Saturday, 27 September 2014

Preparing for UWC Day - Meeting the construction workers and planning a lunch.

 Update: See what happened on UWC Day http://uwcsea-dover-high-school-project-blog.blogspot.com/2014/11/uwc-day.html




1 October will be a day in which the whole UWCSEA Dover Campus will focus on the UWC values, with activities ranging from working with our service clients to dragon boating to hiking to environmental projects, etc. 

As part of this day, 44 students have chosen to engage with construction workers building our new high school block to get some insight into the lives of migrant workers in Singapore and prepare a lunch and celebration as way of a thank you...This is the first of a number of blog posts about this adventure.

Blog post by Sanah Budhraja - Grade 9



Today we were given the opportunity to go to the construction site in school and interview some of the workers. They were pleased to hear that we, the students, wanted to cook a meal for them on UWC day to show our appreciation and understanding of their laborious task.
Being service oriented is a trademark of UWC and therefore all workers have been provided with a room with tables, chairs, fans, a water-fountain and a vending machine. Since most of the workers only spoke Tamil, it was important that we took students who could interact with them and speak their language. 

We asked them what they missed the most about home and the general answer was family, friends, culture and food. When we inquired about the food they wanted, most of them were open to anything as they appreciated our gesture. But once the formality died down and the workers started really enjoying our company they told us that they would prefer a traditional meal consisting of rice, mixed vegetables and a dessert called ‘paisum’. For entertainment they said they would like tamil music and simple decorations.




As we were leaving we could tell the the construction workers seemed very excited and were looking forward to this day. These workers work 7 days a week earning around $14 dollars daily so they can support their family back home. They are truly deserving of this meal and we hope that on UWC day we can reconnect and remind them of their culture as well as show our appreciation.




Additional Reporting by Leila  Fuerst

Video and Photos by Sean Asahara Thio.


To a school that honors the unsung heroes; NGO's and volunteers, we sometimes forget those who work right on our campus. This UWC day, we aim to give back a little bit to the construction workers, unsung heroes who help to shape our campus, by preparing a meal for them, accompanied by music. But before we can cook for them, we needed to ask the workers what they wanted. During the meeting, despite our sometimes slightly sketchy translations, and the fact we never worked with them before, the workers were extremely open towards us, and helped us to organise food for them. They made it very clear that they would eat anything we would offer them, as they were pleased to be recognised. We are excited to continue working with them to make this the best experience for both the students and the workers.










Thursday, 25 September 2014

Post tensioned slab design - Its more interesting than it sounds (I hope!)

We have a lot to say Merci to the French for...the croissant, the baguette, the company that makes our lunch every day and the rather clever system of "post tension" construction we are using to build this building.

This system of post-tensioning was pioneered by a Mr Eugène Freyssinet  in 1933 for the foundation of a marine terminal in France and is now used extensively all over the world in bridges, elevated residential or commercial buildings, foundations, walls, and columns.

The site from above clearly showing the layout of the the metal strips...
Looking down at our construction site from above, it is possible that you may have noticed something a little unusual. The site is criss - crossed with a lines of shiny metal strips...

This strips of metal are actually hollow casings filled with wires and form part of the structural system which we use to hold up the building...This is called post tensioned construction, and is simply a method of producing prestressed concrete. 

The term prestressed is used to describe the process of introducing internal forces (or stresses) into the concrete elements during the construction process in order to counteract the external loads applied when the structure is put into actual use. This method of construction allows us to span large distances safely, whilst keeping the amount of concrete we use to a minimum.

For many of you, you can probably stop reading now as this is probably enough knowledge to anything but the most persistent of questions from the kindergarten... However if you would like to know more please continue...
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So lets start with the basics. The materials we use.  We make most of the building from concrete, which has incredible compressive strength (it cannot be squashed easily but you are welcome to try) but unfortunately it has limited tensile strength so is not every good at resisting large forces pulling on it... This means concrete on its own can only safely really be used to span small distances. 


We would like clear open space in the building, not filled with columns so we require spans over 12m in length. Sort of like lots of little bridges. For this we use a post-tensioned contruction method, first pioneered all those years ago.

