966 research outputs found
Parametric numerical study on service-load deflections of reinforced recycled aggregate concrete slabs and beams based on fib Model Code 2010
This is the peer reviewed version of the following article: [ Tošić, N, Kurama, Y. Parametric numerical study on service‐load deflections of reinforced recycled aggregate concrete slabs and beams based on fib Model Code 2010. Structural Concrete. 2020; 1– 15. https://doi-org.recursos.biblioteca.upc.edu/10.1002/suco.202000015], which has been published in final form at https://onlinelibrary.wiley.com/doi/abs/10.1002/suco.202000015. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingRecycled aggregate concrete (RAC) is entering into structural design codes such as the new Eurocode 2. However, serviceability limit state (SLS) behavior of RAC, especially deflections, can be significantly greater than for natural
aggregate concrete. Proposals for deflection control of RAC exist, but there still have not been significant studies on their implications for SLS design. In this paper, a comprehensive numerical parametric study on the sustained serviceload deflections of reinforced RAC slabs and beams is described. First, a concrete material model for the time-dependent analysis of reinforced concrete structures is described, validated, and calibrated, incorporating fib Model Code 2010 creep and shrinkage models in the OpenSees structural analysis program. Then, service-load deflection analyses are conducted on RAC one-way slabs and T-beams considering the amount of coarse recycled concrete aggregate (RCA), concrete strength class, element height, span, statical system, relative
humidity, and quasi-permanent load-to-design load ratio. The results show that RCA begins to have an appreciable effect on deflections only for coarse aggregate replacement percentages above 25%. At 50% replacement, the maximum spans to satisfy deflection limits can be considerably reduced; however, these reductions are smaller for T-beams and higher class concrete. The results confirm the versatility of the numerical model, as well as the applicability and limitations of RAC in SLS design.This research was funded by the United States Department of State through a Fulbright Visiting Scholar Grant for the project “Optimization of Stratified Recycled Concrete Structures Based on Numerical Analyses and Life Cycle Assessment.” This support is gratefully acknowledged. The authors also express their gratitude for research assistance provided by Dr. Adam Knaack (Schaefer-Inc) and Dr. Seyed Alireza Jalali (Civil Soft Science). Any opinions, findings, conclusions, and/or recommendations in the paper are those of the authors and do not necessarily represent the views of the individuals or organizations acknowledged.Peer ReviewedPostprint (author's final draft
The Voronoi diagram in structural optimisation
In the course of the exploration of computational means in the architectural
design process, in order to investigate more complex, adaptive geometries,
the Voronoi diagram has recently gained some attention, as a structure that is
modular but not repetitive, with potential for a great variety of complex
geometries. The project looks at the Voronoi diagram as a load-bearing
structure, whether its formal potential can be useful for statical optimisation,
and how this optimisation can be facilitated. Hereby, the edges of the Voronoi
polyhedra are regarded as structural members of a statical system, which
then is assessed by structural analysis software.
The project explores different techniques to optimise the cell structure in
regards to its structural properties. It is suggested that the main challenge to
optimise the polyhedra structure lies in the inherent complex relationship
between the Voronoi cell cores and the resulting cell geometry. Cell
geometries emerge from combinatorial properties of the underlying set of
points and so there is no means to manipulate the cells directly.
Results seem to indicate that the emergent Voronoi polyhedra structure,
although difficult to control due to its complex behaviour, can produce a very
specific type of structural order, which is distinctively beneficial for a statical
structure. Certain polyhedra structures which emerge from the Voronoi system
appear to exhibit ‘synergetic’ system behaviour of cooperating tear and
pressure forces, which makes the structure more stable and minimises
deformation. The overall shape of the structure hereby is minimally
transformed. The working principle of the optimised structure lies rather in
how forces are redirected in the system due to its specific topology, rather
than through geometrical transformations of the structure’s overall shape
Analysis of an Orthotropic Deck Stiffened with a Cement-Based Overlay
Over the past years, with increasing traffic volumes and higher wheel loads, fatigue damage in steel parts of typical orthotropic steel bridge decks, has been experienced on heavily trafficked routes. A demand exists to find a durable system to increase the fatigue safety of orthotropic steel bridge decks. A solution might be to enhance the stiffness of the traditional orthotropic bridge deck by using a cement-based overlay. In this paper, an orthotropic steel bridge deck stiffened with a cement-based overlay is analyzed. The analysis is based on nonlinear fracture mechanics, and utilize the finite element method. The stiffness of the steel deck reinforced with an overlay depends highly on the composite action. The composite action is closely related to cracking of the overlay and interfacial cracking between the overlay and underlying steel plate (debonding). As an example, a real size structure, the Farø Bridges located in Denmark, are analyzed. The steel box 1 girders of the Farø Bridges spans 80 meters, and have a depth of 3.5 m, and a width of 19.5 m. The focus of the present study is the top part of the steel box girders, which is constructed as an orthotropic deck plate. Numerous factors can influence the cracking behavior of the cement-based overlay system. Both mechanical and environmental loading have to be considered and effects such as shrinkage, temperature gradients and traffic loading are taken into account. The performance of four overlay materials are investigated in terms of crack widths. Furthermore, the analysis shows that debonding is initiated for a certain crack width in the overlay. The load level where cracking and debonding is initiated depends on the stress-crack opening relationship of the material
