Historical steel trusses are still in use in many constructions and a significant number of them plays central load supporting role. Overtime, they may be subjected to substantial damage risks due to service loads, environmental and accidental actions. As a consequence, the stress in the historical steel truss members can surpass the yield strength of the material, which is not particularly high. In addition, corrosion can reduce considerably the cross-section, leading to an increase in the stress. Therefore, the need to perform structural assessment and safety evaluation for historical steel trusses become important issue.
The diagnosis relative to the preservation and safety of truss structures cannot be carried out except by determining the value of the stress in the truss members. In the context of historical constructions, static testing methods are generally not appropriate since non-destructiveness and respect of the original structure are highly required. As a result, dynamic testing methods are more applicable and advantageous. Based on dynamic tests, the overall objective of this research is to develop a non-destructive practical and reliable experimental technique to identify the real state of stress, i.e. tensile and compressive, in historical truss structures. After the stresses are determined, the structure’s stability and robustness can be concluded.
Several aspects to pay special attention include modelling and analysis of joint connections and global versus local dynamical behaviour of the truss structures. Another aspect is to manage uncertainties due to historical material and geometric properties, taking into account environmental and damage conditions as well as friction. Especially, friction in historical structures could affect drastically the condition of joints. To find out accurate assumptions and a methodology to analyze joints, if possible, taking into account friction, is also an ultimate goal of the research.
The research is carried out in several phases. In the first phase, the scientific development in the field was examined. This phase also consisted of numerical simulations and preliminary development of a technique to identify the real state of stress in different truss systems. In the next phase, an application to the Deutsche Forschungsgemeinschaft (DFG) for funding of experiments is prepared. Upon a success of the DFG application, a number of laboratory tests will be carried out. Calibration of the numerical and experimental results will verify the technique and further improvements will be made. Finally, in-situ tests for several case studies will be performed. Tests in laboratory and in real constructions, if possible, will also take into account the temperature variations and different loading scenarios.