PRE-COMPRESSED CONCRETE-FILLED STEEL TUBE FOR HIGH EARTHQUAKE RESISTING PERFORMANCE OF STEEL COLUMNS

Strength of the circular-shaped concrete-filled steel tubes (CFT) is enhanced significantly due to the confinement provided by the surrounding steel plates. The effectiveness of the confinement depends on several factors such as column slenderness，diameter to thickness ratio，strengths of steel and concrete，the loading method and boundary conditions，and the interface condition between steel and intemal concrete. A new technique is introduced in this study to increase the effectiveness of the confinement in order to improve the strength and the ductility of CFT columns. The CFT column used in this study is different from the conventional CFT column in that the concrete is compressed prior to hardening using two circular steel plates placed at both ends of the column

Concrete Filled Steel Tubes for Performance Improvement of Steel Truss Bridges

Abstract: The use of concrete-filled steel tubes (CFST) in engineering structures has become popular because of their excellent seismic resistance structural properties such as high strength, high ductility and large energy absorption capacity. In CFSTs the surrounding steel tube provides effective confinement to the filled-in concrete and in turn the concrete helps to reduce the potential local buckling of the steel tube resulting improved seismic resistant performance. This study aimed at investigating the benefit of CFST members in railway steel truss bridges susceptible to earthquake loads. Since the end frames of truss bridges are mainly subjected to compressive loads CFST is a good alternative for end raker. The steel weight of the rib can be reduced with CFST and hence the method is economically sound. The seismic behaviour of steel truss bridges with steel and CFST end rakers is discussed based on the results of nonlinear time history analyses. Five truss bridges were designed with different types of end rakers namely existing HEB end raker, square hollow end raker, three square hollow CFST end raker bridges with varying concrete grades. Time history analyses were performed for transverse direction using selected past earthquakes and natural frequencies, maximum vertical and lateral deflections, residual vertical and lateral deflections and member stresses were checked. It was found that the use of CFST in steel truss bridges can be effectively utilized to improve the seismic resisting performance

Dependence on seagrass fisheries governed by household income and adaptive capacity

Seagrass meadows, like other tropical coastal ecosystems, are highly productive and sustain millions of people worldwide. However, the factors that govern the use of seagrass as a fishing habitat over other habitats are largely unknown, especially at the household scale. Using socioeconomic factors from 147 villages across four countries within the Indo-Pacific, we examined the drivers of household dependence on seagrass. We revealed that seagrass was the most common habitat used for fishing across villages in all the countries studied, being preferred over other habitats for reliability. Using structural equation modelling, we exposed how household income and adaptive capacity appears to govern dependence on seagrass. Poorer households were less likely to own motorboats and dependent on seagrass as they were unable to fish elsewhere, whereas wealthier households were more likely to invest in certain fishing gears that incentivised them to use seagrass habitats due to high rewards and low effort requirements. Our findings accentuate the complexity of seagrass social-ecological systems and the need for empirical household scale data for effective management. Safeguarding seagrass is vital to ensure that vulnerable households have equitable and equal access to the resource, addressing ocean recovery and ensuring sustainable coastal communities