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The purpose of this paper is to further validate a wireless sensor system developed at Clarkson University for structural monitoring of highway bridges. The particular…
The purpose of this paper is to further validate a wireless sensor system developed at Clarkson University for structural monitoring of highway bridges. The particular bridge monitored employs a fiber reinforced polymer (FRP) panel system which is fairly innovative in the field of civil engineering design. The superstructure was monitored on two separate occasions to determine a change in structural response and see how the structural system performs over time.
A series of wireless sensor units was deployed at various locations of the steel superstructure, to measure both the modal response from acceleration measurements as well as quasi‐static and dynamic strain response. Ambient and forced loading conditions were applied to measure the response. Data results were compared over two separate periods approximately nine months apart.
The first eight mode shapes were produced from output‐only system identification providing natural frequencies ranging from approximately 6 to 42 Hz. The strain response was monitored over two different testing periods to measure various performance characteristics. Neutral axis, distribution factor, impact factor and end fixity were determined. Results appeared to be different over the two testing periods. They indicate that the load rating of the superstructure decreased over the nine month period, possibly due to deterioration of the materials or composite action.
The results from the two testing periods indicate that further testing needs to be completed to validate the change in response. It is difficult to say with certainty that the significant change in response is due to bridge deterioration and not other factors such as temperature effects on load rating. The sensor system, however, proved to provide high quality data and responses indicating its successful deployment for load testing and monitoring of highway infrastructure.
The paper provides a depiction of the change in structural behavior of a bridge superstructure using a wireless sensor system. The wireless system provided high‐rate data transmission in real time. Load testing at two different points in time, eight months apart, showed a significant change in bridge behavior. The paper provides a practical and actual physical load test and rating during these two periods for quantifiable change in response. It is shown that the wireless system is capable of infrastructure monitoring and that possible deterioration is expected with this particular bridge design. Additionally, the load testing occurred during different seasons, which could create cause for temperature effects in load rating. This can provide a basis for future performance monitoring techniques and structural health monitoring.
This study proposes targeted modernization of the Department of Defense (DoD's) Joint Forces Ammunition Logistics information system by implementing the optimized…
This study proposes targeted modernization of the Department of Defense (DoD's) Joint Forces Ammunition Logistics information system by implementing the optimized innovative information technology open architecture design and integrating Radio Frequency Identification Device data technologies and real-time optimization and control mechanisms as the critical technology components of the solution. The innovative information technology, which pursues the focused logistics, will be deployed in 36 months at the estimated cost of $568 million in constant dollars. We estimate that the Systems, Applications, Products (SAP)-based enterprise integration solution that the Army currently pursues will cost another $1.5 billion through the year 2014; however, it is unlikely to deliver the intended technical capabilities.
This article outlines the procedures being used at Westland Helicopters Limited to establish the fatigue lives of the dynamic and structural components of the Lynx and to…
This article outlines the procedures being used at Westland Helicopters Limited to establish the fatigue lives of the dynamic and structural components of the Lynx and to demonstrate how an adequate safety level is achieved under the loading sustained by the aircraft. For the newcomer to the fatigue problem a brief introduction to the phenomenon of fatigue will be provided and it will be shown how it is applicable to a helicopter. A philosophical outline of the fatigue procedures in current use at Westlands follows and then a description of the Lynx is given. The article will then describe the fatigue testing, flight testing and substantiation procedures used with the Lynx and it will be shown how the eventual fatigue lives are estimated. Finally some thoughts are put forward about the future of fatigue substantiation.
THE purpose of this paper is to examine the part that metal fatigue plays in the engineering of the helicopter, and to outline the methods used at present to estimate the…
THE purpose of this paper is to examine the part that metal fatigue plays in the engineering of the helicopter, and to outline the methods used at present to estimate the safe fatigue life of the component parts of the helicopter.
If facilities managers are to have an impact on the performance of buildings it is vitally important that they appreciate the links between day‐to‐day use of a building…
If facilities managers are to have an impact on the performance of buildings it is vitally important that they appreciate the links between day‐to‐day use of a building component or element and its durability. Facilities managers play an important role in providing a body of expertise and feedback to design professionals who frequently only have a limited association with the building in use. This article examines the impact of dynamic loads on raised access floors located in general office areas. In particular it highlights and discusses rolling loads, an area surrounded by controversy.
Earthquake tremors not only increase the chances of fire ignition but also hinder the fire-fighting efforts due to the damage to the lifelines of a city. Most of the…
Earthquake tremors not only increase the chances of fire ignition but also hinder the fire-fighting efforts due to the damage to the lifelines of a city. Most of the international codes have independent recommendations for structural safety against earthquake and fire. However, the possibility of a multi-hazard event, such as fire following an earthquake is seldom addressed.
This paper presents an experimental study of Reinforced Concrete (RC) columns in post-earthquake fire (PEF) conditions. An experimental approach is proposed that allows the testing of a column instead of a full structural frame. This approach allows us to control the loading and boundary conditions individually and facilitates the testing under a variety of these conditions. Also, it allows the structure to be tested until failure. The role of parameters, such as earthquake intensity, axial load ratio and the ductile detailing of the column on the earthquake damage and subsequently the fire performance of the structure, is studied in this research. Six RC column specimens are tested under a sequence of quasi-static earthquake loading, followed by combined fire and axial compression loading conditions.
The experiment results indicate that ductile detailed columns subjected to 4% or less lateral drift did not lose significant load-carrying capacity in fire conditions. A lateral drift of 6% caused significant damage to the columns and reduced the load-carrying capacity in fire conditions. The level of the axial load acting on the column at the time of earthquake loading was found to have a very significant effect on the extent of damage and reduction in column load capacity in fire conditions. The columns that were not detailed for a ductile behavior observed a more significant reduction in axial load carrying capacity in fire conditions.
This study is limited to columns of 230 mm size due to the limitations of the test setup. The applicability of these findings to larger column sections needs to be verified by developing a numerical analysis methodology and simulating other post-earthquake-fire tests available in the literature.
The experimental procedure proposed in this paper offers an alternative to the testing of a complete structural frame system for PEF behavior. In addition to the ease of conducting the tests, the procedure also allows much better control over the heating, structural loading and boundary conditions.
This preliminary investigation has shown that the programme load method of testing provides more useful information than single load level tests enabling a more reliable…
This preliminary investigation has shown that the programme load method of testing provides more useful information than single load level tests enabling a more reliable estimate of a structural joint fatigue life to be obtained.
A comment was once made that a helicopter was a multi spindle Wohler fatigue machine. Although this is perhaps a rather unkind remark there is, nevertheless, some truth in the fact that a helicopter, by its very nature, produces large dynamic loads in its rotating system and becomes dominated by considerations of fatigue strength. The result of this is that it is necessary to make extensive calculations, flight measurements and subsequently testing of all parts of the helicopter in order to satisfy the air‐worthiness requirements and the evaluation of the fatigue life of the rotor head represents a substantial investment in time and money in any helicopter project. This paper is concerned with the way in which the testing of a rotor head, that is the hub centre, up to the attachment to the blades, is dealt with at Westland Helicopters.
IN the year 1945 aircraft structural design had reached an advanced stage in this country, as judged by all previous standards. The needs of war and the vast expenditure…
IN the year 1945 aircraft structural design had reached an advanced stage in this country, as judged by all previous standards. The needs of war and the vast expenditure on aircraft design and manufacture had unquestionably forced the pace of progress. On the other hand, war‐time conditions must inevitably have tended to produce an unbalanced growth. Expenditure of money and effort was accompanied by a no less drastic expenditure of technical capital, and really long‐term thinking was unavoidably put aside.