Finite element study of hyperstructure systems with modular light‐frame construction in high‐rise buildings

To answer both the growth of the world's urban population and the climate changes, new structural systems with high prefabrication levels and renewable materials need to be developed. A novel structural system that could enable the use of modular light‐frame construction in high‐rise buildings was modeled and analyzed. This system was achieved by having a hyperstructure carrying the loads of four‐story light‐frame superposed substructures. Two 20‐story hyperstructures, one using glulam and another one using reinforced concrete, were designed according to the 2015 National Building Code of Canada and compared. A simplified model for the light‐frame modules according to the CSA O86‐19 was proposed. The interaction between both systems and the impact on the substructures were analyzed. The results of the response spectrum analysis and dynamic wind analysis show that, with a glulam hyperstructure, modules could be connected to the columns and the floors or only to the floors. With a concrete hyperstructure, the modules must be connected to the columns and the cores. For both systems, the design of shearwalls on the short side of the modules is governed by the lateral deformation imposed by seismic forces, while the design of shearwalls on the long side of the modules is governed by the vertical deformation of the primary beams under gravity loads. Standard shearwall assemblies are sufficient to resist the shear induced by gravitational, wind and seismic loads. The analysis indicates that the system could be viable, but more research should be especially performed on the connections between the substructures and the hyperstructure

Fatigue analysis-based numerical design of stamping tools made of cast iron

This work concerns stress and fatigue analysis of stamping tools made of cast iron with an essentially pearlitic matrix and containing foundry defects. Our approach consists at first, in coupling the stamping numerical processing simulations and structure analysis in order to improve the tool stiffness geometry for minimizing the stress state and optimizing their fatigue lifetime. The method consists in simulating the stamping process by considering the tool as a perfect rigid body. The estimated contact pressure is then used as boundary condition for FEM structure loading analysis of the tool. The result of this analysis is compared with the critical stress limit depending on the automotive model. The acceptance of this test allows calculating the fatigue lifetime of the critical zone by using the S–N curve of corresponding load ratio. If the prescribed tool life requirements are not satisfied, then the critical region of the tool is redesigned and the whole simulation procedures are reactivated. This method is applied for a cast iron EN-GJS-600-3. The stress-failure (S–N) curves for this material is determined at room temperature under push pull loading with different load ratios R0σmin/σmax0−2, R0−1 and R00.1. The effects of the foundry defects are determined by SEM observations of crack initiation sites. Their presence in tested specimens is associated with a reduction of fatigue lifetime by a factor of 2. However, the effect of the load ratio is more important

Review of state of the art of dowel laminated timber members and densified wood materials as sustainable engineered wood products for construction and building applications

Copyright © 2019 The Authors. Engineered Wood Products (EWPs) are increasingly being used as construction and building materials. However, the predominant use of petroleum-based adhesives in EWPs contributes to the release of toxic gases (e.g. Volatile Organic Compounds (VOCs) and formaldehyde) which are harmful to the environment. Also, the use of adhesives in EWPs affects their end-of-life disposal, reusability and recyclability. This paper focusses on dowel laminated timber members and densified wood materials, which are adhesive free and sustainable alternatives to commonly used EWPs (e.g. glulam and CLT). The improved mechanical properties and tight fitting due to spring-back of densified wood support their use as sustainable alternatives to hardwood fasteners to overcome their disadvantages such as loss of stiffness over time and dimensional instability. This approach would also contribute to the uptake of dowel laminated timber members and densified wood materials for more diverse and advanced structural applications and subsequently yield both environmental and economic benefits.Interreg North-West Europe (NWE) funded by the European Regional Development Fund (ERDF) supporting the project (Towards Adhesive Free Timber Buildings (AFTB) - 348)

Mechanical behaviour and 3D stress analysis of multi-layered wooden beams made with welded-through wood dowels

