Design and Maintenance Guide 24 Guide to World War II Hangars DEFENCE ESTATES MINISTRY OF DEFENCE WIND SENSITIVE STRUCTURES December 2001
Crown Copyright 2001 Published by the Ministry of Defence December 2001
Foreword This Guide was prepared under the patronage of HQ STC. This document is for the use of Top Level Budget Holders (TLBHs) for application by the Project Sponsors, Property Managers (PROMs), Establishment Works Consultants (EWCs), Works Services Managers (WSMs) and other parties connected with the hangar. For Projects, the principal users of the document are expected to be Project Sponsors to influence the preparation of the Statement of Requirements, the Project Manager and the designers and installers. In addition, for works services falling within the Property Management remit, the EWC assists the Property Manager in determining the description of task and the WSM is responsible for design, installation and maintenance. MOD addressees should ensure that designers and contractors employed for works connected with the Type C hangar are advised of this Guide. Amendments to this Guide will be advised by Defence Estates (DE) Technical Bulletin, issued to PROM and TLBH Works staff. It is the responsibility of the user to check with the PROM or Project Sponsor if amendments have been issued. There is a feedback form at Annex B, for suggested changes or developments to the document. A hangar notification form is also included at Annex C for feedback on any hangar related problems or works on a hangar building. Technical advice and assistance can be obtained from DE. Approaches may be through local DE offices or directly to the Focal Point: Wind Sensitive Structures Specialist Services Defence Estates Blakemore Drive Sutton Coldfield West Midlands B75 7RL All enquiries in connection with drawings and requests for copies of drawings should be addressed to: Library (DE Information Management) Defence Estates Blakemore Drive Sutton Coldfield West Midlands B75 7RL Information provided is for guidance only and it must be verified and checked for each individual project or works service. December 2001 i
Foreword Use of this Guide does not absolve a Project Manager or WSM from any responsibility relating to the design, neither does the existence of the Guide constrain the Project Manager or WSM from using alternatives, provided such alternatives can be demonstrated to provide a result of equal safety, quality and cost effectiveness. This Guide has been devised for the use of the Crown and its Contractors in the execution of contracts for the Crown. The Crown hereby excludes all liability (other than the liability for death or personal injury) whatsoever and howsoever arising (including, but without limitation, negligence on the part of the Crown, its servants or agents) for any loss or damage however caused where the Guide is used for any other purpose. Compliance with a DE Design and Maintenance Guide will not of itself confer immunity from legal obligations. ii December 2001
Acknowledgement December 2001 iii
Amendments Amendments Page No Date Inserted By iv December 2001
Abbreviations BS DCI DE DMG DWS EWC HQ STC JSP MHE MOD PM PROM TB WSM British Standard Defence Council Institution Defence Estates DE Design & Maintenance Guide Defence Works Services Establishment Works Consultants Headquarters Strike Command Joint Services Publication Mechanical Handling Equipment Ministry of Defence Project Manager Property Manager DE Technical Bulletin Works Services Manager December 2001 v
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Contents FOREWORD ACKNOWLEDGEMENT ABBREVIATIONS 1. INTRODUCTION 2. BACKGROUND 2.1 HISTORY OF TYPE-C HANGARS 2.2 USAGES TODAY 2.3 LOCATIONS OF EXISTING TYPE-C HANGARS 3. DESCRIPTION 3.1 IDENTIFICATION 3.2 DRAWINGS 3.3 MAIN STRUCTURAL ARRANGEMENTS 4. STRUCTURAL APPRAISAL 4.1 DESIGN PHILOSPHY 4.2 MEMBERS ANALYSED 4.3 BACKGROUND TO PERMISSIBLE STRESSES AND LOADING USED IN THE APPRAISAL 4.4 OUTCOME 4.5 CONCLUSION 4.6 IMPLICATIONS OF APPRAISAL CONCLUSION 5. OPERATIONAL REQUIREMENTS 5.1 INTRODUCTION 5.2 HANGAR BUILDING 5.3 PROFESSIONAL AND TECHNICAL INSPECTIONS 6. REFURBISHMENT GENERAL 6.1 INTRODUCTION 6.2 OPTIONS AND RECOMMENDATIONS 6.3 WARRANTIES/GUARANTEES 7. REFURBISHMENT ROOFING 7.1 DESCRIPTION 7.2 PROBLEMS 7.3 ROOFING REQUIREMENTS 7.4 ROOFING MATERIAL 7.5 ROOFING OPTIONS 7.6 DETAILED DESCRIPTION OF ROOFING OPTIONS 7.7 SUMMARY OF ROOFING OPTIONS December 2001 vii
