Design of Steel Structures Questions and Answers – Characteristic Loads This set of Design of Steel Structures Multiple Choice Questions & Answers (MCQs) focuses on “Characteristic Loads”.1. Which IS code is used for calculating different loads on different structures? a) IS 800 b) IS 200 c) IS 300 d) IS 875 View Answer Answer: d Explanation: IS 875 (all 5 parts) is recommended by Bureau of Indian Standards for calculating various types of loads on the structure.

- Part 1 is for dead loads, part 2 for imposed loads, part 3 for wind load, part 4 for snow loads and part 5 for special loads and combinations.2.
- Which of the following load is to be considered on liquid retaining structure? a) hydrostatic load b) wave and current load c) earth pressure d) dynamic load View Answer Answer: a Explanation: Hydrostatic load is considered on liquid retaining structures or hydraulic structures.

Wave and current load is considered in marine and offshore structure. Earth pressure is considered in basements, retaining walls, column footings, etc. Dynamic load is due to earthquake and wind.3. What is P-Δ effect? a) earthquake load b) second order moments arising from joint displaced c) second order moments arising from member deflection d) load due to shrinkage effect View Answer Answer: b Explanation: Second order moments arising from joint displaced is called P-Δ effect and second order moments arising from member deflection is called P-δ effect.

Note: Join free Sanfoundry classes at or 4. Match the pair : (A) Mass and gravitational effect (i) wind load (B) Mass and acceleration effect (ii) load due to settlement (C) Environmental effects (iii) imposed load a) A-i, B-ii, C-iii b) A-iii, B-ii, C-i c) A-iii, B-i, C-ii d) A-ii, B-iii, C-i View Answer Answer: c Explanation: Load on structure may be due to following : 1) Mass and gravitational effect : examples of such loads are dead loads, imposed loads, snow and ice loads, earth loads, etc.2) Mass and acceleration effect : examples of such loads are those caused by earthquake, wind, impact, blasts, etc.3) Environmental effects : examples of such loads are due to temperature difference, settlement, shrinkage, etc.

Check this: | 5. The probability that a specific load will be exceeded during life of structure depends on _ a) wind b) factor of safety c) partial factor of safety d) period of exposure View Answer Answer: d Explanation: The probability that a specific load will be exceeded during life of structure depends on period of exposure.

It also depends on magnitude of design load.6. What is characteristic load? a) seismic load b) load which will be exceeded by certain probability during life of structure c) load which will not be exceeded by certain probability during life of structure d) pressure load View Answer Answer: c Explanation: Characteristic load is the load which will not be exceeded by certain assumed or pre-assumed probability during life of structure.

These loads are anticipated loads due to self weight, imposed load, snow, wind load, etc.7. Which of the following is not included in imposed load classification? a) Residential load b) Earthquake load c) Industrial load d) Educational load View Answer Answer: b Explanation: Imposed loads are gravity loads other than dead load and cover factors such as occupancy by people, stored material etc.

- It is classified into following groups : (i)residential, (ii)educational, (iii)institutional, (iv)assembly halls, (v)office and business buildings, (vi)mercantile buildings, (vii)industrial, (viii)storage buildings.8.
- What is the minimum imposed load on roof trusses as per IS code? a) 0.5 kN/m 2 b) 0.4 kN/m 2 c) 0.9 kN/m 2 d) 0.75 kN/m 2 View Answer Answer: b Explanation: As per IS 875, the minimum imposed load on roof truss should be 0.4 kN/m 2,

For sloping roof upto 10˚, the imposed load is taken as 0.5 kN/m 2 if access is not provided and 0.75 kN/m 2 if access is provided.9. For roofs of slope greater than 10˚, the imposed load is reduced by _ for every degree rise in slope. a) 0.02 kN/m 2 b) 0.05 kN/m 2 c) 0.75 kN/m 2 d) 0.5 kN/m 2 View Answer Answer: a Explanation: As per IS 875, for roofs of slope greater than 10 o, the imposed load is taken as 0.75 kN/m 2 and reduced by 0.02 kN/m 2 for every degree rise in slope.10.

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Contents

- 1 What is the difference between live load and imposed load?
- 2 What is imposed load example?
- 3 Is a ceiling a live load?
- 4 What is loading test in construction?
- 5 What is the dead load for residential building?
- 6 What does imposed load mean construction?
- 7 What does imposed load mean construction?
- 8 What are dead and imposed loads?
- 9 What are the two types of loads?

