Composite Footbridge Research Articles

A full computational framework for the temperature analysis of a flax-reinforced composite footbridge with field monitoring validation

This research presents a computational framework for predicting temperatures in flax-reinforced composite sandwich footbridges. The case study is a 15m-span footbridge situated in Almere, the Netherlands, instrumented with 82 fiber Bragg grating (FBG) sensors and 8 thermocouples within an IoT-based structural health monitoring (SHM) system, enabling real-time evaluation. The main focus of this article is to enhance the understanding of structural temperature distributions in FRP sandwich cross-sections for bridge engineering applications. Furthermore, providing a comprehensive and accurate framework for temperature normalization of FBG strain measurements. The methodology involves environmental data, point-by-point solar radiation analysis with sun sheltering, and thermal properties characterization, culminating in a numerical analysis using Abaqus. A k-d tree binary search is performed previous to the numerical analysis to solve compatibility between Abaqus and Rhino's meshing algorithms. The non-uniform heat flux is used as input for the numerical analysis and handled through UEXTERNALDB and DFLUX subroutines. The use of a sub-modeling technique, allows the isolation, in correspondence of the sensor locations, of one critical section of the bridge for detailed analysis. Verification against in-situ measurements demonstrates the framework's efficacy. It was concluded that the framework restitutes errors in the range of ±1 ÷ 3 °C across varying weather conditions, during different seasons, and consistently for multiple sensor locations. Finally, the results are used to compensate strain measurements of nearby selected FBG sensors from the temperature counterparts.

Vertical human-structure interaction of a simply-supported steel-glass composite footbridge under both standing and moving pedestrians

For lightweight footbridges, there are evident vertical coupling effects among standing pedestrians, moving pedestrians and the footbridge. To further clarify the vertical human-structure interaction, the effects of a single standing pedestrian, a single moving pedestrian, as well as both a single standing pedestrian and a single moving pedestrian on a simply supported steel-glass composite footbridge model are investigated in this study, respectively. Experimental results show that the effects of standing and moving pedestrians on the structural natural frequencies are different. The Fourier spectrum of the footbridge is sensitive to the relationship between the natural frequency of the coupled system and the walking frequency of the moving pedestrian. Moreover, at the same monitoring point, the vertical velocity of the footbridge is significantly less than that of the centroid of the standing pedestrian. Finally, a corresponding theoretical model is presented in this study. It is found that the theoretical model can well predict vertical dynamic responses of the human-structure coupled system, and the relative relationship of the vertical dynamic response between the footbridge and the standing pedestrian is clarified. This study can provide valuable references for vertical human-structure interaction and vibration serviceability assessment of the footbridge.

Life Cycle Sustainability Assessments of an Innovative FRP Composite Footbridge

Sustainable construction and the design of low-carbon structures is a major concern for the UK construction industry. FRP composite materials are seen as a suitable alternative to traditional construction materials due to their high strength and light weight. Network Rail has developed a prototype for a new innovative footbridge made entirely from FRP with the aim of replacing the current steel design for footbridges. This study conducted a life cycle analysis of this novel composite footbridge design to quantify the cost and environmental benefits. An LCA and LCC analysis framework was used to analyse the environmental impacts and cost savings of the bridge throughout its lifespan from raw material extraction to its end of life. From the results of the LCA and LCC, the FRP footbridge sustainability was reviewed and compared to a standard steel footbridge. Due to the uncertainty of the fibre-reinforced plastic (FRP) structure’s lifespan, multiple scenarios for longevity at the assets-use stage were studied. The study revealed that the FRP bridge offered substantial economic savings whilst presenting potentially worse environmental impacts, mainly caused by the impact of the production of FRP materials. However, our study also demonstrated the influences of uncertainties related to the glass-fibre-reinforced plastic (GFRP) material design life and end-of-life disposal on the whole life cycle analyses. The results show that if the FRP footbridge surpasses its original estimation for lifespan, the economic savings can be increased and the environmental impacts can be reduced substantially.

Multiparameter sensitivity analysis of a GFRP composite footbridge of a sandwich structure and U-shaped cross-section

The paper deals with multiparameter sensitivity analysis of a composite footbridge. A shell-like structure is 14.5 m long shows U-shaped cross-section and inner service dimensions 1.3 × 2.5 m. Glass fiber reinforced polymer GFRP laminate constitutes faces of a sandwich structure while PET foam received from recycled bottle builts a core. The structure was divided into 285 independent areas where the thickness of laminates and stiffness modulus of PET foam were established as design variables. The impact of their variation on variation of state variables was investigated, vertical displacement of structure, longitudinal strain in handrail and transverse strain in deck were addressed here. Sensitivity vector was computed by a semi-analytical method and, subsequently, expressed in a matrix form and next presented graphically in the form of sensitivity areas. The conducted sensitivity analysis exhibits areas that can be strengthened in order to minimize vertical displacement, longitudinal strain in handrail and transverse strain deck, determining the areas where parameters can be reduced without increasing the value of state variables. The obtained results are bound to support the structural design process or to improve the performance of existing structures.

