1,721,004 research outputs found
Design of a new passive energy dissipation system for earthquake resistant structures
No full textThe basic principle of conventional earthquake-resistant design that has been applied for the last 75 years is intended to ensure an acceptable safety level while avoiding catastrophic failures and loss of life.Over the last half century, a large amount of research has been conducted into developing innovative earthquake-resistant systems in order to raise seismic performance levels while keeping construction costs reasonable.Those structural control systems are broadly classified into three categories asPassive and,Active control, andSeismic isolation system. Passive control systems have been considered as an effective and inexpensive way to mitigate earthquake risks to the structures.Among different passive energy dissipation systems available metallic dampers are popular (and inexpensive) choice for an energy dissipation device because of its relatively high elastic stiffness, good ductility and it’s high potential for dissipating energy in the post yielding region. One of the metallic dampers namelyAdded Damping And Stiffness (ADAS) is the most commonly used metallic dampers in seismic design.
Usually, X-plates are chosen for mounted on a Chevron type bracing are usually chosen for ADAS. In principle, these devices dissipate energy through flexural yielding along the out-of-plane direction of the device, with an assumption of nearly rigid supporting Chevron bracing system along its in-plane direction. Clearly, these devices will be effective in resisting seismic excitation along one of the horizontal directions (in plane direction of the bracing). Other orthogonal components will be resisted by another set of devices installed in a frame spanning along the other orthogonal direction. This can be conveniently overcome if a device performing effectively in three dimensions is thought of.
Three dimensional model of such a device has been proposed in this thesis. The shape of the proposed damper is in the form of an hourglass, and it is referred toHourglass Added Damping and Stiffness (HADAS) device. The HADAS device is capable of dissipating the input energy along both orthogonal lateral directions, provided the supporting bracing system is relatively stiffer. However conventional chevron bracings as used in supporting ADAS devices, have negligible stiffness along the out-of-plane direction. Therefore, a suitable bracing system, capable of providing stiffness along any two lateral orthogonal directions are required to be developed for receiving full benefit from the HADAS devices. Such a bracing system is also proposed in this thesis.
In order to illustrate the improved seismic capacity of the building after installation of damper, a ten storey building located in seismic zone - IV of India is designed conforming to Indian Standards. Three seismic events recorded at the Large Scale Seismic Testing (LSST) array in Lotung, Taiwan are used for the purpose of illustration. The improved performance of building is assessed by comparing peak floor displacement, peak storey drift, peak storey shear force building without and with the devices
Proportioning elastomeric bearings in a seismically isolated building with horizontal and vertical setbacks and torsional irregularities
No full textExperimental determination of natural frequency of confined masonry building by ambient and forced vibration testing
No full textField testing of full scale structure always gives a better idea about its characteristics properties as compared to analysis of the structure in different softwares which includes lot of assumptions and idealization, leading to approximation of the results .This study aims at investigating the fundamental period of vibration of confined masonry buildings located at the campus of IITGN, by measurements of ambient and forced vibrations. This study is extensively carried out on Type-III housing buildings of IITGN and extended to Type-I and Type-II housing buildings. Ambient vibrations were measured for various time durations and on different positions at roof level of a selected three story building by a single seismic accelerometer. Auto spectral density plots for ambient vibrations gave a fair idea of natural frequency of a building .Further, forced vibration testing were also carried out repeatedly on various locations at roof level of a building using electrodynamic mass shaker. Natural frequency was confirmed by plotting auto spectral density functions for ambient and forced vibrations of the buildings, signal to noise ratio plots, and Acceleration Response factor obtained from harmonic input vibrations to the building. The results obtained from experiments are compared by natural frequency obtained from modelling the buildings in SAP 2000. On the basis of results, a new formula for calculation of natural time period for confined masonry buildings has been recommended
A novel framework for developing ground motion prediction models consistent with critical orientation and its implementation in seismic performance assessment
No full textOn improved seismic performance of reinforced concrete structures using steel fiber reinforcement analytical feasibility study
No full textDisplacement based design framework for confined masonry system using strut and tie model
No full textThe confined masonry construction has become increasingly popular in earthquake prone areas due to its satisfactory performance in withstanding the past seismic events and low construction cost. Computation and design member force resultants involves numerical modelling. Since FEM is computationally expensive, simplified approach like Wide Column Model (WCM) is widely accepted in routine seismic design. However it has its own limitations such as, inability to capture the stress concentration around the joints and openings. In such cases Strut and Tie Method (STM) serves as a viable alternative. A case study is presented identifying the lacunas of the current STM when applied to confined masonry system. One of the challenge is the inherent indeterminacy. An approximate approach is proposed to resolve the issue. Further Performance Based Earthquake Engineering has been accepted all over the world. However little has been reported to date in context with the design of confined masonry system. A design framework is proposed in this thesis, with numerical modelling for performance assessment. Example problem is included and compared with the experimental results reported in literature. Overall, the proposed framework shows a great promise of developing performance based design of confined masonry system
Characterization and influence of multicomponent spatially varying ground motion field on structural demand
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