For the sustainability of today’s infrastructure, it is critical that engineers are capable of developing economical and safe design solutions for structures such as bridges and buildings. Multiple things must be considered for structural design. Structural members must be sized to resist applied loading conditions while satisfying design code capacity requirements. Design is also dependent on geometry, constructability, cost, material, availability, etc. The focus of optimization is to determine the best solution for a problem that is defined by a set of given constraints. For structural optimization applications, typically the problem is set up to determine the member cross-sectional areas that will yield an overall minimum weight or cost. It can also be a beneficial tool to compare different design alternatives quickly, especially in the preliminary stages of a project. Various approaches for solving optimization problems have been implemented in different fields of research. Traditional techniques such as linear/non-linear programming are available and more recently heuristic algorithms, which simulate patterns of natural phenomena, have been developed. For this research a heuristic Harmony Search (HS) algorithm is used to optimize a steel plate girder bridge. The HS algorithm is a more recent optimization concept that has been implemented within structural engineering research for solving many truss and frame optimization problems. There has been a limited amount of research on the HS algorithm for bridge structure optimization problems. For this project, HS algorithm will be used to optimize two steel plate girder bridges with varying cross-section configurations. Finite Element Models of the structures using the optimized properties will be used to verify demand/capacities and adequacy of the optimized design. Results will also be compared to traditional preliminary bridge sizing methodologies and programs. / Civil Engineering

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This study considers the application of object oriented programming approach to develop a Windows based program for the design of reinforced concrete T -beam bridges in accordance with the newly adopted AASHTO LRFD Bridge Specification. The program can perform both the analysis and design of the deck and beam. The program is interactive in nature and it is possible to change all input data and design parameters during execution. A series of second-degree interpolating polynomial functions were developed for representing influence line coordinates for various load effects in the deck and beam subjected to moving loads. The analysis results using the program were compared with those obtained from the commercial programs. The design results obtained from the program were compared with example problems for several test structures. Both design and analysis comparisons gave satisfactory results. The successful performance of the program demonstrates the significant advantages of the object oriented programming. It was concluded that the benefits of object oriented programming approach make this a viable technique for the development of computer applications for structural engineering. / Master of Science

Approximately fifty percent of the bridges in the United States are considered deficient. The deterioration of the concrete components is a leading cause of the problem. The deterioration of concrete bridge decks is due primarily to corrosion of the reinforcing steel in the concrete. A promising solution to the problem is the use of fiber reinforced plastics (FRP) as a replacement for reinforcing steel. The use of FRP as reinforcement has the following advantages of lightweight, high tensile strength, corrosion resistance, flexibility, and electromagnetic resistance. This paper looks at the use of FRP as reinforcement in concrete beams and compares the information from deflection measurements of different configurations. Also, a material cost comparison is made to determine the cost of using the FRP reinforcement over standard steel reinforcement. Concrete bridge deck systems are designed using steel and fiber-reinforced plastics and allowable stress and load resistance factor methods. Recommendations for further study and uses of FRP are made. / Master of Science

Economical constraints on the design of bridges usually necessitate the use of as few girders as possible across the bridge width. The girders are typically uniformly spaced transversely with the deck extending past the fascia girders, thereby resulting in an overhang. While designers commonly employ rules of thumb with regard to the geometry of the overhang, these rules of thumb generally lack research justification and the actual girder behavior is not well understood. Overhang construction often produces torsinally unbalanced loading on the girder system, which can lead to problems in steel and concrete girder bridges during construction. The main issue with concrete girder bridges is excessive lateral rotation in the fascia girder, which can cause potential problems of construction safety and maintenance. Field problems on concrete bridges have been reported in the state of Texas where the fascia girders experienced excessive rotation during construction. For steel girder bridges, the unbalanced overhang loading can lead to both local and global instability. Locally, the overhang brackets often exert a large force on the web plate that can distort the web and increase the magnitude of the plate imperfection. Global stability problems have also occurred primarily on bridge widening projects when a few girders are added to an existing bridge system. The girders in the widening are usually isolated from the existing bridge and the unbalanced load from the overhang can cause excessive twist that intensifies the global stability of the girder system. The objective of this study was to improve the understanding of the bridge behavior due to the unbalanced loading from the overhangs and to identify critical factors affecting the girder behavior. The study was also aimed at developing simple design methodologies and design recommendations for overhang construction. The research included field monitoring, laboratory tests, and parametric finite element analyses. The data from the field monitoring and laboratory tests were used to validate finite element models for both concrete and steel girder bridges. Based on the validated models, detailed parametric studies were conducted to investigate the effects of the unbalanced loading. Results from the parametric studies were used to identify the geometries of girder systems that are prone to problems with the overhangs as well as to provide design suggestions. In addition, a closed-form solution for lateral rotation in the fascia girder in a concrete girder bridge was derived using a rigid-body model, and was used to develop design methodology and design recommendations for overhang construction. / text

