Study On The Mechanical Properties Of Glulam Covered Bridge Overall Structure And T-beam

Glued laminated timber structure has many remarkable advantages,such as excellent mechanical properties,good seismic resistance,green environmental protection,etc.In recent years,China has gradually applied modern glued timber structure with good effect,and the timber covered bridge with Chinese characteristics is worth inheriting and developing.In view of the technical problems restricting the design and construction of wooden structure buildings and engineering load-bearing members in China,it is necessary to carry out the research on the whole structure of covered bridges and the mechanical properties of glued timber beams in order to provide technical support for the independent construction of long-span and heavy-duty engineering timber bridges in China.The research object of this paper is the three-span wooden continuous beam covered bridge in Xuefeng Mountain,Dongkou,Hunan Province.Due to the environmental impact,the covered bridge may bear heavy wind and snow loads.In order to ensure the safety of the structure,the internal force analysis and force transmission mechanism of the wooden continuous beam covered bridge were studied.At the same time,according to the size of the bridge deck structure,the larch wood laminate and polyurethane structural adhesive are used to manufacture the glulam T-beam with a scale ratio of about 1/4.Experimental study and finite element analysis were carried out on the flexural performance of the glued wood beam,and the ultimate bearing capacity,failure mode and mechanism of the glulam beam were obtained.The main conclusions are as follows:.1)Using finite element software Midas Civil,considering the stress-deformation coupling effect between lounge structure and bridge deck structure,the overall structure model is established to analyze the static and stable characteristics of glulam bridges.The structure internal force and deformation of the lounge bridge are calculated under different load conditions,and the strength,stiffness and stability of the lounge bridge structure are checked by the most unfavorable load combination.The force law of the lounge bridge structure is obtained.The results show that the covered bridge design scheme is scientific and reasonable.2)Static bending failure test was carried out on glulam beam,through the analysis of deflection,strain,bearing capacity and other measured data of orthogonal T-beam,parallel T-beam and rectangular beam,The failure mechanism of glulam and the transverse distribution law of normal stress in flange plates of glulam T-beam were revealed,and the applicability of orthogonal glulam T-beam,a new component form,was evaluated.3)Based on the principle of stiffness equivalence,this paper proposes a strategy of equivalent orthogonal T-beam to parallel beam and then using Rammer formula to calculate its flexural shear strength,which extends the application range of Rammer formula.The comparison between experimental and theoretical calculation results shows that they are in good agreement.4)The finite element analysis software Abaqus was used to establish the glulam beam model corresponding to the test,and the data of mid-span deflection,stress and strain of each group of specimens under the corresponding load were analyzed,and the experimental failure mechanism of glulam T-beam was further revealed from the theoretical analysis.