Moment Resistance Performance of Dowel Based Connections in Wood Products

由于木材的垂直于纹理的张力和纵向剪切强度较低，木材中螺栓连接的抗弯性能较差。作为一个实际的解决方案，设计师有时可能会考虑这样的连接，作为销只承担剪切力和轴向力，忽略其弯矩承载能力。问题是木材不知道它不应该承载力矩，即使在预期的载荷下也可能表现不佳。或者，非常细长的螺栓/销钉可以与大的间距和端部距离一起使用，这可能不是非常经济。需要合理的设计指导，以使螺栓力矩连接能够有效和安全地使用。基本问题是，对于木材和现代木制品，剪切和拉伸垂直应力的相互作用效果还没有很好地理解。这两种破坏模式本质上都是脆性的，木材作为一种天然材料，其强度特性是不均匀和随机的。这些特点导致了垂直于纹理的拉伸强度和纵向剪切强度都对应力体积敏感。应力体积越大，强度越低。关于应力体积对这些相互作用应力的影响，目前还没有全面的数据。此外，反向循环荷载对这些强度特性的影响，如地震要求的情况下，还没有得到充分的研究。

The moment resistance of bolted connections in wood is poor due to the low tension perpendicular to grain and longitudinal shear strengths of wood. As a practical solution designers may sometimes consider such connections as pinned to only carry shear and axial forces and ignore their moment carrying capacity. The problem is that the wood does not know that it is not supposed to carry moment and could perform poorly even under the intended loading. Alternatively, very slender bolts/dowels can be used with large spacing and end distances which may not be very economical. Rational design guidance is needed to allow bolted moment connection to be used efficiently and safely. The fundamental problem is that the interacting effect of shear and tension perpendicular stresses is not well understood for wood and modern wood products. Both modes of failure are brittle in nature and as a natural material the strength properties of wood are nonhomogeneous and random. These features lead to the fact that tensile perpendicular to grain and longitudinal shear strengths are both sensitive to stressed volume. The larger the stressed volume, the lower the strength. Comprehensive data is not available on the effect of stressed volume on these interacting stresses. Furthermore, the influence of reverse cyclic loading on these strength properties as in the case of demands from earthquakes have not been fully studied.