Lampros N. Koutas

Use of Anchors in Shear Strengthening of Reinforced Concrete T-Beams with FRP

This paper presents an experimental investigation on the effectiveness of various types of spike anchors in combination with U-shaped fiber-reinforced polymer (FRP) jackets for shear strengthening of reinforced concrete T-beams. The parameters examined include the orientation, the number and spacing of anchors, and the role of carbon versus glass fibers in the anchors. It is concluded that anchors placed inside the slab are many times more effective than those placed horizontally inside the web, and anchors of similar geometrical characteristics (e.g., embedment length) display similar effectiveness despite the difference in fiber type. DOI: 10.1061/(ASCE)CC .1943-5614.0000316.

Seismic Strengthening of Masonry-Infilled RC Frames with TRM: Experimental Study

AbstractThis paper presents a technique for retrofitting nonseismically reinforced concrete (RC) masonry-infilled frames with textile-reinforced mortar (TRM) jacketing. In the present study the application of TRM is examined on nearly full-scale, as-built and retrofitted, three-story frames, subjected to in-plane cyclic loading. The results of testing a 2∶3 scale, as-built frame representing typical structures with nonseismic design and detailing characteristics and of a companion frame retrofitted via TRM jacketing are presented and compared in terms of the efficiency of the proposed technique to enhance the strength and deformation characteristics of substandard infilled frames.

Analytical Modeling of Masonry-Infilled RC Frames Retrofitted with Textile-Reinforced Mortar

This paper proposes an analytical approach for modeling the behavior of textile-reinforced mortar (TRM)-strengthened masonry-infilled reinforced-concrete (RC) frames under seismic loading. The model falls into the discrete diagonal-element type and is based on the use of single-strut and single-tie elements to represent the infill panel. It builds on the results of past experimental studies by the writers, in which the application of TRM jacketing was effective for seismic retrofitting of masonry-infilled RC frames. The model is implemented in a nonlinear finite-element code, with the parameters of the diagonal elements being determined from a series of tests on TRM coupons and masonry specimens. The results of the numerical analyses are compared with the experimental data of cyclic tests on 3-story masonry infilled RC frames (as-built and after retrofitting). The model developed in this paper adequately accounts for the TRM-strengthening contribution to the global response of masonry-infilled frames.

Strengthening of Infilled Reinforced Concrete Frames with TRM: Study on the Development and Testing of Textile-Based Anchors

The paper presents a technique for strengthening of reinforced concrete infilled frames with textile-reinforced mortar (TRM) jacketing. The key objective of the study is to examine different methods of masonry infill-concrete connection by developing and testing textile-based anchors at the interface between masonry wallettes and concrete. The parameters examined include mainly the type of boundary conditions at the masonry-concrete interface, the geometry and fiber volume of anchors and the type and number of layers of the textile. It is shown that the anchors developed in this study enable the transfer of substantial tensile forces between masonry and concrete and that their magnitude may be estimated on the basis of anchor properties.

Flexural Strengthening of Two-Way RC Slabs with Textile-Reinforced Mortar: Experimental Investigation and Design Equations

AbstractThe application of textile-reinforced mortar (TRM) as a means of increasing the flexural capacity of two-way reinforced concrete (RC) slabs is experimentally investigated in this study. The parameters examined include the number of TRM layers, the strengthening configuration, the textile fibers material (carbon versus glass), and the role of initial cracking in the slab. For this purpose six large-scale RC slabs were built and tested to failure under monotonic loading distributed at four points. It is concluded that TRM increases substantially the precracking stiffness, the cracking load, the postcracking stiffness, and eventually the flexural capacity of two-way RC slabs, whereas the strengthening configuration plays an important role in the effectiveness of the technique. Simple design equations that provide good estimation of the experimental flexural moment of resistance are proposed.

Analytical Modeling of Masonry Infilled RC Frames and Verification with Experimental Data

The assessment of the response of masonry infilled RC frame structures has been a major challenge over the last decades. While several modeling approaches have been proposed, none can cover all aspects observed in the tests. The present paper introduces a simplified model built on the approach established by Crisafulli and Carr (2007) and addresses its calibration and implementation in a nonlinear analysis software for the evaluation of the in-plane lateral response of infilled RC frames. The proposed model uses a set of elements/springs to account separately for the compressive and shear behavior of masonry. The efficiency of the modeling approach is validated with available experimental data, yielding satisfactory matching. The most intricate issue encountered when attempting to represent a masonry panel is the plethora of the material parameters involved and the lack of complete and available test results. Thus, the numerical investigation is accompanied by a parametric study on the sensitivity of the model to the various parameters to identify the critical modeling quantities and provide guidance on their selection.