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Tilt-up Construction
What may have begun in Ancient Rome is now one of North America’s fastest growing construction practices. Tilt-up Concrete Construction became a more feasible construction technique with the invention of the mobile crane about 100 years ago.
In tilt-up construction, a building’s walls are cast directly on the floor slab and are then tilted into place by a crane. This approach can deliver a finished building quickly because perimeter wall panels can be placed while the rest of the interior building systems are designed. The mass of tilt-up concrete often reduces the need for insulation in a building, and because the walls are cast on site, transportation costs are reduced.
Once tilted into place, the work crew braces the wall panels to keep them standing while construction continues on the next panel. The wall panels can weigh up to 150 tons, and an experienced crew can tilt 30 panels in a day! Although originally, most tilt-up buildings were simple warehouses, today, tilt-up is used for a variety of building types, including homes, office buildings, hotels, and schools
Let It Pour!
The largest concrete pour in Boston history was recently completed. Check out this time-lapse video to see what can be done in 22-1/2 hours, 572 concrete trucks, and a lot of skilled labor
Supporting MHP!
It was a pleasure supporting the Montgomery Housing Partnership (MHP) Golf Outing at Hampshire Greens Golf Course on May 12th. The MHP delivers affordable housing to those in need in Montgomery County. They also do a lot to help the community by providing assistances to young families.
This charitable golf event was won by the Gables Residential team of Joe Shuffleton (ETC), Shane Polk (Gables Residential), Mike Larkin (Tamko Roofing Products) and John McKenna, Esquire (Asmar, Schor & McKenna). Great job gentleman!
A Use For Recycled Glass Bottles
Did you know that only about a third of the total glass waste is recycled in our country?
Recent studies have found a remarkable use for glass in the construction field. More specifically, study results have proven that glass can be used like cement in concrete mixtures. This new viability of waste glass powder creates a significant opportunity and advantages for the concrete industry. The use of recycled glass not only can benefit the concrete industry but also it can positively contribute to create a more sustainable environment.
To test this application, Michigan State University (MSU) exclusively used recycled glass in concrete for all flatwork and a curb construction on campus. The recycled concrete was monitored for two years, and the material exhibited strength gain over time. In addition, the recycled concrete showed lower drying shrinkage than normal concrete. However, recycled glass has a quite complicated chemistry that can cause undesired effects in the concrete mix, which could greatly affect its workability. To use recycled glass safely as an aggregate, it is often necessary to incorporate other materials that can mitigate the adverse chemical reaction that glass can produce with alkalis in the mixture.
Stay Safe This Summer!
Remember to never store other chemicals (cleaning products, solvents, fertilizers, deicing agents, etc.) in pool filter or pump rooms. The most widely used pool chemical is chlorine and it does not play well with others (particularly ammonia compounds). Very bad things can happen if they should mix, including creation of chlorine gas and other highly toxic substances. Ammonia is present in most fertilizers and a number of chemical deicers. Stay safe this summer and separate your chemicals!
It’s also worth noting that chlorine is a powerful oxidizer. That property makes chlorine an effective sanitizing agent in swimming pools but it also accelerates corrosion (rusting). If you have electrical panels, light fixtures, or other steel items that share space with chemical treatment tanks, you’ve probably see the effects.
With Spring Comes Heavy Planters
We are often asked about weight limitations for balconies, particularly with regard to the allowable sizes and weights of plants that may be put on the balconies. The simple answer is that it depends on exactly how the balcony was designed and built. In general, plants that are placed on balconies should not be so large or heavy that they cannot be readily moved by the average size adult.
This would generally mean that an individual plant (with its pot, soil, etc.) should not weigh more than a normal adult (about 200 pounds). Plants with this type of weight limitation can often be placed throughout the balcony surface as long as a clean space of about two feet is provided between them.
Please remember that each case may vary. If you are concerned, think about having a structural engineer evaluate your specific planter layout.
ETC Continues To Grow….
ETC is pleased to welcome Ruben Osorio to our technical staff.
Ruben has been in the construction and engineering industry for six years and is also very experienced as an AutoCAD designer. He is currently working towards his degree in architecture/civil engineering at Northern Virginia Community College.
During Ruben’s free time (what little there is of it), he enjoys reading, listening to music and spending time with his wife, Laura and six-year-old son, Santiago.
We are glad to have him as part of our team!
