructed of RCC wall at its periphery. IBC 2000 recommendations were used. The basic types of base isolator namely High Damping Rubber Bearing (HDR) was designed. The base isolated RCC building was exposed to Design Spectrum seismic loading of IS 1893-2002 (Part I) to compute its response. The conclusions were drawn on the basis of analysis and design of base isolator along with comparison of displacement, storey drift and base shear for fixed base with RCC isolated building. A commonly available, widely used software SAP2000.v16 was utilized.

Jordan Journal of Civil Engineering, 2008

Over the past two decades, much progress has been made in research and application of the base isolation of structures as means of providing earthquake resistance to a structure. However, the trade-off between the extent of acceleration reduction and the response of a base-isolation system has not been given a serious consideration. This work uses a new material constitutive model for rubber bearing base-isolation system, which adopts the technique of real-time structural parameter modification. To achieve this, a finite element modeling and analysis are performed as a comparative study between a conventional totally fixed-base steel frame structure and similar base-isolated structures using rubber-steel bearings. The structures are subjected to the El-Centro, N-S earthquake.