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Fiber-Reinforced Polymer (FRP) plates and fabrics have emerged as viable systems for retrofitting of existing reinforced concrete members with insufficient capacity. The results from previous research, conducted predominately on newly cast laboratory specimens, have been used to develop design guidelines. Detailed testing and evaluation of aged members retrofitted with FRP systems are very limited. This research is conducted to fill this gap. A 45-year old, three-span reinforced concrete slab bridge with insufficient capacity was retrofitted with 76.2 and 127-mm wide CFRP plates, 102-mm wide bonded CFRP plates with mechanical anchors at the ends, and bonded CFRP fabrics. Using four systems in one bridge provided an opportunity to evaluate field installation issues, and long-term performance of each system under identical traffic and environmental conditions. Through controlled truckload tests, the response of the bridge before retrofitting, shortly after retrofitting, and after one year of service was measured. The FRP system's stiffness was small in comparison to the stiffness of the bridge deck, therefore the measured deflections did not noticeably change after retrofitting. The measured strains suggest participation of the FRP systems, and more importantly the strength of the retrofitted bridge was increased. Detailed three-dimensional finite element models of the original and retrofitted bridge was developed and calibrated based on the measured deflections. Those models were used to calculate the rating factors and the corresponding load limits, which increased by 22% after retrofitting. In view of the increased capacity and performance of the bridge, load limits were removed and normal traffic was resumed.
Four 76-year old T reinforced concrete beams were retrofitted with four different systems employing carbon fiber polymer reinforced (CFRP) composites to examine the success of FRP systems to strengthen aged members with substantial deterioration. The beams were removed from FAI-37-2899 and FAI-37-2915. The systems used in this project were (a) external post-tensioning system with CFRP rods, (b) bonded CFRP plates, (c) bonded CFRP fabrics, and (d) bonded CFRP plates with mechanical anchors at the ends of the plates. The experimental data were augmented with analytical results to better understand the observed behavior, particularly when visual data or the measured data were insufficient.
Rising awareness of and increased attention to sexual harassment has resulted in momentum to implement sexual harassment prevention efforts in higher education institutions. Work on preventing sexual harassment is an area that has recently garnered a lot of attention, especially around education and programs that go beyond the standard anti-sexual harassment trainings often used to comply with legal requirements. On April 20-21, 2021, the National Academies of Sciences, Engineering, and Medicine hosted the workshop Developing Evaluation Metrics for Sexual Harassment Prevention Efforts. The workshop explored approaches and strategies for evaluating and measuring the effectiveness of sexual harassment interventions being implemented at higher education institutions and research and training sites, in order to assist institutions in transforming promising ideas into evidence-based best practices. Workshop participants also addressed methods, metrics, and measures that could be used to evaluate sexual harassment prevention efforts that lead to change in the organizational climate and culture and/or a change in behavior among community members. This publication summarizes the presentations and discussion of the workshop.
This chapter first reviews current structural applications of fiber-reinforced polymer (FRP) composites in bridge structures, and describes advantages of FRP in bridge applications. This chapter then introduces the design of a hybrid FRP-concrete bridge superstructure, which has been developed at The University at Buffalo for the past ten years, and discusses structural performance of the superstructure based on extensive experimental and analytical studies.
