查看更多>>摘要：Experimental tests were conducted on one-third-scale outrigger knee joint specimens to define the vulnerabilities of existing outrigger bents under seismic in-plane loading and to develop appropriate retrofit measures to address the identified vulnerabilities. The specimens incorporated deficiencies present in the outrigger knee joints in the WA-99 Spokane Street overcrossing in western Washington State. The as-built specimens exhibited poor behavior with failure at low ductility levels because of shear distress and reinforcement bond failures within the joint. Threshold principal tension stress values describing the expected condition of the joints were established and compared with values obtained by other researchers. Elbow-shaped circular steel jacketing around the joint and beam region was used to retrofit the as-built specimens. The retrofitted specimens formed a plastic hinge in a gap introduced at the top of the column with improved ductility and energy dissipation capacities when compared to the behavior of similar as-built specimens. Retrofitted outrigger knee joint systems can be expected to achieve ductility levels of at least 5 as well as drift capacities exceeding 6%.
查看更多>>摘要：The 20-km (12.5-mi) mass rapid transit underground railway system in central Bangkok, Thailand, recently opened for passengers. During construction, the project was divided into two separate civil design-build contracts: the northern section, comprising approximately 10 km (6.2 mi) of twin bored tunnels, and nine stations constructed within slurry walls by adopting top-down techniques. A crucial part of the design of the underground structures was the selection of appropriate design parameters for the slurry walls. The contractor was responsible for ground-related issues and carried out a detailed site investigation to confirm the ground conditions and define soil parameters for the design of the underground structures. The site investigation comprised 40 conventional wash-bored borings and six self-boring pressuremeter tests. This paper describes the site investigation that was carried out for the project and the ground conditions that were encountered, with particular focus on the use of the self-boring pressuremeter to estimate the soil strength, stiffness, and in situ pressure for use in design of the slurry walls. The paper discusses the various methods used to interpret the data and compares the parameters derived from the pressuremeter to those derived from other methods and from back-analysis of the behavior of the wall during construction. It is concluded that in the conditions in Bangkok, the pressuremeter testing provided higher strength and stiffness values than determined from other methods and that these parameters were subsequently borne out by the behavior of the underground structures.
查看更多>>摘要：Corrugated high-density polyethylene (HDPE) pipe 36 in. (900 mm) in diameter was evaluated for its stress crack resistance with the notched constant ligament stress test (ASTM F 2136). Test specimens were taken directly from the pipe liner to include the processing effects. In addition to the standard test condition of 10% Igepal solution at 50℃, tests were performed in water and air at temperatures of 60°, 70°, and 80℃. The test data were analyzed with the ISO 9080 method to define the transition point and ductile-to-brittle curve. The results indicate that the 10% Igepal solution greatly accelerates the stress cracking process, whereas the stress cracking behavior in water and in air is aggressive and practically the same. Activation energies in both ductile and brittle portions of the curve are in general agreement with the literature for HDPE resins. The results indicate that the rate processing method is an accurate model with which to extrapolate data from elevated test temperatures to lower service temperatures. However, Popelar's shift method tends to overestimate the failure times.
查看更多>>摘要：Although bridges are a highly visible and crucial part of the highway infrastructure, smaller structures typically classified as culverts exist in even greater numbers. Nearly invisible to the public, culverts are crucial components of highways. Failure of culverts can lead to flooding, roadway damage, interruption of traffic, and even fatal accidents. Several states have implemented successful culvert inspection programs, but others are only beginning to formalize their culvert inspection and maintenance. Even after periodic inspection programs are in place, planners need a tool for consistent guidance to identify structures most in need of attention. This paper reports on a simple rating system based on a new culvert inspection program recently implemented by the Indiana Department of Transportation. The rating system uses weighting factors that can be adjusted by the user to provide an overall rating of a culvert based on ratings of specific characteristics of a culvert. The tool can be used to provide a consistent comparison with other culverts across the state and to provide quality control of the inspectors' overall rating as entered into a database.
Yoon-Si LeeTerry J. WipfBrent M. PharesF. Wayne Klaiber...
p.233-244页
查看更多>>摘要：This project investigated the effectiveness of carbon fiber-reinforced polymer (CFRP) composite materials to strengthen an existing, structurally deficient steel girder bridge. The bridge selected for strengthening with the CFRP posttensioning system is a three-span continuous steel stringer bridge on IA-141 approximately 1.6 mi west of Bayard, Iowa. The research program consisted of several tasks, and the main emphasis was the installation of the strengthening system and associated field testing. The bridge was instrumented to measure strain at selected critical locations and tested before installation of the posttensioning system, shortly following posttensioning, and after approximately 1 and 2 years of service to assess changes in behavior resulting from the addition of the posttensioning system and time. During the application of the posttensioning strengthening system, strain was measured to investigate the response of the bridge to the applied posttensioning forces. After the last follow-up test was completed, the posttensioning force was removed (and reapplied) to investigate any loss of posttensioning force that may have occurred during the 2-year period. In general, the installation of the posttensioning system required no special equipment or training other than access equipment, an acetylene torch to remove a portion of several diaphragms, and a hydraulic jack. A three-person crew was able to install the system in just over 1 day. On the basis of an analysis performed by using an HS-20 truck, it was found that the posttensioning strengthening system reduced the dead and live load induced moments by approximately 3% to 5%, allowing the bridge to carry additional live load.
Mahmut EkenelNestore GalatiJohn J. MyersAntonio Nanni...
p.245-251页
查看更多>>摘要：Carbon fiber-reinforced polymer (CFRP) composites have been used in a wide range of application areas in bridge rehabilitations because these materials are less affected by corrosive environmental conditions, are known to provide longer life, and require less maintenance. However, the quality control and quality assessment of these new rehabilitation systems should be further improved and standardized. A recent rehabilitation project that used CFRP laminates was done on a bridge in Dallas County, Missouri, by the Missouri Department of Transportation and the Center for Infrastructure Engineering Studies at the University of Missouri-Rolla. The acousto-ultrasonic nondestructive testing technology was performed to detect and image surface defects in the form of delaminations. These were intentionally formed at the CFRP sheet-concrete interface to investigate the ability of this technique. Acousto-ultrasonic nondestructive testing has shown the ability to detect and image the delaminations between CFRP sheet and concrete substrate.
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