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Transfer Loads from the Rafter to the Beam and Column to the Ground

 ✅ Paper Type: Free Essay ✅ Subject: Construction ✅ Wordcount: 5024 words ✅ Published: 23rd Sep 2019

Transfer Loads from the Rafter to the Beam and Column to the Ground

Introduction

In this assignment will following 13 questions from some detail researches Moreover, this project is aimed at getting understand and interpret structures in the built environment. The building of Casa R is mainly used for live load and dead load analysis, load calculation process, impact of wind force and stress analysis of structure. In addition, photographs and drawings are used to show the direction of force and to introduce different structural elements.

1.    Annotate on pictures of the structure all elements that are to be considered as dead load (you may need to use at least 3 different pictures to show all elements).

Roof frame

Steel frame

Braced frame

stairway

door

Steel bracing

Foundation

Piers

Steel columns

Windows

Steel structures

Timber internal wall structures

Timber floor

Roof sheeting

Skylight

Steel bearer

Timber external wall structure

Floor slab

Figure 1 elements of Casa R (Santibañez, 2018)

2.    Describe the calculation procedure of the total dead load of the structural frame within the building.

Point 1:

Assumption a square hollow section used to rafters, collar tie, beam and columns. (below has shown on figure 2) Through dimension (below has shown on figure 3) of each element that use width multiply height get area of each elements, and then to multiply them length get volume.

Point 2:

Through density of steel 7850kg/m3 multiply them volume able to gain weight of one frame.

Point 3:

Using them weight to multiply 7 frames and then able to gain total dead load of whole building.

rafters

Collar tie

Width

beam

Height

Columns

Figure 2 1 frame of each elements                                   Figure 3 dimension of square hollow section

3.    Consider AS1170.1. What are the live loads that this structure be designed for? Are there any other considerations (based on the structure’s use) that the engineers should consider?

 Type of activity/occupancy for part of the building or structure Specific uses Uniformly distributed actions  kPa A Domestic and residential activities A1 Self-contained dwellings General areas, private kitchens and laundries in self-contained dwellings 1.5 Balconies, and roofs used for floor type activities, in self-contained dwellings— (a) less than 1 m above ground level (b) other 1.5 2.0 A2 Bedrooms, toilet areas 2.0 Stairs and landings in self-contained dwellings 2.0 E Warehousing and storage areas. Areas subject to accumulation of goods. Areas for equipment and plant General storage other than those specified 2.4 for each metre of storage height F Light vehicle traffic areas Parking, garages, driveways and ramps restricted to cars, light vans, etc., not exceeding 2500 kg gross mass 2.5

Figure 4 Reference values of imposed floor actions (SAIGOLBAL, 2002)

– First floor:

• parking area, live load is 2.5 kPa,
• storage area, live load is 2.4 kPa for each meter of storage height,
• kitchen area, live load is 1.5 kPa,
• toilet area, live load is 2.0 kPa,
• balcony area, live load is 1.5 kPa,
• Stairs and landings, live load is 2.0 kPa.

– Second floor:

• bedroom, live load is 2.0 kPa,
• balcony area, live load is 1.5 kPa,
• Stairs and landings, live load is 2.0 kPa.

4.    Draw the load path for a person standing on the roof. Use both plan and elevation views.

Figure 5 elevation views of Load path

Figure 6 plan views of load path

5.    Discuss how stability is provided to the building for all wind directions. Annotate diagrams of the structure to demonstrate the stability/bracing system (for both orthogonal load directions).

The building of Casa R has a good bracing system, thought bracing system provided a stable support to resist wind loads. (figure 7 has describe stability system of Casa R)

Here show tow kind of wind loads in Casa R building:

Cross wind load for stability provided by frame action, i.e. rigid connection at rafter/column connection along uplift, bearing and sliding resistance capacity of footing.

Longitudinal Wind load for stability provided by roof bracing, wall bracing along uplift, bearing and sliding resistance capacity of footing. (figure 8)

Figure 7 Stability/bracing system

Figure 8 all direction of wind loads

Compression

Tension

Compression

Figure 9 stable braced frame

6.    Research a similar structure in Australia made from timber and compare the stability system for both directions with the Casa R structure.

This building located in Melbourne VIC, Australia, designed by BBK. The overall structure of the building is made of concrete and timber. Below figure has shown external and internal appearance.

External of building

Figure 10 external and internal of Doll’s House (EXPO, 2018)

To comparation with bracing system of Casa R, Doll’s house is portal frame system by timber. In this building members included beams and columns, through them connected with wall provide a residential stability strength and for all direction wind load will be resisted by shear wall. Below figure has shown stability systems.

Timber beam

Timber columns

Shear wall

Figure 11 Stability system of Doll’s House

7.    For the chosen building in Task 6, determine the Vr based on AS1170.2. Ensure that you detail all assumptions/factors that you have used. (you only need to calculate the Vr which is the regional wind speed. So, do not consider shielding, terrain, topography etc.).

1. The building of Doll’s house located Northcote, VIC Australia, hence According to figure 12 wind regions, the Doll’s house belongs to region A5.

Figure 12 wind regions (Standard, 2002)

2. According to figure 13 building importance level of Doll’s house which is Level 1, it means the annual probability of exceedance of wind is non-cyclonic 1:100.

Figure 13 Building importance Level (Australia, 2016)

3. refer to table 3.1 of AS 1170.2, it can find out regional wind speeds of this area is V100 = 41m/s.

Figure 14 regional wind speeds (Standard, 2002)

8.    Choose a structural member that is subject to bending action and indicate locations of maximum compression and tension given the shape of the member.

