Bracing system is one such structural system that forms associate integral a part of the frame. Such a structure has to be analyzed before effective arrangement of bracing. ETABS computer code is employed to get the planning of frames and bracing systems with the smallest amount weight and applicable steel section choice for beams, columns and bracing members from the quality set of steel sections. A 3 dimensional structure is enamored four horizontal bays of dimension four meters, and twenty stories is enamored structure height of 3m. The beams and columns are designed to resist dead and loading solely. Wind load and Earthquake masses are taken by bracing. The bracings are provided solely on the peripheral columns. Most of the four bracings are employed in a structure for economic functions. Bracing may be a extremely economical and economical methodology to laterally stiffen the frame structures against wind masses. A braced bent consists of usual columns and girders whose primary purpose is to support the gravity loading, and diagonal bracing members that are connected so that all the members form a vertical cantilever truss to resist the horizontal forces. Bracing is economical as a result of the diagonals add axial stress and thus necessitate minimum member sizes in providing the stiffness and strength against horizontal shear. There are 2 varieties of bracing systems 1) homo centric Bracing System and 2) Eccentric Bracing System. The steel braces are typically placed in vertically aligned spans. This method permits to getting an excellent increase of stiffness with a marginal intercalary weight. 1) homo -centric bracings increase the lateral stiffness of the frame therefore will increase the natural frequency and conjointly typically decreases the lateral structure drift. However, increase within the stiffness could attract a bigger inertia force because of earthquake. Further, whereas the bracings decrease the bending moments and shear forces in columns and that they increase the axial compression within the columns to that they’re connected. 2) Eccentric Bracings cut back the lateral stiffness of the system and improve the energy dissipation capability. The lateral stiffness of the system depends upon the flexural stiffness property of the beams and columns, therefore reducing the lateral stiffness of the frame. The vertical part of the bracing forces because of earthquake causes lateral focused load on the beams at the purpose of association of the eccentric bracing, as a result of lateral loading on a building is reversible, braces are going to be subjected successively to each tension and compression, consequently, they’re typically designed for the additional rigorous case of compression. For this reason, bracing systems with shorter braces, for instance K bracing, could also be most popular to the total diagonal varieties. As associate exception to planning braces for compression, the braces within the double diagonal is meant to hold in tension the total shear in panel. a big advantage of the absolutely triangulated bracing varieties is that the girders moments and shears are freelance of the lateral loading on the structural designing course in kerala. Consequently, the ground framing, that during this case, is meant for gravity loading solely, will be repetitive throughout the peak of the structure with obvious economy within the style and construction. The role of internet members in resisting shear will be incontestable by following the trail of the horizontal shear down the braced bent. The conception of mistreatment steel bracing is one in every of the advantageous ideas which might be accustomed to strengthen or retrofit the present structures. The lateral structure displacements of the building are greatly reduced by the utilization of single diagonal bracings organized as diamond form in third and fourth bay compared to homo- centric (X) bracing and eccentric (V) bracing system.
Manganese is a major alloying element, has complex interactions with carbon and is used to control inclusions. Manganese is beneficial to surface quality in all carbon ranges with the exception of rimmed steels and is particularly beneficial in high-sulfur steels. Manganese provides lesser strength and hardness in comparison to carbon. The increase depends on the carbon content – higher-carbon steels being affected more by manganese. Higher-manganese steels decrease ductility and weldability (but to a lesser extent than carbon). Manganese also increases the rate of carbon penetration during carburizing.