8. REFURBISHMENT - GUTTERS AND DRAINAGE 8.1 DESCRIPTION 8.2 PROBLEMS 8.3 GUTTER PROPOSALS 8.4 GUTTER MATERIAL OPTIONS 8.5 GUTTER ARRANGEMENT 8.6 SNOWBOARDS 8.7 BELOW-GROUND DRAINAGE 9. REFURBISHMENT WINDOWS 9.1 DESCRIPTION 9.2 PROBLEMS 9.3 PROPOSAL FOR WINDOWS 10. REFURBISHMENT WALLS 10.1 DESCRIPTION 10.2 REINFORCED CONCRETE 10.3 DETERIORATION OF WALLS 10.4 ALTERATIONS 10.5 TREATMENT OF EXISTING CLADDING 10.6 PROPOSALS FOR SOLID WALLS 11. REFURBISHMENT DOORS 11.1 DESCRIPTION 11.2 PROBLEMS 11.3 DOOR OPTIONS 11.4 DOOR INSPECTIONS 11.5 HANGAR DOOR OUTRIGGERS 11.6 BLAST AND FRAGMENT PROTECTION 12. ROOF ACCESS 13. STANDARD AND REGULATIONS 13.1 BUILDING REGULATIONS 13.2 PLANNING AND FIRE OFFICER APPROVALS 13.3 CROWN FIRE STANDARDS 13.4 HEALTH AND SAFETY 13.5 PHYSICAL SECURITY 13.6 ENVIRONMENTAL LEGISLATION ANNEXES A B C D E F G H I RECORD DRAWINGS CHANGE SUGGESTION FORM HANGAR NOTIFICATION FORM BASIC WIND SPEED MAP SAFE LOADING ROOFING OPTIONS & DESCRIPTION OF ROOFING MATERIALS WINDOW REFURBISHMENT OPTIONS & TYPICAL WINDOW DRAWINGS DOOR REFURBISHMENT OPTIONS COST COMPARISONS REFERENCES viii December 2001
Guide To World War II Hangars 1 Introduction SCOPE The content of this Guide is applicable to works services and projects. It includes new build, maintenance and refurbishment work. In addition, the guidance relates to safe usage of the hangar and the operations within the structure and in its vicinity. This Guide is intended for use by: Property Managers (PROMs), Establishment Works Consultants (EWCs) and Works Services Managers (WSMs) Project Sponsors, Project Managers, design consultants and contractors users of a Type-C hangar and those engaged in duties connected with the hangar. MOD addressees should ensure that designers and contractors employed for works connected with the Type C hangar are advised of this Guide. This Guide is to be used to provide preliminary advice to assist in the preparation of Statements of Requirement, the undertaking of Option Studies and the preparation of Technical Briefs. It may also be used as the basis for Professional Appraisals as required by DE Specification 005. However, all works be they major repair, major refurbishment or demolition must be supported by an adequate site survey and appropriate assessments by competent engineers. SUMMARY OF CONTENT A description is given of the typical Type C hangar, how it can be identified, its typical structural form and features, drawings that have been prepared for a typical Type C hangar. Using archive drawings as a basis, CAD drawings have been prepared by DE to record the key features of a Type C hangar. A structural appraisal of the hangar has been carried out. This indicates that, generally, the hangars are adequate to cover current loadings provided moderate precautions are taken. Hangars in more exposed locations must be considered individually. Precautions must be taken for the safe undertaking of activities and operations within the hangar and in its vicinity. For example, heavy snowfall can apply excessive loading, due to snow infilling the valleys of the multi-pitched roof. In addition, high winds can necessitate closure of the hangar doors to reduce the effect of dominant openings. The safe use of doors is also addressed with regard to their operation, inspection and maintenance. December 2001 1
Guide To World War II Hangars 1 Introduction The Guide covers hangar refurbishment and the common work items with which a PROM or Project Sponsor will become involved, eg. re-roofing, wall cladding and repair or renewal of doors and windows. Guidance is given in respect of MOD policy, working practices and other standards or codes. Typical solutions are given with illustrations for re-roofing and recladding the walls. Refurbishment options have been developed to include whole life costs. Therefore, the initial costs of the appropriate roofing or cladding solution have been considered in conjunction with subsequent maintenance and operational costs eg. those due to heating losses. The implications of applying the requirements of Crown Fire Standards are addressed where appropriate. MOD security matters are also discussed in the document. This