ACI 369.1M-17 Standard Requirements for Seismic Evaluation and Retroft of Existing Concrete Buildings (ACI 369.1M-17) and Commentary

ACI 369.1M-17 Standard Requirements for Seismic Evaluation and Retroft of Existing Concrete Buildings (ACI 369.1M-17) and Commentary. 3.5—Development and splices of reinforcement Development of straight bars, hooked bars, and lap-spliced bars shall be calculated according to the provisions of ACI 318M, with the following modifcations: a) Deformed straight, hooked, and lap-spliced bars satisfying the development requirements of Chapter 25 of ACI 318M-14 using expected material properties shall be deemed capable of developing their yield strength, except as adjusted in the following: i. The development of lapped straight bars in tension without consideration of lap splice classifcations is permitted to be used as the required lap splice length. ii. For columns, where deformed straight and lap-spliced bars pass through regions where inelastic deformations and damage are expected, the bar length within those regions shall be considered efective for anchorage only until inelastic deformations occur. In such cases, the develop- ment length obtained using ACI 318M procedures shall be compared with a degraded available development length ℓ b-deg , as defned in (b) in the following. C3.5—Development and splices of reinforcement Development requirements in accordance with Chapter 25 of ACI 318M-14 are applicable to development of bars in all components. Chapter 18 of ACI 318M-14 provides development requirements that are intended only for use in yielding components of reinforced concrete moment frames that comply with the cover and confnement provi- sions of Chapter 18 of ACI 318M-14. Chapter 25 of ACI 318M-14 permits reductions in lengths if minimum cover and confnement are present in an existing component. For additional information on development and lap splices, refer to ACI 408R, and for hooked anchorage, refer to Sperry et al. (2005). Equation (1a), which is a modifed version of the model presented by Cho and Pincheira (2006), refects the intent of ACI 318M development and splice equations to develop 1.25 times the nominal bar strength, referred to in this stan- dard as the expected yield strength. The nonlinear relation between developed stress and development length refects the efect of increasing slip and, hence, reduced unit bond strength, for longer development lengths. Refer to Elwood et al. (2007) for more details. Bond strength can be signifcantly curtailed in damaged regions within plastic hinges (Sokoli and Ghannoum 2016; Ichinose 1995). The length where bond capacity is curtailed during inelastic deformations is recommended to be two- thirds of the section efective depth d (Sokoli and Ghan- noum...