scholarly journals Forecasting the Project Duration Average and Standard Deviation from Deterministic Schedule Information

2020 ◽  
Vol 10 (2) ◽  
pp. 654 ◽  
Author(s):  
Pablo Ballesteros-Pérez ◽  
Alberto Cerezo-Narváez ◽  
Manuel Otero-Mateo ◽  
Andrés Pastor-Fernández ◽  
Jingxiao Zhang ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Network Analysis ◽  
Construction Projects ◽  
Project Evaluation ◽  
Alternative Methods ◽  
Stochastic Network ◽  
Project Duration ◽  
Deterministic Scheduling ◽  
Mathematical Expressions ◽  
Additional Calculation

Most construction managers use deterministic scheduling techniques to plan construction projects and estimate their duration. However, deterministic techniques are known to underestimate the project duration. Alternative methods, such as Stochastic Network Analysis, have rarely been adopted in practical contexts as they are commonly computer-intensive, require extensive historical information, have limited contextual/local validity and/or require skills most practitioners have not been trained for. In this paper, we propose some mathematical expressions to approximate the average and the standard deviation of a project duration from basic deterministic schedule information. The expressions’ performance is successfully tested in a 4100-network dataset with varied activity durations and activity durations variability. Calculations are quite straightforward and can be implemented manually. Furthermore, unlike the Project Evaluation and Review Technique (PERT), they allow drawing inferences about the probability of project duration in the presence of several critical and subcritical paths with minimal additional calculation.

scholarly journals ANALISIS PENJADWALAN PROYEK GEDUNG BERTINGKAT DENGAN METODE PERT DAN M-PERT MENGGUNAKAN SIMULASI MONTE CARLO

2020 ◽  
Vol 3 (3) ◽  
pp. 533
Author(s):  
Josua Guntur Putra ◽  
Jane Sekarsari
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Standard Deviation ◽  
Research Method ◽  
Probabilistic Approach ◽  
Deterministic Scheduling ◽  
Work Duration ◽  
The Mean ◽  
Building Project ◽  
Story Building

One of the keys to success in construction execution is timeliness. In fact, construction is often late than originally planned. It’s caused by project scheduling uncertainty. Deterministic scheduling methods use data from previous projects to determine work duration. However, not every project has same work duration. The PERT method provides a probabilistic approach that can overcome these uncertainties, but it doesn’t account for the increase in duration due to parallel activities. In 2017, the PERT method was developed into the M-PERT method. The purpose of this study is to compare the mean duration and standard deviation of the overall project between PERT and M-PERT methods and compare them in Monte Carlo simulation. The research method used is to calculate the mean duration of the project with the PERT, M-PERT, and Monte Carlo simulation. The study was applied to a three-story building project. From the results of the study, the standard deviation obtained was 5.079 for the M-PERT method, 8.915 for the PERT method, and 5.25 for the Monte Carlo simulation. These results show the M-PERT method can provide closer results to computer simulation result than the PERT method. Small standard deviation value indicates the M-PERT method gives more accurate results.ABSTRAKSalah satu kunci keberhasilan dalam suatu pelaksanaan konstruksi adalah ketepatan waktu. Kenyataannya, pelaksanaan konstruksi sering mengalami keterlambatan waktu dari yang direncanakan. Hal ini disebabkan oleh ketidakpastian dalam merencanakan penjadwalan proyek. Metode penjadwalan yang bersifat deterministik menggunakan data dari proyek sebelumnya untuk menentukan durasi pekerjaan. Akan tetapi, tidak setiap proyek memiliki durasi pekerjaan yang sama. Metode PERT memberikan pendekatan probabilistik yang dapat mengatasi ketidakpastian tersebut, tetapi metode ini tidak memperhitungkan pertambahan durasi akibat adanya kegiatan yang berbentuk paralel. Pada tahun 2017, metode PERT dikembangkan menjadi metode M-PERT. Tujuan dari penelitian ini adalah membandingkan mean durasi dan standar deviasi proyek secara keseluruhan antara metode PERT dan M-PERT dan membandingkan kedua metode tersebut dalam simulasi Monte Carlo. Metode penelitian yang dilakukan adalah menghitung mean durasi proyek dengan metode PERT, M-PERT, dan simulasi Monte Carlo. Penelitian diterapkan pada proyek gedung bertingkat tiga. Dari hasil penelitian, nilai standar deviasi diperoleh sebesar 5,079 untuk metode M-PERT, 8,915 untuk metode PERT, dan 5,25 untuk simulasi Monte Carlo. Hasil ini menunjukan metode M-PERT dapat memberikan hasil yang lebih mendekati hasil simulasi komputer daripada metode PERT. Nilai standar deviasi yang kecil menunjukan metode M-PERT memberikan hasil yang lebih akurat.

