Comparison of Reynolds averaging Navier-Stokes (RANS) turbulent models in predicting wind pressure on tall buildings

This paper presents a detailed comparison of using Reynolds Averaging Navier-Stokes (RANS) approach in predicting wind pressure on a super-tall 406 m slender tower with circular cross-section. The results obtained from wind tunnel tests using a rigid model approach in a boundary layer wind tunnel (BLWT) were compared to that of Computational Fluid Dynamics (CFD) numerical simulations. The main objective of this study is to critically investigate the possibility of using RANS turbulent model based CFD approach in tall building design. Three different RANS turbulence models were compared with the wind tunnel data in predicting flow characteristics. The detailed wind tunnel experimental procedure and numerical approach are discussed and presented. It was shown that the shear stress transport (SST) variant model,could predict pressure coefficients comparable to that of the wind tunnel experiments. The influence of flow separation point on flow characterisation and pressure prediction is highlighted. The improvement that can be made in the near-wall region in the finite volume mesh to achieve an accurate separation point is presented. The effects of Reynolds number produced in the wind tunnel and scaled-down numerical models were compared with the anticipated full-scale flow Reynolds number. Hence, it is shown that a correct modelling technique in CFD using RANS turbulence models can be used as an alternative design approach of super-tall structures to estimate wind-induced pressures.ARC DE150101703, CERDS USy

Numerical and analytical investigation of load transfer through eccentric columns with different cross sections

Eccentric columns are not a common feature in concrete building structures. However, late changes in floor layouts and constraints due to available spaces may enforce structural designers to use eccentric columns to transfer vertical load. The load paths of the eccentric column connections can create complications. Due to the sudden changes in geometry, additional stresses are developed at the slab- column connection and a discontinuity region is created in which the strain distribution becomes highly nonlinear and unpredictable. The strut and tie method has been extensively used in analysing such complicated structural elements over the years. This method has its own limitations and is based on simplifications including the definition of the load path. This simplified method can under or over predict the design capacities of such columns, which can be inefficient or inadequate for current design requirements. The objective of this study is to comprehensively investigate the load transfer mechanism for vertical loads of eccentric columns using an advanced finite element approach. Clear identification of the load path, effective cross-sectional area for load transfer and alternative design guidelines for column-slab joint are evaluated and the preliminary work is presented in this paper.ARC DE15010170

Numerical simulation of impact and penetration of ogvial shaped projectiles through steel plate structures

There is an urgent need to develop light-weight protective structures with a sufficient protection to prevent the damage occurring during extreme loading events such as blast and ballistic impacts. This study is a part of ongoing research to develop light weight amour materials which can sustain under those severe conditions. Numerical modelling with explicit finite element code LS-DYNA has performed with realistic geometries. Ballistic protection class BR7 in European norm EN 1063 considered, thus penetration of different shaped projectiles through thick steel plates was examined. Since the geometries and materials of the projectiles have a very significant influence on the outcome of this research detail modelling of the projectiles was performed. For the purpose of this paper, perforation mechanism of 7.62mm APM2 bullet through 6mm thick Weldox 460E high strength structural steel plate was examined. Largrangian methods combined with Johnson-Cook material model available in the LS-DYNA were used for the numerical simulations. Finally the ballistic limit curve for the 6mm thick Weldox 460E plate perforated by APM2 bullet was obtained. Results were compared with the analytical models

Improving the safety of buildings through an innovative sustainable facade system

A building’s façade system is the outer layer of a structure that is designed to provide protection to building occupants and contents from external hazards with varying intensity. In the modern world, many structures undergo different types of dynamic loadings such as blast and ballistics, earthquakes, high winds, hurricanes, tsunamis etc. It is a prime importance of the modern structures to sustain those dynamic loadings without excessive damage. Due to the recent trend towards sustainable development, there are more prevalent uses of innovative systems such as the double skin façade systems, which lead to new challenges in assessing the performance of these façade systems under extreme loadings. This paper presents a review of innovative double layer skin façade system with some finite element modeling to assess the behaviour

Bioremediation for water purification· A case study at St. Coombs Lake, Talawakelle

Phytorernediation is one of the most eco friendly and innovative techniques to remove pollutants fromsoi I and water in agricu Itural areas. Th is study explored potentials ofbioremediation for water purificationat Tea Research Institute of Sri Lanka through monitoring water quality of St. Coombs lake andthrough several glasshouse and laboratory experiments for validating the resu Its during the period ofNovember 2004- February of2005.The water qual ity parameters such as pH, nitrate, phosphate, iron and total col iforrns at 35 DC / 100 rnland Escherichia coli at 44° C / 100 ml were monitored during dry and rainy periods. The possiblecauses for water pollution of the lake were also monitored. Nitrate pollution was greater during rainyperiods since higher contribution of erosion and runoff. Higher levels of total coliforms and Escherichiacoli were observed in both seasons. Five plant species traditionally known to have phytorernedialproperties i.e. Kang kong (Ipomea aquaticai, Giant reed (Arunda danax), Water hyacinthiEichhornia cracipesi, Bulrush (Scirpus lacustris) and Kurnbuk (Terminalia arjuna) wereevaluated for nutrient absorption. The histology of Kumbuk and Tea roots were assessed for theiranatomical attributes to the biorernediation properties.The differences in root anatomical traits in different plant species lead to differences in nutrient andwater absorption. Kang kong, Water hyacinth and Bulrush showed better performances in nutrientabsorption. The results supported the potentials and technical attributes to common biorernediationplant species in purification of water. These attempts would be environmentally and user friendly, costeffective as well as aesthetic advantages and long-term applicability compared to chemical treatments.

