Study On Pull-out Resistance Of Rod Glued In Post-injection Glulam

Timber structures are the representative of green building,it has environmental-friendly,ecological,recyclable and other advantages.From the application situation at home and abroad,modern timber structure can be used in office buildings,shops,residential buildings,schools,kindergartens,nursing homes,hotels,sports venues and exhibition centers,and glue wood in the above buildings have been effectively applied.Glued wood structure mainly includes wood frame structure and long-span wood structure,and its joint performance has always been the focus of research.There are several types of connections,such as glued-in rod connection,bolt and bolt pin type connection.The glued-in rod connection of glulam wood is a new type of connection,which is made by gluing one end of the planting bar into the drilled glulam wood through adhesives and connecting the other end with other components.As a new type of connection,this kind of connection has the advantages of high stiffness,high bearing capacity,good durability and convenient construction.In order to fully reflect these advantages,a lot of studies have been carried out at home and abroad on the bonding and anchoring performance,seismic performance and ultimate bearing capacity of glulam connection with the glued-in rod.There are relatively few studies on glulam connection with the glued-in rod and their applications are not very extensive in China.Given that,a postinjection glue-in rod connection method is proposed in this thesis,which is easy to be glued and installed.Referring to the design of concrete planting bar and the design code of wood structure,the rationality of the design is verified by numerical simulation,and then the pullout performance of the connection specimen is studied by experimental method,which provides a reference for the design and application of glulam connection with the glued-in rod.The main research works in this thesis are summarized as follows:(1)A kind of post-injection glulam connection with glued-in rods specimen suitable for field assembly was designed.Referring to the design of the implant-steel between concrete,the design specifications of timber structures and relevant literature,the geometric parameters such as the diameter of bar planting hole,the bar diameter,implantation depth of glued-in rod,the diameter of lateral injection hole and the number of lateral injection hole were determined.The characteristic parameters of Douglas fir glulam were determined by wood property test.(2)In order to preliminarily analyze the difference of the pull-out performance between and without lateral glue holes,the proposed finite element analysis was carried out for the two types of reinforcement glued-in rods.The results show that the pull-out performance of the post-injection glulam connection with glued-in rods specimens is no less than that of the preinjection glulam connection with glued-in rods without the lateral hole.(3)The pull-out test of glulam connection with glued-in rods test piece has been carried out.Two groups of specimens were used,seven in each group,including a traditional preinjection type specimen(no lateral hole).In addition to the depth of the lateral injection hole,the influence of the diameter of bar planting hole,the implantation depth of glued-in rod,the diameter of bar planting,the diameter of lateral injection hole and the number of lateral injection hole on the drawing resistance of the specimen is considered.The test results show that the size of the injection hole has little effect on the pull-out resistance of the specimens;the specimens with lateral injection hole satisfy the design bearing capacity of the specimens and are easy to install,and the number of lateral injection holes should be two;the increase of anchorage length can effectively improve the pull-out resistance,but the increase of anchorage length of the glued-in rods reduces the nominal shear strength of the wood-adhesive interface;the larger the diameter of the glued-in rods,the greater the pull-out strength.Along with the pull-out force get bigger,the initial stiffness of the specimen gets bigger.With the increase of the thickness of the adhesive layer,the pull-out resistance increases,but the excessive thickness of the adhesive layer will prolong the curing time after injection,especially for the steel-planted specimens with large anchorage length,so it is necessary to adopt a moderate thickness of the adhesive layer.In a word,the reasonable design of the number of lateral injection holes and the thickness of the adhesive layer can make the post-injection glulam connection with glued-in rods easy to install,ensure the quality of injection glue and have good pull-out resistance.