DETAILS OF ONE ACTUAL EXPERIENCE:

STRUCTURAL ENGINEERING DESIGN

OF

A SINGLE-CELL BOX CULVERT (4650m X 3600m)

AT CH 127+200 EKET – ORON ROAD (SECTION IV OF EAST

– WEST ROAD) IN AKWA-IBOM STATE (February, 2009)

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TABLE OF CONTENT

1.0 INTRODUCTION……………………………………………………3

2.0 EXISTING SITUATION……………………………………………..3

3.0 ENGINEERING AND TECHNICAL ASPECT……………………..43.1 DESIGN PRINCIPLES AND METHOD……………………..43.2 DESIGN PARAMETERS……………………………………..4

4.0 DESIGN COMPUTATION…………………………………………..6

5.0 DESIGN AND CONSTRUCTION NOTES………………………...29

6.0 APPENDIX…………………………….……………………………30

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1.0 INTRODUCTION

The design and construction of single cell reinforced concrete box culvert located at Ch 127+200 come under the project: Dualization of East West Road Section IV Eket-Oron Road (Route 15) KM 99+000-KM 150+000 in Akwa-Ibom State. The cost of the project is twenty-six billion naira only (N26, 000,000,000.00).

The final engineering drawing issued to the contractor, Gitto Costruzioni Generalli Nigeria Limited had no structural drawing of the box culvert whose dimensions were as follows:Clear span = 4650mmClear height = 3600mm.During one of the site meetings we had with the Ministry of Works and the Supervising Consultant, we, Gitto, proposed to do a design of the box culvert. The Engineer’s Representative approved our proposal to do the design. I, the company’s engineer, carried out the structural design of the box culvert structure which was later approved by the Engineer’s Representative for construction. The letter of approval is enclosed with this report.

2.0 EXISTING SITUATION

The Proposed reinforced concrete box culvert is an extension of the existing box culvert located at Ch 127+200. The dimension of the existing box culvert is as follows:-

Thickness of the top slab = 500mmThickness of the side walls = 500mmClear span = 4650mmClear span = 3600mm

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The thickness of the bottom slab could not be ascertained due to the presence of the toe beam.

The wing walls of the existing box culvert were not cast monolithic with the side walls of the culvert. The only connection was at the base of the culvert. The culvert and its wing walls are still in good condition. The demolition of the existing wing walls of the culvert was not anticipated in order not to weaken the existing box culvert.

The ground condition of the proposed culvert location is good. The soil material is reddish brown clay sand.

The discharge flow in the existing box culvert is significantly high so the same cross-sectional area was adopted for the proposed box culvert.

3.0 ENGINEERING AND TECHNICAL ASPECT

3.1 DESIGN PRINCIPLES AND METHOD

Ultimate limit state and serviceability limit state were adopted for the design of the structural elements.

The structure was analyzed assuming all joints between slabs and walls are rigid, with positive and negative bending moments determined by the theory of elasticity. Sidesway was not considered in the analysis. The bending moments were calculated by considering the possible incidence of the loads and pressures. Three conditions of loadings were considered: (1) Full load and surcharge on the top slab, the weight of the walls, and maximum earth pressure on the walls; (2) Minimum load on the top slab, minimum earth pressure on the walls, weight of walls, maximum horizontal pressure from water in the culvert, and possible upward pressure on the top slab;(3) Maximum load on the top slab, minimum earth pressure on the walls, and weight of walls.

3.2 DESIGN PARAMETERS

3.2.1 Materials:

All concrete members cast in-situ to grade 25 at 28 days.

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Reinforcing steel to grade 460 (high yield bars to BS 4449).Weight of concrete = 24 kN/m3

3.2.2 Standards and References:

British standardsBS 5400, Steel, concrete and composite bridgesPart 2: 1978, Specification for loads.Part 4: 1990, Code of practice for design of concrete bridges.

BS 8110, Structural use of concrete Part 1: 1997, Code of practice for design and construction.

Charles E. Reynolds and James C. Steedman, 1997, REINFORCED CONCRETE DESIGNER’S HANDBOOK, 10th Edition, Spon Press Taylor and Francis Group, London.

Design manual for roads and bridgesDMRB Volume 2 Section 2 Part 12 – BD 31/01 – The Design of Buried Concrete Box and Portal Frame Structures.

DMRB Volume 1 Section 3 Part 14 – BD 37/01 – Loads for Highway Bridges.

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4.0 DESIGN COMPUTATION

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Fig. 1: Existing box culvert at Ch. 127+200 to be extended.

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6.0 APPENDICES

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