Announcement

Collapse
No announcement yet.

Lag Bolts & Epoxy For Concrete.

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Lag Bolts & Epoxy For Concrete.

    Got to ask this question........... A friend of mine is putting up a radio tower and asked for some input. He has the tower he got used but not the base that sets in the concrete. He doesn't want to spend $350 for the properly designed base so some one (clown)
    told him he could pour the base then drill it out and use this super strength epoxy and some special lag bolts and lag the tower base to the concrete. I told him he's out of his mind to even think of anchoring such a structure like that.
    This isn't one of those little whimpy TV antenna towers this is 72' free standing crank up tower. The three sided base is about 24" or so. My guess is when the wind blows those lags are going to pull straight out of the concrete, were not talking shear force here this is tension or straight pull. I washed my hands of the deal, I'm not getting involved in this accident.

    JL...................

  • #2
    It didn't work too well in Boston a few years ago.

    https://en.wikipedia.org/wiki/Big_Dig_ceiling_collapse

    http://www.nytimes.com/2006/07/12/us/12tunnel.html
    https://www.youtube.com/channel/UCIF...7S66kX1s8rd0qA

    Comment


    • #3
      Originally posted by JoeLee View Post
      Got to ask this question........... A friend of mine is putting up a radio tower and asked for some input. He has the tower he got used but not the base that sets in the concrete. He doesn't want to spend $350 for the properly designed base so some one (clown)
      told him he could pour the base then drill it out and use this super strength epoxy and some special lag bolts and lag the tower base to the concrete. I told him he's out of his mind to even think of anchoring such a structure like that.
      This isn't one of those little whimpy TV antenna towers this is 72' free standing crank up tower. The three sided base is about 24" or so. My guess is when the wind blows those lags are going to pull straight out of the concrete, were not talking shear force here this is tension or straight pull. I washed my hands of the deal, I'm not getting involved in this accident.

      JL...................
      Properly engineered, there is nothing wrong with using epoxy and threaded rod or wedge anchors. It's done all the time. In fact, I recently installed a piece of equipment in a seaport that is designed to withstand 140 mph winds. The only thing holding it down are threaded rods and epoxy.

      Check out the image below. The tower grain dryer next to the bin is on the order of 70' tall and they are normally held down with a bunch of threaded rods and epoxy.
      http://www.brockmfg.com/uploads/phot..._0710_4257.jpg

      This is the epoxy we used for our seaport application: https://www.mcmaster.com/#7505a3/=17vshf7
      The anchors were 1" threaded rod embedded 10" in reinforced concrete, giving us an ultimate pull out strength of 47,000 lbs each.

      Comment


      • #4
        Stick with a vendor that publishes certified test results for his anchors.
        It is a free standing tower so the foundation itself needs to be designed to resist overturning from wind loads. Once the adequacy of the foundation is assured, Size the anchors for the required pullout strength.
        Design of the foundation and the anchors is not a job for amateurs. Get a professional to do it.

        Comment


        • #5
          Originally posted by JoeLee View Post
          he could pour the base then drill it out and use this super strength epoxy and some special lag bolts and lag the tower base to the concrete.
          Am I missing something here. Why would you pour then drill ... when you can set anchors in the cement
          while pouring ?

          Heck .. set the base of the tower in the damn pour .. lol
          John Titor, when are you.

          Comment


          • #6
            Originally posted by Mike Amick View Post
            Am I missing something here. Why would you pour then drill ... when you can set anchors in the cement
            while pouring ?

            Heck .. set the base of the tower in the damn pour .. lol
            This is what I told him, buy the base and set it in the concrete............
            He wants the cheap way out, which is going to be a disaster.

            JL.................

            Comment


            • #7
              It's one of these kind of deals here, small foot print base.



              This is what the mfg. sells to set in the concrete.



              No lags set in epoxy are going to be any where as strong as this design.

              JL..............

