PowerPoint Presentation

Twapia Lubuto Bridge

Structural Design Premise 31 October 2014

1CONTENTINTRODUCTIONBRIDGE DETAILSDESIGN PREMISEANALYSIS & RESULTSCONCLUSION2INTRODUCTIONRDA has appointed Messrs Kiran & Musonda Associates and Gomes Haulage Limited Joint Venture as the Consulting Engineer and Contractor respectively for the upgrading of Indeni to Fatima Girls Secondary School Road in Ndola town.

The Road distance is 14.3Km

Project included 2 new bridges: Munkulungwe and Twapia Bridge

This presentation is for Twapia - Lubuto Bridge 3INTRODUCTION, contdTwapia Lubuto Bridge has been designed using a 1:50 year flood return period.The bridge structure is a composite structure made up of a 325mm thick concrete slab supported by 5 No structural steel trusses which are in turn supported by concrete abutments. The bridge length is 20m.The structure is located at Global Positioning Systems (GPS) coordinates S130009.9 and E 283547.5.

The bridge Span length is approximately of 20m and its width, measured between kerbs is 6100mm.

4INTRODUCTION, contd

5MODEL BRIDGE DETAILSDeck (Trusses and Slab)1.05m deep continuous structural steel + 325mm deep concrete slab on 1.2mm thick bondek permanent formwork

Joints & BearingsHornel Bearings

AbutmentsReinforced concrete having strength of 30MPa

Surfacing50mm thick asphalt concrete

6DESIGN PREMISEDesign Code/ManualSATCC Draft Code of Practice for the Design of Road Bridges and CulvertsAASHTO Bridge Design Loading Exposure ConditionsModerateMaterial PropertiesReinforced concrete: Characteristic strength = 30MPaHigh tensile reinforcing bars: Characteristic strength = 460MPaStructural Steel: Characteristic strength = 350MPaDesign Load FactorsIn accordance with Tables 2.1,2.2 of SATCC Code and summarized below

7DESIGN PREMISETraffic Loading Used NA Section 2.6.3NB Section 2.6.3Type NB36 used

No other traffic loading is considered to act in conjunction with NB Loading

8ANALYSIS AND RESULTSFinite Element Design Software Strands 7 was used for the analysis

9ANALYSIS AND RESULTSDeflections NA Loading

10ANALYSIS AND RESULTSDeflections NB36 Loading

11ANALYSIS AND RESULTSAxial Stresses

12ANALYSIS AND RESULTSAxial Stresses

13ANALYSIS AND RESULTSAxial Stresses

14ANALYSIS AND RESULTSStructural Capacity check

Bottom chord, diagonals, brace diagonals, brace top & bottom chord, end struts, top chord and verticals all have capacity greater than expected loading. See Appendix 1

15CONCLUSIONStructural CapacityThe bridge Members have sufficient capacity when subjected to NA, NB36 and AASHTO HS20-44 LoadingsThe bridge members fail when subjected to NC Super loading. Strengthening of the bridge will be required should the route be used for abnormal super loads. Central Pier can also be considered but structural behavior of supper structure will change and must be re-designed

Serviceability CheckSATCC Code silent on maximum allowable deflection but industry norm is span/250 for normal use or span/300 for sensitive ones .i.e. 80mm or 66mmMaximum deflection obtained on model is 31mm on the NA Loading cases 1 and 2Calculated deflections on the unitary truss model are within acceptable limitsObserved actual site deflections are unusual. Next presentation to focus on this matter16 THANK YOU17 APPENDIX 118APPENDIX 1.1: Bottom Chord

APPENDIX 1.2: Diagonals

APPENDIX 1.3: Brace Diagonals

APPENDIX 1.4: Brace Top and Bottom Chords

APPENDIX 1.5: End Strut

APPENDIX 1.6: Top Chord

APPENDIX 1.7: Verticals

APPENDIX 226APPENDIX 2.1: AASHTO H20 40 LOADINGThe American Association of State Highway Transportation Officials (AASHTO) developed a concept of the hypothetical trucks, called H (with 2 axles) and the HS (with 3 axles) classes of Trucks These are fictitious trucks, used only for design and do not resemble any real truck on the road. An AASHTO Truck class HS20-40 was loaded onto the bridge model and satisfactory structural capacity of the model was obtained and was included in Design Report