Resource Leveling of an Industrial Building Using Genetic Algorithm Technique

Construction companies should schedule their projects in a manner that considers theefficient use of limited resources in order to complete a project within estimated budget, onschedule and in compliance with the specifications. In this context, the planning of resourcesbecomes crucial for a construction project, which can be accomplished by resource leveling.Resource leveling - also known as resource smoothing - is a method that attempts to reducethe fluctuations in resource usage in order to make the resource requirements as uniform aspossible while maintaining the original project duration. The studies dealing with resource leveling problems can be classified into two categories, which are; (1) analytical methods and(2) heuristic methods. Analytical methods may give optimal solutions on small-scaledproblems; however, they are inadequate in large-scaled problems. As a result of theweaknesses of analytical methods, many studies have been conducted in order to developmore efficient models by heuristic methods. Genetic algorithm-based resource leveling is oneof these models, which is developed to attain better solutions. The main objective of thisstudy is to handle the resource leveling problem of an industrial building using geneticalgorithms. In this context, a schedule for an industrial building is established using theCritical Path Method (CPM). The information about the logical constraints and the resourcesrequired to carry out activities were obtained through the interviews with civil engineers fromthe company, whose expertise is on industrial buildings. The proposed genetic algorithmbased resource leveling model attempts to improve the schedule. The developed modelprovided a decrease of 20% in the total resource-days required to complete the project. Thestudy is of benefit to participants of construction industry, because it makes them aware of the potential use of the combination of critical path method and genetic algorithms in order to solve the resource leveling problem

Impacts of Diverse Crop Rotations and Integrated Crop-Livestock System on Soil Quality in South Dakota

Crop diversification can be beneficial in improving soil quality parameters. Diverse crop rotations and integrated crop-livestock systems (ICLS), are two examples of crop diversification used in this study to assess soil quality. The objectives of this study were to: (i) assess the impacts of diverse rotations on soil quality parameters, and (ii) assess the impacts of low and high stocking density on soil quality parameters. Both of the studies were conducted separately and are presented as two different chapters. To accomplish objective (i), a long-term experiment was selected which was established near Brookings, South Dakota, USA at USDA-ARS lab in 2000 on a Barnes (Fine-loamy, mixed, superactive, frigid Calcic Hapludoll) soil. Treatments selected for this study included five crop rotations: (i) 2-yr, corn (Zea mays)-soybean (Glycine max) (CS), (ii) 4-yr, corn-pea (P. sativum)-winter wheat (T. aestivum)-soybean (CPWwS), (iii) 4-yr, corn-soybeanspring wheat-pea (CSSwP), (iv) 4-yr, corn-soybean-spring wheat-sunflower (Helianthys) (CSSwSu), (v) 4-yr, corn-oats-winter wheat-soybean (COWwS) with four replications. Soil samples were collected in the spring after 12 and 16 years of cropping (2013-2017) at two sampling depths (0-5 cm and 5-15 cm). Results indicated that a previous crop, winter wheat under COWwS rotation had the highest soil organic carbon (SOC) content with 22.7 g kg-1 compared to other previous crops at the 0-5 cm depth. Also, previous crop of oat under COWwS rotation had significantly lower bulk density (BD) content than other crops. Additional soil quality parameters were analysis utilizing the Soil Management Assessment Framework (SMAF) tool. The COWwS and CSSwP rotations increased the soil quality compared to the CS, CPWwS and CSSwSu rotations. This study showed the benefits of using the long-term impacts of diverse crop rotations on soil quality parameters. To accomplish objective (ii), an on-farm assessment of soil quality was assessed at four producers’ farms where the specific objective to assess the impact of low and high stocking rates under ICLS on soil quality parameters such as bulk density, pH, soil nutrient parameters (N, P, K, Na, Ca, and Mg), soil organic carbon and nitrogen, and microbial biomass carbon. The four farms were located at: (i) Roscoe, (ii) Gettysburg, (iii) Raymond, and (iv) Selby in South Dakota. Each farm location included two different treatments; grazing cover crops under ICLS and control treatment without grazing. Soil samples were collected from 0-5, 5-15, and 15-30 cm depths in June 2017 and 2018. Study results showed that low stocking rate under ICLS at Roscoe increased soil organic carbon (SOC) from 20.7 to 28.2 g kg-1, total nitrogen (TN) from 2.06 to 2.60 g kg-1, and microbial biomass carbon (MBC) from 72.7 to 241.8 μg g-1 at the surface 0-5 cm depth. However, high stocking rates under ICLS at Gettysburg and Selby sites decreased the SOC. Additional analysis of the parameters was conducted to assess the soil quality index (SQI). Data showed that the low stocking rate under ICLS improved the soil quality index (SQI) while the high stocking rate under ICLS decreased the SQI. This study showed that ICLS with low stocking density can be beneficial in enhancing soil quality at the farm scale. In conclusion, the present study showed that crop diversification can be beneficial in enhancing soil quality, however, long-term assessments are needed that include different diverse crop rotations with cover crops, and different stocking rates and cover crops under ICLS, and monitoring different soil quality parameters, crop yield, and economics

A Grading System-based Model for Detecting Unbalanced Bids during the Tendering Process

