Cross laminated timber (CLT), as a structural plate-like timber product, has been established as a load bearing product for walls, floor and roof elements. In a bending situation due to the transverse shear flexibility of the crossing layers, the warping of the cross section follows a zigzag pattern which should be considered in the calculation model. The Refined Zigzag Theory (RZT) can fulfill this requirement in a very simple and efficient way. The RZT, founded in 2007 by A. Tessler (NASA Langley Research Center), M. Di Sciuva and M. Gherlone (Politecnico Torino) is a very robust and accurate analysis tool, which can handle the typical zigag warping of the cross section by introducing only one additional kinematic degree of freedom in case of plane beams and two more in case of biaxial bending of plates. Thus, the RZT-kinematics is able to reflect the specific and local stress behaviour near concentrated loads in combination with a warping constraint, while most other theories do not. A comparison is made with different methods of calculation, as the modified Gamma-method, the Shear Analogy method (SA) and the First Order Shear Deformation Theory (FSDT). For a test example of a two-span continuous beam, an error estimation concerning the maximum bending stress is presented depending on the slenderness L/h and the width of contact area at the intermediate support. A stability investigation shows that FSDT provides sufficiently accurate results if the ratio of bending and shear stiffness is in a range as stated in the test example. It is shown that by a simple modification in the determination of the zigzag function, the scope can be extended to beams with arbitrary non-rectangular cross section. This generalization step considerably improves the possibilities for the application of RZT. Furthermore, beam structures with interlayer slip can easily be treated. So the RZT is very well suited to analyze all kinds, of shear-elastic structural element like CLT-plate, timber-concrete composite structure or doweled beam in an accurate and unified way.

交叉层压木材（CLT），作为结构性板状木材产品，已被确立为墙壁，地板和屋顶元件的承重产品。在由于交叉层的横向剪切挠性而产生的弯曲情况下，横截面的翘曲呈锯齿形，在计算模型中应予以考虑。精确的曲折理论（RZT）可以以非常简单和有效的方式满足这一要求。RZT由A. Tessler（美国国家航空航天局Langley研究中心），M。Di Sciuva和M. Gherlone（Politecnico Torino）于2007年创建，是一种非常强大且准确的分析工具，它可以处理横截面的典型之字形翘曲。对于平面梁，仅引入一个附加的运动学自由度；对于板的双轴弯曲，仅引入另外两个运动学自由度。从而，RZT运动学能够结合翘曲约束反映集中载荷附近的比应力和局部应力行为，而大多数其他理论则不能。使用不同的计算方法进行了比较，如改进的伽玛方法，剪切模拟方法（SA）和一阶剪切变形理论（FSDT）。对于两跨连续梁的测试示例，根据细长L / h和中间支撑处的接触区域宽度，给出了有关最大弯曲应力的误差估计。稳定性研究表明，如果弯曲刚度和剪切刚度之比在测试示例中所述的范围内，则FSDT可提供足够准确的结果。结果表明，通过简单地修改Z字形函数，范围可以扩展到具有任意非矩形横截面的梁。该概括步骤大大提高了RZT应用的可能性。此外，具有层间滑动的梁结构可以容易地处理。因此，RZT非常适合以准确而统一的方式分析各种剪切弹性结构元素，例如CLT板，木材-混凝土复合结构或组合梁。