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32 CHAPTER 5 SIMULATION AND PRELIMINARY AESTHETIC DESIGN GUIDELINE DEVELOPMENT INTRODUCTION fered or beveled edges to minimize vehicular sheet metal or wheel snagging. Opening geometry in see-through rails, if improperly · Textures or patterns of any shape and length inset into the designed, can have a devastating effect on the rail's crash face of the barrier up to 13 mm deep and 25 mm wide. performance when struck by a vehicle. Likewise, in mono- Geometric insets with an upstream edge with an angle of lithic concrete barrier surfaces that are not see-through, sur- up to 90 degrees should be less than 13 mm deep. face discontinuities, protrusions, or depressions in the face of · Any pattern or texture with gradual undulations that have the barrier can introduce vehicle instability and/or snagging. a maximum relief of 20 mm over a distance of 300 mm. Surface discontinuities, protrusions, or depressions in the face · Gaps, slots, grooves, or joints of any depth with a max- of the rail or at rail openings may be acceptable, provided imum width of 20 mm and a maximum surface differ- their depth and/or geometry do not produce excessive vehic- ential across these features of 5 mm. ular snagging and excessive decelerations. The effect of · No patterns with a repeating upward sloping edge or ridge. architectural surface treatments is little understood and could · Any pattern or texture with a maximum relief of 64 mm, have significant safety-related effects. if such pattern begins 610 mm or higher above the base Native area stones can be applied as a veneer to enhance the of the barrier and all leading edges are rounded or sloped appearance of concrete barriers. To date, the FHWA's guide- to minimize any vehicle snagging potential. No part of lines for vertical-faced, crash-tested stone masonry guardwall this pattern or texture should protrude below the plane of state that maximum projections should not extend beyond the lower, untextured portion of the barrier. 38 mm of the neat line, deep raked joints should be 50 mm thick, and mortar beds should be 5075 mm thick. Stone Prior to the Caltrans study, there was a lack of any guidance that creates protrusions greater than described is not consid- regarding acceptable surface treatment of concrete barriers at ered crashworthy. Based on aesthetics and stone availabil- the national level, and little or no uniformity existed in aes- ity, a smoother stone face may be used, such as Class A or thetic barrier design among the states. While the Caltrans study B masonry. addressed single-slope and vertical-face concrete barriers, In addition to native stone, alternative methods of form- there was no design guidance for widely used safety shape ing concrete walls and barriers provide designers with a concrete barriers. The primary objective of this research was wide range of possible architectural treatments in the form to develop guidelines for the aesthetic surface treatment of of patterns and textures. Caltrans tested several architec- New Jersey and F-shaped concrete barriers (herein generally tural surface treatments applied to the Type 60 single-slope referred to generically as safety shape barriers) based on bar- (9.1-degree) concrete barrier and identified several textures rier impact performance. The guidelines are intended to aid and patterns that could be applied to the single-slope con- engineers and designers in choosing aesthetic surface treat- crete barrier. ments for concrete safety shape median and roadside barriers Crash testing of single-slope median barrier with aesthetic that will not adversely affect crashworthiness. surface treatments by Caltrans resulted in the first set of When considering the geometry of surface asperities, guidelines for the aesthetic surface treatment of concrete bar- variables include the depth, width, and shape of the relief riers. As a result of the Caltrans study, recommendations for or recess. Due to the number and range of these variables, allowable surface asperity geometry on the face of single- it was economically impractical to conduct a parametric slope and vertical-face barriers were developed. The guide- investigation based solely on crash testing. However, the lines, which were approved by the FHWA in acceptance let- researchers believed that a parametric investigation could be ter B-110, permit the following types of surface treatments: performed using finite element computer simulations that · Sandblasted textures with a maximum relief of 9.5 mm. can provide a detailed assessment of the three-dimensional · Images or geometric patterns cut into the face of the bar- impact response associated with the introduction of specific rier 25 mm or less and having 45-degree or flatter cham- aesthetic treatments.