Architecture, Engineering & Planning EVstudio | Denver & Evergreen Architect | Colorado & Central Texas | Blog » Structure

Don’t Forget to Check your Sump Pit and Pump

Jim Houlette — Thu, 19 Jan 2012 21:00:51 +0000

Your home may or may not have a sump pit. If you have one be sure to check it every few months, especially when you may have heavy rain. Most people forget about the sump pit leaving them open to a good chance of major problems.

When checking your sump pit check for the following items:

Standing water more than 4"
Properly working sump pump, it should turn on when the float is raised
Discharge pipe properly attached with no leaks
Discharge pipe exists the dwelling and extends at least 5ft away from the foundation
Water entering sump pit, is it dripping or pouring in?

Around the Denver area many houses are built with an elevated structural floor. When you are checking the sump pit be sure to check the conditions in the crawlspace. Feel the soil to see if it feels soft below the vapor barrier. Soft or muddy soil is a sign of high water content. Also, check the floor joists for signs of rotation or buckling. If the foundation wall is exposed look for cracks larger than 1/8" wide.

If you allow water to collect in the sump pit it will eventually rise to a level where the water then collects in the perimeter drain. Once water collects in the perimeter drain the foundation is at great risk to move if swelling soil is present. Also, you are exposing your house to potentially flooding during a heavy rain.

Originally posted 2009-12-20 22:44:14.

Bentley RAM Structural Software used by EVstudio

Jim Houlette — Thu, 19 Jan 2012 21:00:44 +0000

Structural Model - All Systems

The structural department prefers to use Bentley RAM structural design software for our finite element design needs. The total design package includes many different tools that can be used individually or together as shown above when several different materials and framing members are used. The software allows engineers to model a structure in 3D and keep a complete "total" design all in one. Different framing systems can then be designed using the different tools, but yet all loads and materials are saved into the same model.

This model is of the Company Headquarters building for the Warrior in Transition Project at Fort Hood, Texas. EVstudio is also designing the Soldier & Family Assistance Center that will be built along with the Headquarters. We are the design partner for Au Authum Ki who is the contractor and contract holder.

Elevated Two-way concrete floor - Reinforcement perspective

Although the structural software is very powerful, you as the engineer must be fully aware of how each member is interacting with each other and verify the output is correct.

Elevated Two-way concrete floor - Deflection plan

Originally posted 2010-08-17 00:01:54.

Resistance Piers for Economical Foundation Repair

Adam Denton — Thu, 19 Jan 2012 21:00:37 +0000

EVstudio is asked quite frequently to perform structural evaluations of cracked foundation walls. These cracks are often due to settlement. Modern design philosophy (and most geotechnical reports) calls for the original structural engineer to design foundation walls to clear span ten to fifteen feet to account for soft patches of bearing soil or soils that may be become saturated and hydro-consolidate (shrink in volume when wet). Older homes are more susceptible to damage because they were typically not designed with this in mind. This is not to say they were designed poorly, there were just different design philosophies and industry standards at the time they were constructed.

Installed Resistance Pier Bracket

How a resistance pier works is quite simple. First, a steel bracket is fastened to your foundation, typically at the footing. Then a hydraulic ram is installed on the bracket which drives a steel pier into the ground. Using the hydraulic forces in combination with the weight of the structure above, the steel pier is driven down through the softer soils (which are causing the settlement problem) until bedrock or suitably firm soils are reached. Once the pier reaches competent bearing, the foundation is stabilized and in some instances can even be raised back into a level position.

EVstudio works closely with Pinnacle Structural Services in the evaluation of foundation repairs utilizing the resistance piers as one of many considered solutions.

For more information on resistance piers please watch this informative video.

Originally posted 2011-09-24 00:49:33.

You Want to Remove a Load Bearing Wall?

Jim Houlette — Thu, 19 Jan 2012 21:00:35 +0000

One of the most common phone calls we receive is "We want to remove a wall, we're not sure if it's load bearing. Can you help?"

We are happy to help!

The first thing that is needed is an observation. Our structural engineers can determine the structural layout, identify load bearing walls and discuss options with you and a contractor. Our goal is to help you achieve the finished look you want while maintaining the structural integrity of your home. Safety and performance are our top priorities. During the project we are always happy to explain all options you have, cost differences and any performance concerns we might have. We enjoy educating homeowners about the structure so they have an understanding about their home and why we may recommend one option over another.

Identifying load bearing walls is fairly simple. Look for interruptions or lapped joints in the floor or ceiling joists, large spans, braces in the attic and beams below the wall in question. In addition, a wall might not be load bearing but it may be needed to brace the structure from lateral forces such as wind or earthquake loads. These walls are called shear or brace walls. Only a structural engineer can determine if a wall is load bearing or is a shear wall. Don't let contractors convince you they know what they are doing. Many do, but you won't know until it's too late.

