1,721,053 research outputs found
Tensile capacity of FRP anchors in connecting FRP and TRM sheets to concrete
Full text linkAbstractThis paper investigates the effectiveness of carbon fiber spike anchors as a means of anchoring externally bonded (EB) fiber-reinforced polymers (FRP) and textile reinforced mortar (TRM) sheets into concrete. The investigation employs experimental work, which includes reinforced concrete (RC) columns strengthened with various configurations of EB FRP and TRM sheets connected to RC footings via carbon fiber spike anchors. The fiber spikes have two parts: the anchor part and the fan part. The anchor part is a bar-type dowel component that is epoxy pre-impregnated and inserted into epoxy filled holes within the footing. The fan part was impregnated in-situ and fanned out over and bonded to the EB reinforcement of the column. The connections were tested by pulling the columns upwards, thus applying tensile forces to the connection system. The direct tensile capacity of the anchors was determined for a number of variables including the size and number of anchors, the bonding agent and the type and amount of EB reinforcement. It is concluded that, with appropriate anchorage into concrete, the carbon fiber spike anchor is an effective anchorage system, and therefore, could be used in a range of strengthening applications to prevent premature delamination of FRP and TRM sheets from concrete surfaces
A simplified model for rocking panels with friction connections
Full text linkIn recent decades, various rocking systems have been proposed to enhance the self-centring capacity of structures after seismic events. Sometimes dissipative devices have been added to control peak lateral displacements. However, the computational models currently available in the literature are not suitable for practitioners because they require the solution of complex differential equations describing the negative tangent stiffness that characterises the intrinsic instability of rocking motion.
To address this issue, this study explores a simplified model for rocking panels with panel-to-panel friction connections, potentially combined with moment-resisting frames. The remarkable sliding stiffness of these connections enables to simulate the system as a SDOF oscillator adapting original Displacement-Based Design (DBD) procedures, without the need to resort to closed-form solutions. The accuracy of the model is validated by comparing its results to pseudo-dynamic tests on a precast industrial building reported in the literature.JRC.E.3 - Built Environmen
Towards a Comprehensive Asset Integrity Management (AIM) Approach for European Infrastructures
Full text linkAbstractTransport infrastructure is the backbone of national economies, providing connections for people and goods, access to jobs and services, and enabling trade and economic growth. It is of paramount importance to preserve, maintain and upgrade the infrastructure network so that to sustain the economic growth and an intelligent mobility. Asset Integrity Management (AIM) approaches will therefore represent key tools for facing the infrastructure maintenance issue and for tackling the ageing that characterize already existing assets.This paper, starting from analyzing the current state of the art solutions in assets management (Enevoldsen, I., 2008), proposes a comprehensive AIM approach that aims at replacing current time-based approaches with a performance-based approach that can systematically take into account the dynamic nature of the transport network. This means moving from a deterministic to a probabilistic approach in design, rehabilitation and retrofitting of infrastructures for increasing life-time and reducing maintenance costs. Such approach therefore laid the basis of secure sustainable impact since by improving awareness and reducing uncertainties, it might allow achieving an optimal balance among available resources and planning of investments
Innovative Materials for Seismic and Energy Retrofitting of the Existing EU Buildings
Full text linkThe seismic and energy retrofitting of existing European buildings with innovative materials is addressed in this report. The need for retrofitting of old buildings emanates from their substandard design in terms of both earthquake resistance and thermal insulation. This is revealed during strong earthquakes that result in collapses and damages of old buildings and consequently in economic losses, severe injuries and loss of human lives. Moreover, the poor energy performance of old building envelopes increases their energy consumption. The objective of this report is to explore innovative solutions for seismic and energy retrofitting of existing buildings. Towards such an objective, this report conducts a state-of-the-art review on advanced materials and solutions for enhancing the safety, energy and resource efficiency of the deficient EU residential buildings. Following the consideration of the conventional and state-of-the-art building materials and solutions, the report goes beyond the state-of-the-art by introducing. At the end the main challenges that need to be addressed in building retrofitting projects are listed (cost, sustainability, durability), and recommendations for future research activities towards sustainable buildings retrofitting are proposed. Finally, the socio-economic and environmental impact expected from such research projects is preliminary assessed.JRC.E.4 - Safety and Security of Building
