Brock Commons House: The Tallest Wood Construction In North America

Dead Load

Provide a summary of the structure detailing the design philosophy of the structure (consider aesthetics, function and design statements).Annotate on pictures of the structure all elements that are to be considered in the calculation of the structure dead load. For each element, also label the material used (you may need to use at least 3 different pictures to show all elements).What is the total dead load of this structure? Detail all calculations and clearly state and summarise the assumptions that you have made. 

Create a live loading plan for a typical floor layout (i.e. floors 2-17) for the building. The plan should consist of a floor plan with different areas highlighted based on different usage and a legend indicating the use and the associated design pressure based on AS1170.1.Determine the Vr for the structure based on AS1170.2. You may assume the structure was built on Bond University Campus. 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.)

The structure is built primarily from concrete, timber and steel. Evaluate how issues common to the steel and concrete were/should have been managed. (Hint: you could create a list of issues for each material and then detail the appropriate management strategy for each) he design of a building made primary from timber often requires extensive management strategies around the control of fire and durability. What strategies were employed by the designers of this building and identify if there are other solutions available for the management/design of the above issues.

There are two different types of columns that are used in this structure. The two types are GLT (glue laminated timber) and PSL (parallel strand lumber). Evaluate the reasoning behind the engineer choosing to use two different types of columns? Structural elements and systems

Draw the load path for a person standing on the roof. Use both plan and elevation views.Draw the wind load path.
How is stability provided to the building? You must consider both primary directions.Evaluate how the structure would be different if concrete shear walls were not used. 

If the earthquake loading became the critical loading case, suggest two earthquake design/management systems that could be realistically implemented into the structure.According to the plan of 2nd level, draw the tributary areas for each of the vertical elements (i.e.Consider the connection between the core walls and floor (slab). List and describe three considerations in the choice of connection (e.g. size/type of force, constructability). Then discuss the load path through the connection and identify the types of forces (e.g. tearing) in each element of the connection. 

Create an outline of the geotechnical tests that would have been conducted prior to the design and construction of the structure and footings. Outline the purpose of each test and how its result can impact on the design of the foundations.Identify the footing system of this structure. Draw a cross section (from the bottom of the 2nd floor slab to the bottom of the piles) of this footing and label necessary construction elements.

Considering the serviceability criteria of deflection, identify and calculate the limits for all relevant building components of the Brock Commons Tallwood House. Use the limits prescribed by the Australian Standards. (See Table C1 AS1170.0) Evaluate some of the ways that this structure may have integrated vibration management. It is known that creep, thermal actions and axial shortening are issues commonly experienced by tall buildings. Create a set of management strategies for these issues in the context. Most concrete manufactured today has some type of admixture added to it to increase its performance or constructability. Identify five different admixtures that can be added. For each admixture, describe its purpose and any drawbacks to using said admixture. 

The Brock Commons house has already been considered the tallest wood construction in the North America. The structure is 13-storey that is found in the Pointe-aux-Lièvre’s eco-neighborhood in the city of Quebec. The tall solid timber structure has been constructed on the podium made of concrete/.The structure is 134 feet in its height. The structure is unique by the fact that it is made up of entirely the solid wood(Su 2018). The wooden structure is found in the staircases and also in the shafts of the elevator.

The exterior walls and the cross are also made of the wooden components. The structure is a combination of the glulam beams and columns and also the CLT columns. The chance that has been created by the new, larger and the taller building made of wood has been recognized as an option that is viable in the country especially by the building and the design community(Al-Mukhtar, Khattab  and Alcover 2012). The process has been made possible by the evolution of the products of the woods. The approach and the philosophy of the entire project was basically to use the materials in the most recommended way that allowed for the achievement of the hybrid system of concrete cores and timber.

