| China is an earthquake-prone country, and hysteretic model of prestressedconcrete can provide theoretical basis for repair of damaged structure, strengtheningand safety evaluation after earthquake, so it has very important application value. Inaddition, it is necessary to research the hysteretic model of unbonded prestressedconcrete structures because of uncertainty of earthquakes and complexity of thecalculation of unbonded prestressed concrete structures. In this paper, on the basis ofthe test of simply-supported concrete beams partially prestressed with symmetricalunbonded tendons under low cyclic reversed loading, the moment-curvaturehysteretic model of these structure is established. Then based on the research ofhysteretic characteristics and restoring force characteristics of unbonded partiallyprestressed concrete beams, the hysteretic model of concrete frame beams prestressedwith unbonded tendons on the bottom is analyzed. The main contents of this paper areas follows:(1) A brief overview of the domestic and international scholars about hystereticmodel of reinforced concrete,and points out the shortcomings, thereby the necessityof establishing the hysteretic model of unbonded prestressed concrete beams is putforward.(2) The source of the test data of concrete beams partially prestressed withsymmetrical unbonded tendons is introduced. Based on the test data, the calculationformulas of related features in hysteretic model are point out, and the hysteresis rulesare put forward, so the moment-curvature hysteretic model of concrete beamspartially prestressed with symmetrical unbonded tendons is established.(3) According to the moment-curvature hysteretic model presented in this paper,a MATLAB program about this test and a experiment conducted by a Japanese scholarHiroshi MUGURUMA is developed. It shows that the calculating results are wellagreed with the test results. The correctness of the restoring force model hystereticmodel is demonstrated.(4) Referring to the thought of the program about concrete beams partiallyprestressed with symmetrical unbonded tendons, the hysteretic loops of5concreteframe beams prestressed with unbonded tendons on the bottom under vertical lowcyclic reversed loading are calculated on the basis of their hysteretic model established before. |
