We have some rebar that was not placed correctly due to confusion on the plans. This is a 42” combination railing that VDOT uses.
Under normal conditions the rail would be in the same plane as the concrete parapet bottom. In our case, to maintain the plane of the concrete along the bridge the traffic face of the barrier will be in front of the railing. I think this is probably a concern. So, first, can we leave the rail 2.5” back from the concrete traffic face?
I am anticipating that somehow we need to move the rail to the face of the concrete parapet bottom, so can we increase the spacer that is already on there?
If no special action is no good and increased spacer thickness is no good, have you got any other simple solutions?
After reviewing your attached detail, we believe that you will likely need to move the tube rail flush with the face of the parapet as originally intended. Due to the short height of the parapet and the presence of the sidewalk, the tube rail is likely integral to the redirection of errant vehicles. Thus, the implications of moving the tube face back from the face of the parapet is unknown.
In terms of retrofits, a spacer like the one you propose should be acceptable. As a slightly simple alternative, we might proposed adding a second HSS4x3x3/16 tube as the spacer as you are already using that tube in the system and it provides a similar 3” offset. Then you could us a smaller shim plate and achieve the same offset with less steel. If there is only a single bolt attaching the post to the tube rail and spacers, you may need to tack weld the tube spacer and plate toe each other and/or the rail tube to prevent rotation.
Let us know if you have further questions.