ARCH1162 Structures and Construction 1 Assessment Answer

Introduction

The Gordon project is to be designed and constructed as a two-story building. Imposed and dead loads are acting in structure. There shall be many materials including furniture, and cabinets in the house, and all these loads are to be considered for the structural design of this timber structure.

The structural members includes footings,rafters,battens,bracings,bearers, joists ,purlins,top plate,bottom plate and noggins etc. The timber materials can be used for wall and roof framing, The framing shall be a timber frame with wooden materials. The slab shall be composite or concrete. The timber sections available

All the tension and compression member shall be designed safely without failure and compression members may fail due to compressive stress and compression member may fail due to yielding. Buckling occurs when maximum stress crosses at the yielding point. This is mainly due to the deflection of the structural member. Timber is considered a traditional material for building roofs and beyond. The roof material is the main choice for home builders and sole builders irrespective of traditional or contemporary styles. The popularity of timber as roof material is widely considered and generally easy to start the work and has excellent properties including strength to weight ratio and economic importance. The material is aesthetically appealing and considered bio-degradable and environmentally friendly. The covering of the roof is a major component in defining the proper roof form, and timber is a plentiful and suitable building material. The pitch degree is typically established by covering features that call for a steeper pitch, which could increase the likelihood of ingress with gaps and a pitch of about 50 degrees, clay tiles at 45 degrees, thick slates, and stone flags, which may be used in this situation. The size of the timber elements and roof pitch are not tightly governed by the typical covering borne on laths. When compared to clay roof tiles, the size of the wood stone slates is far larger than what is needed to support the structure's sturdy rafters.

Structure

The roof and the supported covering it provides for the building are the fundamental timber component. A flat roof is the most affordable and straightforward solution from the perspective of builders. Due to its elegant appearance, this form of roof is appealing to pitched roofs.

A flat roof's finish is constrained. The horizontal timber elements or beams in a straightforward pitched timber roof slope in the direction of the rafters, while the purlin supports run parallel to the roof ridge. The rafters are typically notched with the help of birdsmouth to fit over the purlin members to prevent the roof from being blown off by the wind. The mild steel straps that are often used to bind frames to the top of the masonry wall that supports the rafters are slotted over the timber wall plate.

Rafters are notched to the eaves of the timber structure, and purlins are bolted to the posts.

Roof truss

The lower ends of the rafters can be connected to the eaves within the timber beam to construct triangular structures that can span a great distance between the support and the roof.

The rafters and wood beams are connected to avoid splaying.

The current way of building prefabricated timber trusses uses this approach as opposed to the straightforward traditional method of placing individual timber lengths.

The collected knowledge of triangle-shaped structures allows the use of timber trussed rafters for basic spans without internal supporting walls.

Elevation views in structure

The loads from roof and the slabs are directly transferred to footing

Uniformly distributed load transfer in structure

SLAB LOADING

Calculation Dead load, G and Live load, Q 

G = r * slab thickness + superimposed dead load 

=24∗0.2+1=24∗0.2+1

=5.8=5.8

kPa 

Q = 3.0 kPa

Deflection Check according to AS3600 Clause 9.4.4.1 

ΔLef∆Lef

= 1/250 (Table 2.3.2) 

EcEc

= 32 MPa 

kcs=2kcs=2

Fd.ef=Fd.ef=

(1+kcs)G+(Ψs+kcsΨl)Q1+kcsG+Ψs+kcsΨlQ

=

(1+2)5.8+(0.7+2(0.4))31+25.8+0.7+2(0.4)3

=21.9*10³ N/mm² 

Lefd≤k3k4⎛⎝⎜(ΔLef)1000EcFd.ef⎞⎠⎟13Lefd≤k3k4∆Lef1000EcFd.ef13

4700d≤1∗2.95((1250)1000∗32∗10621.9∗103)134700d≤1∗2.9512501000∗32∗10621.9∗10313

88.45mm≤d88.45mm≤d

Cover = 20 (AS3600, Table 4.3 & Table 4.10.3.2) 

ΦΦ

= 12 

D=88.45+cover+0.5∗ΦD=88.45+cover+0.5∗Φ

D=88.45+20+0.5∗12D=88.45+20+0.5∗12

D=114.5mmD=114.5mm

Therefore 200mm slab is OK 

SLAB THICKNESS TO BE PROVIDED IS 200 MM

Truss loadings in roof

Load transfer through slabs

 

Complete view of structure

Materials for construction

Materials

Table 2.1 - Material Properties - Summary

4000Psi	Concrete	24855.58	0.2	23.5631	Fc=27.58 MPa
Timber	Other	11000.58	0.3	0

Frame Sections

Table 2.2 - Frame Sections - Summary

Name		Material		Shape
Batten timber		Timber		General
rafter beam		Timber		General
timber beam 150 x 200		Timber		General
Shell SectionsStory2	B54		78		Beam		750	rafter beam	N/A	500
Story2	B55		79		Beam		750	rafter beam	N/A	500
Story2	B56		80		Beam		750	rafter beam	N/A	500
Story2	B57		81		Beam		750	rafter beam	N/A	500
Story2	B58		82		Beam		750	rafter beam	N/A	500

Base reaction due to loads in structure

Loading on clay roof tiles

Individual length of member – 1.155 m and approximated to 2.3 (considering both sides

Width of the member measured from side elvation – 6.000 m

Clay density is taken as 57.4 kg/m2

Batten and rafter profile

Loads acting in structure

The tile load in roof which is acting on rafter is T1 UDLCFT, T1 = 57.4 kg/m2 x 9.81/1000 x (0.25 + 0.75/2) m = 0.352kN/m

