| Poplar LVL(Laminated Veneer Lumber)orthogonal rib-beam floor is a spatial floor system composed of bidirectional orthogonal Poplar LVL rib-beam and OSB(Oriented Strand Board).In order to study the mechanical performance of Poplar LVL floor under horizontal load,research group carried out the horizontal loading test of traditional floor and box floor with different rib-beam heights,different loading directions,obtained the performance changes of bearing capacity,plane stiffness and ductility of the floor and established the calculation formula of horizontal lateral movement across the span of Poplar LVL orthogonal rib-beam floor.The specific work and conclusions of the research were as follows:(1)The physical and mechanical properties of Poplar LVL standard materials were carried out to obtain the density,flexural elastic modulus and flexural strength,compressive strength,tensile strength,shear strength of LVL-OSB nail joints and load-slip curve of Poplar LVL.(2)Eight Poplar LVL orthogonal rib-beam floor with plane size of 4.8m×3.6m were designed and manufactured.The four-point symmetrical horizontal loading tests in two directions were carried out respectively,and the evolution rules of floor performance such as plane bearing capacity,plane stiffness and ductility were obtained.The difference of plane stiffness and bearing capacity between traditional floor and box floor with different rib-beam height and loading direction were analyzed.The results show that:①The main failure phenomena of the floor was the sliding,tilting and pulling out of the nails between the bezel of the specimen and the OSB.The buckling of OSB panel and the local crushing of poplar LVL beam at the support pad;②When the height of the rib-beams was the same,the stiffness,bearing capacity and ductility of the box floor are better than those of the traditional floor,which indicated that the skin effect of the cladding panels could greatly improve the floor plane performance.③The bearing capacity of the same floor along the short span direction was higher than that along the long span direction;④For the same structural floor,the stiffness and ductility of the floor with a height of 285mm rib-beam were better than those with a height of 235mm rib-beam,indicating that the increase of the height-span ratio of rib-beam could effectively improve the floor plane performance.⑤The shear capacity of the specimens all meet the requirements of the wood structure design standard of 6.40kN/mm.The internal ribbeams of the specimens were basically intact,indicating that they have good integrity.(3)The numerical analysis model of the Poplar LVL floor was established by ABAQUS,and the analysis results were compared with the test results,and the two were in good agreement.Through the extended analysis of the model,the effects of plate thickness,ribbeam spacing and angle steel strength on the flat performance of the floor were analyzed,and the results show that the lateral resistance performance of the plane increases significantly with the increase of rib-beam height,plate thickness and angle strength,among which the plate thickness increases the stiffness of the floor the most obviously.(4)The horizontal lateral displacement and stiffness of the floor span of the orthogonal rib-beam of Popular LVL were calculated by IBC-2012,FEMA273 and NZSEE 2006.On this basis,the formula for calculating the horizontal lateral displacement of the floor span was established by using the modified "equivalent beam" theory.The results show that the average error of FEMA273 and NZSEE 2006 is 19.37%and 24.32%.The average error of mid-span horizontal lateral displacement of the floor with orthogonal rib-beams obtained by using the modified "equivalent beam" theory was about 14.77%,indicating that this formula was more suitable for theoretical calculation of Popular LVL floor. |
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