International Concrete Abstracts Portal

Although the International Building Code (IBC) refers to the American Concrete Institute - ACI 318 Building Code for reinforced concrete design and to the Masonry Standards Joint Committee Building Code for Masonry Structures (TMS 402/ACI 530/ASCE 5) for masonry building design, neither ACI 318 nor TMS 402/ACI 530/ASCE 5 contain provisions for externally bonded FRP applications. To address this limitation, the International Code Council – Evaluation Services (ICC-ES) published in 1997 the acceptance criteria (AC125) to provide minimum requirements for externally bonded FRP strengthening systems, while meeting the main objectives of the building code, including strength, serviceability, fire safety, and durability. This paper provides the background for the latest revisions to the design criteria section of AC125 to reflect recent FRP knowledge regarding strength and serviceability requirements. These changes align AC125 with ACI 440.2R-08 and ACI 440.7R-10 guidelines, which would provide consistency in evaluation and design requirements of externally bonded FRP composites.

A method for strengthening reinforced concrete members using mechanically-fastened FRP (MF-FRP) has been studied in laboratory investigations and in several bridge strengthening demonstration projects. The strengthening is obtained by attaching FRP strips, with high bearing and longitudinal strengths, to concrete elements using steel power actuated fastening “pins” (PAFs), steel anchor bolts or concrete screws, or a combination thereof. The MF-FRP method requires minimal surface preparation and permits immediate use of the strengthened structure. Published research on this method with a range of member sizes has shown promising results in terms of installation efficiency, level of strengthening achieved, and preventing strip delamination before concrete crushing. This State-of-the-Art paper presents an overview of work conducted over the last 10 years on experimental aspects of the MF-FRP method, with beams as well as one-way and two-way slabs. A database of collected test results for MF-FRP strengthened beams and one-way slabs is presented.

A large part of tuff buildings in the Mediterranean area is of historical and artistic relevance. Such buildings are placed in seismic areas and, due to their age, have been subjected to environmental deterioration. For this reason, in the last decades, the interest in strengthening of historical tuff masonry structures is significantly grown especially to techniques that allow properties like as reversibility, compatibility, and sustainability of the intervention to be combined. In the present paper, the results of diagonal compression tests on yellow tuff masonry panels is presented; the specimens were reinforced by using an innovative strengthening system based on the combined use of a pre-cured alkali-resistant basalt or glass FRP grid bonded with a cement based mortar or pre-mixed high ductility hydraulic lime and pozzolan based mortar. Base material properties as well as panels in-plane deformation and strength, including the post peak softening regime in view of seismic applications, are reported in the paper. The experimental results confirmed the effectiveness of the investigated strengthening technique to increase the tuff panels shear strength and validated the use of an innovative mortar specifically formulated to increase the compatibility with tuff material and historical grouting.

This paper describes a simplified methodology to design masonry and concrete walls retrofitted with fiber-reinforced polymer (FRP) products to resist blast load. The wall is analyzed as an equivalent single-degree-of-freedom (SDOF) system responding in flexure to a spatially uniform blast load. The methodology provides specific guidance on how to define all the relevant properties of the equivalent SDOF system based on flexural and shear properties of the retrofitted wall using equations similar to those for static properties of retrofitted walls in ACI 440.2R responding in flexure. The methodology also provides response limits that give correlations between the calculated maximum dynamic response and the corresponding blast damage level to the retrofitted wall. The response limits can be used to design a blast resistant wall for a given amount of acceptable damage. This paper discusses the SDOF-based procedure, summarizes available blast test data on retrofitted walls, and shows comparisons between maximum deflections calculated with equivalent SDOF models of the test walls and measured values. Also, the development of the response limits is described with photographs of observed wall damage levels in shock tube tests.

Carbon Fibre reinforced Polymers (CFRP) have become an effective solution to upgrade and strengthen existing box girder bridges in flexure, shear and torsion. The introduction of CFRP strain limitations to prevent premature delamination together with the increasing strengthening demands and the necessity for use of fibres of increasing stiffness and thickness has resulted in a very poor CFRP material utilisation levels achieved in practice. An effective method to increase CFRP material utilisation is by appropriately anchoring the ends of the CFRP. In this paper, a study into CFRP end anchorage solutions is presented which formed the basis of the experimental program. Both uni-directional and bi-directional fabric was applied to the ends of CFRP laminates and tested under direct shear loading. Uni-directional fabric was oriented both horizontally across and parallel to the direction of the laminate. In all cases it was found that the anchorages solutions tested resulted in a distribution of fibre-to-adhesive bond stresses over a greater length, width of concrete and could potentially result full CFRP utilisation and laminate rupture.