For decades, synthetic fibers have been utilized to improve the performance of concrete structures by enhancing the flexural strength, modulus of elasticity, and other mechanical properties of concrete. However, there are uncertainties about how synthetic fibers affect the coefficient of thermal expansion (CTE), dynamic modulus of elasticity, and flexural strength of the concrete under freeze-thaw cycles. This study was an investigation of the effect of temperature change on the mechanical properties of fiber-reinforced concrete, including CTE, dynamic modulus of elasticity, and flexural strength. Two types of synthetic fiber, polypropylene (PP) and polyvinyl alcohol (PVA) fibers, with three dosages for each type, 6, 7, and $9\mathrm{kg}/{\mathrm{m}}^3$ , were studied. The CTE was obtained using the severe temperature range specified by AASHTO specifications for measuring thermal effects in concrete bridge superstructures. Up to 300 freeze-thaw cycles were applied to specimens, while mass loss, dynamic modulus of elasticity, flexural strength, and CTE were measured in accordance with ASTM protocols. Adding fiber to concrete enhanced the flexural strength, increased the flexibility, decreased the dynamic modulus of elasticity, and increased the CTE. Specimens reinforced with PP fiber showed more flexural strength and flexibility than those reinforced with PVA fiber. Polyvinyl alcohol fiber–reinforced specimens exhibited greater CTE values compared with those reinforced with PP fiber. The added synthetic fiber enhanced the concrete’s resistance to freeze-thaw cycles. The optimum fiber dosage appears to be $7\mathrm{kg}/{\mathrm{m}}^3$ , which generally had the best performance in terms of flexural strength, dynamic modulus of elasticity, and CTE while best preserving structural integrity under repeated freezing and thawing.

The outstanding mechanical and bond strength properties of ultrahigh-performance concrete (UHPC), as well as its long-term durability, make it a suitable material to be used in connections of accelerated bridge construction (ABC). However, the long-term performance and durability of these connections depends on the interface performance between UHPC and prefabricated bridge elements. If debonding failure develops along the interface, the load transfer and durability of these connections may be compromised. This study examined the bond performance between high-strength concrete (HSC) and UHPC under direct tension stress states at different ages and using different surface preparations. The results from this study determined that a sufficient bond strength of UHPC could be assessed even at early ages when good surface preparation was utilized. Furthermore, the properties of the aggregate played a vital role in the interface bond strength. The bond versus slip was investigated at different ages and can be used in future analytical studies to obtain more accurate modeling of HSC–UHPC interfaces.

Adjacent box-girder bridges are commonly built in United States because of their fast, easy, and economical construction. They have shown good performance and service life except for frequent longitudinal cracking in the shear keys. Past research attributed the development of longitudinal cracks in shear keys primarily to temperature fluctuations. However, it is not obvious how temperature fluctuations cause the shear keys to crack. An adjacent box-girder bridge with partial depth shear keys and transverse tie bars was instrumented at the time of construction and subsequently monitored to study temperature effects. A finite-element model of the bridge was used to study the behavior of the bridge generally and failure modes that partial depth shear keys experience under daily and seasonal temperature fluctuations. The bridge girders move considerably in the transverse direction, and each girder expands or contract individually in response to temperature changes. The failure in the shear keys appeared to be caused by these environmental loads, which can be exacerbated by truck loads. Tie bars did little to stop this type of failure.

Adjacent box-girder bridges have become a popular choice as they can be constructed quickly, easily, and economically. In spite of their good performance during many years of service, one major problem has been recurrent longitudinal cracking of the grout material in the shear key. A combination of shear keys and transverse posttensioning (TPT) ties in such kind of bridges is typically used to connect the bridge girders together so that they would behave as a single integrated unit. However, information regarding the contribution of the TPT tie bars on load transfer between adjacent box girders is limited. In this study, a single-span precast prestressed concrete adjacent box-girder bridge was instrumented and monitored to study the effect of TPT tie bars on load transfer mechanism and overall bridge behavior under static and dynamic truck loads. Two sets of instruments were installed in the girders and tie bars during and after the construction of the bridge. A good correlation was achieved betwe...

Across the United States, a large number of corrugated steel pipes, installed three or four decades ago, are approaching the end of their useful service life. In many cases, these aging drainage structures are having significant degrees of metal loss over their inverts due to conveyance of abrasive surface water, which can be acidic in some regions. A metal culvert under Coopermill Road near Zanesville in Muskingum County, Ohio, was selected for replacement based on its advanced level of invert metal loss. Before its replacement, invert paving was done in the half of the culvert toward its outlet end. The other half toward the inlet end was left untreated. With the concrete fully cured, each half of the culvert was instrumented with strain gauges and string potentiometers. Each half was tested under an external load of up to 267 kN (60 kip) placed over the crown. The strains and deflections were measured from the sensors, and the corresponding stresses, thrusts, and bending moments were computed. Despite the highly deteriorated conditions, the culvert structure supported a load considerably larger than the legal limit of 80 kN (18 kip). The invert-paved section of the culvert responded to the load with smaller strains, deflections, and thrusts and moments. The stresses at the interface of the steel culvert and the poured concrete treatment were not very large.

Road managers require convenient, inexpensive methods to quickly assess pavement conditions over large areas. New imaging technologies potentially offer a substantial improvement over current methods. In this study, two hand-portable methods based on widely available consumer-grade technology were tested across a range of pavement conditions. To place the proposed methods in a familiar context, data were compared with the mean texture depth (MTD) calculated by the widely used volumetric method. MTD provided the clearest distinction between experimental roughness classes. Spatial pattern analysis (fractal dimension) of digital images discriminated between light, moderate and severe deterioration but failed to make fine distinctions between degrees of moderate wear. Three-dimensional models constructed by stereoscopic infrared scanning distinguished between all but the smoothest texture classes. It appears that both the proposed methods have potential for accurate, quick and convenient assessment of pavement macrotexture at little expense, although some judgement must be used in their application.