Volume 5, Issue 3, (2017)
Table of Contents
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
A Structural Health Monitoring Technique
S. A. Maqbool, A. Arshad
Volume 5 | Issue 3 | Pages: 107-113 | PDF | HTML
Abstract: The addition of carbon microfibers has proved to be one of the most effective means of improving the electrical conductivity of cementations matrix. In the present study, 5x5x5cm carbon fiber reinforced mortar specimens were positioned in a 60Hz, ± 2.5V AC circuit with a data acquisition system in order to monitor the changes in its electrical resistivity under the influence of different parameters. It was seen that a high fiber fraction and low moisture content makes the specimen act like a pure resistor with negligible capacitance or inductance associated with it. It was also observed that electronic conduction was dominant over electrolytic conduction in a mix proportion with high fiber volume fraction and low water to cement ratio. The resistivity was found to steadily decrease under compressive loading and then increase during the formation of micro and macro-cracks. This study provides an appropriate basis to monitor the health of structures by measuring the increase in electrical resistivity versus the load during the life time of the concrete structures.
Keywords: Concrete, carbon fiber, resistivity, loading rate
Copyright © Journal of Environmental Treatment Techniques
(JETT)
Dorma Trading, Est. Publishing Manager