International Journal of Advanced Structural Engineering
Volume:2 Issue: 2, Summer 2010

The performance of dual-layer multiple tuned mass dampers (DL-MTMD) with uniformly distributed natural frequencies is investigated. The DL-MTMD consists of one large tuned mass damper (L-TMD) and an arbitrary number of small tuned mass dampers (S-TMD). The primary structure is represented as a single degree-of-freedom system which corresponds to a specific vibration mode to be controlled in a real structure. The response of the structure with DL-MTMD is studied under harmonic excitation acting at the primary main system. The performance criterion used for assessing the optimum parameters and effectiveness of the DL-MTMD is selected as the minimization of the maximum dynamic magnification factor (DMF) of the displacement response of main structure. Two dynamic models of the DL-MTMD are proposed in the present study. The Model-I consists of S-TMD having the same mass and damping ratio and uniform distribution of natural frequencies. The Model-II consists of S-TMD with same stiffness and equal damping ratio and uniform distribution of natural frequencies. The comparative performance of the two models indicated that the performance of Model-II in comparison with Model-I is superior with respect to reduction in the displacement DMF.

Many old damaged and undamaged building structures do not meet the criteria of modern seismic design codes. Such structures need to be seismically enhanced. The main objective of this paper is to propose and validate the effectiveness of an upgrade scheme for non-seismic buildings using steel plate shear walls (SPSW). The upgrade is carried out considering a probability-based drift-based criterion, wherein incremental dynamic analysis is used for performance evaluation. The proposed upgrade procedure involves a static energy based scheme for the design of SPSW. It is tested on a 7- and a 5-story steel framed building structure. The results show substantial drift reduction overall, showing the effectiveness of the SPSW; however, selected target performance is not achieved exactly. Various reasons for the inability of the SPSW in meeting the probabilistic target are indicated. Overall, the proposed procedure is found to be effective for the upgrade of non-seismic steel frame structures to satisfy an inelastic drift-based probabilistic performance criterion. Need for future research works are indicated based on the shortcomings of the proposed procedure.

Earlier studies have shown conclusively that a Tuned Liquid Damper (TLD) is effective for controlling vibrations in structures subjected to narrow-banded wind excitations. A recent numerical study has shown that if the design parameters of a TLD are properly set, this device could also be very effective for controlling structural vibration to broad-banded earthquake excitations. Here the results of a reasonably comprehensive set of experiments are presented to investigate the overall effectiveness of TLDs and the specific effect of TLD parameters (depth and mass ratios) for earthquake vibration control of structures. Effects of various earthquake ground motions parameters such as amplitude, frequency content, duration of excitation etc. are also evaluated. It is shown that there is good agreement between the numerical simulation and experimental results. This experimental study conclusively shows that a properly designed TLD reduces structural response to broad-band earthquake excitations. It is also observed that effectiveness of TLD increases with increase in mass ratio, depth ratio and amplitude of ground motion.

In this paper the seismic evaluation of reinforced concrete structures in petrochemical facilities under sever conditions such as high pressure, high temperature and corrosive environment is studied. These structures were designed and constructed during 1976-78. The evaluation procedure is basically performed in two phases namely; a) qualitative and b) quantitative methods. In the qualitative evaluation, all possible documentations including drawings, specifications, structural calculations, new additions and test results were studied. Collected data then was summarized in an evaluation checklist. When the needed requirements did not meet the specified entries, more detailed and quantitative analysis were performed and utilized in this study. Quantitative and numerical study was performed using finite element modeling under sever loading combinations. Based on the results of this evaluation, some important RC structures in this plant were highly vulnerable to seismic forces which required immediate attention. The methodology used and results obtained can be generalized and adapted for similar facilities. This paper will present details, procedure and conclusions obtained.

In Western Coast of Gujarat destructive tsunamis have been generated from large earthquakes along the Makran Coast, Chagos Ridge and Kutch Region in the past. Although the historical record is incomplete, it is believed that such Tsunamis were destructive on the coasts of India, Pakistan, Iran, Oman and Sri Lanka and possibly had significant effects on Islands. The most significant tsunamigenic earthquake in recent times was that of 28 November 194521:56 UTC (03:26 IST) with a magnitude of 8.1 (Mw). In this paper an attempt is made for a numerical simulation of the tsunami generation from the Makran Subduction Zone, and its propagation into the Arabian Sea and its effect on the Dwarka city of Gujarat, India, through the use of a numerical model. It is observed from the results that the simulated arrival time of tsunami waves at the Dwarka is in good agreement with the available data sources. In this study more importance has been given to the run up height of tsunami waves, arrival time and inundation map. Also effect of different fault parameters on basic data is also studied.