Papers by Keyword: Fiber Reinforced Polymer (FRP)

Abstract: This contribution is devoted to assess the capability of a new upper-bound approach for the limit analysis of FRP-reinforced masonry arches by comparing it to both experimental tests and a number of existing numerical procedures. The approach is based on an idea previously presented by the Authors and relies on the representation of the geometry of both the arch and of FRP reinforcement through Non Uniform Rational B-Spline (NURBS) functions. This allows generating a rigid body assembly starting from the assigned geometry composed by very few elements which still provide an exact representation of the original shape. A homogenized kinematic formulation for the limit analysis of the obtained rigid blocks assembly is derived, which accounts for the main properties of masonry material. FRP material is included exploiting the Italian CNR Recommendations for the design of FRP based reinforcing interventions. The approach is capable of accurately predicting the load bearing capacity of masonry arches of arbitrary geometry, provided that the initial mesh is adjusted by means of a suitably devised Genetic Algorithm (GA) until the active interfaces among blocks (e.g. hinges) closely approximate the actual failure mechanism.

Abstract: An innovative approach is proposed to define the optimal fiber-reinforcement of in-plane loaded masonry walls, modeled as linear elastic no-tension (NT) bodies. A topology optimization formulation is presented, which aims at distributing a prescribed amount of reinforcement over the wall, so as to minimize the overall elastic energy of the strengthened element. Perfect bonding is assumed at the wall-reinforcement interface. To account for the negligible tensile strength of brickwork, the material is replaced by an equivalent orthotropic material with negligible stiffness along the direction (s) undergoing tensile principal stress (es). Compressive principal stresses in the reinforcement are not allowed. A single constrained optimization problem allows both the equilibrium of the NT body to be enforced, and the optimal reinforcing layout to be spotted out, without any demanding incremental approach. Some preliminary numerical examples are shown to assess the capabilities of the proposed procedure and to identify the optimal reinforcement patterns for common types of masonry walls with openings.

Abstract: Concrete-filled FRP tube (CFFT) columns have recently gained significant research attention, with a number of experimental studies identifying significant benefits of using high-strength concrete (HSC) to produce high-performance CFFT columns. A recent experimental investigation revealed that prestressing the fibers in the fiber reinforced polymer (FRP) confining shell leads to significant improvements in the axial compressive behavior of HSC-CFFTs. This paper reports the findings from an analytical investigation into the lateral strain-to-axial strain relationship for prestressed HSC-CFFTs. This understanding of the lateral strain-to-axial strain relationship is of particular importance for prestressed CFFTs due to the influence of the additional lateral prestrain. Initially a database that consists of 23 aramid FRP- (AFRP) confined HSC cylindrical specimens with lateral prestress of up to 7.3 MPa is presented. Based on close examination of the experimentally recorded data, an expression to predict the lateral strain-to-axial strain relationship for prestressed HSC-CFFTs is proposed. The comparison of the proposed model predictions with the experimental test results for specimens prepared with prestressed FRP tubes shows good agreement.

Abstract: Concrete in-filled steel tube (CIFST) columns are mainly used as structural members in buildings located in seismic zones. CIFST columns prone to buckling and technique is required to control the buckling of concrete filled steel tubes when they are subjected to cycles of loading. In this work, CIFST columns wrapped with fibre reinforced polymer laminates (FRPL) to prevent the local buckling. Experimental and analytical study of CIFST columns externally wrapped with FRPL have been conducted. Theoretical study is also conducted to find the ultimate load carrying capacity of CIFST columns. The parameters involved in this investigation are type of fibre and shape of the steel tube. The CIFST columns are tested under lateral loading to determine the number of cycles to failure and energy absorption capacity and to observe the hysteresis behaviour. The analytical study comprises of finite element modeling of CIFST columns wrapped with FRPL. The results obtained from the experimental investigation and finite element model are compared. The results revealed that FRPL wrapped circular CIFST columns have higher load carrying capacity and energy absorption capacity and exhibit ductile behavior when compared to CIFST columns.