Guide explains how the Type C structure was appraised, the design philosophy adopted and findings of the analysis. Historical design codes, steelwork stresses and the loading criteria are covered. With regard to wind loading, the significance of dominant openings in a hangar building due to doors and windows and the building's permeability is also explained. In summary, it is usually feasible to refurbish a Type-C hangar with practical, economical and attractive, economical solutions, rather than demolish and rebuild. Each hangar should be assessed on a site specific basis, because several factors influence a decision. These include local variations in snow and wind loading, local labour and materials costs, local planning restrictions for use of the building and the proposed life of the hangar. The Type C hangar with its open area of some 4180m² (45,000 sq ft) and a clear headroom for 1934 hangar of 10.770m (35'-4"), and for 1938 hangar of 9.246m (30'-4"), provides a functional and flexible working facility. With adequate routine maintenance and the careful consideration of major refurbishment options, particularly re-roofing, Type C hangars should continue to offer economic hangar accommodation for many years. Readers are reminded of the general duty to provide information on hangar related problems and hangar projects. A proforma is attached at Annex C. The information obtained from this process enables DE to disseminate relevant hangar related technical guidance. 2 December 2001
2 Background 2.1 HISTORY OF TYPE-C HANGARS The Type-C hangar is the most common of all MOD wartime hangars. In the order of 200 Type-C hangars are still in use on the MOD estate in the UK. With good maintenance and periodic refurbishment, many more years of service can be provided. The first Type-C hangars were constructed in the interwar RAF expansion period of the mid-1930's. The design evolved from the earlier type A and B hangars developed during the 1920's. Their construction continued until the early 1940's when, due to wartime commitments, the RAF needed hangars which could be built much faster, and so other types of hangar, mainly of a lighter construction, superseded the Type-C. 2.2 USAGES TODAY The predominant use today is still as aircraft accommodation. Many old airfields have now passed from the RAF to the Army, and the hangars continue to be used for other purposes such as motor transport, garaging and workshops, and the storage of equipment and materials. 2.3 LOCATIONS OF EXISTING TYPE-C HANGARS The list overleaf illustrates known locations of Type-C hangars on the MOD estate. It is believed, however, that the list is not complete and there are Type-C hangars at other locations. Some hangars listed may have been disposed of, either by demolition or through sale. However, the list is the best available at this time and is given for information purposes only. Establishments with Type C Hangar which are not included are requested to complete the form at Annex C and return to the Wind Sensitive Structures Section, Specialist Services at Sutton Coldfield. December 2001 3
Guide To World War II Hangars 2 Background Locations of existing Type-C hangars 1 Abingdon, Dalton Barracks (1) 35 Locking, RAF (1) 2 Aldergrove, RAF (4)) 36 Lossiemouth, RAF (3) 3 Aston Down, PESD (1) 37 Manby (5) 4 Bassingbourn, Army (4)0 38 Marham, RAF (5) 5 Benson, RAF (4) 39 Middle Wallop, AAC (5) 6 Bicester, RAF (1) 40 Mildenhall, RAF (2) 7 Binbrook, RAF (5) 41 Molesworth, RAF (1) 8 Boscombe Down, DERA (1) 42 Netheravon Airfield (1) 9 Bramcote, RAF (5) 43 Newton, RAF (5) 10 Brize Norton, RAF (4) 44 Northolt, RAF (1) 11 Catterick, Army (2) 45 Odiham, RAF (3) 12 Church Fenton, RAF (2) 46 Scampton, RAF (4) 13 Coltishall, RAF (4) 47 Sealand, RAF (1) 14 Cosford, RAF (3) 48 Shawbury, RAF (4) 15 Cottesmore, RAF (4) 49 South Cerney, Army (2) 16 Cranwell RAF (2) 50 St Athan, RAF (4) 17 Debden, RAF (1) 51 St Eval, RAF (1) 18 Dishforth, Army & RAF (5) 52 Stradishall, RAF (1) 19 Driffield, Alamein Barracks (4) 53 Ternhill, Clive Barracks (1) 20 Feltwell, RAF (5) 54 Thorney Island, Baker Barracks (1) 21 Finningley, RAF (5) 55 Topcliffe, Army & RAF (5) 22 Gosport, HMS Sultan (1) 56 Turnhouse, RAF (1) 23 Hemswell (4) 57 Upavon, Army (2) 24 Honington, RAF (5) 58 Upwood, RAF (2) 25 Hullavington, Army (4) 59 Waddington, RAF (2) 26 Kemble, RAF (2) 60 Wattisham Airfield, Army (4) 27 Kinloss, RAF (3) 61 Watton, RAF (4) 28 Kirton Lindsey, Army (3) 62 West Raynham, RAF (4) 29 Leconfield, ASMT (5) 63 Wick, RAF (1) 30 Leeming, RAF (5) 64 Wittering, RAF (2) 31 Leuchars, RAF (4) 65 Wroughton, RAF (1) 32 Lindholme, RAF (1) 66 Wyton, RAF (4) 33 Linton-on-Ouse, RAF (5) 34 Little Rissington (4) (Total: approximately 196Type-C hangars remaining at 66 establishments) 4 December 2001
