Mod-2 wind turbine system concept and preliminary design report. Volume 1: Executive summary

The configuration development of the MOD-2 wind turbine system is presented. The MOD-2 is design optimized for commercial production rates which, in multi-unit installations, will be integrated into a utility power grid and achieve a cost of electricity at less than 4 cents per kilowatt hour

Buildings and Structures under Extreme Loads II

Exceptional loads on buildings and structures are known to take origin and manifest from different causes, like natural hazards and possible high-strain dynamic effects, human-made attacks and impact issues for load-bearing components, possible accidents, and even unfavorable/extreme operational conditions. All these aspects can be critical for specific structural typologies and/or materials that are particularly sensitive to external conditions. In this regard, dedicated analysis methods and performance indicators are required for the design and maintenance under the expected lifetime. Typical issues and challenges can find huge efforts and clarification in research studies, which are able to address with experiments and/or numerical analyses the expected performance and capacity of a given structural system, with respect to demands. Accordingly, especially for existing structures or strategic buildings, the need for retrofit or mitigation of adverse effects suggests the definition of optimal and safe use of innovative materials, techniques, and procedures. This Special Issue follows the first successful edition and confirms the need of continuous research efforts in support of building design under extreme loads, with a list of original research papers focused on various key aspects of structural performance assessment for buildings and systems under exceptional design actions and operational conditions

Dynamic performance of transmission pole structures under blasting induced ground vibration

Structural integrity of electric transmission poles is crucial for the reliability of power delivery. In some areas where blasting is used for mining or construction, these structures are endangered if they are located close to blasting sites. Through field study, numerical simulation and theoretical analysis, this research investigates blast induced ground vibration and its effects on structural performance of the transmission poles. It mainly involves: (1) Blast induced ground motion characterization; (2) Determination of modal behavior of transmission poles; (3) Investigation of dynamic responses of transmission poles under blast induced ground excitations; (4) Establishment of a reasonable blast limit for pole structures; and (5) Development of heath monitoring strategies for the electric transmission structures. The main technical contributions of this research include: (1) developed site specific spectra of blast induced ground vibration based on field measurement data; (2) studied modal behavior of pole structures systematically; (3) proposed simplified but relatively accurate finite element (FE) models that consider the structure-cable coupling; (4) obtained dynamic responses of transmission pole structures under blast caused ground vibration both by spectrum and time-history analysis; (5) established 2 in/s PPV blast limit for transmission pole structures; (6) developed two NDT techniques for quality control of direct embedment foundations; and (7) described an idea of vibration-based health monitoring strategy for electric transmission structures schematically

協方差型隨機子空間識別法之應用

In this research the application of output-only system identification technique known as Stochastic Subspace Identification (SSI) algorithms in civil structures is carried out. With the aim of finding accurate modal parameters of the structure in off-line analysis, a stabilization diagram is constructed by plotting the identified poles of the system with increasing the size of data matrix. A sensitivity study of the implementation of SSI through stabilization diagram is firstly carried out, different scenarios such as noise effect, nonlinearity, time-varying systems and closely-spaced frequencies are considered. Comparison between different SSI approaches was also discussed. In the following, the identification task of a real large scale structure: Canton Tower, a benchmark problem for structural health monitoring of high-rise slender structures is carried out, for which the capacity of Covariance-driven SSI algorithm (SSI-COV) will be demonstrated. The introduction of a subspace preprocessing algorithm known as Singular Spectrum Analysis (SSA) can greatly enhance the identification capacity, which in conjunction with SSI-COV is called the SSA-SSI-COV method, it also allows the determination of the best system order. The objective of the second part of this research is to develop on-line system parameter estimation and damage detection technique through Recursive Covariance-driven Stochastic Subspace identification (RSSI-COV) approach. The Extended Instrumental Variable version of Projection Approximation Subspace Tracking algorithm (EIV-PAST) is taking charge of the system-related subspace updating task. To further reduce the noise corruption in field experiments, the data pre-processing technique called recursive Singular Spectrum Analysis technique (rSSA) is developed to remove the noise contaminant measurements, so as to enhance the stability of data analysis. Through simulation study as well as the experimental research, both RSSI-COV and rSSA-SSI-COV method are applied to identify the dynamic behavior of systems with time-varying characteristics, the reliable control parameters for the model are examined. Finally, these algorithms are applied to track the evolution of modal parameters for: (1) shaking table test of a 3-story steel frame with instantaneous stiffness reduction. (2) Shaking table test of a 1-story 2-bay reinforced concrete frame, both under earthquake excitation, and at last, (3) damage detection and early warning of an experimental steel bridge under continuous scour.UCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Ingeniería Civi

