Articles 1 - 6 of 6
Full-Text Articles in Engineering
Prediction Of The Compressive Strength And Dynamic Modulus Of Fiber Reinforced Concrete By Ultrasonic Pulse Velocity Measurement At Early Ages, Daniel A. Castillo Pereira
Electronic Theses and Dissertations
This research investigates the relationship between early age ultrasonic pulse velocity and the compressive strength and dynamic modulus of steel, polypropylene, nylon, and glass fiber reinforced concrete. Previous studies prove that adding fibers to concrete alters the propagation of ultrasonic pulse velocity waves. Therefore, each type of fiber-reinforced concrete will have a unique relationship between ultrasonic pulse velocity and its compressive strength and dynamic modulus depending on fiber type, fiber volume fraction, water to cement ratio, and test age. To test this hypothesis, an experimental program comprising of one hundred eighty-nine 100 mm x 200 mm fiber reinforced concrete cylinders ...
Evaluation Of Low And High Frequency Dynamic Response For Condition Assessment Of Reinforced Concrete Structures, Ali Hafiz
Dissertations and Theses
Concrete is widely used for civil infrastructure structures and they experience deterioration and degradation due to aging, increases in the traffic loads, harsher environmental conditions, use of deicing chemicals, etc. Therefore, evaluating the integrity of reinforced concrete structures has become of increasing interest for infrastructure owners and managers. A number of non-destructive testing (NDT) and structural health monitoring (SHM) methods have been developed in recent decades to aid in evaluating structures and provide input for asset management. One family of these methods uses the dynamic response of a structural member: stress waves (high frequency) and structural vibrations (low frequency). Both ...
Test And Evaluation Of Ultrasonic Additive Manufacturing (Uam) For A Large Aircraft Maintenance Shelter (Lams) Baseplate, Daniel H. Gartland
Theses and Dissertations
Additive manufacturing is an exciting new manufacturing technology that could have application to Air Force Civil Engineer (CE) operations. This research replicates a Large Area Maintenance Shelter (LAMS) baseplate design for ultrasonic additive manufacturing (UAM). Due to production problems the test section was not built as designed. Instead, a smaller block of material was submitted for evaluation. After the UAM build, ultrasonic inspection was conducted to identify anomalies in the test piece. The results of this proof of concept study indicate that UAM is not yet ready for CE expeditionary applications requiring a high degree of mechanical strength. The machine ...
Nondestructive Field Assessment Of Flexible Pavement And Foundation Layers, Jinhui Hu
Graduate Theses and Dissertations
Falling weight deflectometer (FWD) and ground penetrating radar (GPR) are nondestructive test devices widely used by transportation agencies to assess pavement conditions. The two papers in this thesis evaluated the uncertainties associated with interpreting data from these devices and assessed potential applications.
In the first paper, FWD tests were conducted on asphalt pavements with varying supporting conditions, and individual layer modulus values were estimated using forward-and back-calculation methods. Dynamic cone penetrometer (DCP) test device was used to independently measure individual layer penetration resistance (PR) values to compare with the estimate moduli values. Results indicated that the predicted subgrade moduli values ...
Optimization Of Stress Wave-Based Nondestructive Methods In Identifying Deterioration In Concrete Structures, Hoda Azari
Open Access Theses & Dissertations
The transportation infrastructure across the United States is deteriorating and requires periodic inspection to predict the cost of repair and extent of maintenance activities, to remedy structural problems, and to ensure safety and serviceability. The use of nondestructive testing (NDT) methods in detecting and characterizing ﬂaws in the infrastructure has become more common. Among different NDT methods, the stress wave-based methods, including ultrasonic surface waves (USW) and impact echo (IE) methods, are widely used to maintain concrete structures. In this dissertation, a complete literature review of seismic wave theory and wave propagation in plate like structures, and stress wave-based methods ...
Evaluation Of Nondestructive Technologies To Assess Presence And Extent Of Delamination Of Hot Mix Asphalt Airfield Pavements, Manuel Celaya
Open Access Theses & Dissertations
Sufficient bonding between the hot mix asphalt layers is essential to ensure the desired structural capacity of a pavement. Delamination or debonding problems are particularly more severe on airfield pavements, due to higher traffic loads applied by aircrafts. Further progression of delamination may result in stripping of the lower layers due to the intrusion of moisture or may develop other dangerous distresses such as foreign object debris. The existing nondestructive testing procedures and equipment that have the potential to address the problem were identified and their effectiveness and potential for success were evaluated. The Ground Penetrating Radar, Falling Weight Deflectometer ...