Bilal El-Ariss

Behavior of Concrete Beams with Short Shear Span and Web Opening Strengthened in Shear with CFRP Composites

This paper presents test results of 16 reinforced concrete (RC) beams with web openings strengthened in shear with externally bonded carbon fiber reinforced polymer (CFRP) composite sheets. Test specimen was 2,600 mm long with a cross section of 85 mm × 400 mm and a shear span to beam depth ratio of a=h ¼ 2. All specimens had the same geometry and main longitudinal top and bottom reinforcement. No internal web reinforcement was provided in the test region to resemble the case of inclusion or enlargement of an opening in an existing beam which would typically result in cutting the internal web reinforcement around the opening. The test parameters were the width and depth of the opening and the amount of the CFRP sheets used for shear strengthening. Test results showed that the inclusion of web openings drastically reduced the beam shear capacity and stiffness. External strengthening with CFRP sheets around the opening was found to be very effective in improving the beam shear resistance and stiffness. Increasing the opening width or depth reduced the gain in the shear capacity caused by the CFRP. Doubling the amount of the vertical CFRP sheets from one to two layers increased the shear capacity but the additional shear capacity gain was not in proportion to the added amount of the CFRP. An analytical approach for prediction of the shear capacity of RC beams with openings strengthened in shear with CFRP was introduced on the basis of the American Concrete Institute (ACI) 440.2R-08 and other formulas published in the literature. The analytical approach showed good agreement with the test results. DOI: 10.1061/(ASCE)CC.1943-5614.0000237.

Optimal finite element modelling for modal analysis of liquid storage circular tanks

Model analysis of liquid storage vertical tanks is a complex task due to fluid-structure-soil interaction. Analysis of tanks subjected to earthquake excitations using finite element modelling (FEM) has become a preferred technique. The FEM is validated by comparing its results with experimental and theoretical results in the literature. However, most finite element studies in literature do not provide enough details on the selection of the elements used. The objective of this study is to provide optimal FEM options of parameters such as element types and number of elements which best predict the tank dynamic characteristics, natural frequencies and principal mode shapes. Coupled natural frequencies in sloshing modes were obtained for various tank height-to-diameter ratios, various tank wall thicknesses and various liquid depths. The FEM predictions compared well with literature available experimental and numerical results. A set of FEM options of parameters is recommended for elastic and inelastic analysis of such tanks.

Improving the robustness of reinforced concrete framed structures under sudden column losses

Recent guidelines have addressed provisions to improve structure integrity to accommodate progressive collapse due to failure of an interior support. This article presents novel technique and numerical model to enhance and evaluate reinforced concrete frame robustness to progressive collapse triggered by an interior or edge column failure in any floor. The presented technique enhances the structure robustness to progressive collapse by providing sufficient ductility, continuity, and redundancy. The technique involves placing external unbounded steel cables attached to the continuous beam in each floor at anchorage and deviator locations to bridge over a damaged column of any floor of the frame. The cables transfer the loads above the failed column to the anchorages and deviators that are assumed to perform as rigid arms, which in turn redistribute the loads to adjacent columns. The numerical model computes the frame building progressive collapse robustness using push-down analysis to simulate a column elimination and estimate the effects of cable catenary action on the frame. Two-dimensional reinforced concrete frame of six stories and four bays was adopted in the study. The numerical results demonstrate the prospect of resisting progressive collapse of reinforced concrete structures by implementing the presented technique.