Details:

Creators:
Zhang, Guoping
Corporate Creators:
Louisiana Transportation Research Center
Subject/TRT Terms:
[+]
Bridge Foundations Bridges--Design And Construction Bridges--Foundations And Piers Cohesive Soils Design Methods Erosion Hydraulics Hydrology Scour Scour At Bridges Shear Strength Of Soils Shear Stress
Publication/ Report Number:
SIO No. 30000145 ; LTRC Project No. 08-3ST
SIO No. 30000145 ; LTRC Project No. 08-3ST Less -
Resource Type:
Tech Report
Geographical Coverage:
Louisiana
Corporate Publisher:
Louisiana Transportation Research Center
Abstract:
Scour of bridge foundations is the most common cause of bridge failures. The Federal Highway Administration

(FHWA) has developed a design method, HEC-18, for the state Departments of Transportation (DOTs) to evaluate

the scour potential of existing bridges and predict the scour depths for new bridges. The scour models in the HEC-18

were based on a number of empirical equations that were developed primarily from laboratory fl ume studies with

limited fi eld data verifi cation. Because of the complex nature of scour process, these scour-prediction equations

recommended in HEC-18 may tend to provide conservative scour depth estimates to ensure that an adequate

factor of safety is considered for bridge scour design. Underestimation of scour depths may result in costly bridge

repairs or even catastrophic bridge failures, while overestimation may cause costly, unnecessarily deep foundations.

The scour potential evaluation for existing bridges is also important. Overestimation of scour depths causes more

bridges to be misclassifi ed as “scour critical,” thus resulting in unnecessary installation of scour countermeasures

or bridge replacements. Currently, the Louisiana Department of Transportation and Development (DOTD) uses

the HEC-18 method for bridge scour design. Costs associated with the current design methods that usually lead to

conservative estimation of scour depths can be very high. On the other hand, DOTD has developed and maintained

a large database for a large number of bridge structures that are prone to scour. Those bridges were monitored and

hydrologic and hydraulic data collected. In addition, diff erent bed materials scour at diff erent rates and, because of

this fact, HEC-18 does not always accurately predict the scour depth at a certain time. A more reliable scour prediction

method is needed, especially for the clay and silty clay soils common in Louisiana,

with distinct local climatic characteristics (e.g., heavy downpours, severe storms, and

hurricanes).


Format:
PDF
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:58d6a966a63e47e5e157742ee6398a45e0f0f6ba79d2fe4313a5308f681a0759
Download URL:
https://rosap.ntl.bts.gov/view/dot/25780/dot_25780_DS1.pdf
File Type:

Supporting Files

• No Additional Files

More +