Experimental tests have shown that glass exhibits very different strengths when tested under biaxial and uniaxial conditions. This paper presents a study on the effects of biaxial stresses on the notional ultimate strength of glass. The study involved applying the theory of elasticity and finite element analysis of the Griffith flaw in the micro scale. The strain intensity at the tip of the critical flaw is used as the main criterion for defining the limit state of fracture in glass. A simple and robust relationship between the maximum principal stress and the uniaxial stress to cause failure of the same glass specimen
has been developed. The relationship has been used for evaluating the strength values of both new and old annealed glass panels. The characteristic strength values determined in accordance with the test results based on 5% of exceedance are compared with provisions in the ASTM standard.
strength of glass; biaxial effect; strain intensity; finite element
Ilham Nurhuda: Department of Civil and Environmental Engineering, The University of Melbourne, Australia; Department of Civil Engineering, Universitas Diponegoro, Semarang, Indonesia
Nelson T.K. Lam: Department of Civil and Environmental Engineering, The University of Melbourne, Australia
Emad F. Gad: Department of Civil and Environmental Engineering, The University of Melbourne, Australia; Faculty of Engineering & Industrial Sciences, Swinburne University of Technology, Australia
Ignatius Calderone: Calderone and Associates Pty Ltd. Consulting Engineers, Australia
Three-dimensional thermal and mechanical coupled finite element models are proposed to study the structural behaviours of shear connectors under fire. Concrete slabs, steel beams and shear connectors are modelled with eight-noded solid elements, and profiled steel deckings are modelled with eight-noded shell elements. Thermal, mechanical and geometrical nonlinearities are incorporated into the models. With the proper incorporation of thermal and mechanical contacts among steel beams, shear connectors, steel deckings and concrete slabs, both of the models are verified to be accurate after the validation against a series of push-out tests in the room temperature or under the standard fire. Various thermal and mechanical responses are also extracted and observed in details from the results of the numerical analyses, which gives a better understanding of the structural behavior of shear connectors
under elevated temperatures.
shear connector; structural fire engineering; finite element modelling; thermal analysis
Aaron J. Wang: Corporate Technical Management, CapitaLand Management (China) Co. Ltd., Shanghai, P.R. China
In the h-type adaptive analysis, when an element is refined or subdivided, new nodes are added. Among them are the transition nodes which are the corner nodes of the new elements formed by subdivision and, simultaneously, the mid-side nodes of the adjacent non-subdivided elements. To secure displacement compatibility, the slave-node approach in which the DOFs of a transition node are constrained by those of the adjacent nodes had been used. Alternatively, transition elements which possess the transition nodes as active mid-side/-face nodes can be used. For C0 plate analyses, the conventional slave-node constraints and the previously derived ANS transition elements are implemented. In both implementations, the four-node element is the ANS element. With reference to the predictions of the transition elements, the slave-node approach not only delivers erroneous results but also fails the patch test. In this paper, the patch test failure is resolved by developing a set of new constraints with which the slave-node approach surpasses the transition-element approach. The accuracy of the slave-node approach is further improved by developing a hybrid four-node element in which the assumed moment and shear force modes are in strict equilibrium.
K.Y. Sze: Departments of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong, P.R. China
D. Wu: Altair Engineering Software (Shanghai), Suite 1401-06, 248 Yangshupu Road, Shanghai 200082, China
This paper presents the results of an investigation on shear strengthening of RC beams externally reinforced with CFRP composite. A total of six full-scale beams of four CFRP strengthened and two unstrengthened were tested in the absence of internal stirrups in the shear span. The
strengthening configurations contained two styles: discrete uniformly spaced strips and customized wide strips over B-regions. The composite systems provided an increase in ultimate strength as compared to the unstrengthened beams. Among the three layouts that had the same area of CFRP, the highest contribution was provided by the customized layout that targeted the B-regions. A comparative study of the
experimental results with published empirical equations was conducted in order to evaluate the assumed effective strains. The empirical equations were found to be unconservative. Nonlinear finite element (NLFE) models were developed for the beams. The models agreed with test results that targeting the Bregion was more effective than distributing the same CFRP area in a discrete strip style over shear spans. Moreover, the numerical models predicted the contribution of different configurations better than the
This paper investigates the nonlinear analysis of concrete-filled steel composite columns subjected to axial loading to predict the ultimate load capacity and behaviour of the columns. Finite element software LUSAS is used to conduct the nonlinear analyses. The accuracy of the finite element
modelling is verified by comparing the result with the corresponding experimental result reported by other researchers. Nonlinear analyses are done to study and develop different shapes and number of cold-formed steel sheeting stiffeners with various thicknesses of cold-formed steel sheets. Effects of the parameters on the ultimate axial load capacity and ductility of the concrete-filled steel composite columns are examined. Effects of variables such as concrete compressive strength fc and cold-formed steel sheet yield stress fyp on the ultimate axial load capacity of the columns are also investigated. The results are shown in the form of axial load-normalized axial shortening plots. It is concluded from the study that the ultimate axial load capacity and behaviour of the concrete-filled steel composite columns can be accurately predicted by the proposed finite element modelling. Results in this study demonstrate that the ultimate axial load capacity
and ductility of the columns are affected with various thicknesses of steel sheets and different shapes and
number of stiffeners. Also, compressive strength fc of the concrete and yield stress fyp of the cold-formed steel sheet influence the performance of the columns significantly.
