Abstract
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.
Highlights
It is evident that the bridge deck was in small amplitude, and the vibration generally kept steady in the ambient vibration environment
Components below 0.1 Hz are mainly trend items and components above 10 Hz are not pronounced since the main structural frequencies and excitation frequencies all fall within 10 Hz. e measured data were analyzed in both time and frequency domains
Concluding Remarks is study has presented a flexible asymmetric stress-ribbon pedestrian bridge’s modal properties and dynamic performance via both experimental and analytical methods. e following conclusions could be drawn: (1) Modal test showed that the stress-ribbon footbridge has closely spaced modes, low natural frequencies, and small damping ratios (
Summary
Structures are prone to have longer spans and become much flexible owing to the development of high strength and lightweight materials and innovation in construction methods [1]. is poses new challenges to structural design since slender structures are more susceptible to dynamic loadings such as human excitation or wind turbulence. Stress-ribbon footbridge, always formed by pretension catenary-shaped cables or steel plates with both ends anchored on the abutments, are characterized by closely spaced modes with low natural frequencies [19, 23, 24]. Their dynamic performance under human excitation is often of great concern. E cross section of the bridge consists of two main stress-ribbon plates made of Chinese Q690D steel with a thickness of 40 mm and width of 750 mm at a spacing of 0.4 m, as shown in Figures 1(b) and 1(c). Handrails made of stainless steel net with a height of 1.15 m are erected on both sides of the bridge deck (see Figure 1(d)). e abutments were cast in artificial digging piles using concrete and prestressed anchor cables
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