Carlos Ribas

Shear-flexural strength mechanical model for the design and assessment of reinforced concrete beams

A conceptual model for the prediction of the shear-flexural strength of slender reinforced concrete beams with and without transverse reinforcement is presented. The model incorporates the shear transferred by the un-cracked concrete chord, along the cracks length, by the stirrups, if they are, and, in that case by the longitudinal reinforcement. After the development of the first branch of the critical shear crack, failure is considered to occur when the stresses at any point of the concrete compression chord reach the assumed biaxial stress failure envelope. A physical explanation is provided for the evolution of the shear transfer mechanisms, and the contribution of each one at ultimate limit state is formulated accordingly. Simple equations are derived for shear strength verification and for designing transverse reinforcement. The method is validated by comparing its predictions with the results of 1131 shear tests, obtaining very good results in terms of mean value and coefficient of variation. Because of its accuracy, simplicity and theoretical consistency, the proposed method is considered to be very useful for the practical design and assessment of concrete structures subjected to combined shear and bending.

Pilot Experiences in the Application of Shape Memory Alloys in Structural Concrete

The interesting properties of shape memory alloys (SMA) have increased the investigation, study, and development of possible applications of these alloys in the field of civil engineering. This paper presents a state of the knowledge of existing studies and applications of SMAs in distinguishing their properties: superelasticity, shape memory, and damping. The main objective of this paper is to discuss the advantages of concrete structures and improvements in their behavior when using SMAs and to collect critical unsolved aspects of SMAs that could be a starting point for the development of future research in this field.

Saving potential for embodied energy and CO2 emissions from building elements: A case study

In this article, the authors estimated the saving potentials in the embodied energy and CO2 emissions, which could be achieved through a replacement of the most energy-intensive elements in a large building. The results showed that 75% of the embodied energy came from only a small group of the building components, that reductions from 14% to 29% in embodied energy values were possible with simple replacements and that between 1770 and 4160 tonnes of CO2 could be avoided to be emitted to the atmosphere, with budget increases lower than 8%.