Photographic strain monitoring during full-scale failure testing of Örnsköldsvik bridge

Abstract

Full-scale failure tests are rarely performed on structures, primarily due to their high costs and the lack of suitable test objects. This article reports the results of a 'test-to-failure' performed using a real bridge. The results obtained in such tests are valuable for assessing analytical models, updating finite element models and investigating the real behaviour of structures. The specific intention in these experiments was to study the shear failure of the bridge, which is a less wellunderstood mode of failure than is bending. To this end, it was necessary to strengthen the bridge using near-surfacemounted reinforcements made of carbon fibre-reinforced polymer bars in order to prevent bending failure. The bridge was heavily monitored during the test, using both traditional sensors such as electrical strain gauges and linear variable differential transducers alongside new monitoring systems such as fibre-optic sensors, strain rosette linear variable differential transducers and a novel photographic monitoring system. This article presents the photographic strain measurements and describes the use of the photographic tools in monitoring and characterizing the behaviour of the failure zone during the full-scale test. The strains measured using the photographic method were found to agree well with those measured using classical strain gauges. In addition, the strain contour plots generated using the photographic method provided crucial insights into the strains within the bridge's failure zone. This study was conducted under the remit of the EU 'Sustainable Bridges' Project.

Nonlinear FE analysis of a full scale in situ test on a RC bridge by means of a 1D layered frame model

“…Strains and deflections were mainly measured under the point loads and close to the supports. A new methodology based on photographic strain monitoring was also applied providing very interesting information on the development of strain fields (Sas et al, 2012). All this data is valuable for comparison with numerical results in order to validate computational models at largest scale.…”

“…The photographic monitoring method installed in field provided a graphical visualization of the strain field in the speckle area indicated in Figure 7a (Sas et al, 2012). Principal tensile strains measured at the load level of 10.8 MN are represented in Figure 7b.…”

“…Peak values reflect the major cracks developed: values of 10000-5000-1000 micro-strains appear around the cracks. A rosette placed in the same area measured around 800 micro-strains (Sas et al, 2012). The principal strains computed by the numerical model are represented by the colour map in Figure 7c.…”

Development of modelling strategies for two-way RC slabs

“…However, the few full-scale tests on real bridges show large load overcapacities compared to conventional assessment, e.g. Plos [1], Sas et al [2]. Consequently, if improved assessment methods are developed and applied, there are huge possibilities to use these reserves.…”

The Use of Advanced Optical Measurement Methods for the Mechanical Analysis of Shear Deficient Prestressed Concrete Members

“…As an optical-numerical full-field measurement method, digital image correlation (DIC) has proven to be an ideal tool for a wide range of applications, including the identification of the mechanical material behavior through inverse modeling (Cooreman et al 2007(Cooreman et al , 2008, structural health monitoring (Sas et al 2012) and the study of the deformation characteristics of a wide range of materials (Ivanov et al 2009;Van Paepegem et al 2009;Srikar et al 2016). During the testing of specimens B103-B109, the stereo-vision digital image correlation technique (3D-DIC) has been adopted to assess the displacements and deformations during the loading procedure.…”