12.07.2015 Views

Report - PEER - University of California, Berkeley

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knee joint exterior interior 3D interiorloadingdirectionjoint shearcapacity(in MPa)ACI 352type I(2002)0.083γ f' cA jγ = 120.6γ = 150.75γ = 201.0γ = 241.33AIJGuidelines(1999)0.7κφ × 0.8f' c Ajk = 0.4 k = 0.7 k = 1.0 k = 1.0φ = 0.85 φ = 0.85 φ = 0.85 φ = 1.00.400.701.01.18Figure 1. Comparison <strong>of</strong> configuration factors for joint shear design.Recently a novel model was proposed by the author (Shiohara 2001, 2002a,2002b, 2003, 2004). The model is much simpler than the FEM, but is comprehensiveenough and unified in which joint shear failure for all types <strong>of</strong> beam-column jointswith different configurations is intrinsically incorporated (Shiohara 2004). This theoryrequire no empirical assumptions accounting the difference in strength and type <strong>of</strong> failure,despite <strong>of</strong> various geometry <strong>of</strong> beam-column joints. This paper reports a correlationstudy with theoretical prediction by the model and in particular, test results <strong>of</strong>knee joints.2. QUADRUPLE FLEXURAL RESISTANCE AND MODELING2.1 Behavior <strong>of</strong> Quadruple Flexural ResistanceThe new behavior model for shear failure <strong>of</strong> interior beam-column joints as well asknee joints are depicted in Fig. 2. In tests, two diagonal opening <strong>of</strong> cracks usuallybecomes dominant. So in this model, shear deformation <strong>of</strong> the joint panel is assumedprimarily due to the rotation <strong>of</strong> the four triangular concrete segments and the opening<strong>of</strong> the cracks. Thus rotational movements <strong>of</strong> the segments are caused by uneven opening<strong>of</strong> the diagonal cracks like flexural cracks at the diagonal boundaries <strong>of</strong> the segments.When moment is applied to the segments from adjacent beams and columns,rotation <strong>of</strong> the segments occur as shown in Figs. 1(b) and 1(c) for knee joint underclosing and opening loads respectively. Because four sets <strong>of</strong> flexural resisting actionare identified in the moment resistance <strong>of</strong> the beam-column joints in this mode, it isnamed quadruple flexural resistance.2.2 J (Joint) Mode and B (Beam) ModeBeam-column joints need to be designed such that the contribution <strong>of</strong> shear deformationin the joint in total story should be minimized by achieving desirable hierarchy <strong>of</strong>458

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