For the first time in the history of architecture, Antonio Gaudí used structural elements based on complex ruled surfacesbeyond traditional conical or cylindrical surfaces -, catenary vaults or branched pillars, in order to increase the structural efficiency of his buildings. The catenary arch had been used only in the construction of bridges by a few engineers, starting in the 18th century. Arata Isozaki said that the "scale model and the structural analysis of the church at the Güell Colony are the most original in the history of architecture". Beyond his artistic and creative geniuswhich has now been widely studied and acknowledged -Gaudí was a revolutionary architect, whose experimental approaches to the design and calculation of structures implied a focus that was so far ahead of its time that later, hugely significant engineers and architects have coincided with the methods and systems used by Gaudí half a century earlier. Norman Foster said in reference to Gaudí: "his methods, a century later, are still revolutionary".

Due to the high risk seismic in many zones of Mexico it has been observed that the ground motions often show large horizontal displacement. This displacement causes large deformations of buried pipelines. Then, the knowledge of study and design recommendations related to deformability of the pipes has not been sufficiently provided. A grand number of studies have been reported concerned about the plastic deformations or buckling of the straight pipe. Most of them are performance of column pipe without internal pressure. Therefore, in this work are analyzed the steel straight pipes, for the purpose of clarifying the deformations of the pipes with internal pressure under large displacement and bending. Effect of internal pressure on deformability of pipe is investigated both under load bending. Stress analysis using FEM is performed in order to simulate the large deformations of the pipes.

The growing need to satisfy the national oil industry demand has required the evaluation and retrofit of the existing pipelines, in addition to create new risers for transportation and distribution of oil products. The current development of offshore structures requires better designs of the risers capable to assuring an optimal level of security. It is common to get situations, in the performance of fixed offshore platforms, in which risers might be found with lowly internal pressure or empty due to maintenance or repairing. This condition could represent an unfavorable situation that might become highly critical given the conditions they are found in. Therefore, this research is focused to study the mechanical behavior and their structural integrity of the pipelines such as, risers with helicoidally welds under combined load (external pressure, bending moment and axial compression). In particular, for safety prediction, the failure modes and uncertainties involved in each loading condition need to be incorporated in the analysis in order to specify the pipelines use thresholds that keep them over acceptable safety levels within their operating lifetimes.

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