Evaluation and Repair Procedures for Precast/Prestressed Concrete Girders with Longitudinal Cracking in the Web (2010) / Chapter Skim
Currently Skimming:
Pages 4-12
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 4... ...
Thus, it appears to be logical to have less restrictive cracking limitations on web end cracking than on conventionally reinforced concrete sections subject to flexure. 1.2.1 Evolution of Permissible Crack Widths The evolution of, and recommendations for, permissible crack widths developed between 1935 and 1970 can be traced from several references (1–6)
|
From page 5... ...
Bureau of Public Roads (Maximum crack width at steel level under service load) , 1966, as contained in References 6 and 7 0.006 0.006 0.008 0.010 - Seawater and seawater spray, alternate wetting and drying - Deicing chemicals, humidity - Salt, air water and soil - Air or protective membrane Flexural cracking in beams.
|
From page 6... ...
The report discusses many possible sources of cracking, such as shrinkage cracking, flexural cracking, tension cracking, and end zone cracking on prestressed concrete members. The report gives the following guidelines, shown in Table 1.2, for tolerable crack widths at the tensile face of reinforced concrete structures for typical conditions.
|
From page 7... ...
However, the report does not give any guidelines regarding the crack width or when to reject the product. The report states that if the crack plane coincides with a strand, it may affect the bond between the strand and concrete and increase transfer and development length.
|
From page 8... ...
• Friction with the bottom form of the prestressing bed (11, 14) : In cases where the bottom form of the prestressing bed is not properly oiled or has indentions, horizontal cracks are developed in the bottom flange.
|
From page 9... ...
• Use of large strands: With the increasing use of concrete with high strength, a number of state highway agencies have begun using 0.6-in. diameter strands at the standard 2-in.
|
From page 10... ...
It also states that 75 psi to 200 psi injection pressure is commonly used for crack widths in the range of 0.006 to 0.007 in. 10 Figure 1.3.
|
From page 11... ...
1.5 Applicability of Results to Highway Practice The project was structured to provide a manual of procedures for the acceptance, repair, or rejection of precast/ prestressed concrete girders with longitudinal web cracking. The manual, which is provided in Chapter 3 of this report, can 11
|
From page 12... ...
• Appendix F provides information on the field inspection of bridges in Nebraska and Virginia. • Appendix G provides design examples of end zone reinforcement using the LRFD Specifications and the proposed details.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.