<p dir="ltr">Link slabs offer a cost-effective solution for eliminating deck expansion joints in multi-span bridges. A link slab is the cast-in-place concrete portion that makes only the deck slab continuous while the girders remain simply supported between two adjacent deck spans. By closing the expansion-joint opening, link slabs can reduce the costs of repairing and rehabilitating leaking joints and improving the bridge riding surface. Link slabs are designed to resist the bending moments imposed by girder end rotation due to live load plus impact, assuming the bridge spans are simply supported at the joints. The continuity provided by the link slab under live load is neglected, based on the assumption that its stiffness is lower than that of the girders. Furthermore, structural elements capable of load transfer (e.g., stirrups and shear stud connectors) within the limits of the deck joint elimination are often removed to reduce induced stresses in the link slab. A bond breaker is placed between the top of the girders and the bottom of the link slab to mitigate stresses. The debonded length, typically set at 5% of each span length, defines the total length of the link slab. Practices may vary among states, such as Indiana, where a composite action between the link slab and supporting girders is maintained. </p><p dir="ltr">However, increased cracking observed in the field is the primary concern about debonded link slabs. Once the cracks form, they allow the entrance of corrosive chemicals and debris, causing deterioration of concrete bridge components. The causes of the increased cracking and resulting leakage at the link slabs have been associated with the limitations of the existing design approaches in considering the effects of thermal loads and support conditions. This study presents a comprehensive finite element analysis to evaluate the behavior of bridge deck link slabs under the combined effect of traffic loads and vertical temperature gradients. The link slabs are subjected to HL-93 loading and temperature gradients following AASHTO LFRD Bridge Design Specifications. A finite element model of the Plott Creek Bridge in Haywood country in North Carolina, instrumented by Wing & Kowalksy (2005), is developed using ABAQUS/Standard software. The numerical model is validated against test data from previous studies available in the literature.</p><p dir="ltr">The results of the numerical investigation reveal that vehicular traffic loading is the primary factor contributing to the cracking of the link slabs. However, vertical temperature gradients are also identified as significant factors inducing stresses within the link slabs. Specifically, the combination of live load and a negative temperature gradient is the most influential loading condition contributing to cracking at the top surface of the link slabs. It is important to note that the rotation of the girder ends due to live load induces a negative moment (tension at the top) on the link slab. A negative temperature gradient, where the temperature on the top deck surface is lower than that on the web of the beams, results in an additional negative moment on the link slab due to its addition to the rotation from the live load. The temperature gradients are observed to increase the girder end rotation obtained from live load analysis for simply supported beams by approximately 20% in the range of parameters considered in the present study. This finding underscores the importance of considering temperature effects in link slab design to ensure structural integrity. </p><p dir="ltr">Furthermore, parametric studies are conducted to assess the impact of various factors such as girder support conditions, span length, debonded zone length, and material properties on crack initiation in link slabs. The analyses show that the primary factors affecting the tensile stress developed in the link slabs are the span length and the girder support conditions. This highlights the importance of considering these factors when designing link slabs. Based on the findings, design recommendations are proposed to enhance the current practices for link slab design. These recommendations include considering temperature gradients alongside live loads, adopting distributed bar spacing for crack control, and incorporating an allowable stress limit of 0.60fy for steel reinforcement following AASHTO LFRD Bridge Design Specifications. Given that link slabs exhibit cracking under service conditions, it is advisable to determine the amount of longitudinal tension reinforcement based on cracked section analysis rather than simply providing the minimum reinforcement. Furthermore, incorporating a debonded zone within 5% to 7.5% of the span length at each side of the link slab is recommended to reduce stresses. The use of roller support is not recommended for link slab applications, while hinge supports can be effective if the span length is less than 15~m (50~ft.). </p>

Consider the construction of a perspective drawing. The perspective is made by drawing lines between a point of origin and several focal points. A series of lines connect the focal points to one another. The culmination of lines drawn from origin to focal point and focal point to focal point describes a place. The perspective is a view, or window into this place. The relationship of these three elements - the origin, focal points, and view - is analogous to the development of a architectural project. The origin is a point of beginning. Each architect brings a set of experiences and ideas to the project. The project springs from the architects' knowledge and ideals. The focal points involve the design development of a project. They relate to the areas of study and discovery for the project. Some foci are specific to a site or program. Some foci further investigate design intentions and how they relate to a given program. The links between foci create a place. Each drawing or description of this place is a view into the project. This thesis outlines the origins, focal points and views of a design for a visitors' center located in southwestern Virginia. / Master of Architecture

