| The object of "strong column and weak beam" has been specified in ChineseNational standard code for seismic design of buildings. But in fact in general designworks, this object often fails because the influence of the reinforcement within slab tomoment bearing capacity of beam has not been accounted. On the contrary, the structurewill become strong-beam-and-weak-columned. It is shown in the investigation work forWenchuan Earthquake there are a large amount of buildings of strong-beam-and-weak-columned behavior in our country. They are all with poor anti-seismic capacity and maybecome heavy potential risks in the future.A representative part from the frame structure is selected, and two1.5m×6mframework specimen is produced according to the ratio of1:2.4. The115mm triangularslot is opened in the floor of the frame structure near the beam-column joints for jointwith slot around. By dynamic test of using piecewise harmonic amplitude displacementcontrol, two specimens is loaded. The destruction process of the two specimens isobserved. The destruction process, the failure mechanism and the seismic performanceare analysed. The effect of the floor open-angle joints is evaluated.The main conclusions are as follows: It is shown that for the traditional cast-in-situreinforce concrete frame joint, because the influence of the reinforcement within slab, thebearing capacity of beam is increased, failure mechanism present "column hingemechanism", and there is "strong beam and weak column" phenomenon; After openingtriangular slot in floor, the column end stress and the extent of damage are reduced, thecolumn reinforcement yield is postponed; The beam end stress are increased, most beamreinforcement are yielded; For the beam end there is visible damage; There isn’t "strongbeam weak column" phenomenon; Energy dissipation capacity increase slightly, ductilityreduce slightly, and little change in stiffness; Opening triangular slot measure has a goodeffect, and improves a true "strong column weak beam". |
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