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I write structure design criteria for our design-build projects and I have a couple general questions I was hoping to get your MASH opinion on.

We have an upcoming project with a need for mounting noise walls on structure in a couple different applications:

1. An existing bridge over a tidal creek


2. New bridges where we would otherwise use our SCDOT TL-4 MASH barrier


3. A new curving overpass with primarily truck traffic where we are considering using a MASH TL-5 bridge barrier.


4. Retaining walls on the bridge approaches

For the existing bridge, I am seeking guidance on what options exist for retrofitting an existing jersey barrier with a noise barrier?  This is a pre-LRFD flat slab bridge with a jersey shape barrier (attached are some existing plan sheets).  I doubt that any noise wall attachment could be designed for the TL-4 collision forces prescribed in AASHTO LRFD BDS 8^th edition Chapter 15.  I assume we would need to remove and replace the barrier (and portion of the flat slab) with a MASH-compliant railing that either has a concrete noise wall extension (such as the attached FDOT standard) or an attachment design that complies with LRFD Chapter 15 collision forces? 

For a new bridge with a TL-4 railing, do you know if the attached FDOT 8’ tall concrete standard drawing is considered MASH TL-4 compliant?  My understanding is that it was crash-tested for NCHRP 350 TL-4 vehicles (https://tti.tamu.edu/publications/catalog/record/?id=6006 ) but I am not aware whether it has been tested for MASH TL-4 requirements.  Do you know of any other MASH TL-4 crash tested barrier-mounted noise walls that are all reinforced concrete?

For TL-5 bridge and retaining-wall-moment-slab options…so far I have found one state-DOT-adopted, crash-tested MASH TL-5 barrier with noise wall mounted behind it, and that is the attached Illinois Tollway Authority standard.  Can you confirm that their proposed shape and minimum offset to the noise wall would perform well under MASH TL-5 conditions (for curving ramp geometry with heavy truck traffic over an interstate)?

Thank you for any advice/opinions you can offer and if you need any additional information, please let me know.

Nice to meet you. Dr Ron Faller with our group has a great deal of expertise in the area of crashworthy soundwalls.

He has provided some comments on your request below in red.

Thanks

We have an upcoming project with a need for mounting noise walls on structure in a couple different applications:

1. An existing bridge over a tidal creek
2. New bridges where we would otherwise use our SCDOT TL-4 MASH barrier
3. A new curving overpass with primarily truck traffic where we are considering using a MASH TL-5 bridge barrier.
4. Retaining walls on the bridge approaches

For the existing bridge, I am seeking guidance on what options exist for retrofitting an existing jersey barrier with a noise barrier?  This is a pre-LRFD flat slab bridge with a jersey shape barrier (attached are some existing plan sheets).  I doubt that any noise wall attachment could be designed for the TL-4 collision forces prescribed in AASHTO LRFD BDS 8^th edition Chapter 15.  I assume we would need to remove and replace the barrier (and portion of the flat slab) with a MASH-compliant railing that either has a concrete noise wall extension (such as the attached FDOT standard) or an attachment design that complies with LRFD Chapter 15 collision forces?

**There are two general considerations.

First a noise wall could have been be developed and crash tested on a parapet at a given test level under a specific safety performance guideline (i.e., NCHRP 350, MASH, etc.). It is up to the DOTs to determine if and when they utilize 350 or MASH hardware.

For non-proprietary crashworthy systems, the end users would need to utilize information in the crash testing report as well as from the developers to determine whether the system could be adapted to other barrier shapes, sizes, and strengths. For proprietary crashworthy systems, the system fabricators and suppliers would be able to provide some implementation guidance on its attachment to barriers and bridge rails.

Alternatively, a noise barrier could have been developed according to the Chapter 15 structure-mounted criteria by applying the loading conditions to both the posts and the noise wall panels. Depending on the spacing of the support posts, the loading may need to be applied to the panels located between the posts. I am uncertain as to whether the panels can take the loading when the posts are farther apart. The hardware supplier would need to demonstrate through calculation or physical component/system testing if the panels can withstand the Chapter 15 loading at all locations along the system, replicating a moving load. The multiple locations are denoted in Chapter 15, including in the commentary.

For the NJ bridge rail on Tidal Creek, one may want to know whether the concrete barrier system is deemed MASH equivalent. NCHRP Project No. 20-07 (Task No. 395) reviewed some barrier systems for equivalency. A follow-on NCHRP project was continued. The processes noted therein could be used to first determine MASH equivalency for the barrier. MwRSF conducted a similar Midwest Pooled Fund Program study years ago, which was published in an internal draft report.

Although unknown now, it may seem possible that the NJ barrier system could be used to anchor a noise wall. However, this decision may be based on the barrier design and capacity as well as the barrier-to-deck and cantilevered deck configurations. Note that there are a range of noise wall weights, which would be placed on the barrier and deck systems.

For a new bridge with a TL-4 railing, do you know if the attached FDOT 8’ tall concrete standard drawing is considered MASH TL-4 compliant?  My understanding is that it was crash-tested for NCHRP 350 TL-4 vehicles (https://tti.tamu.edu/publications/catalog/record/?id=6006 ) but I am not aware whether it has been tested for MASH TL-4 requirements.  Do you know of any other MASH TL-4 crash tested barrier-mounted noise walls that are all reinforced concrete?

**At this time, I am unaware as to whether the Texas and Florida RC noise wall on a concrete barrier is MASH rated under TL-4. However and by its shear size and configuration, I would expect it to meet MASH TL-4, even if damage occurred to the various interfaces between noise barrier and vehicle barrier as well as vehicle barrier and deck. There is considerable inertia in this combined system.

I have not seen other RC noise wall systems other than the two-part configuration utilized by the Illinois Tollway Authority. Most other systems are proprietary.

For TL-5 bridge and retaining-wall-moment-slab options…so far I have found one state-DOT-adopted, crash-tested MASH TL-5 barrier with noise wall mounted behind it, and that is the attached Illinois Tollway Authority standard.  Can you confirm that their proposed shape and minimum offset to the noise wall would perform well under MASH TL-5 conditions (for curving ramp geometry with heavy truck traffic over an interstate)?

*At this time, I am unaware of a TL-5 impact study into curved barriers of varying heights. At this time, there is some data available through NCHRP Project No. 22-34 on ZOI for straight barriers. Further, there exists some ZOI data corresponding to MATC R&D study on TL-6 straight barriers of varying heights, which utilized tank-body trailers. For the Illinois Tollway‘s 64-in. tall straight barrier, I would expect the TL-5 ZOI to be limited with van-body, tractor trailer vehicles. Again, we do not have crash or simulation data to use to adjust ZOI for curved barriers.