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Öğe Analysis of technical specification-based disputes in construction industry(2013) Erdis, Ercan; Ozdemir, Sitki AlperThis article covers the role of the standard and dynamic technical specification system for building structures in avoiding disputes between the employer and contractor, which is a ever-lasting problem in Turkey. For this purpose, the study was started with examining approximately 100 specification files and 32 court records on these issues. Afterwards, a survey was conducted among 58 construction firms associated with the "Turkish Contractors Union" to identify the causes of technical specification related disputes and developing suggestions for possible resolutions. The survey results showed that these disputes generally arise from project characteristics and are mostly human oriented. It was concluded that establishing an institute consisting of experts in technical specifications, creating a standard and dynamic specification system, having quality guidelines, making judicial arrangements to shorten the judicial process, and information dissemination on related subjects through academic programs and judicial documents are important. © 2013 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.Öğe Crisis management in Turkish construction industry(Pergamon-Elsevier Science Ltd, 2006) Ocal, Emin; Oral, Emel Laptali; Erdis, ErcanVarious economical crises have affected Turkish economy during the last decade and construction industry has always been among the hardest hit; giving the idea that a comprehensive approach to crisis management is unavoidable. However, literature showed no findings related with crisis management applications by construction companies. Thus, a questionnaire survey was undertaken by the top management of 120 construction companies to investigate the degree of crisis management applications throughout the industry, mainly focusing on the outcomes during the economical crisis in 2001. Frequency analysis, Likert scale of comparison, Thurstone's paired comparisons, Pearson's chi-square test and Fisher's exact test were used to evaluate the results. The results showed that government policies and instable market conditions were the most important causes of crisis for Turkish construction companies. Meanwhile, only a small number of the companies utilized a systematic crisis management and the extent of crisis management applications varied depending on the size and the structure of the companies. Consequently, panic and powerlessness were the common feelings shared throughout the industry during the economical crisis in 2001. Despite, it was still encouraging that the managers utilized contemporary decision-making methods to get out of the crisis and their final decisions were generally in favour of strategically repositioning themselves. (c) 2005 Elsevier Ltd. All rights reserved.Öğe Decision tree analysis of construction fall accidents involving roofers(Pergamon-Elsevier Science Ltd, 2015) Mistikoglu, Gulgun; Gerek, Ibrahim Halil; Erdis, Ercan; Usmen, P. E. Mumtaz; Cakan, Hulya; Kazan, Emrah EsrefData mining (DM) techniques have not been adopted on a wide scale for construction accident data analysis. The decision tree (DT) technique is a supervised data mining method that shows good promise for this purpose. The C5.0 and CHAID algorithms were employed in this study to construct decision trees and to extract rules that show the associations between the input and output variables (attributes) for roofer fall accidents. Data obtained from the US Occupational Safety and Health Administration (OSHA) was incorporated in this research. Degree of injury (fatality vs. nonfatal injury) was selected as the output attribute, and a multitude of input attributes were included in the study. Two models based on the algorithms were developed and validated. The results showed that decision trees provided specific and detailed depictions of the associations between the attributes. It was found that fatality chances increased with increasing fall distance and decreased when safety training was provided. The most important input attributes in the models were identified as the fall distance, fatality/injury cause, safety training, and construction operation prompting fall, meaning that these factors had the best predictive power related to whether a roofer fall accident would result in a fatality or nonfatal injury. (C) 2014 Elsevier Ltd. All rights reserved.Öğe THE EFFECT OF CURRENT PUBLIC PROCUREMENT LAW ON DURATION AND COST OF CONSTRUCTION PROJECTS IN TURKEY(Vilnius Gediminas Tech Univ, 2013) Erdis, ErcanThe current public procurement law (Law No. 4734) was established in Turkey in 2003. The current law has fundamental differences from the previous one, Law No. 2886, in that the current law's main objective is to increase the effective use of public resources. Although the current law was enacted nine years ago, no in-depth research has been undertaken related to the extent of public savings. Thus, the aim of this research is to analyze the performance of public investments for construction with respect to their success in achieving on time and within budget completion. Additionally, a comparison between the completion duration and budget of construction projects undertaken under the current and the previous law is presented. To achieve these goals, historical contract documents addressing 878 and 575 public construction projects undertaken under two laws, respectively, were analyzed. In this context, the data mining method, including decision trees, artificial neural network, and support vector machines, was applied to predict the duration and cost deviations of the construction projects during the tender process, and the results were compared. It was demonstrated that the current law has contributed substantially towards the completion of the projects within estimated or envisaged durations and costs. The findings of this research can be generalized to countries with similar economical and organizational structures with Turkey.