Assembly Yard Research Articles

A Mathematical Formulation and a Heuristic for the Spatial Scheduling of Mega-Blocks in Shipbuilding Industry

Abstract In shipbuilding industry, to reduce the staying time of the ship in a dock, floating crane and floating dock are used to handle the mega-blocks, thus it increased the turnover of the dock. Therefore, spatial scheduling for mega-block in an assembly yard becomes important in shipbuilding industry. However, spatial scheduling of mega-blocks has some unique characteristics compared with the well-known classic bin-packing problem, and not many studies can be found on this issue. This research proposes an enhanced mathematical formulation and a heuristic algorithm for spatial scheduling of mega-block arrangement problem. The formulation provides tight bound compared with the existing formulation, and the proposed heuristic can obtain good quality of the solution in a reasonable amount of time even when the size of the instance became large. Introduction Shipbuilding industry involves constructing ships and other floating vessels. Block is a base element of the shipbuilding process, and the blocks are assembled and welded in the block assembly shop, and finally erected to a ship in a dry dock. A size of a block is around 15~30 meters with a weight of around 30~300 tons (Zheng et al. 2011), and a large ship consists of around 150 blocks (Koh et al. 2011b). Some blocks are outsourced and timely delivery and quality of blocks have an absolute impact on the ship’s quality. Also, it is possible to shorten the dock duration by receiving blocks from several companies at the same time.

Use of accelerometers to assess and describe trailer motion and its impact on carcass bruising in market cows transported under North American conditions.

Increased trailer motion, coupled with large accelerations and decelerations, has been associated with decreased carcass quality and increased stress indicators in cattle, sheep, and hogs. However, motion of livestock trailers has not been measured in North-American cattle semi-trailers over long distances (> 1000 km). The objectives of this study were to develop a practical method of measuring transport trailer accelerations, to describe the range of accelerations cattle are exposed to under North American conditions, and to conduct a preliminary analysis of trailer accelerations for each compartment and its effect on carcass bruising. The root mean square (RMS) of acceleration was measured at a sampling rate of 200 Hz in 3 orthogonal axes; x (vertical), y (front-to-rear), and z (lateral; side-to-side) by clamping an accelerometer to the cross beam below each of the five compartments of 8 trailers transporting a total of 330 animals (674 ± 33.3 kg BW) from an assembly yard to a processing facility. Journeys took place on separate days and ranged in duration from 13 to 15.7 h. The number and severity of bruises per carcass were determined prior to trimming for n = 290 carcasses and the number of bruises per carcass ranged between 0.38 and 12.75, whereas the bruising score per carcass ranged between 0.38 and 14.88. Mean number of bruises and severity of bruises (bruising scores were assigned according to size using a three-point scale: 1) ≤ 6.5 cm, 2) 6.5 to 12 cm, and 3) ≥ 12 cm and bruising severity was determined by applying the weighted score to each bruise according to bruise area) per carcass was 4.52 ± 2.43 (n) and 5.31 ± 2.84, respectively. Accelerations in commercial transport vehicles were found to range between 0.33 and 1.90 m/s2, whereas the mean RMS of acceleration for all trailers (n = 31 accelerometers) was 1.01 ± 0.32 m/s2, 0.72 ± 0.31 m/s2, and 0.97 ± 0.30 m/s2 for the x, y, and z axes, respectively. Horizontal acceleration was greatest in the nose, back, and doghouse compartments (P = 0.05), whereas lateral acceleration was greatest in the nose and back compartments (P = 0.08). Although the nose, back, and doghouse compartments had the highest RMS values for the lateral and horizontal axes, there were no significant relationships between bruising and acceleration. Replication of this research is required to further understand the relationships between trailer motion, carcass bruising, and overall animal welfare in cattle transported long distances.

Evaluating industrial modularization strategies: Local vs. overseas fabrication

Modularization is becoming more popular in industrial construction to enhance various project management aspects, including time, cost, safety, quality, and productivity. Although many studies have highlighted the differences between modular and conventional (stick-built) construction, little research is conducted to evaluate alternative fabrication strategies (e.g., overseas versus local fabrication). Some practitioners prefer to build modules locally, while some others prefer to outsource the module fabrication overseas and ship them to the industrial plant. This dramatically affects the decision on the size of the module envelope, and in turn, many other associated factors. The purpose of this study is to develop an integrated framework to evaluate different module fabrication strategies. This study employs various automation tools (e.g., building information modeling (BIM), simulation modeling) to quantify the impact of module fabrication strategies on any selected industrial project. The proposed framework considers various project aspects such as shipment and handling, fabrication, lifting, module resizing, and module assembly yard to find the best fabrication strategy. An actual case study, part of an industrial plant in Alberta, Canada, is presented in this paper to elucidate research contributions.

