Nieuwklap Bridge

Abstract

The actual shear capacity of existing reinforced concrete solid slab bridges, constructed before 1960 in the Netherlands, is subject of an extensive research nowadays, since additional sources, increasing the total shear capacity of concrete slabs, have been ascertained to be present. In addition, the increasing occurrence of human-induced earthquakes in the province of Groningen due to gas extraction, arises uncertainties regarding the seismic behaviour and earthquake resistance of existing bridges in this area. The Nieuwklap bridge is a reinforced concrete solid slab bridge located in the Groningen province, combining both characteristics under investigation.
In the course of this research, the first two Levels of Assessment have been applied for the static analysis of the slab part of the deck of the Nieuwklap bridge, which was found to have sufficient shear and bending moment resistance under the application of the traffic loading defined by the current standards. The equivalent proof load tandems, that generate the same shear and bending moment stresses, for each load combination level have been found with both approaches, proving that localized phenomena at the area of load application are more intense when the field experiment takes place. Furthermore, by obtaining the equivalent tandem loading that leads to shear and flexural failure of the concrete slab, it has been concluded that flexural failure due to yielding of the reinforcement will occur first in case of exerting the collapse loading on the flexure-critical positions or on the shear-critical positions next to the end-supports. However, in case of applying the tandem loading on a shear-critical position next to a continuous support it is difficult to define which failure mode will precede.
Regarding the seismic evaluation of the Nieuwklap bridge, the simplified fundamental mode method and a modal response spectrum analysis have been used. The bridge deck has been found to have adequate resistance against the vertical component of the seismic excitation, which cannot be considered critical, generating nearly the half stresses compared to the traffic load (LM1) combination defined by Eurocode 2. The piers and the pendulums supporting the bridge deck have been also evaluated against the two horizontal components of the seismic excitation, for two different earthquake return periods, discovering that they are able to withstand the generated forces without additional measures. Finally, from the performed modal analysis it has been obtained that movement of the bridge on the longitudinal direction can be observed in lower frequencies compared to the vertical and the transverse direction and that more than 10 modes are necessary in order to describe accurately the bridge behaviour.
This Thesis describes the framework that can be used to prepare collapse tests at multiple Levels of Assessment, and for the seismic assessment of existing bridges in regions with recently initiated seismic activity.