Öğe EVALUATION OF PLASTERING CREW PERFORMANCE IN BUILDING PROJECTS USING DATA ENVELOPMENT ANALYSIS(Vilnius Gediminas Tech Univ, 2016) Gerek, Ibrahim Halil; Erdis, Ercan; Mistikoglu, Gulgun; Usmen, Mumtaz A.The research question addressed in this study was how the performance of construction crews working in a certain project or locality could be evaluated, ranked and improved. To develop and demonstrate the relevant framework, data envelopment analysis (DEA) was applied to establish the relative efficiency of plastering crews working in building projects located in different cities around Turkey. Data were collected from 40 crews of varying characteristics, and their technical efficiency scores were computed using the Banker, Charnes and Cooper (BCC) model, which is based on variable returns-to-scale (VRS). The model yields efficiency scores that range between 0 and 1, and a company or crew is considered efficient if its score is 1.0 (100%). Efficient and inefficient crews were identified and ranked on this basis in the study. Cross tabulation analyses were subsequently conducted to gain further insights into the relationships between the efficiency scores and input factors of numbers of skilled and unskilled laborers, daily labor unit costs, work hours, average age of crew members, total crew experience, plastering location, plastering technique, and plaster type. No discernible relationship could be identified between the efficiency scores and productivity outputs of the crews. It was found that plastering technique, plastering location, and total crew experience had a significant association with crew efficiency. Efficiency improvement strategies identified included training, hiring experienced plasterers, adopting more advanced plastering technology, implementing better jobsite management practices, and enhancing workers' knowledge, skills and attitude towards productivity and quality.Öğe Industry financial ratios -: application of factor analysis in Turkish construction industry(Pergamon-Elsevier Science Ltd, 2007) Ocal, M. Emin; Oral, Emel Laptali; Erdis, Ercan; Vural, GamzeTurkish economy has been hit by various economical crises between the years 1998 and 2001 and the economic stagnation still continues. Past experiences in various countries show that it is vitally important to encourage construction activities in order to get out of stagnation, as construction output directly affects about 200 other sectors and industry financial ratio analysis is a means to provide a basis for the governments to undertake corrective action. However, there are over 50 financial ratios that can be used during analysis and some are more important than the others for different industries. Previous research has shown that there are about 25 factors that are important for the construction companies. This, in turn, requires elimination of unrelated data. Factor analysis is a data reduction and classification technique, which can be applied in financial analysis. Factor analysis was thus applied to the financial data collected from Turkish construction companies for a 5-year period in order to determine the financial indicators that can be used to analyse the financial trend of the industry. Five independent factors, i.e. liquidity, capital structure and profitability, activity efficiency, profit margin and growth, and assets structure were identified to be sensitive to the economical changes in the country. The results of the factor-based analysis can be used both by the government to analyse the changes in the industry with respect to time and by the construction companies to analyse their financial state with respect to their rivals. (c) 2005 Elsevier Ltd. All rights reserved.Öğe Modelling masonry crew productivity using two artificial neural network techniques(Vilnius Gediminas Tech Univ, 2015) Gerek, Ibrahim Halil; Erdis, Ercan; Mistikoglu, Gulgun; Usmen, MumtazArtificial neural networks have been effectively used in various civil engineering fields, including construction management and labour productivity. In this study, the performance of the feed forward neural network (FFNN) was compared with radial basis neural network (RBNN) in modelling the productivity of masonry crews. A variety of input factors were incorporated and analysed. Mean absolute percentage error (MAPE) and correlation coefficient (R) were used to evaluate model performance. Research results indicated that the neural computing techniques could be successfully employed in modelling crew productivity. It was also found that successful models could be developed with different combinations of input factors, and several of the models which excluded one or more input factors turned out to be better than the baseline models. Based on the MAPE values obtained for the models, the RBNN technique was found to be better than the FFNN technique, although both slightly overestimated the masons' productivity.Öğe Perceptions of Turkish construction firms about the marketing concepts(Vilnius Gediminas Tech Univ, 2015) Erdis, Ercan; Coskun, Hilmi; Demirci, MustafaCompetitive marketing environment requires construction companies to come up with the right strategies to progress. This only becomes possible by preparing rigorous preconstruction feasibility studies. Additionally, the effectiveness of promotion activities of the company is important to acquire a market share which can be realized by having systematic marketing concept. In this study, the perception and application level of marketing concept of construction firms are investigated. The promotion strategies which enable the companies to have systematic applications of marketing concepts in order to compete with other companies in the sector are discussed. To evaluate the marketing attitudes as applied by the companies, a questionnaire was performed with forty nine Turkish construction firms. The perception and application of the marketing are discussed based on the organizational structure and key interest areas of construction companies. The overall result deduced is that the construction companies do not have a systematic approach to marketing. The companies have primarily adopted the approaches to keep their current places in the sector.Öğe PRICING POLICIES AS A MARKETING STRATEGY IN THE CONSTRUCTION INDUSTRY: CASE STUDY OF TURKISH COMPANIES(Vilnius Gediminas Tech Univ, 2013) Coskun, Hilmi; Erdis, Ercan; Demirci, MustafaThe firms in the construction industry have to determine pricing and promotion policies, then these policies must be carefully and systematically integrated with the marketing strategies. Not only the demand and cost are important in pricing decisions but competition is also a significant variable to be considered. To determine the difficulties and the affecting factors in applying pricing decisions within the marketing concepts in construction sector, a survey was carried out among the Turkish companies as a sample group. In total 49 companies, mostly medium-size firms have been surveyed. The responses of firms are considered based on their actively engaged subsectors, namely, residential, commercial/public buildings, and infrastructure construction. The answers of firms are also evaluated based on their stated organizational structure, namely, simple, hierarchical, project, and network. The views about the various aspects of pricing policy development in phases, for example before and during bid, differ in the construction companies depending on their actively involved fields and their organizational structures.
