The Effect Of Jacking And Loading Methods On The Bending Performance Of Prestressed Glue-lumber Beams

Ordinary glue-lumber beams' compressive strength can not be fully exploited,they always suffer brittle failure and have large deformation.Prestress is applied to ordinary glue-lumber beams can reduced glue-lumber beams short-term deformation,and make the beams by pure bending state into compression bending state,to make full use of the compressive strength of wood.At present,the domestic and foreign scholars and the previous study of the project team,have been done deeply research in the selection of glue-lumber,various fiber materials reinforced glue-lumber beams,as well as the influence of the prestressed values and the number of prestressed steel wires on the bending performance of the glue-lumber beams.The study of the influence of the anchoring device and the jacking and loading methods on the bending performance of prestressed glue-lumber beams is still blank,and lack of finite element simulation analysis.For the problems mentioned above,following work have been carried out in this paper.Put forward the "extracorporeal" end anchorage device.3 groups 9 prestressed gluelumber beams were tested by 3 different kinds of anchoring devices,such as "slotted","extracorporeal" and "boots type",the bending performance of prestressed glue-lumber beams under 3 different anchors was analyzed.The results showed that: Compared with the "slotted" anchoring device,the "extracorporeal" anchoring device can not improve the bearing capacity of the beam,but the beam can be changed from brittle failure to ductile failure,to a certain extent optimize the performance of the beam;Compared with the other two kinds of anchoring devices,the "boots type" anchoring device can improve the bearing capacity of the beam by 30.1%,and the beam can be better pre-force effect,failure modes also represents the top beam compression failure.But due to the beam end of constraints,will damage the end of the beam.Using one point jacking and one point loading,one point jacking and two points loading,two points jacking and one point loading,two points jacking and two points loading with four different jacking and loading methods to bend test of four groups 12 prestressed glue-lumber beams,we measured the effects of the four different jacking and loading methods on the bending performance of prestressed glue-lumber beams.The results show that:In the same preenergizer preconditions,the same loading point,changing the way of jacking has little effect on ultimate bearing capacity of glue-lumber beams;The same jacking point,two loading points than one loading point the glue-lumber beams ultimate bearing capacity increased by about 28.8%~38.9%;Only when two points jacking and two points loading the top of the beam compression zone wrinkles and beam bottom occurs ductility tensile failure,the remaining failure modes are brittle beam bottom tensile failure;Loading process,the two points loading than one point loading beam can make the timber's compressive strength play more fully and improve the utilization rate of wood and steel wir.And given the calculation formula of the maximum bending moment of the four cases,which provides the theoretical basis for the test results.Modeling and analysis by using the finite element software ABAQUS to establish finite element method under four jacking and loading method and three points loading,uniform loading of prestressed glue-lumber beams.The influence of jacking and loading method on the bending performance of prestressed glue-lumber beams have been analyzed.The results were compared with that from the tests and the deviation was analyzed.Finally,combined with the beam bending theoretical analysis,given the jacking and loading method of the proposal.