GFRP composite footbridge series with multi-box cross section – Part 2: Local detailed design

The contribution constitutes Part 2 of research on a GFRP composite footbridge series with a multi-box cross section (Composite Structures, 2020). The 3D numerical modelling and simulation methodology was elaborated and experimentally validated on a test system in which glued laminates, rubber pads, steel plates and screw joints are applied. The test system reflects a steel post–composite platform joint applied in the footbridge series. Local detailed design calculations were carried out including the parts/joints of the case study footbridge that were omitted or modelled in a simplified manner in the global detailed design calculations in Part 1, i.e. validating the ultimate limit state (ULS) for the rubber bearings, validating the ULS for the support stabilizing systems, validating the ULS for the steel post–composite platform joints, validating the ULS for the transport-and-assembly openings. The simulation results were presented in the form of displacement contour maps, failure index contour maps and effective stress contour maps. The parts/joints in which stress concentrations appear were redesigned accordingly to meet the load capacity conditions. The elaborated methodology ensures that the local design results are applied to the entire footbridge series.

Validation Process for Computational Model of Full-Scale Segment for Design of Composite Footbridge

Abstract Experimental tests and numerical simulations of a full-scale segment of a foot and cycle bridge made of polymer composites are presented in the paper. The analysed structure is made of sandwich panels, which consist of glass fibre reinforced polymer (GFRP) multi-layered laminate faces and a PET foam (obtained from recycling) core. The dimensions of the segment cross-section are the same as for the target footbridge; however, span length was reduced to 3 m. The experimental tests were conducted in a laboratory of the Faculty of Ocean Engineering and Ship Technology at Gdansk University of Technology. A single vertical force was generated by a hydraulic cylinder and was applied to the platform of the structure. The experimental tests were supported by numerical analyses performed in Femap with NX Nastran software by means of the finite element method (FEM). Results obtained in the computational model were compared with results from experiments. Thus, the numerical model was validated and the obtained conclusions were used in the next step of the design process of a composite footbridge with a span length of 14.5 m.

Parametric optimization of sandwich composite footbridge with U-shaped cross-section

Parametric optimization of sandwich composite footbridge was presented in the paper. Composite footbridge has 14,5 m long and has U-shaped cross-section with inner dimensions 2,6 × 1,3 m. The sandwich structure in made from GFRP laminate as a faces and PET foam as a core. The aim of analysis was to minimize the mass of the new footbridge that can lead to minimize the cost of structure. After optimization was conducted, the new structure was compare with the realized one. The results show that while mass can be decreased the state variables of structure like maximum displacement, strain or natural frequency do not change significantly. Moreover, results show that, although the mass is decreased, stiffness of the new structure is even higher.Optimization and sensitivity analysis, the divisions of theory of designing, provide the designer a significant support. Despite presented optimization, also sensitivity analysis can additionally be effectively used in issues related to strengthening or modernizing structures as well as in the process of identifying quantities describing the computational model.

GFRP composite footbridge series with multi-box cross section – Part 1: Design methodology, conceptual design and global detailed design

An original conceptual structural and technological design of a series of GFRP composite footbridges was developed, with a multi-box cross-section. A methodology for the design of these footbridges was elaborated using the appropriate Eurocodes and the design code developed by the European Structural Polymeric Composites Group. A method for computer-aided design calculations of the footbridge series using MSC.Marc FE code was formulated. The criteria for the preliminary design and the global detailed design of FRP composite footbridges were established. The structural design of a pedestrian-and-cyclist GFRP composite bridge with a 16.00 m span length and 2.56 m usable width (study case) was created, belonging to the above-mentioned series. Global detailed calculations were carried out as part of the design of the case study footbridge. Seven ultimate limit states and two serviceability limit states were taken into account, and the relevant simulation results were presented. The dimensions of the case study footbridge adopted on the basis of the preliminary design lead to fulfilment of the load-bearing and service conditions in the global detailed calculations. The GFRP composite footbridge series appears to be competitive in terms of technology and price in comparison with existing FRP composite footbridges.

Short and Long Term Measurements in Assessment of FRP Composite Footbridge Behavior.

