Behaviour of functionally graded reinforced-concrete beams under cyclic loading

Tijekom zadnjih deset godina primjenjuje se slojevito mikroarmiranje kao nova metoda za proizvodnju armiranobetonskih elemenata. U radu su prikazani rezultati ispitivanja svojstava slojevito mikroarmiranih betonskih greda izloženih djelovanju cikličnog opterećenja. Za pripremu uzoraka primijenjena su čelična i polipropilenska vlakna. Betonske grede s potpunim kompozitnim djelovanjem ojačane su sa 0,5 do 2 % čeličnih vlakana, a slojevito mikroarmnirane grede sadrže 1,3 % čeličnih vlakana. Dobiveni rezultati pokazuju da se primjenom slojevitog mikroarmiranja betona povećava disipacija energije uslijed cikličkog opterećenjaOver the past decade, the functional grading has been applied as a new method for the manufacturing of reinforced-concrete elements. The objective of this investigation is to evaluate performance of the functionally graded reinforced-concrete beams exposed to cyclic loading. The steel and polypropylene fibres are used for the preparation of samples. Concrete beams with full composite action are strengthened with 0.5 to 2 % of steel fibres, and functionally graded RC beams contain 1.3 % of steel fibres. The use of the functionally graded method to reinforce concrete increases the dissipated energy due to the applied cyclic loading

Mechanical performance and post-cracking behavior of self-compacting steel-fiber reinforced eco-efficient ultra-high performance concrete

In this study the main mechanical performances of a new eco-efficient composition for ultra-high performance concrete, made with fine fly ash and low cement content, were investigated. The main tests include compressive strength, modulus of elasticity in compression, flexural strength by three and four-point bending tests and finally tensile strength through direct tensile test as well as its fresh rheology. The first-cracking strength, toughness indices and residual strength factors were evaluated by means of four-point bending test. In addition, flexural tensile strength and residual flexural tensile strength were studied through three-point bending test by quantifying energy-absorption capacity of the specimens. The results demonstrated 172 MPa and 47 GPa of compressive strength and modulus of elasticity respectively. Even with 1% vf. of micro steel fibers, noticeable post-cracking behavior including energy-absorption capacity, tensile strength and residual flexural tensile strength was observed