http://hdl.handle.net/10397/913 Search the Channel search http://repository.lib.polyu.edu.hk/jspui/simple-search http://hdl.handle.net/10397/5733 Title: Comfort assessment of tower-like slender structures under typhoons and earthquakes<br/><br/>Authors: Liao, Weiyang<br/><br/>Abstract: Recently there has been an increasing demand for high-rise buildings and skyscrapers in urban areas all around the world. Due to their large scale and impressive height, flexible high-rise structures experience discomfort for the inhabitants in terms of excessive perceived motion caused by strong winds and earthquakes. Design of tall buildings should meet the serviceability criteria such that the wind and earthquake induced motions of a tall building within an acceptable range for occupant comfort, which may govern the design. Practices in this topic are usually based on the design wind and earthquake parameters according to historical experiences. Field measurement data of real structures, especially those of several hundred meters high, are very rare. Field monitoring of dynamic responses of a high-rise structure during typhoons and earthquakes provides a unique approach to verifying the parameters and assumptions adopted in design of the structure and to validating the wind tunnel or shaking table testing results. Particularly, a sophisticated structural health monitoring (SHM) system consisting of over 800 sensors has been implemented on the Canton Tower of 600 m high for both in-construction and in-service real-time monitoring. In the past three years, the Canton Tower has experienced several typhoons and earthquakes, during which both static and dynamic responses have been successfully collected through the SHM system. Taking the Canton Tower as the test bed, the research presented in this thesis is devoted to the investigation of comfort assessment of high-rise structures under typhoons and earthquakes. This PhD study has developed a vibration comfort assessment framework by considering various factors such as section type, torsion effect, whole structure response, and uncertainties. First, methodologies in signal processing for vibration comfort assessment are discussed. The torsion effect has been taken into consideration because of the asymmetry of the structure. Second, assessment of the comfort of top floor of the main tower and the contour map of serviceability are developed accounting for the torsion effect. Third, a procedure for assessing average comfort of the whole structure has been proposed by considering the structural profile and dynamic characteristics of the structure. Finally, a probability based reliability evaluation method of vibration comfort with the use of field monitoring responses is developed.; The framework is then applied to the comfort assessment of the Canton Tower using the monitoring data acquired during four typhoons. The wind properties such as mean wind and speed, turbulence and integral scale, gust factor and wind spectra, are first obtained. The acceleration responses at different levels under typhoons have also been investigated. The vibration comfort assessment considering the wind properties and spatial distribution of sensors has been conducted. A regression model is obtained to account for the torsion effect and wind properties. The real probability distribution of acceleration peak values has been obtained and compared with that used in the design. In this study, the principle of equivalent normalization is introduced to evaluate the reliability index because both the monitoring-obtained distribution and the distribution assumed in design do not obey the normal distribution. In a similar manner, the vibration comfort assessment framework is employed to assess the comfort of the Canton Tower under earthquakes. The vibration acceleration responses at each monitoring level under earthquakes are first investigated and discussed, in terms of depth, magnitude, and distance of the earthquakes. The acceleration responses are then used to assess the comfort of the top floor and the structure as a whole. In this context, the comfort index for the whole structure is developed according to the earthquake parameters. The corresponding regression model is also derived. In consideration of the uncertainties in both structure responses and criteria used in this assessment framework, a probability based comfort assessment method for the top floor is proposed in which the distributions of peak values under earthquakes are addressed. In summary, the research addressed in this thesis mainly contributes to the development of a vibration serviceability assessment framework for high-rise structures under typhoons and earthquakes using the field monitoring data. This study also benefits the design assumption verification and the improvement of design parameters for future high-rise structures.<br/><br/>Description: xxviii, 289 leaves : ill. ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577P CEE 2012 Liao http://hdl.handle.net/10397/5696 Title: Road safety implications of bus only lanes and bus drivers junction approaching behaviour<br/><br/>Authors: Tse, Lai Yin Vincent<br/><br/>Abstract: In Hong Kong, franchised buses, which share over one-third of daily journeys, play an important role in the public transport system. Whether they are being safely operated on roads is crucial to the government and public, but little attention has been paid by local researchers. This study therefore aims to look into two specific issues, which are expected to be crucial to the operation safety of buses. First, safety impact of the bus-only lane (BOL) system was studied. The BOLs in Hong Kong are mostly adopted in heavily trafficked corridors, similar to other major cities such as London and Seoul. This measure is aimed to improve bus service reliability by rationalizing road space usage, and hence to further increase bus modal share. Its safety issue has however generally been neglected. The conventional Before-After observational study technique and an alternative method were adopted to conduct an evaluation on this issue. Of the seven studied roads with BOLs, decreases of public bus accidents, both the fatal and serious (FS) and fatal, serious and slight (FSS) were reported; while increases of other vehicle FS accident were found. The results appear to suggest that public buses have been benefited from the BOL operation, but non-bus traffic had not or even had been harmed by that. Second, the driving behavior of bus drivers at signalized junction where most accidents occurred was studied. Through the experiences on red-light violation and Dilemma Zone (DZ) problems, the investigation of this study looked into driver approaching maneuver and decision-making behavior. Hypothesis tests and binary choice models were adopted to assess the performances of bus drivers at the studied junction. As was commonly expected, bus drivers reported to have better performances in response to facing decision dilemma at the start of amber. The dilemma area where the drivers confront Stop/Go decision was relatively small. Apart from the simulation model, the hypothesis test results reveal that bus drivers did adjust their approaching speeds at the times near the end of green signal. Such an action helped their responses to dilemma situation and attributed to their better performances. The results infer that the drivers could have higher consistencies in making Stop/Go decision at amber with the provision of signal information. Junction safety could thus be enhanced. The significances of this research study are: a) it is the first time that the impacts of BOL system on road safety were identified; b) it is the first time that the driving behavior of bus drivers at signalized junction was identified, both in the periods of amber and prior to the start of amber. These findings will contribute tothe safety design of BOLs and the effective trainings of bus drivers.