3 Description 3.1 IDENTIFICATION 3.1.1 General Before commencing work on any hangar, it is clearly important to correctly identify the hangar type. The Type-C hangar is rarely confused with other types, exhibiting a typical multi-pitch roof with a series of ridges and valleys. The only other similar hangars are the Type-A and Type-B from which the Type-C design evolved, and few of these earlier types still remain. Virtually all Type C hangar roofs have the same steel structural frame, comprising a series of primary trusses at 7.62m centres (25ft) each with a clear span of 45.72m (150ft). The primary trusses, in turn, support secondary trusses at 4.572m centres (15ft). This structure forms the multi-pitched roof arrangement with a primary truss aligned on each ridge. At each end of the hangar there are six full height sliding doors, allowing both ends to be fully opened up. 3.1.2 Variations The Type-C hangar may vary in length, internal headroom and cladding material. The overall length is typically 91.44m and varies in 7.62m (25ft) increments from 45.72m to 91.44m (150ft to 300ft). The internal clear height for 1934 hangar of 10.770m (35'-4"), and for 1938 hangar of 9.246m (30'-4"), with an original roof covering either of asbestos cement slates or sheeting. The side walls are usually of brick or concrete although in the Cotswold area, they are sometimes in stone. The following table illustrates the main variations of Type-C hangars: December 2001 5
Guide To World War II Hangars 3 Description YEAR SUB- GROUP 1934 (1) INTERNAL Width x Height 45.72m x 10.770m DIMENSIONS Length 91.44m WALLS Brick or stone DESCRIPTION Hipped end to each duo-pitch roof bay. Hangar 12 bays long and hangar gable ends align with a ridge. One patent glazed window to each bay, approx 6.2m wide x 4.4m high. Solid wall construction to top of wall at roof parapet level. (2) 45.72m x 10.770m 45.72m to 91.44m Brick or stone Hipped end to each duo-pitch roof bay. Hangar length determined by whole number of 7.62m bays. Hangar gable end align with a ridge, providing a vertical face of cladding above the doors. Windows and walls as before. 45.72m x 10.770m 45.72m to 91.44m Concrete 1938 45.72m x 9.246m 91.44m Concrete or brick Ditto Hipped end to each duo-pitch roof bay. Hangar 11 bays long plus 2no half bays at each end. Ends of hangar provide a pitched cantilever roof above the doors. Window height reduced to 3m but in panels either 13.4m or 21.4m long across 2 or 3 structural bays. Wall height only to top of windows, with asbestos cement cladding above to roof level. Figure 3.1 Main Variations of Type-C hangars. The previous table illustrates that there are two main variations of the Type-C hangar, the 1934 and the 1938. There is, in addition, a shorter span version, the structural details of which are not covered by this Guide. The photographs at figures 3.4 to 3.6 illustrate the typical external appearance of the Type C hangar, and show the differences between the 1934 and the 1938 versions. Figure 3.4 shows the rare situation of a 1934 and a 1938 version sited alongside each other. Figures 3.5 and 3.6 show enlarged views of these same hangars. Both have concrete walls, but each has been overclad during past refurbishment. The window areas have also been overclad in translucent sheeting of the same profile as the main wall cladding. 3.1.3 Annexes Most hangars were built with single storey annexes, often to both sides of the hangar and either in brick or concrete according to the hangar wall construction. These provided accommodation for offices, changing rooms, crew rooms, storage and workshops. 3.2 DRAWINGS 3.2.1 Archive drawings A full list of microfilmed drawings and paper drawings is listed in Annex A, and are available from DE Information Management. These drawings have also been scanned, and are available in digital format (PDF documents) and are available from DE Information Management. Site specific as-built drawings are not kept at DE Information Management however, they may be available from the Property Manager or Project Sponsor for a particular site. In view of the reproduction quality of extant drawings, various new drawings were prepared for each of the 1934 and 1938 versions (sect 3.2.2). The following drawings were used in the structural appraisal and these drawings are available from DE Information Management if required. 6 December 2001