The paper presents application of different sensors for the purpose of short and long term measurements, as well as a structural health monitoring (SHM) system to assess the behavior of a novel fiber reinforced plastics (FRP) composite footbridge. The aim is to present a thorough and concise description of these sensors networks and results gathered with their aid during in situ measurement of strains, displacements, and vibrations, as only a few works are available in this field. The bridge geometry, material solutions, and properties are described at first. Then the measurement devices composing the system and subsystems of sensors are elaborated on. Subsequently, the bridge research program is described and the results are shown and discussed. Finally, it is concluded that the use of selected sensors is helpful in assessment of the behavior of the novel structure, and moreover in validation of its numerical models. The collected data confirmed many assumptions made during the bridge design process and allowed us to accept it for exploitation.

Bio-based composite footbridge: Design, production and in situ monitoring

This paper deals with the design, production and monitoring of a bio-composite footbridge with a span of 14 meters across the river Dommel in the city of Eindhoven, the Netherlands. The specific bio-composite material that was used for this research is a Natural-Fibre Reinforced Bio-Polymer (NFRBP). The goal of the research is to prove that NFRBP can be applied as a load bearing structure in an outdoor environment. For this purpose, a multidisciplinary team of academic researchers from two universities, together with a manufacturer from the NFRBP industry and the Centre of Expertise Biobased Economy (CoEBBE), developed a feasible design that could be produced by unskilled hands in a short period of time and within a limited budget. The footbridge was designed, built and installed within less than one year. In the two years after the installation of the footbridge, the structural behaviour of the bridge was monitored by means of optical fibre glass strands, integrated within the structure, with the purpose of measuring deformations and change in elasticity that occur over time.

Numerical modeling and experimental validation of full-scale segment to support design of novel GFRP footbridge

The paper contains analysis of full-scaled three meters long segment of a novel composite footbridge. Both numerical modeling and experimental validation were performed. Analyzed object is a shell type sandwich channel-like structure made of composite sandwich with GFRP laminates as a skin and PET foam as a core. Several static load schemes were performed including vertical and horizontal forces. In FEM analysis multilayered laminate was modeled by means of Equivalent Single Layer (ESL) method while the foam was assumed as three-dimensional continuum. Results were compared with the ones obtained from experiments. Good agreement in comparison showed the correctness of conducted assumption what was a great support in designing process of fourteen-and-half meters long footbridge.

Dynamic tests of composite footbridge segment – experimental and numerical studies

Experimental dynamic tests and numerical simulations of a 3 meters long segment of a footbridge made of polymer composites are presented in the paper. The span-length is reduced, however dimensions of cross-section are the same as the target footbridge. The segment structure is made of sandwich panels, which consist of fibre reinforced polymer (GFRP) laminates (skins) and a PET foam (core). The first part of the paper contains description and results of experimental dynamic tests, which were subjected to the structure. The excitations during these tests was realised by a group of people standing or jumping on the structure deck. The obtained results allowed to determine natural frequencies as well as damping ratios. Moreover, cyclic loading was applied to the structure deck to check the possibility of delamination or debonding occurrence, as a result of repetitive dynamic excitations. The second part contains validation of numerical model - results of numerical analysis and its comparison with the experimental ones.

Bio-based composite footbridge

This paper deals with the design, production and monitoring of a bio-composite footbridge with a span of 14 meters across the river Dommel in the city of Eindhoven, the Netherlands. The specific bio-composite material that was used for this research is a Natural-Fibre Reinforced Bio-Polymer (NFRBP). The goal of the research is to prove that NFRBP can be applied as a load bearing structure in an outdoor environment. For this purpose, a multidisciplinary team of academic researchers from two universities, together with a manufacturer from the NFRBP industry and the Centre of Expertise Biobased Economy (CoEBBE), developed a feasible design that could be produced by unskilled hands in a short period of time and within a limited budget. The footbridge was designed, built and installed within less than one year. In the two years after the installation of the footbridge, the structural behaviour of the bridge was monitored by means of optical fibre glass strands, integrated within the structure, with the purpose of measuring deformations and change in elasticity that occur over time.

Delivery of a 40 m long fibre-reinforced polymer composite footbridge in Madrid, Spain

This paper describes the design, manufacture, installation and load testing of a 40 m long urban footbridge over the River Manzanares in Madrid, Spain. The main structure of the footbridge consists of a fibre-reinforced polymer girder. The girder was manufactured in a workshop using the resin-infusion process, which is normally used to manufacture fibreglass boat hulls. Potential problems that can arise in the manufacture of such elements are highlighted in the paper and the strategies adopted to cope with them are illustrated. The girder was transported by truck to the site where it was lifted onto reinforced concrete supports. The results of the static and dynamic load tests carried out after completion of the pedestrian bridge are presented.

