Estefanía Cuenca

Shear Behavior of Self-Compacting Concrete and Fiber-Reinforced Concrete Push-Off Specimens

The shear behavior of reinforced “Z”-shaped push-off specimens made with self-compacting concrete (SCC) and self-compacting fiber-reinforced concrete (SCFRC) was analyzed by means of experimental tests. Testing consisted of two phases. Firstly, specimens were precracked subjected to linear load along the shear plane. During this first phase three precracked levels were distinguished (without precrack, thin and thick precrack). Then, precracked specimens were tested under direct shear load. The shear behavior along the shear plane was analyzed by means of the crack opening and shear displacement versus shear load process. Variables were: the type of concrete (SCC, or SCFRC with different fibers contents: 40 kg/m3 or 60 kg/m3), the transversal reinforcement (TR) and the precrack width. The analysis was specially focused on the study of aggregate interlocking. The failure occurrence is better controlled thanks to the presence of fibers, the shear behavior is more ductile.

Recommendations for Future Research

A new push-off test should be performed subject to direct shear loads, with good control of crack width, in order to improve the response of the test in determining aggregate interlock in different concrete matrixes, at different levels of compressive strength and with different kinds of steel fibers.

Experimental Tests on Parameters Influencing on Shear

This chapter develops and explains the criteria for obtaining self-compacting fiber reinforced concrete (SCFRC) and the analysis of its production quality continuity in a precast industry and its ulterior application to produce prestressed concrete beams to minimize traditional transverse rebars.

Objectives and Research Significance

The main objective of this Ph.D. thesis is to study the different parameters affecting the shear behavior of concrete reinforced with steel fibers. It also aims to determine the influence of the different parameters involved and examine certain design Codes, with particular reference to the role of fiber reinforcement.

Experimental Tests to Study the Influence on the Shear Behavior of Fibers of Different Characteristics

Steel fiber reinforced concrete (SFRC) is a composite material that is characterized by an enhanced post-cracking behavior due to the capacity of fibers to bridge the crack faces.

Experimental Tests on Fibers Influence on the Size Effect on Shear

In this chapter it will be discussed the possibility of steel fibers to mitigate the size effect in large beams. For that, an experimental program consisting in 9 beams with h = 500, 1,000 and 1,500 mm, made with three types of concretes with 0, 50 and 75 kg/m3 of fibers was done. The beams were tested with a/d = 3 for all cases. The concrete was manufactured in a concrete plant of Italcementi Group, while the tests were carried entirely at the laboratory “Pietro Pisa” of the University of Brescia.

Experimental Tests on Hollow Core Slabs Made with FRC

Hollow Core Slabs (HCS) are usually precast by extrusion and it is not easy to place stirrups; thus, it is difficult to guarantee shear resistance in some cases.

Shear Database and Study of the Parameters Influencing Shear Behavior

After thorough review of the literature on structural elements with shear failure, and after conducting several experimental programs whose values were compared later with the theoretical values obtained with the three selected Design Codes to calculate shear in elements reinforced with fibers, it was found that it would be useful and also necessary to build a large database of elements failing in shear in order to have a large number of cases that allow to better evaluate resisting phenomena and the validity of building Codes. For this reason, this chapter shows the analysis of that database.