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SažetakPosljednjih se godina za pojačanja konstrukcija istražuju tkaninom armirani mortovi (TRM). To su kompoziti koji se sastoje od vlakana (staklenih, ugljičnih, bazaltnih, PBO) i anorganske (cementne) matrice. Nastali su iz potrebe za rješavanjem nedostataka epoksidne matrice kod vlaknima armiranih polimera (FRP-a). Anorganska matrica ima veći toplinski kapacitet, a ponašanje elementa u vlaku nije linearno elastično. Snopovi vlakana su formirani u mreže kako bi se ostvarila povezanost s matricom. Provedeno je više istraživanja pojačanja armiranobetonskih i zidanih konstrukcija, a u ovom radu prikazana su pojačanja armiranobetonskih (AB) ploča, greda i stupova. Istaknuti su parametri koji utječu na učinkovitost kompozitnog djelovanja, a time i učinkovitost pojačanja te ponašanje pojačanih elemenata. Ključne riječi: TRM, pojačanja, AB, vlakna, mort, tkanina Textile reinforced mortars (TRM) as strengthening technique for reinforced concrete structures AbstractIn the last years, textile reinforced mortars (TRM) have been studied for the strengthening of structures. TRM are composites made of fibres (glass, carbon, basalt, PBO) embedded in inorganic (cementitious) matrix. They have been developed due to fibre reinforced polymers (FRP) epoxy matrix´s disadvantages. Inorganic matrix has higher thermal capacity and tensile behavior of material is non linear elastic. Fibre rovings form fabric grids in order to achieve the bond with the matrix through penetration of mortar through the fabric. Several studies have been carried out on the strengthening of reinforced concrete and masonry structures. Strengthening of reinforced concrete (RC) slabs, beams and columns is presented in this paper. Parameters that affect the effectiveness of composite action, and thus the effectiveness of strengthened elements are highlighted.

According to the Eurocode 3 Part 1-2 (EN1993-1-2) (CEN 2005b), it is possible for structural engineers to consider physical based thermal actions and to do performance based design instead of using prescriptive rules based on nominal fire curves. However, some uncertainties remain in the use of such approaches. This study focus on the clarification of the use of the simplified design methods to assess the fire resistance of unbraced steel frames exposed to fire. On the other hand, a recent study (Couto et al. 2013) suggests the use of a buckling coefficient of 1.0 for all the columns except those belonging to the first storey of a pinned framed where 2.0 should be taken instead and it is unclear if the consideration of such values for the buckling lengths is adequate when using performance based designs. In this study, a comparison is made between simple and advanced calculation models and it is demonstrated that the simple design methods, using the suggested buckling coefficients to calculate the fire resistance of the frames are safe sided when compared to the use of advanced calculations using the finite element method (FEM).

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