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1CHAPTER 1 INTRODUCTION RESEARCH PROBLEM STATEMENT In response to local expectations and the traveling public, there is a national need for aesthetic improvement of typical highway features. Requests for barrier treatments and bridge rails that contribute to the overall aesthetic experience are increasing. Research will assist owners in responding to design requests for aesthetic improvements to transportation systems. Concrete barriers (e.g., New Jersey, F-shape, and single- slope, and vertical-face designs) are often the barriers of choice in urban and suburban environments. Many agencies and com- munities have expressed a desire for aesthetic treatments for these standard shapes. To date, there has been limited evalu- ation to determine which aesthetic treatments are safe and prac- tical. Current standards do not provide guidelines to improve the appearance of concrete barriers. Local communities and agencies are also demanding increasingly that state DOTs provide bridge rails with an enhanced âsee-throughâ appearance. Existing designs do not fully meet the desire of the public for a see-through appear- ance. However, the use of innovative designs and materials may result in the development of aesthetic bridge rails with improved view spaces. Designers need guidelines for aesthetic treatments of con- crete barriers and additional options for see-through bridge rails. RESEARCH OBJECTIVE The initial objectives of this research were to (1) assemble a collection of examples of longitudinal traffic barriers exhibit- ing aesthetic characteristics; (2) develop design guidelines for aesthetic concrete roadway barriers; and (3) develop spe- cific designs for see-through bridge rails. Following the submittal of the project interim report and the project panel membersâ meeting with the researchers, the scope of the project and research objectives were modified to only (1) assemble a collection of examples of longitudinal traf- fic barriers exhibiting aesthetic characteristics and (2) develop engineering design guidelines for aesthetic surface treatments of concrete safety shape barriers (e.g., New Jersey and F-shape profiles). Design guidelines for single-slope and vertical- face concrete barriers had been finalized after the initiation of this project in a California DOT study that is discussed in this report. This report summarizes the entirety of the findings of the project, including work performed prior to the modification of the scope and objectives. Chapters 2 and 3 focus on the work performed by the researchers prior to the modification of the scope and objectives. Chapter 2 summarizes (1) the state of the practice pertaining to the features and methods that contribute to the aesthetics of longitudinal barriers and the aesthetic experience provided by the roadway; (2) the lit- erature reviewed; and (3) the use of aesthetic longitudinal traffic barriers and treatments as identified through a survey of U.S. and foreign sources. Many aesthetic barrier examples were provided by transportation organizations from around the world and are presented in Chapter 2. Chapter 3 focuses primarily on barrier form and how it is perceived by the driver in its environment. The chapter defines aesthetics and discusses assessment, factors, and techniques for changing the aesthetic character of longitudinal concrete barriers. In addition, Chapter 3 discusses a viewer preference survey that was performed. Chapter 4 describes the development approach for the aesthetic concrete barrier design guideline. Chapter 5 describes the finite element simulation pilot study, model validation, and development of a surrogate measure of occu- pant compartment deformation. In addition, Chapter 5 pre- sents preliminary design guidelines based on finite element simulation. Chapter 6 presents the selection considerations and results of the full-scale crash tests performed in support of the finite element simulations and the development of the final design guidelines. The final design guidelines for aes- thetic safety shape concrete barrier design are presented in Chapter 7.
