Middleweight Concrete

Incorporating the admixture of lightweight synthetic particles (LSP) in Portland cement concrete may lead to cost savings without property reduction.
http://www.structuremag.org/article.aspx?articleID=1423
-Middleweight concrete with LSP admixture unit weight 110-120 pcf.
-LSP shear strength substantially exceeds ACI predicted values.
-Modifier for lightweight concrete need not apply for middleweight concrete.
-Cost savings derived from reduced materials associated with lower weight and resultant reduced structural dimensions required of concrete members.
-Premium for LSP admixture dependent on location, but overall net savings can be realized for moderately sized projects.
-Contact Schnitzhofer & Associates, LLC for learn more about using Middleweight Concrete for your commercial projects.

Structural Article Summary – Fasteners

The ICC-ES governs the code that dictates the requirements of standard fastener use, and offers various Acceptance Criteria, based upon type and application, to assist in evaluation of alternative fasteners.Click here for a link to the article in STRUCTURE Magazine.

• Acceptance Criteria that form basis of evaluation of fasteners are developed by industry experts and code officials
• Evaluation of power-driven fasteners dependent on material into which they are driven
• Acceptance Criterion 118 addresses evaluation of tapping screws, including screws whose designs deviate from ASTM standards
• Acceptance Criterion 233 covers the evaluation of wood screws based upon testing of lateral, pull-through, and pullout capacities, bending yield, and tensile and shear strength
• Acceptance Criterion 116 provides evaluation criteria for nails that may otherwise not conform with pertinent ASTM standards

Structural Article Summary – Wood Truss Code Updates

2009 IBC has updated the code that results in required action during the construction phase of a project when long-span metal-plate-connected (MPC) wood trusses are implemented.Click here for a link to the article in Strucural Engineer.

• MPC wood trusses spanning 60 feet or more require a registered design professional to design temporary and permanent bracing
• Prior code only recommended, but did not require registered design professional involvement, leading to inconsistent safety results during construction
• An independent, approved agency must still perform inspections during construction on certain items, as per code
• The registered design professional is responsible for the appropriate submittal documents
• Deferral of any submittals by the registered design professional require prior approval of the building official

Structural Article Summary – Precast Concrete

The use of precast concrete provides several benefits to design, construction, and costs in heavier commercial projects.Click here for a link to the article in Structural Engineer.

• Decreased site footprint, a key where construction space is limited
• Decreased construction time required on site, leading to minimization of trades working on site
• Precast concrete is satisfactory for structural elements and also for architectural/construction requirements (e.g. comparative ease of fireproofing or waterproofing)
• Application of layers of precast walls provides both noise and thermal insulation
• Precast concrete improves LEED scores by using recycled and/or locally sourced materials

Structural Article Summary – Steel Decking

The evolution of the research on and understanding of steel decking has led to its efficient use in design and application.Click here for a link to the article in STRUCTURE Magazine.

• Steel decking originally designed as a structural member with concrete added only to provide a flat walking surface and fire resistance.
• Composite steel deck manufacturers of the 1960s had their products individually validated, leading to specifications particular to each company’s products
• AISI funded research to unify one design standard
• Implementation of one code grew the market for steel decking
• Steel Deck Institute (SDI) continued to further the development of standards in response to technology advances

The Greenest University Building Ever!

Achieving the LEED Platinum designation in building is feasible without overburdening structural design requirements, as exemplified by in the construction of the Student Services Center at the University of Texas at Dallas.   http://www.gostructural.com/magazine-article-gostructural.com-1-2012-leed_platinum_and_the_structural_engineer-8673.html

• Post-tensioned beams used as solution for critical structural issues associated with the need to create large column-free spaces

• Design details included to allow concrete shrinkage to occur prior to locking the building into its shear walls thereby minimizing the potential of cracking

• Application of façade-specific louvers to control the effects of sunlight into interior spaces of building

• Architectural exposure of large portions of structural elements to reduce ceiling and floor material requirements

• Close and constant coordination between Structural Engineers and Architects key to achieving success

Mark Raymond: Victims of The City

TED Talk: Watch Here.

Architecture can bring people together, or divide them — witness the skyscraper, costly, inefficient, and only serving small portions of the community. At TEDxPortofSpain, Mark Raymond encourages city governments to let go of their old notions of success and consider the balance of environment, economy, and society to design cities for social change.