Adding post-tensioned reinforcement instead of just steel bars (rebar) alone combines the action of reinforcing the tension zones with the advantages of compressing the concrete slab

With our type of post-tensioned construction, the silver strips seen criss crossing the construction site are actually high strength steel cables which are placed inside the concrete slab from end to end. Once in place concrete is poured directly on top of them and once this concrete  has set hard, they will be pulled tight and stretched (tensioned) by a machine to impart internal forces on the concrete.



When tensioned and locked-off to the anchors, this post-tensioned system increases the load the slab can bear and reduces "sag" by lifting the slab and counteracting forces that could be pushing down on the slab and cause it to crack. This allows our concrete spans to increase to over 12 metres of clear open space and the actual slab thickness by around 30cm a floor (6 floors) to decrease overall building height.



High and low points visible on the slab
We get additional benefits by installing the  post-tensioned reinforcement in a draped profile to create high and low points instead of running in a straight line. This routes the post-tensioned reinforcement through a high point over the slab's supports, and through a low point in between those supports. Now optimum efficiency cab beobtained because the post-tensioned reinforcement is appling forces directly in the tension zones, the concrete is compressed, and the post-tensioned reinforcement is creating an uplift force in the middle of the spans where it is needed the most.


Construction process

The basic element of a post-tensioning system is called a tendon. A post-tensioning tendon is made up of one or more pieces of prestressing steel wires of a diameter of 15.2mm, housed inside a galvanised metal tube, it is these covers that you see so visibly on the site 


A tendon has anchors on each end to transmit the forces into the structure. Long tendons may have intermediate anchors along their length to allow for stressing at construction joints. (see left and right)

To get an idea of the high strength of this type of steel, a typical steel strand used for post-tensioning will fail at about 243,000 psi. In contrast, a typical piece of reinforcing bar (rebar) will fail at around 60,000 psi. To be very sure we also send samples of this steel wiaway for independent testing before we start the work.



The handling and installation of the post-tensioning tendons does require special skill and knowledge. The prestreessing team will install the empty cases in the precise locations dictated by the engineer and shown on the post-tension field placement drawings.  These have to be very accurate

 When these empty tubes have been placed  the wires are inserted in the tubes. There is often a different number of wires in each tube as the specific forces applicable in each area are calculated.

In our elevated slab construction, the tendons typically are grouped in bundles in order to increase the spacing between tendons and improve the constructability of the slab.
After the concrete is placed, it must achieve proper strength before the tendons are tensioned. On our site this is 25 n/mm3 which is about 70% of the actual eventual strength of the concrete .









 The tensioning of the tendons, also known as the stressing operation, is achieved by using a hydraulic jack. At least one end of each tendon will have been installed with a length of prestressing steel cable protruding  from the edge of the slab; this is known as the stressing tail and unlike many other types of tail, this one is designed to be pulled....
 A plastic pocket former also will have been installed at this location to create a stressing pocket 
When the edge form and pocket former are removed, the strand tail and stressing pocket are exposed to allow the construction team to use the stressing jack to apply the force in the tendon.
The forces generated when the tendons are stressed are high enough to damage the structure or even cause injury to people working on the job if the installation and stressing are not done properly. 

Safety during stressing includes making sure that no one is working in the area where the tendon is being stressed. It is possible, but rare, for the cable to snap whilst being stressed.

The tensioning is done in 2 phases, firstly it is stressed  to a force equal to 25% of a strand's tensile strength.(on our site this is 15 MPa.) At this point spray paint is applied to provide a reference line, this is then held and checked for slippage and excessive elongation of the cable, which may indicate a problem with the integrity of the cable.

If everything seems stable then the jack is re-installed and stressing is carried out to the final stressing pressure - 59.6 MPa (a lot!)

As the tensioning is occurring, the steel is being elongated, and the concrete is being compressed. When the proper tensioning force is reached, the prestressing steel is anchored in place. The anchors are designed to provide a permanent mechanical connection, keeping the steel in tension, and the concrete in compression.
The steel elongation is measured and recorded for each tendon. This measurement is reviewed to determine and verify that the proper force exists in each tendon. Once the elongation measurements have been approved, the stressing tails can be cut off just inside the edge of the concrete slab, and the stressing pocket is filled with nonshrink grout (with a material strength of 30 MPa) to provide cover and protection over the end of the prestressing steel.
The act of stressing the tendons transfers force off of the formwork and into the tendons, which carry the force over to the columns or other supports. This means that the deck forms can be removed and cycled up to the next placement as soon as it is determined that all of the tendons in the current slab have been properly stressed.


