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Note to users: Articles in Press are peer reviewed, accepted articles to be published in this journal. When the final article is assigned to volumes/issues of the publication, the Article in Press version will be removed and the final version will appear in the associated published volumes/issues of the publication. The date an article was first made available online will be carried over. Please be aware that, although Articles in Press do not have all bibliographic details available yet, they can already be cited using the year of online publication, as follows: author(s), article title, Journal (year).

 

 

Comparison of Live Load Effects for the Design of Bridges

I. Shahid1, S. H. Farooq, A.K. Noman, A. Arshad

Volume 5  |  Issue 3 |  Pages: 87-99 | PDF | HTML

 

Abstract: Design and lifelong structural performance of bridges is primarily governed by the live load models representing truck traffic. In Pakistan, bridges are designed as per Pakistan Code of Practice for Highway Bridges 1967 (“PHB Code”) and American Associations for State Highway and Transportation officials LRFD (Load and resistance factor design) Bridge Design Specifications (“AASHTO”). Further, National Highway Authority (NHA) has specified legal limits on the live loads to prevent overstressing of bridges. Different states of US had calibrated the AASHTO live load model based on the actual truck weights and traffic volume present in the respective states. In Pakistan, service-level truck traffic is significantly different in axle weights, axle configuration, gross vehicle weights (GVW) and traffic volume than that of United States and Canada. Further, in Pakistan, over the years, service-level truck traffic has changed significantly in axle weights, axle configuration, GVW and traffic volume due to developments in truck industry to meet the heavier loads carrying demands by various industries. Thus, live load models specified in 1967 PHB Code, AASHTO live load model and NHA legal limits may not be a true representation of today’s service - level truck traffic of Pakistan. After discussing the different Live Load Models currently in practice for the design of highway bridges in Pakistan, this paper compares the load effects produced by the actual trucks on sample bridges with the load effects of code specified live load models. Three simply supported, Pre-stressed concrete girders/bridges were considered to study the effects of actual trucks and live load models. Maximum load effects were calculated using influence lines by running each truck on the sample bridges. Maximum load effects were also calculated for live load models of respective codes. Normalized load effects were calculated by dividing the truck load effect with the load effect due to code specified load model and results were plotted on probability plot to compare the results. The results show that the highway loading in Pakistan produces much greater load effects than anticipated from the bridge design codes.

 

Keywords: Live Load, HL-93 loading, Class A loading, Lane loading, Gross Vehicle Weight.

 

 

 

 

Evaluation of a GIS-Based Floodplain Height Difference Model for Flood Inundation Mapping, Case Study: Rudbar, Iran

 Mohammad Ali Nezammahalleh, Mojtaba Yamani, Abolghassem Goorabi, Mehran Maghsoudi, Shirin Mohamadkhan

Volume 5  |  Issue 3 |  Pages: 100-106 | PDF | HTML

 

Abstract: Most of the human societies are experiencing increasing losses of flood hazard each year. Flood inundation mapping is useful for flood mitigation and risk reduction. To detect flood inundation areas, a novel GIS-based model has been developed in the present work. This model makes it possible to calculate the height difference of floodplain surfaces from riverbed by the use of terrain data and hydrometric statistics. The output of the model disregards the mountain topography and represents the local terrain of the floodplain. The output along with the peak discharge by Creager model has been applied for the inundation mapping. The estimated values of the model and observed values have a RMSE of 2.58. The results showed a significant difference, at 95% confidence interval, between the flooded and non-flooded villages in the height differences. It can be concluded that the rural settlements lower in height are more at risk of flooding.

 

Keywords: Floodplain Height Difference, flood inundation, GIS-based model, Rudbar

 

 

 

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