Browsing Civil & Environmental Engineering by Author "Aliabadizadeh, Yahya"
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- ItemBEHAVIOR OF FIBER REINFORCED POLYMER COMPOSITE PILES WITH ELLIPTICAL CROSS SECTIONS IN INTEGRAL ABUTMENT BRIDGE FOUNDATIONS(2016) Aliabadizadeh, Yahya; Amde, Amde M.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Every year in the US and other cold-climate countries considerable amount of money is spent to restore structural damages in conventional bridges resulting from (or “caused by”) salt corrosion in bridge expansion joints. Frequent usage of deicing salt in conventional bridges with expansion joints results in corrosion and other damages to the expansion joints, steel girders, stiffeners, concrete rebar, and any structural steel members in the abutments. The best way to prevent these damages is to eliminate the expansion joints at the abutment and elsewhere and make the entire bridge abutment and deck a continuous monolithic structural system. This type of bridge is called Integral Abutment Bridge which is now widely used in the US and other cold-climate countries. In order to provide lateral flexibility, the entire abutment is constructed on piles. Piles used in integral abutments should have enough capacity in the perpendicular direction to support the vertical forces. In addition, piles should be able to withstand corrosive environments near the surface of the ground and maintain their performance during the lifespan of the bridge. Fiber Reinforced Polymer (FRP) piles are a new type of pile that can not only accommodate large displacements, but can also resist corrosion significantly better than traditional steel or concrete piles. The use of FRP piles extends the life of the pile which in turn extends the life of the bridge. This dissertation studies FRP piles with elliptical shapes. The elliptical shapes can simultaneously provide flexibility and stiffness in two perpendicular axes. The elliptical shapes can be made using the filament winding method which is a less expensive method of manufacturing compared to the pultrusion or other manufacturing methods. In this dissertation a new way is introduced to construct the desired elliptical shapes with the filament winding method. Pile specifications such as dimensions, number of layers, fiber orientation angles, material, and soil stiffness are defined as parameters and the effects of each parameter on the pile stresses and pile failure have been studied. The ANSYS software has been used to model the composite materials. More than 14,000 nonlinear finite element pile models have been created, each slightly different from the others. The outputs of analyses have been used to draw curves. Optimum values of the parameters have been defined using generated curves. The best approaches to find optimum shape, angle of fibers and types of composite material have been discussed.
- ItemEVALUATION OF WAYS TO RECOVER LATE CONSTRUCTION PROJECTS(2009) Aliabadizadeh, Yahya; Baecher, Gregory B.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Delay in construction projects is a common issue. Considerable percentages of projects fall behind schedule causing damages to almost all involved parties. Owners may experience losses due to postponed completion dates and Contractors may face liquidated damages. Even Architects and Engineers may face additional challenges resulted by delays. In this thesis possible solutions to compensate delays before reaching the estimated end of a project have been studied. Effective usage of the remaining time to completion of the project has been the main concern, and advantages and disadvantages of each solution are studied.