Goran Baloević

Experimental Testing of the Effects of Fine Particles on the Properties of the Self-Compacting Lightweight Concrete

The self-compacting lightweight concrete (SCLC) is a combination of the Self compacting concrete (SCC) and the Lightweight concrete. It combines all the good properties of those two materials and is extremely convenient for the construction of buildings that require low mass and do not require high compressive strength, for example restoration works in old structures (e.g., replacement of wooden floors), prefabricated elements that require transportation, and for structures and elements where the concrete surface should be visible. In this paper the effect of the amount of fine particles on the properties of the self-compacting lightweight concrete (SCLC) in the fresh and hardened state was explored. For this purpose, sets of specimens with different combinations of admixtures of silica fume, fly ash, and filler were prepared and tested. Slump flow and flow time of fresh concrete, as well as the dynamic elastic modulus and compressive strength of hardened concrete, were measured at different ages of concrete. The processes of manufacturing and methods of testing are described, as well as the obtained results.

Effect of the joint type on the bearing capacity of a multi–drum column under static load

ABSTRACT The results of an experimental study on the effect of the joints between the blocks on the ultimate bearing capacity of a multi-drum column loaded to centric vertical force and horizontal force in the middle of its height are shown. The column is approximately 2.5 m high, with one hinge at the top and another hinge at the bottom. Four types of joints between the blocks were considered: a dry joint (column C-DJ) and joints with stone powder (column C-SPJ), lead (column C-PBJ), and epoxy (column C-EPJ). The applied vertical and horizontal forces, horizontal displacement, vertical strains, and horizontal circumferential strains in the middle of the column height, as well as shortening of the column, were measured. Under axial compression, ratios between the ultimate load bearing capacities of tested columns were C-EPJ: C-DJ: C-SPJ: C-PBJ = 1: 0.68: 0.59: 0.51. The bearing capacity of the tested columns with regard to the horizontal force depended on the level of the applied centric compression force. Columns with soft joints (C-PBJ, C-SPJ) had the largest shortening and the largest horizontal displacements for the equal forces.

Behavior of fiber reinforced mortar composites under impact load

This paper presents results of the experimental study on the behavior of plain and fiber reinforced cement mortars with different fibers under static and impact compressive load. Glass, polypropylene and carbon fibers were used in equal dosage by mass. The impact test was conducted using an impact tower with drop hammer, which represented the modification of the split-Hopkinson pressure bar system, with strain rates ranging from approximately 35 to 60 s-1. The results of the static test and impact test with two different drop heights were compared and discussed. Among other, it has been concluded that the tested fiber reinforced mortars had no greater static and impact strength compared to the plain mortar. Only their ductility was increased at both static and impact failure. Strengths and ductility of all composite specimens were similar, i.e. without the effect of fiber type. With the increase of strain rate, compressive strength is increased and ductility is decreased for all tested specimens.

Comparison of Developed Numerical Macro and Micro Masonry Models for Static and Dynamic Analysis of Masonry-infilled Steel Frames

First, the basic characteristics of macro and micro masonry models in numerical analyses of masonry structures are discussed. Afterwards, developed numerical macro and micro masonry models, intended for the nonlinear static and dynamic analysis of unreinforced and confined masonry walls, as well as of masonry-infilled frames, are briefly presented. The models are tested on previously performed experimental tests of masonry-infilled steel frame under horizontal static force and masonry-infilled steel frame on a shake-table. The precision of both models is compared. It is concluded that both numerical models can provide reliable results. However, the macro model has more advantages for wide practical application.

Stirrup effects on compressive strength and ductility of confined concrete columns

The results of experimental testing of stirrup effects on compressive strength and ductility of axially loaded confined reinforced concrete columns of rectangular cross-section are presented. Effects of different concrete strengths, different stirrup bar diameters and different stirrup spacing on columns bearing capacity and ductility have been researched.

Effect of Anisotropy of Masonry on the Behaviour of Unreinforced and Confined Masonry Walls Under Ground Motion

This paper presents the numerical test results of the effect of anisotropy on the behaviour of unreinforced and confined masonry walls under horizontal harmonic ground acceleration. Two-storey masonry walls with different lengths (3, 6, 12 m) are analysed. The wall foundations are supported on a rigid base, with possibility of lifting. A non-linear macro model of masonry is used. Cases of strong masonry (high strength and stiffness) and weak masonry (low strength and stiffness) are analysed. Different coefficients of anisotropy of masonry ca (0.2, 0.4, 0.6, 1.0) are considered. The excitation period is taken to correspond to the fundamental period of the individual elastic wall. Horizontal displacements at the top of the walls, vertical stresses in masonry and concrete at the bottom of the walls and stresses in the longitudinal bars at the bottom of the vertical ring beams are shown for each analysed case. It is concluded that the ultimate bearing capacity and deformability of walls, as well as stresses in masonry, concrete and reinforcement under dynamic excitation significantly depend on the anisotropy of masonry. It is also concluded that, with the same coefficient of anisotropy, the behaviour of masonry walls depends on its type (unreinforced, confined), height to length ratio (0.5, 1.0, 2.0), and the quality of masonry (strong, weak).

Effect of the Drum Height on the Seismic Behaviour of a Free-Standing Multidrum Column

The results of a shake-table study on the effect of the drum height on the seismic behaviour and bearing capacity of small-scale free-standing multidrum columns are presented. Columns of equal height with one, three, and six drums through their height were considered for the case of their self-weight only and for the case with an additional weight on the top of the column. The columns were exposed to a horizontal base acceleration of three accelerograms by successively increasing the maximum acceleration to their failure. The characteristic displacements and accelerations of the column were measured. It was concluded that an increase in the number of blocks in the column can significantly increase or decrease its ultimate bearing capacity, depending on the type of the applied accelerogram. It is expected that the experimental database can be useful in the validation of nonlinear numerical models for the dynamic analysis of multidrum columns.