1,721,575 research outputs found
Comparison between rocking analysis and kinematic analysis for the dynamic out-of-plane behavior of masonry walls
No full textThis paper provides a contribution to the rocking analysis of masonry walls by making a comparison with the kinematic analysis suggested by the Italian code. It is shown that the latter approach is generally overconservative and therefore potentially inappropriate for historic buildings, where rehabilitation can be expensive and can affect their cultural value. The equation of motion given by the Housner formulation, corresponding to the movement of a rigid block, is here modified to account for different boundary conditions at different heights of the wall. These boundary conditions or horizontal restraints can represent vaults, transverse walls, or retrofitting devices such as steel tie-rods. A systemic analysis of walls having different dimensions and slenderness is performed, and the results from the Italian code and rocking analysis are compared. Finally, the improvement in the response offered by retrofitting devices is discussed in terms of reduction of amplitude ratio
A finite element model for long-term analysis of timber-concrete composite beams
No full textThe paper presents a finite element model for studying timber-concrete composite beams under long-term loading. Both deformability of connection system and rheological behaviour of concrete, timber and connection are fully considered. The creep of component materials and the influence of moisture content on the creep of timber and connection, the so-called “mechano-sorptive” effect, are evaluated by means of accurate linear models. The solution is obtained by applying an effective step-by-step
procedure in time, which does not require storing the whole stress history in some points in order to account for the creep behaviour. Hence the proposed method is suitable for analyses of composite beams subjected to complex loading and thermo-hygrometric histories. The possibility to accurately predict the long-term response is then shown by comparing numerical and experimental results for different tests
"Experimental behaviour of a full-scale timber-concrete composite floor with mechanical connectors"
No full textThe timber-concrete composite (TCC) beam is a construction technique that can be used for upgrading of existing timber floors without the need of demolition. This possibility has been investigated through full-scale tests on a 6-storey experimental building with light-frame timber walls and platform construction, where the existing timber floor for
domestic use was upgraded for reuse as an office building. The acoustic flooring was replaced with a 60 mm lightweight concrete slab, connected to the existing joists with inclined shear connectors (SFS screws) to form the TCC floor. The floor and environmental conditions were monitored during the
concrete pouring and hardening, and during the
application of the live load. Two different types of construction, propped and unpropped, were compared,
and an extensive experimental investigation was performed on material components (lightweight concrete,
timber, and connection system) with the aim to fully characterise the behaviour under short- and long-term
loading. The unpropped floor was then tested to failure under monotonic loading, and two different boundary conditions, namely the actual joist-to-wall joint and a perfectly pinned support, were investigated. An advanced FE model was validated on the test results and used to predict the deflection in the long-term.
The composite floor achieved the target stiffness and the design load for satisfying ultimate and serviceability limit states for office loading in the UK. The actual joist-to-wall restraint was characterized by a low degree of fixity, however it produced
early longitudinal crack formation in the proximity of
the support. The final collapse of the floor as a whole occurred progressively under increasing load after
failure for fracture in tension of an individual joist. The higher drying shrinkage of lightweight concrete raised the deflection during concrete curing and hardening
A finite element model for long-term analysis of timber-concrete composite beams
No full textThe paper presents a finite element model for studying timber-concrete composite beams under long-term loading. Both deformability of connection system and rheological behaviour of concrete, timber and connection are fully considered. The creep of component materials and the influence of moisture content on the creep of timber and connection, the so-called “mechano-sorptive” effect, are evaluated by means of accurate linear models. The solution is obtained by applying an effective step-by-step
procedure in time, which does not require storing the whole stress history in some points in order to account for the creep behaviour. Hence the proposed method is suitable for analyses of composite beams subjected to complex loading and thermo-hygrometric histories. The possibility to accurately predict the long-term response is then shown by comparing numerical and experimental results for different tests
Numerical and analytical assessment of the buckling behaviour of Blockhaus log-walls under in-plane compression
No full textBlockhaus structural systems are commonly obtained by assembling multiple timber logs, by stacking them horizontally on the top of one another. Although based on simple mechanisms of ancient origins, the structural behaviour of Blockhaus systems under well-defined loading and boundary conditions is complex to predict. The paper focuses on the assessment of the typical buckling behaviour and resistance of vertically compressed timber log-walls. The effects of various mechanical and geometrical variables such as possible
load eccentricities and initial curvatures, openings (e.g. doors or windows), fully flexible or in-plane rigid inter-storey floors are investigated by means of detailed finite-element (FE) numerical models. These FE
models were first validated on test results of past buckling experiments performed on scaled log-wall
specimens, as well as on recent buckling experiments carried out on full-scale timber log-walls, demonstrating the capability to appropriately describe the effective interaction between timber logs and to correctly
predict the expected buckling failure mechanisms and ultimate resistance for the log-walls that were investigated. Comparisons with analytical solutions partly derived from classical theory of plate buckling and column buckling are also presented and critically discussed, in order to assess the applicability of these existing formulations – although specific for fully monolithic and isotropic plates and columns – to Blockhaus structural systems. A closed-form solution is finally proposed as a simplified design buckling method for timber log-walls under in-plane compression
The reduced cross-section method for the evaluation of the fire resistance of timber members - Discussion and determination of the zero-strength layer
No full textThe reduced cross-section method (RCSM) is included in Eurocode 5 (EN-1995-1-2) for the design of timber members in fire conditions. The method considers the strength and stiffness reduction beneath the charred layer by adding an additional depth (known as the ‘zero-strength’ layer) to the charring depth. The zero strength layer is one of the key parameters for the fire design of timber members. Recently, some concerns have been raised that the zero-strength layer might be nonconservative
in some applications. This paper presents the background to the RCSM, followed by a short discussion on the mechanical assumptions, simplifications and possible limitations of the method itself. Further, it discusses determination of the
zero-strength layer thickness for members in bending, tension and compression, and
provides guidelines on the use of standard experimental tests to determine this quantity. For demonstration of the determination procedure, the results of fire tests in bending, tension and compression were analysed following the described procedure. Results show that the zero-strength layer exceeds the value used in practice, indicate that the method of Eurocode 5 may be non-conservative and should be revised
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