Inflatable marine structures are flexible cylindrical structures attached to a rigid base. These structures are generally cylindrical tubes, made of rubberized material, and inflated by air and/or water. Although these structures are permanently inflated, they have the advantage of being deflated and lie flat when not needed and then, inflated in a short period when required. They are relatively easy to install, do not corrode, require little maintenance, and have the capability to withstand extreme temperatures. Due to elasticity of the structure and continuous variation of its shape during operation, inflatable breakwater or sea-wall structural and hydraulic analyses are more complicated than the rigid types. Large deformation of the membrane due to the internal and external loads makes the governing equations of such problems non-linear and complex. In the present study, the behavior of an inflatable marine structure under loading by marine waves was simulated based on 2D numerical modeling. For this purpose, the deformed equilibrium geometry of the breakwater was calculated by solving the prevailing equations through the linear dynamic response of the system. The central difference method was employed to solve the governing equations of the linear dynamic response of the system of finite elements. According to the results of former studies, for 2D modeling of the aforementioned problem, the length of the tube was assumed infinity. Therefore, the effects of lateral supports and boundary conditions were neglected. This study carried out the numerical analysis of the inflatable marine structures for solving the flow-based problem associated with static and dynamic structural analyses. For this purpose, the two-dimensional fluid-structure interactions were analyzed numerically. It was shown that the equilibrium shape of the structure was a function of rubber thickness, elasticity modulus of the material, internal pressure, the dam foot width, and external loads. All the influential parameters of both flow and structure including internal pressure, water depth, wave height, wave period, etc. were attained based on the dimensional analysis. Accordingly, the results describing height and cross-sectional profile of the inflatable tubes loaded by marine waves were obtained.

Reliability analysis of steel structures subject to seawater corrosion is of considerable interest for coastal and offshore marine steel structures. These are often very expensive and have high consequential costs and implications should failure occur. Since corrosion of steel structures causes deterioration of structural strength, usually gradually with time, safety assessment is of considerable importance for new structures (those in the design stage) and also for those which are already in operation.Marine corrosion is a complex phenomenon and subject to various influencing factors each of which has its own inherent uncertainty. In any safety assessment, in principle, the uncertainty of each factor should be studied and taken into account. Since such an action is too difficult, in practice some test programs are normally conducted and all uncertainties caused by different factors are assumed to be included in the relevant corrosion measurements.In addition, in any corrosion reliability analysis for steel structures exposed to seawater, two different models must be taken into consideration: (1) A physical model indicating general corrosion behaviour as a function of exposure time and (2) A stochastic model describing probabilistic treatment of uncertainties observed in real corrosion data. The first has been traditionally treated by invoking a simple power law and in particular a linear relationship. However, using realistic long-term data, validity of such a model has recently been challenged. The second model (i.e. probabilistic modelling of corrosion process) has been dealt with in literature in different approaches, including either taking the corrosion annual rate as a random variable or proposing a stochastic process such as Gamma process. This is usually proposed as a general structural deterioration process. The second approach provides, doubtlessly, better treatment of corrosion uncertainties; however it can be shown unfortunately that the Gamma process is unable to reflect the corrosion uncertainties in some circumstances.In this paper, two sets of corrosion data collected in different seawaters around the world with different temperatures are used. This requires processing of data in such a way that the data sets remain consistent with each other and that outcome is data that can be considered as belonging to one statistical population. Herein, first, a simple algorithm is proposed to transform the whole data to one common temperature. Second, a novel Markov-chain based model is developed which meets long term second-order corrosion statistics (i.e. means and standard deviations of corrosion losses). It is based on a corrosion model that previously has been calibrated extensively to field observations of corrosion and to literature-reported realistic data. Although actual long-term field observations of marine corrosion of steel are scarce, it is shown that particularly for the standard deviation the new model is well capable to be consistent with the long-term data.It is noted that herein, only the corrosion data collected in marine immersion zones are considered (i.e. those taken in splash zones and atmospheric zones are not considered). Further, only general corrosion (i.e. not pitting corrosion) is accounted for herein. These two issues, obviously, have to be addressed separately.

Puducherry is a coastal region in India where the growth of Ulva fasciata (Delile) is very abundant on all marine structures. Though the detrimental effect of this macro algae Ulva fasciata is a secondary one, its effect has to ascertain. To know its effect, the basic mechanism by which Ulva fasciata deteriorates concrete structures, M20 grade concrete cubes were casted and kept in the coastal area where there is abundant growth of Ulva fasciata and also laboratory simulation has been carried out. To ascertain the detrimental effect by the macro algae on concrete surface, samples were collected from the concrete cubes kept in the coastal area and also from the laboratory simulated one. The collected samples were analyzed by SEM, EDX and XRD to establish the degree of deterioration done by marine algae on concrete surface. The SEM and EDX results showed that there is a remarkable change in the base materials viz., Ca and Si content and XRD results revealed the absence of Calcium Hydroxide. Both the results confirmed the biodeterioration of concrete by the marine green algae.