The shear design of reinforced concrete (RC) slabs under concentrated loads calls for the definition of an effective width, which can be used to assess the slab's shear capacity. However, currently the shear strength and effective shear width of oneway RC slabs is only poorly investigated. Therefore, this paper presents the results of 34 shear tests on RC slabs and slab strips without shear reinforcement. To analyze the effective shear width, 0.5 m wide slab strips and slabs with a width of up to 3.5 m were tested under concentrated loads with different shear-span-to-depth ratios (varying between 1.4 and 5.4). While the slab strips were activated over their full width (beam action), the shear capacity of the wide slabs was significantly influenced by their effective shear width. To also clarify the impact of the structural system and the support conditions, the slabs were clamped at one end with different degrees of rotational restraint. Beginning with simply supported, single-span slabs, the rotational restraint was stepwise increased to 100% representing a fully clamped support. Further investigated parameters were the transverse reinforcement ratio and the arrangement of multiple loads. The resulting shear capacities of all tests are compared with code provisions of Eurocode 2. The results illustrate remarkable differences in the shear behavior of wide slabs and slab strips with predominant beam action. Besides the influence of the effective shear width, this paper analyzes the direct load transfer to supports via strut mechanisms (arching action).
K E Y W O R D Sarching action, effective shear width, experimental investigations, reinforced concrete slabs, rotational restraint, shear
VeranlassungBei der Umstellung auf die neue Normengeneration verminderte sich der rechnerische Querkraftwiderstand von Bauteilen ohne Querkraftbewehrung bei gleichzeitig er- Experimental investigations on the shear-bearing behaviour of bridge deck cantilever slabs under wheel loads The calculated shear capacity according to current design rules of a large number of existing concrete bridge deck slabs without shear reinforcement is not sufficient [1]. However, the present design rules for the shear capacity of members without shear reinforcement were principally developed based on shear tests on simply supported single span beams. Since until now, only few tests on the shear capacity of cantilever slabs under concentrated loads have been conducted [3,4], the shear-bearing behaviour of cantilever slabs has been analysed within a research programme funded by the Federal Highway Research Institute of Germany (BASt) [5]. Besides the effective width for shear, the moment-shear relation and the influence of an inclined compression zone were experimentally investigated.
Experimental investigations on the effective width for shear of single span bridge deck slabsThe requirements for the load-carrying capacity of bridges have increased significantly due to rising traffic loads in the last decades [1]. Furthermore, the design rules of the German codes have changed leading to smaller calculated shear capacities of reinforced concrete members without shear reinforcement [2][3][4][5]. Therefore, the calculated shear capacity of a large number of existing concrete bridge deck slabs without shear reinforcement is not sufficient. For the above reasons, the shear-bearing behaviour of slabs has been investigated within a research programme funded by the Federal Highway Research Institute of Germany (BASt) [6,7]. The paper presents the results of the experimental investigations on the effective width for shear of simply supported single span slabs without shear reinforcement.
Veranlassung
BERICHTBild 1 Altersstruktur der Brücken im Zuge der Bundesfernstraßen bezogen auf die Brückenfläche des Bundesfernstraßennetzes [%] nach [2] Age distribution of bridges of German federal highways related to bridge deck area of the national road network [%] according to [2]
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