3 Description HANGAR DRAWING VERSION NUMBER 1934 2029/34 861/35 865/35 DRAWING TITLE General Arrangement: Plan sections of steelwork Roof Trusses Roof Trusses STORAGE MEDIUM Print Negative Negative Figure 3.2 Archive drawings used in structural appraisal 3.2.2 New DE drawings The new drawings prepared by redrawing typical original plans and details are listed in the following table: HANGAR VERSION C type hangar (1934) C type hangar (1938) DRAWING NUMBER DE/H1/001/101 DE/H1/001/102 DE/H1/001/103 DE/H1/001/104 DE/H1/001/105 DE/H1/001/106 DE/H1/001/201 DE/H1/001/202 DE/H1/001/203 DE/H1/001/204 DE/H1/001/205 DE/H1/001/206 DRAWING TITLE General Arrangement showing original Drainage Foundation Plan and Details of Door Rail Foundations General Arrangement: Plan and Elevations General Arrangement showing Steelwork layout Line diagram showing layout and member sizes of Girder Truss A Secondary Truss sizes and layout of members General Arrangement showing original Drainage Foundation Plan and Details of Door Rail Foundations General Arrangement: Plan and Elevations General Arrangement showing Steelwork layout Line diagram showing layout and member sizes of Girder Truss A Secondary Truss sizes and layout of members Figure 3.3 Schedule of new DE drawings The above drawings have been prepared in AutoCAD and are held both on disc and as A1 size prints obtainable from DE Information Management. Copies of these drawings reduced to A3 size are included at Annex A. 3.2.3 Use of drawings Both the archive and newly prepared drawings should only be regarded as indicative of typical Type-C hangars. For any particular hangar, an on-site inspection should be undertaken to check the as-built structure and building fabric for comparison with the typical construction. The original as-built drawings for the site should be requested from the Property Manager. December 2001 7
Guide To World War II Hangars 3 Description 8 December 2001
3 Description Figure 3.4 View of 1934 and 1938 Versions adjacent each other Figure 3.5 Typical 1934 Type C Hangar Figure 3.6 Typical 1938 Type C Hangar December 2001 9
Guide To World War II Hangars 3 Description 10 December 2001
3 Description 3.3 MAIN STRUCTURAL ARRANGEMENTS Figure 3.1 indicated the main variations of Type C hangars. The following sections give further details of the typical main structural arrangements and member sizes. Reference should be made to relevant new drawings in Sect 3.2.2 and to other archive drawings for further details. Providing the member sizes and arrangements are representative of those detailed on the drawings referred to at Section 3.2.2, the appraisal findings in the later sections are appropriate for use at option study stage. 3.3.1 Lattice roof girders The main girders span the full 45.72m span (150 feet) across the hangar between the columns at 7.62 m centres (25 feet) and support the secondary trusses. For both the Type C34 and Type C38 hangars there are typically three separate main girders referred to on original drawings as Girders A,D and E and their typical locations are shown in DE drawings DE/H/001/104 and 204. The three girder types are similar in size and layout, but by utilising different member sizes have different capacities. Figure 3.7 indicates the typical arrangement and member sizes for Girder A. Laced Column 46456 Laced Column E C F J C F K A G K A (plated) H K A (plated) H A (plated) H K K A (plated) H K A G K C F J C F E D D D B B B B D D D A 2 / 9" x 31/2" A 2 / 9 x 3½ x 22.27 x 22.27 lb/ft lb/ft BSC s BSC's B 2 / 9" x 31/2" B 2 / 9 x 3½ x 22.27 x 22.27 lb/ft lb/ft BSC s BSC's C C 2 / 29 / x 9" 3 x x 3" 17.46 x 17.46 lb/ft lb/ft BSC s BSC's D D 2 / 29 / x 9" 3 x 3" x 17.46 x 17.46 lb/ft lb/ft BSC s BSC's E E 2 / 15 2 / 15" x 6 x x 6" 45 x 45 lb/ft lb/ft BSB s BSB's F F 6 x 6" 5 x x 5" 25 x 25 lb/ft lb/ft BSB BSB G G 6 x 23½ / 6" x 16.46 31/2" x lb/ft 16.48 BSC s lb/ft BSC's H H 6 x 6" 3 x x 3" 12.41 x 12.41 lb/ft lb/ft BSC BSC J J 2/6 2 x / 6" 3½ x x 31/2" 16.48 x 16.48 lb/ft lb/ft BSC s BSC's K K 2/6 2 x / 6" 3 x 3" 12.41 x 12.41 lb/ft lb/ft BSC s BSC's Figure 3.7 Main Truss Details Girders A December 2001 11
