Masonry Magazine August 1987 Page. 25
Screen can be placed in the bed joint across cells that are to be partially grouted to restrict the grout flow beyond a certain point. Figure 16 shows typical embedment details for conventional anchors embedded in reinforced cells. In this detail, the anchor may be tied with wire to the reinforcing to secure the anchor during the grouting process. Again, the anchor should be solidly surrounded by grout to a minimum distance of twice the actual anchor embedment depth, both vertically and horizontally.
Two typical embedment details for conventionally embedded anchor bolts installed in composite brick and concrete block construction are shown in Fig. 17. As shown, anchor bolts may be placed in the collar joint between the brick and block wythes or placed into cells in the concrete block wythe and grouted into place. In details similar to Fig. 17(a), the anchor bolt type and diameter may be controlled by the width of the collar joint. Collar joints should be a minimum of 1 in. (25 mm) wide when fine grout is used, or a minimum of 2 in. (50 mm) wide when coarse grout is used (see Technical Notes 7A Revised). When the collar joint dimension is in the 1 in. (25 mm) range, it may become difficult to position anchor bolts in the collar joint and maintain the recommended clear distance between the masonry and the anchor (Fig. 17). The practice of using soaps to accommodate anchors larger than the collar joint is not recommended because the reduction in the brick masonry thickness around the anchor could lead to strength reductions. If the anchor dimensions required are larger than the collar joint, a detail similar to that shown in Fig. 17(b) should be considered.
Through bolts are typically installed after construction and grouting by drilling through the completed masonry work. When through bolts are to be installed after construction in reinforced brick masonry, care should be taken during installation to avoid cutting or damaging reinforcement while drilling the through bolt holes. Reinforcing bar locations can be identified by specially tooled joints or other marks made during construction.
Proprietary Anchors
Proprietary expansion and adhesive anchors typically require special installation procedures and equipment. The manufacturer should be contacted to determine the appropriate anchor for a particular application, the correct installation procedure and if any special installation equipment is required. Improper application and installation of proprietary anchors may lead to less than satisfactory structural performance.
Typical proprietary anchor details are shown in Fig. 18. It is suggested that proprietary anchors be embedded in head joints when facing or building brick are used. This reduces the possibility of placing anchors in brick cores that occur within the thickness of the brick and adjacent to the bed joint surfaces. Anchors set in grouted hollow brick should be placed in holes drilled in the bed joints so that they intersect grouted cells, or should be placed in holes drilled through the faces of the units into the grouted cells. As with conventional anchors, proprietary anchors should be solidly surrounded vertically and horizontally by grout for a minimum distance of twice their embedment depth.
ANCHOR BOLT DESIGN
Anchor bolts are used as a means of tying structural elements together in construction and therefore, provide continuity in the overall structure. In virtually all applications, anchor bolts are required to resist a combination of tension and shear loads acting simultaneously due to combinations of imposed dead loads, live loads, wind loads, seismic loads, thermal loads and impact loads. For this reason, and also to insure safety, anchor bolt details should receive the same design considerations as would any other structural connection. However, due to a lack of available research and design guides, anchor bolt designs are based largely on past experience with very little engineering backup. This situation may lead to conservative, uneconomical designs at one extreme, or nonconservative designs at the other.
Recently, however, research investigating the strength of conventional and proprietary anchors in masonry has been completed. Reports have been issued that evaluate anchor performance and suggest equations to predict ultimate anchor strengths. By combining the research findings with design practices currently used in concrete design, equations for allowable tension, shear and combined tension/shear loads for plate anchors, headed bolts and bent bar anchors are under consideration for adoption in the proposed "Building Code Requirements for Masonry Structures" (ACI/ASCE 530). These equations are outlined below.