Various types of Design Loads on Bridges, Highway & Rail Bridge

While going to deign any bridge, the tasks like computation of Design Loads and loading bridge model are very important. Given below, some crucial loads which should be taken into consideration at the time of creating the design of a bridge.

Dead Load - “Gravity loading because of structural parts of bridge”

Dead load comprises of permanent gravity forces because of structural Elements. It is basically measured as the product of volume and material density. Normally, self-weight is employed in the analysis model with the self-weight option of the analysis software. This makes the calculation step simple.

Superimposed Dead Load - “Dead Gravity loading because of non-structural parts of bridge”

Superimposed dead loads stand for gravity loads that include other permanent items ranging from parapets and road surfacing and other non-structural and architectural attachments to the bridge. Such items last long but should have been modified during the lifetime of the structure. It has similarity with self-weight and it is measured as the product of volume and material density.

The most crucial item of superimposed dead load belongs to the road pavement or surfacing. It is not atypical for road pavements to become gradually thicker over a number of years since every new surfacing is just placed on top of the one before it. Therefore, specifically high load factor is employed to road pavement.

Imposed traffic Loading - “Because of road or rail vehicles”

Imposed traffic loads contain those forces which are produced with road or rail vehicles on the bridge. Bridge traffic can be vehicular, rail or pedestrian/cycle or genuinely any combination of these. The type and strength of the design vehicle alters on the basis of the design code. As for instance, HL-93 is used in AASHTO design code.

Bridge traffic loading is frequently monitored by trucks whose weights significantly surpass the maximum legal. Bridge traffic loading is used with the notional lanes which do not depend on the actual lanes. Eurocode normal loading comprises of invariable loading and a pair of four wheels in a single lane.

To examine the dynamic effects of traffic, the vehicular loads are multiplied with an impact factor frequently.

Pedestrian and cycle track - “Gravity loading because of non-vehicular traffic”

Bridge codes normally indicate a basic intensity for pedestrian loading. Again intensity is based on the design code, it is 5 kN/m2 in the Eurocode and the British standard and 4 kN/m2 in the American code.

To get more detail information, go through the following link. engineeringcivil.org

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Published By

Rajib Dey

www.constructioncost.co

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How to design any one way simply supported slab

In this construction video tutorial, you will learn how to create the design of one way slab (simply supported slab) that is standing on the masonry wall.

You will also gather information on all checks for making design of the slab.

The requirements and materials of the slab are given below :-

Clear span = 3m
Live load = 4000 N/m2
M20 concrete and fe 415 steel are used here.

The calculation is made on the following dimensions :-

A bearing of 120 mm is provided at each end. The distance among centers of bearing = 3+0.12 = 3.12 m

Necessary effective depth = Span/20 x modification factor
= 3120/20 x 1.40 = 112 mm

The bars with 8 mm diameter are arranged with clear cover of 15 mm.
Effective cover = 15 + 4 = 19 mm

Overall necessary depth = 112 + 19 = 131 mm

It is necessary to arrange an overall depth of 135 mm

So, effective depth = 135-19 = 116 mm

The Dead load of the slab will be calculated as follow :-
25 x 135 = 3375 N/m2 (floor finished with C20 mm).

Live load = 4000 N/m2
Therefore, total load = 7855 N/m2
Factor load = Wµ = 1.50 x 7855 = 11782.5 N/m2

To get more details, go through the following video tutorial.

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Published By

Rajib Dey

www.constructioncost.co

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Common causes of downfalls of Dam Structures

A dam is a block across flowing water that opposes, directs or slows down the flow, often creating a store, lake or captivities. Most dams have a section named a spillway or weir over or through which the water passes and have some hydroelectric power generation systems installed.

Dams are like ‘installations containing dangerous forces’ due to the huge impact of a possible destruction on the normal population and the environment.

Generally dam failures are happen rarely but can do huge damage and loss of life, it happens as the dam structures are constrained to horizontal loading from the water head behind. The pressure comes from the water to the dam materials such as the adjoining geology and size of the reservoir which are very new in the case of dam structures.

Common reasons of downfalls of Dam Structures: The most known reason of the downfall of the dam structures is overtopping which is happen either for exceeding that is something concerned with the design of the spillway.

• Overtopping: It is happen when water slopping over the top of a dam and become a reason of dam failure. The two major factors of the overtopping failure are one id created due to surface elevation exceeds the total structural elevation profile and the other one is the over washes of the waves.
• Foundation defects and Slope instability: Foundation defects with settlement and slope instability causes most of the dam failures.

• Cracking: happens by the movements like the natural setting of a dam.
• Water Violating.
• Piping.
• Subsidence and the movement of the foundation.
• Uplift form the ground and sliding of the structure.
• Variation in temperature.
• Dynamic blasting in the nearby areas.

• Seismic load action.
• Wave action on the structure and weak energy absorption.
• Higher amount of silting.
• Loosing shear capacity of the concrete.

Reasons of downfalls of Earth Dam Structures: In case of earth dam, that unique materials that are used for the structure is made from the earth materials is nearby the side and makes the structure to be mixed in nature showing different properties in different conditions of weather and bring variations in the physical properties. There are other reasons of the earth dam failure are: insufficient spillways, piping, failure of the structure etc. and many more.

Reasons of downfalls of Gravity Dam Structures: Gravity dams are made from concrete and masonry and the major causes of failures of these structures are: soil erosion, failed construction joints, poor material etc.

Reasons of downfalls of Arch Dam Structures: This dam is different as it has plane stresses existing and thrust and these factors are caused for the design of the structure and completely dependent on the conditions of soil and rock. The failure happens for lack of structure, penstock vibration and insufficient grouting action.

Reasons of downfalls of Buttress Dam Structures: They have the horizontal forces transferred to the rock foundation and carried out by water pressure which is analyzed for the sliding and overturning failure of dam structure. The main reasons of failure are: alternate freeze and thraw cycles, masonry etc.

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Published By
Rajib Dey
www.constructioncost.co
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