Push-out tests and analytical study of shear transfer mechanisms in composite shallow cellular floor beams

The shear transferring mechanisms of composite shallow cellular floor beams are different with the conventional headed shear studs, and have not been investigated previously. This paper presents the experimental and analytical studies of the shear transferring mechanisms with the aims to provide information on their shear resistance and behaviour. The composite shallow cellular floor beam is a new type of composite floor beam that consists of an asymmetric steel section with circular web openings and concrete slabs incorporated between the top and bottom flange. The unique feature of the web openings allows tie-bars, building services and ducting to pass through the structural depth of the floor beam, creating an ultra-shallow floor beam structure. The shear connection of the composite shallow cellular floor beam is formed innovatively by the web openings, as the in-situ concrete passes through the web openings may or may not include the tie-bars or ducting to transfer the longitudinal shear force. In total, 24 push-out tests were carried out to investigate the shear connection under the direct shear force. The effect of loading cycles on the shear connection was also investigated. The failure mechanisms of the shear connection were extensively studied, which had led to the development of a calculation method of shear resistance for the shear connection

Numerical investigation of the resistance of precast RC pinned beam-to-column connections under shear loading

In precast technology, the effective design and construction is related to the behaviour of the connections between the structural members in order to cater for all service, environmental and earthquake load conditions. Therefore, the design and detailing of the connections should be undertaken consistently and with awareness of the desired structural response. In the research presented herein an analytical expression is proposed for the prediction of the resistance of precast pinned connections under shear monotonic and cyclic loading. The proposed formula addresses the case where the failure of the connection occurs with simultaneous flexural failure of the dowel and compression failure of the concrete around the dowel, expected to occur either when (a) adequate concrete cover of the dowels is provided (d > 6 D) or (b) adequate confining reinforcement (as defined in the article) is foreseen around the dowels in the case of small concrete covers (d < 6 D). The expression is calibrated against available experimental data and numerical results derived from a nonlinear numerical investigation. Emphasis is given to identifying the effect of several parameters on the horizontal shear resistance of the connection such as: the number and diameter of the dowels; the strength of materials (concrete, grout, steel); the concrete cover of the dowels; the thickness of the elastomeric pad; the type of shear loading (monotonic or cyclic); the pre-existing axial stress in the dowels; and the rotation of the joint. In addition, recommendations for the design of precast pinned beam-to-column connections are given, especially when the connections are utilised in earthquake resistant structures

Fire analysis of steel frames with the use of artificial neural networks

The paper presents an alternative approach to the modelling of the mechanical behaviour of steel frame material when exposed to the high temperatures expected in fires. Based on a series of stress-strain curves obtained experimentally for various temperature levels, an artificial neural network (ANN) is employed in the material modelling of steel. Geometrically and materially, a non-linear analysis of plane frame structures subjected to fire is performed by FEM. The numerical results of a simply supported beam are compared with our measurements, and show a good agreement, although the temperature-displacement curves exhibit rather irregular shapes. It can be concluded that ANN is an efficient tool for modelling the material properties of steel frames in fire engineering design studies. (c) 2007 Elsevier Ltd. All rights reserved

Post-fire Behaviour of Innovative Shear Connection for Steel-Concrete Composite Structures

YesSteel-concrete composite structures are commonly used in buildings and bridges because it takes advantage of tensile strength of steel and compressive strength of concrete. The two components are often secured by shear connectors such as headed studs to prevent slippage and to maintain composite action. In spite of its popularity, very little research was conducted on steel-concrete composites particularly on headed stud shear connectors in regards to its post-fire behaviour. This research investigates the post-fire behaviour of innovative shear connectors for composite steel and concrete. Three type of connectors were investigated. They are headed stud shear connectors, Blind Bolt 1 and Blind Bolt 2 blind bolts. Push-out test experimental studies were conducted to look at the behaviour and failure modes for each connector. Eighteen push tests were conducted according to Eurocode 4. The push test specimens were tested under ambient temperatures and post fire condition of 200˚C, 400˚C and 600˚C. The results in ambient temperature are used to derive the residual strength of shear connectors after exposing to fire. Findings from this research will provide fundamental background in designing steel-concrete composites where there is danger of fire exposure

Assessment of the effectiveness of the embedded through-section technique for the shear strengthening of RC beams