3a)Dead Load:

Assumption: It is assumed that slab to be non-suspended slab

Floor system = 0.75 kPa (assumed) x (6/2 + 4/2) x (5.6/2 + 4.4/2) = 18.75 kN Column = 0.45 x 0.4 x 4.75 x 24 = 20.52 kN Wall unit = 20 x 0.175 x (6/2 + 4/2) x 4.75 =   83.13 kN Overall = 121.4 kN

 3b)Second Storey:

 Dead Load

Slab = 0.15m (assumed) x 24 x (6/2 + 4/2) x (5.6/2 + 4.4/2) =                      90 kN Floor system = 0.75 kPa (assumed) x (6/2 + 4/2) x (5.6/2 + 4.4/2) =       18.75 kN Column = 0.45 x 0.4 x 3.46 x 24 =                                                                 15 kN wall system = 20 x 0.175 x (6/2 + 4/2) x (5.6/2 + 4.4/2) =                              60.55 Primary Beam = 24 x 0.6m x 0.8m x (6/2 + 4/2) =                      57.6 kN

Secondary Beam = 24 x 0.25 x 0.45 x (6/2 + 4/2) =                                    13.5 kN

Overall = 256.4 kN

LL = 4 KN//m2 (assumed) x (6/2 + 4/2) x (5.6/2 + 4.4/2) = 100 kN

2^nd upper or Third storey

(i) Dead Load

system Slab = 0.15m (assumed) x 24 x (6/2 + 4/2) x (5.6/2) = 51.4 kN Beam = 24 x 0.6m x 0.8m x 6 =  68.1 KN Floor system = 0.75 kPa (assumed) x (6/2 + 4/2) x (5.6/2) =  10.5 kN Column = 0.45 x 0.4 x 3.06 x 24 = 12.22 kN wall system = 20 x 0.175 x (6/2 + 4/2) x 3.06 =   54.55 kN Overall                                                                                              = 197.77 kN

Second Storey

(ii) Live Load: (2nd Upper Storey Rooms)

LL = 4 KN/m2 (assumed) x (6/2 + 4/2) x (5.6/2) = 50 kN

(2d) Roof Level:

Wall unit = 20 x 0.175 x 1.81 x (6/2 + 4/2) =32 kN  Dead Load service

= 0.75 kPa (assumed) x (5.6/2 + 4.4/2) x (6/2 + 4/2) =   18.75 kN

Overall = 53.75 kN

 Dead Loads  of roof = 0.75KN/m2 x 5 x 5 =  14.17

 Roof Materials kN = 1.5KN//m2 x 5 x 5     = 57.25 KN

Summation of Dead Load = 122.4 + 255.4 + 197.77 + 51.75  + 56.25 = 682.57 kN

Footing strip Size of 2m width (instead of 4m) x 4m (range Length) x .75mm thick

 Weight of Ground Footing Foundation = 24.0 x 2 x 4 x .75 =145.0 KN

 Soil Pressure force = 989.64 / (2.0 x 4.0) = 124.71 KN//m2

5. Dynamic load calculation

The provided spacing is ta the interval of 20feet

=20ft

=20x0.305

=6.1m

The height of the colum will be taken as 5.9 metres

The pitch of the roof will bwe taken as 27 degrees

H(roof)=5.9+6.63X TAN 27

=9.28M.

The average height will be calculated as

h=5.9+9.28-5.9/2=7.6m

The working life obtained becomes 50 years

The region becomes A4

The equivalent V_R=45m/s for the ultimate loading. And also 37m/s for serviceability..

4. Live load plan 

Figure 5typical floor plan(Willebrands 2017)

Taking the prime equation

V_S=V_txM_dxM_ZxM_t

M_t=1.0

The value of the velocity is taken as 45x0.95x1.0x1.0x1.0

V=42.75m/s

This equation will completely define the pressure of the wind

=37x0.97

=35.15m/assuming that the density of the air remain the same as 1.2kg/m3 and also taking the factor of the dynamic loading to be constant that is;

C=1.0

P=0.5x1.2x42.75x42.75x1/1000

=1.097(This is described as Ultimate limit)

The internal pressure will translates into the cross wind

K=0.8 for the cross wind.

Pressure becomes; 1.097x (-0.24) remember -0.24 was obtained from -0.3x0.8

P=-1.61kN/m.

