Tiêu chuẩn quốc tế

• Số hiệu / Standard Number: AASHTO GSBR:1989
• Năm ban hành / Publication date: 1989
• Tình trạng / Status: W - Hết hiệu lực
• Tên tiếng Anh / Title in English: Guide Specifications for Bridge Railings
• Số trang / Page: 54

Phạm vi áp dụng / Scope of standard

These guide specifications have been developed to provide an
alternative to the bridge railing design procedures contained in
the fourteenth edition of the AASHTO Standard Specifications
for Highway Bridges. Because it is likely that these guide
specifications will become the basis for revisions to the standard
specifications, article numbers corresponding to comparable
articles in the standard specifications have been used in the guide
specifications, except that a letter "G" prefix has been added.

Two concepts underlie these guide specifications. The first is
that bridge railing designs should be crash tested to confirm that
they will meet the requirements of a specified railing performance
level. The second is that bridge railing performance needs differ
greatly from site to site over our highway network and that railing
designs. and costs, should match site needs (the multiple
performance levels concept).

Three bridge railing performance levels and associated crash
tests and Performance requirements are given in these guide
specifications, along with guidance for determining the appropriate
railing performance level for a given bridge site. Appendix A to
the guide specifications provides guidelines for the structural and
geometric design of railings that are likely to meet desired
performance level crash test requirements. (Appendix A is intended
for guidance only. Provisions therein are not requirements to be
imposed beyond the requirements of the guide specifications.)
Appendix B discusses the theory, data, and assumptions upon which
the guide specifications are based, along with the potential impact
of the specifications.

These guide specifications are applicable to railings for new
bridges and for bridges being rehabilitated to the extent that
railing replacement is obviously appropriate. They are not
applicable to determining the adequacy of existing railings. when
existing railings should be strengthened or replaced, or the method
or level of strengthening appropriate for upgrading a substandard
existing railing. Such determinations require special study, the
outcome of which will depend on site specific factors such as
the condition of the existing railing, its performance record (at
the site and elsewhere), traffic volume and mix, costs to effect
various levels of upgrade, expected time to major rehabilitation or
replacement of the bridge. etc. In general, because construction
and maintenance costs of the do-nothing option are usually very low
or zero, it will be rare that replacement or upgrading of an
in-place railing that does not have a recognized poor performance
record under its site specific conditions will be justified. Or
stated another way! it may be appropriate to do nothing with an
effective existing railing with a performance level significantly
below that which would be indicated by these guide specifications
because the cost to improve the railing would not be justified by
the improvement in safety achievable.