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Re: Masonry wall with epoxy anchors[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "Seaint@Seaint. Org" <seaint(--nospam--at)seaint.org>
- Subject: Re: Masonry wall with epoxy anchors
- From: Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu>
- Date: Thu, 8 Sep 2005 13:47:11 -0400 (EDT)
Dave, See comments below: On Thu, 8 Sep 2005, Nuttall, Davin J. wrote: > List, > > > Due to contractor error, I had to externally reinforce a 12" CMU stack > bonded cavity wall after-the-fact. If I may ask, why the stacked bond. If the wall will be furred out, then it appears that appearance is not the driving factor, so running bond should have been the better choice. The exception could be that only one side will be furred and the exterior a face of the wall will be exposed. If such is that case, then I have to wonder what the type of load the wall must carry is, how was it deemed insufficient as constructed, and what are the full details of the repair. It sounds as if it could be flexure due to wind pressure and repair could be external steel plates as flexural reinforcement (all speculation...could be something else). If so, then reinforcing one side would not seem to solve the potential problem as the wind in such as situation could be either positive pressure (resulting in tension stresses on the inside face) or negative (resulting in tension stresses on the exterior face). Just curious. > > My detail included continuous steel plates with epoxy anchors drilled > into the center of existing solid grouted cores. The wall will be > furred out, so the repair will not be visible after the project is > finished. > > I now find out that the contractor ignored portions of the submitted > fix, and in some cases, located the anchors right in a mortar joint. > > Questions: > > 1. Because the wall is grouted solid, would you be concerned with edge > distance of the bolt relative to the edge of the individual block? Generally, I would say no. It will in general be the edge distance of the bolt to the edge of the masonry assembly not the unit. This would be largely true even if ungrouted. This is assuming you are looking at it from a global point of view. Where edge distance to a individual block could be an issue is for local effects that could further weakness in the "weak points" (i.e. say you use an expansion style anchor in a mortar joint...could cause the joint to crack/fail due to the expansive force, which in an ungrouted situation could cause the generally considered weakest point - the mortar joint - to be even weaker). > > 2. Are the blocks considered as individual units with respect to the > new bolts and their capacities, or is the entire cmu wall acting as 1 > monolithic unit? Generally considered acting as 1 monolithic unit. But again, it depends on what "thing" (i.e. failure mode, behaviour, etc) you are looking at. Masonry is a "non uniform" material, so some failure modes can be governed by the individual components more readily than the overall assembly. So, it will require knowledge of how masonry behaves and what the bolts are "doing" (i.e. how are the bolts loading the masonry) to really make such a determination. And I don't have enough information of the specific situation to make such an assessment in this situation. > > 3. How much of a strength reduction would you take because the bolt is > located in or right next to a mortar joint, and not the published > distance away from a free edge? Again, it depends on what the bolt is "doing" and the configuration of the bolts as well as the configuration of the wall as is and what kind of loads it must carry. More than likely if the bolts are engaging the grout in the cores, it will likely not matter if the bolt is in a mortar joint or not. > > The worst case scenario would be to remove and relocate the plate and > bolts to the specified location(s). As always, time is a major concern, > and they would like to move on with minimal rework. > > Thanks > > Dave Nuttall, P.E. > Green Bay, WI > HTH, Scott Adrian, MI ******* ****** ******* ******** ******* ******* ******* *** * Read list FAQ at: http://www.seaint.org/list_FAQ.asp * * This email was sent to you via Structural Engineers * Association of Southern California (SEAOSC) server. To * subscribe (no fee) or UnSubscribe, please go to: * * http://www.seaint.org/sealist1.asp * * Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you * send to the list is public domain and may be re-posted * without your permission. Make sure you visit our web * site at: http://www.seaint.org ******* ****** ****** ****** ******* ****** ****** ********
- Masonry wall with epoxy anchors
- From: Nuttall, Davin J.
- Masonry wall with epoxy anchors
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