A review on application of composite truss bridges composed of hollow structural section members

Composite truss with hollow structural section(HSS) members is deemed as the structure applicable to large-span and heavily-loaded bridges. To promote the application of composite truss bridge with HSS members in China, this paper described its structural characteristics and technology in details. Besides, not only were 32 typical design cases of composite truss bridges with HSS members collected, but also the corresponding historical development was summed up. Comparisons on structural components, characteristics and engineering applications were made among composite truss bridges with HSS members in different structural forms. Then, the analysis on the characteristics of composite truss bridges with concrete-filled steel tubular(CFST) chords was conducted, and the challenges on the aspects of complicated joints and interfacial debonding were pointed out. To address these problems, the concrete-filled rectangular hollow section(CFRHS)stiffened with PBLs(Perfobond Ribs) was proposed to improve the reliability of confinement effect in CFST member and force transfer in joints. The advantages on the mechanical properties of CFRHS structure stiffened using PBLs were systematically expounded with respect to the behaviors of steel plate, interface, member and joint. Moreover, the structure design, construction technology, structural calculation and economic efficiency of the practical bridge with CFRHS chords stiffened using PBLs were comprehensively analyzed.The results demonstrated that composite truss bridge with PBL-stiffened CFRHS members was competitive in mechanical performance and construction.

Towards a better recording of microtubule cytoskeletal spatial organization and dynamics in plant cells

Numerous fluorescent marker lines are currently available to visualize microtubule(MT)architecture and dynamics in living plant cells, such as markers expressing p35S::GFP-MBD or p35S::GFP-TUB6.However, these MT marker lines display obvious defects that affect plant growth or produce unstable fluorescent signals. Here, a series of new marker lines were developed, including the pTUB6::VisGreen-TUB6-expressing line in which TUB6 is under the control of its endogenous regulatory elements and e GFP is replaced with VisGreen, a brighter fluorescent protein. Moreover, two different markers were combined into one expression vector and developed two dual-marker lines.These marker lines produce bright, stable fluorescent signals in various tissues, and greatly shorten the screening process for generating dual-marker lines.These new marker lines provide a novel resource for MT research.

Vehicle-bridge coupled vibrations in different types of cable stayed bridges

Numerical analyses of the coupled vibrations of vehicle-bridge system and the effects of different types of cable stayed bridges on the coupled vibration responses have been presented in this paper using ANSYS. The bridge model and vehicle model were independently built which have no internal relationship in the ANSYS. The vehicle-bridge coupled vibration relationship was obtained by using the APDL program which subsequently imposed on the vehicle and bridge models during the numerical analysis. The proposed model was validated through a field measurements and literature data. The judging method, possibility, and criterion of the vehicle-bridge resonance （coupled vibrations） of cable stayed bridges （both the floating system and half floating system） under traffic flows were presented. The results indicated that the interval time between vehicles is the main influence factor on the resonance excitation frequency under the condition of equally spaced traffic flows. Compared to other types of cable stayed bridges, the floating bridge system has relatively high possibility to cause vehicle-bridge resonance.