Damage Mechanics of Dual Systems

Damage Mechanics of Dual Systems

DOI: 10.4018/978-1-4666-6379-4.ch011

Abstract

This chapter begins with the presentation of some experimental results on RC specimens using a special technique called “digital image correlation.” Then, it describes a damage model for RC walls. Next, the model is generalized to include elements with any aspect ratio; finally, the analysis of dual system is described and some numerical simulations are presented. Notice that Section 3.4 described the elastic behavior of dual systems; in section 7.3 that model was extended to include plastic deformations. The goal of this chapter is to generalize that model, including cracking propagation described by the Griffith criterion or its modified version.
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11.1 Experimental Analysis Of Rc Elements Of Various Aspect Ratios

Dual systems are reinforced concrete structures composed by slender elements and walls. These systems are often used as a good structural alternative for buildings and facilities in earthquake-prone areas. Even in framed structures, short or intermediate columns and beams and, in general, RC elements of any aspect ratio may appear as a result of inadequate disposition of masonry walls or other non-structural components (see Figure 1).

Figure 1.

Failure of a short column in a RC structure (Courtesy of Dr. Jürg Hammer, DRM Disaster Risk Management Switzerland SA)

11.1 Hammer, J. (2001). Retrieved February 28, 2014 from http://www.drmonline.net/drmlibrary/peru_photos.htm DRM Disaster Risk Management Switzerland SA.

11.1.1 Digital Image Correlation

In the digital image correlation technique (DIC), the surface of the specimen to be tested is prepared in order to create a random texture. A first digital photo of reference is taken before the test (see Figure 2a). Next, further pictures are taking during the experiment while the chosen external forces are applied (see Figure 2b). A computer program analyzes first the reference digital image; the software divides this photo in small portions that may be imagined as small “finger prints”; subsequently, it identifies each of them. Then, the program processes the following picture, looking for the same “finger prints” and determines their new position in the photo. This procedure gives the average displacement vector of each specific portion. The same procedure is followed sequentially with each digital photograph of the test.

Figure 2.

Representation of a displacement measurement with DIC a) Reference picture b) Deformed configuration

With the displacements, the program computes the strain field using the conventional expressions. Cracks in the concrete appear as concentrations of strains.

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