Every house is slightly different and has it's own unique situation. To remove a bearing wall you will need to support the framing above with a dropped, flush or raised beam. The dropped header is the easiest and cheapest way. However, many people like the look of a flat ceiling with no soffit. Then a flush or raised beam is needed. A flush beam would have to be used if there is living spaced above the wall to be removed. A raised beam is a great option when there is an attic space above.

Flush wood beam incorrectly used without straps as tension ties

I don't like to use a flush beam for single story houses with a rafter/ceiling joist roof system. Many people don't realize that the ceiling joists are in tension holding the exterior walls in place due to an outward force from the rafters. If the ceiling joists are cut to allow for a flush beam that tension can pull the ceiling joists away from the beam. This typically causes a large crack to form in the ceiling and even worse could lead to the exterior wall bowing out. To prevent the separation, light gauge straps are used to connect the cut ceiling joists. The image above is a flush beam supporting ceiling joists. The ceiling joists were cut to allow the flush beam but were not attached with straps. We discovered this situation when we were requested to determine the cause of a large ceiling crack in an old home.

If you are looking to remove a wall please let us know. You can contact Jim Houlette at jim@evstudio.com or call the main line.

Originally posted 2011-08-07 14:45:03.

Effect of Overdriven Fasteners on Shear Wall Capacity

Jim Houlette — Thu, 19 Jan 2012 21:00:34 +0000

APA Technical Topics - Form No. TT-012A

With the use of nail guns set too high and the speed of construction, many nails are over driven. Most building officials don't seem to notice or comment on this error. But, if they do you might have a lot of work ahead of you to add correctly placed nails or staples when the nailing is too close for additional nails. Before you start adding nails or staples consider that additional nails may cause more harm than good. If the specified nailing is at 4"o.c. or less, adding more nails can damage the sheathing and studs, reducing the shear wall capacity more than if the additional fasteners were not used. APA addressed this problem and issued a simple breakdown on when you need additional fasteners or not.

Please visit www.apawood.org for additional information and other useful technical bulletins.

Originally posted 2009-08-08 22:27:19.

Seismic Testing of a Mid-Rise Wood Framed Structure

Adam Denton — Thu, 19 Jan 2012 20:59:46 +0000

NEESWood Capstone Test Structure

After the destruction caused by the 1995 Kobe earthquake the Japanese government took it upon themselves to construct the world’s largest seismic testing table, often referred to as a “shake table”. This testing facility, called Earth-Defense, was built to its enormous size out of necessity. Space to build new structures is a rare commodity in Japan and it was essential to be able to test large mid-rise (4 to 7 story) structures that maximize usable space while minimizing the building footprint. The Earth-Defense shake table is 50’ x 65’ and can support an astonishing 2.5 million pounds while “shaking” test buildings in three directions at once.

The NEESWood Capstone project shown in this video was conducted last summer to test the viability of wood framed mid-rise structures. Mid-rise structures are more traditionally constructed out of steel and concrete, but with the trend towards “green” construction it is becoming desirable to use renewable construction products like wood in larger commercial, residential and mixed use projects. The NEESWood Capstone project tested a seven story mixed use building consisting of a steel framed commercial (retail) main level and six stories of wood framed residential units. This test building was constructed in its entirety within the walls of Earth-Defense. The test building was constructed with many proprietary wood and steel products along with new NEESWood construction methodologies, all of which being beyond the scope of this article.

The portion of the results this test that was of most interest to me as an engineer was the “real life” forces experienced in the structure. As engineers in school we are handed exhaustive volumes of information that we are expected to accept as “the unquestionable truth”. There is an understanding that all of this information has been determined by hundreds of collective years of expert design experience, material testing and are always in a continuous state of refinement. As an engineering student I accepted that this was the adopted standard practice of my trade, but I always wondered how all the design theory I was being fed related to the real world. Hundreds of gauges were installed throughout the Capstone structure to test the forces actually experienced during an earthquake. It was quite satisfying as a design professional to see that the calculated anticipated forces at play in the structure were very close to those actually recorded.

For more detailed information on NEESWood Capstone project please follow this link.

Originally posted 2010-07-15 00:01:06.

Helical Pier Foundations

Jim Houlette — Thu, 19 Jan 2012 20:59:45 +0000

Helical piers are typically used when repairing failed shallow foundations. The helical piers are a deep foundation system that can be placed alongside existing foundations with very little interference.

However, helical piers are also used for new construction as an alternative to typical straight shaft drilled piers. EVstudio recently designed a new foundation using helical piers due to high water table and swelling soil. With a small surface area on the steel shaft the helical pier is very stable is highly expansive soil. We have also recently used helical piers for an addition to a home. There was no soils report, but the house was on drilled piers. A drill rig for new drilled piers could not gain access to the backyard, so helical piers installed using smaller machinery was recommended.

The real advantage helical piers have is their use for repairing moving foundations. The entire existing structure can be underpinned using helical piers that are bolted to the bottom of the foundation. Once the structure is underpinned the moving soil below the footing can be removed, establishing a void space separating the structure from any future movement.