#### What is an imposed load?

What is an Imposed Load? Imposed loads are temporary, changeable or dynamic loads acting upon a structure. The magnitude of these loads is typically related to the occupancy of the space or building where the load is applied. For example, the imposed loads in an industrial facility will be different from those in a residential building.

- Imposed loads can also vary depending on the time of day.
- For example, the imposed loads in a typical office building will be higher during working hours than at night or on weekends when fewer employees are present.
- Imposed loads are also known as live loads.
- Understanding the imposed loads is crucial in the engineering design of various structures such as buildings, bridges, offshore platforms, etc.

These loads are chosen by the engineer for use in design calculations. Some of the most common sources of imposed loads include:

OccupantsVehicle trafficEquipmentFurnitureMovable partitions

Imposed loads can be viewed as those loads that are added (or imposed) on the structure in addition to permanent loads. Engineers use various codes and standards, such as the American Society of Civil Engineers’ ASCE 7, to determine the imposed loads on a particular structure. Synonyms Imposed Loading, LIve Load Share this Term : What is an Imposed Load?

## What is the difference between live load and imposed load?

Live Loads – Live loads on floors and roofs consists of all the loads which are temporarily placed on the structure, For example, loads of people, furniture, machines etc. Live loads keep on changing from time to time. Live loads are also called as imposed loads.

### What is characteristic load?

Characteristic Load or ultimate load –

- The characteristic load is the ultimate load that is liable to come on structure during its lifetime. For simplicity, the variation in the loading is also assumed to follow a normal distribution cure, the characteristic load or ultimate load is given as
- Characteristic load or ultimate load = Mean load + 1.64 S
- \

Characteristic load is that value of load which has a 95 percent probability of not being exceeded during the life time of the structure. In absence of any data, loads given in various standards shall be assumed as the characteristic loads. The following standards may be used for this purpose.

- IS 875 (Part 1) – for dead loads
- IS 875 (Part 2) – for imposed loads
- IS 875 (Part 3) – for wind loads
- IS 875 (Part 4) – for snow loads
- IS 1893 (Part 1) – for earthquake loads

: Characteristic Strength of Materials Characteristic Load or ultimate load

#### What is characteristic load and design load?

Free CT 1: Building Materials (Building Stones) 10 Questions 10 Marks 7 Mins Design Load (L d ) = Characteristics Load (L c ) × Partial factor of safety (γ f ) Characteristics load is computed from statistical data of the graph shown below: It is assumed that in ninety-five per cent cases the characteristic loads will not be exceeded during the life of the structures. However, structures are subjected to overloading also. Structures should be designed with loads obtained by multiplying the characteristic loads with suitable factors of safety depending on the nature of loads or their combinations, and the limit state being considered.

- These factors of safety for loads are termed as partial safety factors (γ f ) for loads.
- Thus, the design loads are calculated as Last updated on Sep 22, 2022 The Staff Selection Commission has released the admit card for all regions for Paper I of the SSC JE CE 2022 exam on 9th November 2022.
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## What is imposed load example?

The term ‘ structural load ‘ refers to forces acting on the structural components of built assets such as a buildings, Structural analysis is a very important part of the design of buildings and other built assets such as bridges and tunnels, as structural loads can cause stress, deformation and displacement that may result in structural problems or even failure,

The building regulations require that structures must be designed and built to be able to withstand all load types that they are likely to face during their lifecycle, Design requirements are generally specified in terms of the maximum loads that a structure must be able to withstand. See also: Force,

There are a number of different types of load than can act on a structure, the nature of which will vary according to the design, use, location and materials being used within, or imposer on the structure, Loads are generally classified as either dead loads (DL) or live loads (LL):

Dead structural loads remain relatively constant, such as the structure’s self weight. Live structural loads may vary such as traffic loads, Environmental structural loads, Concentrated structural loads, Structural line loads, Distributed structural loads,

Dead loads, also known as permanent or static loads, are predominantly associated with the weight of the structure itself, and as such remain stationary and relatively constant over time. Dead loads may include the weight of any structural elements, permanent non- structural partitions, immovable fixtures such as plasterboard, built-in cupboards, and so on.

