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We would like to get your thoughts on conduit bundles placed within reinforced concrete barrier as shown below. I found a similar question that was asked back in 2010 but it did not get into great detail https://mwrsf.unl.edu/q&a/view.php?id=342. 

Below I have shown a bundle of 9- 2 inch conduit bundles with different configurations. 

• Do you have an idea for a maximum bundle or "void area '' that could be used without affecting structural capacity for vehicle  impacts?


• Is there any other concernce with MASH regarding electical conduits?

Our MwRSF research team briefly reviewed and discussed your situation of placing nine 2-in. diameter conduits within the reinforced-concrete, single-slope median barrier system.

From that discussion and considering the reinforcement shown in your barrier, it is suggested that the conduit grouping be located in the lower region of the barrier and positioned at the centerline. Using this general guidance, it is also desired to utilize a solid section of concrete at the base of the barrier for a height/thickness of approximately 5 in. to provide consistent lateral shear transfer across the base.

Further, it would be beneficial to maintain a minimum sidewall thickness of approximately 6 in. of each side of cavity to reduce concerns for sidewall fracture in front of any internal cavity. Using five rows of conduits, a maximum cavity height of 10 in. would be found. Using three columns of conduits, a maximum cavity width of 6 in. would be found. Thus, a maximum cavity area would be approximately 60 in.² within the 672 in.² cross section.

When using the 5-in. lower barrier thickness and a 10-in. cavity height, the top of the cavity would be limited to approximately 15 in., thus maintaining the 6-in. minimum sidewall thickness.

A sample schematic of the barrier with the cavity space for conduits and the dimensions noted above is provided in the attached PDF file. Note that these suggestions are based on our engineering judgement and known behaviors for prior crash testing of concrete median barriers under TL-3/TL-4 impact conditions. Of course, the only true manner to evaluate the effects that these barrier modifications have on overall barrier crashworthiness is through full-scale vehicle crash testing programs.

If you have any questions regarding the suggestions and thoughts noted herein, please feel free to contact me via email or to set up a conference call to further discuss this matter.