Ann Schumacher

Numerical modelling of in-plane behaviour of URM walls and an investigation into the aspect ratio, vertical and horizontal post-tensioning and head joint as a parametric study

Masonry is a complex composite material with non-linear material properties, which make the numerical investigation of its structural behaviour a difficult task. In this paper, a micro non-linear model created using a general purpose finite element code, is discussed with respect to its ability to simulate the in-plane behaviour of unreinforced masonry walls. That is, the capability of model in predicting the cracking, crushing, and sliding phenomena, as well as the global-orthotropic behaviour of previously tested masonry walls are examined. The model is then used within a parametric study to investigate the effect of different aspect ratios, vertical and horizontal post-tensioning as well as the effect of head joints on the capacity of the masonry walls. It will be shown that, while enhancing the lateral in-plane strength of the masonry walls, vertical post-tensioning can also reduce their ductility. On the contrary, horizontal post-tensioning can cause a small reduction in the initial stiffness and yielding shear force of the masonry walls, but increases their integrity, thereby preventing them from sliding and shear failure. Furthermore, it will be shown that, in spite of having a significant influence on local behaviour, head joints do not influence the global behaviour of the masonry walls.

Fatigue strengthening of cracked steel beams with CFRP plates

Externally bonded FRP systems offer an attractive method to improve the fatigue life of steel beams. The fatigue performance of such a strengthened beam can be further enhanced by prestressing the bonded FRP reinforcement. While a number of studies have been conducted on the fatigue strengthening of steel beams using FRP, they have generally been concerned with the overall performance of the strengthened beam, with limited attention to the behaviour of the FRP-to-steel interface and its effects. Against this background, this paper presents the preliminary results of an ongoing experimental program aiming at investigating the behaviour and fatigue failure mechanism of FRP-strengthened cracked steel beams under fatigue cyclic loading, with particular emphasis on the debonding process of the FRP reinforcement and the effect of debonding on crack propagation. The effects of prestressing and debonding on the fatigue performance of the strengthened beam are clearly demonstrated by the test results.

Fibre reinforced polymer composite materials for building and construction

Abstract: Fibre reinforced polymers (FRPs), a relatively new class of non-corrosive, high-strength, lightweight material, have over the past approximately 15 years emerged as practical materials for a number of structural engineering applications. This chapter introduces constituent materials, FRP composite laminates and multilayer laminate theory, and the durability of composite materials for the construction and building industries, as well as future developments. Furthermore, some of the more common FRP applications in civil engineering structures and design rules are described in detail, including externally bonded FRP plates, sheets and wraps for the strengthening of reinforced concrete, steel, aluminium and timber structural members, FRP bars for the internal reinforcement of concrete, and application of FRP profiles.

Modern tubular truss bridges

Keywords: 465/ICOM Note: CD-ROM Reference ICOM-CONF-2002-005 Record created on 2008-01-24, modified on 2016-08-08

Flexural strengthening of beams using externally bonded plates: advanced optical measurements at the beam-to-plate interface

In a first test series, small-scale steel beams reinforced with adhesively bonded carbon fibre reinforced polymer (CFRP) plates were subjected to four-point bending. Phase-stepping 3D-digital speckle pattern interferometry (DSPI) was employed to measure the strain concentrations near the end of the CFRP plate, with a special focus on shear and normal strains. Furthermore, a refined finite element analyses (FEA) of the strengthened beam was carried out to predict these strains. Comparisons between measured and calculated strains have confirmed a strong variation of shear strain across the adhesive layer. The FEA has also shown the much higher normal strains present at the adhesive-steel (AS) interface than at the plate-adhesive (PA) interface. This difference has been suggested as the reason why debonding failure more commonly occurs at the AS interface rather than the PA interface. In a second study using optical measurement capabilities, a reinforced concrete (RC) beam was strengthened in flexure using a CFRP plate and tested in a four point bending test. In this study both conventional measurement techniques as well as an optical 3D image correlation system (ICS) were used to measure the displacements at the tension face of the beam. Results from the ICS measurements have shown interesting and unexpected slip distributions, in particular at the CFRP plate ends. Further experimental and analytical study is needed to confirm and understand this behaviour.

Espi-Measurement of Strain Components on a Cfrp-Reinforced Bending Beam

Reinforcement of structural elements using adhesively bonded carbon-fibre reinforced polymers (CFRP) is a well-advanced strengthening method. In particular, concrete or steel beams are strengthened with CFRP plates. Due to the stress concentration at the end of the plate debonding can often be expected. We describe a laboratory experiment to assess the stress transfer at the end of a CFRP plate, with a special focus on shear and normal stresses. A small-scale, 1.2 m long steel I-beam with 120 mm width was reinforced. The beam was loaded with manually controlled hydraulic jacks in a four-point bending arrangement. In order to allow interferometric measurements, the experiment was performed on a vibration isolated optical table in a temperature stabilized laboratory.