Nicolae Taranu

Full-Scale Shaking Table Tests on a Substandard RC Building Repaired and Strengthened with Post-Tensioned Metal Straps

The effectiveness of a novel Post-Tensioned Metal Strapping (PTMS) technique at enhancing the seismic behavior of a substandard RC building was investigated through full-scale, shake-table tests during the EU-funded project BANDIT. The building had inadequate reinforcement detailing in columns and joints to replicate old construction practices. After the bare building was initially damaged significantly, it was repaired and strengthened with PTMS to perform additional seismic tests. The PTMS technique improved considerably the seismic performance of the tested building. While the bare building experienced critical damage at an earthquake of PGA = 0.15 g, the PTMS-strengthened building sustained a PGA = 0.35 g earthquake without compromising stability.

Environmental impact of carbon fibre-reinforced polymer flexural strengthening solutions of reinforced concrete beams

PurposeThe properties of fibre-reinforced polymer (FRP) composites have led to a significant increase of civil engineering applications based on the usage of these materials. In the construction sector, FRP are mainly used for strengthening existing buildings, thus creating the possibility of avoiding the environmental problems resulting from demolishing these structures and constructing new ones. In the light of this new opportunity, the present paper aims at evaluating and comparing the environmental performances of an unstrengthened reinforced concrete (RC) beam with those of different carbon fibre-reinforced polymer (CFRP) flexural strengthening techniques.MethodsThe paper uses Life Cycle Assessment (LCA) methodology in order to determine the most environmentally friendly solution in the case of an existing RC beam which does not properly satisfy the structural demands. The authors have decided to use the Cradle-to-Gate LCA type of study, considering that the primary goal of the paper is to establish whether strengthening and reusing an existing RC beam can be considered a more viable environmentally friendly proposal in contrast with demolishing the existing structural element and constructing a new one. The following impact categories are used with the purpose of achieving a clear understanding of the products’ environmental influence: Climate Change, Human Toxicity, and Ozone Depletion. Their environmental performances are evaluated using the GaBi 6 software.Results and discussionThe obtained results show that all the assessed CFRP strengthening solutions have a significantly lower environmental impact in comparison with those of the RC beam. In the case of the analysed RC structural element, the highest impact is attributed to the manufacturing stage of the cement and to the steel reinforcements. In most of the CFRP strengthening schemes, the environmental impact is mainly influenced by the amount of component materials (fibre and resin) used for manufacturing the considered composite elements.ConclusionsThe resulted values for the environmental parameters in the assessed case studies encourage the authors to assert that the usage of composite materials in specific civil engineering applications can represent an environmentally friendly solution. The environmental aspect of sustainability can thus be achieved in this industry by using particular FRP strengthening applications. Moreover, the negative effects of modern society over Earth can be reduced. The paper concludes that the usage of composite materials can represent an important step towards the sustainable development of the construction sector.

RC COLUMN LATERAL PRESTRESSING WITH COMPOSITES

This paper deals with a novel strengthening technique for concrete columns that uses FRP materials to apply lateral pre-tensioning. The level of pre-tensioning of the FRP jacket is controlled by using different amounts of expansive agent. The technique aims to enhance the capacity and ductility of columns as well as achieve better utilisation of the confining FRP material. It is shown that jacketing columns by pre-tensioned FRP materials can increase the load bearing capacity up to 25% compared with conventional wrapping and up to more than 2 times compared with unconfined concrete. Pre-tensioning is shown to delay the initiation of the fracturing process of the concrete and this can have implication in design. The paper presents details of experimental work undertaken on wrapped concrete specimens with and without pre-tensioning. Results of two different confining materials (CFRP and GFRP) are presented.

Optimisation of Fabric Reinforced Polymer Composites Using a Variant of Genetic Algorithm

Fabric reinforced polymeric composites are high performance materials with a rather complex fabric geometry. Therefore, modelling this type of material is a cumbersome task, especially when an efficient use is targeted. One of the most important issue of its design process is the optimisation of the individual laminae and of the laminated structure as a whole. In order to do that, a parametric model of the material has been defined, emphasising the many geometric variables needed to be correlated in the complex process of optimisation. The input parameters involved in this work, include: widths or heights of the tows and the laminate stacking sequence, which are discrete variables, while the gaps between adjacent tows and the height of the neat matrix are continuous variables. This work is one of the first attempts of using a Genetic Algorithm (GA) to optimise the geometrical parameters of satin reinforced multi-layer composites. Given the mixed type of the input parameters involved, an original software called SOMGA (Satin Optimisation with a Modified Genetic Algorithm) has been conceived and utilised in this work. The main goal is to find the best possible solution to the problem of designing a composite material which is able to withstand to a given set of external, in-plane, loads. The optimisation process has been performed using a fitness function which can analyse and compare mechanical behaviour of different fabric reinforced composites, the results being correlated with the ultimate strains, which demonstrate the efficiency of the composite structure.

Influence of the Geometric Parameters on the Mechanical Behaviour of Fabric Reinforced Composite Laminates

A polymer fabric reinforced composite is a high performance material, which combines strength of the fibres with the flexibility and ductility of the matrix. For a better drapeability, the tows of fibres are interleaved, resulting the woven fabric, used as reinforcement. The complex geometric shape of the fabric is of paramount importance in establishing the deformability of the textile reinforced composite laminates. In this paper, an approach based on Classical Lamination Theory (CLT), combined with Finite Element Methods (FEM), using Failure Analysis and Internal Load Redistribution, is utilised, in order to compare the behaviour of the material under specific loads. The main goal is to analyse the deformability of certain types of textile reinforced composite laminates, using carbon fibre satin as reinforcement and epoxy resin as matrix. This is accomplished by studying the variation of the in-plane strains, given the fluctuation of several geometric parameters, namely the width of the reinforcing tow, the gap between two consecutive tows, the angle of laminae in a multi-layered configuration and the tows fibre volume fraction.

Life cycle analysis of strengthening concrete beams with FRP

Abstract The current consumption rates and the overall impact of humankind over the Earth’s ecosystem will reach a critical level, placing future generations into a perilous limit to evolution. Therefore, in the coming years, improving the state of the natural environment will represent a vital challenge for society. One of the most important tasks in achieving this global goal is represented by satisfying the primary aspects of sustainability in the construction sector. Thus, the present chapter analyzes the implications, with respect to the environmental dimension of sustainable development, from considering different carbon fiber-reinforced polymers for strengthening reinforced concrete (RC) beams. The main scope of the conducted life cycle assessment studies is to determine if composite materials should be considered in minimizing the environmental footprint of the built environment, by determining the most suitable solution: strengthening and reusing, or demolishing and building a new RC beam.

Shake Table Tests on Deficient RC Buildings Strengthened Using Post-Tensioned Metal Straps

The European research project BANDIT investigated the effectiveness of a novel Post-Tensioned Metal Strapping (PTMS) strengthening technique at improving the seismic performance of deficient RC buildings using shake table tests. A full-scale two-story structure was designed with inadequate reinforcement detailing of columns and beam-column joints so as to simulate typical deficient buildings in Mediterranean and developing countries. Initial shaking table tests were carried out until significant damage was observed in the beam-column joints of the bare frame. Subsequently, the damaged building was repaired and strengthened using PTMS and additional tests were performed. The results of this study show that the adopted strengthening strategy improved significantly the seismic performance of the substandard RC building under strong earthquake excitations.