Numerical and experimental assessment of a typical brazilian footbridge

Abstract For the range of medium spans, around 30 to 40m, composite footbridges are getting popular in Brazil. This kind of structure consists on longitudinal steel truss beams providing support for a concrete deck usually made of precast elements. Typical examples of these structures may be found in many cities in Brazil, especially in Brasilia where a large number of highways demanded a significant set of footbridges. Due to the amount of this kind of composite footbridges in Brazil, studies concerning their mechanical behavior are required in order to ensure pedestrian’s safety. For this end, in this paper, a typical Brazilian composite footbridge located in Brasilia is analyzed by means of experimental tests and computational modeling. The focus is the determination of natural frequencies and mode shapes. Strategies to correctly obtain the vertical modes are also discussed since vertical vibration is the main vibration problem expected for the tested footbridge. The obtained results showed that structural balance between stiffness and mass leads to natural frequencies out of the critical frequency range excited by pedestrians in normal use, although the idea was not to measure how these parameters, mass or stiffness, could influence the model. Moreover, Finite Element models were evaluated comparing complexity versus accuracy to predict modal parameters.

Modal properties identification of a novel sandwich footbridge – Comparison of measured dynamic response and FEA

Abstract A modern sandwich composite footbridge made of high-tech materials, being an example of practical application of laminated composites in civil engineering, is presented. The in situ non-destructive testing of the footbridge, aiming to identify modal properties and pedestrian comfort, is described. The measured eigenmodes and eigenfrequencies are compared with numerically estimated values. Finite element analyses of the footbridge are performed with aid of pure equivalent single layer shell and shell-solid models using Abaqus 6.14 environment. Application of the models is assessed basing on the obtained results in the field of footbridge dynamic response description capabilities.

Proposal of the Composite Footbridge for the Military Application

Proposal of the Composite Footbridge for the Military Application

The relationship between pedestrian loading and dynamic response of an FRP composite footbridge

The relationship between pedestrian loading and dynamic response of an FRP composite footbridge

Load Testing of GFRP Composite U-Shape Footbridge

The paper presents the scope of load tests carried out on an innovative shell composite footbridge. The tested footbridge was manufactured in one production cycle and has no components made from materials other than GFRP laminates and PET foam. The load tests, performed on a 14-m long structure, were the final stage of a research program in the Fobridge project carried out in cooperation with: Gdańsk University of Technology (leader), Military University of Technology in Warsaw, and ROMA Co. Ltd.; and co-financed by NCBR. The aim of the tests was to confirm whether the complex U-shape sandwich structure behaves correctly. The design and technological processes involved in constructing this innovative footbridge required the solving of many problems: absence of standards for design of composite footbridges, lack of standardized material data, lack of guidelines for calculation and evaluation of material strength, and no guidelines for infusion of large, thick sandwich elements. Obtaining answers during the design process demanded extensive experimental tests, development of material models, validation of models, updating parameters and extensive numerical parametric studies. The technological aspects of infusion were tested in numerous trials involving the selection of material parameters and control of the infusion parameters. All scientific validation tests were successfully completed and market assessment showed that the proposed product has potential applications; it can be used for overcoming obstacles in rural areas and cities, as well as in regions affected by natural disasters. Load testing included static and dynamic tests. During the former, the span was examined at 117 independent measurement points. The footbridge was loaded with concrete slabs in different configurations. Their total weight ranged from 140 kN up to 202 kN. The applied load at the most heavily loaded structural points caused an effect from 89% to 120%, compared to the load specified by standards (5 kN/m2). Dynamic tests included standard actions (walking, running, synchronous jumps) as well as aggressive tests, all designed to confirm the usability of the footbridge. The performed trials allowed the identification of the modal and damping parameters of the structure. The designated first natural frequency with a value of 7.8 Hz confirmed the correctness of the U-shape cross-section design due to its significant structural rigidity.

A novel sandwich footbridge - Practical application of laminated composites in bridge design and in situ measurements of static response

A novel sandwich composite footbridge is presented in the paper, as an example of practical application of laminated composites in civil engineering. The in situ static load tests of the footbridge before its acceptation for exploitation are shown and discussed. The results are compared with the corresponding ones from a numerical equivalent single layer model of the sandwich structure created within the framework of finite element method. The numerical solutions, are slightly higher than the measured in situ ones. Hence, it is concluded that the chosen method of structural analysis is efficient enough to recreate static behavior of the bridge and thus it is accepted for application in civil engineering.