The final product....



Stamped on the underside of the slab, its pretty important we dont accidentally damage those tendons.


The edge of the slab showing the tendons and the final thickness of the slab.


































Sunday, 24 August 2014

Our Green Building.


Our Green Building.

This week, our project was fortunate to be featured in the press in Singapore for some of its innovative energy efficient building features. Although as an organisation have been building high performance "green" buildings since the development of the greenmark platinum Tampines campus in 2009, most of our green building efforts are rather mundane and common sense and so rarely make the news.

This coverage centred on part of the 3rd floor of the building, which will the central support space for the school. We have partnered with ETH Zurich, Future Cities Lab to provide a space to try something a little bit new in. We hope lessons learnt as part of this experience will be replaceable through to other projects and perhaps influence other develop similar systems in offices of the future in line with our mission to educate for a sustainable future.

Straits Times.
Business Times
You can read more of the coverage here:

Today, Zaobao, Asia One, Eco Business, Blue and Green tomorrow tomorrow, UN Climate Action Programme
   
and of course on the beyond efficiency blog covering this part of the design.



You can track the progress of the green features of the new building here.

if you're interested, here's a quick summary of some the main factors for our continued development in this area, if you are really, really interested visit this page as I try explain in detail some of the problems that can be observed in the traditional way of the construction industry, if you are really, really, really interested, drop me an email  invite me for a pepperoni pizza somewhere nice for a chat!

- We try and understand the building as a system - looking for opportunities to use waste from one system in another and link the performance of various of the passive and active aspects of the building together.
- The way we are structured as an organisation leads to a huge advantage over others in terms of ownership of the Green building process. The functions of design, build and operation of our buildings and facilities all sit in one place
- We frame many building related decisions in terms of managing operating costs.
- We do not pay our teams of architects,engineers and other experts in terms of the %  of money they spend on the project.
- We have hard, measurable targets for most systems.
- We share the risk of efficiency decisions with the various expert disciplines.
- We standardise equipment and fittings to reduce our inventory.
- We simplify systems as much as we can and try and understand how the buildings are expected to perform throughout average day and throughout the year.

Green Buildings - Business as usual?


Building High Performance Buildings - Perhaps we need to look at a different approach?

As a individual we often make decisions based on efficiency and long term ownership. Value for money in the initial purchase and running costs is often the main reasons for major purchases.  A good example might be found in certain sectors of car industry.

A car company aims to design and manufacture a vehicle that will be cost effective to buy and use, they align internal departments to these targets and spend huge amounts on R+D and advertising aligning this ---- For the simple fact they know that many of there potential customers will use these measurable monetary facts and figures to assess and influence their purchase. If they dont do this, they may well go out of business. (you can even buy a hybrid Ferrari)

Ford would not get very far bringing a family car to market that was hugely inefficient with fuel consumption and expensive to maintain.. It may be one of the reason why the 6 wheeled car never really took off.

Contrast this approach with the building industry I know... We somehow forget these personal life lessons as soon as we are faced with a building project and end up paying a lot of money for something that will cost a small fortune to run. A building - The gift that keeps on taking...

So why is that? Well for a start not many people really know how much there real estate assets cost to own and run - Not in Singapore anyway, and those that do know aren't telling anyone - Some things are best to keep off the bosses radar...aren't they? To add to the fog, industry benchmarks seem almost nonexistent so comparison is rather tough, so we don't even know how much its supposed to cost to run - (at this point it is easy to imagine the secret meetings amongst Facilities managers in smokey bars conspiring to maintain the status quo :)) post occupancy surveys, feedback and accountability to designers based on performance figures are rare.

Design teams work in established silos of expertise with clear purpose but no real responsibility overlap.

Explained in simple terms - Architects design the building, Mechanical and Electrical (M+E) engineers design the lights, air conditioning and the other myriad of complex systems in a modern building, the structural engineer makes sure it doesn't fall down and the quantity surveyor works on the cost. Everyone tries to reduce the risk to themselves so concentrates on their systems and traditionally these teams are paid by a percentage of the money they manage to spend on the building as part of the overall project cost.

