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The introduction of a restoring force technique has allowed the internal stress within kiln-dried lumber to be assessed, without requiring a modulus. However, an analytical model based on the elastic beam theory was only valid within a flexural range and only internal stress in the direction of the width was assumed to exist. Within this work, the model was extended to lumber, which could also contain some other internal stress components, by testing 30-mm-thick and 100-mm- to 130-mm-wide flat-sawn rubberwood boards. The improved model successfully separated the effects of other internal stress components in terms of a remnant force. Also, a finite element analysis was employed to validate the internal stress behavior. With little impact from other internal stress components, the finite element model, which used the released strain and Young’s modulus in the tangential direction, successfully simulated the restoring force profile for an entire half-split length, including the relatively short half-split length outside the flexural range. But the finite element model failed to perfectly capture the restoring force behavior in the presence of other internal stress components. Future work is required to fully investigate the internal stress in all three main orthogonal directions.

For decades, recycled coarse aggregate (RCA) has been used to make recycled aggregate concrete (RAC). Numerous studies have compared the mechanical properties and durability of recycled aggregate concrete (RAC) to those of natural aggregate concrete (NAC). However, test results on the shear strength of reinforced recycled aggregate concrete beams are still limited and sometimes contradictory. Shear failure is generally brittle and must be prevented. This article studies experimentally and analytically the shear strength of reinforced RAC beams without stirrups. Eight RAC beams and two controlled NAC beams were tested under the four-point flexural test with the shear span-to-effective depth ratio (a/d) of 3.10. The main parameters investigated were the replacement percentage of RCA (0%, 25%, 50%, 75%, and 100%) and longitudinal reinforcement ratio (ρw) of 1.16% and 1.81%. It was found that the normalized shear stresses of RAC beams with ρw = 1.81% at all levels of replacement percentage were quite similar to those of the NAC counterparts. Moreover, the normalized shear stress of the beam with 100% RCA and ρw = 1.16% was only 6% lower than that of the NAC beam. A database of 128 RAC beams without shear reinforcement from literature was analyzed to evaluate the accuracy of the ACI 318-19 shear provisions in predicting the shear strength of the beams. For an RCA replacement ratio of between 50% and 100%, it was proposed to apply a reduction factor of 0.75 to the current ACI code equation to account for the physical variations of RCA, such as replacement percentage, RCA source and quality, density, amount of residual mortar, and physical irregularity.

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