General Information

Figure 1 shows a pedestrian suspension bridge.

Suspension bridge.
Suspension over a creek
Type Single-span suspension bridge
Main span ≅ 10 m
Deck width ≅ 0.6 m
Pylon Timber logs (shore 1); timber log and trees (shore 2)
Girder Bamboo transverse pole beam


Figure 2 shows the pylon on shore 1.

Pylon (shore 1).
Pylon made of timber logs

The pylon is made of timber logs and consists of two verticals (1 and 2), three cross-beams (3 to 5), and a brace. The latter consists of a vertical (6) and a diagonal (7), which is connected to vertical 1 by nails. The verticals' bases are embedded in the ground, the cross-beams are connected by nails, and diagonal 7 is tied to vertical 6 by a rope and a short bamboo pole. The main cables are made of ropes; they pass over the upper cross-beams (4 and 5) and are tied at the bottom cross-beam (3). The pylon height h ≅ 2 m, and the width b ≅ 0.7 m. Figure 3 shows the opposite pylon.

Pylon (shore 2).
Pylon made of two trees and a timber log

The pylon is made of two trees and a timber log. The former are the verticals, while the latter is the cross-beam, which is tied to the verticals by ropes and short bamboo poles. The height h1 and the width b1 ≅ 2 m. Figure 4 shows a main span sector.

Main span.
Bamboo pole deck of a suspension bridge

The deck consists of six bamboo poles placed side-by-side that are tied together by ropes. The hanger cables (also made of ropes) are tied to the main cables, the girders, and the deck's external poles. Abutment are not installed, the bamboo poles' ends are placed directly over the creek banks. Figure 5 shows a front view of the pylon on shore 1.

Pylon (shore 1).
Pylon out of axis

There is an eccentricity (e) between the axes of the deck and pylon, causing a deviation angle of the main- and hanger cables. Figure 6 shows a schematic layout of the bridge.

Layout of a pedestrian suspension bridge

The vertical vibration of the main span during pedestrian-induced excitation is shown in video 1.

Video 1. Vertical vibration during pedestrian-induced excitation.

Video 2 shows the pylon vibration on shore 1 during pedestrian-induced excitation.

Video 2. Vibration during pedestrian-induced excitation (pylon shore 1).
  • What are some possible measures to reduce the vertical vibration of the main span?