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Vibration from demolition and construction activities poses a serious risk to museum objects. This case study presents preventive conservation and vibration monitoring strategies developed in response to a large-scale renovation project on the floor directly below the Egyptian Art galleries of the Metropolitan Museum of Art in order to safeguard this fragile, ancient art collection. The paper discusses the methods and procedures that were developed not only to protect the art but also to allow visitors continued access to as much of the collection as possible during the work period. In advance of the construction, pilot testing was performed to determine the levels of vibrations caused by different tools, as well as to gain a better understanding of vibration propagation within the museum and to specific objects through their mounts, pedestals, and display shelves. Vibration prone installations were modified with isolation and/or dampening approaches to mitigate vibration, or when possible, selected objects were deinstalled. A variety of mitigation solutions were shown to be effective through testing. During the demolition and construction phase, continuous wireless vibration monitoring was provided from within the galleries, and sometimes from sensors directly on objects or their shelves to provide near real-time alerts to museum staff and construction personnel. Alert levels were based on frequency independent velocity levels.

In the wake of the 1999 earthquake destruction in Turkey, the urgent need has arisen to evaluate the benefits of loss mitigation measures that could be undertaken to strengthen the existing housing stock. In this study, a benefit-cost analysis methodology is introduced for the comparative evaluation of several seismic retrofitting measures applied to a representative apartment building located in Istanbul. The analysis is performed probabilistically through the development of fragility curves of the structure in its different retrofitted configurations. By incorporating the probabilistic seismic hazard for the region, expected direct losses can be estimated for arbitrary time horizons. By establishing realistic cost estimates of the retrofitting schemes and costs of direct losses, one can then estimate the net present value of the various retrofitting measures. The analysis in this work implies that, even when considering only direct losses, all of the retrofitting measures considered are desirable for all but the very shortest time horizons. This conclusion is valid for a wide range of estimates regarding costs of mitigation, discount rates, number of fatalities, and cost of human life. The general methodology developed here for a single building can be extended to an entire region by incorporating additional structural types, soil types, retrofitting measures, more precise space- and time-dependent seismic hazard estimates, etc. It is hoped that this work can serve as a benchmark for more realistic and systematic benefit-cost analyses for earthquake damage mitigation.

In this paper, an adaptive on-line parametric identification algorithm based on the variable trace approach is presented for the identification of non-linear hysteretic structures. At each time step, this recursive least-square-based algorithm upgrades the diagonal elements of the adaptation gain matrix by comparing the values of estimated parameters between two consecutive time steps. Such an approach will enforce a smooth convergence of the parameter values, a fast tracking of the parameter changes and will remain adaptive as time progresses. The effectiveness and efficiency of the proposed algorithm is shown by considering the effects of excitation amplitude, of the measurement units, of larger sampling time interval and of measurement noise. The cases of exact-, under-, over-parameterization of the structural model have been analysed. The proposed algorithm is also quite effective in identifying time-varying structural parameters to simulate cumulative damage in structural systems. Copyright © 2001 John Wiley & Sons, Ltd.