An analytical seismic fragility assessment framework is presented for the existing low strength reinforced concrete structures more common in the building stock of the developing countries.For realistic modelling of s...An analytical seismic fragility assessment framework is presented for the existing low strength reinforced concrete structures more common in the building stock of the developing countries.For realistic modelling of such substandard structures,low strength concrete stress-strain and bond-slip capacity models are included in calibrating material models.Key capacity parameters are generated stochastically to produce building population and cyclic pushover analysis is carried out to capture inelastic behaviour.Secant period values are evaluated corresponding to each displacement step on the capacity curves and used as seismic demand.A modified capacity demand diagram method is adopted for the degrading structures,which is further used to evaluate peak ground acceleration from back analysis considering each point on the capacity curve as performance point.For developing fragility curves,the mean values of peak ground acceleration are evaluated corresponding to each performance point on the series of capacity curves.A suitable probability distribution function is adopted for the secant period scatter at different mean peak ground acceleration values and probability of exceedance of limit states is evaluated.A suitable regression function is used for developing fragility curves and regression coefficients are proposed for different confidence levels.Fragility curves are presented for a low rise pre-seismic code reinforced concrete structure typical of developing countries.展开更多
In 2007,over 24 million tons of Construction and Demolition(C&D) wastes were generated in Hong Kong.Since the local landfills will be saturated in about 6 years,it is important to find a viable way to reuse these ...In 2007,over 24 million tons of Construction and Demolition(C&D) wastes were generated in Hong Kong.Since the local landfills will be saturated in about 6 years,it is important to find a viable way to reuse these waste materials as to alleviate the demand on public fill capacity.In order to tackle the problem,the Hong Kong government has set up a temporary recycling facility in Hong Kong in 2002 for producing different sizes of recycled aggregate for use in various construction materials.The Hong Kong Polytechnic University has been studying the feasible use of recycled aggregates in Hong Kong for a number of years.A substantial amount of experimental results on the properties of recycled aggregates and the effect of recycled aggregates on the properties of concrete and other construction products(e.g.concrete blocks and granular sub-base) has been published.In this paper,the experience of Hong Kong in using recycled aggregates are summarized and a set of quality control guidelines proposed for governing the use of recycled aggregates in Hong Kong is introduced.The experience and guidelines may also be useful for the recycling of waste materials derived from the recent Sichuan earthquake in China.展开更多
The objective in this study is to apply the sustainable chemistry and photo-thermal synthesis technology to produce the sustainable eco-superplasticiser for the sustainable high performance SCC concrete especially in ...The objective in this study is to apply the sustainable chemistry and photo-thermal synthesis technology to produce the sustainable eco-superplasticiser for the sustainable high performance SCC concrete especially in hot tropical countries. A photo-thermal synthesized eco-superplasticiser （PSES） was produced by using photo-thermal catalyst in a solar chemical reactor. In this preliminary study, an unique high early strength of SCC concrete has been successfully produced by imposing an unique proportion of the photo-thermal-synthesized eco- Superplasticiser （PSES）, local fly ash, sand and aggregate. The SCC concrete is preliminary tried in the precast concrete product to produce the complicated geometries as Tunnel segment, U-shape beam, and Box girder which have the critical reinforcement and thin section concrete. Surprisingly, this SCC provide the benefits as eliminating steaming energy, increased productivity, and minimize pollution. These unique properties of sustainable SCC concrete can not be achieved by the convention concrete by using ligno, naphthalene and melamine base superplasficiser. The synthesized sustainable eco-superplasticiser is a perfect choice to fully utilized the renewable energy and improve the concrete working environment.展开更多
The dynamic responses of the Tsing Ma suspension bridge and the running behaviors of trains on the bridge under turbulent wind actions are analyzed by a three-dimensional wind-train-bridge interaction model. This mode...The dynamic responses of the Tsing Ma suspension bridge and the running behaviors of trains on the bridge under turbulent wind actions are analyzed by a three-dimensional wind-train-bridge interaction model. This model consists of a spatial finite element bridge model, a train model composed of eight 4-axle identical coaches of 27 degrees-of-freedom, and a turbulent wind model. The fluctuating wind forces, including the buffeting forces and the self-excited forces, act on the bridge only, since the train runs inside the bridge deck. The dynamic responses of the bridge are calculated and some results are compared with data measured from Typhoon York. The runnability of the train passing through the Tsing Ma suspension bridge at different speeds is researched under turbulent winds with different wind velocities. Then, the threshold curve of wind velocity for ensuring the running safety of the train in the bridge deck is proposed, from which the allowable train speed at different wind velocities can be determined. The numerical results show that rail traffic on the Tsing Ma suspension bridge should be closed as the mean wind velocity reaches 30 m/s.展开更多
