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Lightweight (LW) aggregates (LWAs) improve fire resistance, moisture resistance, and durability in addition to reducing the selfweight of concrete. However, the ACI 318 code includes a modification factor (lambda) to account for reduced tensile capacity in LW concrete. LWAs are not currently permitted for use in masonry grout due to lack of test data to establish appropriate modification factors for the TMS 402/602 code. This study is a pilot study that aims to experimentally determine how the tensile breakout and shear breakout capacity of cast-in-place bent-bar anchors in masonry assemblies with LW grout compare with the predictions of TMS 402-16 for anchors in normal weight (NW) grout, and with results in the literature for assemblies using NW grout to see if additional testing would be needed to determine a lambda factor for shear and tensile behavior of LW grout. The results indicate that a reduction factor for bent-bar anchor bolts in masonry constructed with LW grout may not be needed, but additional testing should be conducted with smaller bar diameters to demonstrate the consistency of these results across bar sizes.

Embedded plates are used to support external attachments such as heavy piping, brackets, sprinkler systems, or other equipment in concrete structures. The plates are typically welded with deformed reinforcing bars or deformed wires, which are embedded in reinforced concrete walls. The ACI Codes (ACI 318-19 and ACI 349-13) provide design equations to calculate the pullout strength of anchors in concrete under tension loading. However, these empirical equations are based on experiments conducted on headed studs, hooked bars, headed bolts, and adhesive anchors. With the lack of experimental data and resulting Code provisions on straight deformed reinforcing bars or deformed wires used as anchors, it is believed that anchoring bars with the embedment length as per the Code-prescribed development length will provide sufficient strength to transfer tensile forces to the concrete, ignoring other failure modes such as concrete breakout and pullout. The applicability of the concrete-governed adhesive bond model of ACI 318-19 for bonded anchors is evaluated to estimate the strength and failure modes of these connections. The current ACI adhesive bond model does not capture the correct failure mode and the influence of anchor spacing and bond strength on the capacity. The issue is addressed by incorporating the correction factor (ψg,N). This paper presents eight large-scale group-anchor test results to evaluate their concrete breakout strength and the applicability of the ACI 318-19 adhesive anchor/bond model to estimate connection capacities and failure modes. The mean average back-calculated effective k value is 33.3 for deformed reinforcing bar anchors (DRAs) and 36.5 for deformed wire anchors (DWAs). Single-anchor tests were also performed to evaluate the bond behavior per the ACI 318-19 uniform bond model. The experimental study confirms that the axial tension capacity of embedded plates anchored to concrete using deformed reinforcing bars or deformed wires can be limited by concrete breakout strength. The ACI bond model with the correction factor appropriately estimates the failure mode and strength of such connections.

In this research, bond between steel and alkali-silica reaction (ASR) concrete was investigated by means of pullout specimens. Main variables included the presence and type of reinforcement and level of concrete deterioration due to ASR. Results were compared to identical specimens made from control concrete. To promote concrete expansion, both reactive and control specimens were subjected to periods of prolonged exposure to a high-humidity and high-temperature environment (that is, 50 ± 2°C and over 97% relative humidity) inside a custom-built curing facility. Testing was conducted at three different concrete ages to capture any changes in bond behavior as ASR developed. While the effect of ASR on bond strength of confined concrete was negligible, up to 20% reduction in peak bond stresses was observed in the unconfined specimens. In addition, results from a pilot series of tensile testing of headed bolts cast in ASR concrete are also presented.

A laboratory research program was undertaken to compare the failure mechanisms and strengths of concrete foundation slabs subjected to punching shear and concrete breakout loadings. Four nominally identical reinforced concrete slabs were constructed and tested in a laboratory. One of the slabs was loaded in compression through a bearing surface to produce punching shear failure. The other three slabs were loaded in tension through eight anchor bolts arranged around a square perimeter to produce a similarly sized breakout failure. Variations in bearing area and local reinforcement detailing were introduced in the breakout tests to explore their effect on strength. One additional specimen was cast with a single anchor bolt to gather data on basic breakout strength. The test results indicate that punching shear and anchor breakout developed similar failure modes. Punching shear resulted in the largest strength with the largest failure surface. Ultimate load capacities normalized by the square root of the concrete compressive strength and by an effective failure area showed that the nominal failure stresses were nearly equal for the different test cases. The addition of slab deformed reinforcement in the vicinity of the anchor bearing head and oriented perpendicular to the direction of the anchor bolts resulted in a modest increase of the breakout ultimate capacity and of the residual strength.

This study investigated the seismic resistance of thin, lightly reinforced walls strengthened in the out-of-plane direction by thick jacketing. To connect the thin existing wall and thick strengthening jacket, a tee shear connector consisting of one T-shaped steel section and several dowel bars and anchor bolts was used. Cyclic tests of four jacketed wall specimens were performed under out-of-plane lateral loading. The tests showed that the strength of the strengthened walls by thick jacketing was significantly enhanced. During the initial behavior, the tee shear connector performed well, not only as the shear connector, but also as the flexural tension reinforcement. However, as concrete damage increased during repeated load cycles, bond failure occurred early in the tee shear connector under flexural tension. The flexural strengths of the strengthened walls by thick jacketing were computed based on full and partial composite action of the tee section, and the bond and shear resistances of the tee shear connector were estimated in accordance with the provisions of ACI 318-19.