Base isolation, having quite simple contents, aims to protect the buildings from earthquakeinduced damages by installing structural components having low horizontal stiffness between substructure and superstructure. In this study, an appropriate base isolation system for 2-D reinforced concrete frame is investigated. For different structural heights, the structural systems of 2, 3 and 4 bays are modeled by applying base isolation systems and results are compared with conventional structural systems. 1999 Marmara earthquake data is used for applying the model by time history method in SAP2000 package. Results of various parameters such as base shear force, structure drift ratio, structure period and superstructure acceleration are discussed for all models.
base isolation; high damping rubber bearing; time history method; 1999 Marmara earthquake
Turan Karabork: Faculty of Engineering, Department of Civil Engineering, Aksaray University, Aksaray, Turkey
This paper illustrates the results of a seismic vulnerability study aimed to derive the fragility
curves for typical Algerian reinforced concrete bridge piers using an analytical approach. Fragility curves express the probability of exceeding a certain damage state for a given ground motion intensity (e.g., PGA). In this respect, a set of 41 worldwide accelerometer records from which, 21 Algerian strong motion records are included, have been used in a non-linear dynamic response analyses to assess the damage indices expressed in terms of the bridge displacement ductility, the ultimate ductility, the cyclic
loading factor and the cumulative energy ductility. Combining the damage indices defined for 5 damage rank with the ground motion indices, the fragility curves for the bridge piers were derived assuming a lognormal distribution.
analytical fragility curves; damage index; bridge piers; strong motion records
Abderrahmane Kibboua and Mounir Naili: National Earthquake Engineering Centre, C.G.S 01, Rue Kaddour RAHIM, BP 252, Hussein Dey, Alger, Algeria
Djillali Benouar: Bab Ezzouar University of Science & Technology, USTHB BP 32, El Alia, Bab Ezzouar, Alger, Algeria
Fouad Kehila: National Earthquake Engineering Centre, C.G.S 01, Rue Kaddour RAHIM, BP 252, Hussein Dey, Alger, Algeria
The progressive collapse phenomenon is generally regarded as dynamic. Due to the impracticality of nonlinear dynamic computations for practitioners, an interest arises for the development of equivalent static pushover procedures. The present paper proposes a methodology to identify such a
procedure for sudden column removals, using energetic evaluations to determine the pushover loads to apply. In a dynamic context, equality between the cumulated external and internal works indicates a vanishing kinetic energy. If such a state is reached, the structure is sometimes assumed able to withstand the column removal. Approximations of these works can be estimated using a static computation, leading to an estimate of the displacements at the zero kinetic energy configuration. In comparison with other
available procedures based on such criteria, the present contribution identifies loading patterns to associate
with the zero-kinetic energy criterion to avoid a single-degree-of-freedom idealisation. A parametric study over a family of regular steel structures of varying sizes uses non-linear dynamic computations to assess the proposed pushover loading pattern for the cases of central and lateral ground floor column failure. The identified quasi-static loading schemes are shown to allow detecting nearly all dynamically detected plastic hinges, so that the various beams are provided with sufficient resistance during the design process. A proper accuracy is obtained for the plastic rotations of the most plastified hinges almost independently of the design parameters (loads, geometry, robustness), indicating that the methodology could be extended to provide estimates of the required ductility for the beams, columns, and beam-column connections.
progressive collapse; 2D frames; pushover loads; non-linear dynamic computations; zero kinetic energy configuration
K. Menchel, T.J. Massart and Ph. Bouillard: Department of Building, Architecture and Town planning (BATir), Universite Libre de Bruxelles (U.L.B) F.D. Roosevelt Av., 50, CP 194/2 – Brussels, Belgium