1,721,191 research outputs found
DESIGN PROVISIONS FOR END-ANCHORING DEVICES IN CONCRETE AND MASONRY ELEMENTS EXTERNALLY BONDED WITH FRP MATERIALS
No full textAnchoring devices for external strengthening systems made of Fiber Reinforced Plastic (FRP) materials represent a solution to avoid or delay debonding phenomena in concrete and masonry strengthened elements. Several types of anchoring devices were tested by researchers and used in real applications in the last years, but clear design indication for estimating the effectiveness of each anchoring type are still not available. Basing on the examination of the available experimental results of bond tests in concrete and masonry specimens externally bonded with FRP materials, this paper is aimed to furnish design indications for calculating the effectiveness of two types of common end anchoring systems in term of theoretical debonding load increase: 1) transversal FRP strips and 2) FRP spike anchors
Bond tests on concrete and masonry blocks externally bonded with FRP
No full textThe paper is a preliminary presentation of a study focused on definition of the bond properties of carbon and glass fibers externally bonded to strengthen concrete and masonry elements. An experimental program is now in progress starting from the analysis of previous bond tests: monotonic and cyclic loads will be applied on concrete and masonry specimens according to a pull-out test procedure considering various configurations of FRP sheets, anchorage systems, environmental temperature. Comparisons of available experimental tests with existing debonding formulations are developed to check their effectiveness
Effectiveness of anchoring devices for CFRP sheets epoxy bonded over tuff blocks
No full textThis paper examines the results of an experimental program made of bond tests on yellow tuff masonry elements externally bonded with Carbon Fibre Reinforced Plastic (CFRP) sheets. The experimental tests have been carried out according to a single pull-push set-up and were mainly aimed to investigate the effectiveness of different anchoring systems for avoiding or delayed debonding phenomena. The experimental results have been examined both in terms of debonding load, load-slips curves and distribution of axial strains in order to highlight the effectiveness of the different anchoring systems
Effectiveness of design formulations for injected anchors in masonry elements
No full textThe paper is aimed to carry out a critical analysis of the available experimental results of pull-out tests related to several types of injected anchors in masonry elements. The database is also comprehensive of the results of some experimental pull-out tests directly carried out by the Authors. Both data on traditional steel bars and on anchors made by innovative materials embedded in several types of masonry made of natural stones and clay bricks are included in the database. Firstly, the main parameters influencing the experimental pull-out forces in the collected database were analyzed. Successively, the experimental values of the pull-out forces were compared with theoretical predictions provided by existing formulations and their reliability was discussed. Finally, regression analyses were carried out on the available database in order to assess new design formulations taking into account the main parameters influencing the performance of injected anchors
Analysis of bond behavior of injected anchors in masonry elements by means of Finite Element Modeling
No full textInjected anchors made of steel bars embedded in masonry elements by means of cement-based grout represented in the past a wide solution for avoiding out-of-plane mechanisms. Corrosion phenomena in steel bars reduced the effectiveness of such type of intervention over time. Innovative materials, as the Fiber Reinforced Plastic ones, can represent a suitable alternative to increase durability and performance of injected anchors. Since the effectiveness of injected anchors is strictly related to bond behaviour along both the bar-grout and the grout-masonry interfaces, a detailed analysis by means of a Finite Element model was developed for different types of bars embedded in masonry elements. The numerical model was firstly calibrated on some experimental results of pull-out tests available in literature and, then, is used for investigating the effects of several parameters on both local and global behaviour. Load-displacement curves and local distributions of shear stresses are examined in detail. The numerical analyses evidenced that the maximum tensile force in the anchor mainly depends on the shear strength of the bar-grout and the grout-masonry interfaces and on the embedded length, but for very long embedded length, it can be limited by the tensile failure in the anchor or in the masonry
Finite Element Modelling of Masonry Panels Reinforced with FRP Grids
No full textThe effect of the application of strengthening systems in form of polymeric grids embedded in inorganic matrix on
masonry elements is not easy to assess and represents a fundamental issue with respect to the preservation of
masonry buildings in seismic areas. In addition, recent seismic codes do not provide specific criteria for assessment
of existing masonry walls reinforced with such type of technique. In this paper the main results of experiments
carried out on unreinforced and reinforced masonry panels with mortar layers strengthened with composite grids
are briefly described. The reinforcement, made of polymeric grids, was applied in a symmetric way on both sides
of the panels. The panels were tested against in-plane actions with refer to a combination of a vertical static load
and a horizontal cyclic load. Successively, a Finite Element Model (FEM) of the unreinforced and reinforced
masonry panels has been employed in order to: 1) assess some mechanical parameters of the materials influencing
the global non-linear response of the panels in their plane, and 2) evaluate the efficiency of such a strengthening
system
Strength capacity of RC beams without shear reinforcement: Numerical analysis and comparisons with code provisions
No full textThe investigation of the behavior of reinforced concrete (RC) elements without shear reinforcement is a current focal point, driven by the incomplete consolidation of predictive formulas for shear strength in RC elements. Currently, the literature provides, indeed, a limited number of experimental and numerical studies on this subject. This paper seeks to advance the comprehension of the behavior and collapse mechanisms of RC beams not provided of shear reinforcement, as commonly employed in RC slabs of bridges. The paper commences with a critical review of several predictive formulas for the shear strength of RC elements lacking transverse reinforcement, as stipulated by various international codes. The objective is to identify the principal parameters involved in the formulations and discuss their roles also by means of sensitivity analysis. Following this, the results of nonlinear numerical analyses, based on a three-dimensional finite element (FE) model, are presented. The FE model was initially calibrated using experimental results from a benchmark beam lacking shear reinforcement, retrieved from the literature, which exhibited a brittle shear failure. Subsequently, several specimens were prepared for the numerical investigation, assuming multiple combinations of geometrical and mechanical parameters. For specimens experiencing shear failure, the strength was compared with that provided by code formulas, as well as using the strut-and-tie approach for the cases characterized by a reduced shear span-to-depth ratio. In general, these analytical tools significantly underestimated the numerical strength, underscoring the necessity for further insights based on experimental tests. The numerical outcomes have been, indeed, prodromal to design an experimental campaign
Cracking Behaviour of RC Beams Externally Strengthened with Emerging Materials
No full textThis paper presents some experimental results about cracking phenomena of reinforced concrete beams externally strengthened with
bonded composite materials. Carbon Fibre Reinforced Polymers (CFRP) laminates or steel (SRP) tapes have been used. Comparisons
with analytical results in terms of cracks width and crack spacing are reported using an analytical model developed by the authors, taking
into account the non-linear behaviour of materials and bond laws. Comparisons at service condition with code formulas are also
reported
Evaluation of bond strength in concrete elements externally reinforced with CFRP sheets and anchoring devices
No full textUse of anchoring devices can be useful to avoid or delay end debonding failure in reinforced concrete elements externally
bonded with fiber-reinforced plastic materials. Many theoretical formulations are now available to predict bond strength, but no design
provisions have been suggested to take into account the beneficial effect of anchorage devices. This paper presents the results of
experimental bond tests performed on concrete blocks externally strengthened with carbon fiber sheets. The prime focus is the evaluation
of effect given by three different types of anchorage systems upon increasing debonding load. A simple model is introduced to predict the
influence of the examined anchorage systems on the debonding load. Its accuracy is confirmed by comparisons with the experimental
results
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