Experimental and numerical studies of continuous composite beams taking into consideration slab cracking

Abstract

IntroductionSpecial requirements with regard to the theory of composite structures and their creative shaping make them one of the most interesting solutions for load-carrying structures in the construction technology. The constituent parts of the cross section are made of materials with different Young's moduli, which interact with each other through the use of fasteners. These elements are joined to maximise both their strength properties and operating characteristics with respect to their location within the feature.The greatest benefits are currently visible in the application of steel-concrete composite structures [24]. These are mainly used in bridge construction but are also used in other areas of the construction industry, especially in the industrial construction [16].The importance of the issue of cracking in the context of continuous composite structures is still a topic of discussion. Although the structure safety is not compromised in any way, its operating lifespan is significantly affected. Non-structural cracks can cause damage to insulation and -in the long -cause corrosion of the reinforcement, as well. Therefore, it must be remembered that the operating lifespan of the structure is one of the basic assumptions in the design process and it significantly affects the adopted design solutions and materials [26]. The feature's operating lifespan is maintained when the structure fulfils its function within a given time both for its load-bearing capacity (ultimate limit states) and serviceability (limit states related to the reduction of cracks, stresses and deflections). The correct structure design ensures that it is fit for purpose for at least the period of expected operating lifespan. The requirements for the bridge structure operating lifespan are particularly high, though. In accordance with [26], bridges are classified as the S5 design category (class), which means the approximate design lifetime of at least 100 years.Nowadays, in order to meet the increasingly stringent operating lifespan criteria, the design phase for composite bridges should take into account non-structural concrete cracking and the change of its stiffness between the cracks Eksploatacja i NiEzawodNosc -MaiNtENaNcE aNd REliability Vol.18, No. 4, 2016 579 sciENcE aNd tEchNology 579[28] in the ultimate limit state and serviceability limit state. Concrete cracking affects the stiffness of the composite section and can cause an overload of the steel section. The change in the stiffness causes redistribution of excessive bending moments along the length of the continuous beam. The problem of the behaviour of the composite structure with the cracked concrete slab is complicated and not fully explored. For this reason, the stiffness of the concrete in tension in often overlooked in the design of civil engineering structures. This approach leads to an irrational assessment of the load-bearing capacity and serviceability of the composite structure, which causes a reduction in the lifetime of the feature [36].This problem also occur...

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