<br/><br/>Description: xii, 108 leaves : col. ill. ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577M CEE 2012 Tse http://hdl.handle.net/10397/5695 Title: Multi-scale modelling of long-span bridges for health assessment in structural health monitoring<br/><br/>Authors: Yu, Yang<br/><br/>Abstract: Nowadays long-span bridges are usually modeled in different length scale levels for various research purposes. An accurate model should concurrently use the different theories at the respective scale level. The work described in this thesis aims to develop the effective strategies and methodologies for multi-scale finite element modeling of long-span steel bridges for health assessment and demonstrate its efficiency through analytical and experimental case studies as well as the practical engineering applications. The strategy and methodology of multi-scale modeling is successfully proposed and numerically implemented using mixed dimensional coupling through multi-point constraint equations. The reduced-scale specimen of the longitudinal steel truss has been studied in analytical computation and laboratory test. The comparison between the calculated results by different models and measurements data as well as the analytical results comparison with ones by other modeling methods suggest the proposed multi-scale model is the most efficient and accurate. All the strategies and implementation methods have been generalized and considered as applicable to full-scale long-span bridge structure. As an actual engineering application, a multi-scale model of long-span bridge of Tsing Ma Bridge is then developed by incorporating local detailed model of concerned location into structural global model based on proposed multi-scale modeling strategy. Structural global response at component scale and the hot-spot stress distribution of critical locations at local scale are then obtained simultaneously that can be used for structural health assessment and damage-related analyses. After performing sensitivity-based model updating and verification, the comparison results indicates that the developed multi-scale model is superior as compared to traditional two-step analyzing method. To demonstrate the developed multi-scale model can be further extended for nonlinear analysis, the linear and nonlinear seismic responses of the bridge under El-Centro ground motion are investigated considering geometric nonlinearity and bilinear hysteretic constitutive model. There are no universal principles to describe the influence pattern of traveling wave, so such effects should be specifically investigated for an individual bridge. The implementation schemes for nonlinear damage-related analyzing procedures are finally explored and outlined by introducing a nonlinear computing algorithm of constitutive equations combined with proper damage laws to consider the structural deterioration process.<br/><br/>Description: 1 v. (various pagings) : ill. (some col.) ; 30 cm. http://hdl.handle.net/10397/5694 Title: Study on ship emissions and its impact to air quality in Hong Kong<br/><br/>Authors: Yau, Pui Shan<br/><br/>Abstract: Hong Kong is one of the busiest ports in the world, but it is lacking in sophisticated maritime emission inventory and air quality assessment inside or near the port area. Most of the shipping activities in Hong Kong waters occur within a couple of kilometers from the community, and the emissions from ships may cause adverse health effects on the public. The current research focuses on two areas: (i) developing emission inventory on ocean-going vessels (OGVs) and (ii) investigating the contribution of ship emission to the air quality of a community near the international container port. The speed profiles of vessels on different shipping routes in Hong Kong waters were determined with Automatic Identification System. Compared with the emissions estimated using the speed limits of control zones, the ship emissions estimated using vessel speed profiles could provide results with up to 88% higher accuracy. Uncertainty analysis and sensitivity of the model demonstrated the significance of improvement of vessel speed resolution. The vessel speed profiles derived were applied to the ship emission estimation. Based on maritime emission inventory developed with activity-based approach in the current study, the total ship emissions from OGVs in 2007 were 17097, 8190, and 1035 tonnes accounting for 17%, 11%, and 16% of total emissions of NOx, SO₂, and PM₁₀ in Hong Kong, respectively. From the emission spatial allocation, the shipping route along the East Lamma Channel and the berthing location of the Kwai Chung and Tsing Yi Container Port were the regions with the highest emissions. The OGV emissions in Hong Kong contributed 0.07% NOx, 0.05% SO₂, and 0.06% PM₁₀ out of the global total shipping emissions in 2007. Fine particulates (PM₂.₅) was collected near the Kwai Chung and Tsing Yi Container Terminals (KTCT) during the two study periods, i.e., (1) 14 August to 2 October 2009 for summer and (2) 26 January to 1 March 2010 for winter. The average PM₂.₅ concentration was 30.5 μg/m³. The chemical composition of the PM₂.₅ collected was characterized. The dominant species was determined to be sulfate (34%), followed by organic matter (19%) and elemental carbon (12%). The major PM₂.₅ sources, with particular emphasis on those associated with ship emissions, were identified using positive matrix factorization (PMF). The emissions of residual oil combustion and marine diesel oil combustion from ship engines contributed 12% (3.6 μg/m³) and 7% (2.3 μg/m³) of the total PM₂.₅ in the area near KTCT. The secondary sulfate associated with ship emission was determined, and its contribution to PM₂.₅ was 6% (1.8 μg/m³). Together with the primary ship emissions, the total ambient PM₂.₅ mass associated with ship emissions at the sampling site was 7.6 μg/m³ (25%).<br/><br/>Description: xiii, 182 leaves : ill. (some col.), col. maps ; 30 cm.; PolyU Library Call No.: [THS] LG51 .H577P CEE 2012 Yau