Feasibility Study: FRP Jetties

Abstract

Fiber-reinforcedplastic (FRP) is an upcoming material in the construction industry due tocharacteristic material properties such as its high resistance to corrosion andhigh strength to density ratio. Also, it is often claimed that structures fromFRP have lower life-cycle costs and eco burden compared to constructions madefrom steel, concrete, or wood; this can be attributed to the low amount ofrequired maintenance and longer life span of FRP. Therefore, FRP seems a verysuitable material in the harsh environments where hydraulic structures residecompared to conventional materials.No actual commercial jetties, besidessmall pedestrian jetties, are yet constructed from FRP: knowledge regarding thepotential financial savings or the environmental impact of such jetties are notwell known. Also, specific consequences of constructing a jetty from FRP areunknown, as well the ability of FRP jetties to maintain their structuralcapabilities over their entire life-time. Therefore, this thesis investigatesthe feasibility of FRP jetties and judges whether FRP jetties are betteralternatives than jetties constructed fromtraditional materials. In the scope of this thesis, the research is narrowed down to comparing FRP withreinforce concrete (RC).The main design challenge of FRP incivil engineering related structures is coping with the relatively lowstiffness of FRP, as this presumably determines the dimensions of thestructural elements and restrictions of the structure as a whole. Governingstructural safety criteria in steel and concrete are more often strengthrelated. The research rests on a case study of an RC jetty, which provides boundaryconditions and a program of requirements. An FRP jetty is designed whichcomplies with the structural criteria. These criteria were both extracted fromthe case study and provided by the CUR96, a Dutch design guideline for FRP incivil engineering practice. Most structural elements are designed from scratch:laminates are designed for the flanges and webs in a composite calculator namedeLamX2. The finite element method (FEM) software program SCIA Engineer is usedfor the structural analysis. One dimensional structural elements were firstvalidated before utilizing them in the FEM model. The pile properties anddimensions are based on contemporary literature and commercially availableproducts. The driveability of the FRP piles is researched by means of Wave EquationAnalysis of Piles (WEAP), for which the program AllwavePDP is utilized.Furthermore, sustainability aspects of both jetties are researched by means ofa Life Cycle Assessment (LCA). The LCA determines how much equivalentgreenhouse gases are expelled over the life-time of the jetties for a set ofimpact categories. These results are normalized by calculating the respectiveshadow costs for each impact category; this makes the total environmentalimpact of the structures comparable. The financial feasibility is the lastinvestigated topic; under various scenarios, life-cycle costs of both jettiesare investigated. The scenarios contained different variables such as estimatesof FRP raw material costs or assumed share of maintenance costs; end-of-lifecosts were not included in the analysis.The structural analysis of the FRPjetty indicated that both Serviceability Limit State (SLS) criteria and UltimateLimit State criteria (ULS) determine the dimensions of the structural elementsand the jetty design in general. The most crucial parts are partially embeddedFRP piles, which are prone to buckling. Initially, the FRP piles in thedetailed 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 duringinstallation before reaching this level. An analysis indicated that drivingshorter piles to a depth of 8 meter is possible: at this depth, the piles donot refuse and have accumulated sufficient bearing capacity by shaft frictionto support the superstructure. The eco burden of the FRP jetty was foundsignificantly higher compared to the RC jetty: in the base case LCA, therelative difference is 365 percent higher for the FRP variant. After asensitivity analysis, the relative difference is still 59 percent higher when comparingthe best-case scenario of the FRP jetty with the worst-case scenario of the RCjetty. The RC jetty also performed better than the FRP jetty regardinglife-cycle costs in various considered scenarios. The relative difference inlife-cycle costs for the most favorable scenario of the FRP jetty is still 28 %higher compared to the life-cycle costs of the RC jetty.Due to the poorer performance of theFRP jetty regarding the life-cycle costs and environmental burden, it isconcluded that FRP jetties, for the time being, are not better alternativesthan RC jetties. Regarding the type of jetty, the conclusion can begeneralized. The jetty is designed for the turnover of liquid bulk; imposed loadsare 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 forthose cases. Regarding the material choice, the conclusion cannot begeneralized. The FRP jetty was compared to an RC jetty. Jetties made from steelor wood are likely more vulnerable to degradation in harsh conditions. Thedurability properties of FRP might be more beneficial to the assessment of FRP jettiesin these cases. Certain future developments might affect the conclusion.Innovation in manufacturing techniques and an increase of market demand for FRPcould lower the price. Besides, biodegradable FRP materials are being developedwhich potentially may reduce the environmental burden of FRP. Keywords: FRP, composite design,hydraulic structures, jetty, pile driving, LCA, life-cycle costs