Integral Abutment Bridges
Table 1 shows responses regarding status of use of integral abutment bridges and problems associated with integral abutment bridges.
The 2009 survey on integral abutment bridges also addresses the issue of costs associated with the use of integral abutment bridges. Tables 2 and 3 show the state responses on the issue of construction and maintenance costs of integral abutment bridges compared to conventional bridges.
Summary of Responses
The responses to the survey indicate that nine states do not use integral abutment bridges. Out of the nine states that do not use integral abutment bridges, three states (Alabama, Delaware and Louisiana) never used integral abutments, three states (Alaska, Arizona and Mississippi) discontinued their use due to serious problems, and three states (Florida, Texas and Washington) discontinued their use either because they realized no performance advantage over their conventional practice (Florida and Texas) or they concluded that semi-integral abutments offer more advantages compared to integral abutments (Washington). The status of use of integral abutment bridges is illustrated in Figure 2.
The responses also indicate that 25 states have no problems with the use of integral abutment bridges. In addition, 12 states (California, Colorado, Maine, Michigan, Missouri, Nebraska, New Mexico, New York, North Carolina, Oklahoma, Utah and West Virginia) report either minor or moderate problems with the use of integral abutment bridges. Four states (Indiana, Kansas, South Dakota and Virginia) had moderate problems with integral abutment bridges in the past; they found a solution to their problems and do not report any more problems. However, three states (Alaska, Arizona and Mississippi) had serious problems with integral abutment bridges; as a result, each state discontinued their use. The status of problems with integral abutment bridges is illustrated in Figure 3.
The responses to the issue of construction costs of integral abutment bridges compared to conventional bridges indicate a lower construction cost in twenty-seven states, higher construction cost in five states (Arkansas, Georgia, Maryland, Nebraska and Utah), and same construction cost in three states (Indiana, Kansas and New Hampshire). The status of construction costs of integral abutment bridges and conventional bridges is illustrated in Figure 4.
The responses with regard to the issue of maintenance costs of integral abutment bridges compared to conventional bridge indicate a lower maintenance cost in thirty-two states, and same maintenance cost in three states (Georgia, Hawaii and Nebraska). Not surprisingly, no state reports a higher maintenance cost with the use of integral abutment bridges. The status of maintenance costs of integral abutment bridges and conventional bridges is illustrated in Figure 5.
Forty-one states use integral abutment bridges. The number of integral abutment bridges, both statewide and nationwide, has increased considerably in the last few decades. Eight states have more than 1,000 integral abutment bridges; among them, Missouri with more than 4,000 and Tennessee with more than 2,000 integral abutment bridges. The responses received from the state departments of transportation confirm the fact that use of integral abutment bridges almost always results in lower bridge maintenance costs compared to conventional bridges. The responses also confirm that in the vast majority of states, the construction cost of building integral abutment bridges is lower compared to conventional bridges.
In addition, most states report no problems with integral
abutment bridges; a limited number of states report minor to moderate problems with the use of integral abutment bridges. A number of states that previously had problems with integral abutment bridges were able to come up with solutions to these problems. As a result, they do not report any more problems with the use of integral abutment bridges.
However, it is very important to recognize that many problems are avoided because integral abutment bridges are built within the limitations imposed by the design parameters outlined in each state’s Bridge Design Manual. These design limitations prohibit the use of integral abutments for very long bridges and in situations that involve complex structural and soil conditions. In addition, there are limitations on skew, curvature and type of piles to name a few.
Apparently, more research on integral abutments is needed in order to advance the use of integral abutment bridges. More research that predicts the behavior of integral bridges based on theory, in addition to empirical evidence will lead to the introduction of national guidelines for integral abutment bridges, which will provide legitimacy to this cost-effective method of bridge construction. The current absence of such a document acts as a deterrent to the use and further advancement of integral abutment bridge construction.
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