Iole Pecora

Date of Graduation

2017

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Eduardo M Sosa

Committee Co-Chair

Ever J Barbero

Committee Member

Gregory J Thompson

Abstract

The protection of transportation tunnels is one of the top priorities of transportation and government entities. Transportation tunnels have been identified as particularly vulnerable to different threats such as propagation of toxic gasses, or smoke originated by human activities or flooding originated by extreme climatic events such as hurricanes and severe weather. Finding solutions to minimize the consequences of disastrous events has become critical to increase the resiliency of tunnel systems. The implementation of large-scale inflatable structures at specific locations of the tunnel system for containing the propagation of flooding or gases is now possible. When a threat happens, a sensing system detects the threat and triggers the activation of an inflation system which can deploy, inflate and pressurize the inflatable structure in a few minutes. When the inflatable structure is completely inflated, it acts as a barrier that can isolate the compromised region and contain the threat. The feasibility of this concept was demonstrated in 2008, and several experimental evaluations were conducted in the recent years to demonstrate the operational viability of this solution. Despite the successful results seen in the experimental evaluations, the development of simulations that can predict results in advance to reduce the number of experimental iterations is still essential. Finite Element simulation efforts performed in the recent years contributed to the understanding of the dynamics of the deployment and inflation of an inflatable structure for one particular tunnel profile and one folding and deployment configuration. However, if the membrane material of the inflatable changes, or the shape or configuration of the tunnel profile changes, or the position for storage of the folded inflatable changes, the initial behavior of the unstressed membrane during the initial deployment and later inflation, will be different. All this variability increases the need of experimental iterations to determine the appropriate combination of parameters to achieve acceptable results. Considering that the resources for experimental iterations can be very limited, there is a clear need to continue with the development of predictive models that can account for the different factors involved in the implementation of inflatable structures for tunnel protection.;This work presents the development of Finite Element simulations generated for the evaluation of different phases of the operation of a large-scale inflatable structure used for sealing a tunnel segment. The simulations developed in this work focused on reproducing deflation, folding, and placement procedures for deploying an inflatable from the ceiling of a tunnel segment. The models were also used to evaluate the behavior of the inflatable during the initial deployment and the full inflation. Different strategies were analyzed with the ultimate goal of maximizing the global and local conformity, which translate in a better sealing capacity of the inflatable to the tunnel profile. The results of the simulations showed that a very flat shape can be achieved by implementing a controlled deflation of the nominal shape of the inflatable as a starting point of the folding procedures. Moreover, a combination of translational and rotational planes allowed the flattened shape to reach a more compact shape at the end of the folding procedures. Simulation results also showed that the stiffness of the membrane influenced the shape and behavior of the inflatable during the initial deployment. Moreover, results demonstrated that the implementation of passive restrainers to control the movement and release of the membrane during the deflation, folding, deployment and inflation contributed to reach higher levels of local conformity of the inflatable to the tunnel perimeter, as well as an increase of the contact area as the global and local conformity improved. A comparison of simulation results with available experimental data demonstrated a good level of agreement between the finite element simulations and the experimental observations.

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