Genome wide analysis of the evolution of Senecavirus A from swine clinical material and assembly yard environmental samples.

Senecavirus A (SVA), previously known as Seneca Valley virus, was first isolated in the United States in 2002. SVA was associated with porcine idiopathic vesicular disease in Canada and the USA in 2007 and 2012, respectively. Recent increase in SVA outbreaks resulting in neonatal mortality of piglets and/or vesicular lesions in sows in Brazil, the USA and Canada point to the necessity to study the pathogenicity and molecular epidemiology of the virus. Here, we report the analysis of the complete coding sequences of SVA from 2 clinical cases and 9 assembly yard environmental samples collected in 2015 in Canada, along with 22 previously released complete genomes in the GenBank. With this combined data set, the evolution of the SVA over a 12-month period in 2015/2016 was evaluated. These SVA isolates were characterized by a rapid accumulation of genetic variations driven mainly by a high nucleotide substitution rate and purifying selection. The SVA sequences clustered in clearly defined geographical areas with reported cases of SVA infection. No transmission links were identified between assembly yards, suggesting that point source introductions may have occurred. In addition, 25 fixed non-synonymous mutations were identified across all analyzed strains when compared to the prototype SVA strain (SVV-001). This study highlights the importance of monitoring SVA mutations for their role in increased virulence and impact on SVA diagnostics.

Combining photogrammetry and robotic total stations to obtain dimensional measurements of temporary facilities in construction field

Abstract Background Three-dimensional (3D) modeling and visualization of temporary site facilities is instrumental in revealing potential space conflicts and refining time and cost estimates. This research focuses on implementation of photo-based 3D modeling in a time-dependent, dynamically-changing context. Methods We propose a cost-effective modeling technique to obtain dynamic dimension measurements of a moving object. The methodology resulting from integrating photo-based 3D modeling and robotic total station tracking technologies better caters to the application needs of visualization and measurement in construction that are critical to operational safety and structural accuracy. The computational foundation of photogrammetry is first addressed then the modeling procedure and the system design described. Results In a module assembly yard, a rigging system being lifted by a mobile crane was identified as the moving object. The length and the length changes of twelve slings on a newly-engineered rigging system at different stateswere measured in order to ensure quality and safety. Conclusion The proposed technique relies on utilizing two robotic total stations and three cameras and provides a simple, safe and effective solution to monitor the dimensional changes of a temporary facility in the construction field.

Spatial scheduling for shape-changing mega-blocks in a shipbuilding company

To overcome space restriction and to increase productivity, some shipbuilding companies use floating-docks on the sea instead of dry-docks on the land. In that case, a floating-crane that is capable of lifting very heavy objects (up to 3600 tons) is used to handle the blocks which are the basic units in shipbuilding processes, and therefore, very large blocks (also called mega-blocks) can be used to build a ship, but because there are some positional restrictions under which the mega-block assembly yard can be constructed, the space is the scarcest resource in the process. The focus of the research reported in this paper is to develop an efficient spatial schedule for the mega-block assembly yard. First, we develop a length-time two-dimensional packing model for this problem. Since the optimisation model cannot be solved using an analytical method, we propose a GA-based heuristic algorithm using computational geometry theory. Through performing a series of computational experiments, we finally show that the proposed spatial scheduling algorithm can provide solutions of good quality very efficiently.

조선소의 메가블록 조립작업장을 위한 공간계획알고리즘 개발

To mitigate space restriction and to raise productivity, some shipbuilding companies use floating-docks on the sea instead of dry-docks on the land. In that case, a floating-crane that can lift very heavy objects (up to 3,600 tons) is used to handle the blocks which are the basic units in shipbuilding processes, and so, very large blocks (these are called the mega-blocks) can be used to build a ship. But, because these mega-blocks can be made only in the area near the floating-dock and beside the sea, the space is very important resource for the process. Therefore, our problem is to make an efficient spatial schedule for the mega-block assembly yard. First of all, we formulate this situation into a mathematical model and find optimal solution for a small problem using a commercial optimization software. But, the software could not give optimal solutions for practical sized problems in a reasonable time, and so we propose a GA-based heuristic algorithm. Through a numerical experiment, finally, we show that the spatial scheduling algorithm can provide a very good performance.