Master of Science / Department of Civil Engineering / Robert J. Peterman / Concrete box culvert floor slabs are known to have detrimental effects on river and stream hydraulics. Consequences include an aquatic environment less friendly to the passage of fish and other organisms. This has prompted environmental regulations restricting construction of traditional, four-sided box culvert structures in rivers and streams populated by protected species. The box culvert standard currently used by the Kansas Department of Transportation (KDOT) is likely to receive increased scrutiny from federal and state environmental regulators in the near future. Additionally, multiple-cell box culverts present a maintenance challenge, since passing driftwood and debris are frequently caught in the barrels and around cell walls. As more structures reach the end of their design lives, new solutions must be developed to facilitate a more suitable replacement. Since construction can cause significant delays to the traveling public, systems and techniques which accelerate the construction process should also be considered. This thesis documents development of a single-span replacement system for box culverts in the state of Kansas. Solutions were found using either a flab slab or the center span of the KDOT three-span, haunched-slab bridge standard. In both cases, the concrete superstructure is connected monolithically with a set of abutment walls, which sit on piling. The system provides an undisturbed, natural channel bottom, satisfying environmental regulations. Important structural, construction, maintenance, and economic criteria considered during the planning stages of bridge design are discussed. While both superstructural systems were found to perform acceptably, the haunched section was chosen for preliminary design. Rationale for selection of this system is explained. Structural modeling, analysis, and design data are presented to demonstrate viability of the system for spans ranging from 32 to 72 feet. The new system is expected to meet KDOT’s needs for structural, environmental, and hydraulic performance, as well as long-term durability. Another option involving accelerated bridge construction (ABC) practices is discussed.

<p>The strut-and-tie method (STM) is a powerful tool used for the design of D-regions (disturbed regions) of reinforced concrete structures. Many typical bridge substructure components consist of D-regions and require the use of the STM for design. Implementation of the STM is more complex than typical design methods, and engineers are often unfamiliar with the design process. As a result, designing using the STM is more time consuming than traditional design methods. The Indiana Department of Transportation (INDOT) identified a need for a tool that assists with the design of typical bridge substructure components using the STM. STEP (Strut-and-Tie Evaluation Program) is a computer program created to fulfill this role. To use the computer program, engineers input geometric conditions, material properties, and reinforcement information for a structural component. STEP uses this information to develop a strut-and-tie model and perform STM design procedures. A graphical representation of the model and a summary of the design results are provided as program outputs for the user.</p> <p> </p> <p>STEP, created using Excel VBA, is intended to aid in the design of multi-column bent caps and integral and semi-integral end bent caps. Within this thesis, an overview of the STM is provided, including the basic procedures for designing using the STM. An introduction to Excel VBA is also presented. The document describes the layout and formatting of the computer program, required user inputs, and program outputs. Furthermore, limitations and assumptions within the computer program for the substructure components are also included. Finally, design examples focused on the use of STEP for the design of a five-column bent cap and an integral end bent cap are presented. This document can be used as a resource for engineers when designing bridge substructure components using STEP. </p>

Self-consolidating concrete (SCC) is a new, innovative construction material that can be placed into forms without the need for mechanical vibration. The mixture proportions are critical for producing quality SCC and require an optimized combination of coarse and fine aggregates, cement, water, and chemical and mineral admixtures. The required mixture constituents and proportions may affect the mechanical properties, bond characteristics, and long-term behavior, and SCC may not provide the same inservice performance as conventional concrete (CC). Different SCC mixture constituents and proportions were evaluated for mechanical properties, shear characteristics, bond characteristics, creep, and durability. Variables evaluated included mixture type (CC or SCC), coarse aggregate type (river gravel or limestone), and coarse aggregate volume. To correlate these results with full-scale samples and investigate structural behavior related to strand bond properties, four girder-deck systems, 40 ft (12 m) long, with CC and SCC pretensioned girders were fabricated and tested. Results from the research indicate that the American Association of State Highway Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) Specifications can be used to estimate the mechanical properties of SCC for a concrete compressive strength range of 5 to 10 ksi (34 to 70 MPa). In addition, the research team developed prediction equations for concrete compressive strength ranges from 5 to 16 ksi (34 to 110 MPa). With respect to shear characteristics, a more appropriate expression is proposed to estimate the concrete shear strength for CC and SCC girders with a compressive strength greater than 10 ksi (70 MPa). The author found that girder-deck systems with Type A SCC girders exhibit similar flexural performance as deck-systems with CC girders. The AASHTO LRFD (2006) equations for computing the cracking moment, nominal moment, transfer length, development length, and prestress losses may be used for SCC girder-deck systems similar to those tested in this study. For environments exhibiting freeze-thaw cycles, a minimum 16-hour release strength of 7 ksi (48 MPa) is recommended for SCC mixtures.

The purpose of this thesis is to provide insight into how different geometric parameters such as tower height, girder depth, and pier dimensions influence the structural behaviour, cost, and feasibility of an extradosed bridge. A study of 51 extradosed bridges shows the variability in proportions and use of extradosed bridges, and compares their material quantities and structural characteristics to girder and cable-stayed bridges. The strategies and factors that must be considered in the design of an extradosed bridge are discussed. Two cantilever constructed girder bridges, an extradosed bridge with stiff girder, and an extradosed bridge with stiff tower are designed for a three span bridge with central span of 140 m. The structural behaviour, materials utilisation, and costs of each bridge are compared. Providing stiffness either in the girder or in the piers of an extradosed bridge are both found to be effective stategies that lead to competitive designs.

Span-to-depth ratio is an important bridge design parameter that affects structural behaviour, construction costs and aesthetics. A study of 86 constant-depth girders indicates that conventional ratios have not changed significantly since 1958. These conventional ratios are now questionable, because recently developed high-strength concrete has enhanced mechanical properties that allow for slenderer sections. Based on material consumption, cost, and aesthetics comparisons, the thesis determines optimal ratios of an 8-span highway viaduct constructed with high-strength concrete. Three bridge types are investigated: cast-in-place on falsework box-girder and solid slabs, and precast segmental span-by-span box-girder. Results demonstrate that total construction cost is relatively insensitive to span-to-depth ratio over the following ranges of ratios: 10-35, 30-45, and 15-25 for the three bridge types respectively. This finding leads to greater freedom for aesthetic expressions because, compared to conventional values (i.e. 18-23, 22-39, and 16-19), higher ranges of ratios can now be selected without significant cost premiums.