scholarly journals On the Algorithms Used to Compute the Standard Deviation of Wind Direction

2009 ◽  
Vol 48 (10) ◽  
pp. 2144-2151 ◽  
Author(s):  
Pierre S. Farrugia ◽  
James L. Borg ◽  
Alfred Micallef
Keyword(s):  
Standard Deviation ◽  
Wind Direction ◽  
Atmospheric Stability ◽  
Angular Distance ◽  
Circular Statistics ◽  
Horizontal Wind ◽  
Stability Class ◽  
Mathematical Expressions ◽  
Analytical Work

Abstract The standard deviation of wind direction is a very important quantity in meteorology because in addition to being used to determine the dry deposition rate and the atmospheric stability class, it is also employed in the determination of the rate of horizontal diffusion, which in turn determines transport and dispersion of air pollutants. However, the computation of this quantity is rendered difficult by the fact that the horizontal wind direction is a circular variable having a discontinuity at 2π radians, beyond which the wind direction starts again from zero, thus preventing angular subtraction from being a straightforward procedure. In view of such a limitation, this work is meant to provide new mathematical expressions that simplify both the computational and analytical work involved in handling the standard deviation of wind direction. This is achieved by deriving a number of Fourier series and Taylor expansions that can represent the minimum angular distance and its powers. Using these expressions, the relation between two algorithms commonly used to determine the standard deviation of wind direction is analyzed. Furthermore, given that these trigonometric expansions effectively reduce the mathematical complexity involved when dealing with circular statistics, their potential application to solve other problems is discussed.

scholarly journals On the Origin of the Standardization Sensitivity in RegEM Climate Field Reconstructions*

2008 ◽  
Vol 21 (24) ◽  
pp. 6710-6723 ◽  
Author(s):  
Jason E. Smerdon ◽  
Alexey Kaplan ◽  
Diana Chang
Keyword(s):  
Standard Deviation ◽  
Missing Values ◽  
Mean Field ◽  
Alternative Methods ◽  
Reconstruction Method ◽  
Climate Data ◽  
The Mean ◽  
Calibration Interval ◽  
Reconstruction Interval ◽  
Selection Of

Abstract The regularized expectation maximization (RegEM) method has been used in recent studies to derive climate field reconstructions of Northern Hemisphere temperatures during the last millennium. Original pseudoproxy experiments that tested RegEM [with ridge regression regularization (RegEM-Ridge)] standardized the input data in a way that improved the performance of the reconstruction method, but included data from the reconstruction interval for estimates of the mean and standard deviation of the climate field—information that is not available in real-world reconstruction problems. When standardizations are confined to the calibration interval only, pseudoproxy reconstructions performed with RegEM-Ridge suffer from warm biases and variance losses. Only cursory explanations of this so-called standardization sensitivity of RegEM-Ridge have been published, but they have suggested that the selection of the regularization (ridge) parameter by means of minimizing the generalized cross validation (GCV) function is the source of the effect. The origin of the standardization sensitivity is more thoroughly investigated herein and is shown not to be associated with the selection of the ridge parameter; sets of derived reconstructions reveal that GCV-selected ridge parameters are minimally different for reconstructions standardized either over both the reconstruction and calibration interval or over the calibration interval only. While GCV may select ridge parameters that are different from those that precisely minimize the error in pseudoproxy reconstructions, RegEM reconstructions performed with truly optimized ridge parameters are not significantly different from those that use GCV-selected ridge parameters. The true source of the standardization sensitivity is attributable to the inclusion or exclusion of additional information provided by the reconstruction interval, namely, the mean and standard deviation fields computed for the complete modeled dataset. These fields are significantly different from those for the calibration period alone because of the violation of a standard EM assumption that missing values are missing at random in typical paleoreconstruction problems; climate data are predominantly missing in the preinstrumental period when the mean climate was significantly colder than the mean of the instrumental period. The origin of the standardization sensitivity therefore is not associated specifically with RegEM-Ridge, and more recent attempts to regularize the EM algorithm using truncated total least squares could theoretically also be susceptible to the problems affecting RegEM-Ridge. Nevertheless, the principal failure of RegEM-Ridge arises because of a poor initial estimate of the mean field, and therefore leaves open the possibility that alternative methods may perform better.

scholarly journals Social network analysis of construction companies operating in international markets: case of Turkish contractors

