Cedric D'Mello

Vierendeel Bending Study of Perforated Steel Beams with Various Novel Web Opening Shapes through Nonlinear Finite-Element Analyses

The Vierendeel mechanism is always critical in perforated steel beams with single large web openings, where global shear forces and Vierendeel moments co-exist. Thus far, the main parameters that are known to affect the structural behavior of such beams are the depth of the web opening, the critical opening length of the top tee-section and the web opening area. A comprehensive Finite Element (FE) study of four sizes of perforated steel sections with three different sizes of eleven standard and novel non-standard web opening shapes was undertaken, and their primary structural characteristics presented in detail in order to provide a simple design method for general practice. The different geometric parameters were isolated and studied in order to understand the significance of their effects and in turn advance the knowledge on the performance of perforated steel beams. An elaborate FE model was established, with both material and geometrical non-linearity, allowing load redistribution across the web openings and formation of the Vierendeel mechanism. The reduction of the global shear capacities, due to incorporation of the local Vierendeel moments acting on the top and bottom tee-sections, was obtained directly from the FE analysis. Following that, a comparison of the global shear-moment (V/M) interaction curves of the steel sections with various web opening shapes and sizes was established and empirical generalized V/M interaction curves developed. Moreover, the accurate position of the plastic hinges was determined together with the critical opening length and the Vierendeel parameter. This work has now shown that the shape of the web opening can also significantly affect the structural behavior of perforated beams, as opposed to the equivalent rectangular shape predominately used so far. In addition, the effect of the position of the web opening along the length of the perforated beam was revealed. The importance of the parameters that affect the structural performance of such beams is illustrated. The thorough examination of the computational results has led to useful conclusions and an elliptical form of a web opening is proposed for further study. The outcome of this study is considered as being relevant for practical applications.

Incorporation of fiber-optic sensors in concrete specimens: testing and evaluation

As series of tests has been carried out on the performance of several fiber-optic temperature sensors, operating on the fluorescence lifetime principle using neodymium-doped fiber and configured into ruggedized temperature probes, mounted in a number of different concrete samples. The aim has been to evaluate the performance of probes fitted into concrete specimens to simulate the conditions experienced in structures used in civil applications, such as bridges and dams. A key feature of the investigation was observing the integrity of the sensors under investigation while obtaining temperature data from the device. The results show the sensors operated well from below room temperature to beyond 300/spl deg/C, preserving their integrity under adverse test conditions.

Experimental study and analytical study of push-out shear tests in Ultra Shallow Floor Beams

The Ultra Shallow Floor Beam is a new type of composite floor beam fabricated by welding two highly asymmetric cellular tees together along the web and incorporating a concrete slab between the top and bottom flanges. The unique features of this system are circular and elongated web openings that allow tie-bars, building services and ducts passing through the structural depth of the beam. For the composite beam in bending, the longitudinal shear force is transferred by a unique shear mechanism which results from the special configuration of the beam, and shear connectors, if they are present. The work reported in this paper includes a total of 16 full-scale push-out tests aimed at investigating the longitudinal shear behaviour of these beams and the effects of additional shear connectors. A theoretical analysis was also performed to investigate the failure mechanism of the system.

THE FATIGUE STRENGTH OF GROUTED REPAIRED TUBULAR MEMBERS

The results of fatigue tests performed on bolted split-sleeve grouted clamps of the type used to repair or strengthen tubular members are reported. Sinusoidal tension-compression axial loading was employed; the applied load and the grout age were the variables. The results indicate that the margin of safety against fatigue may not be as great as expected, with some results close to the factored design loads. It is suggested that particular attention should therefore be paid to the fatigue performance of bolted grout-filled clamps in service.

Detailed study of perforated beams with closely spaced novel web opening.

This paper presents a detailed study of the behaviour of perforated steel beams with closely spaced web openings. Seven specimens including two typical cellular beams (i.e. circular web openings) and five perforated beams with novel web opening shapes were tested previously by the authors, to investigate the failure mode and load strength of the web-post between two adjacent web openings. These new novel web opening shapes improve the structural performance of the perforated beams with respect to web-post buckling failure. In addition, the manufacturing procedure of these novel web openings is improved and leads to sustainable design. The effects of web opening spacing/web opening depth of web-posts as well as the web opening depth/web thickness were studied to investigate the stability (slenderness) of the web-post subjected to vertical shear load. In comparison with the conventional cellular beams, significant advantages were obtained.