Estimation of skin friction on bored and cast In-situ concrete Piles in sand

Bored and cast in-situ piles in Sri Lanka are design as end bearing piles and the skin friction contribution is generally I neglected. Results of the high strain dynamic load tests are presented to show that a significant skin friction capacity is developed on bored and cast in-situ piles. The distribution of the skin friction along the pile shaft, obtained from high strain dynamic testing of piles, is used to investigate the accuracy of the commonly used skin friction capacity estimation methods

Numerical simulations of response of tubular steel beams to close-range explosions

A numerical study of hollow and concrete-filled square tubular steel columns subjected to near-field detonations has been undertaken and validated through the experimental results. The experiments used concrete-filled and hollow square tubular columns (100 x 5 mm SHS Grade C350) made out of cold-formed structural steel hollow sections (SHS) that were simply supported at both ends. High explosives TNT charges were placed above the top surface of the column at two different scaled standoff distances of 0.12 m/kg1/3 and 0.15 m/kg1/3. Failure patterns and permanent mid-span deformations were recorded and compared with the numerical analysis results. Arbitrary Lagrangian-Eulerian (ALE) formulations coupled with fluid-structure interaction (FSI) algorithms that are available in the advanced finite element code LS-DYNA were used in the numerical study. A detailed description of the numerical technique adopted in the study is presented. The models were validated with the experimental results and were used to obtain the failure pattern, permanent plastic deformation, pressure and impulse time histories, stress distribution, and energy absorption of the different configurations of the columns. The performance of hollow and concrete-filled SHS tubes for blast load mitigation was assessed and discussed

Experimental investigation and simplified modeling of response of steel plates subjected to close-in blast loading from spherical liquid explosive charges

Detonations of nitromethane spherical charges have been carried out to study close-in blast loading of steel plates and the effectiveness of several protective solutions. Three types of bare steel plates, namely mild steel, high-strength steel, and stainless steel were subjected to explosive blast loading. Steel plates of the same type with polyurea coating and composite covers were also subjected to localized blast loading. During an explosive field trial, the blast pressures and displacements of steel plates were measured. Additionally, loading of steel plates by the impinging detonation products was captured by high-speed video recordings. This experimental program has produced results which can be used to calibrate numerical models and to refine the simplified models for predicting blast loads and response of structural elements due to close-in detonations. The effectiveness of polyurea coating for enhancing blast protection of steel plated structures is discussed. The engineering-level model for predicting the blast impact impulse of the detonation gases from the charges in close proximity from the target is introduced and validated using the experimental results obtained during the course of the explosive trials

ICSECM 2015 - Wind Design of Slender Tall Buildings: CFD Approach

Urbanization has led to the uprising of such buildings in densely populated areas where land availability and prices are a concern in such areas. Where such concerns exist the land must be fully exploited and thus constructions of tall buildings are always found as a solution in such areas. Wind behaviour is a key designing parameter for such building and need to be assessed accurately in the preliminary and secondary design stages. As most of the existing design codes have their own limitations in providing necessary guidelines for the wind designing, such as height limits of the buildings, the existing practice is to conduct wind tunnel tests to determine the wind induced loads on the buildings. However, the cost of the wind tunnel test is comparatively high and conducting wind tunnel tests at preliminary design stage is uneconomical. The rapid growth of Computation Fluid Dynamic (CFD) technique over the last few decades enables Engineers to simulate the wind behaviour around moving objects such as aeroplanes and automobiles. Therefore use of such methodology to predict wind loads on the buildings, especially at the preliminary design stages could be beneficial. This paper discusses a preliminary investigation that carried out on a non-typical 350m tall slender building using CFD approach.Urbanization has led to the uprising of such buildings in densely populated areas where land availability and prices are a concern in such areas. Where such concerns exist the land must be fully exploited and thus constructions of tall buildings are always found as a solution in such areas. Wind behaviour is a key designing parameter for such building and need to be assessed accurately in the preliminary and secondary design stages. As most of the existing design codes have their own limitations in providing necessary guidelines for the wind designing, such as height limits of the buildings, the existing practice is to conduct wind tunnel tests to determine the wind induced loads on the buildings. However, the cost of the wind tunnel test is comparatively high and conducting wind tunnel tests at preliminary design stage is uneconomical. The rapid growth of Computation Fluid Dynamic (CFD) technique over the last few decades enables Engineers to simulate the wind behaviour around moving objects such as aeroplanes and automobiles. Therefore use of such methodology to predict wind loads on the buildings, especially at the preliminary design stages could be beneficial. This paper discusses a preliminary investigation that carried out on a non-typical 350m tall slender building using CFD approach