Costantino Menna

Application-Oriented Chemical Optimization of a Metakaolin Based Geopolymer

In this study the development of a metakaolin based geopolymeric mortar to be used as bonding matrix for external strengthening of reinforced concrete beams is reported. Four geopolymer formulations have been obtained by varying the composition of the activating solution in terms of SiO2/Na2O ratio. The obtained samples have been characterized from a structural, microstructural and mechanical point of view. The differences in structure and microstructure have been correlated to the mechanical properties. A major issue of drying shrinkage has been encountered in the high Si/Al ratio samples. In the light of the characterization results, the optimal geopolymer composition was then applied to fasten steel fibers to reinforced concrete beams. The mechanical behavior of the strengthened reinforced beams was evaluated by four-points bending tests, which were performed also on reinforced concrete beams as they are for comparison. The preliminary results of the bending tests point out an excellent behavior of the geopolymeric mixture tested, with the failure load of the reinforced beams roughly twice that of the control beam.

LCA-based study on structural retrofit options for masonry buildings

PurposeOver the last decade, the rehabilitation/renovation of existing buildings has increasingly attracted the attention of scientific community. Many studies focus intensely on the mechanical and energy performance of retrofitted/renovated existing structures, while few works address the environmental impact of such operations. In the present study, the environmental impact of typical retrofit operations, referred to masonry structures, is assessed. In particular, four different structural options are investigated: local replacement of damaged masonry, mortar injection, steel chain installation, and grid-reinforced mortar application. Each different option is analyzed with reference to proper normalized quantities. Thus, the results of this analysis can be used to compute the environmental impact of real large-scale retrofit operations, once the amount/extension of them is defined in the design stage. The final purpose is to give to designers the opportunity to monitor the environmental impact of different retrofit strategies and, once structural requirements are satisfied, identify for each real case the most suitable retrofit option.MethodsThe environmental impact of the structural retrofit options is assessed by means of a life-cycle assessment (LCA) approach. A cradle to grave system boundary is considered for each retrofit process. The results of the environmental analysis are presented according to the data format of the Environmental Product Declaration (EPD) standard. Indeed, the environmental outcomes are expressed through six impact categories: global warming, ozone depletion, eutrophication, acidification, photochemical oxidation, and nonrenewable energy.Results and discussionFor each retrofit option, the interpretation analysis is conducted in order to define which element, material, or process mainly influenced the LCA results. In addition, the results revealed that the recycling of waste materials provides environmental benefits in all the categories of the LCA outcomes. It is also pointed out that a comparison between the four investigated options would be meaningful only once the exact amount of each operation is defined for a specific retrofit case.ConclusionsThis paper provides a systematic approach and environmental data to drive the selection and identification of structural retrofit options for existing buildings, in terms of sustainability performance. The final aim of this work is also to provide researchers and practitioners, with a better understanding of the sustainability aspects of retrofit operations. In fact, the environmental impacts of the retrofit options here investigated can be used for future research/practical activities, to monitor and control the environmental impact of structural retrofit operations of existing masonry buildings.

Applications of Shape Memory Alloys in Structural Engineering

Shape memory alloys (SMAs) have physical and mechanical features that make them successful candidates for use in structural engineering applications. Primarily, SMAs play a key role toward the development and implementation of smart materials/devices, which can be integrated into structures to provide functions such as sensing, energy dissipation, actuation, monitoring, self-adapting, and healing of structures. Other excellent properties of SMAs can be exploited in civil engineering applications, such as good fatigue and corrosion resistance, large damping capacity, and good versatility in terms of their many possible shapes and configurations. This chapter discusses the variety of SMA applications in structural engineering based on the application domain.

Effect of nanofiller length and orientation distributions on Mode I fracture toughness of unidirectional fiber composites

Although several experiments demonstrate a statistical variability of length and orientation of nanofillers in composites, a limited number of analytical studies include these effects in the prediction of fracture energy, particularly in composites containing micro-sized continuous fibers together with nano-sized fillers such as carbon nanotubes. In this investigation, we model the Mode I interlaminar fracture toughness of unidirectional fiber composites containing carbon nanotubes with known length and orientation distributions. A micromechanical model, based on an analytical framework developed for “classical” short fiber composites, is presented to quantify the enhancement of fracture toughness due to either carbon nanotube pullout from the matrix or carbon nanotube fracture. The results show remarkable differences compared to the models that utilize a unique (average) carbon nanotube length value, especially with regard to maximum achievable energy enhancement, depending on mean length and on interfacial shear strength between carbon nanotubes and matrix. Some key characteristics of the carbon nanotube statistical length distribution are also analyzed along with the limit of mean carbon nanotube length between the two competing mechanisms of toughening. The analytical framework is also supported by Mode I fracture toughness experiments conducted on nanofilled S2-glass fiber/epoxy laminated composites. The inclusion of experimentally determined distributions of carbon nanotube lengths in the presented model led to good estimations of the effect of carbon nanotubes on the Mode I interlaminar fracture toughness. Comparable results were obtained for carbon nanofibers, as well.

