The advantages of using high strength concrete (HSC) have led to an increase in the typical span and a reduction of the weight of prestressed girders used for bridges. However, growing demands to utilize HSC require a reassessment of current provisions of the design codes. The objective of one of the research projects, recently initiated and sponsored by the National Cooperative Highway Research Program (NCHRP), NCHRP Project 12-64, conducted at North Carolina State University is to extend the use of the current AASHTO LRFD design specifications to include compressive strength up to 18,000 psi (124 MPa) for reinforced and prestressed concrete members in flexure and compression. This thesis deals with one part of this project. Nine full-size AASHTO girders are examined to investigate the behavior of using different concrete compressive strength and subjected to the flexural loadings. The experimental program includes three different configurations of prestressed girders with and without a deck slab to investigate the behavior for the following cases: 1) the compression zone consists of normal strength concrete (NSC) only; 2) the compression zone consists of HSC only; and 3) the compression zone consists of a combination of two different strengths of concrete. An analytical model is developed to determine the ultimate flexural resistance for prestressed girders with and without normal compressive strength concrete. The research also includes investigation of the transfer length and the prestress losses of HSC prestressed girders. Based on materials testing and extensive data collected from the literature, a new equation is proposed to calculate the elastic modulus for normal and high strength concrete.

Since the early 1950âs, composite concrete-steel systems have been a popular and economic choice for floor construction in the United States. The conventional composite floor system comprised of a concrete slab with light gauge steel deck form supported by wide flange structural steel girders has been widely used in construction. In recent years, modifications to the conventional system have been made to meet a market need for floor systems with reduced structural depth to be used in a variety of building types including office buildings, hotels, and hospitals. In 2007, Diversakore® LLC developed the Versa :T:TM beam, an innovative shallow floor composite framing system that utilizes a small structural depth and also makes improvements in the ease and speed of construction. The system includes a u-shaped steel plate which supports hollow core plank flooring during construction and serves as a stay-in-place form for a cast-in-place reinforced concrete girder. The concrete girder is cast monolithically with a topping slab to engage the hollow core planks and the u-shaped steel section into a composite t-beam. A research program to evaluate the performance of this innovative floor system has been developed and is currently ongoing at the Constructed Facilities Laboratory at North Carolina State University in Raleigh, NC. The experimental and analytical program includes full-scale tests of representative sub-assemblages and utilizes a layered sectional analysis to predict the behavior. The results of the analytical model and the experimental investigation are presented along with conclusions drawn from the initial phase of the research program.

This research evaluated longitudinal pavement marking performance and developed useful degradation models for paint pavement markings which can help transportation agencies meet the pending FHWA minimum retroreflectivity requirements. The impacts of several important factors (such as directionality, pavement type and roughness) on marking retroreflectivity were evaluated. With a large dataset in hand, we determined whether these factors had significant impacts on marking retroreflectivity. Paint pavement marking centerline retroreflectivity values measured in the direction of paint striping were found to be significantly higher than the values measured in the opposite direction. The mean values of the retroreflectivity measurements collected on the plant mixed pavements were found to be significantly larger than the values collected on the bituminous surface treatment (BST) pavements. Image processing techniques were used to analyze paint pavement marking surface glass bead density. Bead density values were found to have a positive correlation with marking retroreflectivity measurements. Higher glass bead density led to higher marking retroreflectivity. The research also compared existing marking retroreflectivity degradation models. A linear mixed effects model (LMEM) was selected as most appropriate for the paint marking retroreflectivity data. LMEMs were established for paint pavement markings based on the data collected in NC. The research outcomes can help transportation agencies have a better understanding of paint pavement marking performance, which can lead to cost savings by maximizing the marking service lifecycles.