2016 ◽  
Vol 23 (3) ◽  
pp. 327-337 ◽  
Author(s):  
Bartug Kemal AKGUL ◽  
Beliz OZORHON ◽  
Irem DIKMEN ◽  
M. Talat BIRGONUL
Keyword(s):  
Social Network ◽  
Social Network Analysis ◽  
Network Analysis ◽  
Construction Projects ◽  
International Markets ◽  
Project Networks ◽  
Construction Companies ◽  
International Construction ◽  
Multiple Partners ◽  
Complex Projects

Investigation of market entry strategies is critical for the success of international contractors. Establishing partnerships is among the most effective vehicles of operating in international markets. The major objective of this paper is to analyze the partnership behavior of contractors in overseas projects. In this respect, social network analysis (SNA) was used to better understand the collaborative project networks in different markets and for projects of differing sizes. A database was developed based on the collaborative international construction projects where Turkish firms and their non-Turkish partners were involved. A total of 449 projects carried out in 46 countries were used for the analysis. The findings of the study suggest that contractors adopt different strategies depending on the market and project character­istics. The majority of the companies tend to remain in the same markets; they keep working with the same partners or choose local partners; and engage with multiple partners in more complex projects. This study is expected to help contractors reflect on their internationalization decisions and devise appropriate strategies to establish project networks.

scholarly journals A Novel Method of Developing Construction Projects Schedule under Rework Scenarios

2019 ◽  
Vol 11 (20) ◽  
pp. 5710
Author(s):  
Guofeng Ma ◽  
Shan Jiang ◽  
Tiancheng Zhu ◽  
Jianyao Jia
Keyword(s):  
Construction Projects ◽  
Development Project ◽  
Real Estate Development ◽  
Design Structure Matrix ◽  
Project Duration ◽  
Project Completion ◽  
Design Structure ◽  
Novel Method ◽  
The Impact ◽  
Critical Chain

Construction projects have faced serious schedule delays caused by rework risks. However, it appears that traditional methods are of limited value in developing applicable project schedules. This study presents an analysis on construction projects schedule development under rework scenarios by a novel method named the improved critical chain design structure matrix (CCDSM). Research data are collected from a real estate development project in China. As a result, predictions of project completion duration and probability have been made. A reliable schedule considering information interactions has been developed and visualized. Rework impact areas of activities have been examined to quantitatively record the impact on project duration. To meet different demands, the method generates two more schedules setting different rework buffers. Furthermore, these activities have the potential of causing rework and have been quantified based on the calculation of two criticalities, providing an identification of rework-intensive works that should be payed close importance to, which have not be realized by previous methods. The results proved the feasibility and effectiveness of this method in developing a schedule for construction projects disturbed by rework, helping practitioners adopt measures to avoid rework-caused schedule delays and achieve sustainable development of such projects.

Modeling of the harmonization method for executing a multi-unit construction project

2019 ◽  
Vol 9 (1) ◽  
pp. 282-291 ◽  
Author(s):  
Michał Tomczak
Keyword(s):  
Construction Industry ◽  
Construction Projects ◽  
Construction Project ◽  
Optimization Method ◽  
Linear Processes ◽  
Project Duration ◽  
Construction Enterprises ◽  
Non Linear ◽  
Implementation Time ◽  
Selection Of

AbstractOne of the key problems in managing the realization of a construction project is the selection of appropriate working crews and coordinating their activities in a way that ensures the highest degree of implementation of defined goals (minimizing the project duration and/or reducing downtime and related costs). Most of the existing methods of work harmonization used in construction industry allow obtaining the desired results only in relation to the organization of the processes realization in repetitive linear projects. In case of realization of non-linear construction objects or construction units, it is usually necessary to choose between the reduction of the project implementation time and maintaining the continuity of crews work on the units. It was found that there is a lack in the literature of developed method enabling harmonization of crews’ work, while minimizing the downtime at work and the duration of the entire project taking into account additional constraints, e.g. the need to not exceed the deadlines for the realization of the project stages.The article presents the concept of a multi-criteria optimization method of harmonizing the execution of non-linear processes of a multi-unit construction project in deterministic conditions. It will enable the reduction of realization time and downtimes in work, taking into account the preferences of the decision maker regarding the relevance of the optimization criteria. A mathematical model for optimizing the selection of crews and order of completion of units in multi-unit construction projects was also developed. In order to present the possibility of usage of the developed concept, an example of the optimal selection of crews and their work schedule was solved and presented. The proposed method may allow for better use of the existing production potential of construction enterprises and ensure synchronization of the crews employed during the work, especially in the case of difficulties in acquiring qualified staff in construction industry.

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