Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 32
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.
