bridge on a canal

a presentation on Bridge construction by p.w.d bijnour: 

a presentation on Bridge construction by p.w.d bijnour By Bahul anand b.Tech final

Introduction to Bridges: 

Introduction to Bridges

What is a bridge?: 

What is a bridge? A bridge is a structure that spans a divide such as: A stream/river/ravine/valley Railroad track/roadway/waterway The traffic that uses a bridge may include: Pedestrian or cycle traffic Vehicular or rail traffic Water/gas pipes A combination of all the above

Classification of Bridges ooften made by p.w.d : 

Classification of Bridges ooften made by p.w.d Concrete Bridge Steel Bridge Timber Bridge Composite Bridge Based on Material used

Function of A Bridge: 

Function of A Bridge A bridge has to carry a service (which may be highway or railway traffic, a footpath, public utilities, etc.) over an obstacle (which may be another road or railway, a river, a valley, etc.) and to transfer the loads from the service to the foundations at ground level.

General Span Types: 

General Span Types

Projects of p.w.d bijnor in my training period: 

Projects of p.w.d bijnor in my training period Construction of bridge on a distributory canal Repairing of damaged bridge in bijnor

Drawing of bridge formed on canal: 

Drawing of bridge formed on canal

Components of Bridge: 

Components of Bridge Caisson/Raft Foundation Bridge Pier Bearing Deck Slab Roadway Railing Abutment 1 7 3 4 6 1 7

Site picture : 

Site picture

About the canal bridge under construction: 

About the canal bridge under construction The loads is to be transferred to the bearings and piers and hence to the ground by slabs or beams acting in flexure, i.e. the bridges obtain their load-carrying resistance from the ability of the slabs and beams to resist bending moments and shear forces. Only for the very shortest spans is it possible to adopt a slab without any form of beam. This type of bridge will thus be referred to generally as a girder bridge.

My Site Information during training( procedure): 

My Site Information during training( procedure) Survey - existing ground level and site details. Soil investigation - at least one bore-hole for each support position to determine safe bearing pressure, aggressive conditions and predict settlement. Mining - details of old working and future seams. canal Board – navigation requirements, maximum flood levels and scour problems around foundations. . Statutory Undertakers – diversion of existing services, provision for future services in the deck.

Site Information: 

Site Information Planning Authorities – normally concerned with aesthetic appeal and the effect on local amenities. Road Geometry – details of horizontal and vertical alignment together with the road cross-section. Design Standards – design live loading, visibility distances, headroom standards and horizontal clearances. Time – the time for design and the phasing of construction in relation to other work. Atmospheric Conditions – an aggressive environment may involve high maintenance costs for steel construction and special precautions in the detailed specification.

Conceptual Choice Considerations: 

Conceptual Choice Considerations Initial conceptual choice should take account of: clearance requirements and the avoidance of impact damage type & magnitude of loading topography and geology of the site possible erection methods local skills and materials future inspection and maintenance aesthetic and environmental aspects

Factors Affecting Conceptual Choice: 

Factors Affecting Conceptual Choice The functional considerations that have greatest influence on conceptual choice are: The clearance requirements (both vertically and horizontally) and avoidance of impact The type and magnitude of the loading to be carried The topography and geology of the site

Clearance Requirements: 

Clearance Requirements This bridges is designed to ensure, as far as is possible, that they are not struck by vehicles, vessels which may pass through them. This requirement is normally met by specifying minimum clearances. It must be remembered that designed values must take into account deflections due to any loading that may occur on the bridge structure. Clearance requirements may thus determine the span of a bridge and also have a significant bearing on the construction depth. Whilst the requirements will not normally determine precisely the type of bridge, it may well eliminate some possibilities.

Clearance Requirements: 

Clearance Requirements this bridge over a highway would be expected to have a minimum vertical clearance of about 5,3 metres; even this may not protect it from accidental impact In addition, pier positions was desiged such that the likelihood of impact from errant vehicles is minimised, both to protect the pier and the vehicle itself. This requirement was usually achieved by setting the pier back a reasonable distance from the edge of the carriageway.