For upward slope

P=-.4x1.097

=-0.44kPa

6. Durability

Steel is normally affected by the process of the corrosion. This can be controlled by the use of the galvanic corrosion protection. The concrete may be affected by improper compaction and other ASR effects. The effects of ASR(Alkali Silica Reaction) can be prevented using pozzolanic admixtures. Timber is affected by exposure to water. This should be minimized as low as possible.

7. Fire protection.

The building has employed the use of the timber with the thick layer. This thick layer normally chars to provide natural protection against protection of fire. The building also enjoys access to the fire extinguishers and standpipes(Willebrands, O., 2017)..

8. Reasoning behind GLT and PSL

The GLT has excellent strength to weight ratio

Third Storey

It is durable

It poses proper flexibility to size and shape

It has high dimensional stability and strength besides being locally available.

Parallel strand lumber is suited for use in the places where high bending stress is needed.

It is also very attractive with proper surface finish. 

Building Stability

In order to ensure proper stability, the building has been supplied with a frame work of properly fixed columns and also systems of beams with joints that ere stiff and cable of taking moments.

12. Use of concrete shear wall

The shear walls are basically used in the provision of the lateral resistance and stiffness. When wood is exposed to a lot of moisture, it decays up. This is also true when it comes into the contact with the ground. Also use of the nails weakens the strength of the wood. If shear walls made from the concrete are used instead, the structural strength of the building will improve. When the shear wall are not used, the structure will utilize other alternatives that include the following;

• Moment resisting frames: These are girders and columns that are fixed with the semi rigid connections.)
• Braced Walls: They have single diagonals. This can be used in lace of the shear walls.

Use of the shear wall will give perfect straightness of the RC walls as another advantage.

13. .Earthquake

Most of the engineers and the designers normally rely on the previously published reports on the earthquake to improve their design work. The reports have indicated that proper design will easily assist in the resistance of the seismic loading. In order to improve the resistance, the follow b in design criteria must be followed(Teshnizi, Pilon, Storey,  Lopez and Froese 2018).Thorough foundation survey or research should be conducted in the sand that may be loose, clay locations and other silty places. Much consideration should be given to the seismic waves or flooding

The cantilevers like parapets and towers are known to be undumped elements. These components should be given some high coefficient of the seismic design. The accelerations that are inclined vertically should be given much consideration.

14. Tributary in vertical elements.

Shown in shaded parts.

Given: Live Load, L=50 psf Dead Load, D= 70 psf 1. Girder BC 1-1 Tributary area, A T = 40 x 15 = 600 sq ft Influence area, AI = 2 A T = 2 x 600 = 1200 sq ft Live load reduction = 0.25 + [15 / √ (AI) ] = 0.25 + [15 / √ (1200)] = 0.25 + 0.433 =0.683 Amplified loads per linear foot: Dead Load = 1.2 (70 psf) (15 ft) = 1260 plf Live Load = 1.6 (0.683)(50 psf) (15 ft) = 819.6 plf Wu = 1.2 D + 1.6 L = 1260 + 819.6 = 2079.6 plf = 2.08 k/ft

Live Load

The materials component, the angle of inclination, the period of treatment of the concrete. The thickness of the slab especially suspended one will give wider crack at the point of the connection. The light slab though suspenede gives smaller crack during the testing period.

Special requirement on the concrete finish will definitely influence the type of the slab wall connection. There is lots of demand for high quality formwork for the case of the fair-faced concrete.

Finally the involvements of other techniques for the construction will mean inclusion or use of specific type of connection.

16. Geotechnical testing

Direct Shear Test

This is a laboratory test that is used basically by the geotechnical engineers in the measurements of the shear strength of the soil. The specimen is placed in a shear box with the two stack rings that hold the sample. The contact that exists between the two rings is taken as the mid-height of the sample. The other soil characteristics that are determined include the soil cohesion and the angle of the internal friction.

Proctor Compaction Test

 This is a laboratory technique for measuring the maximum moisture content of the soil type. These lab tests for the most part comprise of compacting soil at realized dampness content into a tube shaped form of standard measurements utilizing a compactive exertion of controlled size. The soil is generally compacted into the form to a specific measure of equivalent layers, each accepting various blows from a standard weighted mallet at a predetermined tallness. This procedure is then rehashed for different dampness substance and the dry densities are resolved for each. The graphical relationship of the dry thickness to dampness content is then plotted to set up the compaction bend. The most extreme dry thickness is at last acquired from the pinnacle purpose of the compaction bend and its relating dampness content, otherwise called the ideal dampness content(Taylor 2014).