Dead loads can be calculated by assessing the weights of materials specified and their volume as shown on drawings, This means that in theory, it should be possible to calculate dead loads with a good degree of accuracy, However, structural engineers are sometimes conservative with their estimates, minimising potential deflections, allowing a margin of error and allowing for alterations over time, and so design dead loads often far exceed those experienced in practice,

For more information see: Dead loads, Live loads, also known as imposed loads, are usually temporary, changeable and dynamic. These include loads such as vehicle traffic, occupants, furniture and other equipment, The intensity of these loads may vary depending on the time of day, for example an office building may experience increased live loads during week- day work hours but much smaller loads during the night or at weekends. Environmental structural loads, may act on a structure as a result of topographic or weather conditions, Note this maybe shortened to environmental loads in the context of discussing structures, there are many other environmental loads that act on a building though some of which have a lesser impact on structural loads but none the less impact the buildings performance and comfort levels, these might be terms as environmental factors,

In turn these should not be confused with environmental impacts which is more likely to describe sustainability issues surrounding the use of materials, energy performance, waste, biodiversity impacts etc. Wind load (WL) Wind loads can be applied by the movement of air relative to a structure, and analysis draws upon an understanding of meteorology and aerodynamics as well as structures,

Wind load may not be a significant concern for small, massive, low- level buildings, but it gains importance with height, the use of lighter materials and the use of shapes that my affect the flow of air, typically roof forms, Where the dead weight of a structure is insufficient to resist wind loads, additional structure and fixings may be required.

Corner streams or jets that occur around the corners of buildings, Vortex shedding that occurs in the wake of a building, Through-flow, or passage jets, that occur in a passage through a building or small gap between two buildings,

In complex situations, it may be necessary to undertake wind tunnel testing of building forms to assess the change in air flows caused by the presence of a structure, Increasingly, analysis is also possible using computational fluid dynamics software,

### What are the 3 types of loads?

Different types of loads in buildings and structures A structural load is a force, deformation, or acceleration applied to structural elements. A load causes stress, deformation, and displacement in a structure. Structural analysis, a discipline in engineering, analyzes the effects of loads on structures and structural elements. Different types of loads The loads in buildings and structures can be classified as vertical loads, horizontal loads and longitudinal loads. The vertical loads consist of dead load, live load and impact load. The horizontal loads consist of wind load and earthquake load.

The longitudinal loads i.e. tractive and braking forces are considered in special cases of design. The estimation of various loads acting is to be calculated precisely. Indian standard code IS: 875–1987 and American Standard Code ASCE 7: Minimum Design Loads for Buildings and Other Structures specifies various design loads for buildings and structures.

Each of them is discussed below. Dead load Dead loads, also known as permanent or static loads, are those that remain relatively constant over time and comprise, for example, the weight of a building’s structural elements, such as beams, walls, roof and structural flooring components.

Dead loads may also include permanent non-structural partitions, immovable fixtures and even built-in cupboards. Dead loads comprise the weight of the structure or other fixed elements before any live loads are taken into consideration. Live loads are added to the dead load to give the total loading exerted on the structure.

The calculation of dead loads of each structure is calculated by the volume of each section and multiplied by the unit material weight. Live load Live load is a civil engineering term that refers to a load that can change over time. The weight of the load is variable or shifts locations, such as when people are walking around in a building.

Anything in a building that is not fixed to the structure can result in a live load since it can be moved around. Live loads are factored into the calculation of the gravity load of a structure. They are measured in pounds per square foot. The minimum live-load requirements are based on the expected maximum load.

A live load can be expressed either as a uniformly distributed load (UDL) or as one acting on a concentrated area (point load). It may eventually be factored into the calculation of gravity loads. Wind load Wind loads can be applied by the movement of air relative to a structure, and analysis draws upon an understanding of meteorology and aerodynamics as well as structures.

Wind load may not be a significant concern for small, massive, low-level buildings, but it gains importance with height, the use of lighter materials and the use of shapes that may affect the flow of air, typically roof forms. Where the dead weight of a structure is insufficient to resist wind loads, additional structure and fixings may be required.

Wind load is required to be considered in structural design especially when the heath of the building exceeds two times the dimensions transverse to the exposed wind surface. The design wind loads for buildings and other structures shall be determined according to one of the following procedures:

- Method 1 – Simplified procedure for low-rise simple diaphragm buildings
- Method 2 – Analytical procedure for regular shaped building and structures
- Method 3 – Wind tunnel procedure for geometrically complex buildings and structures

Snow load This is the load that can be imposed by the accumulation of snow and is more of a concern in geographic regions where snowfalls can be heavy and frequent. Significant quantities of snow can accumulate, adding a sizable load to a structure. The shape of a roof is a particularly important factor in the magnitude of the snow load.

- MOISTURE CONTENT
- ACCUMULATION:
- DISTRIBUTION
- TEMPERATURE VARIATIONS

Earthquake load Earthquake load takes place due to the inertia force produced in the building because of seismic excitations. Inertia force varies with the mass. The higher mass of the structure will imply that the earthquake loading will also be high.

