Benefits of piers constructed monolithically in bridge

When integral bridge, piers are constructed monolithically with the bridge deck, the following benefits are obtained :-

Bearing replacement cost is directly associated with the maintenance of bridges and it creates problem for the contractors. With integral bridge systems, it can be bypassed. In design standpoint, bearing replacement involves extra stresses and requirement of diaphragms in transverse design.

Movement of the bridge deck is obtained with the bending deformation of long and slender piers. Thus, it reduces the construction cost of bearings with the use of monolithic construction among bridge deck and piers.

Besides, it is less important to give extra effort to create design for drainage details and get bearing replacement. Alternatively, in maintenance perspective considerable cost and time savings can be gained with integrated bridge construction rather than applying bearings as bridge articulation.

Monolithic construction comprises of the shortest useful Euler buckling length for piers since they provide fixed supports at the interface among bridge deck and piers.

Other Factors: In two span integral bridges, temperature, creep and shrinkage, and other loads that provide longitudinal forces like seismic forces which create crucial design challenges.

These forces produce supplementary moments on the central pier increasing the demand. It requires innovative solutions in the design, ranging from implementation of arch systems to facilitate the bridge to breath up and down because of thermal actions. Unsettled soil conditions and seismic zones create the design challenges. Integrated Bridge design is an expert area in the design of bridges.

Note: In monolithic construction the piers are attached with the bridge decks irrespective of any joints and bearings.



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Rajib Dey
www.constructioncost.co
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Different types of loads for designing bridge structures

While designing bridge structure, different types of loads are taken into consideration. The protection of the bridge construction throughout its use under all situations is mainly dependent on those loads and their combinations.

The role of design loads is very important for creating exact design of bridge. Given below, various types of design loads operating on bridges :-

1. Dead load
2. Live load
3. Impact load
4. Wind load
5. Longitudinal forces
6. Centrifugal forces
7. Buoyancy effect
8. Effect of water current
9. Thermal effects
10. Deformation and horizontal effects
11. Erection stresses
12. Seismic loads

1. Dead Load: The dead load stands for a self-weight of the bridge components. The various components of bridge range from deck slab, wearing coat, railings, parapet, stiffeners and other utilities. While creating the design of bridge, it is considered as the first computable design load.

2. Live Load: The live load on the bridge belongs to the moving load on the bridge all through its length. The examples of moving loads are vehicles, Pedestrians etc. But, it is complicated to choose one vehicle or a group of vehicles to design a safe bridge.

IRC suggested some fictional vehicles as live loads which will provide secure results in anticipation of any type of vehicle moving on the bridge. The vehicle loadings are classified as follow :-

• IRC class AA loading
• IRC class A loading
• IRC class B loading

IRC Class AA Loading: This type of loading is applicable to create the design of new bridge particularly heavy loading bridges ranging from bridges on highways, in cities, industrial areas etc. In class AA loading normally the following types of vehicles are taken into consideration :-

• Tracked type
• Wheeled type

IRC Class A Loading: This type of loading is applicable for creating the design of all permanent bridges. It is treated as standard live load of bridge. While designing a bridge with class AA type loading, then it should be examined for class A loading also.

IRC Class B Loading: This type of loading is applicable for making design of temporary bridges like Timber Bridge etc. It is treated as light loading.

3. Impact Loads: The Impact load on bridge occurs because of sudden loads which are produced when the vehicle is moving on the bridge. When the wheel is in motion, the live load will alter occasionally from one wheel to another that produces the impact load on bridge.

The impact loads on bridges are assessed with an impact factor. Impact factor stands for a multiplying factor that is based on several factors like weight of vehicle, span of bridge, velocity of vehicle etc.

To get more details about other types of loads, go through the following link theconstructor.org



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Published By
Rajib Dey
www.constructioncost.co
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Bridge pile cap construction details

This construction video is based on pile cap construction process for building up a bridge. The video is specifically designed for bridge engineer.

The video throws light on the following topics :-

a. Pile Head Breaking
b. Granular laying
c. CC work
d. Rebar Fabrication

The construction method of bridge is segregated into two parts :-

Substructure (pile foundation, pile cap, pier, pier cap)

Superstructure (bearing, girder, slab)

Definition of pile cap: It belongs to a structural member that is positioned and generally attached on the top of a pile or a group of pier to transfer the loads into the pile or group of piles to relate them into a bent.