This paper presents experimental and numerical investigations on multi-layered timber beams using welded-through wood dowels in place of traditional poly(vinyl acetate) (PVAc)-adhesives (or metallic nails). Four-layer beams were constructed with varying numbers of dowels, in each, and then loaded using four-points bending tests to evaluate the mechanical performance of these beams. The practical difficulties encountered in constructing deeper multi-layer beams are discussed and possible solutions which have been employed for the purpose of this work, and proved successful are presented. In order to investigate thoroughly the full potential of multi-layered beams with a very limited number of experimental studies, a 3D FE model has been presented, validated against experimental results and then used to study some influential parameters. The results showed that a reasonable bending stiffness of multi-layered beams is achievable with a good combination of material and geometric parameters.Deposited by bulk importSB. 19/02/201

Modélisation et optimisation du comportement mécanique des outils d'emboutissage stratifiés précontraints par vissage :

In sheet metal stamping, the forming tools play a crucial role and the global cost of stamped parts is highly influenced by the cost of the tools, depending on the production volume. For low volume or for rapid prototyping, stamping tools can be made by an assemblage of steel sheets or layers, assembled by different techniques (glue, screws, bolts...). Each layer is obtained by laser cutting and micro-milling (as in the Stratoconception¯ approach). The present work deals with the design of stamping tools obtained by the assemblage of plates in layers and fixed by screws. We propose and validate a numerical approach for the 3D stress analysis of the multilayered tools. The final original objective is to optimize the layered stamping tools assembled by screws. In order to avoid the great difficulties involved for the numerical simulation of the stamping process taking into account deformable and layered tools assembled by screws, we develop a simplified approach based on two steps, based on the decoupling of the non-linearities of the stamping process and the linear elastic analysis of the deformable tools. Several examples are considered with multilayered steel tools assembled by screws and produced by the Stratoconception¯ approach. We finally proposed an optimization procedure of the screw positions as an attempt to improve the design and the strength of the layered tools by increasing the life duration of the screwsDans le contexte de l'emboutissage des tôles, les outils jouent un rôle crucial et le coût global d'une pièce emboutie est fortement influencé par le coût des outils, dépendant du volume de production. Pour la petite et moyenne série ou pour le prototypage rapide, les outils d'emboutissage peuvent être fabriqués par un empilement de strates métalliques, assemblés par diverses techniques (collage, vissage, boulonnage...). Chaque strate est obtenue par découpe laser et micro-fraisage (comme dans la Stratoconception¯). Ce travail, original en ce qui concerne les outils d'emboutissage, consiste à proposer une méthodologie numérique permettant l'analyse du comportement tridimensionnel des outils d'emboutissage, en particulier les outils prototypes fabriqués par empilement successif de couches métalliques (strates) et assemblés par vissage, l'objectif final étant de pouvoir dimensionner, voire optimiser leurs conception, notamment le système d'assemblages des strates par des vis précontraintes. Afin de surmonter les difficultés qu'implique la simulation de l'emboutissage en considérant les outils déformables (maillages, temps CPU...) ainsi que celles liées à l'aspect stratifié des outils, nous proposons et nous développons une approche simplifiée en deux étapes qui a l'avantage de découpler les non-linéarités de l'emboutissage et l'analyse linéaire élastique des outils déformables. La démarche a été appliquée avec succès dans le cadre des outils stratifiés assemblés par vissage (obtenus par Stratoconception¯). Dans ce contexte, nous avons également proposé une procédure d'optimisation des positions des vis précontraintes afin d'améliorer la conception et la tenue mécanique des outils stratifiés, notamment en augmentant la durée de vie des vis précontrainte

The optimal design of sheet metal forming processes: application to the clinching of thin sheets

The production of high-strength clinched joints is the ultimate goal of the manufacturing industry. The determination of optimum tool shapes in the clinch forming process is needed to achieve the required high strength of clinched joints. The design of the tools (punch and die) is crucial since the strength of the clinched joints is closely related to the tools geometry. To increase the strength of clinched joints, an optimisation procedure using the response surface methodology, based on an adaptive moving target zone, is presented. The cost function studied here is defined in terms of the maximum value of the tensile force computed during the simulation of the sheets separation. Limitations on the geometrical parameters due to feasibility issues are also taken into account. The kriging interpolation is used to provide an approximation to the optimisation problem and to build the response surfaces