Development of material to be used for bearing pad in precast concrete connections
Mounir Khalil El Debs, University of Sao Paulo at Sao Carlos, Brazil
Aline da Silva Ramos Barboza, Federal University of Alagoas, Brazil
Anamaria Malachini Miotto, Tuiuti University of Parana, Brazil
Bearing pads are used in precast concrete connections to provide a more uniform distribution of contact stresses over the bearing areas and to allow relative movements between precast concrete elements, in order to prevent cracking at the connection area. This paper presents the study of an alternative material made with styrene-butadiene latex modified on Portland cement mortar, polymeric fibres, and, eventually, lightweight aggregate (vermiculite). The developed material showed a good compression strength and low elasticity modulus. These characteristics make it suitable for use as bearing pads in precast concrete connections, such as beam-to-column connections or wall-to-wall connections. The paper shows the main characteristics of this material and the application and tests on: (a) beam-to-column connections and (b) samples that reproduce a wall-to-wall connection.
Size-effect experiments on concrete in compression
Stefan L. Burtscher, University of Technology, Vienna
Johann Kollegger, University of Technology, Vienna
It is well known from literature that heterogeneous granular materials exhibit a size effect under tensile loading. Thus, the strength determined in experiments is not a material property. Some experiments have been performed regarding the size effect in tension whereas very few experiments have been performed in compression. However, compressive loading of concrete is more important because concrete is applied in structural systems to carry load in compression and not in tension. Furthermore, a compressive failure in a load-carrying member is more brittle, and in most cases more dangerous, than a tensile failure. Experimental investigations on the size effect are therefore needed. Experiments from literature on column-like specimens under compressive loading were performed up to a size range of 1:4. The size range of a series of geometrically equal specimens is given by the amplification factor of a characteristic dimension from the smallest to the largest specimen size. Obviously large size ranges are advantageous for experimental studies on size effect. The largest size range (1:16) of experiments on concrete under compressive loading carried out so far will be presented in this paper. This series was performed in one of the largest testing facilities available. A size effect on nominal strength was detected. The results are compared with the two most common size-effect laws.