Browsing by Subject "Hydraulic performance"

Now showing 1 - 3 of 3

Effects of bridge deck submergence on backwater
(2007-05) Konieczki, Michael Vincent; Charbeneau, Randall J.
Currently no specific literature exists on the hydraulics of bridge rails. The objective of this research is to evaluate the hydraulic performance of bridge rail and deck systems and to provide recommendations on hydraulic analysis based on geometry for submerged and unsubmerged conditions to be used as a guideline in bridge design and construction. Physical modeling is used to establish rating curves for bridge-rail systems. Such curves provide a specific head discharge relationship that can then be non-dimensionalized using Froude scaling for greater applicability. An additional set of physical experiments will be conducted to analyze the effects of tailwater elevation and submergence (of the bridge superstructure) on backwater elevation. Tools will then be developed to provide prediction of hydraulic performance.
Effects of flush slab supports on the hydraulic performance of curb inlets and an analysis of design equations
(2016-05) Schalla, Frank Edward; Hodges, Ben R.; Barrett, Michael E
The new Texas Department of Transportation curb inlet uses 6 inch flush slab supports for the top slab of a curb inlet. HEC-22, which provides design equations used by TxDOT, states flush slab supports can reduce an on-grade inlet’s interception capacity by as much as 50%, yet does not provide any guidance on quantifying these effects. Full-scale physical modeling of the TxDOT curb inlet on-grade was performed to investigate the effects of flush slab supports on hydraulic performance. In addition, the modeled curb inlet is compared with HEC-22 and other curb inlet design equations. No measurable difference in interception capacity or ponded width was found between curb inlets with flush slab supports and without. For the 5 ft modeled curb inlet a combination of Guo and MacKenzie (2012) design equation and HEC-22 align best, yet neither align with every tested slope combination. HEC-22 design equations were found to over-predict the 15 ft modeled curb inlet by an average factor of 2.3:1. No other design equations were found to accurately predict hydraulic performance for the 15 ft modeled curb inlet.
Hydraulic performance of bridge rails based on rating curves and submergence effects
(2007-05) Klenzendorf, Joshua Brandon; Charbeneau, Randall J.
The Texas Department of Transportation (TxDOT) is required by the Federal Highway Administration (FHWA) to use crash tested bridge rails on all new bridge construction and for existing bridges scheduled for safety rehabilitation. In general, crash tested bridge rails have a greater height and less open space than bridge rails that have failed crash testing. In the case of safety rehabilitation of existing bridge railing systems that have failed crash testing, the change to successfully crash tested rails would likely result in a rail design with greater height and less open space. This design could result in poor hydraulic performance of the new bridge rails during flood events, which may increase the upstream water surface elevation. Such a change could impact the floodplain for the 100-year return period flood. In the event that the floodplain changes by more than one foot, the Federal Emergency Management Agency (FEMA) requires a floodplain map revision. This can be costly and result in the delay and complication of rehabilitation projects. The objective of this research is to evaluate the hydraulic performance of different bridge rail designs that have been crash tested and found acceptable for TxDOT use. Physical modeling experiments are conducted in order to determine rating curves for various rail systems. The rating curves describe the upstream water surface elevation as a function of the flow rate passing over the rail. A simple three parameter model is developed in order to describe the rating curves based on obtained experimental data. In addition, the effects of the submergence of bridge rails by an increase in downstream water surface elevation are also evaluated. Submergence can occur on a rail located on the upstream side of the bridge due to the backwater produced by the rail on the downstream side of the bridge. This will increase the upstream water surface elevation predicted by the rating curves for each rail. Two different models are used to approximate and characterize the effects of rail submergence.