Click for next page ( 49


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 48
48 CHAPTER 4 CONCLUSIONS AND SUGGESTED RESEARCH CONCLUSIONS native solutions that do not require wires or cables would be preferable. This research resulted in improved deployment, position- ing, and data collection procedures for portable scour monitor- ing work. These improvements will facilitate data collection Rigid Frame Deployment of a Kneeboard under adverse conditions and will allow more successful mon- itoring at a wide range of bridges under flood flow conditions. Further research and development on the kneeboard con- The research was conducted recognizing the need to provide cept deployed on a rigid frame would be valuable. As devel- solutions that are easily used and affordable by state and local oped, the kneeboard on a rigid frame was able to facilitate bridge owners. data collection on bridges with projecting decks and/or large The research completed did not include work directed overhangs. However, there were deployment issues related toward new measurement technology, but concentrated on to getting the kneeboard on the water surface and maintain- improved deployment methods. The proposed solution, as ing a stable platform for measurement. The conclusion was developed in the articulated arm truck, did not meet all the that a rigid frame deployment of a kneeboard was viable, but identified criteria defined for this research. In particular, the an alternative floating platform might work better. research did not solve the measurement problems with debris A kneeboard works well on a tether, and the larger surface and ice. However, the research did solve some difficult imple- area is necessary under those conditions to keep the board mentation problems and provided improvement over current upright. However, on a rigid frame it is not necessary to have practice in flood flow monitoring. The resulting product will as much flotation, and a different board or floating system be beneficial to bridge inspectors and should greatly improve might work better. One idea is a pontoon-style system with a their ability to get reasonable results under adverse conditions. stabilizing fin between the pontoons that locates the trans- ducer under water 6 to 12 inches and also provides direc- tional stability. Alternatively, the transducer could simply be SUGGESTIONS FOR FURTHER RESEARCH mounted on a rigid, horizontal frame submerged under water without flotation. Although this research produced a reliable, fully functional articulated arm device, improvements could be made to the device, and other areas of research and development would Angular Measurement of Rotator further improve the ability to make flood flow measurements. The rotator at the end of the crane was included to provide the ability to rotate a sensor deployed at the end of the crane. Physical Probing Attachment The angle of rotation was measured with a 10-turn poten- tiometer. Mounting this sensor on the rotator required sig- A physical probe was fabricated from Schedule 80 stainless nificant fabrication, and the 10-turn potentiometer was not steel pipe that could be used for point measurements of scour as robust or durable as the other sensors included to monitor hole conditions. Knowing the location of the end of the crane, crane position. these point measurements could be completed with accurate An improved sensor arrangement for measuring the posi- positioning. The primary limitation of the probe was that it tion of the rotator would be desirable if the concept of a knee- could be used only in gravel/cobble beds or around piers with board on a rigid frame is pursued further. The rigid frame riprap, because the strength of the crane hydraulics would deployment of the kneeboard was ultimately the only appli- drive the probe into the bed in softer materials. Given this con- cation that required rotational ability. For example, rotational cern, a sensor at the end of the physical probe would be bene- ability was not necessary for the streamlined probe concept, ficial to help identify the water sediment interface. Such a after it was modified to allow it to rotate and track the cur- sensor might be as simple as a pressure switch; however, alter- rent on its own. It was also not necessary for any of the cable-

OCR for page 48
49 suspended operations. The tilt ability at the end of the crane However, this work concentrated on direct sonar measurement (as provided with the additional hydraulics that were added to with the streamlined probe and the kneeboard deployment the crane) was a desirable and necessary improvement. How- on a rigid framework. These programs were fully developed ever, the additional capability to rotate and to measure that and field-tested and are believed to be fairly robust software rotation added significant cost and complexity to the crane. packages. Therefore, without additional research and development to The cable-suspended program and the physical probing make the kneeboard concept more functional, the crane design did not receive the same level of development and testing. and construction could be simplified by eliminating the rota- They were developed to a prototype level, but did not receive tor and its measurement. the same degree of field testing as the other programs. Devel- oping fully functional software that is thoroughly de-bugged Alternative Positioning Systems is a time-consuming process that requires extensive testing. Additional testing and development of these two pieces of The calculation of the location of the end of the crane was software would provide greater confidence in their operation based on assorted tilt and displacement sensors, along with a and use. surveyor's wheel to locate the truck on the bridge deck. This system worked well. With the exception of the rotator mea- surement, as discussed above, the sensors selected were fairly Remote Control Boat simple and robust. The computer software was designed to complete all the geometric calculations necessary to define The use of an unmanned, remote control boat offers several crane location, without any direct operator involvement. advantages for flood monitoring, including safety, access However, this approach did create a system of multiple issues, measurement anywhere around or under the bridge, and components that required a certain electronic aptitude to oper- the ability to work at both low- and high-clearance bridges. ate and maintain. A simpler positioning system involving fewer Previous research has been completed on the use of remote components, such as the low-cost GPS concept explored dur- control boats for scour and stream gaging work, involving the ing the research, might be preferable if the required accuracy use of both gas and electric propulsion systems. Ultimately, was possible. Therefore, as GPS technology continues to im- the hull and the propulsion system should be designed around prove, an alternate positioning system based on GPS might be the payload that must be carried, and, using the wireless sonar possible. Another approach could involve proximity sensors developed as part of this project, the payload requirements located on the bridge a fixed distance ahead and behind the would be relatively small. Other areas of concern include devel- truck to track the movement of the crane arm. Additional re- oping a boat durable enough to survive the potential rough search might identify other methods as well, with the intent water, debris, and difficult operational conditions. This would being to reduce the number of sensors and calculations neces- require ruggedized servos and controllers mounted in water- sary to track the movement of the crane arm. proof compartments. The use of an unmanned remote control boat for scour mon- Additional Software Development itoring was identified during the literature review in Phase I. Although this concept was not pursued as part of this research Extensive effort was put into creating a software package to project, it is still a viable concept that should be investigated automate the data collection process with the articulated arm. further.