Bridges are structures that have both engineering and architectural value. The importance bridges have in society is not only due to their function but their form and posture. Bridges are structures that pass longer spans among all other structures. This passageway includes not only the quantitative values, but the quality also. The perfect harmony between its form and function is reflected in its overall structure. Footbridges are the most intimate type of bridges for people. Usually of smaller dimensions and lighter weight, the design for these types is done with more aesthetic care. In this study, bridges are briefly analyzed from both architectural and engineering points of view. The differences and importance of footbridges in daily life are studied. Some of the existing footbridges in Ankara are observed and models, inspired by them, are made. With necessary adaptations, new cases are obtained and comparisons in their dimensions and structural system are realized.

No description available.

Fire is a significant threat to the structural integrity of buildings. Depending on the architecture of the structure and the intensity and duration of the fire event, structural members may lose strength and stiffness eventually leading to collapse whether by flexural buckling or crushing. The focus of this research is on the behavior and fire performance of reinforced-concrete columns under fire conditions. In order to effectively study column performance with differing loading, aggregate and dimensional characteristics under varying time-temperature curves and fire exposures, a numerical model was constructed in Microsoft Excel. The spreadsheet model allowed for complete transparency of the calculations and provided a means to visualize the data in flexible ways. ANSYS and several published column furnace tests were used to benchmark the heat transfer and structural analysis portions of the model. One, three and four-sided fire exposures along with the ASTM E119 fire curve and a natural fire curve were used to study latent heating effects, increasing and decreasing eccentricities, moment magnification, and failure modes. Assessments of column structural capacity were performed in accordance with the provisions of ACI 318. The completed model served as an effective tool for the thesis and is available to help aid students and engineers investigate the design of reinforced concrete columns under fire conditions through integration the heat transfer analyses and the structural evaluations.

The installation of geogrid as a means of extending the service life of a roadway or reducing the required base course thickness of a pavement structure has become increasingly popular. The realization of these benefits depends largely on the degree to which the geogrid reinforcement leads to an increase in the stiffness of the aggregate base course layer. The objective of this research was to investigate the structural capacity of geogrid-reinforced aggregate base materials in flexible pavements through full-scale testing. The scope involved field testing at two sites in northern Utah that each included five different geogrid-reinforced sections and five accompanying unreinforced control sections. Five different geogrid types were utilized to ensure that the experimentation was representative of the geogrid products available in the industry at the time of the study. At each of the two field sites, 10 test sections were established, and several field tests were conducted during and following construction of the two pavements to characterize the in-situ structural properties of the subgrade, base, and hot mix asphalt layers of each geogrid-reinforced and unreinforced test section. The procedures involved nuclear density gauge, soil stiffness gauge, Clegg impact soil tester, dynamic cone penetrometer (DCP), portable falling-weight deflectometer, and falling-weight deflectometer testing of each test section. Samples of the subgrade and base materials were also obtained from both field sites for laboratory testing, which included dry and washed sieve analyses, Atterberg limits testing, and material classification. An analysis of covariance (ANOCOVA) was conducted on the results of each field test to determine if the structural capacity of the geogrid-reinforced sections was different than that of the accompanying unreinforced control sections.Among the 24 ANOCOVA models developed for the two field sites, only four indicated that geogrid presence was statistically significant. Of these four models, three indicated that the presence of geogrid reinforcement led to higher values of the given measurement of structural capacity compared to the unreinforced condition; however, in none of the cases was the difference practically important as defined in this research and would therefore not result in a different input in the pavement design process. Notably, in all three of these models, the same testing procedure, namely the DCP, was used for the testing. A measurable increase in the structural capacity of the reinforced layer may not be immediately observable using standard pavement testing procedures. Further field research is recommended to investigate the duration of the required conditioning period and also the extent of the zone of influence of geogrid reinforcement in aggregate base courses.

The objective of this research was to develop a structural index for use in network-level pavement evaluation, which facilitates the inclusion of the pavements structural condition in many pavement management applications. The primary goal of network-level pavement management is to maintain an acceptable condition of the pavements within the network using available, and often limited, resources. Pavement condition is described in terms of functional and structural condition, and the current widespread practice is to only consider the functional condition during network-level evaluation. This practice results in treatments that are often under-designed or over-designed when considered in more detail at the project-level. The disagreement may be reduced by considering the structural capacity of the pavements as part of the network-level decision process. This research was conducted by identifying various structural indices, choosing an appropriate index, and then applying data from the state of Virginia to modify the index and show example application for the index. It was concluded that the Modified Structural Index best met the research objectives. Project-level and network level data were used to conduct a sensitivity analysis on the index, and example applications were presented. The results indicated that the inclusion of the Modified Structural Index into the network-level decision process minimized the errors between network-level and project-level decisions, when compared to the current network-level decision making process. Furthermore, the Modified Structural Index could be used in various pavement management applications, such as network-level structural screening, and developing structural performance measures. / Master of Science