Functions of pile cap
To disperse a single load evenly over the pile group as well as over a larger area of bearing potential.

To laterally strengthen separate piles and enhance complete durability of the group.
To arrange the required combined resistance to stress organized by the super structure and ground movement.
To transfer the loads of the building to the foundations and the ground soil layers despite the loads are vertical or inclined.
To facilitate the column or superstructure to stay on a consistent and solid core foundation rather than staying directly on ground.

To learn the detail pile cap construction process for a bridge, go through the following video tutorial.

Video Source: Construction Methodology

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Published By
Rajib Dey
www.constructioncost.co
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How to calculate hinged support, normal thrust and shear of a three hinged circular arch

This construction video tutorial is based structural analysis. You will learn how to make calculation of reaction at the support as well as normal thrust and shear for three hinged circular arch.

This video is presented by renowned engineer Mr. Parag Pal.

Three hinged system:

a. A three hinged system comprises of two plates, attached collectively with a hinge containing two hinged supports A and B resting on the ground.
b. When the plates 1 and 2 comprises of curved bars, the system is known as a three-hinged arch.
c. The distance 1 among the centers of the hinges at the support is known as the span of arch.
d. When distance f from the center of the crown hinge to the straight line going through the former two is defined as its rise.

The reactions of a three hinged arch will be completely established with four parameters, as for example, the amounts of reaction Ha, Hb, Va, and Vb.

So, a three hinged system is always statically determinate.

Benefits:

a. The bending moments and shears operative over cross sections of three hinged arches are significantly smaller as compared to the subsequent stresses in a simple beam covering the equivalent span and bearing the same load. So, three hinged arches are inexpensive relating to ordinary beams, specifically for large span structures.

b. Calculations are very simple as compared to other type of arches.
c. No bending moments are generated at the abutments and the crown since hinges cannot withstand moments.
d. Differential settlements of the supports do not impact stresses, since the pines or hinges allow the arch to assume the slightly different shape consequent upon settlement.

e. The pin joints allow the arch to modify itself to expansions and contractions because of alterations in temperature.

In this video, solution is given to the following problem: A three-hinged circular arch hinged at the springing and crown points contain a span of 40 m and a central rise of 8 m. It bears a consistently distributed load 20 kN/m over the left-half of the span collectively along with a concentrated load of 100 kN at the right quarter span point.

Determine the supports, normal thrust and shear at a section 10 m from left support.

To get the solution, go through the following video tutorial.

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Published By
Rajib Dey
www.constructioncost.co
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Types of bridge and bridge components

Bridges are generally made of various types and materials and an essential part of transportation.

Bridge: It is mainly a structure which is built to stretch physical obstacles without closing the original way underneath like a body of water, valley or road etc. to make a passage over the hurdle.

There are lots of different designs from which each of them can be served for a distinct purpose and can be applied in different situations. The designs of the bridges differ as per the function of the bridge, the nature of the soil where the bridge has constructed and anchored, the material used to make it and the available funds for it.

There are mainly 4 types of bridges such as, 1) Bridges by Structure, 2) Fixed or Movable Bridges, 3) Types by Use and 4) types of Materials.

Bridges by Structure:

1. Arch bridges: The bridges use arch as a main structural element and also made with one or more articulations depended on the kind of load and stress forces endured. Ex: - “Old Bridge” in Mostar, “Bosnia and Herzegovina” and the “Hell Gate Bridge” in New York.

2. Beam bridges: They are very basic type of bridges which are supported by many beams of various shapes and sizes like inclined or V shaped. Ex: - “Lake Pontchartrain Causeway” in Southern Louisiana.

3. Truss bridges: They mainly use diagonal mesh of posts above the bridge and two most common designs are the King posts and queen posts.

4. Cantilever bridges: They are like the arch bridges in appearance but support their load through the diagonal bracing than vertical bracing and often use truss formation both in the below and the above the bridge. Ex: - “Queensboro Bridge” in New York City.

5. Tied arch bridges: Same appearance of the arch bridges but transfer weight of the bride and traffic load on the upper chord that is connected at the bottom cords in bridge foundation and these types of bridges are often called bowstring arches or bridges.

6. Suspension bridges: These kinds of bridges generally use ropes or cables from the vertical suspender for holding the weight of bridge deck and traffic. Ex: - “Golden Gate Bridge” in San Francisco.