Clearance Requirements: 

Clearance Requirements Navigation authorities specified clearances over canal, to allow not only for the mast height and width of vessels below the bridge, but also for particular requirements for piers in the waterway (or on a flood plain) to avoid excessive flow velocity and scour of river banks. In considering vertical clearance, a designer must bear in mind the problems of attaining them. The approach gradient for a bridge should not normally exceed about 4%

Loading: 

Loading The type and magnitude of loading has a significant bearing on the form of bridge. Highway loading by its nature is impossible to determine exactly, either in disposition or in magnitude. A bridge requires a deck on which the traffic can run and (unless the span is so short that a simple slab is adequate to span between abutments) the deck must be strong enough to distribute the loading to the main girders.

Topography & Geology of Bridge Site: 

Topography & Geology of Bridge Site The overall topography of the site will probably determine the line of the road. Not infrequently this may mean that bridges will have to cross other road and canal at a substantial angle, resulting in skew spans. Generally, the bridge site is fixed by the geometry of the obstacle and local terrain. The road may be on a curve; whilst it is possible to curve a bridge to follow this, it is frequently expensive and structurally inefficient, usually dictating the use of torsionally stiff girders even for short spans. If the curve is slight, it may be preferable to construct the bridge as a series of straight spans. Poor foundation conditions will favour fewer foundations and hence longer spans. A balance has to be found between the cost of foundations and superstructure to minimise the total cost.

Other Factors: 

Other Factors Method of Erection It has long been appreciated that a designer must consider at the design stage the method by which a bridge will be erected. Indeed it is not infrequently the case that such consideration should be made even at the time of conceptual choice, since it can happen that the superficially most attractive design is impossible to erect in a particular location. For example, a design that relies on being erected in large pieces (such as a major box girder), may be ruled out because of the impossibility of transporting such pieces to a remote site with inadequate access roads.

Other Factors: 

Other Factors Local Constructional Skills and Materials A bridge should be suited to local technology. It is not sensible to specify a sophisticated design if all the material and labour has to be imported. Future Inspection and Maintenance Lack of attention to future maintenance both at the conceptual design and the detailed design stages would results in many bridges, otherwise satisfactory, have deteriorated because of difficulty in inspection and maintenance. It is particularly important that in locations where access is difficult (either physically or because it would cause disruption of services) details which deteriorate should be avoided as far as possible. This will be considered further in various respects, for example whether a bridge should be a series of simple spans or should be continuous.

Other Factors: 

Other Factors Aesthetic and Environmental Aspects The appearance of bridges has in recent years become a matter of considerable importance. Frequently, a scheme takes a road or railway through an area of great natural beauty and it is important that any structures are in keeping with these surroundings and do not adversely affect them. For example, it is commonly accepted that a bridge is more aesthetically pleasing with an odd number of spans than an even number. In addition, a degree of deepening at piers can add to the attraction. The 3-span structures are more attractive than the two span ones. Hence, unless there are other contra-indications, the conceptual choice should probably tend towards a 3-span solution.

Detailed Design Considerations: 

Detailed Design Considerations The design development needs to make the correct choices for: deck structure layout i.e. spans and structural arrangements continuous or simple construction proportions, i.e. span/depth ratios reducing fabrication labour to a minimum design for ease of construction

Basic Components of a Bridge: 

Basic Components of a Bridge The two basic parts are: Substructure - includes the piers, the abutments and the foundations. Superstructure - consists of the deck structure itself, which support the direct loads due to traffic and all the other permanent and variable leads to which the structure is subjected. The connection between the substructure and the superstructure is usually made through bearings. However, rigid connections between the piers (and sometimes the abutments) may be adopted, particularly in frame bridges with tall (flexible) piers.

Substructure : Piers: 

Substructure : Piers Piers are of two basic types: Column piers - Concrete column piers may have a solid cross-section, or a box section may be the shape chosen for the cross-section for structural and aesthetic reasons. Wall piers - generally less economical and less pleasing from an aesthetic point of view. They are very often adopted in cases where particular conditions exist, e.g. piers in rivers with significant hydrodynamic actions or in bridges with tall piers where box sections are adopted.

Types of Bridge Piers often used in p.w.d in india: 

Types of Bridge Piers often used in p.w.d in india

Bridge Deck: 

Bridge Deck The principal function of a bridge deck is to provide support to local vertical loads (from highway traffic, railway or pedestrians) and transmit these loads to the primary superstructure of the bridge. As a result of its function, the deck will be continuous along the bridge span and (apart from some railway bridges) continuous across the span. As a result of this continuity, it will act as a plate (isotropic or orthotropic depending on construction) to support local patch loads.