1,720,994 research outputs found
Assessment of performance of steel and GFRP bars as injected anchors in masonry walls
No full textThe first part of the paper presents the results of two series of in situ pull-out tests of injected anchors embedded in existing yellow tuff masonry walls. Anchors are made of steel and GFRP bars with diameter of 12 and 20 mm and were embedded by means of two types of grout: a cement-based and a pozzolana-based grout. The results were examined in terms of both maximum load and displacement to determine the most efficient bar-grout coupling. The experimental pull-out forces are also compared with the predictions given by several literature formulas. The second part of the paper is devoted to verify the efficiency of the tested injected anchor systems for avoiding out-of-plane damage mechanisms in masonry walls having varying slenderness and subjected to horizontal forces; to this aim parametric analyses were performed to calculate the seismic acceleration required to activate several out-of-plane mechanisms and to verify the effectiveness of injected anchors similar to those experimentally tested into avoiding them
Modelling of the bond behaviour of tuff elements externally bonded with FRP sheets
No full textThe performance of fibre reinforced plastic (FRP) materials used for external strengthening depends strongly on the bond behaviour at the FRP-substrate interface. In this paper, the results of an analytical model and of two Finite Element (FE) models (bi-and three-dimensional) for simulating bond behaviour in FRP-strengthened masonry elements using zero-thickness interface elements are presented. The primary parameters of bilinear and nonlinear bond-slip laws were determined from experimental results of single shear bond tests that the authors conducted on masonry blocks of yellow tuff bonded with FRP carbon and glass fabrics. Several parametric analyses were conducted to estimate the effect of the primary bond law parameters on the global behaviour of the specimens and to determine the effective bonded length for the investigated masonry support
Bond tests on tuff elements externally bonded with FRP materials
No full textThe experimental results of several bond tests on masonry blocks made of yellow tuff and
bonded with different types of Fibre Reinforced Plastic (FRP) fabrics carried out by the authors are
presented and analysed. The discussion of results is mainly focused on: (1) assessing the set-up reliability,
(2) choosing sufficient bonded length for achieving the full bond strength, (3) estimating the efficacy of end
anchoring systems, (4) evaluating the effect of a plastering layer and of the masonry strength on the
debonding load. The results are analysed both in terms of global (failure modes and loads, load–displacement
curves) and local behaviour (distribution of axial strains and shear stresses) aimed to evidence the
different behaviour of the used fibres (carbon, glass, basalt, flax). Finally, the experimental failure loads are
compared with formulations based on a ‘design by testing’ approach
Modelling of the in-plane behaviour of masonry walls strengthened with polymeric grids embedded in cementitious mortar layers
No full textThe seismic reinforcement of masonry walls needs to be carried out through appropriate and effective techniques aiming at providing both adequate strength and displacement capacity. The present research concerns experimental results about the in-plane behaviour of masonry walls strengthened through an innovative technique employing polymeric grids embedded in cementitious mortar layers applied on the wall surface. The behaviour of strengthened masonry walls subjected to cyclic shear-compression tests is examined in order to quantify the strength and displacement capacity increment provided by the reinforcement. A Finite Element Model of the unreinforced and reinforced panels has been developed and parameters defining masonry and strengthening materials have been calibrated by means of comparisons with the experimental results. The effectiveness of the strengthening system has been then numerically investigated through a wide parametric analysis varying the masonry strength, the wall shape, the axial stiffness of the strengthening grid and the strength of the mortar. Finally, a comparison of the effectiveness of the polymeric grid with a traditional steel one embedded in the same mortar layer is also reported
EXPERIMENTAL BEHAVIOUR OF MASONRY PANELS STRENGTHENED WITH FRP SHEETS
No full textThis paper is focused on the effectiveness of strengthening technique of masonry by continuous externally bonded (eb) Fiber Reinforced Polymers (FRPs) and reports on the obtained experimental results. Tuff panels were subjected to monotonic in-plane shear, combined with axial load. Performances of different types and amount of FRP, and of strengthening configurations are compared in terms of shear capacity, ultimate displacements and failure mechanism
Rapid visual screening for seismic evaluation of RC hospital buildings
No full textHospitals must be fully operational in the event of an emergency after an earthquake to protect the lives of patients and health workers as well as to provide emergency care and medical treatment to the subsequently increased number of patients who will be driven to healthcare facilities.
Surveys performed in the aftermath of recent earthquakes have shown that the performance of hospitals and their functionality after an earthquake are related not only to structural damage but also to damage that occurs to nonstructural elements and medical equipment.
For a large-scale mapping of the seismic risk to hospitals, it is impossible to proceed with advanced methodologies; simplified methodologies are thus required. These methodologies must consider the performance of nonstructural elements and equipment.
In this work, a rapid visual screening method is proposed to determine a Safety Index for hospital buildings. The newly developed procedure provides a risk index by evaluating the main parameters that affect the vulnerability of buildings during a systematic sidewalk survey. The procedure has been applied to two Italian hospitals located in different seismic areas, and the results are compared with a similar index obtained from a push-over analysis. Finally, the proposed RVS method has also been applied to two hospitals damaged by the 2009 L'Aquila Earthquake and the 2012 Emilia Earthquake
Assessment of a bond strength model for FRP reinforcement externally bonded over masonry blocks
No full textAccording to recent design Codes and Recommendations, verification against debonding is imperative in the design of strengthening interventions with Fiber Reinforced Polymers (FRP). In FRP – reinforced masonry elements, debonding at reinforcement extremities (end debonding) must be avoided by limiting the maximum force achievable by the strengthening system. This paper proposes design criteria against debonding in masonry elements externally strengthened by FRP sheets. Results of more than 250 bond tests, reported in the literature and carried out over different masonry supports, clay bricks and natural stones, are collected and examined. Formulas for fracture energy of interface bond law and debonding load are assessed starting from the experimental database. In order to provide design formulas according to the Partial Safety Factor Method for Ultimate Limit State verification, mean and characteristic values of the debonding load are determined through statistical methods
Erratum: Assessment of a bond strength model for FRP reinforcement externally bonded over masonry blocks (Compos. Part B: Eng. (2014) 61 (147-161) DOI: 10.1016/j.compositesb.2014.01.028)
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