Guide To World War II Hangars 3 Description 3.3.2 Secondary trusses The secondary trusses span 7.62m (25 feet) between the supporting primary trusses. The truss depth varies along its span, having the depth of 4.9m at the supports and 1.23m at mid-span, thus forming valley gutters. The original roof was supported directly on the secondary trusses via timber sarking and purlins. Figure 3.8 illustrates the typical arrangement of a secondary truss with runway beam where fitted. Main Truss 7620 Main Truss A A M ain tru ss top chord B D A A D B C C E F C E C M ain tru ss bo tto m c ho rd 10" x 4 1 / 2 " or 10" x 6" Runway Beam A 2 / 4" x 2 1 / 2 " x 1 /4 " B 2 / 31 / 2 " x 3" x 1 /4 " C 2 / 4" x 3" x 5 /16 " D 3" x 3" x 1 / 4 " E 2 / 3" x 3" x 5 / 16 " F 2 / 2" x 2 1 / 2 " x 1 /4 " Figure 3.8 Secondary Truss Details New drawings DE/HI/001/106 and D/DE/HI/001/206 indicate the typical variations to secondary roof trusses. 12 December 2001
3 Description 3.3.3 Columns and base A typical supporting column for a Type C hangar comprises two I beams tied together by a system of diagonal lacing angles, and encased in concrete over their full height. Fig 3.9 illustrates the concrete foundation detail. laced colum n. floor level 762 914 150 1524 1524 Fig 3.9 Column Foundation Detail C34 columns are restrained at mid height by longitudinal 12 x 4 x 31 lb/ft and 9 x 3 x 17 lb/ft rolled steel channels which run along the length of the hangar. In each end bay of a Type C38 hangar a horizontal 6 x 3 rolled steel joist tie is provided. 3.3.4 Runway beams Two sizes of runway beams traverse the full width of the hangar. These run parallel to the main trusses and are attached to the underside of the secondary trusses at 4.572m centres. i.e. 2no. 10 x 4 1 / 2 x 25 lb/ft Joists with 1.5 Tonnes SWL 2no. 10 x 6 x 40 lb/ft Joists, with 6 Tonnes SWL Runway beams are not always present in hangars, neither are they present in each hangar bay. 3.3.5 Vertical bracing There are four sets of diagonal vertical bracing, two on each side of the hangar with each placed in the same structural bay as the roof wind girders at each end of the hangar. The drawings at sect 3.2.2 indicate the roof wind girder and vertical bracing arrangements. December 2001 13
Guide To World War II Hangars 3 Description 3.3.6 Roof wind girders Two lateral wind girders span horizontally across the width of the hangar and are located in the last full structural bay at each end of the hangar. 3.3.7 Lattice stiffening girders (N Truss) At top of door level, these run longitudinally along both side elevations of the hangar. 3.3.8 Doors Each door measures approximately 10.7m high by 8 metres wide and weighs in the order of 12.5 Tonnes. They comprise a series of 10 x 3 channels and 10 x 4 1 / 2 RSJ s, which are externally sheeted in steel plate of varying thickness as follows: 1/4 plate up to 6m high and 1 / 8 " plate above. Originally, windows were fitted above 8.4m height, but these have frequently been replaced with steel plates. Internally the doors are sheeted in 1 / 2 " steel plate but only up to 6m height. Doors have sometimes been filled with gravel as blast protection. In the original design it is apparent that the steel sheeting on both the front and the rear faces on the door frames, are an integral part of the door structure. The steel plates provide strength and stability to the door frame members, and in the case of the lower diagonal bracing members, act as the gusset connection plates. 14 December 2001
