José Manuel Gordo

Welded structures are subjected to internal residual stress after manufacturing that may affect the structural strength and normally are associated with an increase on initial geometrical imperfections. This study presents a simplified method to generate an adequate representation of residual stresses on Finite Element models for structural analysis of thin-walled structures and other applications. The results obtained shown that the methodology proposed to introduce residual stresses is simple, accurate and efficient on the modulation of post-welding stresses and their pattern, thus it may be used for simulation of the thermal process.

The present work studies the concept of productivity in shipbuilding and how it should be measured. The existing metrics, shipbuilding process and shipyard organization were studies in order to choose the most adequate metrics which would allow the measuring of a shipyard productivity in a systematic and holistic way. This is achieved by gathering the man-hours spent in each ship organized by cost centre and using Compensated Gross Tonnages as the measure of output from the shipyard. Data was gathered for thirty ships built in the same European yard organized by cost centre. From the data collected it was found that the ratio of hours spent in outfitting to the hours spent in structures is proportional to the complexity of the ship. There was also opportunity to study the work reduction resulting from building ships in series and the shares of labour for ships series and across ship types.

A robust methodology to simulate virtually the residual stresses pattern in welded steel plates is presented. The methodology is applied to the structural analysis of typical welded plates belonging to ship structures, and the effect of residual stresses on the elastoplastic behavior of plates loaded axially is analyzed in comparison to the residual stress free case, both for tension and compression and including initial imperfections. Residual stresses affect in different manner plates with different geometries; thus a parametric study is performed covering the usual range of variation of the most important plate parameters that control the strength of the plates, more precisely the slenderness and the aspect ratio. The results from finite elements analysis are compared with codes and most established formulations and recommendations of applicability in the prediction of load-shortening curves for hull’s bending strength evaluation, ultimate strength and ultimate strain of plate elements are made.

Welded structures are subjected to internal residual stress after manufacturing that may affect the structural strength and normally are associated with an increase on initial geometrical imperfections. This study presents a simplified method to generate an adequate representation of residual stresses on Finite Element models for structural analysis of thin-walled structures and other applications. The results obtained shown that the methodology proposed to introduce residual stresses is simple, accurate and efficient on the modulation of post-welding stresses and their pattern, thus it may be used for simulation of the thermal process.

A robust methodology to simulate virtually the residual stresses pattern in welded steel plates is presented. The methodology is applied to the structural analysis of typical welded plates belonging to ship structures, and the effect of residual stresses on the elastoplastic behavior of plates loaded axially is analyzed in comparison to the residual stress free case, both for tension and compression and including initial imperfections. Residual stresses affect in different manner plates with different geometries; thus a parametric study is performed covering the usual range of variation of the most important plate parameters that control the strength of the plates, more precisely the slenderness and the aspect ratio. The results from finite elements analysis are compared with codes and most stablished formulations and recommendations of applicability in the prediction of load-shortening curves for hull’s bending strength evaluation, ultimate strength and ultimate strain of plate elements are made.

To improve the shipbuilding process and obtain a more cost-effective production, several approaches are used today. The state of the art approach is based on newer production technologies, mainly steel cutting and welding technologies,...

The results of a four points bending test on a box girder are presented. The experiment is part of series of tests with similar configuration but different thickness, spacing between longitudinal stiffeners and span between frames. The present work refers to the stockiest plate box girder with a plate’s thickness of 4 mm and a span between frames of 800 mm. The experiment includes initial loading cycles allowing for residual stresses relief. It also includes a series of cycles close to collapse load allowing the analysis of linear characteristic at high levels of load. The moment curvature relationship is established for a large range of curvatures. The ultimate bending moment of the box is evaluated and compared with the first yield moment and the plastic moment allowing the evaluation of the efficiency of the structure. The post buckling behavior and collapse mode are characterized. Comparison of the experiment with a progressive collapse method is made taking into consideration the effect of residual stresses on envelop of the moment curvature curve of the structure.

The international competition in shipbuilding is a subject that weighs heavily in new ships orders and leads to the study about the feasibility of adopting new technologies and processes in the production flow, in order to respond to the current challenges. Thus, a program was developed to forecast times and costs in the construction processes stages of ship blocks in a shipbuilding yard, allowing the simulation of implementation of alternative cutting and welding technologies. The main goal of this study is to understand the relation between operational and labor costs in various types of cutting and welding technologies, and the potential earnings related to cost savings in downstream stages of the production flow due to the application of higher quality technologies in upstream processes. The times and cost values computed by the developed algorithm grant a deeper understanding of the consequences of the adoption of alternative shipbuilding technologies in the productive process.

This study analyses the structure of costs of several processes associated with the shipbuilding industry. The analysed productive processes are: cutting preparation procedures, steel plate cutting processes, processes of hull plates and...