Embedded Through-Section (ETS) technique is a relatively recent shear strengthening strategy for reinforced concrete (RC) beams, and consists on opening holes across the depth of the beam’s cross section, with the desired inclinations, where bars are introduced and are bonded to the concrete substrate with adhesive materials. To assess the effectiveness of this technique, a comprehensive experimental program composed of 14 RC beams was carried out, and the obtained results confirm the feasibility of the ETS method and revealed that: (i) inclined ETS strengthening bars were more effective than vertical ETS bars, and the shear capacity of the beams has increased with the decrease of the spacing between bars; (ii) brittle shear failure was converted in ductile flexural failure, and (iii) the contribution of the ETS strengthening bars for the beam shear resistance was limited by the concrete crushing or due to the yielding of the longitudinal reinforcement. The applicability of the ACI 318 (2008) and Eurocode 2 (2004) standard specifications for shear resistance was examined and a good agreement between the experimental and analytical results was obtained.The study reported in this article is part of the research project 'DURCOST', PTDC/ECM/105700/2008, supported by FCT. The authors wish to acknowledge the support provided by the 'Casais', Secil (Unibetao, Braga) and Sika Portugal Companies. The first author acknowledges the National Council for Scientific and Technological Development (CNPq), Brazil, for financial support for scholarship (GDE 200953/2007-9)

Numerical model for the non-linear dynamic analysis of multi-storey structures with semi-rigid joints with specific reference to the Algerian code

The current paper aims at investigating the dynamic response of rigid and semi-rigid connections of steel structures built in high seismic areas. A nonlinear dynamic analysis model, which is an extension to the simplified and direct mechanical model used in the static analysis, is proposed and discussed. The novelty of the model consists in the introduction of a bar element with semi-rigid joint as a single element without the need to discretise it (i.e. without a finite element mesh) in the program where non-linearity is considered in the flexibility factor of the stiffness matrix. The model developed is validated through application to examples of steel frames with different types of connections under dynamic forces. The results obtained were very satisfactory. This work is motivated by the need for the revision of the Algerian seismic code (RPA99v2003) which does not yet consider provisions for the design of structures with semi-rigid joints. Based on the results of the study carried out on a multi-storey structure with different types of joints subjected to seismic loading, it can be seen that the safety justifications recommended by Algerian regulations RPA99 in terms of relative displacements as well as the dimension of the seismic joint prove to be too conservative compared to those by Eurocode 8

On the dynamics of rocking motion of single rigid–block structures

This paper describes the behavior of single rigid-block structures under dynamic loading. A comprehensive experimental investigation has been carried out to study the rocking response of four blue granite stones with different geometrical characteristics under free vibration, and harmonic and random motions of the base. In total, 275 tests on a shaking table were carried out in order to address the issues of repeatability of the results and stability of the rocking motion response. Two different tools for the numerical simulations of the rocking motion of rigid blocks are considered. The first tool is analytical and overcomes the usual limitations of the traditional piecewise equations of motion through a Lagrangian formalism. The second tool is based on the discrete element method (DEM), especially effective for the numerical modeling of rigid blocks. A new methodology is proposed for finding the parameters of the DEM by using the parameters of the classical theory. An extensive comparison between numerical and experimental data has been carried out to validate and define the limitations of the analytical tools under study.Ecoleader Group 4Fundação para a Ciência e a Tecnologia (FCT) -: SFRH/BPD/17449/2004, SFRH/BD/9014/200

Prediction of self-compacting concrete elastic modulus using two symbolic regression techniques

yesThis paper introduces a novel symbolic regression approach, namely biogeographical-based programming (BBP), for the prediction of elastic modulus of self-compacting concrete (SCC). The BBP model was constructed directly from a comprehensive dataset of experimental results of SCC available in the literature. For comparison purposes, another new symbolic regression model, namely artificial bee colony programming (ABCP), was also developed. Furthermore, several available formulas for predicting the elastic modulus of SCC were assessed using the collected database. The results show that the proposed BBP model provides slightly closer results to experiments than ABCP model and existing available formulas. A sensitivity analysis of BBP parameters also shows that the prediction by BBP model improves with the increase of habitat size, colony size and maximum tree depth. In addition, among all considered empirical and design code equations, Leemann and Hoffmann and ACI 318-08’s equations exhibit a reasonable performance but Persson and Felekoglu et al.’s equations are highly inaccurate for the prediction of SCC elastic modulus