This approach has been successfully adopted for generations. These multidisciplinary team structures build most of the buildings we live and work in today.Obviously the system works.....

Sort of...

When you decide you want to build a high performance green building that costs less to build and less to operate, the traditional team systems and process starts to look like a sub plot from the emperor with his new clothes.

For you to be able to really squeeze out the savings, I would recommend an integrated and systems linked design approach. Despite the complex jargon, its thankfully mostly common sense.

A building is of course a complex interlinked system. Actions taken on aspect of the building are very likely to have a ripple (if not a wave!) effect on other parts of the building. The current traditional system of building cannot easily take advantage of the ripple effect between disciplines without strong leadership from the owner or the project leads.

Let me give you some examples of current practice cobbled together from projects I have seen, this contains many sweeping generalisations but I am sure will ring a few bells of those that have been exposed to this process:

The Architect designs the facade- they want the building to look great as that is what they do, however we all know (don't we?)  that orientation, facade design, selection of materials will ultimately affect the heat of the internal spaces.  Here in Singapore we need to buy air-conditioning systems to take this heat away. This is designed by the M+E consultant and is expensive to buy and will use up at least 60% of the electrical consumed by the final building. The owner may focus his comments the look of the building based on its aesthetics rather than its orientation in relation to the sun. Often the owner is just a landlord who may not really mind what the bills of future tenants are.

Once the architect has finished with the masterpiece he passes it to the M+E engineers who designs the systems.  For this work they will often use a combination of series of rule of thumb calculations, recommendation of  equipment suppliers, the last few projects they did,  the knowledge that he does not want to be liable on the finished building to fix a design issue that causes poor functionality, an estimation of redundancy needed and usage patterns and also the knowledge of the fact that he is ultimately paid for the fiscal quantity of their work.

The owner doesn't tell anyone the anticipated operating patterns and uses of the spaces passed the most basic information as he has paid the consultant team to do that for him hasn't he? (He wonders if Is a lab in a school the same as a research one? He doesn't realize a school is often shut for half the year and not often used at night, he wonders what sort of redundancy of systems does a school really? How many people are actually going to be in that specific room, What are the critical systems in a school ?)

Without this information  in a school context, the team search there minds for reminders from their own school experiences many decades ago to fill in the gaps and make assumptions of needs.( Somewhat dangerous if you went to a school like mine!)  Or possibly use figures from other spaces in other types of buildings thought to be similar.

The end product - A successfully delivered, great looking building for the next 40 years, perhaps with a high level of green building certification and a happy owner and consultant team ........but under the surface large amounts of redundant overcapacity and high fixed and operating costs...and of course missed opportunities..
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Now lets look at a simplified example of day in the life of a project that uses systems thinking to create green, high performance building..........

The building owners realises that current orientation of building and design of facade means the building will be very hot in the afternoon..decides function is more important than form - Phones the architect...

The Architect then works his magic and changes design of facade to minimize heat gain and reorients the building for maximum passive shading effect.  The result of his work is that most of the inside spaces can retain an ambient temperature and some of the windows now no longer need expensive aluminum sun shading and special heat rejecting glass...It also has the added advantages of allowing many of the spaces to now use daylight without the fear of glare and heat.

The M+E consultant sees this effort on reducing the internal temperature of the building and increasing the daylighting levels and works to reduces the capacity of the original air conditioning design by 30%.

The owner points out that the school is not often used at night for classes but loves maximum daylight in the day as it is linked to better performance of students,  the lighting design is then reduced by 20% (saving capital and operating costs)

As the air conditioning was such power hungry system, this orientation change decision ripples through the design. He also sees another linked opportunity - As he has cut the air con design by 30%, he can then reduce the electrical supply infrastructure accordingly, reducing distribution board capacity and ultimately getting get rid of a transformer. (again reducing capital and operating costs) The architect thanks him for the reduction in equipment and quickly turns the now redundant machine room into a car park saving valuable GFA.

The structural engineer notices this efforts and rather than being left out and reduces the structures and design of the roof as there is no longer any need for a big beam to hold up that heavy cooling tower that has just been eliminated from the roof.

The M+E consultant then sees another opportunity with the extra space gained back on the roof and reorients the cooling towers to maxmise air flow over them, making them more efficient and saving operating costs in water and power.