This thesis focused on using a detailed structural evaluation of seven (three flexible and four composite) high performance in-service pavements designated as high-priority routes to verify the applicability of the Mechanistic Empirical (M-E) models to high performance pavements in the Commonwealth of Virginia. The structural evaluation included: determination of layer thicknesses (from cores, GPR and historical data), pavement condition assessment based on visual survey, estimation of layer moduli from FWD analysis as well as material characterization. One of the main objectives of this study was to utilize the results from the backcalculated moduli in order to predict the performance of this group of pavement structures using the M-E Design Guide Software. This allowed a quick verification of the performance prediction models used by comparing their outcome with the current condition. The in-depth structural evaluation of the three flexible and four composite pavements showed that all the sites are structurally sound. The investigation also confirmed that the use of GPR to determine layer thicknesses and the comparison with a minimum number of cores is a helpful tool for pavement structural evaluation. Despite some difficulties performing the backcalculation analysis for complex structures, the obtained results were considered reasonable and were useful in estimating the current structural adequacy of the evaluated structures. The comparison of the measured distresses with those predicted by the M-E Design Guide software showed poor agreement. In general, the predicted distresses were higher than the distresses actually measured. However, there was not enough evidence to determine whether this is due to errors in the prediction models or software, or because of the use of defaults material properties, specially for the AC layers. It must be noted that although an in-depth field evaluation was performed, only Level 3 data was available for many of the input parameters. The results suggest that significant calibration and validation will be required before implementation of the M-E Design Guide. / Master of Science

The objective of this research was to investigate the structural capacity of aggregate base materials stabilized with triaxial geogrid placed in a full-scale pavement involving control, or unstabilized, sections. Field testing was performed on a roadway in northeastern Utah that was 16 km (10 miles) long and included 10 test sections, seven stabilized sections and three control sections, each having five test locations. The pavement structure was comprised of a hot mix asphalt layer overlying an untreated aggregate base layer of varying thickness, depending on the test section. Except for the control sections, one or two layers of geogrid were incorporated into portions of the pavement structure at different locations. Falling-weight deflectometer testing and dynamic cone penetrometer testing were used to evaluate the structural capacity of the aggregate base layer in each pavement section. For data analysis, the Rohde's method was applied in conjunction with the 1993 American Association of State Highway and Transportation Officials pavement design guide methodology, and the Area under the Pavement Profile (AUPP) method was applied in conjunction with a mechanistic-empirical pavement analysis. Statistical analyses were then performed to enable comparisons of the test sections. Field results indicated that the asphalt layer thickness was consistently 140 mm (5.5 in.) at all 10 test sections, and the base layer thickness varied from 360 mm (14 in.) to 510 mm (20 in.). The results of the statistical analyses indicated that the majority of the 45 possible pairwise comparisons among the test sections were not statistically significant, meaning that variations in the presence and position of triaxial geogrid at those sections did not appear to affect the structural capacity. The remaining comparisons, however, were statistically significant and involved the test sections with the highest structural capacity. While one of these was unexpectedly an unstabilized control section, the others were constructed using one or two layers of geogrid in the base layer. In addition to being statistically significant, the observed differences were also practically important. Increases in the observed base layer coefficient from 0.12 to 0.18 correspond to an increase in the allowable number of equivalent single axle loads (ESALs) from 5.9 million to 19.2 million at the research site, while decreases in the observed AUPP value from 340 mm (13.37 in.) to 213 mm (8.38 in.) correspond to an increase in the allowable number of ESALs from 3.7 million to 17.3 million at the research site. These results indicate that, when geogrid reinforcement is compatible with the given aggregate base material and proper construction practices are followed, statistically significant and practically important increases in pavement design life can be achieved.

No description available.

Adjacent precast, prestressed box beam bridges have a history of poor performance and have been observed to exhibit common types of deterioration including longitudinal cracking, concrete spalling, and deterioration of the concrete top flange. The nature of these types of deterioration leads to uncertainty of the extent and effect of deterioration on structural behavior. Due to limitations in previous research and understanding of the strength of deteriorated box beam bridges, conservative assumptions are being made for the assessment and load rating of these bridges. Furthermore, the design of new box beam bridges, which can offer an efficient and economical solution, is often discouraged due to poor past performance. Therefore, the objective of this research is to develop improved recommendations for the inspection, load rating, and design of adjacent box beam bridges. Through a series of bridge inspections, deteriorated box beams were identified and acquired for experimental testing. The extent of corrosion was determined through visual inspection, non-destructive evaluation, and destructive evaluation. Non-destructive tests (NDT) included the use of connectionless electrical pulse response analysis (CEPRA), ground penetrating radar (GPR), and half-cell potentials. The deteriorated capacity was determined through structural testing, and an analysis procedure was developed to estimate deteriorated behavior. A rehabilitation procedure was also developed to restore load transfer of adjacent beams in cases where shear key failures are suspected. Based on the understanding of deterioration developed through study of deteriorated adjacent box beam bridges, improved inspection and load rating procedure are provided along with design recommendations for the next generation of box beam bridges.