2 resultados para 090108 Satellite Space Vehicle and Missile Design and Testing

em Iowa Publications Online (IPO) - State Library, State of Iowa (Iowa), United States


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This study had three objectives: (1) to develop a comprehensive truck simulation that executes rapidly, has a modular program construction to allow variation of vehicle characteristics, and is able to realistically predict vehicle motion and the tire-road surface interaction forces; (2) to develop a model of doweled portland cement concrete pavement that can be used to determine slab deflection and stress at predetermined nodes, and that allows for the variation of traditional thickness design factors; and (3) to implement these two models on a work station with suitable menu driven modules so that both existing and proposed pavements can be evaluated with respect to design life, given specific characteristics of the heavy vehicles that will be using the facility. This report summarizes the work that has been performed during the first year of the study. Briefly, the following has been accomplished: A two dimensional model of a typical 3-S2 tractor-trailer combination was created. A finite element structural analysis program, ANSYS, was used to model the pavement. Computer runs have been performed varying the parameters defining both vehicle and road elements. The resulting time specific displacements for each node are plotted, and the displacement basin is generated for defined vehicles. Relative damage to the pavement can then be estimated. A damage function resulting from load replications must be assumed that will be reflected by further pavement deterioration. Comparison with actual damage on Interstate 80 will eventually allow verification of these procedures.

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Internal curing is a relatively new technique being used to promote hydration of Portland cement concretes. The fundamental concept is to provide reservoirs of water within the matrix such that the water does not increase the initial water/cementitious materials ratio to the mixture, but is available to help continue hydration once the system starts to dry out. The reservoirs used in the US are typically in the form of lightweight fine aggregate (LWFA) that is saturated prior to batching. Considerable work has been conducted both in the laboratory and in the field to confirm that this approach is fundamentally sound and yet practical for construction purposes. A number of bridge decks have been successfully constructed around the US, including one in Iowa in 2013. It is reported that inclusion of about 20% to 30% LWFA will not only improve strength development and potential durability, but, more importantly, will significantly reduce shrinking, thus reducing cracking risk. The aim of this work was to investigate the feasibility of such an approach in a bridge deck.