Steel bearer Beam member

Figure 15 maximum compression and maximum tension in beam

9.    Consider the connection between the rafter and the column. Discuss the load path through the connection (show a photo of your connection).

Below the figure has shown the connection that are the rafters were welded with the columns.

Transfer loads from the rafter to the beam and column. Transfer loads from the column to the pad footing and then to the ground.

Figure 16 rafters were welded with columns

10.                       Identify two of the materials used for structural purposes. Comment on why they were chosen and discuss how the engineer has managed any issue associated with the material.

Steel:

1. Why they were chosen steel, because it is:

• Cost effectiveness
• Speedy construction
• Service integration
• Quality and safety
• Sustainability

As well as, the building was built on a slope that required strong support and the ability to withstand the wind loads, the engineers chose steel as the material, such as, columns, bracings, beams.

2. There are problems that engineer has managed:

• Corrosion:

For the corrosive treatment of steel materials, the engineer can work with reputable metal construction suppliers because they can make recommendations and recommendations based on their years of experience in providing buildings for building location and applications. In addition, they are metal corrosion experts who can easily spot areas where the choice of materials in the building design can lead to bimetallic or environmental corrosion. Engineer will also get the highest quality materials and coating options and will continue to provide reference and assistance frameworks throughout the life of the building.

• Fatigue and Fracture:

Engineer can consider to regular maintenance and inspection, or impact test during production to prevent material breakage or damage.

• Poor fire protection:

The material of steel is not good for fire protection; hence engineer can use thin film intumescent coatings covered with steel to resist fire.

Concrete:

1. Why they were chosen concrete, because it is:

• The deterioration of concrete is not appreciable with age.
• Concrete makes a building fire-safe due to its noncombustible nature.
• Concrete can withstand high temperatures.
• Concrete is resistant to wind and water. Therefore, it is very useful in storm shelters.
• As a soundproofing material cinder concrete could be used.

When engineers consider the suitability of the foundation, using concrete as the foundation is a good choice. Because concrete can be poured into any size or shape, and effectively incorporated into steel, the entire foundation becomes stronger and more stable.

2. There are problems that engineer has managed:

• Scaling:

To scaling of concrete, engineer need to avoid don’t use salt or other chemicals on concrete during the winter.

• Cracking

To cracking of concrete, engineer can do this in the following 4 methods:

1. Remove topsoil, soft spots and organic material in the subgrade
2. Compact all loose soil underneath the concrete slab
3. Slope the subgrade for proper drainage
4. Design a flexible concrete pavement that could accommodate load and movement

11.                       Sketch the type of footing system that would most likely have been adopted to support the structure at ground level. Draw a cross section of this footing labelling necessary construction elements. Sketch one alternate footing systems that could have being used by the Casa R building. How would the footing system of the Casa R building differ if the structure was made from timber?

(1) The pad footing would be most likely adopted to support the structure at ground level. Figure has shown the pad footing detail at ground level.

Figure 17 pad footing at ground level

(2) below of figure has shown that a cross section of pad footing and labelled construction elements.

Figure 18 a cross section of pad footing

(3) Raft footing systems that can have being used by the Casa R building, because raft footing consists of one footing usually placed under the entire building area. They are used when soil bearing capacity is low, column loads are heavy and differential settlement for single footing are very large or must be reduced. Below of figure has shown raft footing details.

Figure 19 raft footing

(4) when structure is made by timber that will bring less burden to the footing than steel structure, it means timber structure is more lightweight. However, the connection between timber structure with footing that is more complicated and difficult than steel. For example, steel structure able to be using bolt or weld to connect with footing, while timber structure which require stone or gravel to prevent timber from termite or rot.

12.                       Considering the serviceability criteria of deflection, identify the limits for all relevant structural components of the Casa R. Use the limits prescribed by the Australian Standards.

 Element Serviceability parameter Element response Metal roof cladding Residual deformation Span/600 but <0.5 Mid-span deflection Span/120 Roof members (trusses, rafters, etc.) Mid-span deflection Span/300 Ceilings with plaster finish Mid-span deflection Span/200 Columns Deflection at top Height/500 Portal frames (frame racking action) Deflection at top Spacing/200 Walls—General (face loaded) Mid-height deflection Height/150 Fixed glazing systems Deflection 2 × glass clearance Beams where line-of-sight is along invert Mid-span deflection Span/500 Floor joists/beams Mid-span deflection Span/300 Handrails—Post and rail system Mid-span system deflection Height/60 + Span/240

Figure 20 Suggested serviceability limit state criteria (Standard™, 2002)

References

• Australia, C. o. (2016). NCC, volume one. Austraila : The Australian Building Codes Board.
• EXPO, A. (2018). Gorgeous Doll’s House extension transforms a drafty bungalow into an energy-efficient home. Retrieved from THE ONLINE ARCHITECTURE AND DESIGN EXHIBITION: http://projects.archiexpo.com/project-27477.html
• SAIGOLBAL. (2002). Structural design actions. In Australian/New Zealand Standard™ (p. 9).
• Santibañez, D. (2018, August 10). Casa R / Felipe Lagos. Retrieved from the world’s most visited architecture website: https://www.archdaily.com/899874/casa-r-felipe-lagos
• Standard, A. Z. (2002). WIND REGIONS. In Wind actions (p. 14).
• Standard™, A. Z. (2002). SUGGESTED SERVICEABILITY LIMIT STATE CRITERIA. In General principles (p. 28).

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