Category Archives: Construction

Will the Olympics Come Back to the US?

2024 is eleven years away but that hasn’t deterred the US Olympic Committee (USOC) from thinking about the future.  After a two repeated failed bid attempts (New York City in 2012 and Chicago 2016), the USOC recently sent letters to 35 mayors, inviting them to consider bidding for the 2024 Olympics.

“Our objective in this process is to identify a partner city that can work with us to present a compelling bid to the IOC and that has the right alignment of political, business and community leadership,” USOC CEO Scott Blackmun said in the letter.

While this does not guarantee the USOC will officially bid for the 2024 games, this is their first step testing the waters and interest level.  The feedback and interest level of each city’s response will help determine if the US could potentially host its fifth Summer Olympics (previous US host cities include: 1904 – St. Louis, MO, 1932 – Los Angeles, CA, 1984 – Los Angeles, CA, & 1996 – Atlanta, GA).

The International Olympic Committee will vote on the 2024 Games sometime in 2017, giving the USOC four years to prepare – and they’ll need it. The US is not alone in their expressed interest in winning the 2024 games, Paris; Rome; Doha, Dubai; and Durban, South Africa have all thrown their hats in the ring.  For more information on the USOC’s letter, please read more here.

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Short and Long Span Pool Structures

An indoor aquatic center is a building consisting of two or more rooms.  One room is the natatorium, which contains one or more pools. 

Indoor short span natatoria house short course pools and have a narrow width, around 100 feet.   Such a space can accommodate all types of pools as long as their widths are in the range listed above.  A short span across the building offers greater variety of materials in the relative cost range.  Concrete is considered a first choice for life cycle costs due to its total resistance to corrosion and its lifetime durability if properly engineered, constructed and coated.   A concrete roof system can be cast-in-place with beams and deck, it can be built up with precast T’s and precast planks or it can be a combination depending on the structural type of the building. 

When the natatorium width exceeds100 feet, the depth of the beam and its length begins to add significant costs for both fabrication and for delivery.  At these costs, alternative roof structural systems become attractive.  The most economical systems are steel trusses, which must be covered with a high-build epoxy coating to protect against corrosion.  Glulam beams with wood decking have been successful when the wood is properly processed and humidity in the natatorium is controlled.  Tensile roofs are successful in some building types if budget is available for first cost and environment control.  If a steel system is chosen, the trusses should be pipe or box-type.  Bar and angle joists are difficult to coat and recoat due to recesses and the high number of welds, bolts and webs.  Corrosion may occur in these poorly or non-coated points.

CannonDesign – Cost Trends

As most of us know in the recreation design industry, CannonDesign is a multidisciplinary international design firm.  Cannon’s December newsletter focuses on economic trends impacting design and construction.  It reviews unemployment rates, Non-residential Construction, GDP, futures, and construction cost values.  For those interested in a crystal ball look into 2013, I encourage you to take a look.

http://www.cannondesign.com/ecamp/2012/Cost_Trends/december_2012/hepg5.html

 

Modern Swimming Pool Concrete and It’s Ancient Past

Beneath the water and under the plaster and tile finish lays the fundamental element in most swimming pools: concrete. It has been used to reinforce a pool’s structural shell for over 2,500 years; the Ancient Romans were the first to use it in their baths. But what is it about concrete that has kept it in use throughout history and into the modern day?

Concrete is made up of three basic components: water, aggregates and Portland cement.  Water hydrates the cement and provides the exothermic chemical reaction which begins the hardening process.  The amount of water in a concrete mix can vary, but in general, the lower the water/cement ratio, the stronger the resulting material.  Contrary to popular belief, concrete and cement are not the same thing; cement is actually just a component of concrete.  The cement and water form a paste that coats the aggregate and sand in the mix. That paste hardens and binds the aggregates together.  The aggregates vary based on the mix design, but usually include small, medium, and large aggregates such as sand, gravel, and crushed stone.

Other than stone, the aggregate category also includes additives which alter the properties of the concrete. Some additives accelerate the concrete setting time, while others slow it down according to the designer’s needs. Two common additives are Fly Ash and ground granulated blast furnace (also known as “Slag.”) These common pozzolans react with calcium hydroxide to improve the workability of concrete, improve surface finish, and reduce the heat generated by setting concrete.

The American Concrete Institute (ACI) has extensive documentation on the use of both Fly Ash and Slag in concrete mixes.  As these additives tend to be less expensive than cement (and may be used as cementitious replacements up to 50%), they can be tantalizing options with significant budgetary implications.   Fly Ash and Slag may even be used interchangeably if one is not available.

It is important to note that while up to 50% of cementitious material may be substituted with Slag (per ACI standards), a rule of thumb in pool structural design is to cap the replacement at 15%, as the long-term performance of the concrete may be affected.

From purely a structural performance perspective, with an eye to serviceability and durability, the ACI does not have any issues the use of pozzolans.  However they will affect the concrete, something contractors need to be aware of prior to construction.  Additionally it is critical that the concrete batch plant is aware of the application of the concrete prior to determining the mix design.

How does all of this affect swimming pools?  The use of pozzolans in swimming pool concrete has been used for many years.  Regardless of the pool’s intended finish (tile, plaster, or paint), it is important to follow the manufacturer’s recommendations for finish application; such as ensuring the concrete is clean and free of debris.

As always, please contact a structural engineer for any structural design solution.  For more information on swimming pool concrete or the application of a pool shell finish, please refer to following online resources:

Portland Cement Association – http://www.cement.org/index.asp

National Plaster Council – http://www.npconline.org/

The Tile Council of North America – http://www.tcnatile.com/

What To Do When Your Pool Leaks

A leaking pool is a problem…for everybody. How do you find the leak or leaks, and then how do you fix the problem?

Following a plan can often reduce time and frustration.  A good strategy for finding one leak is the following:

1.      Identify the most likely sources of a leak in a pool:

a)  A crack or hole in the shell

b) The expansion joint and the water stop is broken and the sealant is compromised

c) Honey combing (tiny holes) in the concrete around fittings

d) An underwater light conduit broken or unglued

e) A leaking seat at a hydrostatic relief valve

f) A failure in the underground piping

2.      Testing for leak:

  •  Step one: At closing time, mark the normal operating water level.  Operate the filter pump all night and then mark and measure the loss of water 12 hours later the next morning.
  •  Step Two: At closing the following evening, repeat the same as above except turn off the filter pump. The next morning mark and measure the loss of water.

a)  If the water loss is the same, whether the filter pump is running or not, the leak is in the pool shell, and at one or more probable sites identified as in a-e above.

b)  If the water loss is greater when the filter pump is operating it suggests the leak is in the pressure piping.

c)  If the water loss is less when the filter pump is in operation, it suggests that the leak is in the suction piping i.e. the suction in the pipe draws groundwater into the pool or mud impacts a crack in the pipe, thus reducing the loss of water.

d) If a leak in the pool shell is identified as large or small, the next step is to confirm the location. The most common is to use food-coloring concentrate or crystal violet with scuba or mask and snorkel.

e) Modern technology provides professional leak detection contractors.

f)  If the leak can be diminished by temporary underwater repairs to the pool shell or piping, that may be the best tactic until the end of the outdoor season. If in an indoor pool, a shutdown will need to be scheduled to make repairs.

This was shared by Joe Hunsaker with Aquatic Professionals in 2005.