Abstract
The deformation and dynamic behavior mechanism of submerged shell-like lattice structures with membranes are in principle of a non-conservative nature as circulatory system under hydrostatic pressure and disturbance forces of various types, existing in a marine environment. This paper deals with a characteristic analysis on quasi-periodic and chaotic behavior of a circular arch under follower forces with small disturbances. The stability region chart of the disturbed equilibrium in an excitation field was calculated numerically. Then, the periodic and chaotic behaviors of a circular arch were investigated by executing the time histories of motion, power spectrum, phase plane portraits and the Poincare section. According to the results of these studies, the state of a dynamic aspect scenario of a circular arch could be shifted from one of quasi-oscillatory motion to one of chaotic motion. Moreover, the correlation dimension of fractal dynamics was calculated corresponding to stochastic behaviors of a circular arch. This research indicates the possibility of making use of the correlation dimension as a stability index.
Abstract
The capacity of tubular truss chords subjected to concentrated reaction forces in the vicinity of the open end (i.e., the bearing region) is not directly treated by existing design specifications; although capacity equations are promulgated for related tubular joint configurations. The lack of direct treatment of bearing capacity in existing design specifications seems to represent an unsatisfactory situation given the fact that connections very often control the design of long-span tubular structures comprised of members with slender cross-sections. The case of the simple-span overhead highway sign truss is studied, in which the bearing reaction is applied near the chord end. The present research is aimed at assessing the validity of adapting existing specifications?capacity equations from related cases so as to be applicable in determining design capacity in tubular truss bearing regions. These modified capacity equations are subsequently used in comparisons with full-scale experimental results obtained from testing carried out at the University of Pittsburgh.
Key Words
side wall bearing; tubular member bearing; long-span trusses; bearing limit state; nonlinear finite element analysis; circular HSS.
Address
Department of Civil & Environmental Engineering, University of Pittsburgh, Pittsburgh, rnPennsylvania, 15261, USA
Abstract
This paper proposes a model for the analysis of the construction sequences of steel-concrete composite decks in which the slab is cast-in-situ for segments. The model accounts for early age shrinkage, such as thermal and endogenous shrinkage, drying shrinkage, tensile creep effects and the complex sequences of loading due to pouring of the different slab segments. The evolution of the structure is caught by suitably defining the constitutive relationships of the concrete and the steel reinforcements. The numerical solution is obtained by means of a step-by-step procedure and the finite element method. The proposed model is then applied to a composite deck in order to show its potential.
Key Words
steel-concrete composite decks; fractionated casting; construction sequence; shrinkage and creep effects; finite element method.
Address
Luigino Dezi and Fabrizio Gara; Dept. of Architecture, Construction and Structures, Marche Polytechnic Univ., via Brecce Bianche 60131, Ancona, ItalyrnGraziano Leoni; PROCAM, Univ. of Camerino, Viale della Rimembranza, 63100, Ascoli Piceno, Italy
Abstract
In this paper, a cyclic mechanical model is presented to simulate the behaviour of top and seat with web angle beam-to-column connections. The introduced mechanical model is compared with Eurocode 3 Annex J, its extension, and with experimental data. To have a better insight regarding the actual response of the joints, available results of the experiments, carried out on full-scale top and seat angle joints under monotonic and cyclic loading, are first considered. Subsequently, a finite element model of the test setup is developed. The application of the proposed model, its comparisons with the experimental curves and with the Eurocode 3 Annex J and with its modification, clearly show the excellent quality of the model proposed.
Key Words
steel structures; bolted connections; mechanical model; Eurocode 3; Annex J; finite element model; partial strength.
Address
Dept. of Mechanics and Materials, University of Reggio Calabria, Italy
Abstract
Current fire design codes for determining the temperature within the structural elements that form part of a complete building are based on isolated member tests subjected to the standard fire. However, the standard time-temperature response bears little relation to real fires and doesn\'t include the effects of differing ventilation conditions or the influence of the thermal properties of compartment linings. The degree to which temperature uniformity is present in real compartments is not addressed and direct flame impingement may also have an influence, which is not considered. It is clear that the complex thermal environmental that occurs within a real building subject to a natural fire can only be addressed using realistic full-scale tests. To study global structural and thermal behaviour, a research project was conducted on the eight storey steel frame building at the Building Research Establishment\'s Cardington laboratory. The fire compartment was 11 m long by 7 m wide. A fire load of 40 kg/m2 was applied together with 100% of the permanent actions and variable permanent actions and 56% of live actions. This paper summarises the experimental programme and presents the time-temperature development in the fire compartment and in the main supporting structural elements. Comparisons are also made between the test results and the temperatures predicted by the structural fire Eurocodes.
Key Words
fire design; full-scale tests; steel and composite structures; temperature.
Address
Frantisek Wald; Dept. of Steel and Timber Structures, CTU Prague, Faculty of Civil Engineering, Th?urova 7, 166 29 Praha 6, Czech RepublicrnMagdalena Chladna; Dept. of Civil Engineering, Technical Univ., Bratislava, Slovak RepublicrnDavid Moore; BCSA-British Constructional Steelwork Association, London, UKrnAldina Santiago; Dept. of Civil Engineering, Univ. of Coimbra, Polo II - Pinhal de Marrocos, 3030-290 Coimbra, Portugal rnTom Lennon; Building Research Establishment, Garston, UK