The effects of manganese can be summarized as.1. Lowers the temperature at which austenite begins to decompose 2. Extends the metastable austenitic region and delays the commencement of all the austenite decomposition reactions 3. Favors the formation of lower bainite and suppresses the upper bainite reaction on isothermal transformation 4. Is the most effective alloying addition for lowering the martensite-start (MS) temperature 5.Favors the formation of e-martensite 6.Has little effect on the strength of martensite and on the volume change from austenite to martensite 7. Has little or no solution-hardening effect in austenite and between 30–40 MN/m2 per wt. % in ferrite (by lowering the stacking-fault energy of austenite, manganese increases the work-hardening rate) 8. By lowering the MS temperature, manganese prevents the deleterious effects of auto tempering 9. Lowers the transformation temperature, causing substantial grain refinement 10. In general, lowers the tough-to-brittle impact transition temperature (due to its grain-refinement action) 11. Increases the propensity for weld cracking due to the effect on hardenability. The severity of its influence depends to a great extent on the type of steel and the welding techniques. 12. Does not increase the susceptibility of the steel to delayed fracture due to hydrogen absorption 13. Improves the fatigue limit 14. Reduces the number of cycles to failure under high strain conditions 15. Forms five carbides (Mn23C5, Mn15C4, Mn3C, Mn5C2 and Mn7C3), the dominant one being Mn3C, which forms a continuous range of solid solutions with Fe3C, thus reducing the solubility of carbon in a-iron 16. Prevents the formation of an embrittling grain-boundary cementite. 17. Suppresses the yield extension in deep-drawing steels by virtue of its grain-refinement effect 18. Suppresses strain aging 19. In combination with nitrogen, has a solid-solution hardening effect and improves high-temperature properties 20. Extends the range of use of low-carbon steels 21. Has a strong influence on the pearlite morphology of high-carbon steels 22. Extends the range of use of high-carbon steels through its grain-refining and pearlite-refining actions 23. Raises strength values in bainitic steels by reducing grain size and increasing dispersion hardening 24. Allows bainitic steels to be produced by air hardening 25. Increases hardenability 26. Slows down the temper reactions in martensite 27. Assists interphase precipitation 28. Improves austemper and martemper properties 29. Increases temper embrittlement unless the carbon content is very low and trace element impurities are minimal 30. In spring steels, promotes ductility and fracture toughness without undue loss in tensile strength 31. Removes the risk of hot shortness and hot cracking when the ratio of manganese to sulfur is greater than 20:1 by forming a higher melting-point eutectic with sulfur than iron sulphide 32. Has a major influence on the anisotropy of toughness in wrought steels due to the ability to deform manganese sulfides during hot working 33. Forms three manganese sulfide morphologies (Type I, II and III) dependent upon the state of oxidation of the steel 34. Enhances free-cutting steels 35. Increases the stability of austenite 36. Has similar atomic size as iron 37. Lowers the stacking-fault energy of austenite (in contrast to alloying element additions such as chromium or nickel) 38. Allows lower solution temperatures for precipitation-hardening treatments in highly alloyed austenite due to increased carbon solubility 39. Forms s intermetallic compounds suitable for precipitation-hardened austenitic steel detailing course in kochi 40. Plays a major role in controlling the precipitation process that occurs during isothermal transformation to austenite 41. Increases the rate of carbon penetration during carburizing 42. Contributes, in combination with nitrogen, to the performance of work hard enable austenitic stainless steels 43. Improves hot corrosion resistance in sulfurous atmospheres 44. Enhances wear-resistance in carbon-containing austenitic steels where the manganese content is between 12-14% 45. Improves response of low-alloy steels to thermomechanical treatments 46. Strengthens certain steels by producing an austenitic structure using manganese-containing compounds 47. Enhances the performance of TRIP steels 48. Promotes Ferro-elastic behavior in appropriate steels 49. Less tendency to segregate within the ingot 50. In general, improves surface quality.
