Current Issue : July - September Volume : 2012 Issue Number : 3 Articles : 5 Articles
The Moment Distribution Method is a quite powerful hand method of structural analysis, in which the solution is obtained\niteratively without even formulating the equations for the unknowns. It was formulated by Professor Cross in an era where\ncomputer facilities were not available to solve frame problems that normally require the solution of simultaneous algebraic\nequations. Its relevance today, in the era of personal computers, is in its insight on how a structure reacts to applied loads by\nrotating its nodes and thus distributing the loads in the form of member-end moments. Such an insight is the foundation of the\nmodern displacement method. This work has a main objective to present an exact solution for the Moment Distribution Method\nthrough a matrix formulation using only one equation. The initial moments at the ends of the members and the distribution and\ncarry-over factors are calculated from the elementary procedures of structural analysis. Four continuous beams are investigated to\nillustrate the applicability and accuracy of the proposed formulation. The use of a matrix formulation yields excellent results when\ncompared with those in the literature or with a commercial structural program....
The low-cost, widespread availability and robust nature of current electronic devices suggest the feasibility of creating a composite\r\nstructure with integrated networked sensors to monitor in real time the life of civil and aerospace structures while in service\r\nconditions. For structures that need to survive to high number of life cycles under varying load-environmental conditions, it is of\r\ncrucial importance that the strength, stiffness, endurance, and general load-bearing capabilities of the composite not to be severely\r\ndegraded by the integrated networked components. Therefore, design tools must be developed to achieve optimized, safe, and\r\nreliable structures. High values of stress concentrations due to the presence of a rigid device within a highly anisotropic material\r\ncan trigger the initiation of microcracks in the resin matrix. To quantify these effects, the acoustic emission technique is used to\r\ncharacterize the initiation of microfailures within laminated composites with integrated electronics....
Helical anchors are vital support components for power transmission lines. Failure of a single anchor can lead to the loss of an\r\nentire transmission line structure which results in the loss of power for downstream community. Despite being important, it is\r\nnot practical to use conventional borehole method of subsurface exploration, which is labor intensive and costly, for estimating\r\nsoil properties and anchor holding capacity. This paper describes the use of an empirical and elasticity-based design technique\r\ncoupled with the spectral analysis of surface wave (SASW) technique to provide subsurface information for anchor foundation\r\ndesigns. Based on small-strain wave propagation, SASW determines shear wave velocity profile which is then correlated to anchor\r\nholding capacity. A pilot project involving over 400 anchor installations has been performed and demonstrated that such technique\r\nis reliable and can be implemented into transmission line structure designs....
Major threats to bridges primarily consist of the aging of the structural elements, earthquake-induced shaking and standing waves\r\ngenerated by windstorms. The necessity of information on the state of health of structures in real-time, allowing for timely\r\nwarnings in the case of damaging events, requires structural health monitoring (SHM) systems that allow the risks of these\r\nthreats to be mitigated. Here we present the results of a short-duration experiment carried out with low-cost wireless instruments\r\nfor monitoring the vibration characteristics and dynamic properties of a strategic civil infrastructure, the Adolphe Bridge in\r\nLuxembourg City. The Adolphe Bridge is a masonry arch construction dating from 1903 and will undergo major renovation\r\nworks in the upcoming years. Our experiment shows that a network of these wireless sensing units is well suited to monitor the\r\nvibration characteristics of such a historical arch bridge and hence represents a low-cost and efficient solution for SHM....
Traffic and variable loading conditions greatly influence the performance, durability, and safety of a bridge structure throughout\r\nits service life. Continuous monitoring can provide the basis for determining the deterioration rate and for estimating the\r\nremaining service life, thus assisting in making important decisions regarding bridge maintenance. This paper presents the design\r\nand implementation of a health monitoring system for condition assessment of full-depth precast concrete bridge deck, which\r\nwas developed for the Parkview Bridge in Kalamazoo, Michigan. This system is composed of a remotely accessible on-site data\r\nacquisition system and a sensor network of vibrating wire strain gauges to monitor strain and temperature over given time\r\nincrements. The system relies on the sensor network embedded in the bridge deck to gather static performance data under different\r\nloading conditions to provide condition assessment by collecting, storing, analyzing, and reporting relevant performance data over\r\ntime. The paper presents a practical case study that mainly focuses on describing the initial steps in the development of the sensor\r\nnetwork system, namely, the design (system architecture and data structures) and construction along with examples of how the\r\ndata is acquired, organized, presented, and analyzed, keeping in mind that the bridge is still early in its life-cycle and has not yet\r\nexperienced any structural problems....
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