An Embedded Wireless Sensor Network with Wireless Power Transmission Capability for the Structural Health Monitoring of Reinforced Concrete Structures

Maintenance strategies based on structural health monitoring can provide effective support in the optimization of scheduled repair of existing structures, thus enabling their lifetime to be extended. With specific regard to reinforced concrete (RC) structures, the state of the art seems to still be lacking an efficient and cost-effective technique capable of monitoring material properties continuously over the lifetime of a structure. Current solutions can typically only measure the required mechanical variables in an indirect, but economic, manner, or directly, but expensively. Moreover, most of the proposed solutions can only be implemented by means of manual activation, making the monitoring very inefficient and then poorly supported. This paper proposes a structural health monitoring system based on a wireless sensor network (WSN) that enables the automatic monitoring of a complete structure. The network includes wireless distributed sensors embedded in the structure itself, and follows the monitoring-based maintenance (MBM) approach, with its ABCDE paradigm, namely: accuracy, benefit, compactness, durability, and easiness of operations. The system is structured in a node level and has a network architecture that enables all the node data to converge in a central unit. Human control is completely unnecessary until the periodic evaluation of the collected data. Several tests are conducted in order to characterize the system from a metrological point of view and assess its performance and effectiveness in real RC conditions.

Methodology for Life-Cycle Sustainability Assessment of Building Structures

This study aims to define a methodological framework that could guide construction community stakeholders in conducting environmental sustainability comparisons among building systems at the design stage. The study proceeds on the basis that the design of new structures starts with specific requirements, including national technical standards. An application of the proposed framework for the comparative life-cycle assessment (LCA) concerning a residential building is presented; three different structural materials are compared—namely, reinforced concrete (RC), steel, and wood. Starting with functional, architectural, and structural requirements, the building is designed and verified to take into account how structural solutions change depending on each building material. A cradle-to-grave LCA study is conducted for the three alternative structures using SimaPro software; both IMPACT2002+ and EPD2008 methodologies are used to quantify environmental impacts.

Fabric-Reinforced Cementitious Matrix (FRCM) composites

Abstract An innovative class of fiber-reinforced composites is represented by Fabric-Reinforced Cementitious Matrix (FRCM) systems, which are becoming broadly used as externally bonded strengthening of both concrete and masonry constructions. The key feature of FRCM systems is the replacement of a classical polymeric matrix with an inorganic matrix, making them particularly effective in retrofitting of masonry structures given their chemical, physical, and mechanical compatibility to the substrate. Several experimental investigations have been carried out so far, both at the scale of the composite material and of structural components, reaching an adequate level of knowledge for structural engineering applications. In this chapter, we provide a comprehensive review on the mechanical behavior of FRCM composites and their beneficial effects on the performance of retrofitted masonry walls subjected to gravity loads and earthquake actions. Important issues related to the experimental material characterization, mechanical modeling, and effectiveness of FRCM strengthening systems are highlighted.

An innovative embedded wireless sensor network system for the structural health monitoring of RC structures

Maintenance strategies based on structural health monitoring are able to provide effective support when it comes to optimizing the scheduled repair of existing structures, enabling their lifetime to be extended. With a particular focus on reinforced concrete (RC) structures, the state of the art seems to still be lacking an efficient and cost-effective technique that is capable of monitoring inner stresses continuously over the lifetime of a structure. Current solutions can typically only measure the required mechanical variables in an indirect, but economic, manner, or directly, but expensively. Moreover, most of the solutions proposed can be implemented only by means of manual activation, making the monitoring very inefficient and then poorly supported. This study deals with a structural health monitoring solution based on a wireless sensor network (WSN) that enables the automatic monitoring of a reinforced concrete (RC) structure. The network is comprised of wireless distributed sensors embedded in the structure itself which can be suitable for a digital monitoring of innovative constructions, such as 3D printed structures, thus enabling the creation of smart structures according to the requirements of Industry 4.0.

FIBRE-BASED SECTIONAL ANALYSIS OF URM WALLS WITH SINGLE-SIDE FRCM STRENGTHENING

Recently, research community has shown a growing interest in inorganic matrix composite materials (referred to as Fiber Reinforced Cementitious Matrices, FRCMs, or Textile Reinforced Mortars, TRMs, or Inorganic Matrix-Grid composites, IMGs) as an effective solution for external strengthening of existing masonry walls. Such composites are typically made of a composite grid immersed in an inorganic mortar, making their mechanical behavior different from conventional fiber reinforced polymers, FRPs. While the in-plane behavior of unreinforced masonry (URM) walls strengthened with FRCM systems has been investigated through extensive experimental campaigns and numerical approaches, a comprehensive understanding of the out-of-plane behavior is still lacking, with particular reference to failure modes, analytical formulations and effects of different FRCM strengthening systems. In the present work, the available experimental outcomes on the out-of-plane behavior of strengthened URM walls are firstly collected, encompassing different URM types, eccentric load applications, FRCM strengthening systems. Then, a fiber-based sectional model of URM walls with single-side FRCM strengthening is proposed and validated with proper experiments. The tensile behavior of FRCM systems is modelled considering different characteristic phenomena of such materials, i.e. matrix cracking and fiber sliding. The results of the fiber-based analysis are in good agreement with experiments. 2578 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 2578-2586

Environmental sustainability assessment of structural retrofit of masonry buildings based on LCA

Over the last decade, the rehabilitation/renovation of existing buildings has progressively attracted the attention of the scientific community and government institutions. While many studies report on mechanical and energy improvements of retrofitted/renovated existing structures, only few works deal with the environmental impacts of such interventions and related assessment approaches. The environmental impacts related to a structural retrofit option can be successfully quantified by means of life-cycle assessment (LCA) techniques. In particular, a proper cradle to gate (or grave) system boundary can be considered at the scale of the existing building which is subjected to the structural retrofit process, encompassing design requirements and alternative solutions. We propose a step-by-step methodological approach based on LCA which aims to evaluate the life cycle environmental impacts of typical retrofit processes applied to existing masonry structures.