- When the earthquake load exceeds the moment of resistance offered by the element, then the structure will break or damage.
- The magnitude of earthquake loading depends upon the weight or mass of the building, dynamic properties of the building and difference in stiffness of adjacent floors along with the intensity and duration of the earthquake.

Earthquake load acts over the surface of a structure placed on the ground or with an adjacent building. Buildings in areas of seismic activity need to be carefully analysed and designed to ensure they do not fail if an earthquake should occur. Earthquake load depends on the following factors;

- Seismic hazard
- Parameter of the structure
- Gravity load.

Load combination A load combination results when more than one load type acts on the structure. Building codes usually specify a variety of load combinations together with load factors (weightings) for each load type to ensure the safety of the structure under different maximum expected loading scenarios.

- Special loads
- Thermal load – The loads occur when the materials expand or contract with temperature change and this can exert significant loads on a structure.
- Settlement load – When one part of a building settles more than other parts this type of load occurs.
- Flood load – These are caused by flood and water ingress in the foundation which results in corrosion.
- Soil and fluid load – It is caused due to excessive flow of water in the soil which impacts the soil density.
- Conclusion

With loads established, structural engineers can design the complete structure. The use of building code dimension tables and the appropriate sizes of structural members with correct load calculation can hugely determine the stability of a building. : Different types of loads in buildings and structures

## Is a ceiling a live load?

Dead Load – The weight of a building’s structural parts, such as roof, structural flooring components, beams, and walls, are examples of dead loads, also known as permanent or static loads, that remain essentially constant throughout time. Permanent non-structural dividers, fixed fixtures, and even built-in cabinets can all be considered dead loads.

#### Is rain load a live load?

Live loads are those loads produced by the use and occupancy of a building or structure and do not include construction loads, environmental loads (such as wind loads, snow loads, rain loads, earthquake loads and flood loads) or dead loads (see the definition of ‘Live Load’ in IBC 202).

#### What is design load limit?

Design load

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In a general sense, the design load is the maximum amount of something a system is designed to handle or the maximum amount of something that the system can produce, which are very different meanings. For example, a with a design load of 20 tons is designed to be able to lift loads that weigh 20 tons or less.

However, when a failure could be catastrophic, such as a crane dropping its load or collapsing entirely, a is necessary. As a result, the crane should lift about 2 to 5 tons at the most. In, a design load is greater than the load which the system is expected to support. This is because engineers incorporate a in their design, in order to ensure that the system will be able to support at least the expected loads (called, despite any problems with construction, materials, etc.

that go unnoticed during construction. A would have a general design load, meaning the maximum amount of heat it can produce. A bridge would have a specified load, with the design load being determined by engineers and applied as a theoretical load intended to ensure the actual real-world capacity of the specified load.

### What is a factored load?

Factored design loads are determined by multiplying a service load by a load factor. Service loads on a structural member, for example, are the actual loads that will be assumed to act on the member when the structure is in service, i.e. loads assumed to occur over the anticipated service life of the structure.

## What is loading test in construction?

Load Testing 101 A load test is performed by applying pressure to a specific pile in predetermined directions; either by compression (push), tension (pull), or laterally. The load is generally applied via a hydraulic jack to make sure the pressure is equal to the final load requirement.

#### How do you calculate loading limits?

Working Load Limits Working Load Limit (WLL) is the maximum working load designed by the manufacturer. This load represents a force that is much less than that required to make the lifting equipment fail or yield. The WLL is calculated by dividing the breaking load limit (BLL) by a safety factor (SF).

For forged products Suncor uses a 5:1 safety factor (SF).For cast products Suncor uses a 4:1 safety factor (SF).For all other products, such as assemblies, Suncor uses a 4:1 safety factor (SF).

: Working Load Limits

## What is the dead load for residential building?

Generally, the customary floor dead load is 10-12 PSF (pounds per square foot) for floors, 12-15 PSF for roof rafters and 20 PSF for roof trusses. However, these may increase when a heavy finish material, such as brick veneer walls or tile floors/roofs, is specified.

#### What is a 1.5 kPa floor load?

Area of floor = 6.0 m x 4.0 m = 24 m 2 Live load rating of a house = 1.5 kPa Therefore, live load of floor = 24 m 2 x 1.5 kPa = 36 kN All unfixed items in a building such as people and furniture result in a ‘live’ load on the structure. Live loads are exerted in the vertical plane.