Four full-scale field lateral load tests were conducted to independently verify the Weathered Rock Model for P-y Curves published by Cho (2002). Class A performance predictions were developed and presented to North Carolina Department of Transportation officials prior to testing. Performance predictions were calculated using the Weathered Rock Model, Reese¡¯s Method for P-y Curves in Weak Rock (Reese, 1997), and the Stiff Clay Model (Reese, Cox, and Koop, 1975). Field testing was conducted on two sites in Durham County, North Carolina; both sites were located within the Durham Triassic Basin. Two fully instrumented drilled shafts were constructed at each site; the instrumentation plan allowed for the measurement of top deflections, head rotation, shaft deflection and strain with depth. Results obtained from each test shaft are compared with respective Class A performance predictions. Results of verification testing show that the Weathered Rock Model can be used to accurately model the lateral deflection behavior of drilled shafts embedded in weathered rock profiles. Distribution of the subgrade reaction evaluated from testing results is compared with that published by Cho (2002) for other types of weathered rock. The magnitude of the increase in the subgrade reaction below the point of rotation for Triassic Weathered Rock is not as significant as that realized by Cho (2002). Recommended design procedures for using the Weathered Rock Model with either rock dilatometer data or geologic data are presented.

Research work in this thesis deals with the effects of lateral loads in the longitudinal direction on a substructure?s point of fixity. Full scale tests were performed to model and test a section of a bridge where the superstructure is connected to the substructure through elastomeric bearing pads. The connection rotational stiffness between the super and substructure was measured as an effect of applying a lateral load to the foundation element and creating a moment at the connection joint. A circular concrete pile, square concrete pile, and steel H-pile were tested in connection with both type V and type VI elastomeric bearing pads. The response of these full scale tests were then modeled in FB-MultiPier as tested and as an equivalent single foundation element. The model response was then compared to the measured results. Through the use of FB-MultiPier, three existing North Carolina bridges? foundation elements were analyzed to determine an effective range of partial head fixity and its compounding effects on the development of a foundation element?s depth to fixity.

This project assesses the feasibility of using statistically clustered property tax data instead of windshield survey data for input into the Internal Data Summary (IDS) trip generation model used by the North Carolina Department of Transportation. The report summarizes the clustering analysis and its data requirements. To gauge clustering resource requirements for a case study application, NCSU researchers examine the Town of Pittsboro. Comparing the traffic flow outputs of the traditional modeling techniques and those resulting from the use of the clustering method to 56 ground count stations, the research finds that clustering and tradition methods yield similar results. An 85% reduction in person-hours required to gather the input data is the main benefit resulting from the use of the clustering technique. The major drawback is that advanced statistical training is required to implement the technique.

Evaluation of the structural condition of deteriorated concrete infrastructure and evaluation of new sustainable cementitious materials require an understanding of how the material will respond to applied loads and environmental exposures. A fundamental understanding of how microstructural changes in these materials relate to changes in mechanical properties and changes in fluid penetrability is needed. The ability to provide rapid, inexpensive assessment of material characteristics and relevant engineering properties is valuable for decision making and asset management purposes. In this investigation, the effects of changes in dynamic elastic properties with water content and fluid penetrability properties before and after a 300 °C exposure were investigated as they relate to estimates of the crack density parameter, developed from the work by OâConnell and Budiansky (1974; 1977) on dry and saturated crack media. The experimental and analytical techniques described in this dissertation allow calculation of a value for the crack density parameter nondestructively from differences in wet and dry dynamic shear modulus of relatively thin disks. The techniques were used to compare a conventional concrete mixture and several mixtures with enhanced sustainability characteristics. The analysis provided quantitative assessment of changes with high temperature damage and autogenous healing, and provided estimates of increases in mean crack trace lengths. The three enhanced sustainable materials investigated were a very high fly ash mixture (mixture F), a magnesium phosphate cement based mortar (mixture M), and a magnesium phosphate cement based concrete (mixture G), and were compared to a conventional concrete mixture (mixture C). The results showed that water interaction, deterioration due to damage, and autogenous healing recovery were different for mixtures G and M than the concrete mixtures C and F based on portland cement. A strong correlation was found between log(API), Gd and crack density parameter. The findings imply that the test method and related analysis can be used to evaluate the validity of current standard test methods to new âgreenâ construction materials and therefore be a useful screening tool as well as providing important insight into microstructural changes in concrete under various exposures.

