STEEL CONNECTIONS

The steel structures are constructed by properly connecting the available standard sections. The connections are an important part of steel structure and are designed more conventionally than any individual members. There is a discrepancy between the actual behaviour and the analysis of steel structure is large, therefore the connections are complex to analyse and design. When the structural member fails in case of overloading then there is a general practice to prefer the individual member rather than the connections, therefore this kind of practice affects many structural members. The cost of structural steel consists of major portion of connections and that is the reason primary importance should be given to the design of connections for safety and economy of structure.

The connections are generally provided in the following cases:

• When there is the requirement to cater the heavy load and long span then the built-up sections are to be provided. In this case, this section should be connected together to get a good section.
• In case of longer span, the length of standard section needs to be connected with other section. In this case to connect the multiple sections proper design of connections are important.
• The different members need to be connected at the end (for example secondary beams to be connected to primary beam, column, footings, etc).

The classification in the connections provided in the steel structure is as follows:

• Riveted connections
• Bolted connections
• Welded connections
• Pinned connections

Shear and bending moment diagrams

Shear and bending moment diagrams are analytical tools used in conjunction with structural analysis to help perform structural design by determining the value of shear force and bending moment at a given point of a structural element such as a beam.

 Sedimentation 

Sedimentation is also called clarification. Sedimentation removes settleable solids by gravity. Water moves slowly through the sedimentation tank/basin with a minimum of turbulence at entry and exit points with minimum short-circuiting. Sludge accumulates at the bottom of the tank/basin. Typical tanks or basins used in sedimentation include conventional rectangular basin, conventional center-feed basins, peripheral-feed basin, and spiral-flow basins.

In conventional treatment plants, the amount of detention time required for settling can vary from 2 to 6 hours. Detention time should be based on the total filter capacity when the filters are passing 2 gpm per square foot of superficial sand area. For plants with higher filter rates, the detention time is based on the filter rate of 3 to 4 gpm per square foot of sand area. The time requirement is dependent on the weight of the floc, the temperature of the water, and how still the basin is. Effective sedimentation is critical to optimize pathogen removal and to enhance filter effluent quality.

A number of conditions affect sedimentation: 1) uniformity of flow of water through the basin, 2)stratification of water due to difference in temperature between water entering and water already in the basin, 3) release of gases that may collect in small bubbles on suspended solids, causing them to rise and float as scum rather than settle as sludge, 4) disintegration of previously formed floc, and 5) size and density of the floc.

Sedimentation basins are designed to provide idle conditions, such as a uniform low velocity, proper detention time, no short circuits, and no surface turbulence to the flocculated water for an effective sedimentation. Velocity varies from 1 to 3 ft/minute. Detention time (the time it takes to fill the tank) ranges from 1 to 6 hours, depending on the design of the basin. A short circuit is the flowing of incoming water through the tank, without proper stratification of the water in the basin. Short circuits are generally caused by the stratification of the water in the basin and are common during summer and winter. There should be a proper mixing and baffling of the influent with the water in the basin. Surface turbulence is due to wind action and movements of the equipment. An adequate wind-breaking height of the basin wall above the water surface and the proper maintenance of equipment are very helpful.

Sediments settle to the bottom of the basin, and the effluent is strained from the top. These basins have inlet and outlet valves for flow control, and the bottom floor slopes to a hopper (pit) for the sludge collection. Sedimentation basins are classified as primary and final sedimentation basins, according to their functions. A primary sedimentation basin receives the flocculated water and discharges it to the final sedimentation basin.

 GPS 

GPS is a system of 30+ navigation satellites circling Earth. We know where they are because they constantly send out signals. A GPS receiver in your phone listens for these signals. Once the receiver calculates its distance from four or more GPS satellites, it can figure out where you are.