Triaxial shear test.

This method is used to measure the mechanical properties of the soil. In this test, the soil sample is subjected to stress. This is regularly accomplished by setting the example between two parallel platens which apply worry in one (generally vertical) heading, and applying liquid weight to the example to apply worry in the opposite ways. (Testing mechanical assembly which permits use of various dimensions of worry in every one of three symmetrical headings are talked about underneath, under "Genuine Triaxial test".)

R-Value testing

The R-Value test[1] measures the reaction of a compacted test of soil or total to a vertically connected weight under particular conditions. This test is utilized by Caltrans for asphalt configuration, supplanting the California bearing proportion test. Numerous different organizations have received the California asphalt plan technique, and indicate R-Value testing for subgrade soils and street totals.

Roof Level

Sieve Analysis

A sifter investigation (or degree test) is a training or strategy utilized (ordinarily utilized in structural designing) to evaluate the molecule measure conveyance (additionally called degree) of a granular material by enabling the material to go through a progression of strainers of continuously littler work size and gauging the measure of material that is ceased by each strainer as a small amount of the entire mass.

The size circulation is regularly of basic significance to the manner in which the material performs being used. A sifter investigation can be performed on non-natural or natural granular materials including sands, smashed shake, soil, stone, feldspars, coal, soil, an extensive variety of produced powders, grain and seeds, down to a base size contingent upon the correct strategy. Being such a straightforward method of molecule estimating, it is likely the most well-known.

17. Footing system

The footing system refers to the component that assists in the transfer of the load from the building to the laid foundation. The building that is under the study has employed the use of the shallow rooting system that is fastened using the screw and bolts on the ground.

Deflection

C1 AS1170.0) stipulates the limiting deflections under two heads as given below:

(a) The maximum deflection should not go beyond span/250 due to all loads including the effects of temperatures, shrinkage and creep and measured from the as-cast level of the supports of roof ,floor and all other horizontal members.

(b)  The highest deflection should not normally exceed the lesser of span/350 or20 mm including the effects of temperature, creep and shrinkage occurring after erection of partitions and the application of finishes.It is a must  that both the requirements are to be fulfilled for each structure. 

The checking of the two requirements is done after designing the members. Despite the fact that, the revision of the structural design has to be confirmed on details to ensure that it does not fails to meet any one of the two or both the requirements.By avoiding this, C1 AS1170.0) the member initial dimensions are assumed as recommended by guideline thus general satisfaction of the deflection limits.  Illustration in the Clause20 indicates various spans to effective depth ratios and cl. 24.5 suggests limiting cross section of 

beams, a relation of  b  and  d of the members, hence achieving lateral stability. They are indicated  below:

(A)  For the deflection requirements

Different basic span figures to effective ratios of depth  for three various support conditions are prescribed for spans up to 10 m, in which the modification should be done under any or all of the four different situations:

• In the cases for spans that are beyond 10 m,
• In the case of the consideration of the amount and the stress of tension steel reinforcement,
• when putting into consideration the amount of compression 
• In the casesfor flanged beams.Any beam lateral stability depends upon the ratio of slenderness and the support situations. Accordingly section of the code that stipulates the following

(i)   In case of  simply supported and continuous beams, the clear distance between the lateral restraints shall be beyond the lesser of 60b or 250b2/d, in which  d  is the effective depth and  b  refers to compression breath face lateral restraints  between the  midway.

(ii)  In the case of  dealing with cantilever beams, the clear distance from the free end of the cantilever to the lateral restraint shall not go beyond  the lesser of 25b  or  100b2/d.

C1 AS1170.0) prescribes computation steps of the short-term deflection. The usual methods for elastic deflections  using  the  short-term  modulus  of  elasticity  of  concrete    Ec      and effective moment of inertia  Ieff  given by the following equation as recommended by the code In the continuous beams, therefore ,modification of  Ir,  Igr   and  Mr  values are done as in the equation below;

Wind Load

? X 1 + X 2 ?X e   =

q1  ?