Live loads for floors as per building usage | Uniformly distributed load kPa or kN/m 2 |
---|---|

Houses | 1.5 |

Flats, apartments, motel bedrooms | 2.0 |

Offices | 3.0 |

Workshops | 5.0 |

Parking, vehicle > 2.5 t | 5.0 |

Hospitals, school assembly areas with fixed seating | 3.0 |

Dance halls, bars, lounges | 5.0 |

Table 2: Live load comparisons Note that kPa and kN/m 2 are essentially the same units. Need more information about units of force?

## What does imposed load mean construction?

Imposed loads (quasi-permanent variable actions) are defined as loads that are applied to the structure.

## What does imposed load mean construction?

Imposed loads (quasi-permanent variable actions) are defined as loads that are applied to the structure.

#### What are the 3 types of loads?

Different types of loads in buildings and structures A structural load is a force, deformation, or acceleration applied to structural elements. A load causes stress, deformation, and displacement in a structure. Structural analysis, a discipline in engineering, analyzes the effects of loads on structures and structural elements. Different types of loads The loads in buildings and structures can be classified as vertical loads, horizontal loads and longitudinal loads. The vertical loads consist of dead load, live load and impact load. The horizontal loads consist of wind load and earthquake load.

The longitudinal loads i.e. tractive and braking forces are considered in special cases of design. The estimation of various loads acting is to be calculated precisely. Indian standard code IS: 875–1987 and American Standard Code ASCE 7: Minimum Design Loads for Buildings and Other Structures specifies various design loads for buildings and structures.

Each of them is discussed below. Dead load Dead loads, also known as permanent or static loads, are those that remain relatively constant over time and comprise, for example, the weight of a building’s structural elements, such as beams, walls, roof and structural flooring components.

Dead loads may also include permanent non-structural partitions, immovable fixtures and even built-in cupboards. Dead loads comprise the weight of the structure or other fixed elements before any live loads are taken into consideration. Live loads are added to the dead load to give the total loading exerted on the structure.

The calculation of dead loads of each structure is calculated by the volume of each section and multiplied by the unit material weight. Live load Live load is a civil engineering term that refers to a load that can change over time. The weight of the load is variable or shifts locations, such as when people are walking around in a building.

Anything in a building that is not fixed to the structure can result in a live load since it can be moved around. Live loads are factored into the calculation of the gravity load of a structure. They are measured in pounds per square foot. The minimum live-load requirements are based on the expected maximum load.

A live load can be expressed either as a uniformly distributed load (UDL) or as one acting on a concentrated area (point load). It may eventually be factored into the calculation of gravity loads. Wind load Wind loads can be applied by the movement of air relative to a structure, and analysis draws upon an understanding of meteorology and aerodynamics as well as structures.

Wind load may not be a significant concern for small, massive, low-level buildings, but it gains importance with height, the use of lighter materials and the use of shapes that may affect the flow of air, typically roof forms. Where the dead weight of a structure is insufficient to resist wind loads, additional structure and fixings may be required.

Wind load is required to be considered in structural design especially when the heath of the building exceeds two times the dimensions transverse to the exposed wind surface. The design wind loads for buildings and other structures shall be determined according to one of the following procedures:

- Method 1 – Simplified procedure for low-rise simple diaphragm buildings
- Method 2 – Analytical procedure for regular shaped building and structures
- Method 3 – Wind tunnel procedure for geometrically complex buildings and structures

Snow load This is the load that can be imposed by the accumulation of snow and is more of a concern in geographic regions where snowfalls can be heavy and frequent. Significant quantities of snow can accumulate, adding a sizable load to a structure. The shape of a roof is a particularly important factor in the magnitude of the snow load.

- MOISTURE CONTENT
- ACCUMULATION:
- DISTRIBUTION
- TEMPERATURE VARIATIONS

Earthquake load Earthquake load takes place due to the inertia force produced in the building because of seismic excitations. Inertia force varies with the mass. The higher mass of the structure will imply that the earthquake loading will also be high.

When the earthquake load exceeds the moment of resistance offered by the element, then the structure will break or damage. The magnitude of earthquake loading depends upon the weight or mass of the building, dynamic properties of the building and difference in stiffness of adjacent floors along with the intensity and duration of the earthquake.

Earthquake load acts over the surface of a structure placed on the ground or with an adjacent building. Buildings in areas of seismic activity need to be carefully analysed and designed to ensure they do not fail if an earthquake should occur. Earthquake load depends on the following factors;

- Seismic hazard
- Parameter of the structure
- Gravity load.

Load combination A load combination results when more than one load type acts on the structure. Building codes usually specify a variety of load combinations together with load factors (weightings) for each load type to ensure the safety of the structure under different maximum expected loading scenarios.