Since the use of epoxy coated steel has become mandatory starting in the 1980s, recent studies have shown that epoxy coating does not prevent corrosion, but instead will debond from the steel reinforcement in as little as 4 years (Weyers RE et al, 1998) allowing instead a much more insidious form of corrosion to take place known as crevice corrosion. Therefore, it is important to determine if the nondestructive corrosion activity detection methods are applicable to ECR as well as institute guidelines for interpreting the results. Since the corrosion of reinforcing steel is directly responsible for damage to concrete structures, it is surprising that nondestructive corrosion assessment methods are not part of regular bridge inspection programs such as PONTIS and NBIS. Instead, the inspection and bridge rating guidelines of federally mandated programs such as NBIS are so vague as to allow for a relatively subjective application by the field inspectors. Clear cover depths, resistance, corrosion potentials, linear polarization data, as well as environmental exposure and structural data were collected from a sample of 38 bridge decks in the Commonwealth of Virginia. These structures were further divided in three subsets: bridge decks with a specified w/c ratio of 0.47, bridge decks with a specified w/c ratio of 0.45 and bridge decks with a specified w/cm ratio of 0.45. This data was then correlated to determine which parameters are the most influential in the assignment of NBIS condition rating. Relationships between the non-destructive test parameters were also examined to determine if corrosion potentials and linear polarization are applicable to epoxy coated steel. Based on comparisons of measurements distributions, there is an indication that corrosion potential tests may be applicable to structures reinforced with epoxy coated steel. Furthermore, these conclusions are supported by statistical correlations between resistivity, half cell potentials and linear polarization measurements. Unfortunately, although apparently applicable, as of now there are no guidelines to interpret the results. Based on the linear corrosion current density data collected, no conclusion can be drawn regarding the applicability of the linear polarization test. As far as the NBIS deck rating is concerned, since the inspection guidelines are so vague, age becomes a very easy and attractive factor to the field personnel to rely on. However, this conclusion is far from definitive since the very large majority of structures used in this particular study had only two rating values out of theoretically ten and realistically five possible rating values. / Master of Science

With the recent developments of several bridge managements systems and their wide-spread use, bridge engineers are realizing the importance of systematic and well planned investments and appropriate management. However the results are far from satisfactory. Bridge management systems need more effective policy analysis tools that can take advantage of the vast amounts of available information to be more efficient. The objective of this research is to develop a policy analysis tool, which is generic in nature and can be applied to any bridge management system provided all the appropriate data is available. In particular, this policy analysis tool is geared to suit policy making, planning and budgeting for the interstate bridges in the state of Virginia. The policy analysis tool developed in this research is a discrete event simulation model capable of extracting information from text files in the Pontis Data Interchange format and simulate user defined element level policies. The model testing was performed using the interstate bridges of the Salem district in Virginia. All the relevant information was extracted from their PONTIS databases. Several scenarios with varying network policies were simulated. The results indicate the validity and the accuracy of the model. The policy analysis tool is a useful addition to the existing policy analysis tools and is capable of handling probabilistic distributions of data instead of single value averages. This will enable the tool to capture more information thereby making the simulation model more realistic. The general framework that was developed here can be applied to any infrastructure problem, and eventually it should be possible to achieve a discrete event simulation based integrated infrastructure management system. / Master of Science

Studies have shown that over 30 percent of the bridges in the United States are structurally deficient, and/or over 50 years old. The majority of the highway bridges have reinforced concrete decks supported on steel or concrete girders. Over the years, weathering and deicing chemicals have caused spalling of the concrete surrounding the reinforcing steel, deteriorating many bridges to levels that often result in closure. Repairing or reconstructing the reinforced concrete deck to meet current design specifications is often not possible or feasible, and at times seems illogical due to the possibility of reoccurrence. Because of reinforced concrete's downfalls, there is a move toward alternative materials and designs for bridge deck replacements. In particular, Reynolds Metals Company has lead the movement toward the use of a shop-extruded aluminum deck system known as ALUMADECKTM. The purpose of this research is to evaluate data collected from full-scale testing under test truck loading of an in-service ALUMADECK bridge system. The bridge is known as the Little Buffalo Creek Bridge and is located in Mecklenburg County, VA. The topics researched from the load tests are the composite action amongst the deck and supporting members, the load distribution amongst supporting members, the dynamic load allowance for supporting members, and the developed deck stresses due to test truck loads. Evaluations of the research topics include comparisons to the methods employed in the design calculations provided by VDOT and to those of the American Association of State Highway and Transportation Officials (AASHTO) design specifications. / Master of Science

