Abstract
According to the facts of localized crushing failure of bolt groove in wood connection with enough end distance and the three-phase composites of wood with solid (wood substance), water, and gas, a confined compression test for the wood cylinder was conducted for achieving constitutive relation under the complex stress state in wood groove. A porous constitutive model was developed according to the confined compression experiments. Then, the constitutive model was implemented in a finite element modeling of mental dowel-type fasters in wood-to-wood connections to analyse the load-carrying capacity parallel to the grain. Through changing the thicknesses of centre members and side members of wood connections made of a similar wood species, Pinus Sylvestris var. Mongolica, the effects of thickness combinations of centre members and side members on the failure modes and load-carrying capacity of bolted wood connection including numerical simulations and experiments were compared. The failure modes, including the yielding of centre member, the yielding of side member, and the yielding of the bolt, as well as the rigid rotation of the bolt, all reappeared by the finite element modeling with the porous constitutive model. The predicted deformation shapes and load-displacement relations of bolted wood connections were compared with experimental ones, and good correlations were observed. This paper presents a new approach to simulate the local embedment crushing of bolt groove in wood connections.
Highlights
Finite element (FE) numerical simulation of the localized problem in wood structure is always a difficult issue due to the inevitable differences between FE results and experiment results. e reasons causing the differences involve the high variable mechanical properties of wood, differences between clear wood and structural wood, size effect, defects of wood, effect of moisture content, duration of load, and even the test method for material parameters for the localized compression wood
Sandhaas developed a continuum damage mechanics model including eight types of failure modes to simulate the performance of timber joints with the slotted-in steel plate, where the size effect for fracture energy was taken into consideration by means of the characteristic element length [4]
A new approach to simulate the localized issue of wood groove in bolted connection by applying the porous constitutive model for wood groove was established to mitigate the dependency on the experiences
Summary
Finite element (FE) numerical simulation of the localized problem in wood structure is always a difficult issue due to the inevitable differences between FE results and experiment results. e reasons causing the differences involve the high variable mechanical properties of wood, differences between clear wood and structural wood, size effect, defects of wood, effect of moisture content, duration of load, and even the test method for material parameters for the localized compression wood. Guan adopted a modification factor of the empirical modulus to simulate the stiffness of the flat nail embedment test, where a multiplier 0.25 was used [2]. In bolted wood connection, the stress state in wood groove is not uniaxial one. A new approach to simulate the localized issue of wood groove in bolted connection by applying the porous constitutive model for wood groove was established to mitigate the dependency on the experiences. In the process of groove crushing, the embedment stiffness of connection changes with the changing of the contact state. When groove crush is happening, embedment stiffness increases steeply which means that groove becomes compact and the wood void becomes small. The effect of embedment stiffness and strength will be reflected in the porous constitutive by the corresponding relationship between void ratio of wood and pressure on the porous medium
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