Serdar Ulubeyli

A multiple criteria decision‐making approach to the selection of concrete pumps

Abstract In this study, the ELECTRE III method, which is one of the most common techniques among multiple criteria decision‐making (MCDM) approaches, was considered in a selection problem of concrete pumps. As a methodological framework, a two‐step questionnaire survey was conducted by 70 firms that have and use concrete pumps. A solution of the problem was then found in the light of the real world data by means of ELECTRE III. The paper can be of value to researchers studying the anatomy of decision‐making in equipment selection in general and investigating selection criteria of concrete pumps in particular. It also contributes to the academic environment as an application practice of ELECTRE III to correspond with the nature of equipment selection and as an effective means for the formalization of knowledge possessed by industrial practitioners. On the practical side, ELECTRE III offers an efficient and convenient tool that forces the users into orderly and methodical thinking, and guides them in making...

Causes of Delays in Construction Projects in Turkey

Abstract In both developing and industrialized countries, deviation from a planned time schedule is one of the most frequently encountered problems in construction investments. Various factors faced with during construction period prevent systematic flow of work, which causes time-based anomalies as a conclusion. Considering the vital importance of the construction industry on the macro-economic structure of a country, it is inevitable to be aware of considerable effect of the timely completion on the allocated project budget. In this study, causes of time extensions in the Turkish construction industry and levels of their importance were examined together. In total, 34 factors affecting project duration were taken into account. A questionnaire survey, including these factors, was then applied to 71 construction companies in Turkey, and the outcomes were evaluated by means of statistical analyses. According to the results, “design and material changes” was found to be the most predominant factor, followed...

Health and Safety Perception of Workers in Turkey: A Survey of Construction Sites

This study reports the general health and safety (HS) conditions in the Turkish construction industry from the perspective of construction labor. Toward this aim, a questionnaire survey was carried out with 800 workers employed in 32 construction projects in Turkey. Contractors were found to neglect their legal liabilities in paying workers’ insurance premiums. Also, they overlooked safety training and were reluctant to hiring physicians at construction sites and investing in personal protective equipment (PPE). As the real constructors of projects, workers did not attach adequate importance to occupational training. In addition, they were not willing to use some PPE. Key participants of HS affairs such as workers, contractors, unions, and government should comprehend their drawbacks to overcome the current dangerous view of the industry. In this regard, related government bodies should compel contractors and workers to adapt to the relatively new regulations on occupational HS.

Fuzzy multi-criteria decision making model for subcontractor selection in international construction projects

Abstract.A general contractors ability to select proper subcontractors in foreign projects is a key competitive advantage. Toward this aim, a subcontractor selection model (CoSMo) was developed in this study. As a computational approach, the fuzzy sets method was employed because it can model human judgment by means of linguistic values, combining qualitative and quantitative decision criteria into an aggregate measure. Although the algorithm may be complex for easy acceptance by industrial practitioners, this disadvantage was minimized through a computer-supported system. In order to gain a better understanding of the current practice of CoSMo, a real world construction project was conducted. As a result, it was observed that CoSMo has high practical application and can be used as an advisory system by satisfying principal contractors requirements to reduce the risk involved in the selection of a subcontractor. Moreover, it gives an initial idea of how subcontractors perform on each decision criterion ...

Quality function deployment in the speculative house-building market: how to satisfy high-income customers

This paper presents a study that reports a detailed process of ‘quality function deployment’, considering an ultra-luxury villa project. It is based on a questionnaire survey that was applied to 42 residents and seven top managers. The results highlight real expectations of high-income residents. Residents were not satisfied with the ‘sauna’, ‘sports areas’, and ‘fitness centre’ despite the fact that these were among the least important expectations. However, residents were satisfied with the ‘security of the complex’, ‘architectural design’, and ‘quality of the end-products’. If some expectations (i.e. ‘areas for common use’, ‘playing areas for children’, and ‘quality of the end-products’) achieve better technical standards in the next projects, demand for luxury residences will likely be improved. Consequently, 25 expectations and corresponding findings constitute a preliminary framework for an expectations agenda for such projects for builders who wish to improve marketing practices.

A semiotic analysis of cartoons about occupational health and safety issues in the construction workplace

The construction industry in developed and developing countries is almost always among industries with poor safety records. In decreasing the numbers of safety incidents, society’s perception of construction workers, who are the central part of the occupational health and safety issue, can be an important learning tool for these workers in terms of self-criticism. Therefore, society’s perception of the responsibility of workers for occupational health and safety is presented by means of cartoons. For this objective, seven cartoons exhibited in the International Construction Accidents Cartoon Contest held in Turkey are examined through the General Theory of Verbal Humour, a semiotic analysis method. As the main finding, construction-based occupational health and safety perceptions of countries were found not to change significantly. Consequently, these results can have a function in guiding workers and worker unions to revise and manage the general perception of society about them. Moreover, such cartoons can be used as a lingua franca for occupational health and safety training in international construction projects where multinational migrant workers are employed.

