Anchorage to concrete

Abstract

Several types of anchor are available t o transfer loads into structural concrete. They all utilize the concrete tensile strength. Many reinforced concrete structures are designed under the assumption that the concrete is cracked. Research shows that fasteners will attract cracks or even induce cracking. Therefore, the behavior of different types of fasteners in uncracked and cracked reinforced concrete has been studied extensively. Fasteners used in zones with potential concrete cracking must be suitable for this application. Suitable are cast-in-situ headed studs, post-installed anchors like undercut anchors and specially designed torque-controlled expansion anchors and adhesive anchors with follow-up expansion. They show a reduction of the concrete failure load of about 25-35% compared with uncracked concrete when located in o r close t o cracks with a width of 0.3-0.4 mm (0.0 I 24.0 I 6 in). This crack width can be expected in typical concrete members designed with ordinary crack control provisions. Based on comprehensive studies described in this article fastenings in uncracked and cracked concrete can be designed with sufficient accuracy. Progress in Structural Engineering and Materiais I998 Vol I(4): 392-403The demand for more flexibility in the planning, design and strengthening of concrete structures has resulted in an increased use of mechanical and chemical anchoring systems for structural applications.Most reinforced concrete (RC) members are designed under the assumption that the concrete is cracked under service load. It is known that the presence of cracks can substantially reduce the concrete capacity of fasteners[i*~. Some fasteners are not suitable for use in cracked concrete. Therefore, the design of anchors needs to consider the influence of cracks on the behavior of fasteners.This article describes the fastening systems available on the market and gives background information on the behavior and design of fasteners loaded in tension and shear and installed in cracked and non-cracked concrete. The state-of-the-art of fastenings is also described in ACI 355121 and Comite Euro-International du Beton (CEB)WI and by Eligehausen et al[r*i. Mechanical fastenings CAST-IN-SITU PARTSCast-in-situ elements are fastened to the formwork and cast into the concrete. They are available in a big variety of versions. A common example is a plate with welded-on headed studs (Fig. la). J-bolts are also often employed (Fig. lb). They are typically manufactured from smooth bars. The bolts are bent into a J-shape at one end and are threaded with coarse rolled threads. Channel bars (Fig. lc) comprise cold drawn or hot rolled U-shaped steel profiles with special anchoring elements. After removal of the formwork the attachment is fixed to the channel with special hammer-head or hook-head bolts. The anchoring elements such as T-shaped anchors or headed bolts are welded or forged to the back of the anchor channel. With all cast-in-place systems a tension load is transferred into the concrete by mechanical interlock. Abbre...

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“…The research of capacity on pull-out carry out among other [6][7][8][9][10][11][12][13]. This is done in two stages.…”

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