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The paper compares the following methods for analysis of composite steel-concrete beams: the “exact” analysis method, simplified method, effective modulus method and the method proposed by Eurocode 4 design code. The exact analysis method is based on the application of linear integral operators. Simplified analysis is derived from the exact method and adopts the assumption that generalized displacements change linearly with the concrete creep function. Effective modulus method and the method proposed by the Eurocode 4 design code are algebraic methods, widely used in practice. The results obtained using the mentioned four methods are compared on one example.

Different analytical methods, with different levels of approximations and accuracy, are available for analysis of continuous composite steel-concrete beams. The Eurocode 4 recommends few simple methods for calculation of creep, shrinkage, cracking of concrete and shear lag effects that are explained in the paper. Through the numerical examples of four continuous composite steel-concrete beams, the proposed methods of analyses are evaluated and compared. Practical recommendations for analysis of this type of girders are formulated. Za analizu spregnutih kontinualnih nosača od čelika i betona postoje različite analitičke metode, različitog stepena tačnosti. Evrokod 4 dozvoljava i preporučuje nekoliko jednostavnih metoda kojima se u proračun uvode nelinearni efekti kao što su skupljanje i tečenje betona, ispicalost betonske ploče i shear-lag efekat, i one su objašnjene u radu. Kroz numeričku analizu četiri spregnuta kontinualna nosača ove metode su upoređene i date su praktične preporuke za analizu ove grupe nosača.

In this paper, the analysis of longitudinal shear in concrete slab, according to Eurocode 4 (EN 1994-1-1:2004), is shown. The potential surfaces of shear failure in solid and composite slab are analyzed. For each potential surface of shear failure, the corresponding length is defined. The transverse reinforcement should be determined from the condition that, for any potential surface of shear failure, the design longitudinal shear per unit length (shear flow) is not greater than the longitudinal shear resistance of the slab per unit length. The longitudinal shear resistance of concrete slab per unit length should be determined according to EN 1992-1-1. The rules for transverse reinforcement are based on a truss analogy, i.e. the concrete slab is considered as a truss system that has compressed concrete struts and tensioned reinforcement (chords).The failure occurs when either the reinforcement yields or the concrete struts fail in compression. The transverse reinforcement in the concrete slab transfers the shear stresses from studs (shear connectors) and ensures that the premature failure of the slab will not occur. U radu se prikazuje proračun podužnog smicanja u betonskoj ploči prema Evrokodu 4 (EN 1994-1-1:2004). Analiziraju se potencijalne površine loma usled podužnog smicanja, u punoj i spregnutoj betonskoj ploči. Za svaku potencijalnu površinu loma definiše se odgovarajuća dužina površine smicanja. Proračun nosivosti pri podužnom smicanju se zasniva na uslovu da proračunski podužni napon smicanja, bilo koje potencijalne površine loma usled podužnog smicanja u okviru ploče, ne bude veći od proračunske nosivosti pri podužnom smicanju. Proračunska nosivost pri podužnom smicanju betonske ploče se određuje u skladu sa EN 1992-1-1. Ovaj proračun se zasniva na modelu rešetke, tj. betonska ploča se posmatra kao sistem kosih (dijagonalnih) pritisnutih betonskih štapova kombinovan sa zategama koje predstavlja poprečna zategnuta armatura. Gubitak nosivosti (lom) betonske ploče nastaje ako dođe do tečenja (loma) u armaturi ili ako dođe do drobljenja betona u pritisnutim štapovima. U betonskoj ploči se obezbeđuje adekvatna površina poprečne armature koja će da prenese smičuće napone iz moždanika i obezbedi da ne dođe do prevremenog loma u betonu.