Fatigue Limit of Axially Compressed Concrete
An attempt to evaluate analytically the fatigue limit of axially loaded concrete depending upon the load parameters, number of load cycles and static short-term strength is presented. The conventional limit of concrete microcracking statical sustained strength of concrete, curvelinear relationship between fatigue limit and load asymmetry coefficient and straight-line relationship between logarithm of number f load cycles and fatigue limit are involved into a consideration. The proposed method is applicable for the range of load cycles number from 10,000 to an indefinite large
A scenario for the avoidance of dangerous stability situations
Ship Stability is one of the maritime subjects which raises lot of enthusiasm and controversy. As long as ships continue to be lost at sea, the need will exist for a constant reviewing of stability standards and increasing exigency to provide more effective regulations. The present study will be focussed on three main modules. These modules are: technology, regulations and training. Whenever an accident happened at sea people are called to find probable persons or authorities responsible. They concentrated their research on: the ship Master and crew, the national and international regulations and the ship. As far as navigation is concerned, the master will be responsible, from a legal point of view, for any accident or damage caused by his ship to any other things. The problem highlighted here is to know if the ship master get the necessary technical background to confront all kinds of situation he might encounter at sea. This study will be divided into five chapters. The first chapter deals with what we can call the naval architecture heritage. The characteristic conditions of a vessel are the doing of the naval architect. As far as the building is finished the Master will just have to cope with it. The second chapter concerns the factors affecting the ship stability and mostly the marine environment. The marine environment in which the ship will sail for all its life is not always friendly. Chapter three is about how ship Masters use the information given by the shipbuilder in order to find the best conditions in which they can navigate safely and in accordance with the regulations. The case study is only one of various incident that can happen if something goes wrong or somebody makes a mistake. The case of the HERALD OF FREE ENTERPRISE is interesting in the way that it raises many problems and questions involving all the parties concerned. Finally it is time to try to understand what training can and must do in order* to improve the navigation conditions. On other hand we will look at the International Maritime Organization for assistance in upgrading trainers
Parametric study of long-term deflections of reinforced recycled aggregate concrete members according to the fib model code 2010
In this study, a parametric analysis of the deflection calculations of reinforced RAC members is presented. Within the parametric analysis, member support conditions, ambient conditions (influencing shrinkage and creep), reinforcement ratios, and quasi-permanent–to–design load ratios are varied. Through the analysis, the change in deflections is observed against RCA percentage (from NAC to RAC with 100% of coarse RCA) and span-to-effective depth ratio. The results of the analysis enable a clear overview of the variability of the deflections of RAC members relative to NAC.This work was supported by the Ministry for Education, Science and Technology, Republic of Serbia [grant number TR36017] and the SAES project [BIA2016-78742-C2-1-R] of the Spanish Ministerio de Economía, Industria y Competitividad. This support is gratefully acknowledged.Postprint (published version
EXAMINATIONS FOR THE DETERMINATION OF LOAD-CARRYING CAPACITY OF THE BRIDGE OVER THE SEBES-KÖRÖS AT VÉSZTŐ
Load-carrying elements of a 100 years old steel (wrought iron) railway bridge have been
examined. On the basis of in-situ supervision, statical analysis, in-situ and laboratory
measurements conditions of the further service have been determined. The laboratory
fatigue tests verified the safety of the bridge against failure
The Debate about the Structural Behaviour of Gothic Vaults: From Viollet-le-Duc to Heyman
The structural behaviour of the gothic vault will be discussed, focusing in the debate about Viollet-le-Duc’s rational theory (ca. 1850): the “active” ribs support the load of the “passive” masonry of the webs. The debate reached its climax in the 1930’s with the frontal attack mounted by Abraham: the ribs are merely decorative; it is the shell which carries the vault. Other eminent French scholars (Aubert, Focillon), were not so drastic, since Abraham, Viollet’s ideas have been looked with suspicion. The debate is still alive, though in fact was closed by Heyman in the 1960’s, when he formulated the principles of the modern Limit Analysis of masonry structures. Within this new theoretical frame it is a false debate, as it states a question which cannot be answered: what is the “actual” or “true” structural state of a building. This fact, discovered in the 1920’s by Baker, supposes a Copernican change in the approach to the analysis of structures. The debate on gothic vaults may serve to illuminate this approach and its corollaries
Estimation of accumulated creep deformation for structures subjected to cyclic changes of loading in the plastic range
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