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The Bridge Street Bridge project represents the successful transfer of the technology developed from one of the ongoing research projects conducted at the Structural Testing Center by LTU research team. This research project was funded by the National Science Foundation, Michigan Department of Transportation, American Concrete Institute, Mitsubishi Chemical Functional Co., Tokyo Rope Mfg. Co., Ltd., and the City of Southfield. The research project was conducted under the direction of Dr. Nabil Grace.
The Bridge Street Bridge in Southfield, MI, is the first vehicular concrete bridge ever built in the United States that uses carbon fiber reinforced polymer (CFRP) material as the principal structure reinforcement. From the surface, the Bridge Street Bridge Project in Southfield, Michigan does not appear to be much different than any other bridge installation. As the sole means of access to the Bridge Street Industrial Subdivision, the project consists of two parallel bridges with one serving incoming traffic and the other, outgoing. Each is constructed of reinforced concrete with similar traffic barrier and sidewalk configurations. This similarity of appearance belies the radical difference in the actual structures with regard to their reinforcement systems and materials.
The lack of availability of design guidelines and technical data for the use of carbon fiber reinforced polymer (CFRP) reinforcements has contributed significantly to the delay in using composites materials in prestressed concrete bridges in the US.
Consequently, no single prestressed concrete bridge using CFRP has been constructed or even considered by any government agency. As a result, the use of CFRP reinforcements in the US has been limited to research activities and subsequent technical publications. The proposed research program is tailored to develop design guidelines to aid the designers to safely design CFRP prestressed structural components, and to construct a one-half scale bridge model and two prestressed concrete girders and test them under different loading conditions. The proposed investigation will result in technical data that will be adopted in the construction of the first authorized CFRP prestressed concrete bridge inn the US. Furthermore, future prestressed concrete bridge projects that will be undertaken by the supporting state agencies will benefit significantly from the generated data.
This research presents a new concept dealing with the development of a multi-span continuously pre-stressed concrete bridge system that requires no shoring or forms and has superior characteristics compared to conventional continuous bridge systems. The non-corrosive bridge system will be built of: (i) modified pre-cast pre-tensioned, with internal carbon fiber reinforced plastic (CFRP) strands, Double-T (DT) girders, (ii) cast-in-place continuous deck, reinforced with glass carbon fiber reinforced plastic (GFRP or CFRP) re-bars, connected to the DT through CFRP or GFRP shear connectors, and (iii) externally draped continuous CFRP post-tension strands. An analytical and experimental study will be conducted by Junior and Senior undergraduate students to examine the static, dynamic, fatigue and ultimate load characteristics of the multi-span continuously prestressed new bridge system. These include cracking, flexural strength, punching shear strength, damping response, natural frequencies and associated mode shapes and fatigue strength. The multi-span continuously pre-stressed bridge system and its construction technique present a leap forward as well as a breakthrough in the development of a new approach for non-corrosive efficient bridges. It will result in considerable savings in construction time and costs and in the complete elimination of corrosion problems in future USA bridges.
The lack of ductility in these materials and the corresponding catastrophic failures of strengthened structures reported in several research investigations have contributed to the lack of confidence in composite materials for structural engineering and the subsequent delay in using them for the strengthening/stiffening of concrete structures in the United States.
To solve this problem, an innovative design of new FRP sheets needs to be introduced and evaluated in both laboratory and field. The study will consist of four phases. The first phase will address the development of an innovative three-axis braided FRP fabric that will be fabricated using a combination of carbon, aramid and glass fibers oriented in three different directions. These sheets will differ from the currently available, ineffective unidirectional and woven single fiber-type sheets, which have been evaluated at LTU and found to lack the necessary energy absorbing capability. The developed fabrics will provide ductile rather than brittle failure of strengthened structures. The second phase will deal with the construction, instrumentation and strengthening of simple, continuous, and cantilever test beams. The developed FRP braided fabric and the selected epoxy adhesive will be used for strengthening these beams. During phase four, results from the first three phases will be deployed into a practical application in the state of Ohio by ODOT.
The lack of availability of (1) design guidelines for the use of carbon fiber reinforced polymer (CFRP) reinforcements, (2) CFRP-test standards, and (3) low cost CFRP prestressing strands, stirrups and reinforcing rods has contributed significantly to the delay in using composite materials in prestressed concrete construction in the United States. Consequently, no single prestressed concrete bridge using CFRP materials has been constructed or even considered by bridge contractors or any government agency. As a result, the use of CFRP reinforcements in the US has been limited to research activities and subsequent technical publications.
Several states (DOTS Great Lakes Consortium) have realized the importance and the positive impact that this innovative/smart bridge system of the City of Southfield would have on developing new approaches for future construction of their highway bridges. As a result, Departments of Transportation (DOTS) in the following states are providing technical and financial support for the proposed research project: (1) Michigan (2) Ohio (3) Minnesota (4) New York and (5) Pennsylvania.
This research investigation is tailored to: (1) develop design guidelines to aid the designers to safely design CFRP prestressed structural components, (2) establish appropriate test standards for CFRP prestressing strands, stirrups, and flexural reinforcing rods, and (3) construct a one-half scale bridge model and two prestressed concrete girders and test them under different loading conditions. The proposed investigation will result in design guidelines and technical data that are essential for the design and construction of future CFRP prestressed concrete bridges by the supporting state agencies.
This project is a fundamental necessity, given the fact that a majority of the nation’s structures are over 30 years old. With limited funds these structures won’t be able to be replaced for years to come.
With increasing truckloads, the external composite strengthening approach is the only method of strengthening to prolong their life span. This investigation entails the testing required to determine the effects of the environment on the durability of external composite strengthening. The project will address the testing and performance evaluation of 81 FRP strengthened concrete beams and FRP coupon specimens subjected to various environmental conditions. These environmental conditions will include: (1) freeze/thaw, (2) repeated (fatigue) loading, (3) UV light, (4) water submersion/humidity, (5) saltwater, (6) alkali, and (7) dry heat exposure, as detailed in Table 1. The environmental exposures will be conducted in accordance with ASTM specifications.
Two types of fiber-reinforced polymer (FRP) will be used in this investigation. The test beams will be constructed, strengthened and subjected (with CFRP coupon specimens) to specific environmental conditions. After the completion of these accelerated environmental exposures, proper instrumentation will be applied to the test beams. Each beam will be subjected to four-point flexural load tests up to failure. Loading and unloading will be conducted to determine the level of the dissipated energy. A 30x12x12 environmental testing chamber of several capabilities is under construction in the STC. Several laboratories and skilled technicians will be supporting the various activities outlined in this proposal.
Two funded research projects are currently being conducted in the Structural Testing Center to develop CFRP drive shafts and suspension systems for the use in automotive applications. Three types of manufacturing are used:
The developed shafts are currently being tested under different torsional repeated torque and under various temperatures.
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