Unbalanced bidding is a common practice used in both unit price and lump sum contracts. Contractors may unbalance their bids in different forms for various reasons. The studies in the literature either focus on developing optimization models that assist contractors in winning contracts and maximizing profits of their bids through unbalancing or developing models that assist owners in detecting and/or preventing unbalanced bids during the bid evaluation stage. Unbalanced bidding is one of the most controversial subjects in the construction management literature and practice. Although there is no consensus on whether it is unethical or not, this practice is not usually for the benefit of owners. Therefore, owners have the right to reject the unbalanced bids and create a fair competition environment if they have a mechanism to detect it during the bid evaluation process. The main objective of this study is to propose a model, which consists of five different grading systems and helps owners in detecting unbalanced bids during the tendering process. In the proposed model, owners may either calculate the individual grades of each bidder or calculate the final score of each bidder by assigning different weights to these grading systems according to the project characteristics or their own needs. The final scores and bid prices of the contractors can be simultaneously evaluated. In order to demonstrate the applicability of the proposed model, an illustrative example is presented. It can be concluded that the proposed model can be effectively and easily used by owners for detecting unbalanced bids. This paper is the revised version of the paper that has been published in the proceedings of the Creative Construction Conference 2018 (Polat et al., 2018)

Structural System Selection Using the Integration of Multi-Attribute-Decision-Making (MADM) Methods

A structural system carries all loads acting on the building and transfers them effectively to the soil through the foundation. Since it is the essential component of a building, selecting the most appropriate structural system is one of the critical decisions in the structural design. The design team, which consists of engineers and architects, is responsible for determining the structural system that will satisfy the owner's and end user's needs as well as the legal requirements. Due to the fact that a number of compromising and conflicting criteria may affect the structural system selection process, it is a difficult task and it should be considered as a multi-attribute-decision-making (MADM) problem. The main objective of this study is to provide the design teams with a MADM approach that will assist them in selecting the most appropriate structural system in a more objective and systematic manner. In the proposed approach, analytic hierarchy process (AHP) is used to compute the weights of the criteria and Vise Kriterijumska Optimizacija I Kompromisno Resenje (VIKOR) is employed to rank the structural system alternatives. In order to demonstrate how the proposed can be applied in a real life problem, the structural system of a housing project in Istanbul, Turkey is selected via this approach. The findings of the model were discussed with the decision making team in the studied project and they stated that the proposed approach could be easily employed as a guideline in selecting the most appropriate structural system from the managerial viewpoint. This paper is the revised version of the paper that has been published in the proceedings of the Creative Construction Conference 2018 (Polat et al., 2018)

Impacts of different objective functions on resource leveling in construction projects: a case study

A review of the recent literature on the models that focus on resource leveling in Critical Path Method networks shows that different objective functions have been used to optimize resource utilization. The main objective of this study is to investigate the impacts of using different objective functions on resource utilization histograms in Critical Path Method networks. For this purpose, nine different resource leveling objective functions were optimized via a genetic algorithm-based model. The model was developed using actual data obtained from a steel framed industrial building construction project. It was found that each of these objective functions generates different resource utilization histograms. In order to determine the improvement levels achieved by resource leveling using nine different objective functions, the improvement percentage in each parameter and the average improvement percentage for each objective function were calculated. Even though the objective function that involves the minimization of the sum of the square of the deviations in daily resource usage provided the best average improvement percentage in the studied case, another objective function(s) may provide better average improvement percentage in different projects. The contractor should consider all objective functions for resource leveling and select the one(s) that provides the best average improvement percentage

Motivation of civil engineers and architects in Turkey

Motivation is one of the key factors that stimulate individuals to improve their productivity. Therefore, motivation of construction workers has been debated with considerable interest by participants in the construction industry. However, motivating only construction workers, but ignoring the motivation of construction professionals, viz., architects and civil engineers, may not be enough to successfully complete a construction project. Although motivation of construction professionals may also enhance the performance of a construction project, this topic is mostly ignored in the motivation literature. This study attempts to fill this gap by (1) identifying the motivators that are of importance to architects and civil engineers and (2) exploring the statistical difference between architects’ and civil engineers’ motivators. For this purpose, a questionnaire survey was administered to Turkish architects and civil engineers to collect data on their perceptions of the importance of different motivators. The case of Turkey is investigated because several of the larger Turkish contractors undertake construction projects outside their home country. Statistical analysis was performed on the collected data to verify whether there are statistically significant differences in the perception of some motivators by architects and civil engineers. The study demonstrates the existence of a statistically significant difference between architects’ and civil engineers’ motivators. Identifying the architects’ and civil engineers’ motivators may help construction companies in motivating their architects and civil engineers more effectively, thus developing a quality workforce

Detecting unbalanced bids via an improved grading-based model

Unbalanced bidding, also known as skewed bidding, is the process of increasing and/or decreasing the prices of various bid items without altering the total offered bid price. Bids can be unbalanced either mathematically (front-end loading) or materially (quantity error exploitation). Owners should be very careful when evaluating the tenders as awarding a contract to an unbalanced bid may result in severe cost overruns because the prices of those items do not reflect their true costs and markup allocations. Unbalanced bidding is still a contentious issue in the construction industry. While some researchers consider it as a legal bidding strategy in such a fierce competitive business environment, others view it as an unethical practice and claim that unbalanced bids should be disqualified. Studies regarding unbalanced bidding can be categorized into two groups: (1) the ones focusing on detecting or preventing this practice to help owners; and 2) the ones focusing on optimizing unbalanced bidding to help contractors. This study aims to develop a model, which consists of eight grading systems, to assist owners in detecting materially unbalanced bids. The proposed model is the improved version of the previous model, which was composed of five grading systems. In order to demonstrate how this grading-based model can be used by owners, an illustrative example is presented. It was found that owners can easily and successfully detect unbalanced bids via the proposed mode