IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-1684, p-ISSN: 2320-334X PP 54-62 www.iosrjournals.org International Conference on Innovations in Civil Engineering 54 | Page SCMS School of Engineering and Technology Pressure Distribution Around Net Clad Scaffolds Using Computation Fluid Dynamics Techniques Hassan Irtaza 1 , R.G. Beale 2 , M.H.R. Godley 2 , A. Jameel 3 1 (Department of Civil Engineering, A.M.U., Aligarh 202002, India) 2 ( 2 Faculty of Technology, Design and Environment, Oxford Brookes University, Oxford, U.K.) 3 (University Polytechnic, A.M.U., Aligarh 202002, India) ABSTRACT : Computational Fluid Dynamics simulations of the flow patterns and pressure distributions around scaffolds clad by debris netting were undertaken using Fluent. The models were verified using full-scale data from the Silsoe experimental site and from wind tunnel investigations of the permeability of scaffold nets and from fully clad scaffold models. The simulations show that for net clad scaffolds the Eurocode provisions are correct for the pressure coefficients on windward and side faces. However, for leeward faces a net scaffold a pressure coefficient of zero can be used. Keywords - Scaffold structures, Wind loads, Computational fluid dynamics, Pressure coefficients 1. Introduction Steel scaffolds are extensively used to provide access and support to permanent works during different stages of construction in the UK and other parts of the world. Previous researches into scaffold structures, both experimentally and computationally, have primarily been involved with determining the structural performance. This includes analyses based on effective length in the early stages of research to more advanced non-linear force displacement effects (local as well as global) taking into account the influence of semi-rigid connections and including both material and geometric non-linearity (Beale, 2007) [1]. Limited research has been reported on the magnitude of loads actually acting on the scaffold including wind load. Scaffolds are often clad with nets called debris nets as shown in Fig. 1 to protect both the passers-by and work force from falling debris and also to shield workers from extreme weather. Debris nets are generally woven fabric of varying air penetrability. The main disadvantage of using nets is that there is an increase in the wind load on the structure, particularly on the scaffold to building ties. Such increases in the wind load on the scaffolds make such structures susceptible to damage or collapse under storm conditions. This has led to a number of incidents reported over the past two decades, such as Uppark House, Surrey, which claimed two lives on 25 th January 1990 (Maitra, 1994). Building damage is often caused by windblown scaffolding as well. The UK Health and Safety Executive (HSE, 1994) organized a conference into the wind loads on scaffold structures. Amongst the papers presented in this conference were those on wind damage (Blackmore, 1994), design of net clad structures (Williams, 1994) [2], full-scale tests (Hoxey, 1994) [3] and wind-tunnel tests (Schnabel, 1994). Codes of practice such as those by the British Standards Institution, BS 5975 (BSI, 1996), and in European Codes BS EN 12810 (BSI, 2003), BS EN 12812 (BSI, 2004) include techniques for assessing the increase in tie loading due to wind. Despite this, there have been a number of incidents in recent years where scaffolding has fallen from buildings during storm conditions. In the current design and analysis of scaffolds, the wind loads are derived from experiments conducted on permanent structures and limited allowance is made for the presence of the façades of the building to which the scaffold is attached. Limited research using CFD has been reported to determine the wind loads on temporary structures. Huang et al (2007) [4] used CFD to determine wind loads on high lift structures. Recently Amoroso et al (2010, 2011) [5,6] reported the results of wind tunnel tests on partially clad structures which complement the results reported in this paper and Giannoulis et al (2010) investigated, both experimentally in the field, and by CFD the airflow around a raised permeable panel which could be used to simulate the wind load on net cladded scaffolds. The authors have reported preliminary studies in (Irtaza et al, 2007) [7] and (Irtaza et al, 2009a,b) [8,9]. Due to the highly turbulent nature of the atmospheric boundary layer non-aerodynamic bluff bodies need a large computational domain for external flow fields. Keeping this in mind a model scale of 1:30 of Silsoe Experimental Building (SEB) was selected as a base model and a scaffold cladded with net were considered for this study. The simulation was done on the basis of Silsoe Research Institute (SRI) full-scale data. The velocity profile and the longitudinal turbulence intensities simulated were obtained from SRI site (Richards et al, 2007) [10]. Three different unsteady CFD models, namely Renormalization (RNG) k   , Realizable k   and Reynolds stress model are available in Fluent version 6.3 (Fluent, 2006) and were used to determine the pressure coefficients on the outer and inner face of the net clad scaffolds.