Moment Resistance Performance of Dowel Based Connections in Wood Products

木材中螺栓连接的抗弯矩性能较差，这主要是由于木材的纵向抗拉强度和纵向抗剪强度较低。作为一种实际的解决方案，设计者有时可能会认为这种连接只承受剪切和轴向力，而忽略其承载弯矩的能力。问题是木材不知道它不应该携带力矩，即使在预期的载荷下也可能表现不佳。另外，非常细长的螺栓/销钉可以用于大间距和端距，这可能不是很经济。为保证螺栓弯矩连接的高效、安全使用，需要合理的设计指导。基本的问题是，剪应力和垂直应力的相互作用对木材和现代木制品还没有很好地理解。这两种破坏模式本质上都是脆性的，并且作为一种天然材料，木材的强度特性是非均匀和随机的。这些特点导致了竖向抗拉强度和纵向抗剪强度对应力体积都很敏感。受应力体积越大，强度越低。关于应力体积对这些相互作用应力的影响还没有全面的数据。此外，在地震需求的情况下，反向循环荷载对这些强度特性的影响尚未得到充分研究。****提出的工作将研究螺栓弯矩连接在单调和反向循环荷载下作为构件和结构框架的承载能力。考虑应力体积效应，研究垂直于晶粒的拉伸与剪切相互作用的脆性破坏模式。这些信息将为有效加固技术的设计提供指导。最后，将开发基于可靠性的设计程序，以使其性能符合地震和非地震载荷的要求。该研究的预期影响是更合理的设计程序，以考虑螺栓和销钉为基础的力矩连接，从而使用通用的非专有连接器实现更安全、更经济的设计解决方案。研究结果的成功实施将带来更好、更安全的木结构建筑，特别是对于更大、更高的木结构建筑市场。

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.****The proposed work will study the moment carrying capacity of bolted moment connections under monotonic and reverse cyclic loading as components and in structural frames. The interacting brittle failure mode of tension perpendicular to grain and shear will be studied with consideration of stressed volume effect. This information will lead to design guidance for effective reinforcement techniques. Finally, reliability based design procedures will be developed to qualify their performance to handle demands from both seismic and non-seismic loading. The expected impact of the study is more rational design procedures for consideration of bolted and dowel based moment connections leading to safer and more cost efficient design solutions using generic non-proprietary based connectors. Successful implementation of the results will lead to better and safer wood-based buildings especially for the bigger and taller wood building market.