Welded Anchors for Embedded Plates

Steel embedded plates are often used to transfer loads from structural members to concrete structures or foundations. Such plates are often cast-in-place for constructability and to provide a smooth surface for attachment. These plates are attached to the concrete with welded anchors, which typically consist of headed studs, headed anchors, weldable rebar, or shear lugs they can be designed to resist applied tension, shear, and moment. Welding should be compatible with the anchor type. 

Embedded plates may be designed using one type of anchor or a combination of different types. A combination may be desirable when large one-directional moments are encountered. The embedded plate thickness should be designed to carry the tension, compression, shear, and moment to the anchors in a manner similar to that 

The guidelines for designing welded anchors for embedded plates presented herein are based on ACI 318 Appendix D, and the user should refer to that document for details not included herein. Shear lugs on embedded plates are similar to those discussed in 3.7 except without grout, and will not be discussed further. 

AWS Dl.l/Dl.lM requires studs to be Type B made from cold drawn bar stock conforming to ASTM A108. Since headed studs are relatively short, it is not practical to consider reinforcing steel in design as might be the case with longer anchors. 

Headed anchor rods may be used in heu of headed studs to increase the embedment and assure ductile design, or if studs are not available. Design is similar to that for headed studs. The user must ensure that the anchor rod is made of a weldable material. 

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Examples of Design of Welded Anchors for Embedded Plates... 

Both rebar and headed anchor rods welded to an embedded plate can be cumbersome to handle since the lengths can be long. If this is undesirable for shipping or coating, a threaded coupler can be welded to the embedded plate and the rebar or anchor rods threaded to match. In this case the coupler weld would have to be sufficient to transfer the tension and shear loads. 

Legs are anchored to the foundations by base plates, which are held in place by anchor bolts embedded in the concrete. For large vessels in high seismic areas, a shear bar may be welded to the underside of the base plate which, in turn, fits into a corresponding recessed groove in the concrete. 

Equation (D-I9) is for cast-in headed stud anchors. It is based on the fixity of the anchor to the embedment and is appropriate for use in designing anchors welded to embedded plates. 

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