In the last few years, Simpson Strong-Tie has heard from a number of structural engineers expressing frustration with the lack of performance data for shallowly embedded, post-installed anchors (shallow anchors). Engineers of Record (EOR) have identified a common application for shallow anchors as those related to attachment of sill plates for structural and nonstructural wall-to-podium slab connections. One dilemma faced by the EORs originates in their desire to prevent damage to concrete podium slab reinforcement, especially where reinforcement is located close to the slab’s top surface to resist negative bending moments. EORs further indicate that shallow anchors are frequently needed for the following attachments: hanging MEP fixtures; attaching nonstructural components associated with tenant improvements; and anchoring light equipment.
Tag: concrete
Project Profile: Reinforcing Concrete Joists to Increase Load Rating
We’re excited to share another fiber-reinforced polymer (FRP) project that required both flexural and shear strengthening (photo below) of reinforced concrete joists to enable the slab floors to carry more live load. The structure is in Southern California, and appears to have been built in the 1950s or 1960s when pan joist construction was common. The EOR for this project, Structural Focus, is an experienced structural engineering firm known for seismic retrofit solutions. The FRP applicator was FD Thomas Structural Specialties, a contractor with decades of FRP installation experience.
Reasons to Specify SET-3G Adhesive for Anchorage in Concrete Construction
We’ve been receiving a lot of requests lately from engineers wanting to know exactly what the difference is between Simpson Strong-Tie’s relatively new adhesive, SET-3G™, and its predecessor, SET-XP®. Both are epoxy-based adhesives used to anchor threaded rods and reinforcing bars in concrete base material for structural applications. If you perform a live pull test on a ½“-diameter mild steel rod embedded 4“ deep in 3,000 psi uncracked normal-weight concrete, the result will likely be the same; in both cases, the steel rod will break in a ductile manner at around 11 kips. You can see this hourglass-shaped steel failure mode happening in Figure 1. (To learn more about anchorage failure modes and ductility, check out this blog). Yet, the SET-3G design values shown in ESR-4057 come out ahead. But why?
Case Study: Shoring Up Aging Concrete Grain Silos with Fiber-Reinforced Polymer
The Simpson Strong-Tie® Composite Strengthening Systems™ was used to restore and strengthen 6 distressed cast-in-place concrete grain silos with a combination of carbon and glass FRP, meeting a tight timeline and budget.
Are You Ready to Design Post-Installed Anchors in Cracked Masonry?
Design criteria for cracked-concrete masonry units are finally available for adhesive anchors.
It has been over 15 years since cracked concrete changed the way anchorage to concrete was qualified and designed. The ICC International Building Code (IBC) 2003 referenced American Concrete Institute (ACI) 318-02 Appendix D as a design provision for both cast-in-place and post-installed anchors into concrete. Appendix D was the first introduction of cracked concrete to designers. These design provisions required mechanical anchors to be qualified per ACI 355.2, which mandated testing of anchors in cracks. The Masonry Society (TMS) 405 has not addressed cracks in concrete masonry units since the code’s introduction to concrete in 2003. The Concrete and Masonry Anchor Manufacturers Association (CAMA) has taken on the task of introducing cracked masonry unit testing, qualification and design by updating Acceptance Criteria AC58. These criteria were developed to address the testing and qualification of adhesive anchors in grouted, hollow, and partially grouted concrete masonry units, as well as in brick masonry units.
Epoxy vs. Acrylic Adhesive Systems: Which Is Right for Me?
Not all anchoring adhesives are created equal. There are important differences between acrylic-based and epoxy-based adhesive systems — differences that affect installation, gel and cure times, and anchoring performance. In the following post, Marlou Rodriguez, S.E., of Simpson Strong-Tie, lays out some of the comparative installation advantages of each system.
There are two common types of adhesives for anchoring threaded rod or rebar into concrete — epoxy-based systems and acrylic-based systems. What’s the difference? When should you specify one rather than the other? This blog post will help you understand the differences and guide you in choosing the best adhesive for your anchoring solution.
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Simpson Strong-Tie® SET-3G™ Adhesive Offers a Ductile Solution for Post-Installed Anchorage near a Concrete Edge
Designing post-installed anchorage near a concrete edge is challenging, especially since the ACI provisions for cracked-concrete anchorage went into effect. In the following post, one of our field engineers, Jason Oakley, P.E., explains how SET-3G™ and Anchor Designer™ for Concrete software from Simpson Strong-Tie make it easier to design a ductile anchor solution.
