Experimental and Numerical Investigation on Dynamic Properties and Human-Induced Vibrations of an Asymmetric Steel-Plated Stress-Ribbon Footbridge

This paper presents a comprehensive study on dynamic properties and human-induced vibrations of a slender asymmetric steel-plated stress-ribbon footbridge via both experimental and analytical methods. Bridge modal test was conducted using both ambient vibration testing and impact methods. Modal properties of the bridge were identified based on stochastic subspace identification and peak-pick techniques. Results show that the bridge is characterized by closely spaced modes with low natural frequencies and small damping ratios (<0.002). A sophisticated finite element model that incorporates pretension of the stress ribbon and contribution of deck panels is developed and proven to be capable of reflecting the main dynamic characteristics of the bridge. Human-induced vibrations were measured considering synchronization cases, including single-person and small group walking as well as random walking cases. A theoretical model that takes into account human-structure interaction was developed, treating the single walking person as an SDOF system with biomechanical excited force. The validity of the model was further verified by measurement results.

Development and study of closure strip between precast deck panels in accelerated bridge construction

This research investigates the use of glass fiber reinforced polymer (GFRP) bars in bridge decks and ultra-high performance fibre-reinforced concrete (UHPFRC) as filling materials in (i) panelto- panel closure strips between transverse precast full-depth deck panels (FDDPs) supported over girders and (ii) the shear pockets for the panel-to-girder connection. The experimental research program included three phases. Phase I examined pullout strength of straight-end and headed-end GFRP bars embedded into UHPFRC to determine the required closure strip width to develop bar full strength. Phase II included the development and study of closure strip details incorporating UHPFRC as joint-filling materials and GFRP bars projecting into the joint. Three joints of width 200 mm between precast FDDPs were developed, namely: angle-shape joint (Ajoint), C-shape joint (C-shape), and zigzag-shape joint (Z-joint), with 175-mm projecting length of GFRP bars into the joint. Two series of 2500x600x200 mm one-way slabs were cast to investigate the flexural strength of the jointed precast slabs compared to cast-in-place slabs. Two types of concrete were used to fabricate the precast FDDPs, namely: normal concrete (NSC) and high-performance concrete (HPC). Correlation between experimental results and available design equations for moment and shear capacities, as well as CHBDC and AASHTO-LR applied factored design moments, was performed. All specimens failed in either flexural or flexural-shear mode outside the UHPFRC-filled joint. Phase III included testing three pairs of 3700x2500x200 mm laterally-restrained precast FDDPs incorporating the three developed joint details in the transverse direction of the girders. Each pair of specimens was tested under 600x250 mm wheel loading located beside the closure strip, considering (i) constant amplitude fatigue (CAF) loading up to 4 million cycles followed by increasing static loading to-collapse, and (ii) incremental variable amplitude fatigue (VAF) loading to-collapse. The failure mode of the tested slabs was punching shear, with the transverse UHPFRC joint diverting the extension of the punching shear plane to the adjacent precast FDDP segment. Results of fatigue load tests on the three-jointed pairs of slabs showed high fatigue performance. A new prediction model for fatigue life of the GFRP-reinforced, UHPFRC-filled jointed deck slabs was developed.

Flexure strength prediction of closure strip between prefabricated deck slabs supported over bridge girders incorporating CFRP bars and UHPFRC

Glass fiber reinforced polymer (GFRP) bars are used in bridge decks to overcome the problem of corrosion of steel bars and concrete spalling. However, design guidelines for joints between GFRPreinforced precast deck panels supported over girders for accelerated bridge replacement is as yet unavailable. The proposed research investigates the use of GFRP bars in the closure strip between jointed precast deck panels, which is filled with ultra-high performance fiber-reinforced concrete (UHPFRC). Four different bar splice lengths in the joint were considered in this study, namely: 75, 105, 135 and 165 mm, with bar splice spacing taken as 0, 75 and 100 mm. 27 specimens were constructed and tested to-collapse to determine their structural behavior and load carrying capacity. Correlation between experimental findings and available design equations for moment and shear capacities was conducted, leading to recommendations for the use of the proposed joints between precast deck panels in slab-on-girder bridges.