The Gjøa Semi: a North Sea project relevant for Western Australia

Gjøa was the largest field development project in Norway in 2010. Gjøa was proven in 1989 and are now being developed together with nearby Vega satellites. The combined reserves are estiThe recent Gjøa field development in the North Sea has many features that are relevant for the oil and gas developments north of Western Australia. While the field location is not very similar to the north of Western Australia, the field development solution is very relevant. Several subsea clusters are tied back to a semi-submersible platform with export of gas and condensate via pipelines to shore. Other aspects to the project that are relevant to Western Australia are split location engineering between Norway and India, fabrication of the hull in Korea and subsequent heavy lift transport to the assembly yard, pre-installation of the mooring system, and tow to field with ocean going tug boats. The semi concept, which was used for the Gjøa development, is a mature technology with few technical challenges on a conceptual level. On the other hand the building of an oil and gas platform for A$2 billion has many challenges, both economical and technical, that have to be solved to have a successful project for both the client and the contractor.

The Key Technology of Skew Continuous Prestressed Concrete Box Girder Bridges with Incremental Launching Method

Incremental launching method is a construction technology for prestressed concrete continuous bridges widely used in China. In the incremental launching method, the superstructure of a bridge is erected from one side of bridge longitudinally to the opposite bank. Compared with other technology for bridge erection methods, it may reduce the cost of labor, shorten the construction period and save the assembly yard. So it is a competitive construction method for medium-span prestressed concrete continuous bridges. A large number of skew bridges will be built especially at mountain area, so it is very necessary to research on incrementally launching method for skew bridges. The objective of the study presented in this paper is to introduce the method used in the Lishui Bridge in Zhangjiajie city of China.

The effect of transport time from the assembly yard to the abattoir and resting time at the abattoir on pork quality

Over 1900 pigs, supplied by two producers, were first delivered to an assembly yard and then transported to a commercial abattoir. Transport times were 50 min and 2 h, and resting periods at the abattoir were < 30 min, 3 h and 6 h. Times were chosen to represent normal practices in Ontario. The colour and structure of the boneless loins were as sessed subjectively 24 h postmortem. The shorter (50 min) transport time was associated with the highest (P ≤ 0.05) incidence of pale and soft/exudative loins. A longer transport time reduced the incidence of pale and soft/exudative loins; it also increased (P ≤ 0.05) the incidence of dark and firm/dry loins; particularly during winter. A resting period of < 30 min resulted in the highest (P ≤ 0.01) incidence of pale and soft/exudative loins. A 3 h resting period significantly improved (P ≤ 0.01) quality by reducing the incidence of pale loins and soft/exudative loins. Extending the resting period from 3 h to 6 h provided inconsistent improvements in quality due to interactions with season (P ≤ 0.05) and producer/management (P ≤ 0.05). Considering transport time and resting period together further highlighted the importance of resting period at the abattoir. Three h resting period always improved (P ≤ 0.05) quality regardless of transport time, season or producer. Key words: Transport, resting period, pork quality, pale, soft and exudative, DFD

Profit-Oriented Production Strategy in Shipyards

The profitability of a shipyard depends to a great extent on its production costs. A low-cost building strategy could be based upon cutting a production capacity that could not be continuously employed in executing the shipyard's production program. One of possible models of build strategy targeting is related to the organization of a ship assembly yard as a yard entrepreneur and its independent partners/subcon-tractors. The relationship between these entities during the different building phases has to be defined in terms of the designs and drawings coming from the work preparation process. The flow of main documents is discussed as well as the means of subcontracting during several phases of the process.

Experience in enlargement assembly of a semigantry crane on an outside assembly yard at the Sayano-Shushenskoe hydroelectirc station

Experience in enlargement assembly of a semigantry crane on an outside assembly yard at the Sayano-Shushenskoe hydroelectirc station