Ossature (construction) | EPFL Graph Search

vignette|De cette épave, il ne subsiste pratiquement que l’ossature d’acier, la quille, l’étrave et les membrures : le bordé a disparu. vignette|Ossature de la Eames House à Los Angeles. Les remplissage de l'ossature sont en verre et en cemesto. En architecture-construction, l'ossature (de l'italien ossatura, squelette, carcasse, charpente) est un type de structure généralement rigide d'un ensemble ou d'une partie d'ensemble architecturé (l'ossature d'une voûte ou d'un vitrail). En termes de gros œuvre c'est la partie structurelle et porteuse d'un vaisseau ou d'un édifice (la bâtisse). Définition L'ossature, la bâtisse, est constituée en pierre, brique, béton, métal ou bois. C'est le support rigide en gros œuvre, ce sont les éléments de l'ouvrage qui assurent la stabilité et cette structure est réceptrice du remplissage en parois pour constituer l'abri. La partie située au-dessus du sol est la superstructure, la partie enterrée dans le sol est l’infrastructure. Cette struct

Comportement dynamique des dalles de roulement des ponts en béton sollicités par le trafic routier

The management of a network of existing road bridges involves interventions in order to maintain safety and the priority of these interventions is often determined by safety criteria. During the evaluation of safety, the dynamic effect of traffic actions is considered using equivalent static loads determined by multiplying the effect calculated using traffic load models by a dynamic amplification factor. During the evaluation of a deck slab, the application of inappropriate dynamic amplification factors could have significant financial implications, all the more since the local dynamic effects of overloaded trucks are determinant for this type of structural element. Dynamic amplification factors defined in codes have usually been derived from the measurement of global traffic action effects in the main structural elements of bridges. Unfortunately, local dynamic effects in deck slabs have not been studied in detail until now. A better understanding of the dynamic behaviour of deck slabs will lead to the definition of more accurate dynamic amplification factors and avoid the use of values that are too conservative. The behaviour of deck slabs of six typical Swiss highway bridges has been simulated in order to study their dynamic response during the passage of trucks. The structural arrangement of the deck slab was different for each of the six bridges. A parametric study was based on the simulation of various scenarios involving the passage of trucks for various combinations of speed, path and road surface roughness. Deck slab response was obtained by numerical simulation based on models of the bridge, truck and road surface. This system was resolved using a prediction - correction algorithm that considers the dynamic interaction between a bridge and trucks. Dynamic amplification factors were subsequently calculated from strains and deflections obtained from independent static and dynamic simulations. The simulation of numerous scenarios enabled the evaluation of the influence of different parameters on the dynamic response of a deck slab: The road surface roughness was found to be one of the most important parameters, with an increase in roughness leading to an increase in dynamic amplification factors. An overloaded truck produces a lower dynamic amplification factor in a deck slab than an empty truck. The truck speed influences the dynamic interaction, but a clear relationship between speed and dynamic amplification factor could not be identified. The maximum dynamic amplification factor does not vary significantly from one point to another over a deck slab in a girder bridge. The structural arrangement of a deck slab in a girder bridge has little influence on dynamic amplification factors. Overall, the different deck slabs on the girder bridges studied were all equally sensitive to the dynamic effects of road traffic. In many cases considered for the framed slab bridge, the maximum dynamic amplification factor was found to occur over the supports. For such bridges, the sensitivity of the deck slab to the dynamic effects of road traffic is not uniform. Finally, two approaches to evaluating deck slabs of existing road bridges are proposed. The first approach is only applicable in certain situations and involves a simplified evaluation using an updated traffic load model and a dynamic amplification factor. In situations where a simplified evaluation is not applicable, the second approach is to evaluate a deck slab using numerical or experimental analyses.

EPFL1999

Influence of bond and anchorage conditions of the shear reinforcement on the punching strength of RC slabs

Fabio Brantschen

Reinforced concrete flat slabs constitute one of the most common and efficient modern construction methods. The design of such structural system might be governed by a brittle failure in the vicinity of the slab-column connection associated to punching shear. The arrangement of transverse reinforcement in the critical zone increases both the strength and the deformation capacity of the slab-column connection. Recent advances on the understanding of the punching phenomena lead nowadays to a better approach of their differences in efficiency. One of the main parameters identified as governing for the performance of this specific reinforcement is the quality of its anchorage and bond, influencing the development of cracks in the shear-critical region. Such characteristic is generally defined through force-slip relationships and is strongly influenced by the local state of stress and strain. Although the activation of reinforcement often takes place within already cracked concrete for many structural members, the conventional approaches supporting code formulations are still almost exclusively based on tests performed on uncracked specimens. In the coming years, an increased emphasis should be placed on the study of the performance of reinforcing details in such severe conditions, with the aim to improve the knowledge of this rather underrated but critical problematic. Several experimental works were thus conducted in the frame of this thesis on the role of the anchorage of the transverse reinforcement in punching shear phenomenon. A programme of pull-out tests on actual detailing solutions was performed in cracked conditions similar to those developing in slabs at the vicinity of the columns. The results highlighted notable differences amongst the evaluated types of anchorages, confirming therefore the various levels of performance observed in punching tests. The activation of this specific reinforcement is investigated through tests on full-scale slab specimens provided with extended measurements of the force and crack openings. The use of an innovative reinforcing setup allowed to track the concrete and steel contributions in the punching phenomenon, providing the experimental information required to validate the main assumptions of the Critical Shear Crack Theory for the failure mode within the shear-reinforced area. Observations on straight bars with in-plane cracking supported the development of analytical formulations to evaluate the reduction of performance âin terms of strength and stiffnessâ for various anchorage details by analogous considerations to the aggregate interlock approaches. The model is validated through a refined numerical method and the main test results available from literature. Such developments can be partially used within the frame of the Critical Shear Crack Theory, which calculates the contribution of the shear reinforcement in the punching strength âfor the failure mode of interestâ with a physical model of activation for the transverse elements. The latter contains a number of general assumptions âperfect bond and anchorage conditions, simplified crack kinematicsâ which can be improved and refined on the basis of the experimental results of the present research. Proposals are formulated to take into account in the existing model a more realistic activation of the transverse reinforcement in the slab during punching, and thus to improve the understanding and the predictions associated to this failure mode.

EPFL2016

A 3D printed bio-composite removable connection system for bamboo spatial structures

Romain Pascal T van Wassenhove, Anastasios Vassilopoulos

A 3D printed bio-composite removable connection system for bamboo space structures is introduced in this paper. The system consists of a removable clipping connection for raw bamboo structures, adapted to the European market. The use of parametric design and 3D printing enables to have both design and production processes adapted to the non-uniform bamboo culm dimensions, while being standardisable. The resulting design possibilities are very large due to the high adaptability of the whole process. The efficiency of the introduced connection system has been validated experimentally. Standardized specimens of the bio-composite material, a connection detail (clip), and a structural component were examined experimentally to validate the design. A pyramidal structure made of bamboo culms of 30 mm of diameter and 4 mm in thickness was able to sustain a load of 7 kN in compression, proving the relevance of the proposed connection system. A finite element model was developed to model the clip behaviour and successfully compared to the experimental results.

2021

Comportement dynamique des dalles de roulement des ponts en béton sollicités par le trafic routier

EPFL1999

Influence of bond and anchorage conditions of the shear reinforcement on the punching strength of RC slabs

Fabio Brantschen

EPFL2016