7. Cable-stayed bridges: They use deck cables which are straightly connected to one or more vertical columns as cables generally connected to columns in two ways- harp design and fan design.

Fixed or movable types of bridges:

1. Fixed: Most of the bridges in this world are fixed and have no movable parts for providing higher clearance for river or sea transportation which flows below them. These bridges are mainly designed for staying in one place till their demolishing.
2. Temporary bridges: These bridges are made of modular basic objects which can be moved by medium or light machinery and used in military engineering or in circumstances as in time of fixing or repairing.
3. Moveable bridges: Powered by electricity and have moveable decks also.

Video Source: Sami Ullah Stanikzai

Types by use:

1. Car traffic: They are usually very common and have two or more than two lanes which are designed for carrying car and truck traffic of various depths.
2. Pedestrian bridges: They are generally found in the urban environments where car transportation way is through the soils of rough mountains, forests etc.
3. Double-decked bridges: They are naturally built to maintain as better as the traffic movement can be flowed across bodies of water or rough land. They often have large amount of car lanes and sometimes have the dedicated areas for train tracks.
4. Train bridges: Especially made for carrying one or more than one lanes of train tracks.
5. Pipelines: They can carry water, air, gas and communication cables in the water or remote lands.
6. Viaducts: They are old-fashioned structures which are created for carrying water in the prosperous areas to dry cities.
7. Commercial bridges: Modern bridges are now built as a decoration to the commercial buildings like restaurants and shops.

Types by materials: Natural materials like wood, stone, concrete and steel and some other advanced materials.

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Published By
Rajib Dey
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Ring 3.0 – A powerful software for bridge analysis and masonry design

LimitState Ltd has developed RING, a powerful construction program for bridge analysis and masonry design.

The most updated version is RING 3.0. The newest version can be used for analyzing masonry arch bridges. The software is mostly suitable for structural engineers.

The software provides the following advantages :-

• Analyze single or multi-span bridges without having fixed upper limit on the permissible number of spans
• Automatically determine the critical failure mode although:
o only a single span is associated
o sliding is involved
modelling multi-ring arch bridges
• Determine and resolve numerous multiple load cases
• Automatically find out 'passive' pressures - analyze deep and multi-span arch issues with ease
• Model the presence of arch backing material
• User-friendly wizard system facilitate simple and rapid model definition
• Modern, uncomplicated interface supported with an collaborating modeling environment

Extensive library comprises of standard road and rail vehicles
• Property editor facilitates fast querying and adjustment of model properties
• 3D graphical output for superior perception
• Automatic report creation

• User-accountable arch and backfill profiles
• User-accountable separate block weights, masonry strength, mortar loss etc.

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Rajib Dey

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How bridge works to sustain various loads

This construction article focuses on uses and types of bridges.

How bridges balance forces
Things are moved through forces, but they also retain them stagnant. A bridge remains stand steels as all the forces operating on it are correctly in balance. In a nutshell, bridge designers can be described as force balancers.

A bridge extents over a river, valley, sea, or road. There is no direct support under the enormous deck (the primary horizontal platform) of a bridge. If the bridge is lengthier, it becomes heavy and bears lots of weight. So, the chance for collapsing is increased. Bridges can sometime collapse, but most sustain securely for a prolonged period as it cautiously balance two primary types of forces known as compression (a pushing or compressing force, operating internal) and tension (a pulling or stretching force, operating external), by dispersing the load toward abutments (the supports at each side) and piers (one or more supports in the middle). There exist different types of bridges, substantially all of them function by balancing compressive forces in some areas with tensile forces somewhere else, so there does not exist universal force to induce motion and provide damage.

Carrying loads
At the time of unloading, a bridge has to provide support to its own weight (the dead load), therefore the tension and compression in its structure become really static forces (ones that don't give rise to movement) that is adjusted slightly from hour to hour or day to day. Though, by characterization bridges bear fluctuating amounts of weight (the live load) from things like railroad trains, cars, or people, which can significantly raise the ordinary tensile or compressive forces. Rail bridges, as for instance, bend and flex each time when an overweight train passes over them and then "relax" over again once the load has elapsed.

To read the complete article, go through the following link.
www.explainthatstuff.com

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Published By

Rajib Dey

www.constructioncost.co

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