- Special loads
- Thermal load – The loads occur when the materials expand or contract with temperature change and this can exert significant loads on a structure.
- Settlement load – When one part of a building settles more than other parts this type of load occurs.
- Flood load – These are caused by flood and water ingress in the foundation which results in corrosion.
- Soil and fluid load – It is caused due to excessive flow of water in the soil which impacts the soil density.
- Conclusion

With loads established, structural engineers can design the complete structure. The use of building code dimension tables and the appropriate sizes of structural members with correct load calculation can hugely determine the stability of a building. : Different types of loads in buildings and structures

## What are dead and imposed loads?

What Is Live Load and Dead Load in Construction? – The dead loads are permanent loads which result from the weight of the structure itself or from other permanent attachments, for example, drywall, roof sheathing, and weight of the truss. Live loads are temporary loads ; they are applied to the structure on and off over the life of the structure.

## What are the two types of loads?

LOADS ON BUILDINGS LOAD TYPES The determination of the loads acting on a structure is a complex problem. The nature of the loads varies essentially with the architectural design, the materials, and the location of the structure. Loading conditions on the same structure may change from time to time, or may change rapidly with time.

Loads are usually classified into two broad groups: dead loads and live loads. Dead loads (DL) are essentially constant during the life of the structure and normally consist of the weight of the structural elements. On the other hand, live loads (LL) usually vary greatly. The weight of occupants, snow and vehicles, and the forces induced by wind or earthquakes are examples of live loads.

The magnitudes of these loads are not known with great accuracy and the design values must depend on the intended use of the structure. In structural analysis three kinds of loads are generally used:

- Concentrated loads that are single forces acting over a relatively small area, for example vehicle wheel loads, column loads, or the force exerted by a beam on another perpendicular beam.
- Line loads that act along a line, for example the weight of a partition resting on a floor, calculated in units of force per unit length.
- Distributed (or surface) loads that act over a surface area. Most loads are distributed or are treated as such, for example wind or soil pressure, and the weight of floors and roofing materials.

- Dead Loads (DL)
- Live Loads (LL)
- Wind Load (WL)
- Snow Load (SL)
- Earthquake Load
- Thermal Loads
- Settlement Loads
- Dynamic Loads
- CALCULATION OF LOADS

The structure first of all carries the dead load, which includes its own weight, the weight of any permanent non-structural partitions, built-in cupboards, floor surfacing materials and other finishes. It can be worked out precisely from the known weights of the materials and the dimensions on the working drawings.

Although the dead load can be accurately determined, it is wise to make a conservative estimate to allow for changes in occupancy; for example, the next owner might wish to demolish some of the fixed partitions and erect others elsewhere. All the movable objects in a building such as people, desks, cupboards and filing cabinets produce an imposed load on the structure.

This loading may come and go with the result that its intensity will vary considerably. At one moment a room may be empty, yet at another packed with people. Imagine the `extra’ live load at a lively party! Wind has become a very important load in recent years due to the extensive use of lighter materials and more efficient building techniques.

A building built with heavy masonry, timber tiled roof may not be affected by the wind load, but on the other hand the structural design of a modern light gauge steel framed building is dominated by the wind load, which will affect its strength, stability and serviceability. The wind acts both on the main structure and on the individual cladding units.

The structure has to be braced to resist the horizontal load and anchored to the ground to prevent the whole building from being blown away, if the dead weight of the building is not sufficient to hold it down. The cladding has to be securely fixed to prevent the wind from ripping it away from the structure.

The magnitude of the snow load will depend upon the latitude and altitude of the site. In the lower latitudes no snow would be expected while in the high latitudes snow could last for six months or more. In such locations buildings have to be designed to withstand the appropriate amount of snow. The shape of the roof also plays an important part in the magnitude of the snow load.

The steeper the pitch, the smaller the load. The snow falling on a flat roof will continue to build up and the load will continue to increase, but on a pitched roof a point is reached when the snow will slide off. Earthquake loads affect the design of structures in areas of great seismic activity, such as north and south American west coast, New Zealand, Japan, and several Mediterranean countries.

- Only minor disturbances have been recorded in east Asia and Australia.
- All building materials expand or contract with temperature change.
- Long continuous buildings will expand, and it is necessary to consider the expansion stresses.
- It is usual to divide a reinforced concrete framed building into lengths not exceeding 30 m and to divide a brick wall into lengths not exceeding 10 m.

