Nauki Techniczne

Archives of Civil Engineering

Zawartość

Archives of Civil Engineering | 2011 | No 3 |

Abstrakt

This study investigates the use of steel fibers and hybrid composite with a total fibers content of 2% on the high strength flowing concrete and determines the density, compressive strength, static modulus of elasticity, flexural strength and toughness indices for the mixes. The results show that the inclusion of more than 0.5% of palm fibers in hybrid fibers mixes reduces the compressive strength. The hybrid fibers can be considered as a promising concept and the replacement of a portion of steel fibers with palm fibers can significantly reduce the density, enhance the flexural strength and toughness. The results also indicates that the use of hybrid fibers (1.5 steel fibers + 0.5% palm fibers) in specimens increases significantly the toughness indices and thus the use of hybrid fibers combinations in reinforced concrete would enhance their flexural toughness & rigidity and enhance their overall performances.

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Autorzy i Afiliacje

Eethar Thanon Dawood
Mahyuddin Ramli

Abstrakt

The proper designing of PV systems requires the use of advanced building energy simulation techniques. It allows to design the best position of the PV array, as well as the right quantity of produced energy in different cases. On the other hand the PV efficiency is not only a constant value but changes according to temperature and solar radiation. This paper is devoted to estimate the simultaneous effect of both weather factors on PV efficiency. The task was achieved by numerical simulation and ESP-r software. Computer simulations have been carried out with the use of the Typical Meteorological Year data for Warsaw (52°N 21°E). The greatest influence of temperature on the efficiency of solar energy conversion was observed for crystalline silicon cells. The influence of the boundary conditions assumed in the study is ignored for amorphous silicon cells in the summer period and regardless of the material type in the winter period.

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Autorzy i Afiliacje

D. Heim

Abstrakt

The main idea of this work is to demonstrate an application of the generalized perturbation-based Stochastic Finite Element Method for a determination of the reliability indicators concerning elastic stability for a certain spectrum of the civil engineering structures. The reliability indicator is provided after the Eurocode according to the First Order Reliability Method, and computed using the higher order Taylor expansions with random coefficients. Computational implementation provided by the hybrid usage of the FEM system ROBOT and the computer algebra system MAPLE enables for reliability analysis of the critical forces in the most popular civil engineering structures like simple Euler beam, 2 and 3D single and multi-span steel frames, as well as polyethylene underground cylindrical shell. A contrast of the perturbation-based numerical approach with the Monte-Carlo simulation technique for the entire variability of the input random dispersion included into the Euler problem demonstrates the probabilistic efficiency of the perturbation method proposed.

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Autorzy i Afiliacje

M. Kamiński
P. Świta

Abstrakt

To reliably calibrate suitable partial safety factors, useful for the specification of global condition describing structural safety level in considered design case, usually the evaluation of adequate failure probability is necessary. In accidental fire situation, not only probability of the collapse of load-bearing structure, but also another probability related to the people staying in a building at the moment of fire occurence should be assessed. Those values are different one from another in qualitative sense but they are coupled because they are determined by similar factors. The first one is the conditional probability with the condition that fire has already occured, whereas the second is the probability of failure in case of a potential fire, which can take place in the examined building compartment, but its ignition has not yet appeared. An engineering approach to estimate such both probabilities is presented and widely discussed in the article.

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Autorzy i Afiliacje

M. Maślak

Abstrakt

A two-scale numerical homogenization approach was used for granular materials. At small-scale level, granular micro-structure was simulated using the discrete element method. At macroscopic level, the finite element method was applied. An up-scaling technique took into account a discrete model at each Gauss integration point of the FEM mesh to derive numerically an overall constitutive response of the material. In this process, a tangent operator was generated with the stress increment corresponding to the given strain increment at the Gauss point. In order to detect a loss of the solution uniqueness, a determinant of the acoustic tensor associated with the tangent operator was calculated. Some elementary geotechnical tests were numerically calculated using a combined DEM-FEM technique.

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Autorzy i Afiliacje

M. Nitka
J. Tejchman

Abstrakt

The paper focuses on different approaches to the safety assessment of concrete structures designed using nonlinear analysis. The method based on the concept of partial factors recommended by Eurocodes, and methods proposed by M. Holicky, and by the author of this paper are presented, discussed and illustrated on a numerical example. Global safety analysis by M. Holicky needs estimation of the resistance coefficient of variation from the mean and characteristic values of resistance, and requires two separate nonlinear analyses. The reliability index value and the sensitivity factor for resistance should be also identified. In the method proposed in this paper, the resistance coefficient of variation necessary to calculate the characteristic value of resistance may be adopted from test results and the resultant partial factor for materials properties, and may be calculated according to Eurocodes. Thus, only one nonlinear analysis from mean values of reinforcing steel and concrete is required.

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Autorzy i Afiliacje

Sz. Woliński

Zasady etyki publikacyjnej

ETHICS POLICY

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Procedura recenzowania

Manuscript Peer-Review Procedure

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-The model of peer-review is double-blind: the reviewers do not know the names of the authors, and the authors do not know who reviewed their manuscript (but if the research is published reviewers can eventually know the names of the authors). A complete list of reviewers is published in a traditional version of the journal: in-print.
-It is the editor who appoints two reviewers; however, if there are discrepancies in the assessment the third reviewer can be appointed.
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Editor’s responsibilities
-The editor decides whether the paper fulfills all requirements i.e. formal and scientific and which articles submitted to the journal should be published.
-In making these decisions, the editor may be guided by the policies of the journal’s editorial board as well as by legal requirements regarding libel, copyright infringement, and plagiarism.
-The editor maintains the integrity of the academic record, precludes business needs from compromising intellectual and ethical standards, and is always willing to publish corrections, clarifications, retractions, and apologies when needed.
-The editor evaluates manuscripts for intellectual content without regard to race, gender, sexual orientation, religious belief, ethnic origin, citizenship, or political philosophy of the author(s).
-The editor does not disclose any information about a manuscript under consideration to anyone other than the author(s), reviewers and potential reviewers, and in some instances the editorial board members, as appropriate.

Reviewers' responsibilities
Any manuscripts received for review are treated as confidential documents. They must not be shown to or discussed with others except if authorized by the editor. Privileged information or ideas obtained through peer review is kept confidential and not used for personal advantage Any invited reviewer who feels unqualified to review the manuscript or knows that its timely review will be impossible should immediately notify the editor so that alternative reviewers can be contacted. Reviewers should identify relevant published work that has not been cited by the authors. Any statement that an observation, derivation, or argument had been previously reported should be accompanied by the relevant citation. A reviewer should also call to the editor's attention any substantial similarity or overlap between the manuscript under consideration and any other published data of which they have personal knowledge. Reviewers should not consider evaluating manuscripts in which they have conflicts of interest resulting from competitive, collaborative, or other relationships or connections with any of the authors, companies, or institutions connected to the submission. Reviews should be conducted objectively. Personal criticism of the author is unacceptable. Referees should express their views clearly with appropriate supporting arguments. All reviews must be carried out on a special form available in the Editorial System.

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