Graduation of Roel Winter
28 September 2017 12:00 - Location: Room 1.96, faculty of Civil Engineering and Geosciences
“Feasibility Study: Investigating the Technical- and Economic Feasibility and Sustainability Aspects of Fiber-reinforced Plastic Jetties”| Professor of graduation: Prof. dr. ir. S.N. Jonkman , supervisors: Dr. ir. J.G. de Gijt (TU Delft), Dr. H.M. Jonkers (TU Delft), Dr. ir. C. Kassapoglou (TU Delft), Ir. H.E. Pacejka (Gemeente Rotterdam)
Fiber-reinforced plastic (FRP) is an upcoming material in the construction industry due to characteristic material properties such as its high resistance to corrosion and high strength to density ratio. Also, it is often claimed that structures from FRP have lower life-cycle costs and eco burden compared to constructions made from steel, concrete, or wood; this can be attributed to the low amount of required maintenance and longer life time of FRP. Therefore, FRP seems a very suitable material in the harsh environments where hydraulic structures reside compared to conventional materials.
No actual commercial jetties, besides small pedestrian jetties, are constructed from FRP: knowledge regarding the potential financial savings or the environmental impact of such jetties are not well known. Also, specific consequences of constructing a jetty from FRP are unknown, as well the ability of FRP jetties to maintain their structural capabilities over their entire life-time. Therefore, this thesis investigates the feasibility of FRP jetties and judges whether FRP jetties are better alternatives than jetties constructed from traditional materials. In the scope of this thesis, the research is narrowed down to comparing FRP with reinforce concrete (RC).
The main design challenge of FRP in civil engineering related structures is coping with the relatively low stiffness of FRP, as this presumably determines the dimensions of the structural elements and restrictions of the structure as a whole. Governing structural safety criteria in steel and concrete are more often strength related.
The research rests on a case study of an RC jetty, which provides boundary conditions and a program of requirements. An FRP jetty is designed which complies with the structural criteria. These criteria were both extracted from the case study and provided by the CUR96, a Dutch design guideline for FRP in civil engineering practice. Most structural elements are designed from scratch: laminates are designed for the flanges and webs in a composite calculator named eLamX 2. The finite element (FEM) software program SCIA Engineer is used for the structural analysis. One dimensional structural elements were first validated before utilizing them in the FEM model. The pile properties and dimensions are based on contemporary literature and commercially available products. The driveability of the FRP piles is researched by means of Wave Equation Analysis of Piles (WEAP), for which the program AllwavePDP is utilized. Furthermore, sustainability aspects of both jetties are researched by means of a Life Cycle Assessment (LCA). The LCA determines how much equivalent greenhouse gasses are expelled over the life-time of the jetties for a set of impact categories. These results are normalized by calculating the respective shadow costs for each impact category; this makes the total environmental impact of the structures comparable. The financial feasibility is the last investigated topic; under various scenarios, life-cycle costs of both jetties are investigated. The scenarios contained different variables such as estimates of FRP raw material costs or assumed share of maintenance costs.
The structural analysis of the FRP jetty indicated that Serviceability Limit State (SLS) criteria are most often the governing criteria and determine the dimensions of the structural elements (i.e. planks, beams, and girders).
Initially, the FRP piles in the detailed design were to be installed to a depth of 13 meter below ground level, but the results from the WEAP indicated that the piles refused during installation before reaching this level. An analysis indicated that driving shorter piles to a depth of 8 meter seems to be possible: at this depth, the piles do not refuse but do have accumulated sufficient bearing capacity by shaft friction to support the superstructure. The eco burden of the FRP jetty was found significantly higher compared to the RC jetty: in the base case LCA, the relative difference is 270 percent higher for the FRP variant. After a sensitivity analysis, the relative difference is still 25 percent higher when comparing the best-case scenario of the FRP jetty with the worst-case scenario of the RC jetty. The RC jetty also performed better than the FRP jetty regarding life-cycle costs in all the considered scenarios. The relative difference in life-cycle costs for the most favorable scenario of the FRP jetty is still 125 % higher compared to the life-cycle costs of the RC jetty.
Due to the poorer performance of the FRP jetty regarding the life-cycle costs and environmental burden, it is concluded that FRP jetties, for the time being, are not better alternatives than RC jetties. Regarding the type of jetty, the conclusion can be generalized. The jetty is designed for the turnover of liquid bulk; imposed loads are generally lower than loads on Ro-Ro, solid bulk, or container transfer jetties. It therefore seems unlikely that FRP does seem to be a better alternative for those cases. Regarding the material choice, the conclusion cannot be generalized. The FRP jetty was compared to an RC jetty. Jetties made from steel or wood are likely more vulnerable to degradation in harsh conditions. The durability properties of FRP might be more beneficial to the assessment of FRP jetties in these cases.
Certain future developments might affect the conclusion. Manufacturing techniques for FRP are optimized and hence costs are reduced. Besides, biodegradable FRP materials are being developed which potentially may reduce the environmental burden of FRP. Also, the price developments of related raw materials (e.g. oil, concrete, steel) and smart solutions for the end-of-life stage might significantly influence the life-cycle costs of the jetties in both ways.
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