Structural steels are sometimes made by rolling steel solid from the steel making method when reheating it to a temperature higher than 850°C. Rolling consists of passing the steel through a series of rolls that kind the solid steel into the form and thickness needed. A big selection of shapes and sizes are presently rolled or out there. The properties of steel for the most part result from the influence of micro structure and grain size the different factors like non-metallic inclusions are vital. The grain size is powerfully influenced by the cooling rate, to a lesser extent by different aspects of warmth treatment and by the presence of little quantities of components like atomic number 41, metallic element and atomic number 13. Thus, the assembly of steel and steel product involves heat and therefore the effects of heating and cooling throughout. The chemical composition of steel is essentially determined once the steel is liquid except for a given chemical content the structure is essentially determined by the speed at that it’s cooled and should be altered by ulterior reheating and cooling below controlled conditions. Carbon steels are for the most part composed of iron with up to one.7% carbon, however the addition of comparatively little quantities of different components greatly influences its behavior and properties. For structural functions it’s fascinating that steel be ductile and weldable, and consequently most structural carbon steels are low-carbon steel with carbon within the vary zero.15 to 0.29% and should embody little quantities of metal, element and copper. the right production of steel structures may be a complicated method involving creating the steel, process it into helpful product, fabricating these product into helpful assemblies or structures by cutting, drilling and fitting, and erection and grouping these parts, assemblies, and structures into buildings or bridges. it’s vital to investigate processes as a result of they’ll have a significant result on the investigated environmental impact of a steel structure, however they ordinarily don’t specify or would like details of exactly however the steel is made, rolled or fashioned. Presently, attachment is maybe the foremost vital method employed in the fabrication and erection of structural steel designing course in kerala work. it’s used terribly extensively to hitch parts to form up members and to hitch members into assemblies and structures. attachment used and done well helps within the production of terribly safe and economical structures as a result of attachment consists of primarily connection steel element to steel element with steel that’s intimately united to each. Corrosion of steel takes place by a fancy chemical science reaction between the steel and atomic number 8 that’s expedited by the presence of wetness. Structural needs further protection and therefore the usual strategies are paint systems or exciting. steel is an environmentally friendly artefact which means less environmental impacts compared with the opposite trendy structural parts. The usage of steel to implement the property criteria from the extraction and mineral processing of raw materials, through the look and construction of buildings to the tip of life is extremely vital for overall property. Steel and concrete bridge structures have similar impacts on the atmosphere. Steel will totally justify its claims to be the best construction material. It’s ability implies that instead of being destroyed to form means for a replacement building with modified use, a steel-framed building will typically be reconfigured for a replacement use, and given an entire vogue by ever-changing its protection. The long span capabilities of steel construction provides clear areas that may be simply reconfigured, providing the prospect of extending a building’s helpful life. At the tip of a building’s helpful life its steel frame may be simply demolished and components of it either re-used or recycled; de-mountability may be designed into a steel building, permitting house owners to arrange for future use on another web site. Steel employed in construction won’t visit lowland as even scrap steel includes a price and could be a very important part within the method of manufacturing new steel. Steel may be recycled which means subsequent re- cyclings do nothing to cut back its qualities; it’s not simply recycled, however multicycled.
Steel and Seismic Design
The different aspects of a seismic design has always been a concern when it comes to the designing of steel structure design course in kerala. A number of strategies are important to the design of structures that will behave adequately in strong earthquakes. The major aspects that are considered are continuity, adequate stiffness and strength, regularity, redundancy etc. Continuity. All of the pieces that comprise a structure must be connected to each other with sufficient strength that when the structure responds to shaking, the pieces don’t pull apart and the structure is able to respond as an integral unit. An important aspect of continuity is having a complete seismic load resisting system so that a force that is applied anywhere in the structure has a means of being transmitted through the structure and to the foundation. In addition to vertical frames, a complete seismic load resisting system must also include horizontal diaphragms to transmit inertial forces to the vertical frames. Stiffness and Strength. Structures must have sufficient stiffness so that the lateral deformations experienced during an earthquake do not result in instability and collapse. Structures must have sufficient lateral and vertical strength such that the forces induced by relatively frequent, low intensity earthquakes do not cause damage and such that rare, high-intensity earthquakes do not strain elements so far beyond their yield points that they lose strength. Regularity. A structure is said to be regular if its configuration is such that its pattern of lateral deformation during response to shaking is relatively uniform throughout its height, without bringing a lot of deformation in small areas of the structure. It is important to avoid excessive twisting of structures because it is difficult to predict the behavior of a structure that twists excessively. It also is important to avoid concentrations of deformations in structures because these concentrated deformations can become very large, leading to extreme local damage in the area of the concentration and a loss of vertical load. Redundancy is important because of the basic design strategy embodied in the building codes, which anticipates that some elements important to resisting lateral forces will be loaded beyond their elastic limits and will sustain damage. If a structure has only a few elements available to resist earthquake-induced forces, when these elements become damaged, the structure may lose its ability to resist further shaking. However, if a large number of seismic load resisting elements are present in a structure, and some become damaged, others may still be available to provide stability for the structure. Defined Yield Mechanisms. The most important strategy is to Design a predetermined yield mechanism. In this approach, which is often termed capacity design, the designer must decide which elements of the structure are going to yield under strong earthquake excitation. In order to sustain yielding without undesirable strength loss elements are detailed . At the same time, all of the other elements of the structure, such as gravity load-carrying beams, columns and their connections, are proportioned so that they are strong enough to withstand the maximum forces and deformations that can be delivered to them by an earthquake, once the intended yield mechanism has been engaged. In essence, the members that are designed to yield act as structural “fuses” and protect other elements of the structure from excessive force. This strategy ensures that critical members important to the vertical stability of the structure and its ability to carry gravity loads are not compromised.
