Repair of degraded structural members with substantial corrosion damage is a critical aspect of structural integrity management of both offshore and onshore oil and gas structures. Conventional cutting and welding repairs of damaged/corroded structural members are generally the standard. However, such a repair is considered a hot work repair, which requires the subject tank/location and adjacent tanks gas free for safety reasons. This leads to a significant impact on the continuous operation of the units and, consequentially, financial losses.

The main advantage of this technique is that it does not require cutting or welding, allowing for continuous operation of the structure with no safety risks. The repair method utilizes a new steel plate bonded to the existing damaged/corroded steel plate by specially selected adhesive polymer(s), forming a sandwich composite plate. The repair can be done from one side of the structure only, making it significantly simpler and faster than other alternatives.

Traditionally, the impact requirements set out by MARPOL for FPSOs and FSOs have been addressed by creating internal cofferdams or external sponsons.

This research paper describes the structural engineering study conducted to confirm the impact resistance of an SPS 20-30-Existing CDH for the prescribed impact between an offshore supply vessel and the FPSO in way of the boat landing area. Based on the results from the structural dynamic analysis using LS-DYNA, which simulated bow and stern collisions for various collision angle and locations, two main conclusions were drawn:

Firstly, it was observed that the SPS 20-30-Existing CDH provides an impact resistant hull structure able to withstand the minimum accepted industry standard specified design condition (5000 tonnes displacement OSV colliding with the specified FPSO at 2m/s) without rupture of the crude oil tanks. As an integral part of the FPSO structure, it not only meets but exceeds the requirements of MEPC/Circ 406 “Guidelines for Application of MARPOL Annex I Requirements to FPSOs and FSUs”, providing 97,000 kJ of energy absorption capacity.

Secondly, SPS CDH provides a package of risk reduction benefits over that of cofferdams and external that reduces critical fatigue stresses, schedule reduction for fabrication and installation, reduced risks during fabrication, less maintenance and eliminates the risks and costs for through life void space inspections.

Furthermore, case studies describe the conversion cost, schedule benefits and operational benefits of the SPS CDH as installed on projects completed to date, including the FPSO’s P57, P58, MV22 and Aseng. Project approvals have been granted by DNV and ABS.

This research paper, a collaboration between SPS Technology (previously Intelligent Engineering), DNV, Technip and Sabah Shell Petroleum, describes an application of SPS technology as an impact protection deck for the well bay deck area of a Tension Leg Platform (TLP) structure.

The authors first described the main features of the system, design parameters, deck panel geometry and impact protection design philosophy. The impact resistant panels incorporated two key design features: a puncture and impact resistant plating with excellent membrane capacity, and a channel support frame designed to provide a controlled progressive collapse mechanism for impact loads, and a soft support at the corners of the panels/panel junctions while maintaining the structural capacity for operational loads.

Then, finite element analyses using two commercially available explicit finite element codes (LS-DYNA and Abaqus) were used to simulate the structural response and energy dissipation mechanisms related to accidental impact loads with rigid and deformable objects.

This research paper undertaken at Virginia Tech and  Michigan Tech presents the results of a live-load test of the Shenley Bridge, the first bridge application of the sandwich plate system technology in North America. The Shenley Bridge was built in 2003, in Québec, Canada, it spans 23m, has a width of 7m and was designed according to the Canadian Highway Bridge Design Code (CHBDC).

Distribution factors were determined for interior and exterior girders and dynamic load allowance was determined from a comparison of the bridge’s response under static conditions to the response under dynamic conditions. A comparison between measured results and AASHTO LRFD, AASHTO standard, and CHBDC provisions for concrete decks supported by steel girders indicated that the standard provisions tend to produce conservative predictions for lateral load distribution but can be unconservative for dynamic load allowance in some cases. As a result of the testing program containing a single field test, a finite-element model was also used for determination of lateral load distribution and yielded predictions similar to the measured results. Results from the finite-element models were often less conservative than the code provisions.

