19 research outputs found
Comparison between the environmental performance of buildings made of reinforced concrete and timber
In order to reduce the environmental impact of the construction industry, the case of natural material (such as timber) is pursued. However, is the use of low-impact materials sufficient to decrease the overall environmental impact of a building? The answer is not trivial, because there are many parameters that affect sustainability, in addition to the unitary environmental impact of the building materials. Through this article, an evaluation of the total CO2 emission in buildings made of reinforced concrete and CLT panels is carried out. The entire life cycle (LCA) of the materials is considered, as well as the CO2 emissions derived from heating and chilling. The relationship between CO2 emissions and building height is also taken into account along with weather conditions.The structures and envelopes of a three - storey family house and of a multi-storey residential building are designed from a structural and thermal point of view, respectively. In order to consider the climatic effects, three locations with very different weather conditions are assumed (i.e. Catania, Turin, Oslo). The carbon footprint of three different structures is considered, namely RC frame made with cast-in-situ structural elements, precast RC panels and timber CLT structure.The quantification of the carbon footprint allows to notice how the overall structural and thermal performances, including the thermal mass, affect the environment performance
New eco-mechanical index for concrete structures
A new eco-mechanical index (EMI) has been introduced with the aim of quantifying the environmental impact
of concrete structures. From a general point of view, this indicator represents the amount of carbon dioxide
released to produce certain mixtures of pre-established strength and ductility. Both for normal strength and high
strength concrete, with and without steel fibers, these mechanical properties are summarised by the work of
fracture under tensile actions. If also structural durability has to be taken into account, the maximum crack width
of reinforced concrete structures must be computed. This is possible by using a tension-stiffening model, here
applied to reinforced concrete elements in tension. However, with or without the evaluation of crack width, the
concrete with the best EMI releases the highest fracture energy. For this reason, the work of fracture represents
also a durability parameter, and therefore it can be used to tailor cement-based composites with the highest
strength, ductility, and durability, and the lowest environmental impact
Multiple cracking and strain hardening in fiber-reinforced concrete under uniaxial tension
Fiber-reinforced concrete (FRC) showing strain hardening after cracking is commonly defined as High Performance Fiber Reinforced Cementitious Composite (HPFRCC). In the post cracking stage, several cracks develop before complete failure,which occurs when tensile strains localize in one of the formed cracks. As iswell known,multiple cracking and strain hardening can be achieved in cement-based specimens subjected to uniaxial tension by increasing the volume fraction of steel fibers with hooked ends, or by using plastic fibers with and
without steel fibers, or bymeans of high bond steel fibers (e.g., twisted fibers or cords). To better understandwhy,
in such situations, highmechanical performances are obtained, an analyticalmodel is herein proposed. It is based
on a cohesive interface analysis,which has been largely adopted to investigate themechanical response of FRC or the snubbing effects produced by inclined fibers, but not the condition ofmultiple cracking and strain hardening ofHPFRCC. Through this approach, all the phenomena that affect the post-cracking response of FRC are evidenced, such as the nonlinear fracture mechanics of the matrix, the bond–slip behaviour between fibers andmatrix, and the elastic response of both materials. The model, capable of predicting the average distance between cracks as
measured in some experimental campaigns, leads to a new design criterion for HPFRCC and can eventually be used to enhance the performances of cement-based composites
Optimal calculation of reinforcement in tunnel segmental lining
The capability of steel fiber-reinforced concrete to carry tensile stresses, also in the presence of
wide cracks, allows designers to reduce the area of steel reinforcing bars. This aspect has been taken into
account in a new design procedure of concrete segmental linings, capable of computing the behavior of ordinary
reinforced cross-sections subjected to bending moment and normal forces. Accordingly, a practical formula to
quantify the possible reduction of steel rebars in fiber-reinforced concrete is proposed in the present paper. This
formula, which is in accordance with code rule requirements, has been used to optimize the reinforcement of
prefabricated concrete linings
Evaluation of minimum reinforcement ratio in FRC members and application to tunnel linings
Steel fiber-reinforced self-compacting concrete subjected to concentrated loads
To model the behavior of precast segmental tunnel linings under thrust jack loading, cylindrical concrete columns, subjected to concentrated loads, are investigated. Specifically, uniaxial compressive tests have been performed on specimens made with self-compacting concrete and reinforced with two different amounts of steel fibers (0, 30 kg/m3, respectively). In addition, to measure concrete properties, three point bending tests have been carried out in accordance with code rules. As a result, not only the fracture toughness of concrete in compression is improved, but also the ultimate and the maximum splitting loads are remarkably increased by the presence of long fibers. Accordingly, a new formulation of the classical Leonhardt's approach is eventually proposed. Finally, based on the results of the present research, it seems reasonable to replace reinforced concrete with SFRSCC in structures subjected to high concentrated loads