@conference {692, title = {An Analytical Method for the Estimation of Radiation Heat Flux from Open pool Fires and pool Fires Im-pinging on Ceilings}, booktitle = {10th Asia-Oceania Symposium on Fire Science and Technology}, year = {2015}, address = {Tsukuba, Japan }, abstract = {

This paper presents a new integral method for the estimation of the thermal radiation flux from open pool in air fires and pool fires having flames sometimes impinging under extensive ceilings. For open fires, a uniformly distributed emissive power to the cylinder that represents the flame envelop is used together with a radiant fraction that depends on the source diameter. Estimations and comparisons are produced using the mean as well as the continuous (stoichiometric) flame heights which is calculated and correlated numerically including flames impinging on the ceiling. The applicability of the method and comparison with previous analytical methods is validated for a range of heat release rates (1 to 300 kW) using experimental results of the literature. For fires under ceilings, the gas temperature distribution under the ceiling is used to estimate the thermal radiation from a disc that represents the flames if flames impinge on the ceiling as well the hot gases in all the ceiling layer. Radiation flux from the ceiling jet is significant in this case, while the lower and higher values are estimated for the complicated view factor, assuming that the flame cylinder under the ceiling is opaque or transparent. Estimations are compared with experimental results of the literature, indicating that the adoption of a transparent flame cylinder produces conservative results for all the cases examined.

}, keywords = {Ceiling, Simplified modelling, Thermal radiation}, author = {Vouros, Α and Delichatsios, ΜΑ and Zhang, J} } @article {693, title = {Hybrid Simulation of Bridge Pier Uplifting}, journal = {Bulletin of Earthquake Engineering}, year = {2015}, abstract = {

Substructured Pseudodynamic (PsD) testing is used to study the transverse seismic response of a bridge with box-girder deck monolithically connected
to circular piers, but free to move laterally at the abutments. The tests are of two types, each one with two variants: with the pier footing rocking on elastic soil and
uplifting from it, or fixed to rigid ground. The first type concerns a two-span deck connected monolithically to a central pier and supported at each end on the abutment
through a pair of elastomeric bearings, which are stiff and strong in compression but very soft and weak in tension. The second one concerns the interior
piers of multi-span bridges having all spans equal and all piers similar. The pier was physically tested at 1:2 scale; everything else was numerically simulated
online with Opensees. The deck, the soil and the bearings were modeled as elastic, but not allowing tension to develop at the soil-footing interface, and the bearings
two orders of magnitude more flexible in tension than in compression. In the first type of tests, at a peak ground acceleration (PGA) of 0.15g, the footing uplifted,
the bearings developed tension, but the pier stayed elastic. In the second type of tests, with a PGA of 0.4g, uplifting of the footing did not prevent plastic hinging at
the pier base, but reduced significantly the pier damage. A cyclic quasi-static test in the end shows the deformation capacity margins of the pier.

}, keywords = {bridge piers, distributed testing, Foundation uplifting, Hybrid simulation}, author = {Stathas, N and Skafida, S and Bousias, SN and Fardis, MN and Digenis, S and Palios, X} } @conference {688, title = {Numerical and experimental validation study of flame extent of a pool fire under the ceiling}, booktitle = {MCS-2015: Ninth Mediterranean Combustion Symposium}, year = {2015}, address = {Rhodes, Greece}, abstract = {

The purpose of this work is to establish dimensionless correlations for the flame extent under a ceiling to be used for large scale calculations of radiative heat fluxes for which numerical simulations may be prohibitive and probably, not credible. Towards this objective, this paper presents a numerical study of the flame height in an open pool fire and the subsequent flame extent under the ceiling. Fire dynamics simulator (FDS, version 6) was applied. The stoichiometric mixture faction was used to define the continuous flame height which also coincides with the maximum mean temperature on the axis of the fire. The size of the pool fire was 0.1m {\texttimes} 0.1 m having heat release rates (HRRs) from 2 to 100 kW for two heights 30 and 50 cm. The predicted free flame height and horizontal flame extent are plotted as functions of HRR and compared to correlations and experimental data in the literature. Because most of the correlations and measurements are based on the mean (visual) flame height, the predicted continuous flame height is found to be 3/5 of the experimentally mean flame height. It is found that the predicted flame height and horizontal flame extent agree well with existing experimental relations. However, some difference was noted in the horizontal flame extent indicating that the relation between the mean and continuous flame heights derived for an open free pool fire may no longer apply due to the presence of the ceiling affecting the entrainment and the turbulence of the ceiling flame jet.

}, author = {Wang, Y and Vouros, A and Zhang, J and Delichatsios, M} }