Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Eine Plattform für die Wissenschaft: Bauingenieurwesen, Architektur und Urbanistik
Moisture Induced Pressures in Concrete Airfield Pavements
The erosion of military concrete airfield pavements by jet exhausts is an expensive problem expected to get worse. Scaling of pavements is being observed beneath the auxiliary power units (APUs) of F/A-18 and B-1 aircraft. The AV-8B Harrier and future vertical takeoff and landing aircraft will generate a concrete environment much more severe than that generated by the low power APUs. In order to develop pavements impervious to this form of erosion, the failure mechanism must be known. One plausible culprit, suggested by the apparent role of heating, is moisture. To examine this hypothesis, a mathematical model was developed to predict pore pressures caused by water vapor and air migrating through the pores of a heated section of concrete. The foundation of this model is a constitutive relationship developed to characterize the flow of high velocity, compressible, heated gases through concrete. This relationship equates a nondimensional flow parameter with pressure and temperature ratios across the medium. The key premise is that the resistance to flow through a high resistance porous medium can be modeled with friction coefficients analogous to the method used for simpler geometries. Pore pressures predicted using this model show that moisture in the pores of the cement is unlikely to be the primary cause of material failure in airfield pavements heated by the F/A-1 8 APU. Moisture is a probable cause of failure, however, when the cement is being heated by the exhaust of a Harrier during takeoff and landing.
Moisture Induced Pressures in Concrete Airfield Pavements
The erosion of military concrete airfield pavements by jet exhausts is an expensive problem expected to get worse. Scaling of pavements is being observed beneath the auxiliary power units (APUs) of F/A-18 and B-1 aircraft. The AV-8B Harrier and future vertical takeoff and landing aircraft will generate a concrete environment much more severe than that generated by the low power APUs. In order to develop pavements impervious to this form of erosion, the failure mechanism must be known. One plausible culprit, suggested by the apparent role of heating, is moisture. To examine this hypothesis, a mathematical model was developed to predict pore pressures caused by water vapor and air migrating through the pores of a heated section of concrete. The foundation of this model is a constitutive relationship developed to characterize the flow of high velocity, compressible, heated gases through concrete. This relationship equates a nondimensional flow parameter with pressure and temperature ratios across the medium. The key premise is that the resistance to flow through a high resistance porous medium can be modeled with friction coefficients analogous to the method used for simpler geometries. Pore pressures predicted using this model show that moisture in the pores of the cement is unlikely to be the primary cause of material failure in airfield pavements heated by the F/A-1 8 APU. Moisture is a probable cause of failure, however, when the cement is being heated by the exhaust of a Harrier during takeoff and landing.
Moisture Induced Pressures in Concrete Airfield Pavements
C. A. Kodres (Autor:in)
1994
106 pages
Report
Keine Angabe
Englisch
Civil Engineering , Soil & Rock Mechanics , Airports , Damage assessment , Moisture content , Pore pressure , Jet engine exhaust , Erosion , Fighter aircraft , Bomber aircraft , Fatigue(Mechanics) , Failure(Mechanics) , Computer programs , Cements , Porosity , Vertical takeoff aircraft , Thermal expansion , Mathematical models , Friction , Flow rate , Cracking(Fracturing) , Spallation , Concrete durability , Pavement damage , Concrete pavements , Portland cement , F/A-18 Aircraft , B-1 Aircraft , AV-88 Aircraft
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