This research presents the results of an experimental program undertaken at the North Carolina State University (NCSU) Constructed Facilities Laboratory (CFL) to evaluate the performance of a new innovative glass fiber reinforced polymer (GFRP) bridge deck. This bridge deck is produced commercially by Martin Marietta Composites of Raleigh, NC under the trade name of DuraSpan. The experimental program involved examining the behavior of 5.00 inch deep and 7.66 inch deep DuraSpan bridge deck profiles. The program included numerous quasi-static flexural tests, testing of connection details to facilitate the development of a railing system, evaluation of the performance of the bond lines in negative moment regions, and an evaluation of the coefficient of thermal expansion. A finite element model was developed to predict the stiffness of the bridge deck at service load levels. Finite element optimization techniques were used in conjunction with coupon test data and the large scale flexural test data to calibrate the model.

Emulsified oil can be injected into the subsurface to enhance the in-situ bioremediation of chlorinated solvents, energetic materials, and some heavy metals. Current design practice for these remediation systems is not well formalized and depends much on ?engineering intuition.? To better understand the effects of different remediation system designs, computer models are being developed that can accurately and efficiently simulate how the oil moves through and reacts in the subsurface. To this end, we have developed a Langmuir isotherm based transport model to simulate the distribution of emulsified oils in an aquifer in order to investigate what effect changing the volume of emulsion, amount of oil, and injection pattern has on distributing the oil through the aquifer. Upon investigation we found that increasing the volume of emulsion and mass of oil has a diminishing increase on distribution and that injection pattern has little effect at typical injection volumes. We further developed regression equations to estimate the distribution of emulsified oil for both areal and barrier treatment to be used in improving injection system design.

Biodiesel is an alternative fuel that can be made from vegetable oils or animal fat. This study focuses on whether substitution of soy-based biodiesel fuels for petroleum diesel would produce an overall reduction in emissions of selected pollutants. A life cycle inventory model was developed to estimate energy consumption and emissions of selected pollutants and greenhouse gases. Real-world measurements using portable emission measurement system (PEMS) were made for 15 construction vehicles, including five backhoes, four front-end loaders, and six motor graders on both petroleum diesel and soy-based B20 biodiesel. These data are used as the basis for vehicle tailpipe emission factors of CO2, CO, HC, NOx, and PM. The results imply that biodiesel is a promising alternative fuel for diesel, but that there are some environmental trade-offs. Analysis of empirical data reveals that intra-vehicle variability of energy use and emissions is strongly influenced by vehicle activity that leads to variations in engine load, as represented by manifold absolute pressure (MAP). Vehicle-specific models for fuel use and tailpipe emissions were developed for each of the 30 construction vehicle. The time-based regression model has the highest explanatory ability among six models and is recommended in order to predict fuel use and emission rate for diesel-fueled nonroad construction equipment. Representative duty cycles for each type of vehicles were characterized by a frequency distribution of normalized manifold absolute pressure (MAP). In order to assess the variations of fuel use and emissions among different duty cycles, for a given engine, the inter-cycle variability is assessed. In order to assess the variations of fuel use and emissions among engines, for a given duty cycle, the inter-engine variability is assessed. The results indicated time-based inter-cycle and inter-engine variations of fuel use and emissions are significant. Fuel-based emission factors have less variability among cycles and engines than time-based emission factors. Fuel-based emission factors are more robust with respect to inter-engine and inter-cycle variations and are recommended in order to develop an emissions inventory for nonroad construction vehicles. Real-world in-use measurements should be a basis for developing duty cycle correction factors in models such as NONROAD.