Research Articles (Civil Engineering)

Permanent URI for this collection

https://scholar.sun.ac.za/handle/10019.1/761

Browse

Browsing Research Articles (Civil Engineering) by Subject "Bridges -- Design and construction"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Seismic evaluation of the northbound N1/R300 bridge interchange
    (South African Institution of Civil Engineering, 2016) Solms, M. N.; Haas, T. N.
    The design of the Stellenberg Interchange was finalised in 1982, with construction completed in 1986. The bridge was designed using a code of practice which did not include any requirements for seismic excitation. This code was superseded by the Code of Practice for the Design of Highway Bridges and Culverts, which provides detailed analysis guidelines for bridges located in seismic-prone areas. According to this code, the bridge is located in a seismic-prone area with an anticipated peak ground acceleration of 0.1 g. Current research suggests that this region could be exposed to a peak ground acceleration of approximately 0.2 g. Upon inspection of the bridge, it was noted that the bridge does not conform to modern-day best practice guidelines for bridges located in seismic-prone regions. These factors necessitated an exploratory investigation to determine whether the bridge can sustain earthquake magnitudes between 0.05 g and 0.2 g. The study was conducted by experimentally determining the natural frequencies with its corresponding mode shapes, which were used to calibrate a finite element model. The finite element model was subjected to different magnitude earthquakes to determine its structural integrity. The results show that, for an earthquake of 0.1 g, the bending moment at one of the column bases is exceeded, while two other column base moments are within 15% of its design capacity. For a 0.2 g magnitude earthquake, the design bending moments at five columns are significantly exceeded, while three other columns' design moments are close to being exceeded. The exceedance of the design moments could lead to significant damage, with the possibility of collapse of the bridge.
  • Thumbnail Image
    Item
    Traffic characteristics and bridge loading in South Africa
    (Journal of the South African Institution of Civil Engineering, 2017-12) Lenner, Roman; De Wet, Gerhard; Viljoen, Celeste
    ENGLISH ABSTRACT: The loading model of the Technical Manual for Highways (TMH-7) published for bridge design in South Africa is in need of revision and simplification. The frequency of heavy vehicle loads has increased and the current application of the loading model is unnecessarily cumbersome. This paper aims to compare the heavy vehicle traffic loading of South Africa and Europe. A comparison of global internal bridge forces under the NA loading of TMH-7 and LM1 loading of Eurocode provides an indication of how current South African provision relates to the ones adopted in Europe. Above all, the traffic characteristics in South Africa are investigated in comparison to data used in development of LM1. LM1 loading generally results in higher internal forces when compared to TMH-7 loading. A direct adoption would thus imply more expensive bridges across South Africa without substantiation, considering the satisfactory past performance of existing structures. More importantly, the gross vehicle weights observed in South Africa are higher than those used for the development of LM1, indicating that the current TMH-7 distributed loading may be too low. Axle loads and their variability in South Africa are somewhat less than in Europe, so local design effects are less of a concern. It is apparent that further urgent work is required to establish a load model that reflects the current heavy vehicle traffic and predicts appropriate characteristic vertical loads.