Kamiran Abdouka

Bond behaviour between NSM CFRP strips and concrete substrate using single-lap shear testing with cement-based adhesives

Abstract The efficiency of strengthening RC beams using the near-surface mounted (NSM) carbon fibre-reinforced polymer (CFRP) method depends on the bond between the NSM CFRP and the concrete substrate. This study presents the results of a study of the bond efficiency of NSM CFRP strips with two different CFRP strip surface types (smooth, rough) and dimensions (1.4 × 10 mm, 1.4 × 20 mm) with cement-based adhesive using single-lap shear tests. The study also contains development of a statistical model to predict the bond strength (pull-out force). It was found that the rough surface CFRP showed superior bond strength (pull-out force) when compared to the smooth surface CFRP. Moreover, there is a very good agreement between the experimental and predicted results.

Displacement-based assessment of non ductile exterior wide band beam-column connections

Results from testing two half-scale exterior wide band beam-column sub-assemblages under cycles of lateral displacement are presented in this article. The first subassemblage represents the current level of detailing adopted in low to moderate seismic regions, such as Australia, for connections where seismic provisions are not normally a consideration in design. Minor (inexpensive) detailing changes in the reinforcement distribution and anchorage were introduced to the second test specimen. These changes significantly improved the connection performance in terms of increased displacement capacity and a reduction in strength deterioration. Using a displacement-based assessment approach to assess primary moment-resisting band beam frames of up to eight stories, it was found that the current level of detailing is adequate for the drift demands resulting from the expected Australian seismicity for a 500-year return period. However, for the displacement demands corresponding to a 2500-year return period, the frames sited on very soft soils and frames over four stories sited on intermediate soils would require improved detailing such as that used in the second sub-assemblage. A strength hierarchy of strong column-weak beam was assumed in this assessment.

Bond Behavior between NSM CFRP Strips and Concrete Exposed to Elevated Temperature Using Cement-Based and Epoxy Adhesives

AbstractThe repair and strengthening of existing concrete structures with composite material has become more common during the last decade. The near-surface-mounted (NSM) technique was used in this...

Post-Tensioned Band Beams as Moment Resisting Frames Under Earthquake Loading: A State-of-the-Art Review

Abstract Post-tensioned concrete wide-band beams are used increasingly as a common floor construction method in Australia. More recently, there has been a growing need for the floor system to contribute to the seismic resistance of the building as a moment frame. However, relatively little is known about the performance of wide post-tensioned beams under this type of loading. This paper reviews the current state of knowledge in this area, and assesses several current building design codes in terms of their relevance to this type of construction. Current research shows the potential to achieve adequate drift and energy dissipation in areas of low to moderate seismicity, but research is very limited, particularly for post-tensioned wide beams. While AS3600–2009 does not contain any width limitations on beams resisting earthquake loads, other codes do limit this width for certain levels of ductility. However, these design codes focus on narrow beams, and the beam width restrictions are generally based on limited research data. Construction techniques and seismicity levels vary significantly for different countries and this affects different design codes. Therefore, the relevance and applicability of several code design and detailing requirements in relation to beam widths and detailing typically used in Australia are questionable.

Exterior post-tensioned band beam to column connections under earthquake loading

Abstract Although post-tensioned wide band beams are an extremely common structural floor system in Australia, very little is known about their performance under seismic loading. This study presents the results of two half-scale exterior post-tensioned wide band beam to column connections under seismic loading. The specimens were designed and detailed in accordance with current Australian practice to AS 3600-2009 to resist gravity loading only. The first specimen had tendons evenly distributed throughout the beam width, while the second specimen had the outer tendons moved much closer to the column side face. Both specimens performed similarly and torsional damage to the edge beam was critical. Both specimens achieved drifts of 3.0% or higher prior to significant loss in capacity, which is greater than the imposed maximum drift limit in most design codes. A 3D finite element parametric analysis was undertaken using the experimental results to calibrate the model. In addition to ensuring all reinforcement is properly anchored, this analysis confirmed the importance of the edge beam in the behaviour of the overall connection. Providing closed ligatures in the edge beam to the side face of the column was found to be critical to ensuring overall ductility of the connection, as well as minimising additional torsion placed on the edge beam by concentrating reinforcement within the column width where possible.

Shear Force - Unbalanced Moment Transfer at R/C Exterior Wide Band Beam Connections

Abstract In this paper a new mechanical model for the transfer of unbalanced moment and shear in exterior wide band beam-column connections is proposed. It is based on the crack formation pattern and the mobilization of struts-and ties in the vicinity of the column. The critical section of the wide beam is divided into flexural and torsional elements and the unbalanced moment is divided between these elements as bending moment and torque. Shear force is also divided among these elements in proportion to the shear area of each element. A linear interaction between the shear force and torque carried by the torsional elements and their corresponding ultimate capacities is assumed.

Strengthening of slab–column connections against punching shear using FRP materials: state-of-the-art review

Abstract Many existing concrete slabs require strengthening in punching shear due to increased loading, change in use, design defect and structural damage. Of the different retrofitting techniques, the use of fibre reinforced polymer (FRP) reinforcements has proven to be an effective way to increase the punching shear capacity and ductility of flat slabs. There are many techniques for strengthening with FRP so in order to select and design an appropriate method, the most common documented methods should be known. A comprehensive literature review of the different FRP-strengthening methods for flat slabs against punching shear is presented in this paper. Each technique is discussed in terms of its results, advantages and disadvantages.