Austenitic unblemished steels have wonderful corrosion resistance, additionally, even thick, hot-rolled primary solid solution chrome steel plates afford wonderful toughness and weldability. As a result of these characteristics, they’re widely used as steel materials for welded structures, in the main in industrial machines and plants. within the design and engineering fields too, there’s little question that SUS304—the commonest primary solid solution unsullied steel—will still be the foremost probably candidate for the applying of unsullied steels, visible of the very fact that SUS304 contains a smart balance of properties, available in varied forms, and has already found several applications. Once properly used, it is free from conspicuous erosion for an extended time and displays better performance as a steel material. In distinction, since SUS304 contains a substantial proportion of nickel (a rare metal), it’s rather more costly than general structural steels and structural steels that are subjected to corrosion-protective treatment (e.g., plated steels). Moreover, the worth of SUS304 is at risk of fluctuations within the prices of raw materials. even if increasing importance is hooked up to LCC, the higher than value structure for SUS304 is associate degree impediment to increasing its application below gift domestic conditions that square measure loath to any increase in initial work price. In distinction, ferritic chrome steel sheet (cold-rolled sheet), that doesn’t contain nickel, has seen its applications in vehicles and residential appliances, etc., speedily dilated. Formerly, hot-rolled ferritic chrome steel detailing course in kochi was thought-about unsuitable as a steel material as a result of its inferior toughness and weldability. The technological progress has helped in reducing impurities, etc., in steel producing and application/forming technology, like fastening, hot-rolled ferritic chrome steel containing less than regarding 11 November metal currently has enough properties needed of structural steels, and thence will be utilized in several applications. The characteristics and future prospects of a hot-rolled ferritic chrome steel developed for discipline structure—are as follows. Carbon and element impurities square measure reduced and also the microstructures of the merchandise and heat-affected zones square measure rendered finer. The deformation characteristic is analogous thereto of general structural steels, because the fixed strength utilized in structural style, identical worth as that of SS400 steel for structural use will be adopted. The matter of inferior toughness of welded joints and inferior fastening workability has been eliminated that has been a drawback of ferritic chrome steel. Since the steel contains a relatively tiny proportion of metal, it’s subject to erosion corrosion in outside environments containing fine particles of ocean salt. However, in standard outside environments, the speed of corrosion growth is very low and thence enough structural sturdiness will be secured for prolongedstruction. This steel has been approved by the minister as fixed below Article thirty seven of the Building Law, in order that it will be utilized in general buildings. Additionally, the steel could be a high-durability steel that meets the best level of sophistication three (durability: regarding a hundred years) within the classification of measures against deterioration as outlined within the Housing Quality Promotion Act. The steel is predicted to search out applications within the design and engineering fields, not solely as a fabric for the body of long-lived housing, however conjointly as a replacement sort of structural chrome steel that helps scale back the load of corrosion-protective treatment applied throughout work or maintenance.
Prefabricated construction could be a new technique and is fascinating for big scale housing programmes. The main aim of prefabrication are :
1) To impact economy in value
2) To boost in quality because the elements is factory-made below controlled conditions.
3) To hurry up construction since no hardening is critical.
4) To use domestically on the market materials with needed characteristics.
5) To use the materials that possess their innate characteristics like lightweight weight,easy workability, thermal insulation and combustibility etc.
Need for Pre fabrication
1. Ready-made structures square measure used for sites that aren’t appropriate for traditional
construction technique like cragged region and additionally once traditional construction
materials aren’t simply offered.
2. PFS facilities may be created at close to a site as is finished to form concrete blocks
used in plane of standard knick.
3. Structures used repeatedly might be standardized .
- Readymade elements are used
- Shuttering and staging is greatly reduced.
