Author Archives: CS Editor

Tips for specifying exterior concrete surfaces

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Brooming large-area placements is a much more difficult task than brooming sidewalks or driveways. Controlling the depth of broom marks is just one of the problems faced by finishers. Photo courtesy CECO Concrete Construction

by Ward R. Malisch, PE, PhD, Bruce A. Suprenant, PE, 
and Frank Salzano, PE, PhD

Based on the information presented in the article, “Specifying Broomed Exterior Concrete Surfaces” by Ward R. Malisch, PE, PhD, Bruce A. Suprenant, PE, and Frank Salzano, PE, PhD in the April issue of The Construction Specifier, the following are recommendations for specifying exterior concrete surfaces.

Appearance (broom finish)
The broom finish should be specified to match the appearance in an existing slab or pavement of comparable size. For instance, one should not specify a sidewalk appearance for a parking structure. Also, a mockup or reference sample should be specified for appearance consistent with the placement size. The limitations of a mockup should be understood; when one is used, there should always be a repair portion so the contractor’s means and methods using the specified repair materials and procedures can be evaluated when repair is necessary.

Texture
A limited-range broom finish—such as light, medium, or heavy—should be avoided because it is hard to distinguish between textures to that degree. One should specify a broom finish as light-to-medium or medium-to-heavy. Further, texture depth should not be specified unless a procedure for measuring depth is included in the specifications.

Flatness
For parking lots and other site paving, a 13-mm (½-in.) gap under a 3-m (10-ft) straightedge can be specified. Use ACI 117-10, Standard Specifications for Tolerances for Concrete Materials and Construction, methodology for measuring with a straightedge. For parking structures, one should specify an overall floor flatness (FF) of 17 and a minimum local floor levelness (FL) of 11. (ASTM E1155, Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers, can be used for its methodology for measuring F-numbers.)

Drainage
Whenever possible, a top-surface one-way slope or a one-way top and bottom surface slope should be specified, with two-way slopes and warps avoided. A two percent slope for water drainage of suspended slabs should be specified. The structural engineer should check short-term and long-term deflections to determine their effect on drainage.

Aluminum design manual available

The 10th edition, and newest installment since 2010, of the Aluminum Design Manual has been released by the Aluminum Association. This resource is important for engineers and other construction professionals using aluminum in load-bearing structure design. Referenced in the 2015 International Building Code (IBC), the resource covers sections including aluminum structures, design, material properties, and design aids. Additionally, more than 30 illustrated design examples are included based on the specification of aluminum structures. Visit www.aluminum.org for ordering information.

AISC design guide published

The American Institute of Steel Construction (AISC) has released AISC Design Guide 29, Vertical Bracing Connections–Analysis and Design, providing information on common bracing systems and structural principles. The lower bound theorem of limit analysis and uniform force method are used to address brace-to-gusset connections, orthogonal and nonorthogonal connections, as well as chevron or K-bracing, eccentric braces, and gusset plate stability. More than 12 complete design examples are included with all applicable state limits identified. To download the guide, visit www.aisc.org/dg.

New 3-D modeling program now available

Model-based design software, Tekla Structural Designer, is now available for architects, engineers, and construction professionals to effectively analyze and design 3-D multi-material buildings. Fully automated design features, as well as high-quality documentation and building information modeling (BIM) allows users to create various project aspects from steel framing to concrete slab design in a single design model. The program provides the ability to compare alternate design schemes, manage changes, and collaborate with other team members. Other features include wind loading and finite element analysis, automatic product documentation, change management, and model synchronization. For more information, visit www.tekla.com.

CLFMI guidelines released

The Chain Link Fence Manufacturers Institute (CLFMI) has released updated editions of two of the organization’s most used technical guidelines, CLFMI Product Manual and Wind Load Guide for the Selection of Line Post Spacing and Size. Used by architects, specifiers, and contractors around the world, these resources help ensure the correct chain link fencing systems are being specified and installed for various applications. Information regarding commercial, industrial, residential, and high-security projects is included. Applicable ASTM standards are examined, as well as tables to determine appropriate line-post spacing in various wind-load conditions. To download these guides, as well as others, visit www.chainlinkinfo.org.