Shear strengthening of reinforced concrete T‐beams with fully or partially bonded fibre‐reinforced polymer composites

Austrian Federal Railways ÖBB, Austrian motorway operator ASFINAG Strengthening methods for shear-deficient bridges were developed and tested in cooperation with the HILTI Corporation and SIKA Austria. In order to identify the strengthening effect in shear, a number of 12 T-shaped RC-beams with a length of 5.38 m were designed. In the experimental campaign two different types of strengthening systems were applied and subjected to shear loading until failure. The successful use of a modern digital image correlation system provided the basis for an in-depth analysis of failure mode and crack pattern as well as shear degradation at each load stage. Finally, the applicability of existing shear design models with consideration of the strengthening elements analogously to cast-in shear reinforcement was evaluated.anchorage, carbon fiber, FRP, postinstalled, shear, shear test, strengthening, undercut anchor 1 | INTRODUCTION Subsequent strengthening of existing structures has gained in importance over the last decades due to the decreasing number of new structures and the ever-growing number of existing ones. The ongoing increase in traffic loads, continuous updating of design codes, and also paradigm shifts lead to the fact that a number of existing bridge structures do not fulfill the required safety level concerning the shearbearing capacity as required by codes of practice such as Eurocode 2. 1 Meanwhile, there exist refined methods for the verification of the shear load-bearing capacity 2-7 , developed from more consistent mechanical models. MC2010 8 provides advanced design approaches allowing for a better utilization of the real structural resistance. Nevertheless, the need for sound technical solutions in the subsequent shear strengthening of existing reinforced concrete (RC) structures is constantly increasing.While the flexural strengthening of RC members has become a routine task, the retrofitting of shear-deficient members is still a challenging issue for the following reasons:• Local shear retrofitting requires the introduction of forces over very short distances. In comparison, flexural strengthening is oriented in the longitudinal direction of a structural member and usually applied over larger sections. Therefore, adequate stiffness and proper anchorage solutions are needed when strengthening in shear. • The strengthening system must be reliably activated without the necessity of large additional live loads or deformations of the structure. • Currently, there are no harmonized recommendations for RC shear design itself available; therefore, the rather complex design of shear strengthening is even more disputable.A few established methods to strengthen RC structures in shear already exist (see e.g., overview in Reference 9). Selected popular methods for shear strengthening are discussed and compared on the basis of experimental investigations in Reference 10. With respect to the affected sections of a structure and the impact on the overall structural behavior, such strengthening solutions can generally be...

Section: Test Results and Evaluationsupporting

confidence: 90%

Section: Applied Strengthening Techniquesmentioning

confidence: 99%

See 1 more Smart Citation

Developing optimized strengthening systems for shear‐deficient concrete members

Randl

Harsányi

2017

“…Various strengthening techniques have been proposed in the past decades to improve the structural performance and to extend the service life of RC structures. These techniques include externally‐bonded steel plates, ferrocement, and fiber reinforced polymer (FRP) . Latterly, fabric reinforced cementitious matrix (FRCM), aka textile reinforced mortar or textile reinforced concrete, has emerged as a promising strengthening material for RC and masonry structures .…”

Section: Introductionmentioning

confidence: 99%

Tensile characterization of multi‐ply fabric‐reinforced cementitious matrix strengthening systems

Younis

Ebead

Shrestha

2019

Fabric reinforced cementitious matrix (FRCM) is a composite consisted of highstrength fibers impregnated in a cement-based mortar, and is commonly used for strengthening reinforced concrete and masonry structures. Comprehending the tensile behavior of FRCM is important to achieve a reliable and accurate design of FRCM strengthening systems. The current paper reports on the results of an experimental study on the tensile characterization of FRCM. A total of 40 FRCM specimens (410 × 50 mm, varied in thickness) were prepared and tested. The tensile characterization tests were conducted according to AC 434 guidelines using clevisgrip mechanism. The tests were used to assess the effect of two parameters:(a) fabric type (carbon/glass) and (b) number of fabric plies (one/two/three/four).The results showed that the tensile strength of carbon-FRCM specimens was approximately 1.33 times that of the glass-FRCM counterparts. Three distinct failure modes were observed, namely, (a) ductile fabric slippage in carbon-FRCM (up to three plies of fabric); (b) brittle fabric delamination in carbon-FRCM with four plies of fabric;and (c) brittle fabric rupture in glass-FRCM systems. The FRCM tensile loadcarrying capacity had proportionally increased with the number of fabric plies; less significant effect (within 20%) was observed on the corresponding ultimate tensile stresses (considering the net fabric area as the effective area). K E Y W O R D Scomposite, fabric-reinforced cementitious matrix, mechanical characterization, strengthening, textile reinforced concrete, textile reinforced mortar

“…As the rebuilding of old infrastructure is too expensive and time consuming, durable techniques of rehabilitation are needed. There is a growing interest in the use of FRP composite materials for the strengthening and retrofitting of concrete structures . The application of FRP sheet has broadly been considered in civil engineering because of its proper mechanical properties in retrofitting concrete structures.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on fracture behavior of notched self‐consolidating concrete beam strengthened with off‐axis CFRP sheet

Sangi

Amiri

Abdollahzadeh

et al. 2019

In this study, the effects of fiber orientation within the carbon fiber reinforced (CFRP) sheets, on the fracture mode and crack growth of specimens were investigated by constructing five groups of initially notched self‐consolidating concrete beams, and strengthening them with CFRP sheets in the tensile area. Furthermore, the bearing capacity, strain variation along the sheet, crack mouth opening, and the midspan displacement were recorded by varying the height of the beams and the initial notch lengths. The results indicate that the load‐crack mouth opening curves have two peak load points. First, the applied load increases up to one peak value and then there is a drop in the load‐caring capacity. Afterwards, the applied load is improved to another peak value due to the relatively high cohesive effect of the CFRP sheet. The results show that as the height of the beam section increases, or the initial notch length decreases, the first and the second peak loads increase. By comparing the specimens with different fiber angles in each group, it was observed that the specimen with fiber angle 0° has a higher capacity relative to other angles, yet its failure occurs in a lower displacement. Furthermore, with the help of finite element software and nonlinear static analysis, the behavior of the aforementioned beams including the stress and strain distributions in the CFRP sheet, and the sheet‐to‐concrete bond zone have been examined and compared with the existing experimental results for validation.