Experiments on Large Structures - Dynamic Behavior of Concrete and Seismic Engineering - page 215

Values respectively ranging from 0.022 g (0.22 m/s 2 ) to 0.14 g (1.40 m/s 2 ) could be
observed with walking and running pedestrian groups. Design codes often specify
the comfort criteria from critical accelerations under service loads, and frequently
depend on the resonance frequencies.

Dynamic tests allow these criteria and their relationships with the dynamic
properties of footbridges to be checked. For this footbridge, the critical acceleration
specified by British standards (BS 5400) and by the Eurocode (EC2.2) is 0.76 m/s 2 ,
whereas the critical acceleration specified by the Ontario code (ONT 83) is 0.48
m/s 2 . These values can be exceeded in certain loading cases specified in Table 6.1.

Maximum accelerations

Loading cases

(m/s 2 ) (g)

1 pedestrian, walking 0.0135 0.132

2 pedestrians, walking 0.0133 0.130

3 pedestrians, walking 0.0159 0.156

4 pedestrians, walking 0.0219 0.215

Pedestrian group, walking 0.0222 0.218

1 pedestrian, running 0.0384 0.377

2 pedestrians, running 0.0604 0.593

3 pedestrians, running 0.1053 1.033

4 pedestrians, running 0.1352 1.326

Pedestrian group, running 0.1425 1.398

Table 6.1. Maximum accelerations on the footbridge

6.5.2. A mixed cable-stayed/suspension bridge

As far as road bridges are concerned, dynamic tests can take place with
controlled traffic, using test vehicles (lorries and trailers) with a specified axle load,
or under ambient vibrations generated by the wind or steady traffic. Bridge
responses are measured by accelerometers, strain gauges and displacement
transducers. Generally, the strains and displacements are used to obtain the dynamic
amplification factor, whilst accelerations are used to obtain the dynamic properties,
even if the accelerations can also be integrated to provide displacement responses.