- Construction time is reduced and buildings ar completed sooner permitting on
- Earlier come back of the capital invested with.
- On-site construction and congestion is reduced.
- Internal control is easier during a plant mechanical system setting than a construction and Site setting.
- Manufacture is placed wherever expert labour, power materials house and
- Overheads are lower.
- Time spent in weather or dangerous environments at the development web site is minimised
- Materials for staging is keep partially or fully and used
- Accessibility of precise structure and expect acquisition.
- The Time Period is reduced.
- Fewer enlargement joints are needed.
- Interruptions in connecting is omitted.
- Work is completed with a higher technology.
- Less employees are required.
- Careful handling of ready-made elements like concrete panels or steel and
- glass panels is needed.
- Attention must be paid to the strength and corrosion-resistance of the change of integrity of
- prefabricated sections to avoid failure of the joint
- Equally leaks will generate at joints in ready-made elements.
- Transportation prices could also be higher for voluminous ready-made sections than for
- the materials of that they’re created which might usually be packed additional with efficiency.
- Giant ready-made structures need heavy-duty cranes measurement and handling to position in position.
- Giant teams of buildings from identical style of ready-made components tend to
- look drab and monotonous.
- Native Jobs area very less
Prefabricated building parts are utilized for buildings that are factory-made off
site and shipped later to assemble at the ultimate location a number of the unremarkably used
prefabricated building. The materials employed in the ready-made parts area several.
The modern trend is to use concrete steel, treated wood, metal cellular concrete,
light weight concrete, ceramic product etc. whereas selecting the materials for
prefabrication the subsequent special characteristics area unit to be thought-about.
- Thermal insulation property
- simple workability
- sturdiness altogether climatic conditions
- Non combustibility
- Economy in price
- Sound insulation
In the olden days building a house was by the use the bricks, timber, cement, sand, steel and construction mixture etc and to construct the house on site from these materials. In ready-made construction solely the foundations are created during this method. While sections of walls floors and roof ar ready-made structures with windows and door frame enclosed and transported to the positioning upraised in to position by a crane and stewed along. tekla structural steel designing courses in kochi
Developments in the Steel Market
Steel is usually used by the industrial sector and the demand for steel often leads the cycle in industrial production. The demand for steel grew only during the year of 2016, In the initial 10 months of 2016, the monthly consumption indicator for the major steel-consuming economies increased by approximately 1.9% There is an improvement in the market and demand for steel is expected to increase this year and possibly in the coming few years, according to the market analysts. This shows expectations of expansion of fiscal policy by the new US Administration, including corporate and personal tax cuts and actions to raise steel-intensive infrastructure investment. Major energy project are also being expedited, and the recent revival of two major oil pipeline projects would add demand for steel tubular goods. Canada’s recent approval of energy pipeline projects will also support demand and production of the country’s steel sector going forward.
In India steel demand has increased in a favorable manner being nearly double over the past decade or so. Steel demand has increased nearly 5% per annum in the last few years, supported by the infrastructure and a series of consumption and investment-boosting reforms, including the “Make in India” initiative which has led to increased FDI. In the recent months the demand for steel may have been effected due to the cash shortage associated with the move to demonetize certain currency notes, but strong GDP growth in the fourth quarter of 2016 suggests that the effects may have been more muted than expected. Over the longer term, steel usage will continue to grow to be a favorable one in India, with per capita consumption converging towards higher world average levels . Within Asia, demand growth has been fastest in economies located in Southeast Asia. A report that was released by the South East Asian Iron and Steel detailing Institutes in March 2017, shows that ASEAN steel demand expanded by almost 13% in 2016, rising to a level of 78 million tonnes. Most economies in the region have posted a double-digit steel demand growth, but Vietnam had the highest growth at 20%. That country’s steel association expects significant growth in steel production over the long term, as local producers try to meet steel demand for infrastructure and to support economic development more broadly. Indeed, the country has one of the fastest growth rates in Asia (capacity has nearly doubled in the last four years).