4 Structural appraisal For the purpose of this Guide an initial structural appraisal was carried out for a typical Type C34 hangar using typical member sizes represented by the new drawings referred to in Section 3.2.2. The purpose of the appraisal was to examine the main components of the hangar type to check the hangar s ability to carry the loading specified by current loading codes. Structural calculations were undertaken in support of the appraisal. The detailed findings of the appraisal are given later in the various sections which follow. These findings are given purely to assist in the preparation of option studies. The refurbishment solutions given in section 7 are appropriate for Option Study purposes providing that the site conditions, member sizes and loading circumstances are no less/worse than those considered in the appraisal. Where member sizes and loading circumstances differ it will be necessary to undertake further appraisal work at option study stage in order to check the applicability of the solutions offered in this Guide. In any event, the progression to Project stage will require provision of detailed surveys and calculations in support of the chosen option. It is recommended that where further appraisal work is undertaken the following publications are consulted. Appraisal of existing structures - 2nd edition, 1996 - I Struct E Appraisal of existing iron and steel structures - SCI publication 138 Assessing the capacity of existing steelwork - SCI paper AD135 Historical structural steelwork handbook - BCSA The remainder of this Chapter concentrates on the assumptions made in the appraisal process and the detailed findings. An indication is given of the process that a professional civil/structural engineer will normally take prior to advising on the structural adequacy of a site specific Type C hangar and its proposed refurbishment. 4.1 DESIGN PHILOSOPHY The calculations in support of the appraisal were carried out in accordance with the following standards: BS 449 1932 Use of Structural Steelwork in Buildings BS 449 1937 Use of Structural Steelwork in Buildings BS 6399 1996 Part 1 Loading for Buildings Code of Practice for dead and imposed loads BS 6399 1988 Part 3 Loading for Buildings Code of Practice for imposed roof loads BS CP3 Chapter V Part 2 1972 Code of Basic data for the design of buildings - wind loads TICE 104 No 1986 Appraisal of existing and design of new runway and lifting beams (then extant) The appraisal calculations were undertaken to check the main structural members so that informed professional judgement could be made of the adequacy of the generic Type C hangar. December 2001 15
Guide To World War II Hangars 4 Structural appraisal The assumptions made in the appraisal of this generic Type C hangar may, due to site circumstances, not translate to other Type C hangars. The loading conditions, predicted future use, projected life span etc., will vary from site to site. It is recommended that, at Option Study stage, suitable allowances are made for deviations from assumptions made in the appraisal used for this Guide and that a site specific analysis is always considered before drawing any firm conclusions. There are two extant British Standards which could be used in the design of steel frame buildings; namely BS5950 and BS449. Great debate exists as to which of these two codes is more appropriate for the analysis of historical structures. Final selection is to be based upon professional judgement dependent upon the particular circumstances of the structure and scale of project in question. Because this Guide is primarily to support the Option Study process it was considered that use of BS CP3 and BS 449 was appropriate. For new Projects and for the refurbishment of Type C hangars the use of BS 6399 and BS 5950 is considered to be appropriate. 4.2 MEMBERS ANALYSED For the Type C34 hangar the following structural members were analysed: Typical main girders type A, secondary trusses, columns, column foundations runway beams, vertical bracing and roof wind girders. Amongst others, the following members were not checked: Longitudinal edge beam, walls, parapets, purlins, doors, door supports and gantries; untypical members such as end trusses, C-38 cantilever trusses, C-38 main truss supporting cantilever trusses, columns supporting end main trusses, C-38 columns supporting cantilevered roof and associated untypical foundations. The analysis for individual elements of the structure are described in Section 4.4. The most heavily loaded portal frame was considered to be the central frame which supports two 6 ton runway beams. The beams span between the secondary trusses, one beam each side of portal frame (see drawing DE/H1/001/104). 16 December 2001