Research And Design On Hollow Post-beam System Of Glulam Timber Architecture

Larches,with excellent mechanical properties,are widely distributed in northeast China.With the implementation of our nation's Natural Forest Protection Project and the development of buildings with timber structures,the demand for thinning wood and artificial forests is increasingly growing.Currently,using small-diameter larch as the structural building timber has several disadvantages such as poor dimensional stability,low strength and hardness,and high stress,etc.Many factors lead to the difficulty in the processing and utilization of small-diameter larches.Glulam,which is made with the gluing technique,is characteristic of various complex shapes and efficient utilization of materials,which provides an opportunity for the small-diameter wood to be used as the structural timber.This research has fabricated glulam materials and produced medium-sectioned hollow structural glulam by small-diameter larch.The pin groove bearing performance of solid larch;bolt-steel plate hollow glulam node ductility performance;hollow glulam beam bending performance,lateral force resistance performance of hollow glulam post-beam system been studied.By parametric design method,the glulam building was designed.It also analyzed mechanical properties of each components and feasibility of parametric design for wooden architecture through the finite element simulation.The results of the study are summarized as follows:(1)According to the comparison between the test values and the calculated values of each country,the error of the calculated value of NDS and the test value was minimal,in the range of2.4?7.4%.When the load direction is parallel to the direction of the specimen,the yield strength increased with the increase of density,and decreased with the increase of the bolt diameter.Through the single bolt connection node bearing capacity test,it is concluded that the yield load increased with the bolt diameter and level increase.The initial stiffness and ultimate load increased with the bolt diameter increase.According to the calculation value of chinese code and NDS,the error of the bearing capacity is in range of 1.4%?18.5% and 7.3%?21.8%.(2)The failure mode of the single bolt and steel plate node is related to the width of the specimen,the bearing width and the diameter of bolt.When the width-diameter ratio is greater than or equal to 14.4,the node damaged with wood split off.When the ratio is greater than or equal to 10.9 and less than or equal to 12.5,the node damaged with double plastic hinge bending yield of the bolted.When the ratio is less than or equal to 10.0,the node damaged with single plastic hinge.The ductility of node is good in the firstly two modes.When the ratio is between12.5?16.4,the node is optimal in ductility performance.When the width-diameter ratio between10.0?10.9,the value is the critical point of the single plastic hinge and double plastic hinge failure mode.The diameter of the bolt has a great influence on the bearing capacity of the node.When the node width in the range of 140?230mm,the bolt diameter can be taken as 14 mm or16mm.The test values have certain error with Chinese and the US timberwork design handbook,the error is between 21.5%?159.0% and 4.3%?168.1% respectively.It is reasonable to according to the GB 50005 with the bearing capacity calculation of this node,the error is 4.4%? 39.5%.(3)Based on the simulation calculation of the bending performance,it is better to choose the hollow beam with rectangular section.Three failure mechanism were observed about the hollow beams,which were characterized by brittle tensile failure initiated at the tension face of the beam.The average deflection of the hollow glulam beams was 62.3mm,which was bigger than the allowable design value of 13.8mm.The maximum ultimate deflection can reached l/ 47 before damaged.The apparent bending stiffness is 0.86 times the calculation value.The characteristic apparent modulus of elasticity is 12140 MPa when the hollow section ranges from25% to 40% and the wall thickness greater than 20 mm.A reduction coefficient 0.86 should be added to calculate the bending stiffness.A calculation model for the ultimate bending moment was proposed,and the calculation values were consistent with the test values.The finite element value simulated by ABAQUS is in good agreement with the test value,and the bearing capacity error is 11.9%,and the limit moment error is 7.3%.(4)Both of the pure post-beam frame structure and the frame-herringbone supported post-beam structure have anti-lateral force.The pure frame structure has a weak bearing capacity as the anti-lateral force structure system.The herringbone support brings the large antiliteral stiffness and bearing capacity,6.3 and 2.75 times the pure frame,respectively.But it does not show good ductility performance,0.67 times the pure frame.Before the overall structural failure,each specimen strength degradation is less than 30%,showed the enough surplus capacity.The structural design proposal was given,the plane stability of frame-herringbone support should be checked in advance.The hysteresis curve and the skeleton curves simulated by ABAQUS were in good agreement with the test value.(5)The digital development of architectural design's graph theory has been taking as an entry point to analyze the wooden ones built through parametric design.The parametric design was selected to design the hollow glulam structure with large-span post-beam systerm and the design process was improved to fit the environmental characteristics.After the model analysis on structural stability and anti-seismic property by finite element method,the result that the bearing and deformation capacity of this structure is in compliance with norms has been received.Included the wind and snow load,the maximum deformation was2.26 times increased.