In this thesis technical and economic analysis of Fiber Reinforced Composite Polymer (FRPC) bridges was performed. Current condition and main issues of conventional bridges in the world and in Lithuania are assessed, main defects are indicated. In this thesis FRPC is considered as an alternative solution for bridge construction. Application range of FRPC for bridge construction is classified and actual bridge examples are analysed. Further, main properties of FRPC are introduced, taking into account influence of material composition, manufacturing technology, long term effects and advantages over conventional materials. Load-deformation, failure behavior analysis of FRPC bridge decks and bridges revealed advantages over conventional bridge solutions and design issues. In addition, existing codes for FRPC bridge design are analysed, design peculiarities are emphasized and current problems are identified. Performed Life Cycle Cost (LCC) analysis revealed financial viability of FRPC bridges. Finally, main conclusions and problems to be solved are stated and FRPC application potential for bridges construction in Lithuania is suggested. Performed analysis revealed that FRPC application for bridges construction is technically and economically viable solution. / Šiame magistriniame darbe atlikta Pluoštais Armuotų Polimerinių Kompozitinių (PAPK) tiltų techninė ir ekonominė analizė. Nagrinėjama esama pasaulio ir Lietuvos tiltų būklė, nustatytos būdingos problemos bei defektai. Šiame darbe PAPK yra svarstoma kaip alternativi medžiaga tiltų statybai. Atlikta PAPK panaudojimo klasifikacija tiltų statybai, analizuojami esami PAPK tiltų pavyzdžiai bei jų paplitimas. Toliau nustatomos mechaninės bei fizinės PAPK savybės, atsižvelgiant į medžiagos sandarą, gamybos būdą, ilagalaikius veiksnius ir privalumus lyginant su plienu ir gelžbetoniu. Pagal atliktą PAPK tiltų ir perdangų apkrovos-deformacijų, suirimo analizę nustatyta elementų elgsena, pateiktos pagrindinės problemos bei privalumai palyginus su tradiciniais tiltų sprendiniais. Taip pat išnagrinėtos PAPK tiltų projektavimų normos, pateikti skaičiavimų ypatumai bei problemos. Paskutiniame skyriuje atlikta Gyvavimo Ciklo Kainos analizė parodė PAPK tiltų finansinį įgyvendinamumą. Darbo pabaigoje pateikiamos pagrindinės išvados, rezultatai, spręstinos problemos bei PAPK tiltų panaudojimo rekomendacijos Lietuvoje. Atlikta techninė ir ekonominė analizė parodė, jog PAPK panaudojimas tiltų statybai yra techniškai ir ekonomiškai efektyvus sprendimas.

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.

Master of Science / Department of Civil Engineering / Hani G. Melhem / Fiber Reinforced Polymer (FRP) is a relatively new material used in the field of civil engineering. FRP is composed of fibers, usually carbon or glass, bonded together using a polymer adhesive and formed into the desired structural shape. Recently, FRP deck panels have been viewed as an attractive alternative to concrete decks when replacing deteriorated bridges. The main advantages of an FRP deck are its weight (roughly 75% lighter than concrete), its high strength-to-weight ratio, and its resistance to deterioration. In bridge design, AASHTO provides load distributions to be used when determining how much load a longitudinal beam supporting a bridge deck should be designed to hold. Depending on the deck material along with other variables, a different design distribution will be used. Since FRP is a relatively new material used for bridge design, there are no provisions in the AASHTO code that provides a load distribution when designing beams supporting an FRP deck. FRP deck panels, measuring 6 ft x 8.5’, were loaded and analyzed at KSU over the past 4 years. The research conducted provides insight towards a conservative load distribution to assist engineers in future bridge designs with FRP decks. Two separate test periods produced data for this thesis. For the first test period, throughout the year of 2007, a continuous FRP panel was set up at the Civil Infrastructure Systems Laboratory at Kansas State University. This continuous panel measured 8.5 ft by 6 ft x 6 in. thick and was supported by 4 Grade A572 HP 10 x 42 steel beams. The beam spacing’s, along the 8.5 ft direction, were 2.5 ft-3.5 ft-2.5 ft. Stain gauges were mounted at mid-span of each beam to monitor the amount of load each beam was taking under a certain load. Linear variable distribution transformers (LVDT) were mounted at mid-span of each beam to measure deflection. Loads were placed at the center of the panel, with reference to the 6 ft direction and at several locations along the 8.5 ft direction. Strain and deflection readings were taken in order to determine the amount of load each beam resisted for each load location. The second period of testing started in the fall of 2010 and extended into January of 2011. This consisted of a simple-span/cantilever test set-up. The test set-up consisted of, in the 8.5 ft direction, a simply supported span of 6 ft with a 2.5 ft cantilever on one side. As done previously both beams had strain gauges along with LVDTs mounted at mid-span. There were also strain gauges were installed spaced at 1.5ft increments along one beam in order to analyze the beam behavior under certain loads. Loads were once again applied in the center of the 6 ft direction and strain and deflection readings were taken at several load locations along the 8.5 ft direction. The data was analyzed after all testing was completed. The readings from the strain gauges mounted in 1.5 ft increments along the steel beam on one side of the simple span test set-up were used to produce moment curves for the steel beam at various load locations. These moment curves were analyzed to determine how much of the panel was effectively acting on the beam when loads were placed at various distances away from the beam. Using these “effective lengths,” along with the strain taken from the mid-span of each beam, the loads each beam was resisting for different load locations were determined for both the continuously supported panel and the simply supported/cantilever panel data. Using these loads, conservative design factors were determined for FRP panels. These factors are S/5.05 for the simply supported panel and S/4.4 for the continuous panel, where “S” is the support beam spacing. Deflections measurements were used to validate the results. Percent errors, based on experimental and theoretical deflections, were found to be in the range of 10 percent to 40 percent depending on the load locations for the results in this thesis.