Modern Earthquake Risk Assessment（ERA） methods usually require seismo-tectonic information for Probabilistic Seismic Hazard Assessment（PSHA） that may not be readily available in developing countries. To bypass thi...Modern Earthquake Risk Assessment（ERA） methods usually require seismo-tectonic information for Probabilistic Seismic Hazard Assessment（PSHA） that may not be readily available in developing countries. To bypass this drawback, this paper presents a practical event-based PSHA method that uses instrumental seismicity, available historical seismicity, as well as limited information on geology and tectonic setting. Historical seismicity is integrated with instrumental seismicity to determine the long-term hazard. The tectonic setting is included by assigning seismic source zones associated with known major faults. Monte Carlo simulations are used to generate earthquake catalogues with randomized key hazard parameters. A case study region in Pakistan is selected to demonstrate the effectiveness of the method. The results indicate that the proposed method produces seismic hazard maps consistent with previous studies, thus being suitable for generating such maps in regions where limited data are available. The PSHA procedure is developed as an integral part of an ERA framework named EQRAM. The framework is also used to determine seismic risk in terms of annual losses for the study region.展开更多
In this paper seven of the ten Water Control Zones(WCZs)in Hong Kong's coastal waters with monthly or bi-weekly sampling data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to...In this paper seven of the ten Water Control Zones(WCZs)in Hong Kong's coastal waters with monthly or bi-weekly sampling data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to analyze the spatial and temporal variations of chlorophyll-a and its influencing factors.Cluster analysis was employed to group the monitoring stations based on the structure of the data set.Multiple step regression was employed to determine the significant influencing factors of chlorophyll-a level.The results suggest that all the monitoring stations could be grouped into two clusters.ClusterⅠwith frequent red tide incidents comprises two WCZs which are semi-enclosed bays.ClusterⅡwith less red tide occurrence comprises the other five WCZs in an estuarine environment in the west.For both clusters,the organic contents indicator,BODS,was a common significant influencing factor of the chlorophyll-a level.Nitrogen and light penetration condition related to turbidity,total volatile solids and suspended solids had more influence on the cholophyll-a level in ClusterⅠthan in ClusterⅡ,while phosphorus and oceanographic conditions associated with salinity,temperature,dissolved oxygen and pH were more important in ClusterⅡthan in ClusterⅠ.Generally,there was a higher average chlorophyll-a level in winter and autumn in a year.The chlorophyll-a level was much higher in ClusterⅠthan in ClusterⅡamong all seasons.Although the chlorophyll-a concentration had great variations from place to place in Hong Kong's coastal waters,it seemed to have a common long term fluctuation period of 8-10 years with a high-low-high variation in the period in the whole region,which might be influenced by other factors of global scale.展开更多
基金financial support provided by the Overseas Research Student (ORS) award scheme of the Vice-Chancellors committee of the United Kingdom's universities as well as the A.G. Leventis Foundation
文摘An analytical seismic fragility assessment framework is presented for the existing low strength reinforced concrete structures more common in the building stock of the developing countries.For realistic modelling of such substandard structures,low strength concrete stress-strain and bond-slip capacity models are included in calibrating material models.Key capacity parameters are generated stochastically to produce building population and cyclic pushover analysis is carried out to capture inelastic behaviour.Secant period values are evaluated corresponding to each displacement step on the capacity curves and used as seismic demand.A modified capacity demand diagram method is adopted for the degrading structures,which is further used to evaluate peak ground acceleration from back analysis considering each point on the capacity curve as performance point.For developing fragility curves,the mean values of peak ground acceleration are evaluated corresponding to each performance point on the series of capacity curves.A suitable probability distribution function is adopted for the secant period scatter at different mean peak ground acceleration values and probability of exceedance of limit states is evaluated.A suitable regression function is used for developing fragility curves and regression coefficients are proposed for different confidence levels.Fragility curves are presented for a low rise pre-seismic code reinforced concrete structure typical of developing countries.
文摘In 2007,over 24 million tons of Construction and Demolition(C&D) wastes were generated in Hong Kong.Since the local landfills will be saturated in about 6 years,it is important to find a viable way to reuse these waste materials as to alleviate the demand on public fill capacity.In order to tackle the problem,the Hong Kong government has set up a temporary recycling facility in Hong Kong in 2002 for producing different sizes of recycled aggregate for use in various construction materials.The Hong Kong Polytechnic University has been studying the feasible use of recycled aggregates in Hong Kong for a number of years.A substantial amount of experimental results on the properties of recycled aggregates and the effect of recycled aggregates on the properties of concrete and other construction products(e.g.concrete blocks and granular sub-base) has been published.In this paper,the experience of Hong Kong in using recycled aggregates are summarized and a set of quality control guidelines proposed for governing the use of recycled aggregates in Hong Kong is introduced.The experience and guidelines may also be useful for the recycling of waste materials derived from the recent Sichuan earthquake in China.