This independent group of researchers performed and assessed full-scale laboratory fatigue tests on two retrofitted steel orthotropic bridge decks (OBDs). The aim of the tests was to reduce stresses at fatigue-sensitive details and, therefore, extend the fatigue life of the OBD by stiffening the existing deck plate. Two retrofitting systems were studied for this research paper. The first is the bonded system, which consists of bonding a second steel plate to the existing deck by vacuum-infusing a thin adhesive layer (2 mm) between the two steel plates.

Both retrofitting systems were found to be very efficient in reducing stresses (between 45 and 70% reduction), with the bonded system being more efficient in reducing local stresses close to the welds and the sandwich system in reducing global stresses on the bridge. Moreover, stresses are lower than their fatigue threshold even under maximum wheel loads. Results proved that both systems are efficient alternatives to retrofit and help extend the fatigue life of the existing OBD.

This paper describes the design, fabrication and erection of an SPS bridge deck integrated with press-braked tub girders Muskingum County, Ohio.

The design of both SPS bridges was driven by accelerated bridge schedules to minimize impact to the travelling public, residents and the environment.

This research paper from 2021 by an independent Indian research team presents the behaviour of isotropic bridge decks and orthotropic sandwich bridge decks under IRC class-A wheel loading. In general, fatigue damage on the bridge deck is caused by stress concentration due to wheel loads.  Therefore, reducing the stress range in critical locations will extend the fatigue life of the structure. In this context, the authors performed a finite element analysis of the SPS bridge deck experiment conducted by Shan and Yi (2016), which compared 2-10-2 SPS and 4mm single-layer steel plate decks under wheel loads. Authors observed a good match between experimental and simulation results using ANSYS.

In summary, the authors of this research paper showed that SPS can:

• significantly reduce fatigue damage,
• has a great overall structural performance, and
• is an effective solution to retrofit existing steel (orthotropic) bridge decks.

This research paper by an independent research team at South China University of Technology presents the results of laboratory experimental and numerical studies of wheel load stress concentrations on SPS bridge deck panels with no stiffeners compared with those for a stiffened steel deck.

This paper provides details of the key structural (serviceability and ultimate limit state loads) and dynamic (natural frequencies, damping, mode shapes, modal mass and acceleration response to walking excitations) testing (BRE Global, UK and University of Sheffield Vibration Engineering Section) and subsequent approvals for SPS floors and terraces.

This research paper presents a study by a joint US and Korean research group.  Experiments with various independent variables were performed to evaluate the flexural capacity of the composite panel, and finite element analyses were conducted to examine the state of the stresses generated between the steel plate and the polymeric core. Twelve panels measuring 500mm x 250mm were assessed.

Results also confirmed that the bond strength between the polymeric material and the steel plates was sufficient to maintain the stability of the panels and to resist the forces generated at the interface between the two materials, even without any special surface treatment or additional shear connectors. Design equations for predicting the flexural strength and stiffness of the panels were proposed, and its suitability was verified. Additionally, experimentally tested cutting and joining recommendations for field applications were presented.

This paper by Korean researchers assesses the dynamic properties and vibration characteristics of the sandwich plate system used as floor panels. An experiment was performed in two buildings where the system was applied: a large 15m module in a new building and a 1.5m² renovation module, suitable to be lifted by a single person.

Authors also emphasize that besides the adequate vibration performance, the system also has numerous other advantages, such as being able to decrease the construction duration, floor height, and structural weight.

This research paper covers Sandwich Plate System as a structural composite material and two types of applications in bridge rehabilitations: full deck replacement and deck overlay. Highlighting two projects — Mettlach Bridge in Germany, and the Pont Grande-Duchesse Charlotte (Pont Rouge) in Luxembourg — the authors illustrate the efficiency and applicability of SPS.

In this paper, SPS Technology engineer Rodrigo Gorga and the team of authors proposed a simple yet reliable macro-scale ASR finite element (FE) approach for use in more accurate modelling of the combined effect of corrosion and ASR.