 
DEMOLITION OF BUILDINGS

Demolition of buildings and structures are required for various reasons. Demolition methods and processes for buildings and other structures are described. As we know that every design of a building or a structure has a lifespan know as design life. The building is designed considering a span of life, say 80 -100 years. When this design life of the building is over, the structure is not safe for living and neighboring buildings. There can be more reasons for demolition of a building, old structures are to be replaced by new ones. The structure lost its stability or having any structural damage. Small structures are demolished to build big structures etc. Definitions Demolition: The word demolition means destruction, breaking down or removal. Demolition of building is the process of dismantling or destroying of a structure after its life of serviceability by pre-planned and controlled methods. Implosion: When explosives are used in the demolition of a building, it is termed as Implosion.

 

HYDRAULIC JUMP

A hydraulic jump is a phenomenon in the science of hydraulics which is frequently observed in open channel flow such as rivers and spillways. When liquid at high velocity discharges into a zone of lower velocity, a rather abrupt rise occurs in the liquid surface. The rapidly flowing liquid is abruptly slowed and increases in height, converting some of the flow's initial kinetic energy into an increase in potential energy, with some energy irreversibly lost through turbulence to heat. In an open channel flow, this manifests as the fast flow rapidly slowing and piling up on top of itself similar to how a shockwave forms. The phenomenon is dependent upon the initial fluid speed. If the initial speed of the fluid is below the critical speed, then no jump is possible. For initial flow speeds which are not significantly above the critical speed, the transition appears as an undulating wave. As the initial flow speed increases further, the transition becomes more abrupt, until at high enough speeds, the transition front will break and curl back upon itself. When this happens, the jump can be accompanied by violent turbulence, eddying, air entrainment, and surface undulations, or waves.
 
There are two main manifestations of hydraulic jumps and historically different terminology has been used for each. However, the mechanisms behind them are similar because they are simply variations of each other seen from different frames of reference, and so the physics and analysis techniques can be used for both types.
 
The different manifestations are:
 
The stationary hydraulic jump – rapidly flowing water transitions in a stationary jump to slowly moving water
The tidal bore – a wall or undulating wave of water moves upstream against water flowing downstream. If one considers a frame of reference which moves along with the wave front, then the wave front is stationary relative to the frame and has the same essential behavior as the stationary jump.

 Statically Determinate and indeterminate Beams

Structure is generally classified into two categories as Determinate and Indeterminate Structures or Redundant Structures for analysis of structures to find forces based on criteria discussed below. Structure is an assemblage of a number of components like slabs, beams, columns, walls, foundations and so on, which remains in equilibrium. It has to satisfy the fundamental criteria of strength, stiffness, economy, durability and compatibility, for its existence. Any structure is designed for the stress resultants of bending moment, shear force, deflection, torsional stresses, and axial stresses. If these moments, shears and stresses are evaluated at various critical sections, then based on these, the proportioning can be done. Evaluation of these stresses, moments and forces and plotting them for that structural component is known as analysis. Determination of dimensions for these components of these stresses and proportioning is known as design.

Determinate structures are analysed just by the use of basic equilibrium equations. By this analysis, the unknown reactions are found for the further determination of stresses. Redundant or indeterminate structures are not capable of being analysed by mere use of basic equilibrium equations. Along with the basic equilibrium equations, some extra conditions are required to be used like compatibility conditions of deformations etc to get the unknown reactions for drawing bending moment and shear force diagrams. Example of determinate structures are: simply supported beams, cantilever beams, single and double overhanging beams, three hinged arches, etc. Examples of indeterminate structures are: fixed beams, continuous beams, fixed arches, two hinged arches, portals, multistoried frames, etc. Special methods like strain energy method, slope deflection method, moment distribution method, column analogy method, virtual work method, matrix methods, etc are used for the analysis of redundant structures.
 
Indeterminate Structures: A structure is termed as statically indeterminate, if it can not be analysed from principles of statics alone, i.e. clip_image001. A statically indeterminate structure may be classified as:
Externally indeterminate, (example: continuous beams and frames)
Internally indeterminate, (example: trusses )
Both externally and internally indeterminate, (example: trussed beams, continuous trusses )