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Report - PEER - University of California, Berkeley

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Maximum nodal moment (test)Maximum nodal moment (predicted)2.01.61.20.80.40.00.2J (Joint) failureB (Beam) failureBJ failureAnchorage failure0.40.60.81.0M j / M b = 1.07 M j / M b = 1.00(a) openingdirection1.21.41.60.20.40.60.81.01.2(b) closingdirection1.41.61.8M j (predicted) / M b (predicted)M j (predicted) / M b (predicted)Figure 6. Correlation <strong>of</strong> strength and failure mode.The average <strong>of</strong> the ratio <strong>of</strong> observed strength to predicted one is 1.01 for closingloading and 1.04 for opening loading respectively. It shows good correlation. It shouldbe noted, test results shows that the strength under closing load is always larger thanthat under opening loading. The model account for this tendency correctly for theinventory data, which includes specimens with joint failure and beam failure.In Fig. 6, the fifty one specimens are plotted to compare the observed and calculatedresults listed in Table 2. Horizontal axis shows the ratio <strong>of</strong> M j /M b . Vertical axisshows the observed strength normalized by M b . The predicted strength by the modelshow good correlation with test result, except the specimens which exhibited prematureanchorage failure in the tests.It is also observed that all the specimens which exhibited beam yielding failure intests, have value <strong>of</strong> M j /M b larger than 1.07 for opening and 1.00 for closing except twospecimens. Hence, the ratio <strong>of</strong> M j /M b is good index to predict the failure mode <strong>of</strong> kneejoint if the longitudinal bars in beams and column are satisfactory anchored in kneejoint. The value <strong>of</strong> M j /M b <strong>of</strong> 1.0 may be good criteria for discriminate joint shear failurefrom beam yielding failure.5. CONCLUDING REMARKSA new theory <strong>of</strong> Quadruple flexural resistance in reinforced concrete monolithicbeam-column joint was applied to knee joints. Although the theory is based on a simpleconcept, it has an potential to predict both strength and failure type, reflectingessential critical parameters affecting the behavior <strong>of</strong> beam-column joints. The modelcontains no empirical factors accounting the difference between interior, exterior orknee joint like a configuration factors adopted in current design codes. It is demonstratedthat the quadruple flexural resistance is applicable to knee joint. The calculatedvalue <strong>of</strong> joint capacity and predicted failure mode agree well with wide variety <strong>of</strong>specimens in inventory <strong>of</strong> tests data <strong>of</strong> knee joint.466

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