Viable retrofit schemes are necessary to delay or offset replacement of deteriorating concrete bridge members. Carbon fiber reinforced polymer (CFRP) pultruded plates can be especially effective when retrofitting bridge members where stiffness, fatigue resistance, ease of installation, and weathering characteristics are a concern. The research reported in Chapter 1 was undertaken to examine the influence of fatigue loading, prior cracking, and patch materials on flexural performance of reinforced concrete members retrofitted with externally bonded CFRP plates. Moreover, experimental data from the six reinforced concrete beams tested as part of this research are expected to further evaluate available design equations for external retrofitting of reinforced concrete structures. The test results do not suggest a significant effect of fatigue loads; show that existing cracks do not significantly impact the strength of retrofitted members; and indicate that patch materials can reduce the available bond strength, and require additional surface preparation. The research reported in Chapter 2 presents a novel design approach utilizing externally bonded CFRP plates developed in an attempt to overcome construction errors in a member removed from an adjacent box girder bridge. The design methodology was evaluated based on data from testing of a retrofitted girder along with previous tests on as-is girders. Test data suggest appreciable improvements in terms of load carrying capacity and stiffness of the retrofitted girder. The relatively simple retrofit plan developed could have been used to delay replacement of the deficient girders. The research reported in Chapter 3 is aimed at filling some of the gaps in the available test data through retrofitting and testing of a 18.3 m (60 ft) prestressed box girder retrofitted with CFRP composite plates with mechanical anchors. Prior research on the use of CFRPs for retrofitting of existing structures has predominantly focused on mildly reinforced concrete members, and application to prestressed members is rather limited. Moreover, data regarding performance of mechanical anchors for enhancing bond characteristics of CFRP composites are scant. After a description of the design procedure, the test data are used to evaluate the design method, current design recommendations, and performance of mechanical anchors.
High strength fibre composites (FRPs) have been used with civil structures since the 1980s, mostly in the repair, strengthening and retrofitting of concrete structures. This has attracted considerable research, and the industry has expanded exponentially in the last decade. Design guidelines have been developed by professional organizations in a number of countries including USA, Japan, Europe and China, but until now designers have had no publication which provides practical guidance or accessible coverage of the fundamentals. This book fills this void. It deals with the fundamentals of composites, and basic design principles, and provides step-by-step guidelines for design. Its main theme is the repair and retrofit of un-reinforced, reinforced and prestressed concrete structures using carbon, glass and other high strength fibre composites. In the case of beams, the focus is on their strengthening for flexure and shear or their stiffening. The main interest with columns is the improvement of their ductility; and both strengthening and ductility improvement of un-reinforced structures are covered. Methods for evaluating the strengthened structures are presented. Step by step procedures are set out, including flow charts, for the various structural components, and design examples and practice problems are used to illustrate. As infrastructure ages worldwide, and its demolition and replacement becomes less of an option, the need for repair and retrofit of existing facilities will increase. Besides its audience of design professionals, this book suits graduate and advanced undergraduate students.
TRB's National Cooperative Highway Research Program (NCHRP) Report 655: Recommended Guide Specification for the Design of Externally Bonded FRP Systems for Repair and Strengthening of Concrete Bridge Elements examines a recommended guide specification for the design of externally bonded Fiber-Reinforced Polymer (FRP) systems for the repair and strengthening of concrete bridge elements. The report addresses the design requirements for members subjected to different loading conditions including flexure, shear and torsion, and combined axial force and flexure. The recommended guide specification is supplemented by design examples to illustrate its use for different FRP strengthening applications.
The global response to COVID-19 has demonstrated the importance of vigilance and preparedness for infectious diseases, particularly influenza. There is a need for more effective influenza vaccines and modern manufacturing technologies that are adaptable and scalable to meet demand during a pandemic. The rapid development of COVID-19 vaccines has demonstrated what is possible with extensive data sharing, researchers who have the necessary resources and novel technologies to conduct and apply their research, rolling review by regulators, and public-private partnerships. As demonstrated throughout the response to COVID-19, the process of research and development of novel vaccines can be significantly optimized when stakeholders are provided with the resources and technologies needed to support their response. Vaccine Research and Development to Advance Pandemic and Seasonal Influenza Preparedness and Response focuses on how to leverage the knowledge gained from the COVID-19 pandemic to optimize vaccine research and development (R&D) to support the prevention and control of seasonal and pandemic influenza. The committee's findings address four dimensions of vaccine R&D: (1) basic and translational science, (2) clinical science, (3) manufacturing science, and (4) regulatory science.