Mechanical performance of single-layer reticulated glulam shells with semi-rigid prefabricated planted-bar joints

In order to study the mechanical behavior of new type reticulated glulam shells with prefabricated planted-bar joints, six groups of specimens, totally 18 specimens, with two different cross sections were designed and manufactured. The tests of eccentric compression behaviors, considering different eccentricities including three load cases of 0 mm, 50 mm and 100 mm respectively, were conducted. In addition, the effects of eccentricity, axial compression and the variation of the cross section on the semi-rigid characteristics of the joints were evaluated. It is found that three typical failure modes at joints may occur, including the local buckling of steel members in core areas, the yield of planted-bar in wood members and the fracture of wood members in compression zone. Eccentricity can affect the failure mode of the joints, and is proportional to the initial rotation stiffness of the joint. With the same eccentricity, rectangular cross section specimens are superior to square cross section specimens in terms of the ultimate bending capacity, but inferior to the latter in the rotational ductility. The smaller the eccentricity, the more obvious the effect of axial force on the initial rotational stiffness, and the greater the initial rotation stiffness. The moment-rotation curve of joint was obtained from the tests, and the semi-rigid moment-rotation equation was fitted, which considered the effects of eccentricity, axial force, and section type on the semi-rigid characteristic, introduced initial stiffness coefficient, compression influence factor and curvature shape coefficient, and used power function to improve the model. An example of single-layer reticulated spherical shell was calculated using the fitted equation, and completely analysed for whole load-deformation process. It is found that the ultimate load carrying capacity of reticulated shell using the new type assembled joints is much greater than the one whose joints are considered as pinned joints. The trend of complete load-displacement curve is close to the one whose joints are considered as rigid joints. In addition, the whole structure has a certain stability capacity and ductility.