ABSTRACT
Due to increased requirements on the load-carrying capacity, a lot of existing reinforced concrete bridge deck slabs without shear reinforcement are insufficient according to current design codes. The decisive loads for dimensioning bridge deck slabs in transverse direction are the wheel loads of the load models. The load-bearing behaviour of one-way slabs under concentrated loads displays an intermediate case between beam-shear and punching. In current design approaches for calculating the shear and punching capacity of slabs, a shear strength per unit length is multiplied by an effective width for one-way shear and a control perimeter for punching-shear, respectively. However, the shear or punching behaviour of one-way slabs under concentrated loads cannot be accurately covered by shear and punching shear design rules. These rules were mostly validated by shear tests on beams and by the punching behaviour of two-way slabs, respectively.
In order to study the effective width contributing to the shear resistance, extensive experimental investigations have been conducted at the Institute of Structural Concrete at RWTH Aachen University, Germany. Slab strips with a width of 0.5 m and wide slabs with a width of up to 3.5 m were tested under concentrated loads (Figure 1). In case of the 0.5 m wide slab strips the full width was activated indicating a beam-like bearing behaviour. In contrast, the width of the 3.5 m wide slabs was larger than the activated width. Comparing the results of 35 shear tests on wide slabs and slab strips, the effective width for shear is derived and presented in the paper. In addition, the influences of the static system (cantilevers, simply supported single span slabs and slabs with one clamped end), the shear-span-to-depth ratio (varying between 2.9 and 5.4) and the transverse reinforcement ratio on the effective width for shear are evaluated based on the crack development, the load-deflection behaviour and the distribution of the support reaction. An effective width b sup based on the distribution of the support reactions is determined according to Figure 2 by substituting the actual distribution of support reactions by an equivalent constant one. The test results will be used to develop an appropriate approach for the shear capacity of slabs under concentrated loads. This new approach aims at ensuring both an appropriate assessment of existing bridge deck slabs as well as a safe and economic design of new structures. Testing frame with slabs with <italic>b</italic> = 1.5 m and 2.5 m. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig324_1.jpg"/> Effective width <italic>b</italic> <sub>sup</sub> based on the distribution of the support reactions. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig324_2.tif"/>