The scheduled replacement of the 8th North Bridge, in Salt Lake City, UT, presented a unique opportunity to test a pre-cast concrete deck, steel girder bridge. A live-load test was performed under the directions of Bridge Diagnostic Inc (BDI) and Utah State University. Six different load paths were chosen to be tested. The recorded data was used to calibrate a finite-element model of this superstructure, which was created using solid, shell, and frame elements. A comparison between the measured and finite-element response was performed and it was determined that the finite-element model replicated the measured results within 3.5% of the actual values. This model was later used to obtain theoretical live-load distribution factors, which were compared with the AASHTO LRFD Specifications estimations. The analysis was performed for the actual condition of the bridge and the original case of the bridge, which included sidewalks on both sides. The comparison showed that the code over predicted the behavior of the actual structure by 10%. For the original case, the code's estimation differed by as much as 45% of the theoretical values. Another opportunity was presented to test the behavior of a cast-in-place concrete box girder bridge in Joaquin County, CA. The Walnut Grove Bridge was tested by BDI at the request of Utah State University. The test was performed with six different load paths and the recorded data was used to calibrate a finite-element model of the structure. The bridge was modeled using shell elements and the supports were modeled using solid elements. The model was shown to replicate the actual behavior of the bridge to within 3% of the measured values. The calibrated model was then used to calculate the theoretical live-load distribution factors, which allowed a comparison of the results with the AASHTOO LRFD Specifications equations. This analysis was performed for the real conditions of the bridge and a second case where intermediate diaphragms were not included. It was determined that the code's equations estimated the behavior of the interior girder more accurately for the second model (within 10%) than the real model of the bridge (within 20%).

Railroad bridges are the most important connection parts of railroad networks. These bridges are exposed to heavier train loads compared to highway bridges as well as various detrimental ambient conditions during their life span. The railroad bridges in Turkey are mostly constructed during the late Ottoman and first periods of the Turkish Republic / therefore, they are generally close to about 100 years of age / their inspection and maintenance works are essential. Structural health monitoring (SHM) techniques are widely used around the world in order to increase the effectiveness of the inspection and maintenance works and also evaluate structural reliability. Application of SHM methods on railway bridges by static and dynamic measurements over short and long durations give important structural information about bridge members&rsquo / load level and overall bridge structure in terms of vibration frequencies, deflections, etc. Structural Reliability analysis provides further information about the safety of a structural system and becomes even more efficient when combined with the SHM studies. In this study, computer modeling and SHM techniques are used for identifying structural condition of a steel truss railroad bridge in Usak, Turkey, which is composed of six spans with 30 m length each. The first two spans of the bridge were rebuilt about 50 years ago, which had construction plans and are selected as pilot case for SHM and evaluation studies in this thesis. Natural frequencies are obtained by using 4 accelerometers and a dynamic data acquisition system (DAS). Furthermore, mid span vertical deflection member strains and bridge accelerations are obtained using a DAS permanently left on site and then compared with the computer model analyses results. SHM system is programmed for triggering by the rail load sensors developed at METU and an LVDT to collect mid span deflection high speed data from all sensors during train passage. The DAS is also programmed to collect slow speed data (once at every 15 minutes) for determination of average ambient conditions such as temperature and humidity and all bridge sensors during long term monitoring. Structural capacity and reliability indices for stress levels of bridge members are determined for the measured and simulated train loads to determine structural condition of bridge members and connections. Earthquake analyses and design checks for bridge members are also conducted within the scope of this study.