文摘The objective in this study is to apply the sustainable chemistry and photo-thermal synthesis technology to produce the sustainable eco-superplasticiser for the sustainable high performance SCC concrete especially in hot tropical countries. A photo-thermal synthesized eco-superplasticiser （PSES） was produced by using photo-thermal catalyst in a solar chemical reactor. In this preliminary study, an unique high early strength of SCC concrete has been successfully produced by imposing an unique proportion of the photo-thermal-synthesized eco- Superplasticiser （PSES）, local fly ash, sand and aggregate. The SCC concrete is preliminary tried in the precast concrete product to produce the complicated geometries as Tunnel segment, U-shape beam, and Box girder which have the critical reinforcement and thin section concrete. Surprisingly, this SCC provide the benefits as eliminating steaming energy, increased productivity, and minimize pollution. These unique properties of sustainable SCC concrete can not be achieved by the convention concrete by using ligno, naphthalene and melamine base superplasficiser. The synthesized sustainable eco-superplasticiser is a perfect choice to fully utilized the renewable energy and improve the concrete working environment.
基金National Natural Science Foundation of China Under Grant No.90715008, 50838006The Fundamental Research Funds for the Central Universities Under Grant No 2009JBM078
文摘The dynamic responses of the Tsing Ma suspension bridge and the running behaviors of trains on the bridge under turbulent wind actions are analyzed by a three-dimensional wind-train-bridge interaction model. This model consists of a spatial finite element bridge model, a train model composed of eight 4-axle identical coaches of 27 degrees-of-freedom, and a turbulent wind model. The fluctuating wind forces, including the buffeting forces and the self-excited forces, act on the bridge only, since the train runs inside the bridge deck. The dynamic responses of the bridge are calculated and some results are compared with data measured from Typhoon York. The runnability of the train passing through the Tsing Ma suspension bridge at different speeds is researched under turbulent winds with different wind velocities. Then, the threshold curve of wind velocity for ensuring the running safety of the train in the bridge deck is proposed, from which the allowable train speed at different wind velocities can be determined. The numerical results show that rail traffic on the Tsing Ma suspension bridge should be closed as the mean wind velocity reaches 30 m/s.
文摘Modern Earthquake Risk Assessment（ERA） methods usually require seismo-tectonic information for Probabilistic Seismic Hazard Assessment（PSHA） that may not be readily available in developing countries. To bypass this drawback, this paper presents a practical event-based PSHA method that uses instrumental seismicity, available historical seismicity, as well as limited information on geology and tectonic setting. Historical seismicity is integrated with instrumental seismicity to determine the long-term hazard. The tectonic setting is included by assigning seismic source zones associated with known major faults. Monte Carlo simulations are used to generate earthquake catalogues with randomized key hazard parameters. A case study region in Pakistan is selected to demonstrate the effectiveness of the method. The results indicate that the proposed method produces seismic hazard maps consistent with previous studies, thus being suitable for generating such maps in regions where limited data are available. The PSHA procedure is developed as an integral part of an ERA framework named EQRAM. The framework is also used to determine seismic risk in terms of annual losses for the study region.
基金National Natural Science Foundation of China,No.47176032
文摘In this paper seven of the ten Water Control Zones(WCZs)in Hong Kong's coastal waters with monthly or bi-weekly sampling data of 17 parameters collected at 37 monitoring stations from 1988 to 1999 were selected to analyze the spatial and temporal variations of chlorophyll-a and its influencing factors.Cluster analysis was employed to group the monitoring stations based on the structure of the data set.Multiple step regression was employed to determine the significant influencing factors of chlorophyll-a level.The results suggest that all the monitoring stations could be grouped into two clusters.ClusterⅠwith frequent red tide incidents comprises two WCZs which are semi-enclosed bays.ClusterⅡwith less red tide occurrence comprises the other five WCZs in an estuarine environment in the west.For both clusters,the organic contents indicator,BODS,was a common significant influencing factor of the chlorophyll-a level.Nitrogen and light penetration condition related to turbidity,total volatile solids and suspended solids had more influence on the cholophyll-a level in ClusterⅠthan in ClusterⅡ,while phosphorus and oceanographic conditions associated with salinity,temperature,dissolved oxygen and pH were more important in ClusterⅡthan in ClusterⅠ.Generally,there was a higher average chlorophyll-a level in winter and autumn in a year.The chlorophyll-a level was much higher in ClusterⅠthan in ClusterⅡamong all seasons.Although the chlorophyll-a concentration had great variations from place to place in Hong Kong's coastal waters,it seemed to have a common long term fluctuation period of 8-10 years with a high-low-high variation in the period in the whole region,which might be influenced by other factors of global scale.