The steel demand developments have been affected in Japan, that reflects a sluggish investment in industrial, electrical and other machinery. Following a decline of 8% in 2015, apparent steel demand has remained stable in 2016, with steel orders up in the construction sectors (particularly civil engineering) and industrial machinery and equipment’s. The output from the industries has also started to recovering in early 2017, and steel demand is expected to recover in line with improved economic prospects. In Ukraine, the mining and steel industry has undergone considerable disruptions as a result of the conflict. The economy of different country having started to recover from the deep recession, and production from industries having shown signs of recovery in late 2016 and early 2017, steel market conditions should improve somewhat going forward.
Concrete does not burn – it cannot be ‘set on fire’ unlike most other materials in a building and it does not emit any toxic fumes when affected by fire. It will also not produce smoke or drip molten particles, unlike many plastics and metals. Designing with a non-combustible material results in a structure needing simpler fire detailing and therefore having quicker construction programmers. The outcome of inadequate fire details, poor workmanship and modifications during occupation causing a fire risk are reduced when homes have a non-combustible structure.
Much of design for fire safety is concerned with ensuring that people can escape from the building or structure, fire fighters are protected and the fire cannot spread to other properties or areas. Current building regulations for England and Wales are written with these three aims and there is no requirement for protection of property or to minimize damage beyond this. Clients and project teams may choose to go beyond minimum requirements and choose to provide a higher level of protection against the hazards of fire either to further reduce the risks addressed by the building regulations or to protect property.
In the majority of applications, concrete can be described as virtually ‘fireproof’. The materials when chemically combined within concrete, form a material that is important for fire safety design, and has relatively low thermal conductivity. This low conductivity means that the effect of fire is limited to the surface zones of the concrete with the middle of the element often unaffected. This also gives concrete excellent fire separation performance.
According to Government statistics  60% of total household growth in England up to 2033 will come from households of age 65 or over. Designing beyond regulation, to protect an ageing population including vulnerable occupants, as well as occupants who are very young or with mobility limiting conditions, and therefore may need more time to escape a fire, are more reasons to choose a non-combustible material for structures. The materials used in the buildings can be classified according to the reaction to fire and resistance to fire This will determine whether a material can be used and when additional fire protection needs to be applied to it. EN 13501-1 classifies materials into seven grades (A1, A2, B, C, D, E and F).
The highest possible designation is A1 (non-combustible materials). The UK also has a National classification system, which has ‘non-combustible’, ‘limited combustibility’, Class 0, 1, 2, 3 and 4 (with the lower number indicating lower combustibility, smoke emission or flame droplets).Modern concrete and masonry are classed as A1 in the European system and ‘non-combustible’ in the National system, and do not need any further testing nor additional fire treatments. Designers have a responsibility to consider fire as a real possibility that can affect people’s lives and livelihoods. Choosing non-combustible materials, such as concrete and masonry, for the main structure designing course in kerala of a building, provides an excellent starting point for achieving a safer built environment for us all.
A new method called Hybrid construction integrates all concrete to make best advantage of their different inherent qualities. The accuracy, speed and high-quality finish of precast components can be combined with the economy and flexibility of cast in-situ concrete.
Hybrid concrete construction produces simple, buildable and competitive structures. The contractor is benefited from increased component manufacture, safe and faster construction and consistent performance.
Progressive collapse of structures means disproportion in size. Though the disproportion between cause and effect is a common feature, there are various differing mechanisms that produce such an outcome. The readiness to the theoretical treatment, approaches for quantifying indices, and possible or preferable alternate measures can vary accordingly. It is better to distinguish and describe the different types of progressive collapse. The term propagating action refers to the action that results from the failure of one element and leads to the failure of further similar elements.
A progressive collapse can be triggered by accident actions, including fire hazard, gas explosion, terrorist attack, vehicle collision, design and construction errors, and environmental corrosion. Due to industrialization, the buildings with multi-function and high complication become more common of which the safety and stability are far more concerned. Thus during the long-term use, the structure may suffer unexpected accidental actions, causing local damage or failure.
The progressive collapse of building structures is a complicated mechanical behaviour of the entire structural systems under large deformation. Problems such as large displacement, large rotation, contact and collision between specimens are inevitable during progressive collapse. Therefore, it is important to select the appropriate model for analysis to consider these features. Targeting at different objects, various progressive collapse models have been developed. The most representative models are the finite element model and the discrete element model. Before the failure of the entire structure the accurate mechanical behaviour can be calculated, but the following condition such as moving and collision between rigid bodies is hardly represented.
