Yes / This paper proposes a new design concept for a steel truss-reinforced concrete box girder which incorporates a steel truss instead of longitudinal bars and stirrups. A comprehensive assessment of the flexural and shear behavior of the proposed steel truss-reinforced concrete box girders was conducted through the testing of twelve girders until failure. All test specimens had the same concrete depth and width of 400 mm and 300 mm, but the length of concrete in the shear and flexural specimens were 3300 mm and 3100 mm, respectively. Moreover, the reinforcing steel truss configuration and member sizes were different. The effects of the angle steel size of the lower chord, vertical webs spacing, shear span ratio and presence of diagonal webs on the cracking, yield and ultimate loads, crack patterns, failure modes, vertical load-deflection curves and strain distribution of these steel truss-reinforced concrete box girders were studied. The test results showed that the flexural capacity of the steel truss-reinforced concrete box girder increases with the increase of angle steel size of the lower chord. Moreover, the spacing of vertical webs and presence of diagonal webs have little effect on the flexural capacity of steel truss-reinforced concrete box girders tested. With the decrease of the shear span ratio and vertical webs spacing, the shear capacity of the steel truss-reinforced concrete box girder increases. Finally, simplified formulae for calculating the flexural and shear capacities of steel truss-reinforced concrete box girders were proposed, showing good agreement with the experimental results.

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%).

Live load distribution factors are used to determine the live-load moment for bridge girder design when a two dimensional analysis is conducted. A simple, analysis of bridge superstructures are considered to determine live-load factors that can be used to analyze different types of bridges. The distribution of the live load factors distributes the effect of loads transversely across the width of the bridge superstructure by proportioning the design lanes to individual girders through the distribution factors. This research study consists of the determination of live load distribution factors (LLDFs) in both interior and exterior girders for horizontally curved concrete box girder bridges that have central angles, with one span exceeding 34 degrees. This study has been done based on real geometry of bridges designed by a company for different locations. The goal of using real geometry is to achieve more realistic, accurate, and practical results. Also, in this study, 3-D modeling analyses for different span lengths (80, 90, 100, 115, 120, and 140 ft) have been first conducted for straight bridges, and then the results compared with AASHTO LRFD, 2012 equations. The point of starting with straight bridges analyses is to get an indication and conception about the LLDF obtained from AASHTO LRFD formulas, 2012 to those obtained from finite element analyses for this type of bridge (Concrete Box Girder). After that, the analyses have been done for curved bridges having central angles with one span exceeding 34 degrees. Theses analyses conducted for various span lengths that had already been used for straight bridges (80, 90, 100, 115, 120, and 140 ft) with different central angles (5º, 38º, 45º, 50º, 55º, and 60º). The results of modeling and analyses for straight bridges indicate that the current AASHTO LRFD formulas for box-girder bridges provide a conservative estimate of the design bending moment. For curved bridges, it was observed from a refined analysis that the distribution factor increases as the central angle increases and the current AASHTO LRFD formula is applicable until a central angle of 38º which is a little out of the LRFD`s limits.

My thesis is focused on a design and comparism of the highway bridge across Dolansky creek. The bridge is built by balanced cantilever method. The common span length is 110metres. The bridge is post-tensioned concrete structure.The static model is made of beams.The static analysis during lifespan of bridge is made by Time discretization analysis . The design of reinforcement is made for longitudinal section and cross section.