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PRACTICAL APPLICATIONS FOR CONSTRUCTION AND THE BUILT ENVIRONMENT


Innovation & Research


Issue No. 95


IN THIS ISSUE Buildings


Design of steel buildings to resist explosions 7 Future energy management for buildings 2 BIM and Energy Performance Modelling 5


Energy 3D terrain modelling made easy 8


Future energy management for buildings 2 Flooding


New technologies for improving fl ood protection of the urban environment 6


Guidance


Built-up walls in modern construction 4 New guidance for glazed roofs


2 Infrastructure


New technologies for improving fl ood protection of the urban environment 6


Modelling 3D terrain modelling made easy 8


BIM and Energy Performance Modelling 5 Research


New projects in structural engineering 3 R&D Enabling Fund call for applications 7


Seismic testing


Seismic testing of sustainable composite cane and mortar walls for low-cost housing 4


Structures


Design of steel buildings to resist explosions 7 New projects in structural engineering 3


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Also at www.innovationandresearchfocus.org.uk


November 2013 People & vehicle stability in fl oods


The frequency of extreme fl ood events is expected to increase signifi cantly due to climate change. It is increasingly necessary, therefore, to know the criti cal hydrodynamic conditi ons as to when people and vehicles become unstable in fl ood waters by sliding or toppling over. Supported by the Royal Academy of Engineering Research Exchanges with China and India Award scheme, Professors Junqiang Xia and Roger Falconer have proposed new criteria for the stability of people and vehicles in fl oods based on theoreti cal and experimental studies.


xtreme fl ood events in populated areas can lead to serious loss of human life, and vehicles can often become hazardous to people and property when they are swept away by fl oods. The risk to people and vehicles varies both in time and space across a fl ood-prone area, and also changes with different shapes and weights. This variation in the degree of hazard posed needs to be estimated quantitatively to improve fl ood risk management, and was the focus of this collaboration.


In investigating the criterion for


fl ooded vehicles, different forces acting on a partially submerged vehicle are stated, together with the corresponding expressions for these forces, and a mechanics-based formula for the incipient velocity is given for partially submerged vehicles under different orientation angles.


Using various die-cast scale model vehicles, over 300 experiments were conducted in a fl ume at Cardiff University, to establish the critical depth and corresponding velocity at the threshold of vehicle instability. Finally, incipient velocities for three vehicle orientation angles were estimated using two approaches: predictions using the scale ratios from small-scale model vehicles; and computations based on derived formulae using the prototype vehicle parameters.


0.0 0.5 1.0 1.5 2.0 2.5 3.0


Abt et al.(1989)


Karvonen et al.(2000) Formula calibrated


0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 h f (m)


Fig. 2 Suggested stability thresholds for adults


for the incipient velocity being derived for the two instability mechanisms of sliding and overtopping. About 50 experimental runs were then conducted in a fl ume at Wuhan University, China, to obtain the conditions of water depth and corresponding velocity for human instability, using a scaled model human body. The experimental data from these studies were then used to determine two parameters in the derived formula for each instability mechanism. Finally, the derived formulae were validated in


by model human data Formula calibrated


by real human data Current exp. data


Depth-incipient velocity relations for prototype vehicles


1.0 2.0 3.0 4.0 5.0 6.0


Formula (1)


U U


Formula (2)


Formula(2) for 90° Formula(1) for 0°and 180 90° (Exp.from 1:24 model) 180°(Exp.from 1:24 model)


0.20.30.40.50.6 h f (m)


Fig. 3 Depth-incipient velocity relations for prototype vehicles


These critical conditions for the prototype, based on the scale ratios, compared well with calculations obtained using the derived formulae, which gives more confi dence in the predicative accuracy of the formula. The data will allow for improved road planning in regards to the orientation of parking in order to reduce the likelihood of cars in areas at risk being swept away by fl oods. For the stability of people in fl ood waters, various different forces have been analysed, with expressions for these forces being published, and with formulae


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detail using current experimental data obtained from scale ratios and for other experimental data using real people. The validation results indicated that the proposed formulae can accurately assess the risk to people subjected to fl oodwaters (see graph above), so the risk can be better forecast and warnings made with a greater degree of certainty.


For further information please contact Prof. Roger A Falconer at Cardiff University (E-mail: FalconerRA@cf.ac.uk), or Prof. Junqiang Xia at Wuhan University (E-mail: xiajq@ whu.edu.cn).


Innovation & Research Focus Issue 95 NOVEMBER 2013 1


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