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

复合构件的设计方法基于半概率安全概念。电阻的安全系数是基于材料的特性行为和统计扩散。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权重的影响。从科学的角度来看，仅根据材料或复合接头的行为简单地转换安全系数是不正确的。为了实现所要求的安全水平，必须对复合材料构件提出一种一般化的安全概念。这一安全概念的基本原则将以众所周知的组合梁为例加以阐述。通过现有的和新的组合梁试验，确定了组合梁在不同状态下的荷载-变形特性的统计分布。额外的有限元分析将通过参数研究扩大可用数据的数量。采用可靠度理论对组合梁在使用极限状态和极限状态下的性能进行了评估。考虑复合材料接头的滑移及其统计扩散，在截面性能水平上进行评价。采用可靠性方法进行系统计算，在极限状态下对相关输入参数进行加权。所以抵抗的部分安全系数是合理的。组合梁在使用极限状态下的性能将根据变形进行评价。在此过程中，将考虑复合材料接头的滑移。变形极限的突破将成为梁性能概率评价中的一种新的破坏准则。这为保证组合梁的安全水平提供了一种新的设计方法。最后对安全系数论证的新概念进行了推广，使其适用于不同类型的复合构件。

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.