Accelerated bridge construction (ABC) is gaining substantial momentum in the US because of its many advantages. Extensive use of precast members is necessary for ABC to succeed. Some of the key advantages of ABC are: (1) higher quality of construction for structural elements because of fabrication in plants, (2) more durable materials because of more appropriate curing in plants, (3) concurrent execution of different tasks, (4) reduced traffic interruption and less risk to the traveling public and construction crew, and (5) reduced direct and indirect effect on the environment due to expedited construction and the use of more efficient technologies that require less energy. Despite their numerous advantages prefabricated columns have rarely been used in areas of high seismicity because of high uncertainty about their seismic performance.
Summary
Hinge or “pin” connections may be used in integral bridges to connect columns to pile shafts to reduce the foundation force demand. Used in combination with prefabricated columns, pins facilitate accelerated bridge construction (ABC). These innovative methods could improve the quality and economy of project compared with conventional construction in seismic regions. This study developed pipe pins that reduce moment transfer between the column and pile shaft under seismic excitations. The pipe pins consist of two steel pipes and a rod that transfer shear and tension while allowing rotation between the column and shaft. The primary objective of this research was to investigate the seismic performance and develop design guidelines of column‐to‐pile shaft pipe pins for cast‐in‐place and precast constructions. This research was composed of experimental and analytical studies. The experimental portion of the study consisted of testing of a large‐scale bent model subjected to seismic loadings. The test results confirmed that the proposed design method meets the safety and performance requirements of the codes under seismic loadings. The pins maintained structural integrity with minimal damage, while the columns reached the full plastic hinge capacity. The analytical studies consisted of (a) a simple stick model to be used as a design tool, (b) a finite element model (FEM) for global analysis of bridges, and (c) an elaborate FEM to investigate the microscopic performance and interaction of the components. The analytical models were subsequently used in parametric studies.
Cu-Al-Mn (CAM) shape memory alloys (SMA) are cost effective, have a high low-cycle fatigue life and superelastic limit, and a wide temperature application range compared to other types of SMAs. These characteristics of CAM SMAs have resulted in an increased research interest in their use in civil engineering applications, particularly as reinforcement in concrete structures, and dampers in steel structures. However, these applications could require machining of the CAM SMA bars for connecting with other structural elements. This study presents the methods and results of the first systematic research on the machinability of CAM SMAs. The key machinability characteristics of CAM SMAs, such as chip formation, cutting temperature, tool wear, workpiece surface roughness and diameter deviation were studied and compared with conventional NiTi SMAs, and commonly used steel: mild steel (MS) and 304 stainless steel (SS). Effects of a wide range of cutting parameters, such as cutting speed ranging from 15 to 120 m/min, feed rate ranging from 0.1 to 0.2 mm/rev, and depth of cut ranging from 0.5 to 1.5 mm, were investigated. The results from this study demonstrated that the tool wear from machining CAM SMAs was close to that of SS and slightly higher than that from machining MS but much lower than of that from machining NiTi SMAs. In all the cases considered here, the tool wear from machining CAM SMAs was found to be 0.6 to 1.8 times that from machining SS, 0.8 to 2.4 times that from machining MS, and 1/7 to 1/21 times that from machining NiTi SMAs. After a continuous machining test with a total cutting length of 4.5 m, the nose wear of machining CAM SMAs was found to be 1.6 times that of machining MS, and the average flank wear of machining CAM SMAs was found to be three times that of machining MS; the diameter deviation (relative diameter difference with the first sample) of CAM SMAs was only 10 mm larger than that of MS.
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