Shear design of short-span beams

Abstract

Eurocode 2 presents two alternative methods for accounting for arching action in beams. The simplest option is to reduce the component of shear force owing to loads applied within 2d of the support by the multiple av/2d (where av is the clear shear span and d is the effective depth). Eurocode 2 also allows short-span beams to be designed with the strut-and-tie method (STM), raising the question of which method to use. This paper presents a simple strut-and-tie model for short-span beams. The stress fields used in the STM are shown to be broadly consistent with those calculated with non-linear finite-element analysis. The STM is shown to give good predictions of shear strength, particularly when the concrete strength is calculated in accordance with the recommendations of Collins and Mitchell. The accuracy of the simplified design method in Eurocode 2 is shown to be highly dependent on the stirrup index. The paper also presents data from eight beams tested by the authors which show that aggregate fracture has little if any influence on the shear strength of short-span beams.