              Comment


              • #8
                Originally posted by Fasttrack View Post
                Properly engineered, there is nothing wrong with using epoxy and threaded rod or wedge anchors. It's done all the time. In fact, I recently installed a piece of equipment in a seaport that is designed to withstand 140 mph winds. The only thing holding it down are threaded rods and epoxy.

                Check out the image below. The tower grain dryer next to the bin is on the order of 70' tall and they are normally held down with a bunch of threaded rods and epoxy.
                http://www.brockmfg.com/uploads/phot..._0710_4257.jpg

                This is the epoxy we used for our seaport application: https://www.mcmaster.com/#7505a3/=17vshf7
                The anchors were 1" threaded rod embedded 10" in reinforced concrete, giving us an ultimate pull out strength of 47,000 lbs each.
                There is a huge difference in a grain silo that has a 40' ft. dia. foot print with an angle iron base and several hundred lag bolts spaced out every 8" to 10"
                Were talking a small foot print tower with a T base.

                JL.................

                Comment


                • #9
                  You do not say if the slab already exists. If not then the anchors could be built in (set in) during the pour.

                  The doco on ChemSet type anchors does seem impressive ... but I (like you) feel uncomfortable with glue holding big pulls when not necessary.

                  The site below may assist some in giving lead to the base required. Many of the poles (even wooden ones) are of a height similar to the proposed tower.

                  click here for link to some power pole design doco

                  I did not find an exact link to the bases for the poles as such ... but it is a start.

                  Comment


                  • #10
                    No, the concrete is not poured yet. I told him by the base from the company and be safe and do a right.

                    JL........

                    Comment


                    • #11
                      I have done a couple of successful installations like this - on the same tower, taking it along with me when I moved. I got the tower used, free and had to design and fabricate my own base structure. First installation served 20 years. Am 11 years into the second installation.

                      Originally posted by JoeLee View Post
                      It's one of these kind of deals here, small foot print base.



                      This is what the mfg. sells to set in the concrete.



                      No lags set in epoxy are going to be any where as strong as this design.

                      JL..............
                      Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                      ~Practitioner of the Electromechanical Arts~

                      Comment


                      • #12
                        My friend got his for about $500, pretty cheap considering what some of these go for. He doesn't want to spend the $350 for the base so he's looking for the "inexpensive" way out, and we all know what happens when we go this rout.
                        He's also cutting corners on the concrete base. If the epoxy lags don't fail the tower is sure to topple over or end up looking like the leaning tower of Pisa.

                        JL...........

                        Comment


                        • #13
                          If memory serves when setting a pole 1/5 of the height should be in the ground.

                          Lag bolts and epoxied anchors depend on the tension strength of the concrete base. Concrete has high compression strength but low tensile strength.
                          The anchors probably will not pull out but will fail by taking a nice chunk of the concrete with it.

                          Tell him the story about buying a lathe cheap and having to spend as much to buy tooling for it.

                          For less than $100 he can make a nice anchor that can be embedded in the base concrete and easily hold the tower.

                          Remind him to place a good ground plane in the hole also when he does this.
                          Guaranteed not to rust, bust, collect dust, bend, chip, crack or peel

                          Comment


                          • #14
                            FWIW: I have a TV tower, 30' tall, anchored to a slab alongside my shop. The base of the tower is welded to a plate, 1/2" X 16" square, with the tower base being a triangle 13" on a side. I used 4, 3/8" expansion anchors that are 2 or 3" long. The tower IS shielded from the West wind, but is NOT connected to the building. Been there for 30+ years.

                            Comment


                            • #15
                              As long as the tower can't get blown over and drop on anyone, I'd say let him mount it in whatever stupid way he wants to. This is an instance where going cheap initially will quite likely end up being most expensive in the end and I'm of the opinion that if being stupid isn't painful it should at least be expensive.
                              Location: Saskatoon, Saskatchewan, Canada

                              Comment

                              Working...
                              X