PROS
Fast Installation
Can be Proof Tested
Negligible Uplift Pressure from Swelling Soil
High Tensile Resistance
Moderate to Small Equipment Needed

CONS
Specialized System
Concerns with Corrosion

Learn more about different types of foundations

Originally posted 2009-12-11 00:54:22.

Quickly Construct Concrete Pad Footings with FASTBAG

Adam Denton — Thu, 19 Jan 2012 20:59:39 +0000

At a recent seminar I attended I was introduced to the Fab-Form product called FASTBAG. This product is brilliantly simple….a textile bag you can fill with concrete and reinforcing bars to take the place of the wood formwork traditionally utilized to construct pad footings.

FASTBAG in the field.

The bags come in multiple sizes designed to replace standard pad footing sizes. While the shape of the filled bag does not look like the traditional footing the contact patch and load path are designed to be identical to a square footing as illustrated below.

I admit I have not seen these bags used in practice and unless I come across a project that requires the use of multiple pad footings I am not certain they would pay off over traditional wood forms for new construction. However, I do a lot of retrofit structural design for residential repairs and remodels and I see that the FASTBAG would have a wonderful application in this arena. I have had many projects that require new concrete pad footings to be constructed in very close quarters such as crawlspaces. I can see this product being a considerable help to a contractor who needs to construct a footing deep inside a crawlspace with only 20” of clear space to maneuver in. Stay tuned to this blog for a follow up report on the real world application of this product.

Originally posted 2011-03-31 00:21:24.

AutoDesk Revit Structure and Bentley RAM working together

Jim Houlette — Sat, 31 Dec 2011 21:20:58 +0000

EVstudio's structural department is working on several new projects where we will be modeling the structure in Revit and exporting it to RAM to complete the analysis. The first trial tests have been working great. As we become more comfortable with the process we will be doing some extra work by continuing with our previous means of design along with the new design procedure using Revit and RAM together.

The goal of using Revit structure is to have the ability to work with architects using Revit, create the complete BIM model and impute structural loads directly on the Revit model. These loads are then exported out along with the building model to create a true structural model used for design. The ability to communicate between a drafting software and a design software is amazing and will ultimately help engineers to track loads, resolve conflicts and provide high quality plans for our client and contractors.

EVstudio is always looking for ways to improve our work and provide higher quality products to our clients. The use of Revit and RAM are typically used for commercial projects, however can be used for residential as well. We are also talking with several software designers developing programs that model a residential wood structure, designs it, and produces a materials list for the builder. A great tool to have to reduce errors, value engineer and help builders know total material lists to reduce waste.

Originally posted 2011-04-10 00:09:43.

Raft Slab-on-Grade Foundation

Jim Houlette — Sat, 31 Dec 2011 21:20:36 +0000

A Raft Slab-on-Grade foundation can be as simple as a 4” thick slab with no reinforcement and a shallow perimeter rib to an 8” thick slab heavily reinforced with deep ribs spaced roughly 10’o.c. The wide range of concrete thicknesses and reinforcement is a function of many things such as soil type, loads, exterior finishes, allowable deflections, climate, and many more factors. The primarily factor that influences the slab thickness, reinforcement and rib sizes of a slab-on-grade foundation is the soil type.

If the soil is a sandy material with non-swelling fines to allow good compaction then the slab-on-grade foundation will be evenly supported, and has a low risk of soil movement. This raft foundation will just need the minimum slab, ribs and reinforcement.

If the soil has swelling material that is susceptible to changes in moisture content then the raft must be designed to resist this movement. The use of reinforced ribs is an economical way to strengthen the slab. Ribs are below the slab and are spaced evenly to create a grid or waffle appearance. This is done in lieu of thickening the entire slab because you gain more strength with depth and will typically use less concrete and steel reinforcement to achieve the same design capacities.

Raft foundations have been used for residential structures, commercial structures and heavy construction structures. The reason for the wide range of uses is simply because the raft slab-on-grade foundation is simple to construct and one of the most cost effective foundations. Typically, little earthwork is needed, sites are leveled, ribs are trenched, reinforcement placed and then concrete is placed. Also, since the raft foundation is just reinforced concrete, access to plumbing can be achieved by removing sections of the slab and then patching as needed. If the slab is post tensioned then accessing the plumbing is much more difficult.

But the raft foundation has its problems as well. On sites with high risk of soil movement the slab can become expensive if deep ribs and heavy reinforcement is needed. That is when a post tensioned slab may become cost effective. In addition, the control of visible cracks in the slab can be difficult. Concrete shrinks as it cures and if control joints are not placed appropriately or sufficient reinforcement is not used the owners may be upset with visible cracks. Cracks caused by shrinkage do not indicate failure, but can be an eye sore and a difficult conversation with the owner.

PROS
Cost effective
Common Construction
Low Tech
Sections may be removed to Access Plumbing

CONS
Limited Design Capacity
Does not respond well to Soil Movement

Learn more about different foundation types.

Originally posted 2009-11-03 10:42:22.