Expansion joints are provided at these points so that the structure is physically separated and can expand without causing structural damage. If one part of a building settles more than another part, then stresses are set up in the structures. If the structure is flexible then the stresses will be small, but if the structure is stiff the stresses will be severe unless the two parts of the building are physically separated.

Dynamic loads, which include impact and aerodynamic loads, are complex. In essence, the magnitude of a load can be greatly increased by its dynamic effect. Actual loadings in a building are typically either concentrated or uniformly distributed over an area. The former need no further consideration other than as necessary to characterise them as a force vector.

In the latter, however, some modelling is needed when the area considered is actually made up of an assembly of one-way line and surface elements. These elements would pick up different portions of the total load acting over the surface, depending on their arrangement.

Consider the simple structural assembly shown in Figure 1 (a). Eight pre-cast concrete elements are supported by three beams Both external beams have to carry the weight of a half concrete element The middle beam carries the weight of one element ( of the left and right element as illustrated in Figure 1 (b)).

The reactions from all the elements supported by a beam then become loads acting on the beam. Note that these loads form a continuous line load on the beam. Loads of this type are expressed in terms of a load or force per unit length (i.e. N/m) and are commonly encountered in the structural analysis process. Figure 1 Another way of looking at this same loading is to think in terms of contributory areas. Each of the beams can be considered as supporting an area of the extent indicated in Figure 2 (a) and (b). The width of each area is often called the load strip.

The load acting over the width of the load strip is transferred to the support beams. If the uniformly distributed load is constant and the load strip is of a constant width, the amount of load carried per unit length by the support beam is simply the load per unit area multiplied by the width of the load strip.

This process is illustrated in Figure 2. The result is again a continuous line load describable in terms of a load per unit length. This process is valid for equal uniformly distributed loads only. Figure 1 The loading considered should, of course, include both live- and dead-load components. The exact value of the latter can be found by calculating the volume contributary area the thickness of the material and multiply it by the unit weights for that material.

Determining these values can be tedious. An alternative is to use a unit weight, e.g. the weight for one square metre, typically expressed as a force per unit area, to represent the weight expressed as N/m 2,. Since live loads are also expressed in terms of a force per unit area, the calculation process is facilitated, since both loads can be considered simultaneously.

Some sample load calculations per m2 are shown below. SAMPLE DESIGN CALCULATIONS For design purposes it is most appropriate to select a unit area for all loads (dead, live, wind etc.). This often simplifies the calculation because the unit area may be used for members with the same loading but different contributory areas.

- To determine the load per unit area is the most appropriate procedure in structural design.
- The total load can easily be calculated by load per unit area times the contributary area.
- For design purposes often the unit loading strip is used as indicated in Figure 1 (b) above.
- It is convenient to determine first all the loadings per unit area that occur frequently throughout the building.

The advantage is that these figures can then be used for all different areas or floor levels with the same loading. The following is an example of a unit load determination for an office building. FLAT ROOF