Quantification of fresh ready-mix concrete waste: order and truck-mixer based planning coefficients

ABSTRACT This paper reports a study of order and truck-mixer based planning coefficients used to avoid or utilise fresh concrete waste. To achieve this objective, an original calculation procedure was proposed to quantify the fresh concrete waste, and direct quantitative measurements were performed in three batching plants in Turkey. Data obtained were analysed by descriptive statistics, one-way analysis of variance, and hypothesis testing. As a result, clients may order 8.57% more of their concrete needs instead of using much wider margins to avoid over-ordered concrete. They may also reserve 8.96% of their concrete needs in other batching plants to compensate their possible extra concrete requirements. Based on these numbers, concrete amount and cost may be better estimated, and thus, the over-ordered concrete may be eliminated. Finally, leftover concrete amount was found to be 0.33% of total concrete in a truck-mixer and to be in a relationship with the number of arrivals of a truck-mixer in an order. Through these findings, potential conflicts between contractors and concrete suppliers about the amount of delivered concrete may be prevented. Also, batching plants may save concrete and benefit from recycling. Overall, natural resources and energy may be consumed less and environmental pollution may be prevented.

Industry-wide competitiveness assessment through fuzzy synthetic evaluation: the case of cement industry

This study aims to develop a fuzzy force assessment model (FFAM) for quantifying industry-wide competition conditions (CCs) using five-force framework. It employed fuzzy synthetic evaluation to assess CCs of forces and industry, and real case of Turkish cement industry was demonstrated. As a result, FFAM provides a comprehensive and practical device. As empirical findings, CCs in cement industry are medium-to-high, and pressure from substitutes is the most effective force, followed by intensity of competitors’ rivalry, bargaining power of buyers, bargaining power of suppliers, and threat of entrants. Consequently, this study is first to propose a structured and fuzzy five-force quantification model and to assess CCs in cement industry.

Bulanık veri zarflama analizi ile beton pompası seçimi

Bu calismanin amaci, insaat sektorundeki makine secimleri problemine, beton pompasi acisindan yaklasmak ve beton pompasi ureticileri ve kullanicilarina, uretim ve satin alma sureclerinde yardimci olabilecek bir yontem ortaya koymaktir. Bu kapsamda, cok olcutlu karar verme problemlerini cozmek icin kullanilan yontemlerden biri olan veri zarflama analizi, elde edilen verilerin bazilarinin bulanik sayilar olmalari nedeniyle, bulanik veri zarflama analizi (BVZA) olarak kullanilmistir. Hesaplamalarda hem bulanik ve hem de normal sayilari ayni anda isleyebilmek icin Madea ve digerleri (1998) tarafindan gelistirilen ve Saati ve digerleri (2002) tarafindan iyilestirilen α-kesim kumeleri yaklasimindan faydalanilmistir. Calisma kapsaminda, Turkiye’de faaliyet gosteren uc farkli beton pompasi ureticisi tarafindan uretilen ayni tipteki birer adet beton pompasinin ozellikleri ve beton pompasi kullanicisi 70 adet firmanin makine sorumlulari ile yapilan gorusmelerden elde edilen veriler kullanilarak, soz konusu beton pompalarinin etkinlikleri hesaplanmistir. Bu etkinlik hesaplamasi sirasinda Charnes-Cooper-Rhodes yontemi ile elde edilen esitlikler kullanilmistir. Sonuc olarak, degerlendirmeye alinan uc farkli beton pompasi icerisinden B3 kodlu beton pompasi, etkinlik degeri en yuksek olan secenek olarak belirlenmistir. Bu calisma sonucunda elde edilen bulgularin; beton pompasi ureticilerinin pazardaki durumlarini gormelerine, urunlerini gelistirerek rekabet guclerini artirmalarina ve potansiyel alici ve kullanicilarin en uygun urunu secmelerine yardimci olabilecekleri dusunulmektedir. Ayrica BVZA’nin, cok olcutlu karar verme problemlerinde karsilasilan farkli tur ve birimlerdeki verilerin, mevcut kisitlarla birlikte degerlendirilmesinde kullanilabilecek oldukca faydali bir yontem oldugu ortaya konulmustur. Bu yontem ile bir veya birden cok parametre hedeflenerek hesaplamalar yapilabilmekte ve karar verme surecinde avantaj saglanabilmektedir.