+  (1 - q1 ) X o

2 ?

where Xe =  modified value of X,

X1, X2   = values of X at the supports,Xo = refers to value of X at mid span,

q1 = coefficient shown in the table below  and

X = value of Ir, Igr  or  Mr   as appropriate. coefficient  table

k1	0.5 or less	0.6	0.7	0.8	0.9	1.0	1.1	1.2	1.3	1.4
k2	0	0.03	0.08	0.16	0.30	0.50	0.73	0.91	0.97	1.0

Remember:  k2    is given by (M1  + M2)/(MF1  + MF2), i.e. M1  and M2 = support moments, and MF1 and MF2 = fixed end moments.

Deflection due to Shrinkage

C1 AS1170.0)  indicates the method of calculating the I.e.  k3   is a constant which is 0.5 for cantilevers, 0.125 for simply supported members,  0.086  for  members  continuous  at  one  end,  and  0.063  for  fully

using  compressive  concrete moment and  tensile  steel  about  the neutral axis (distance is assumed to be    x     from the bottom of the flange as illustrated  below:

2234(100)(50 + x )  = (23.255)(1383)(450 - x ) or       x  = 12.92 mm which gives   x = 112.92 mm. Accordingly,      z   =   lever arm   =   d – x/3   =

512.36  mm.

Ir   = 2234(100)3/12  + 2234(100)(62.92)2 + 23.255(1383)(550 – 112.92)2

+ 300(12.92)3/3 = 7.214(109)  mm4

Mr  = 82.96 kNm  (see Step 2)

M  = wperm l2/8 = 9.3(8)(8)/8 = 74.4  kNm.0.918 I 

   ≤  Ief≤  Igr,  Ieff   should be equivalent to  Igr.  So,  Ieff   =  Igr   =

11.384(109mm The two requirements in regard to the deflection control are given in parts. Therefore they are confirmed as follows

Confirmation of the first requirement Highest allowable deflection  = 8000/250  = 32  mm

The actual final deflection due to all loads

The highest allowable deflection is the lower of span/350 or 20 mm. Here, span/350 = 22.86 mm. Hence, the highest allowable deflection = 20 mm. The actual final deflection = 1.948  + 2.64 4 + 3.118   = 7.706 mm  < 20  mm. thus, o.k.

Thus, both the requirements of C1 AS1170.0)  as well as as given in section are met

The design of the building has incorporated several  management strategies to control the floor vibrations.

Reduction of effects

There have been alterations that lower the annoyance that are linked to the vibrations. The noise level has been eliminated by the removal of the articles that are known to vibrate noticeably.

Relocation of the activities

The building has employed the techniques of relocation of the vibration sources. This has included the relocation of the area of the aerobic exercise from the top floor to the ground floor. The walking vibrations have been controlled by having the specific areas near the columns.

Stiffening

The vibration due to the walking and rhythmic activities in the building has been reduced through increase of the stiffness of the floor. The structure has incorporated new columns between the already existing columns from the affected floor to the foundation down. The stiffening in the structure has also been achieved using transverse methods of blocking or decking.

 Isolation

The floor vibration that results from the machinery components within the building has been reduced by placing them on the soft springs.

The creep refers to the deformation on the structure as a result of the imposed stress. This may results from the self-weight of the elememt.The building has sorted out the creep effects through load reduction(Connolly, Loss, Iqbal and Tannert 2012)

Corrosion Protection

The structural members of the used timber have had increases surface area hence reduced effects vof the creep. The water cement ratio of the building especially in the foundation was made as little as possible to reduce the creeping effect.

The heat flow within the building takes place in three, two or one dimension. In most of the real situations the heat flow takes place through three dimensions. The transfer of the heat takes place through each of the following means

Conduction is the flow of heat via a material through direct molecular contact. This particular contact will take place within two objects that are in contact(Wood 2014).

Convection is transfer of heat by the movement of the molecular particles of the liquid or gas. Radiation is the heat transfer by the electromagnetic radiations.Since conduction is regarded as the primary heat transfer means,the material has incorporated the use of low density insulation materials including glass of 2500kg/m3.

