In April of 2008, the Federal Highway Administration (FHWA) launched the Long Term Bridge Performance (LTBP) program. The program was established to collect scientific quality data from a number of bridges across the nation over a period of 20 years. The data will be used to provide a better picture of bridge health and structural performance. Utah Department of Transportation (UDOT) structure number 1F 205, located 2.4 km (1.5 mi) west of Perry, Utah, was selected as one of the LTBP pilot bridges (this bridge will also be referred to as the Cannery Street Overpass). UDOT performs regular maintenance on this bridge and in April of 2011 they began a rehabilitation project over a 13-km (8-mi) section of I-15 that included the Cannery Street Overpass. The main purpose of this rehabilitation was to improve pavement conditions. As part of this work, in the fall of 2011 UDOT removed all of the asphalt from the bridge deck, performed deck repairs, and placed a new asphalt layer. A unique opportunity presented itself to better understand the relationship between the mass and resonant vibration frequencies of the structure. This relationship is understood by (omega_n)^2=k/m, where omega_n=resonant frequency; k=stiffness; and m=mass. A decrease in mass should yield an increase in resonant frequency. Dynamic testing was done on the bridge to obtain its resonant frequencies. This testing included measuring the velocity response of the structure at different points on the bridge due to ambient vibrations (mainly from traffic). Three tests were performed before, during, and after UDOT's scheduled maintenance. These testing states include: State 1. Original asphalt on bridge deck State 2. No asphalt on bridge deck State 3. New asphalt on bridge deck These three states represent three different mass states of the bridge. The original asphalt layer was substantially heavier than the new asphalt layer. The data obtained from all three tests was processed in order to extract modal properties of the bridge. The changes in modal properties were analyzed and the results of the testing proved to be insightful at defining the relationship between mass and resonant frequency.

As part of the Long Term Bridge Performance (LTBP) Program, a single-span, prestressed, integral abutment concrete girder pilot bridge near Perry, Utah was instrumented with different sensors at various locations onto the bridge for long-term monitoring and periodic testing. One of the periodic tests conducted on this bridge was a live-load test. The live-load test included driving trucks across the bridge, as well as parking trucks along different lanes of the bridge, and measuring the deflection and strain. The data collected from these tests was used to create and calibrate a computer model of the bridge. The model was afforded the same dimensions and characteristics as the actual bridge, and then the boundary conditions (how the bridge is being supported) were altered until the model data and the live-load data matched. Live-load distribution factors and load ratings were then obtained using this calibrated model and compared to the AASHTO LRFD Bridge Design Specifications. The results indicated that in all cases, the AASHTO LRFD Specification distribution factors were conservative by between 55% to 78% due to neglecting to take the bridge fixity (bridge supports) into account in the distribution factor equations. The actual fixity of the bridge was determined to be 94%.Subsequently, a variable study was conducted by creating new models based on the original bridge for changes in span length, deck thickness, edge distance, skew (angle of distortion of the bridge), and fixity to see how each variable would affect the bridge. Distribution factors were then calculated for each case and compared with the distribution factors obtained from the AASHTO LRFD Specifications for each case. The results showed that the variables with the largest influence on the bridge were the change in fixity and the change in skew. Both parameters provided ranges between 10% non- conservative and 56% conservative. The parameter with the least amount of influence was the deck thickness providing a range between 4% non-conservative and 19% non- conservative. Depending on which variable was increased, both increases and decreases in conservatism were exhibited in the study.

Concrete girder bridges are a commonly used type of bridge which can be reinforced withboth regular and post-tensioned reinforcement. At a certain span length, the use of tensionreinforcement becomes a must because regular reinforcement won’t be enough. To get anidea of where this boundary lies, we studied a bridge in this research which is a half-throughbridge intended for railway traffic with the use of post-tensioned reinforcements. Thisbridge has a span of 22,15 metres and it is compared to bridges at the same span andshorter span using regular reinforcements. The analysis in this thesis is made using the finiteelementsprogram Brigade Standard.Two previously executed projects are used as references. A literature study will be carriedout initially, where Eurocodes, old examination projects and other literature on tensionreinforcement are examined.The acquired result is that the tension-reinforced bridge relates to a bridge with about 3/4span with regards to torque over the middle support. The torque over the support is thelimiting factor which causes an exponential increase in the amount of reinforcement atlonger spans. At about 20 metres the amount of necessary reinforcement starts to increaseexponentially and above this span post-tensioning is the preferred method.Torsion at the end support is also a crucial parameter since a regular-reinforced bridge with20-metre span cannot be reinforced to handle this with the current geometry. At a 20-metrespan, actions are therefore required to improve the torsion capacity, for example, increasingthe girder width. This increased girder width could be considered a saving in materials dueto the avoided increment of concrete in the case of tension-reinforced design, where thisincreased width is unnecessary.The total amount of reinforcement, independent of the reinforcement type, is greater in themiddle support of the regular reinforced bridge than the tension reinforced with the samespan. However, the total amount of reinforcement over the entire bridge is higher in thetension reinforced alternative.The result also shows that the tension reinforcement increases the compression force in thebridge and eliminates tension cracks which were expected according to our literature study.