UDLCLT, T2 = 57.4 kg/m2 x 9.81/1000 x 0.75 m = 0.422 kN/

Loads acting in batten

Size of batten – 0.035 x 0.035 m

Quantity of batten is no – 8 in either side

Density of material – 770 kg/m3

Load on batten is 770kg/m3 x 9.81/1000 x 0.035 x 0.035 is 0.009 kn

This load is atcing over spacing of structure 0.75 m = 0.75 x0.009 = 0.007 kn

Tota load on each batten = 8 x0.007 = 0.056kN

Load converted as UDL is 0.024kn/m when the total load is divided by batten spacing

Loads in rafter

Size of rafter – 0.125 x 0.050 m

Total quantity of rafter – 9 nos

Density of material – 770 kg/m3

Uniformly distributed load acting in rafter

= 770kg/m3 x 9.81/1000 x 0.125 x 0.050

= 0.047 kN/m

Loads on struts

Size of struts – 0.125 m x 0.050 m

Maximum loads in strut is calculated as 770 kg/m3 x 9.81/1000 x 0.125 m x 0.050 m x 0.577m = 0.027 kN/m

Load distribution diagram on roof

Beam section is calculated and taken as 150 x 200 mm

Length of the beam is 2 m

Self weight of beam is calculated as

0.15 x0.2 x 770 kg/m3 x 9.81/1000 x = 0.227 kN/m

Total udl in roof structure = beam udl+rafterudl+battenudl = 0.227+0.352+0.024+0.047+0.047 = 0.697 Kn/m

THIS SHALL BE FACTORED

By converting UDL to point load

PLA = wL/ 2 = 0.697×2.300 / 2 = 0.802 kN

Point Loads applied on rafters 0.802 at support and 0.027 at centre

Loads applied on beams

Loads on beam considering T2

TOTAL LOAD SINCLUDING BEAMS,UDL,RAFTERS AND SELF WEIGHT OF STRUCTURE = 0.767 KN/M

BY CONVERTING IT INTO POINT LOAD

wL/2 = 0.767×2.300/ 2 = 0.882 Kn

Loads applied on rafters and beams

Considering equilibrium of moment equal to o

−0.882 (2)−0.047 (2)( 2 2)−1.791(1)+VB (2)

Vb =Va = - 1.82Kn

For simple span timber structure, the arrangement on site shall be considered for varying length as a traditional approach which is an easier and time-consuming approach resulting in optimized size and geometry of structural members. While considering the simple span structure the internal walls, timber rafters of truss specification can be of economical choice and there are results with accumulated knowledge for triangular structural members. The truss members have many advantages including better stress grading, spanning for large distances, joining under factory conditions, and economy, and can be delivered at right time with the specification. The trussed rafters are spaced at a distance of 750 m and the roofing material could be typically analyzed. As per structural efficiency of structural members including bracing shall be considered from top to bottom. The timber roof as traditional built material using roofing components or modern construction components can be verified with the help of an accredited and experienced structural engineer.

References

Loss C., Piazza M., Zonta D. (2012). “Analytical model to evaluate the equivalent viscous damping of timber structures with dowel-type fastener connections,” Proceedings of the 12th World Conference on Timber Engineering (12WCTE), Session 29 (Connections 9): 516-525, Auckland, New Zealand.

Loss C., Piazza M., Zonta D. (2013). “A new method to assess the seismic vulnerability of existing wood frame buildings,” Proceedings of the 2nd International Conference on Structural Health Assessment of Timber Structures, in Advanced Materials Research: 486-494, Trento, Italy. DOI: 10.4028/www.scientific.net/AMR.778.486.

Loss C., Piazza M., Zonta D. (2013). “Seismic design of timber buildings with a direct displacementbased design method,” Proceedings of the 2nd International Conference on Structures and Architecture, in Structures and Architecture: 98-105, Guimaraes, Portugal. DOI: 10.1201/b15267-14.

Loss C., Zonta D., Piazza M. (2013). “On Estimating the Seismic Displacement Capacity of Timber Portal-Frames”, Journal of Earthquake Engineering 17 (6): 879-901. DOI: 10.1080/13632469.2013.779333.

 Loss C., Piazza M., Zonta D. (2013b). “A new method to assess the seismic vulnerability of existing wood frame buildings,” Proceedings of the 2nd International Conference on Structural Health Assessment of Timber Structures, in Advanced Materials Research: 486-494, Trento, Italy. DOI: 10.4028/www.scientific.net/AMR.778.486.

Loss C., Piazza M., Zonta D. (2013c). “Seismic design of timber buildings with a direct displacementbased design method,” Proceedings of the 2nd International Conference on Structures and Architecture, in Structures and Architecture: 98-105, Guimaraes, Portugal. DOI: 10.1201/b15267-14.

Piazza M., Riggio M., Tomasi R., Giongo I. (2010). “Comparison of In Situ and Laboratory Testing for the Characterization of Old Timber Beams before and after Intervention” Gu, X., Song, X. editors, Advanced Materials Research Vols. 133-134: 1101-1106. URL:http://www.scientific.net/AMR.133- 134.1101.pdf.

Riggio M., Tomasi R., Piazza M. (2014). “Refurbishment of a Traditional Timber Floor with a Reversible Technique: The Importance of the Investigation Campaign for the Design and the Control of the Intervention”, International Journal of Architectural Heritage: Conservation, Analysis, and Restoration, 8(1): 74-93 (available online: 23 Apr 2012). DOI: 10.1080/15583058.2012.670364.

Zonta D., Loss C., Piazza M., Zanon P. (2011). “Direct Displacement-Based Design of glulam timber frame buildings”, Journal of Earthquake Engineering 15: 491-510. DOI: 10.1080/13632469.2010.495184.

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