Air Leakage

The warm air that is genetrated from within the building rises and is quickly replaced with the cold air from outside.During the warm weather,the leaking  air is replaced with hot air that must be dehumified and cooled.The structural component of the building has incorporated mechanism that allows for the proper exchange of air or ventilation(Calderon 2018).

Concrete admixtures

Concrete admixtures are normally added to the batch of the concrete before mixing the concrete. The admixtures of the concretes tend to improve the quality of the concrete, retardation and manageability(Poirier, Moudgil, Fallahi, Staub and Tannert 2016).

1. Set retarding Admixtures

These are normally added to delay the chemical reactions that occur when settling process of the concrete starts. It is commonly used in the reduction of the high temperature effects that can possibly lead to the faster setting of the concrete.

Advantages

It reduces additional costs in the placement of the new concrete batch

They help in the reduction of the cracking that results from the form deflection.

Disadvantages

Some retarders normally play a major role in the water reduction and may keep some air as well in the concrete.

2. Air-Entrainment

An entrained concrete normally increase the durability of the concrete in relation to the freeze-thaw properties. This type of the admixture produces a concrete that is more workable.

Advantages

The degree of workability is high

The durability is high as well

The cycles of wetting and drying are very high.

Disadvantages

The ratio of the entrained air and compressed strength normally vary and is difficult to maintain.

3. Water reducing concrete admixtures

These are chemical products that when added to the concrete may create a desired slump at a lower ratio of the water cement. They are normally used to obtain a specific strength.

Advantages

Helps in the improvement of the properties of the concrete especially in the decks of the bridge.

Disadvantages

Low cement content tend to compromise the strength of the structure made from such compounds.

4. The Shrinkage Reducing

These are chemical substances that are added during the initial mixing of the concrete.

Advantages

It reduces the long term and early shrinkage

It is suitable in the cases where shrinkage cracking leads to the problems of durability

Disadvantages

It may sometimes lead to the reduction of the strength of the compound

5. Super plasticizers

The core reason for the use of super plasticizers is to ensure that there is production of a flowing concrete that has proper slump

Advantages

It improves the workability of the concrete.

Disadvantages

It is associated with the lump loss.

References

Al-Mukhtar, M., Khattab, S. and Alcover, J.F., 2012. Microstructure and geotechnical properties of lime-treated expansive clayey soil. Engineering Geology, 139, pp.17-27.

Calderon, F., 2018. Quality control and quality assurance in hybrid mass timber high-rise construction: a case study of the Brock Commons (Doctoral dissertation, University of British Columbia).

Connolly, T., Loss, C., Iqbal, A. and Tannert, T, 2012. Feasibility study of mass-timber cores for the UBC Brock Commons Tallwood Building.

Fast, P. and Jackson, R., 2017, September. Case Study: University of British Columbia’s 18-storey TallWood House at Brock Commons. In IABSE Symposium Report (Vol. 109, No. 28, pp. 2314-2321). International Association for Bridge and Structural Engineering.

Mohammad, M., Jones, R., Whelan, M. and Coxford, R.2016, CANADA’S TALL WOOD BUILDINGS DEMONSTRATION PROJECTS.

Poirier, E., Moudgil, M., Fallahi, A., Staub-French, S. and Tannert, T., 2016. Design and construction of a 53-meter-tall timber building at the university of British Columbia. In Proceedings of the World Conference on Timber Engineering, Vienna, Austria.

Su, J.Z., 2018. FIRE SAFETY OF CLT BUILDINGS IN CANADA. Wood and Fiber Science, pp.102-109.

Taylor, R.E., 2014. Geotechnical centrifuge technology. CRC Press.

Teshnizi, Z., Pilon, A., Storey, S., Lopez, D. and Froese, T.M., 2018. Lessons Learned from Life Cycle Assessment and Life Cycle Costing of Two Residential Towers at the University of British Columbia.

Willebrands, O., 2017. Differential Vertical Shortening in Timber-Concrete High-rise Structures.

Wood, D.M., 2014. Geotechnical modelling. CRC Press.