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1

Forecasting the course of construction project management in conditions of uncertainty

Konior Jarosław

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

557--572

EN

The methodology and research results presented in the article indicate the practical possibility of conducting optimization of construction project management course. The goal of the achievement leads to the rationalization of the management of investment tasks, in which there are a series of uncertain parameterized events. The goal was achieved through many years of the author’s own research, which was personally carried out on several hundred construction projects according to original methodology for assessing and forecasting the characteristic parameters of construction investments (cost and time) in conditions of uncertainty: from determinism, through probability and randomness, to fuzziness. The presented and documented achievement stands for accomplishment in project management of construction projects, where decision-making with an increasing degree of uncertainty takes place and requires the course of investment tasks that will be implemented in the future to be forecasted. In the conducted research and conclusions it was proven that construction processes should be considered as phenomena with random events and various degrees of uncertainty, to which methodology with developed modelling parameters should be used.

PL

Metodyka i wyniki badań zaprezentowane w artykule wskazują na praktyczną możliwość optymalizacji kosztowej przebiegu przedsięwzięć budowlanych. Cel osiągnięcia prowadzi do racjonalizacji zarządzania zadań inwestycyjnych, w których występują sparametryzowane przeze mnie serie zdarzeń niepewnych. Cel został osiągnięty na drodze kilkunastoletnich badań własnych, które są prowadzone na kilkuset obiektach i budowach według autorskiej metodyki oceny i prognozy ich charakterystycznych parametrów (koszt i czas) w warunkach niepewności: od determinizmu, poprzez probabilistykę i przypadkowość, aż do rozmytości. Zarządzanie przedsięwzięciami budowlanymi i podejmowanie decyzji zarządczych następuje w rosnącym stopniu niepewności i wymaga prognozowania przebiegu zadań inwestycyjnych, które zostaną zrealizowane w przyszłości. W prezentowanych badaniach udowodniono, że procesy budowalne powinny być rozważane jako zjawiska ze zdarzeniami losowymi o różnym stopniu niepewności, do których stosować metodykę o zbliżonych parametrach modelowania.

2

Prediction model of seasonality in the construction industry based on the accidentality phenomenon

Hoła Bożena, Topolski Mariusz, Szer Iwona, Szer Jacek, Blazik-Borowa Ewa

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e30, 2022

EN

The construction industry is an economic sector that is characterized by seasonality. Seasonal factors affect the volume of production, which in turn affects the accident rate. The aim of the research presented in the article was to develop a model for predicting the number of people injured in occupational accidents in the construction industry. Based on the analysis of statistical data and previous studies, the occurrence of certain regularities of the accidentality phenomenon was found, namely the long-term trend over many years, as well as seasonality and cyclicality over the course of a year. The found regularities were the basis for the assumptions that were made for the construction of the model. A mathematical model was built in the non-linear regression dimension. The model was validated by comparing the results of prediction errors generated by the developed model with the results of prediction errors generated by other known models, such as ARIMA, SARIMA, linear and polynomial models, which take into account the seasonality of the phenomenon. The constructed model enables the number of people injured in accidents in the construction industry in selected months of future years to be predicted with high accuracy. The obtained results can be the basis for making appropriate decisions regarding preventive and prophylactic measures in the construction industry. Commonly known mathematical tools available in the STATISTICA package were used to solve the given task.

3

Influence of randomness of buckling coefficient on the reliability index's value under fire conditions

Kubicka Katarzyna, Radoń Urszula

Archives of Civil Engineering

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2018

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Vol. 64, nr 3

173--179

EN

The paper concerns reliability analysis of steel trusses under fire conditions with taking into account randomness of buckling coefficient, modulus of elasticity's and yield strength's reduction factors. To assess the reliability system analysis was employed. The calculations of appropriate standard deviations of random variables were realized in Mathematica program. Two types of trusses were analysed: statically determinate and indeterminate, so respectively serial and mixed system were used. The results, gotten for different levels of coefficients of variation of reduction factors were presented.

4

The effect of randomness on the stability of capillary gravity waves in the presence of air flowing over water

Majumder D. P., Dhar A. K.

