1. Girder-deck system (cm)
Case Study of First All-FRP Pedestrian Bridge in Taiwan Yeou-Fong Lia, Sainey Badjiea, Walter W. Chena and Yu-Tsung Chiub
aDepartment of Civil Engineering , National Taipei University of Technology, Taiwan.
bIndustrial Technology Research Institute, Material and Chemical Research Laboratory, Taiwan.
Introduction
National Parks are of tremendous worth to our environment and so is Taijiang National Park, the last of the eight national parks in Taiwan. Since the park is located close to the ocean, structures in the park that are built of traditional building materials become subjects of chloride ion attack. Therefore, FRP composite was used to build a steel-free pedestrian in the park. Although it is the first in Taiwan, FRP composites have been utilized in a lot of pedestrian bridge projects elsewhere in the developed nations. In this study, the design of the 8-m FRP pedestrian bridge is presented and finite element method was used for analysis. Results from the theoretical analyses correlated well with the finite element results.
Keywords： Fiber Reinforced Plastic (FRP), Bridge deck, Three-Point Bending Test, Finite Element Analysis
Bridge inventory data
Results
Total length: 8 m (span: 7.5 m)
Width: 1.5 m;
Total weight (Superstructure only): approximately 1.2 tons;
Materials: Pultruded GFRP composite and epoxy adhesive;
Main components: girder, deck and diaphragm;
Maximum deflection: ≤ L/500*;
Load capacity: 4.07 kN/m2
The deflection results from the analyses were compared. For both systems, the maximum deflection was obtain at midspan. The theoretical results had a good correlation with the finite element results for the 8-m girder. On the other hand, the girder-deck system met the deflection requirements.
Analytical methods
8-m girder (cm)
Girder-deck system (cm)
FEA
0.542
1.03
Meets deflection goal
EBT
0.539
L/500 = 1.5
TBT
Ghugal and Sharma
0.544
Equation (1)
0.562
Parts were connected using a combined connection type using both epoxy resin in addition to FRP pins (or bolts). This combined connection type has the best fatigue performance.
Methodology
Both theoretical and numerical tools were used to study the bridge under service loads. First, the finite element model of a component of the bridge (an 8-m girder) is compared against theoretical results. After validation of the model, the girder-deck system is modeled to check for deflection requirements.
Conclusion
An all-GFRP composite pedestrian bridge was built in the high-chloride environment of the Taijiang National Park, Taiwan to counteract corrosion.
A Terrestrial Laser Scanner (TLS) was used to scan the pedestrian bridge and produce a 3D model of the bridge digitally for future reference.
From the analysis results of the 8-m girder, the deflection values for the EBT and TBT are very close when compared with the FEA result, thus verifying the accuracy of the FEA model.
Analyses results of the bridge showed that it has met design goals of AASHTO’s Guide Specifications for Design of FRP Pedestrian Bridges for a deflection not more than L/500.
ANSYS was adopted in the finite element analysis and the model used a 3D SOLID45 element with three d.o.f on each node. A simply supported boundary condition was applied using structural loads. Continuous mesh with shared common nodes was used for connected parts.
Euler Beam Theory (EBT) and Timoshenko Beam Theory (TBT) were adopted.
Equations used in the theoretical analysis are the well known TBT (eq. 1&2) and EBT (eq. 3).
Eq. (2) is from Ghugal and Sharma (2011)**
…..………(1)
* AASHTO (2008) AASHTO Guide Specifications for the Design of FRP Pedestrian Bridges (1st Edition ed.). Washington, DC.: American Association of State Highway and Transportation Officials.
** Ghugal, Y. & Sharma, R. (2011) “A Refined Shear Deformation Theory for Flexure of Thick Beams,” Latin American Journal of Solids and Structures , Vol. 8, No. 2, pp
…..…………(2)
………………………………(3)