Synthesis of accelerograms compatible with the Chinese GB 50011-2001 design spectrum via harmonic wavelets: artificial and historic records

A versatile approach is employed to generate artificial accelerograms which satisfy the compatibility criteria prescribed by the Chinese aseismic code provisions GB 50011-2001. In particular, a frequency dependent peak factor derived by means of appropriate Monte Carlo analyses is introduced to relate the GB 50011-2001 design spectrum to a parametrically defined evolutionary power spectrum (EPS). Special attention is given to the definition of the frequency content of the EPS in order to accommodate the mathematical form of the aforementioned design spectrum. Further, a one-to-one relationship is established between the parameter controlling the time-varying intensity of the EPS and the effective strong ground motion duration. Subsequently, an efficient auto-regressive moving-average (ARMA) filtering technique is utilized to generate ensembles of non-stationary artificial accelerograms whose average response spectrum is in a close agreement with the considered design spectrum. Furthermore, a harmonic wavelet based iterative scheme is adopted to modify these artificial signals so that a close matching of the signals’ response spectra with the GB 50011-2001 design spectrum is achieved on an individual basis. This is also done for field recorded accelerograms pertaining to the May, 2008 Wenchuan seismic event. In the process, zero-phase high-pass filtering is performed to accomplish proper baseline correction of the acquired spectrum compatible artificial and field accelerograms. Numerical results are given in a tabulated format to expedite their use in practice

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Non-linear viscous damping identification using genetic algorithms

(in press

Robust design of tuned mass damper systems for seismic protection of multistory buildings

In this paper, a method is proposed for the robust design of tuned mass damper (TMD) systems for seismic protection of multistory buildings. The seismic excitation is a random ground motion acceleration modeled by a stationary filtered white noise process. The protected building consists of a generic multi-degree-of-freedom (MDOF) structure, represented by its modes of vibration and linear mass dampers. The design properties of the TMD system are mass, frequency and damping ratio of the TMD units, along with their location within the structure, considered as fixed at its base. Uncertainties in the properties of both the building and the input seismic excitation are explicitly accounted for in the robust design of the TMD system. In particular, the uncertain parameters considered are stiffness and damping of the structure, and frequency and damping properties of the Kanai-Tajimi model used for representing the surface ground filter of the white noise process acting at the bedrock. The response quantity chosen to be representative of the seismic demand in the building is the interstory drift ratio. Its variation to the uncertainties is treated with the direct perturbation method, by applying a mixed-order approach. Robustness in the design of the TMD properties is formulated as a multiobjective optimization problem, in which both mean and standard deviation of the building response, produced by the considered uncertain parameters, are minimized. The weighted sum method is applied for transforming the multiple objective into an aggregated scalar objective function and then solving the minimization problem. The proposed design procedure is implemented on an illustrative example, consisting of a multistory building protected with a TMD system made from two units that have to be tuned with the first- and second-mode period of the structure, respectively. Parametric analyses on protected systems characterized by different properties are carried out, and the significance of the effects produced by the variation of such properties on the optimum design of the TMD system is shown. Differences between a robust design with the proposed procedure and a more conventional one that does not account for uncertainties in the system properties are finally evaluated. © 2014 American Society of Civil Engineers