International Journal of Applied Mechanics and Engineering

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2015

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Vol. 20, no. 4

835--855

EN

A nonlinear spectral transport equation for the narrow band Gaussian random surface wave trains is derived from a fourth order nonlinear evolution equation, which is a good starting point for the study of nonlinear water waves. The effect of randomness on the stability of deep water capillary gravity waves in the presence of air flowing over water is investigated. The stability is then considered for an initial homogenous wave spectrum having a simple normal form to small oblique long wave length perturbations for a range of spectral widths. An expression for the growth rate of instability is obtained; in which a higher order contribution comes from the fourth order term in the evolution equation, which is responsible for wave induced mean flow. This higher order contribution produces a decrease in the growth rate. The growth rate of instability is found to decrease with the increase of spectral width and the instability disappears if the spectral width increases beyond a certain critical value, which is not influenced by the fourth order term in the evolution equation.

5

Random and fuzzy measure of unpredictable construction works

Konior J.

Archives of Civil Engineering

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2015

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Vol. 61, nr 3

75--88

EN

Supplementing well recognised practical models of project and construction management, based on probabilistic and fuzzy events may make possible to transfer the weight of the change and extra orders assessment from the qualitative form to a quantitative one. This assessment, however, is naturally burdened with an immeasurable, subjective aspect. Elaboration of probability of occurrence in a construction project unforeseen building works requires application (in addition to the non-measureable, qualitative criteria) of measurable (quantitative) criteria which still appear during construction project implementation. In reimbursable engineering contracts, a random event described as an extra, supplementary building work has a random character and occurs with a specific likelihood. In lump sum contracts, on the other hand, such a random event has a fuzzy character and its occurrence is defined in a linear manner by the function of affiliation to the set of fuzzy events being identical with unforeseen events. The strive for quantitative presentation of criteria regarded by nature as qualitative and the intention to determine relations between them led to the application of the fuzzy sets theory to this issue. Their properties enable description of the unforeseen works of construction projects in an unambiguous, quantitative way.

PL

Szacując prawdopodobieństwo wystąpienia w przedsięwzięciu budowlanym zamiennych lub dodatkowych robót budowlanych stosuje się - oprócz kryteriów niemierzalnych (jakościowych) - kryteria mierzalne (ilościowe) wyrażone w analizie przepływu środków finansowych w czasie realizacji przedsięwzięcia budowlanego. W kontraktach inżynierskich powykonawczych zdarzenie losowe określone jako nieprzewidziana robota budowlana ma charakter losowy i występuje z określonym prawdopodobieństwem: w kontraktach ryczałtowych natomiast takie zdarzenie losowe ma charakter rozmyty i jego występowanie jest określone liniowo funkcją przynależności do zbioru zdarzeń rozmytych tożsamych z nieprzewidzianymi. Dążenie do ilościowego ujęcia kryteriów z natury uchodzących za jakościowe i chęć wyznaczenia panujących między nimi relacji, doprowadziło do spojrzenia na zagadnienie w kategoriach zbiorów rozmytych jako pochodną ujęcia probabilistycznego. Ich właściwości dają możliwość opisania nieprzewidzianych - zamiennych i dodatkowych - robót budowlanych w jednoznacznym aspekcie ilościowym.

6

Nieprzewidziane roboty budowlane jako zdarzenia i relacje rozmyte

Konior J.

Przegląd Budowlany

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2006

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R. 77, nr 2

36-39

7

Optimal control for a nonstationary linear system with a quadratic cost functional

Czornik Adam

Matematyka Stosowana : matematyka dla społeczeństwa

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1997

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Nr 40

3--11

EN

This paper is about optimal control of infinite-horizon nonstationary stochastic linear processes with a quadratic cost criterion. The synthesis problem of optimal control is solved under the assumptions that the criterion is an average expected cost and that the process' matrices possess limits for the time approaching infinity. Furthermore, the limit matrices are such that the "limit" process is both observable and controllable. The paper documents existence of an optimal feedback control policy. The policy is such that the gain matrix is a (scaled) solution to a Riccati stationary matrix equation. The equation is stationary in that its coefficients are the limits of the process' non-stationary matrices.