Thursday, March 9, 2017

Papers at SEMC 2016

This year, I was author and co-author of three papers at SEMC 2016, the conference on Structural Engineering, Mechanics and Computation in Cape Town, South Africa. While I did not have the chance to travel, my students Mr. Valdivieso and Mr. Mejia traveled to present their thesis work, and Dr. van der Veen traveled to present our co-authored paper.

The abstract of mr. Mejia's paper is:

Throughout history invasive methods for analyzing deflections and deformations have been used in concrete structures at the laboratory, but the advancement of technology has allowed the development of new non-invasive alternative methods such as digital image correlation (DIC). With this technique, it is possible to obtain information about the deflections, strains and strain fields in a structure. The current study consists of performing a flexural test on plain concrete beams and concrete arches reinforced with FRP rein-forcement. All tests were recorded with a cheap, small camera, then transferred into a series of images in or-der to apply the digital image correlation technique. The analysis with DIC results in the displacements, strains and strain fields of the surface under analysis. Finally, the percentage of error between the displace-ment derived from the DIC technique and the displacement measured by Linear Variable Differential Trans-formers (LVDTs) is calculated. In conclusion, the study shows that it was not possible to reach accuracy on the values of deflections and strains by the applied method and that a higher-speed camera is necessary to capture the moment of failure.

The abstract of mr. Valdivieso's paper is:

A large number of existing bridges in Europe and North-America are reaching the end of their devised service life. Therefore, it is necessary to improve the methods of assessment for existing bridges. One method, suitable for existing reinforced concrete slab bridges, is the Modified Bond Model. This method, however, currently only takes the effect of torsion for loads close to the edge into account in a simplified manner. In this study, finite element models are created of a slabs with two supports, three concentrated (pre-stressing) loads and a distributed load, representing a truck wheel print. The load is varied along the longitu-dinal and transverse directions of the slab to find the bending moments (mx and my) and torsional moments (mxy). The results is an expression for the effect of torsion in slabs, which can be used with the Modified Bond Model for assessment and design of slab bridges.

The abstract of the paper of which I am first author is:

For the assessment of existing structures and the design of new structures, it is important to have a good understanding of the flow of forces, here applied to reinforced concrete solid slabs. Two analyti-cal methods are used: finite element models with 3D solid elements and a plasticity-based model that is suita-ble for hand calculations, the Modified Bond Model. The slabs that are modeled are half-scale models of rein-forced concrete solid slab bridges. As the Eurocode live load model prescribes more heavily loaded trucks in the first lane, the load model is asymmetric. For the finite element models, limited use is made of the redistri-bution capacity of the slab. For the Modified Bond Model, the influence of torsion and the edge effect need to be taken into account. The results of these studies improve the current state-of-the-art for analysis and design of reinforced concrete slabs.

Here are the slides of my paper:

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