In this paper, a simplified model is proposed for the shear strength of short shear walls based on the original three-parameter kinematic theory (3PKT). The model is built on first principles – compatibility of deformations, constitutive relationships and equilibrium – and aims to combine simplicity and accuracy for structural assessment applications. The model focuses on shear failures along diagonal cracks, while other failure modes such as sliding shear, out-of-plane instability, or detailing/lap splice failures need to be evaluated separately. The simplified 3PKT is validated with 29 specimens with a wide range of properties and is compared to the ASCE (ASCE 2014) and Japanese (AIJ 2001) seismic code shear provisions. It is shown that the model captures well the effect of all key test variables, and significantly reduces the conservatism and scatter of the code strength predictions. It is also shown that the proposed approach can be particularly helpful in the assessment of structures with less-than-minimum shear reinforcement to avoid costly and disruptive strengthening interventions.
Steel slag as a solid waste during steel-making has potential cementitious activity, and its use as supplementary cementitious material is an effective way to improve its resource utilization. Ethanol-diisopropanolamine (EDIPA), as an organic admixture, affects the hydration of the steel slag-cement composite system. In this paper, the effect of EDIPA on the hydration and mechanical properties of the steel slag-cement composite system was investigated by using mortar strength tests and combining with heat of hydration, X-ray diffraction (XRD), thermogravimetry/differential thermogravimetry (TG/DTG), scanning electron microscope (SEM) and other testing methods. The results show that EDIPA can improve both early and late compressive strength of steel slag-cement mortar at low dosing (0.02%). However, at high dosing (0.06%, 0.10%), EDIPA is unfavorable to early strength, but enhanced late strength more strongly than low dosing. Low dose of EDIPA can promote the hydration of steel slag-cement composite pastes, and can also improve the hydration degree in the early and late stages. At low dosing, EDIPA can promote the formation of ettringite (AFt) and facilitate the transformation from AFt to monosulfoaluminate (AFm). In addition, EDIPA affects the crystal structure and morphology of Ca(OH)2 prepared by co-precipitation method. And the morphology of Ca(OH)2 gradually changes from long hexagonal column to short hexagonal column and then to irregularly radiating lamellar with the increase of EDIPA dosing. This indicates that EDIPA inhibits the vertical growth of Ca(OH)2 and has the reference sig-nificance for the change of Ca(OH)2 morphology in the composite paste.
The extended multi-directional non-orthogonal crack model was applied to the joint interface area between RC members connected by shear dowel and the experimental verification was conducted in use of the low cycle fatigue experiments. The splitting tension field induced by the dowel action around the reinforcing bar is successfully reproduced with the coupled joint crack model and the beam finite elements, and the splitting tension cracking under cyclic fatigue loading and the joint degradation were fairly captured computationally. The effect of spiral steel confinement on the shear dowel performance can be quantitatively evaluated by the generic full 3D nonlinear analysis.