Engineers often provide holdown anchoring solutions near a concrete edge to help prevent overturning of light-frame shear walls during a seismic (or high-wind) event. Sometimes a post-installed anchor must be used if the cast-in-place anchor was mislocated or misinstalled, or is located where a retrofit or addition is needed. Since the cracked-concrete anchorage design provisions went into effect more than a decade ago, it has been challenging for engineers to offer a near-edge post-installed anchoring solution. This is especially true for structures subject to earthquake loads in seismic design category (SDC) C through F. Simpson Strong-Tie’s new SET-3G epoxy is the first anchoring adhesive in the industry to offer exceptionally high bond-strength values that permit ductile anchorage in concrete near an edge. This blog post will cover a specific example that focuses on Chapter 17 of ACI 318-19 to design a threaded rod, anchored with SET-3G adhesive, used to secure a holdown located 1 3/4″ away from a single concrete edge (Figure 1).
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New CSS Product Launch — FRCM Strengthening Products
The new FRCM Composite Strengthening Systems™ repair and reinforcement solution from Simpson Strong-Tie combines high-performance sprayable mortar with a carbon-fiber grid that creates a thin structural layer that repairs and strengthens without significantly increasing the structure’s weight or volume. FRCM stands for fabric-reinforced cementitious matrix. Its advantages are similar to those of FRP (that is, strength, low weight and ease of application), but it may also be used to repair, resurface, strengthen and protect in one application, along with providing greater resistance to heat and better long-term durability.
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What’s New in the ACI 440.2R-17?
The wait is over. The ACI 440.2R-17 Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures is now available. The following post will highlight some of the major changes represented by this version of the document.
It’s been a long road and countless committee hours to get from the last version of ACI 440.2R-08 to this document. While there are multiple smaller changes throughout the document, the most notable update is the addition of Chapter 13 – Seismic Strengthening.
The new seismic chapter addresses the following FRP strengthening scenarios:
- Section 13.3 – Confinement with FRP
- This section includes all of the following: general considerations; plastic hinge region confinement; lap splice clamping; preventative buckling of flexural steel bars.
- Section 13.4 – Flexural Strengthening
- The flexural capacity of reinforced concrete beams and columns in expected plastic hinge regions can be enhanced using FRP only in cases where strengthening will transfer inelastic deformations from the strengthened region to other locations in the member or the structure that are able to handle the ensuing ductility demands.
- Section 13.5 – Shear Strengthening
- To enhance the seismic behavior of concrete members, FRP can be used to prevent brittle failures and promote the development of plastic hinges.
- Section 13.6 – Beam-Column Joints
- This section covers a great deal of recent research on the design and reinforcement of beam-column joints.
- Section 13.7 – Strengthening Reinforced Concrete Shear Walls
- This section provides many recommendations for FRP strengthening of R/C shear walls.
Simpson Strong-Tie Can Help
We recognize that specifying Simpson Strong-Tie® Composite Strengthening Systems™ (CSS) is unlike choosing any other product we offer. Leverage our expertise to help with your FRP strengthening designs. Our experienced technical representatives and licensed professional engineers provide complimentary design services and support – serving as your partner throughout the entire project cycle.
For complete information regarding specific products suitable to your unique situation or condition, please visit strongtie.com/css or call your local Simpson Strong-Tie RPS Specialist at (800) 999-5099.
Upcoming Free Webinar: Advanced FRP Design Principles
Join us live on July 25 for the second interactive webinar in the Simpson Strong-Tie FRP Best Practices Series: Advanced FRP Design Principles. In this webinar we will highlight some very important considerations during the FRP design processes. This will include topics such as the latest industry standards, proper use of material properties, and key governing limits when designing with FRP. Attendees will also have an opportunity to pose questions to our engineering team during the event. Continuing educations units will be offered for attending this webinar.
Learn more: Webinar – Introducing Fabric-Reinforced Cementitious Matrix (FRCM)
In this free webinar we dive into some very important considerations including the latest industry standards, material properties and key governing limits when designing with FRCM.
Continuing education credits will be offered for this webinar.
Participants can earn one professional development hour (PDH) or 0.1 continuing education unit (CEU).
Why You Should Specify Stainless-Steel Screw Anchors When Designing for Corrosive Environments
I was driving under a concrete bridge one nice clear day in Chicago, and I happened to look up to see rusted rebar exposed below a concrete bridge. My beautiful wife, who is not a structural engineer, turned to me and asked, “What happened to that bridge?” I explained that there are many reasons why spalling occurs below a bridge. One common reason is the expansion of steel when it rusts or corrodes.