Click for next page ( 25


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



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 24
24 CHAPTER 4 CONCLUSIONS AND SUGGESTED RESEARCH 4.1 CONCLUSIONS Extending the column spiral reinforcement into the con- nection region is required to ensure adequate confinement of It is feasible to integrally connect reinforced concrete the connection region. The required spiral reinforcement in columns to box-beam pier caps by extending the column lon- the connection region may be taken as the greater of the min- gitudinal reinforcement through holes in the pier cap flange imum spiral reinforcement required by the design specifica- and filling the pier cap compartment directly above the col- tions and one-half the required column spiral reinforcement umn with concrete. The resulting connection is sufficient to next to the integral connection region. develop the plastic hinging of the column, given that anchor- The live load distribution factors in the current design age adequate to fully develop the column longitudinal rein- specifications, which were developed for use with bridges forcement inside the pier cap is provided. The first test spec- supported on conventional bearings, may be used for bridges imen, which had a deeper pier cap and longer anchorage with integral connections. length of the column longitudinal reinforcement, reached Using grillage models to analyze bridges with integral a ductility of = 6.0 before failure. The second test connections is expected to yield high accuracy. specimen, with a shallower pier cap, reached a ductility of = 4.0 before failure. The failure at this lower ductility 4.2 SUGGESTED RESEARCH essentially resulted from the loss of bond between the col- umn bars and the concrete in the integral connection region. Parametric studies to further verify the simplified analysis Integral pier connections are most likely to be used for method for typical structures as included in the proposed bridges with high skew angles and are supported on single- design specifications is needed. Some of the parameters that column piers. The use of the integral pier connections results need to be included are the skew angle, variation in adjacent in lower elevation of the bridge deck and the approaches with- span length, number of continuous spans, and number of the out reducing the bridge underclearance. The cost of bridges girders in the cross section. with integral connections is expected to exceed conventional The shear connectors on the outside of the bottom flange of bridges; however, because of the lower approach elevation, the the pier cap may complicate construction. Testing to prove that combined cost of the bridge and the approaches is expected to the column longitudinal reinforcement is sufficient to transfer be lower than that of a conventional bridge. the column shear force to the connection region is needed.