Probabilistic concept for deformation-based design of hybrid elements like composite beams

组合构件的设计方法是基于半概率安全概念。抗力的安全系数基于材料的特性和统计分布。但是，根据材料组合和接头的延性，对于特定的复合构件，可能需要使用不同的安全系数和其他影响权重。从科学的角度来看，仅基于材料或复合材料接头的行为对安全系数进行简单的转换是不正确的。为了实现所需的安全水平，必须为组合构件开发一个可推广的安全概念。将使用众所周知的组合梁的例子来开发这个安全概念的基本原理。在现有的和新的组合梁试验中，将确定不同状态下荷载-变形-性能的统计分布。额外的有限元分析将通过参数研究扩大可用数据的数量。利用可靠度理论，对组合梁在正常使用极限状态和承载能力极限状态下的性能进行了分析。将在考虑组合接头中的滑移及其统计分布的横截面性能水平上进行评估。使用可靠性方法进行系统计算将导致在极限状态下对相关输入参数进行加权。因此，阻力的必要部分安全系数是合理的。组合梁在正常使用极限状态下的性能将根据变形进行评估。在此过程中，将考虑复合材料接头中的滑移。变形超限将成为梁性能概率评估中的一个新的失效准则。这利兹到一个新的方法，在设计组合梁，这是必要的，以保证所需的安全水平。最后，新的概念的理由，安全系数将被推广，以便它可以适用于不同类型的组合构件。

The design method for composite members is based on the semiprobabilistic safety concept. The safety factors for resistance are based on the characteristic behavior and the statistical spread of materials. But, depending on material combinations and ductility of joints, for a specific composite member it can be necessary to use different safety factors with other weighting of the influences. From a scientific point of view, a simple transformation of safety factors based only on the behavior of the material or of the composite joint is not correct. In order to realize the required safety level a generalizable safety concept has to be developed for composite members.The basic principles of this safety concept will be developed using the example of the well known composite beams. Out of existing and new composite beam tests the statistic spread of load-deformation-behaviour will be determined at different states. Additional FEM analysis will enlarge the number of available data by parametric studies. The behavior of composite beams will be evaluated at serviceability limit state and at ultimate limit state using the reliability theory. Evaluation will be done at the level of cross section performance taking into account the slip in the composite joint and its statistical spread.Systematic calculation using reliability method will lead to a weighting of the relevant input parameters in ultimate limit state. So the necessary partial safety factors for resistance can be justified. The behavior of composite beams at serviceability limit state will be evaluated on basis of deformations. In this process slip in the composite joint will be taken into account. The exceeding of deformation limits will be a new failure criterion in the probabilistic evaluation of the beam behavior. This leeds to a new approach in the design method for composite beams that is necessary to guarantee the required safety level.Finally the new concept for the justification of safety factors will be generalized so that it can be applied for different types of composite members.