Flexure strength prediction of closure strip between prefabricated deck slabs supported over bridge girders incorporating CFRP bars and UHPFRC

Glass fiber reinforced polymer (GFRP) bars are used in bridge decks to overcome the problem of corrosion of steel bars and concrete spalling. However, design guidelines for joints between GFRPreinforced precast deck panels supported over girders for accelerated bridge replacement is as yet unavailable. The proposed research investigates the use of GFRP bars in the closure strip between jointed precast deck panels, which is filled with ultra-high performance fiber-reinforced concrete (UHPFRC). Four different bar splice lengths in the joint were considered in this study, namely: 75, 105, 135 and 165 mm, with bar splice spacing taken as 0, 75 and 100 mm. 27 specimens were constructed and tested to-collapse to determine their structural behavior and load carrying capacity. Correlation between experimental findings and available design equations for moment and shear capacities was conducted, leading to recommendations for the use of the proposed joints between precast deck panels in slab-on-girder bridges.

Development and study of closure strip between precast deck panels in accelerated bridge construction

This research investigates the use of glass fiber reinforced polymer (GFRP) bars in bridge decks and ultra-high performance fibre-reinforced concrete (UHPFRC) as filling materials in (i) panelto- panel closure strips between transverse precast full-depth deck panels (FDDPs) supported over girders and (ii) the shear pockets for the panel-to-girder connection. The experimental research program included three phases. Phase I examined pullout strength of straight-end and headed-end GFRP bars embedded into UHPFRC to determine the required closure strip width to develop bar full strength. Phase II included the development and study of closure strip details incorporating UHPFRC as joint-filling materials and GFRP bars projecting into the joint. Three joints of width 200 mm between precast FDDPs were developed, namely: angle-shape joint (Ajoint), C-shape joint (C-shape), and zigzag-shape joint (Z-joint), with 175-mm projecting length of GFRP bars into the joint. Two series of 2500x600x200 mm one-way slabs were cast to investigate the flexural strength of the jointed precast slabs compared to cast-in-place slabs. Two types of concrete were used to fabricate the precast FDDPs, namely: normal concrete (NSC) and high-performance concrete (HPC). Correlation between experimental results and available design equations for moment and shear capacities, as well as CHBDC and AASHTO-LR applied factored design moments, was performed. All specimens failed in either flexural or flexural-shear mode outside the UHPFRC-filled joint. Phase III included testing three pairs of 3700x2500x200 mm laterally-restrained precast FDDPs incorporating the three developed joint details in the transverse direction of the girders. Each pair of specimens was tested under 600x250 mm wheel loading located beside the closure strip, considering (i) constant amplitude fatigue (CAF) loading up to 4 million cycles followed by increasing static loading to-collapse, and (ii) incremental variable amplitude fatigue (VAF) loading to-collapse. The failure mode of the tested slabs was punching shear, with the transverse UHPFRC joint diverting the extension of the punching shear plane to the adjacent precast FDDP segment. Results of fatigue load tests on the three-jointed pairs of slabs showed high fatigue performance. A new prediction model for fatigue life of the GFRP-reinforced, UHPFRC-filled jointed deck slabs was developed.

Comparison of Material Properties of Multilayered Laminates Determined by Testing and Micromechanics

This paper presents an experimental material campaign focusing on fiber-reinforced polymers (FRP) to be applied in a novel bridge deck panel. Laminas based on most commonly used fibers, i.e., glass, carbon, basalt and aramid, were prepared and studied in tension, shear and compression. In the subsequent test stages, different fabric reinforcements (uni- and bi-directional fabrics, woven fabrics, CSM layers) were considered for glass laminas only, and finally, a resultant laminate was designed and tested. Such an approach gives a great opportunity to create “tailor-made” laminates, as required in FRP bridge deck panels. Simultaneously with the laboratory tests, analytical calculations were performed using a few micromechanical models that aimed to determine engineering constants and strength parameters. Then, the results obtained from material testing and analytical calculations were compared, and conclusions on the compliance were drawn. Based on this validation, further analytical calculations may replace time-consuming laboratory tests and facilitate FRP deck design.

Highway bridge deck made of ductile-cast-iron

<p>The application of ductile cast iron to a bridge deck is explored. Produced by casting, the deck can be of any shape without welding and expected to have little possibility of fatigue crack. The deck would be light, about a half of the RC deck, so that it could enhance the seismic resistance of a bridge. The deck is designed following the Japanese design specifications for steel highway bridges. The design is done by 3-D FEM. Through computational simulations and actual casting trials, the ductile cast-iron deck panel with uniform material property is produced successfully. To investigate its structural behavior, the panel is loaded statically. Ductile structural behavior is observed without initiating cracks. Fatigue test is carried out. No fatigue cracks occur even when the number of the loading cycles reaches 10,000,000. The wheel load running test of the 12 deck panels was conducted, ensuring that a very good fatigue resistance．</p>