Mark Raymond is the president of the The Trinidad and Tobago Institute of Architects — a firm dedicated to safeguarding sustainable, ethical and artistic design throughout the islands. He studied at the Architectural Association in London and worked for Norman Foster and DEGW before returning to Trinidad. Mark works on a wide variety of architectural, urban design and landscaping projects. He has also lectured in the US, UK and throughout the Caribbean.

Risk Management

Risk Management: Preventing-Mitigating Field Construction Problems

Basics of Wood Inspection: Considerations for Historic Preservation

A Brief Summary by S&A of:

APTI Article, Vol XXXVIII No. 2-3, 2007 Page 36, by Mr. Ronald W. Anthony.

Introduction:

3 Primary Reasons to Conduct a Wood Inspection

1. Concerns about moisture and it’s effects.
2. Deterioration, both physical and biological.
3. Need to determine material properties.

Highly Variable Wood Behavior

1. Different species.
2. Rate of tree(Measured in Growth Rings per Inch).
3. Age of tree.
4. How the wood was cut from the log.
5. Presence of defects.
6. End use conditions.

 Concerns About Moisture

1. Paint peeling, stains, warping.
2. Active leaks.
3. Decay + insects associated with moisture.
4. Moisture measurement.

Concerns About Deterioration (Weathing)

1. Results of weathering, overload failure, mechanical failure, shrinkage.
2. IMPORTANT: Checks can be o.k. Checks in structural members that “meet” are of concern.
3. Differential shrinkage in mortise & tenon can lead to failure.
4. Weathering of Wood: Cyclic wetting and drying, exposure to UV light & erosion by windblown debris.

Concerns About Deterioration (Biological)

1. Fungal or insect attack.
2. Bacteria degradation possible but not common in historic buildings because fungi + insects act more rapidly.
3. During inspections – focus on fungus and insect activity.
4. Be aware of moisture absporption through endgrain. Internal mositure retention causes decay, and not always visible.
5. Inner growth rings better resist decay.
6. Mildew: Grows on surface – does not damage wood.
7. Stain Fungi: Propogates through wood but does not cause effect strength.
8. Decay Fungi: (Alert Here) Breaks down wood composition. Types include: Brown Rot, White Rot, Dry Rot. It is important here to identify location and extent of rot.
9. Incipient Decay: (Early stages of decay) Discoloration + initial loss of integrity of wood. Use an awl or screwdriver to discover soft or punky wood.
10. Intermediate Decay: Small voids have developed.
11. Advanced Decay: Tools to measure interior decay – Incriement borer, hand drill. More advanced technique – Resistance drilling, to determine extent of damage.
12. Termites: Detection by presence of mud tubes.
13. Wood Boring Beetles: Create holes packed with “frass.”
14. Carpenter Ants + Bees: Leave large open holes.
15. For both insect and damage and decay, effective cross section properties of the members can be determined and used for structural analysis.

Material Properties

1. Determine wood species.
2. Tools for Wood Inspection: 1. Visual inspection 2. Sharp probe 3. Moisture Meter 4. Telescoping mirror and flashlight.
3. Visual ID’s: MIssing or broken pieces, fungal decay, moisture.
4. Probe ID’s: Internal voids.
5. Moisture meter: provides approximate values.
6. Conductance meter (Resistance Moisture Meter): Used for heavy timbers. This method is useful for determining whether the wood is drying or taking up moisture.

Advanced Investigative Techniques

1. Stress wave analysis: Location of advanced decay.
2. Resistance drilling: Quantify loss of material.
3. Digital Radioscopy: View hidden conditions.

Where to Look

1. Wood in contact with the ground.
2. Wood exhibiting moisture stains.
3. Wood with visible decay.
4. Roof penetrations.
5. Attic sheathing, framing lumber and timbers.
6. Sill beams and wall plates, particularly when in contact with masonry.
7. Floor joists and girders, particularly where resting on exterior walls.
8. Openings (doors and windows)
9. Material interfaces.
10. exterior woodwork.
11. porches.
12. crawl space and basements.
13. areas of structure that have been altered.

Professional Development Courses Completed

09.24.2011 – New Siesmic Stablilization Technology for Retrofits and New Construction

Design of fiber reinforced composite materials for strengthening of existing structures

Guidelines for development around tunnels and seismic compliance of underground tunnels