Tanking (Bituminous felt (5-ply) and 50 mm gravel | 1.20 kN/m 2 | |

50 mm Insulation | 0.03 “ | |

180 mm Concrete slab (0.18 x 25 kN/m 3 ) | 4.50 “ | |

13 mm Gypsum plaster | 0.22 ” | |

DEAD LOAD | 5.95 kN/m 2 | |

LIVE LOAD (SA 1170.1 & 4.8.1.1) | 0.25 kN/m 2 | |

TOTAL LOAD | 6.20 kN/m 2 |

OFFICES

Carpet | 0.05 kN/m 2 | |

50 mm Insulation | 0.03 “ | |

200 mm Concrete slab (0.20 x 25 kN/m 3 ) | 5.00 “ | |

13 mm Gypsum plaster | 0.22 ” | |

DEAD LOAD | 5.30 kN/m 2 | |

LIVE LOAD (Appendix B 6.11) | 3.00 kN/m 2 | |

TOTAL LOAD | 8.30 kN/m 2 |

CORRIDORS AND PASSAGEWAYS

Carpet | 0.05 kN/m 2 | |

40 mm Screed (0.04 x 22 kN/m 3 ) | 0.88 “ | |

20 mm Insulation | 0.05 “ | |

200 mm Concrete slab (0.20 x 25 kN/m 3 ) | 5.00 “ | |

13 mm Gypsum plaster | 0.22 ” | |

DEAD LOAD | 6.20 kN/m 2 | |

LIVE LOAD (Appendix B 6.4) | 4.00 kN/m 2 | |

TOTAL LOAD | 10.20 kN/m 2 |

STAIRS AND LANDINGS

Stairs | ||

Marble tiles | 0.42 kN/m 2 | |

Concrete wedge (2 x 0.17 x 0.25 x 4 x 23.5 kN/m 2 | 2.08 kN/m 2 | |

160 mm Concrete slab (0.16 x 25 kN/m 2 ) | 4.00 ” | |

DEAD LOAD | 6.50 kN/m 2 | |

LIVE LOAD (Appendix B 6.4) | 4.00 kN/m 2 | |

TOTAL LOAD | 10.50 kN/m 2 |

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Landings Marble tiles 0.42 kN/m 2 160 mm Concrete slab (0.16 x 25 kN/m 2 ) 4.00 ” DEAD LOAD 4.42 kN/m 2 LIVE LOAD (Appendix B 6.4) 4.00 kN/m 2 TOTAL LOAD 8.42 kN/m 2Having compiled the required unit loading figures the load per running metre for a particular member can be calculated quite quickly by multiplying the unit load with the appropriate depth of the loading strip, or in case the total dead load on a member is needed by multiplying the unit load with the contributary area.

- AUSTRALIAN STANDARD LOADING CODE (AS 1170 PART 1) In the previous Unit the external loads on structures were classified in several different ways.
- The minimum design load on structures must be in accordance with the SAA Loading Code SA 1170 Parts 1 to 3.
- According to Part 1 `Dead and Live Loads and Load Combination’, the structure must be designed for the worst load combination for strength, stability and serviceability for limit states design.

It is beyond the scope of this subject to consider all load combinations (strength limit stages, stability limit stages and serviceability stages) of the standard. We will only consider the following load combination for strength limit stage: Where G,Q,W u are parts of dead, live, and wind loads, and have the following meaning: There are some other live loads, which are considered in this subject. Handrails, balustrades and railings of private dwellings must resist a single force of 0.6 kN acting inward, outward or downward at any point on the handrail, a continuous load of 0.4 kN/m, and the wind load acting on or transmitted to the handrail.

All other handrails including parapets and railings to all roofs shall resist a static load of 0.75 kN/m acting inward, outward or downward or the appropriate wind load, whichever produces the most adverse effects. For all non-trafficable roofs, either flat or pitched, each member providing support to the cladding thereof (including decking, purlins, beams and trusses) shall be designed to withstand the live load resultant from stacked materials or equipment used in repair or maintenance operations which shall be taken as 0.25 kPa on the plan projection, except that where the area supported by any structural member is less than 14.0 m², the intensity of live loads on that member shall be determined as follows: Live load = (1.8/A + 0.12) kPa A = the plan projection of the surface area of roof supported by the member under analysis, in square metres.

For flat or near-flat roofs and balconies which are intended to be available for pedestrian traffic or resort, the construction (including decking, purlins, beams and trusses) shall be designed to support the following uniformly distributed live load or a concentrated load of 1.8 kN, whichever load gives the more adverse effect –

- (a) for houses: 3 kPa (for 10.0 m² or less) varying linearly to 1.5 kPa (for 40.0 m² or greater);
- (b) for all other buildings: 4 kPa (for 10.0 m² or less) varying linearly to 3 kPa (for 40.0 m² or greater);
- Cantilevered sections of trafficable roofs shall be designed for the live load corresponding to the area of 10.0 m² or less.

- Students who want more depth of information may refer to Part 1 and Part 2 of the Loading Code
- The following examples show you how to calculate the dead load (DL) of a structural member or component and live load (LL) on a floor area of a residential building.
- Example 1
- We use the following formula to calculate the dead load:

Dead load = Volume × Density (DL = m 3 × kN / m 3 Calculate the weight (DL) for a Glulam beam, size 420 × 75 mm 5.4 m long. Density of timber is 1100 kg/m 3 Solution: First convert mass density in weight density.1100 kg/m 3 = 11000 N/m 3 = 11 kN/m 3 Now we can calculate the weight of the timber beam (bearer):

W | = | 0.420 × 0.075 × 5.4 × 11 |

= | 1.87 kN |

Example 2: Calculate the live load (LL) that the bearer has to carry (contritbutary area is 5.4 × 3.6 m). The applicable LL according to AS 1170 Part 1 (Dead and live load) is 1.5 kPa for residential application.

- Remember 1 kPa = 1 kN/m 2
- Solution: Using the formula LL = m (length) × m (width) × kN/m 2

LL | = | 5.4 × 3.6 × 1.5 |

= | 29.16 kN |

You have studied hard take a break before you click for more load calculations. : LOADS ON BUILDINGS