The Facilities Manger sees this overall electrical reduction and not wanting to be forgotten quickly goes back to the power company and re- negotiates a downsizing in the standing supply capacity they rent from the electrical supply company and reduce the extent of anticipated maintenance contracts with the air conditioning equipment suppliers...

The quantity surveyor watches it all and wonders why this method isn't used all the time.

The  project team report the significant saving in project budget that has been realised without any "value engineering" of the functionality (and safe in the fact that there fee is fixed) and the owner looks forward to reduced operating costs and in the case of not for profit schools, spending more money on education and not buildings..

If only it worked like that somewhere in the real world......

Perhaps it does :)

Track the green features of our building here


Saturday, 23 August 2014

Our Building "Green Building" Features


Our Building Green Features Last updated 14th August 2014

"Why, I must ask, does being 'green' mean building with glass and steel and concrete and then adding wind turbines, solar panels, water heaters, glass atria - all the paraphernalia of a new "green building industry" - to offset buildings that are inefficient in the first place? - HRH Prince Charles.

At UWCSEA we are great fans of BCA Greenmark  and as far as possible design and build our buildings to a platinum standard (version 4) but the pursuit of points always comes second to practical and common sense features.  This page will be constantly updated as we add and confirm features:
Linked from the following blog posts:

- Our Green Building
- Green Building - Business as usual


WATER

- All water fixtures and fittings will obtain the maximum 3 ticks under the WELS scheme.

- 1 rain water retention tank and 1 water detention/ retention tank for rainwater and air conditioning condensate water water tied to an ABC feature (its a surprise!)

Update 27/09/14 - We have now managed to firm up the design for the water system - Plumbing is usually rather dull but we have managed to add another system to use rainwater and AHU condensate waste water to run 100% of the flushing system of the building which makes it much more exciting.  We found the funding to do this work but studying the levels of the building again, surveying existing sewer lines in more detail and managing to tie to the existing lines using gravity. Saving us a big tank and ejector pump in the original proposal.

ENERGY

- Use of sunpipes for car park daylighting
- No landscape or other decorative lighting.
- Innovative air conditioning design for the office spaces
- Design for Exam hall roof to enable 100 % daylighting in the space.
- Natural ventilated toilets and staircases - No extraction fans.
- Combination sensor and timer systems for lights in infrequently occupied spaces




THE BUILDING
- Toilets and staircases externalized to aid natural ventilation
- ETTV <40 (work in progress)
- Exact North-South orientation with no windows on East and West facades
- Low window-to-wall ratio
- Extensive green walls




Changes made during the design and construction due to energy or operating cost concerns.

- Redesign to ensue the removal of sumps and therefore pumps in the carpark drainage system
- Redesign to eliminate holding tanks and pumps from the sanitary systems to instead connect to existing sanitary lines.
- Consolidation of emergency support systems including sprinkler pumping systems to eliminate extra pumps but expanding capacity of existing tank and genset upsize instead of seperate systems.
- Resdesign  of standard light fittings to allow for easy retrofit to LED in common areas if price improves.
- Modification of electrical system and roof to accommodate future solar PV opportunities.
- Changes to aluminium window extrusion profile to include thermal breaks (Common in cold countries but not in hot ones!)
- Design and addition of redundant gray water piping for future coupling to recycled water systems
- Detentions tanks for drainage

Monday, 28 July 2014

Selamat Hari Raya Puasa



Today we took the time to prepare for the casting of the first storey slab. This floor houses the main reception, a Heritage Centre, Admissions, the Foundation office and Alumni, The High School office, University Advising and the Head of Campus offices along with a large social and gathering place for students and staff that will link into the tent plaza area. 

The area that we are about to construct.

One good reason to study mandarin - We have a wide variety of nationalities on the site ....The plan broken up into teams and hopefully clear to all....

Concrete "Elephant" pumps on site ready for tomorrow.


And finally just in case this blog gives the impression that everything always goes perfectly to plan..  This wasn't in the plan for the fire hydrant installation today.......



The conclusion....


After raining most of the morning - 4pm finally getting going on the casting,






Some of the 92 concrete trucks involved in this concrete pour...

02:45 - Finished! 622 m3 of Concrete formed into a building!