TRM vs FRP jacketing in shear strengthening of concrete members subjected to high temperatures
Full text linkThis paper presents the first study on the performance of TRM and FRP jacketing in shear strengthening of reinforced concrete (RC) members subjected to ambient and high temperatures, including both medium-scale rectangular beams and full-scale T-beams. Key parameters investigated on the mediumscale rectangular RC beams include: (a) the matrix used to impregnate the fibres, namely resin or mortar, resulting in two strengthening systems (TRM or FRP), (b) the level of high temperature to which the specimens are exposed (20 �C, 100 �C, 150 �C, 250 �C), (c) the strengthening configuration (sidebonding, U-wrapping and full-wrapping), (d) the number of jacketing layers (2 and 3) and (e) the textile properties (geometry, material). The effectiveness of both non-anchored and anchored TRM jackets in shear strengthening of full-scale T-beams at high temperature was also studied. It is concluded that TRM possess excellent performance as strengthening material at high temperature. TRM jacketing remained very effective in shear strengthening of concrete at high temperature; on the contrary the effectiveness of side-bonding and U-wrapping FRP jacketing was reduced nearly to zero when subjected at temperatures above the glass transition temperatur
Biaxial Bending of RC Columns Strengthened with Externally Applied Reinforcement in Combination with Confinement
No full textThe paper presents an analytical model for the analysis of reinforced concrete members with rectangular cross-section, strengthened in flexure with various types of externally applied reinforcement (near-surface mounted – NSM – or externally bonded – EBR), in combination with composite material confining jackets. The model takes into account simple but realistic constitutive laws for the constituent materials and through a simplified procedure yields the resistance of cross sections subjected to biaxial bending combined with axial loading. Verification of the analytical approach is provided by comparing the model predictions with existing test results published in the literature. The analytical formulation is then implemented in a user-friendly computer program, which is used to perform a number of parametric studies on the role of various factors (e.g. reinforcing ratios, level of axial force, level of confinement, type of external reinforcement and confining materials) in section resistance.JRC.G.5 - European laboratory for structural assessmen
Investigation of Bar Buckling in Columns Confined with Composite Material Jackets
No full textThe onset and evolution of bar buckling at the plastic hinge of old-type reinforced concrete (RC) columns confined with composite material [textile-reinforced mortar (TRM) and fiber-reinforced polymer (FRP)] jackets was investigated experimentally and analytically in this study. The interaction between composite jacket (or concrete cover, for unconfined concrete) and embedded longitudinal compression reinforcement at the onset and evolution of bar buckling was achieved through strain measurements of the compression reinforcement. Moreover, the implementation of a stress-strain confinement model, which relates lateral with axial strains, allowed the description and monitoring of the axial-lateral strain relationship at the base of the columns throughout the evolution of bar buckling. Finally, based on the aforementioned confinement model and on the experimental measurements, the post-buckling behaviour of columns was related with the stiffness of the jacket.JRC.G.5 - European laboratory for structural assessmen
Bond Strength of Lap Spliced Bars in Concrete Confined with Composite Jackets
No full textThe effectiveness of fiber-reinforced polymer (FRP) and textile-reinforced mortar (TRM)
jackets was investigated experimentally and analytically in this study as a means of confining
old-type reinforced concrete (RC) columns with limited capacity due to bond failure at lap
splice regions. The local bond strength between lap spliced bars and concrete was measured
experimentally along the lap splice region of six full-scale RC columns subjected to cyclic
uniaxial flexure under constant axial load. The bond strength of two column specimens tested
without retrofitting was found to be in good agreement with the predictions given by two
existing bond models. These models were modified to account for the contribution of
composite material jacketing to the bond resistance between lap spliced bars and concrete.
The effectiveness of FRP and TRM jackets against splitting at lap splices was quantified as a
function of jacket properties and geometry as well as in terms of the jacket effective strain,
which was found to depend on the ratio of lap splice length to bar diameter. Consequently,
simple equations for calculating the bond strength of lap splices in members confined with
composite materials (FRP or TRM) are proposed.JRC.DG.G.5 - European laboratory for structural assessmen
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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