The progressive collapse of building structures can be analyzed using three finite models, they are the fine model, simplified model and multi-scale model. According to the mechanical behaviour of structural members the fine model can be established. This method is widely used for specimen because of its large calculations and large modelling process. Since the fine model is more time consuming and laborious simplified model is more preferred in the investigations on the progressive collapse. The ultimate mechanical behaviour of structures can be known by the simplified finite model. The finite element model can calculate the mechanical behaviour before the failure of the entire structure but the collision between the rigid bodies is not represented. The discrete element method brings out the mechanical behaviour of the structure. The dynamic effect can be known by comparing the internal forces and deformations in the dynamic and static analysis. The dynamic equation for structural progressive collapse is very complex hence is very difficult to obtain the simple mathematical expression of the dynamic effect. The structural ability to withstand the local damage due to accident is known as the robustness of the structure design courses in kerala. There are two classifications of the design methods for progressive collapse of building structures (1) the incident-dependent progressive collapse design; (2) incident-independent progressive collapse design. The first one is more accurate and mostly used with buildings with high safety requirement. The second method is all the more simpler.To put an end to the huge damage caused due to the progressive collapse several international designs and codes have been brought into effect.
The steel structure course in kerala should have adequate strength, stiffness and toughness for proper functioning.
- Preliminary member sizing of beams
- Structural analysis – modeling, analysis
- Design review – member modifications
- Cost of estimation
- Preparation of structural drawings and specifications
- Loads for structural analysis and design
- Dead load
- Live load
- Mean return period OR
- Recurrence interval OR
- Live loads for various occupencies
- Reduction in basic design live load
- Impact Load
- Wind load
1. Adaptations to site:
If it is a building, the design must be such that there are suitable arrangements for rooms, corridors, stairways, windows, elevators, emergency exits etc and all this plan should be adapted to site so that it is acceptable and at a reasonable cost. This is called functional planning.
2. Structural scheme:
structural scheme is dependent on functional planning. Structural scheme includes the location of columns in the buildings, it is to be carried out with the functional plan and sufficient space must be calculated between finished ceiling and finished floor for location of columns.
3. Structural analysis:
Once the design is laid out, structural analysis must be performed to determine internal forces that will be produced in the framework. Proper calculations must be made and it should be ensured that structure in reality also behaves as it is supposed to be
5. Factor of safety:
The following factors must be considered while developing of design to provide suitable values of the margin of safety and reliability.
- Variability of the material with respect to strength and other physical properties
- Uncertainty in the expected loads
- Precision with which internal forces are calculated
- Possibility of corrosion
- Extent of damage, loss of life
- Operational importance
- Quality of workmanship
The design safety of structures may be evaluated in either of the two ways:
- Allowable Stress Design
- Load and resistance factor design
A. Allowable stress design:
- Based on the elastic behaviour of the material.
- The stress is in allowable limits.
- The full strength of the material is not utilized but we use less value as the limited stress value.
- It is based on the elastic behaviour of the material
- The stress on structural members is kept within the allowable limits
- Full strength of the material is not utilized and a lesser value of the limited stress value is used.
- The compressive stress is divided by a factor of safety to obtain an allowable or working stress.
Disadvantages of Allowable stress design
- In ASD the internal stress is zero before any loads are applied .
- ASD does not give reasonable measure of strength. As strength is more fundamental measure of resistance than allowable stress. Safety is applied only to stress. Loads are considered to be uniform. To overcome the above limitations and drawbacks LRFD was evolved.
- During manufacturing of steel when it is cooled, the rate of cooling at the top is different than at the bottom or middle and so it causes differential cooling, thus, introducing induced stress internally.
- It does not give reasonable measure of strength. .
- Safety is applied only to stress level. Loads are considered to be uniform. If not, only option is the factor of safety.
B.Load and Resistance Factor Design(LRFD)
This is based on the principle that strength of various materials and the applied loads depend on certain factors, and thus the structural elements are designed using reduced strength and increased loads.The strength is reduced on the basis of the strength of the material. The load factor is more for the materials that cannot be easily predicted.