International Journal of Sustainable Materials and Structural Systems (4 papers in press)
Experimental and Numerical Study on the DADAS Dampers in Steel Frame Structure
by Faezeh Nejati, Mahmood Hosseini, Amir Mahmoudzadeh
Abstract: In this study, a structural system with seesaw motion with respect to a central massive support has been considered for steel buildings with square plan, and the bottom ends of the all circumferential columns at the lowest story have been equipped with Double-ADAS (DADAS) dampers, which dissipate a great portion of the seismic input energy. The hysteretic behavior of DADAS dampers has been investigated by using finite element analysis. At first a set of regular steel multistory buildings with 5 stories have been designed based on the conventional code provisions. Then, the structures of the designed buildings have been changed into the structure with seesaw motion by using, at the base level of the building, a massive central column, eliminating other middle columns, and equipping circumferential columns with DADAS dampers. The damper is modeled at structural laboratory of Earthquake Engineering Research Institute in small scale and tested under harmonic loaded. Experimental results show the proper conduct of the damper prototype is under load. To show the efficiency of the proposed structural system and dampers, a series of nonlinear time history analysis (NLTHA) were performed by using a set of 3-component acceleration of some selected earthquakes. Numerical results of NLTHA show that the proposed rocking structures can efficiently decrease the seismic damage in the building.
Keywords: Double-ADAS Damper (DADAS); Experimental Study; Finite Element Modeling; Nonlinear Time History Analysis; Seesaw Motion of Structures.
Modern Methods of Railway Track Safety Inspection
by Ta-Lun Yang, Wael A. Altabey
Abstract: Railway and transit tracks are designed and constructed as smooth segments of straight lines and circular curves linked by transitional spirals. Dynamic traffic loads, material wear and environmental cycles gradually produce deviations in the track from the original smooth geometry. Such deviations lead to rough ride in the vehicles and furthermore higher dynamic vehicle-track interaction forces which lead to faster deviation growth. To monitor the geometric condition of the track and to guide maintenance and repair, hand tools were used to take consecutive measurements by track walkers. Modern state-of-the-art technology has since replaced the traditional slow and painful measurement practice. Inspections are now done from a moving vehicle at hundreds of km per hour without contacting the track. All track geometry parameters are measured up four times per meter; data are analyzed in real time by onboard software to identify the location and magnitudes of deviations which exceeds the acceptable tolerance. Historical measurements are stored in data bases which are used to establish degradation trends and to guide the planning of maintenance. With the help of high-speed imaging technology, automated video inspection systems are installed on some vehicles to detect other faults in the track structure. Four types of such modern inspection tools are introduced in the paper presentation. These are: a single-car comprehensive inspection vehicle; a dedicated inspection train; a highway-railway dual usage truck and an unmanned inspection system. Actual operational systems are used as examples to illustrate the design and capabilities of each of these types of inspection tools.
Keywords: Railway and transit tracks; vehicles; Track structure; Dynamic traffic loads; Inspections; Imaging technology; Video inspection systems.
A Review Study on Preparation and Application of Microencapsulated Phase Change Materials
by Min Li, Boyuan Mu, Wael A. Altabey
Abstract: Microencapsulated phase change materials have better thermal stability, and are widely used in the field of energy storage. In this paper, the core and wall material characteristics of microencapsulated phase change materials are reviewed. Several preparation methods, such as in-situ polymerization, interfacial polymerization, and suspension-like polymerization, are analyzed and the applications of microencapsulated phase change materials in fiber fabric, building, military camouflage and heat conduction are summarized.
Keywords: phase change materials; microcapsules; energy storage; application.
Spatially continuous fully distributed microwave-photonic and coaxial cable sensors for structural health monitoring
by Baokai Cheng, Liwei Hua, Wenge Zhu, Hai Xiao
Abstract: All nations in the world are facing tremendous pressure from their aging civil infrastructures. The potential catastrophic failure and collapse of these large size civil structures would bring devastating impacts on the economy and human lives. Structural health monitoring (SHM) has been proven effective to prevent catastrophic failures. However, most engineered structures are large in dimension, complex in geometry and heterogeneous in materials. Comprehensive evaluation of the health status of the structure as a whole prefers distributed sensing to provide spatially-uninterrupted information along the entire span of the structure. Current distributed sensing technologies still have difficulty to meet the combined requirements. There is a continuing need for innovations in distributed sensing technologies to ensure the safe operation of various infrastructures. This report summarizes our recent research progresses in developing new distributed sensing technologies for SHM based on the new microwave-photonic and coaxial cable platforms. The two new platforms have the combined advantages of high measurement resolution, large strain capability, long span of coverage, easy-to-install/embed, spatial continuity (no dark zones), and flexible gauge lengths. The new distributed sensing technology may bring a revolutionary tool to address a number of insufficiently-studied areas in SHM, such as distributed monitoring of cracks and corrosion, post seismic monitoring to ensure mission-critical services in disaster responses and emergency evacuations, study of the progressive structural failures/collapses under extreme loads, and high performance smart structures.
Keywords: Distrubuted sensor; microwave-photonics; coaxial cable; structure health monitoring.