A survey of the wind energy resource of Cornwall to examine the influence of settlement patterns and topography on optimum wind turbine size and disposition

The introduction of wind turbines has led to complaints about noise, domination and radio frequency interference from neighbouring properties. The aim of the thesis was to determine how the pattern of rural settlement and topography influences the gross technical resource, and how this resource is affected by various combinations of wind turbine size, type and cluster layout. The work consisted of examining in detail every possible site in Cornwall and every large site in England and Wales. This involved establishing a computer data base where each location was described by over three dozen relevant site characteristics. In determining mean annual site wind speeds at hub height the data from twentysix meteorological stations and the results of over fifty Tala kite ascents were used to calibrate four predictive models for site wind speed and to choose the best one for this thesis. Five noise prediction models were tested against field results for twentytwo wind turbines. All the models were found to be inaccurate and a new prediction method with an accuracy of +/— 3^B(A) was developed. A public perception survey of over sixty households situated near six UK , wind turbines, and an examination of the way in which the 1974 Control of Pollution Act and planning policies are put into effect, both further defined acceptable environmental criteria for wind turbines. Noise and dominance were found to be the most serious restraints, whilst radio frequency interference eliminated over 40% of potential sites. The thesis shows that the resource is inversely related to wind turbine size. In Cornwall, the technical resource is 2.5MW for multimegawatt machines rising to 1555KW for quiet machines of 17m to 19m diameter

The uplift of high voltage transmission tower foundations

The in-service performance of transmission tower foundation systems is poorly understood. This knowledge deficiency is particularly acute with regard to the dynamic and transient loading of these foundations in uplift. There is also uncertainty surrounding the integrity of existing assets as design practice appears to overestimate the capacity of the foundations when they are subject to testing. A significant component of cost of new high voltage overhead line route construction or uprating involves the maintenance or reinforcement of the individual transmission tower foundation systems. Therefore, a more developed understanding of the foundation system behaviour is required to facilitate these works in a cost-effective and timely manner. To gain a better understanding of foundation system performance, a series of full scale rapid uplift tests were carried out in July 2012. The tests bridged understanding of the load-displacement, load-rate and rate effects of soils from previous experimental research to field scale, with associated construction and in situ soil nonlinearities. The tests made use of modern instrumentation and monitoring techniques in combination with rigorous numerical finite element back analysis to update understanding of in situ failure mechanisms and capture uplift capacity enhancements due to the application of rapid loading. The field tests and numerical back analysis results highlighted significant limitations in current design practice particularly the reliance on an outdated failure mechanism and ultimate limit state criterion. The results of the rapid uplift tests compared to standard industry practice suggested that the latter method may be unduly conservative leading to an underestimation of in-service capacities. The results presented will lead to a better understanding of foundation system performance and more legitimate design and testing practice technical specifications

Identifying loading and response mechanisms from ten years of performance monitoring of a tall building

Author version of article. The final published version is available from the publisher website via: doi:10.1061/(ASCE)0887-3828(2008)22:1(24)© 2008 ASCEIn 1993 Shimizu Corporation provided the opportunity to record manually readings of stress and strain gauges they had embedded at the 18th storey of a 65-storey office tower under construction in Singapore. Static readings continued during construction and long after, and capitalising on access to the building and assistance of both contractor and owner, monitoring systems for tracking wind, acceleration and deflection were installed and progressively upgraded. Further, a comprehensive ambient vibration survey and finite element model updating exercise provided a thoroughly validated analytical model of the structure. This model has been used in parallel with the analog wind and tremor ‘super-sensor’ of the building itself to provide direct evidence and characterization of the seismic and wind loadings on the building. This paper describes the evolution of the monitoring system and its capabilities together with some of the insights the system provided into structural and loading mechanisms during its operational life until early 2005.