Time-Dependent Behavior of Reinforced Polymer Concrete Columns under Eccentric Axial Loading

Polymer concretes (PCs) represent a promising alternative to traditional cementitious materials in the field of new construction. In fact, PCs exhibit high compressive strength and ultimate compressive strain values, as well as good chemical resistance. Within the context of these benefits, this paper presents a study on the time-dependent behavior of polymer concrete columns reinforced with different bar types using a mechanical model recently developed by the authors. Balanced internal reinforcements are considered (i.e., two bars at both the top and bottom of the cross-section). The investigation highlights relevant stress and strain variations over time and, consequently, the emergence of a significant decrease in concrete’s stiffness and strength over time. Therefore, the results indicate that deferred effects due to viscous flow may significantly affect the reliability of reinforced polymer concrete elements over time

on the statics of curved masonry structures via numerical models

Purpose This paper aims to review recent literature results on the equilibrium problem and the strengthening design of masonry vaults. Design/methodology/approach A Lumped Stress Method (LSM) is considered within the Heyman's safe theorem, based on the definition of thrust surface of a masonry curved structure. In particular, the static problem of the vault is formulated by introducing a membrane continuous of the studied masonry structure to associate with a spatial truss through a nonconforming variational approximation of the thrust surface and membrane stress potential. A tensegrity approach based on a minimal mass design strategy, different strengths in tension and compression of the material is discussed within the strengthening strategy of masonry vaults. Findings The numerical results have highlighted the efficacy of the two numerical approaches to assess the vulnerability of existing structures and design optimal strengthening interventions of these structures. Originality/value The presented models can represent fast and useful tools to assess the vulnerability of existing structures and design optimal strengthening interventions with composite materials of these structures

Cohesive fracture in composite systems: experimental setup and first results

Composite systems are widely used in many engineering applications for new structures and strengthening of existing ones. Within the structural rehabilitation of civil constructions, the plating technique of beams with Fiber Reinforced Polymer (FRP) represents a quick and optimal intervention with respect to traditional ones. The failure of these composite systems usually occurs due to the FRP debonding, which corresponds to a mode II fracture of concrete specimens. In this paper, a new experimental setup for investigating the mode II fracture behavior of FRP-concrete composite structures is presented. The test equipment consists of both conventional equipment and a non-contact optical technique, Digital Image Correlation (DIC), and the test system was realized at the Design Machine Laboratory of the University of Salerno. A preliminary test was performed and the corresponding results are shown and discussed

Experimental evaluation of the long-term creep deformations of epoxy resin

Abstract Adhesively bonded structures are widely used in many engineering fields for new structures and strengthening of existing ones. The failure of these joints are in some cases caused by long-term deformations. In this paper, an in house made experimental setup for investigating the creep behavior of epoxy resin specimens is presented. The test equipment consists of both conventional apparatus and a non-contact optical technique, Digital Image Correlation (DIC). Several tests were performed at different temperatures and the corresponding results were used for creep master curve construction by means of time-temperature superposition principle (TTSP)

Cohesive fracture in composite systems: experimental setup and first results

Composite systems are widely used in many engineering applications for new structures and strengthening of existing ones. Within the structural rehabilitation of civil constructions, the plating technique of beams with Fiber Reinforced Polymer (FRP) represents a quick and optimal intervention with respect to traditional ones. The failure of these composite systems usually occurs due to the FRP debonding, which corresponds to a mode II fracture of concrete specimens. In this paper, a new experimental setup for investigating the mode II fracture behavior of FRP-concrete composite structures is presented. The test equipment consists of both conventional equipment and a non-contact optical technique, Digital Image Correlation (DIC), and the test system was realized at the Design Machine Laboratory of the University of Salerno. A preliminary test was performed and the corresponding results are shown and discussed

Fracture Failure Modes in Fiber-Reinforced Polymer Systems Used for Strengthening Existing Structures

The development of promising new high-performance materials, such as composite materials made of fibers in a polymeric resin (fiber-reinforced polymer, or FRP), has transformed the structural rehabilitation and upgrade industry for buildings and infrastructure. Conventional materials and construction techniques (e.g., strengthening with externally bonded steel plates, known as beton plaqués, or steel/concrete jackets) have been supplanted by innovative ones. The most important emerging techniques involve the use of externally bonded composites as a quick and effective option for repairing and upgrading existing structures. Several issues regarding FRP–substrate interaction, mainly related to brittle failure mechanisms due to fracture phenomena, remain the focus of a great deal of research. This paper presents an overview of debonding behavior and its predictive modelling in externally bonded FRP systems

Anchorage device for FRP laminates in the strengthening of concrete structures close to beam-column joints

Fiber reinforced composite materials are frequently used in the rehabilitation or upgrading of reinforced concrete structures. Within this context, current international guidelines have set rules for the design of FRP strengthening applications. Nevertheless, some specific topics for seismic applications have to be studied more deeply. One of these is represented by the FRP plating of members subject to bending moment, or bending moment and axial force, when such an intervention is executed close to beam-column joints, due to the need for suitable FRP anchorage devices. There are still only a few not conclusive studies currently available in literature on this topic. In this paper, the main features of a device prototype, proposed by the authors, and the results of an experimental program are reported. The tests have been performed at the Testing Laboratory of Material and Structures of the Department of Civil Engineering of the University of Salerno, within ReLUIS (University Network of Seismic Engineering Laboratories) Consortium research program