Hope To See You on Thursday!
ETC and the Property Management Association (PMA) invites you to attend the largest apartment industry event in the Washington metropolitan area on April 17, 2014, at the Washington Convention Center. ETC is in booth #516, so please stop by and say hello! Our technical staff will be on site to answer all your building questions.
WUFI: Hygrothermal Analysis Software (No, It’s not a Dog)
Computer-aided Hygrothermal analysis and modeling allow us to understand movement of heat and moisture through building components. While such analysis is critical when developing a new building, it is also an effective tool in the repair industry when new roofing systems, re-cladding/coating building facades, or even introducing interior finish treatments are considered for an existing structure.
When changing the building’s cladding system components or interior conditioning system, it is always important to understand how heat and moisture will move through the building envelope to ensure the new system can achieve long term durability and satisfactory performance. Concerns such as condensation, material degradation (rot, spalling concrete/brick), or even mold growth may result if the building envelope is not properly designed with overall system drying potential and wetting risk being considered.
Unfortunately, modeling and analyzing heat flows and moisture drive is a very complex task. Lucky for us, we have the software that can help: a relatively new software family called WUFI (Wärme und Feuchte instationär, or Transient Heat and Moisture), developed by the Fraunhofer Institute for Building Physics (Germany) and Oak Ridge National Laboratory (US). This software calculates heat and moisture transfer through a selected portion of the building envelope (wall or roof section), in accordance with algorithms set forth in ASHRAE 160 “Criteria for Moisture-Control Design Analysis in Building.” The program can adequately model a component of an existing structure by taking into account the material properties, orientation of the analyzed section, and historical climate data for the structure’s location.
From this modeling, we are able to analyze:
- How moisture will accumulate or dry out of a wall system over time;
- Which layers of the wall system are most susceptible to moisture accumulations and thus damage or decay;
- How temperature and interior relative humidity may fluctuate based on historical climate information for the region; and,
- If a potential risk of biological growth is present on interior finishes.
Please contact us if you believe your structure is experiencing issues related to heat and/or moisture. Our trained staff can use the WUFI Pro 5.2 software to assess your areas of concern and offer solutions to moisture drive problems
Spray Water Test
Spray Water Testing is often used to evaluate water leakage of buildings, especially at walls, windows or doors. Although there are many ways to determine if something is watertight, a common and effective field test incorporates two types of wet conditions that a building will encounter during a storm: surface flow and wind-driven rain.
Surface Flow refers to water that flows down the face of a wall due to gravity. This type of flow can cause leaks without the pressure difference that comes along with the wind of a storm. To simulate it, a section of wall is isolated and sprayed with a spray nozzle at flow rates specified by ASTM E2128.
To test the window/wall for wind-driven rain, a pressure chamber is used. This chamber is usually on the inside of the building and a vacuum is placed in the chamber which draws water into the building to generate “wind” (AAMA 511). A spray rack is then used to simulate rain during a storm (see AAMA 502).
These tests are generally judged to PASS or FAIL for the window and/or wall in question. However, we can make the process more diagnostic by isolating a smaller defective section of the wall. This is helpful in determining the necessary repairs because a section of the wall, or a joint of a window may be all that needs to be repaired or replaced instead of the entire wall/window.
A recent ETC investigation of a water leak in an office space utilized a less involved test in which a garden hose and nozzle were used to systemically spray different potential leak areas until the location of the water entry point was discovered. By starting at the lowest elevation and working up, you can eliminate uncertainty about where the leak really is.
The ETC Team Grows
ETC would like to welcome our newest Staff Engineer, Adam Shamieh. Adam graduated from Georgia Tech with a BS in civil engineering with a focus on structures. He moved to Maryland in 2013 to work on the repair and restoration of existing structures. We are pleased he chose ETC as his new work home.
When Adam is not evaluating some interesting building problem, he enjoys bicycling, longboarding (downhill skateboarding), rock climbing and photography. I even hear he is quite the grill master. Can’t wait to try one of his famous chicken kebabs!
Hope To See You This Weekend!
ETC and the Washington Metropolitan Chapter Community Associations Institute (WMCCAI) invites you to attend the largest community association industry event in the Washington metropolitan area on March 22, 2014, at the Washington Convention Center. ETC is in booth #108, so please stop by and say hello! Professional engineers on site to answer all your building questions.