Abstract: Reinforced concrete (RC) is the most popular building material in the construction industry. It is a composite material in which low tensile strength and ductility of concrete are counteracted by the inclusion of reinforcement having higher tensile strength and ductility. The RC based structures are required to be replaced after their life time. Complete replacement will be a huge financial burden and might certainly be a waste of natural resources when upgrading or strengthening is an adoptable alternative. Strengthening can be achieved through retrofitting. The meaning of retrofitting is addition of new technology, components, accessories or features to older systems. Retrofitting may be required when the structure needs to be used for a purpose dealing with more load compared to design loads. It may also be used where old structures are needed to be upgraded. This paper is focused on the retrofitting of simply supported RC beams. Various materials like polymers, cementitious composites, steel sections etc. are used for retrofitting of RC beams. For the addition of these new materials to the existing ones, various techniques are used. This paper is a review of the materials and techniques used in retrofitting process of RC beams in existing buildings. The effectiveness of each material and technique is also reviewed.

Abstract: This paper presents the results of 20 hollow and concrete-filled double-skin tubular columns (DSTCs), which were tested as part of a comprehensive experimental program that was undertaken at The University of Adelaide on FRP-concrete steel DSTCs. The paper is aimed at providing important insights into the influence of two key parameters, namely the diameter of inner steel tube and presence/absence of a concrete-filling inside the inner steel tube, which play major roles in the column behavior through their influences on a series of interacting mechanisms that govern the complex system behavior. A detailed examination of the results yielded a number of important insights into the mechanisms that influence the compressive behavior of DSTCs.

Abstract: In order to promote the usage of structural insulated panels (SIP) as floor and roof for residential buildings, the bending capacity of SIP should be improved. In this paper, fiber reinforced polymer sheets were used as strengthening materials. The new variation of SIPs, which is called Fiber Reinforced Structural Insulated Panel (FSIP), was tested in this paper. Five one-way slabs were subjected to uniformly distributed loads till failure. It is observed that the flexural bearing capacity and stiffness of the slabs were affected by the thickness of foam core and the strength of FRP sheet. By strengthened with FRP sheets, the one-way slab of structural insulated panel can be used for floor and roof in residential and light commercial buildings.

Abstract: This paper reports on an experimental investigation on the influence of FRP-to-concrete interface gap, caused by concrete shrinkage, on axial compressive behavior of concrete-filled FRP tube (CFFT) columns. A total of 12 aramid FRP (AFRP)-confined concrete specimens with circular cross-sections were manufactured. 3 of these specimens were instrumented to monitor long term shrinkage strain development and the remaining 9 were tested under monotonic axial compression. The influence of concrete shrinkage was examined by applying a gap of up to 0.06 mm thickness at the FRP-to-concrete interface, simulating 800 microstrain of shrinkage in the radial direction. Axial strain recordings were compared on specimens instrumented with two different measurement methods: full-and mid-height linear variable displacement transformers (LVDTs). Results of the experimental study indicate that the influence of interface gap on stress-strain behavior is significant, with an increase in interface gap resulting in a decrease and increase in the compressive strength and ultimate axial strain, respectively. It was also observed that an increase in interface gap leads to a slight loss in axial stress at the transition region of the stress-strain curve. Finally, it is found that an increase in the interface gap results in a significant decrease in the ratio of the ultimate axial strains obtained from mid-section and full-height LVDTs.

Abstract: Fibre reinforced polymer composites have been widely used in automotive industries due to its high tensile strength, lightweight and potential resistance towards environmental conditions. This paper presents a study on the fatigue life prediction of fibre-reinforced polymer (FRP) and the application of FRP composite in manufacturing engineering industries. Four designs of I-beam with different thickness and fillet were studied. The analyses of fatigue life of the designs were done using ANSYS software. Results from the analysis showed that the combination of glass/polyester and the design of I-beam with a fillet of 10mm and thickness of 20mm was the best combination in terms of its good fatigue life, factor of safety and stronger top surface.

Abstract: Recently, a new type of composite system was proposed in the form of fibre reinforced polymer (FRP)-concrete-steel double-skin tubular columns (DSTCs). The performance of this column system, which consists of an outer tube made of FRP and an inner tube made of steel, has been experimentally investigated in a number of studies. However, apart from a single study reported on square DSTCs, all of the existing studies have been concerned with DSTCs with circular external tubes. This paper reports on part of an ongoing experimental program at the University of Adelaide that was aimed at addressing this research gap. The effect of cross-sectional shape of inner steel tube on compressive behaviour of square DSTCs was investigated through the test of 16 hollow and concrete-filled DSTCs. The result of the experimental study indicate that concrete in hollow DSTCs with circular inner steel tubes develop significantly larger ultimate axial stresses and strains than concrete in companion hollow DSTCs with square inner steel tubes. On the other hand, the results also indicate that the presence of a concrete-filling inside inner steel tubes results in a significant improvement in the behavior of DSTCs with square inner steel tubes.