The best fire protection strategies for structural components are useless if connections lack the necessary fire resistance. Many current European Technical Approvals for anchors in concrete provide details on duration of fire resistance based on EOTA Technical Report 020 – Evaluation of Anchors in Concrete Concerning Resistance to Fire – published in 2004. This report delineates testing, evaluation and design requirements for anchors subject to fire exposure. It addresses post-installed mechanical anchors, adhesive anchors and plastic anchors and includes a simplified design approach that considers all relevant concrete failure modes as well as pull-out failure and the steel resistance. The failure modes relevant for normal service conditions also apply under fire exposure. Nevertheless, as temperatures increase the yield point of steel drops significantly. Stainless steels exhibit superior resistance to elevated temperature over carbon steels; however, in general, the reduction in the steel strength is greater than that associated with concrete breakout or pull-out failure. Thus, in most cases, steel failure is the governing parameter in the design, although concrete failure may control in case of shallow embedment, anchor groups or close to the edge. The simplified design method to determine the steel capacity under fire exposure provided by the EOTA Technical Report 020 and by the pre-standard CEN/TS 1992-4 ‘Design of fastenings for use in concrete’ yields often very conservative results. Therefore the leading brands in fastening technology perform fire tests according to the regime given in TR 020, which result in design values which are sometimes as much as three times as high as the values according to the simplified prediction.

This paper describes an experimental investigation on the long-term creep behavior of adhesive anchors under sustained tensile loads in combination with different environmental exposures. The experimental program comprises of 36 pull-out test specimens. The specimens consist of a cylindrical shape concrete block of 300 mm (12 inch) in diameter and 200mm (8 inch) in depth, with 15M (No. 5) deformed steel bars post-installed to an embedment depth of six times the bar diameter or 125mm (5 inch). Three types of adhesives were used: Type A - Fast setting two component methyl methacrylate adhesive, Type B - Fast setting two part epoxy adhesive and Type C - Standard set two part epoxy adhesive. The study is divided into four phases. Phase I consists of static pullout tests to determine the yield strength (fy) and the maximum capacity of each anchor system. Phase II consists of sustained load tests under load levels of 40%fy at normal laboratory conditions. Phases III and IV are sustained load tests under load levels of 40%fy with moisture exposure and freeze/thaw cycling, respectively. All sustained load tests lasted for a period of at least 90 days. The results of the static pullout testing showed that specimens with epoxy based adhesive exhibited stronger bond strength, forcing the anchor to fail by rupture prior to bond failure. As for the sustained load test results, specimens with standard set epoxy based adhesive showed insignificant creep displacement under room conditions, however, when exposed to moisture noticeable creep displacements were recorded. Specimens with both fast setting epoxy and methyl methacrylate based adhesives showed higher creep displacements under environmental exposure versus those kept at room temperature.

Adhesive anchors are used worldwide for structural and non-structural connections. Because their structural behavior is influenced by many factors, adhesive anchors must be prequalified. In the US this is done according to ICC-ES AC308 and ACI 355.4-10. Design provisions for bonded anchors are stated in ICC-ES AC308 and the ACI 318-11, Appendix D. Only prequalified adhesive anchor systems are covered by the ACI Standard. In this paper the testing procedure, assessment criteria and design provisions with respect to sustained tension loading are described and – based on test results – the validity of the design provisions is discussed. It is concluded, that adhesive anchors qualified according to ACI 355.4-10 and designed according to the ACI 318-11, Appendix D can safely be used to resist sustained tension loading provided that they are installed properly. The design provisions given in ICC-ES AC308 and ACI 318-11, Appendix D should be applied to all anchors that must resist sustained tension loads and not only to anchors installed overhead.

ASTM E488 and ASTM E1512 as well as ICC-ES AC308 and ACI 355.4 have extensive testing protocols for the short-term and long-term evaluation of adhesive anchor systems. Currently the sustained load testing procedures establish residual load and displacement criteria on projected displacements from a 1000 hour sustained load test. An anchor is considered approved for sustained load if it meets these pass/fail criteria. In an NCHRP research project conducted at the University of Florida, an AASHTO standard (AASHTO TP 84-10) was developed to evaluate the sustained load performance of adhesive anchor systems based on a stress versus time-to-failure approach common with many testing protocols. Adhesive anchors are loaded to failure at various percentages of the mean static load as determined from static load tests. The resulting stress versus time-to-failure relationship generated from this test method is very useful to an engineer designing with adhesive anchors under sustained load. A subsequent NCHRP research project conducted in partnership at the University of Florida and the University of Stuttgart will utilize this test method to evaluate the long-term performance of adhesive anchor systems under sustained load coupled with various installation and in-service conditions (temperature, moisture, etc).

This paper describes and comments on AIJ Design Guideline 2010 of post-installed bonded (adhesive) anchor. This paper presents tension tests to clarify the influence of the embedment depth and the edges on the tensile behavior of a single post-installed bonded anchor. The 4 parameters of the test are established; embedment length (le = 7da, 14da and 21da; da: anchor diameter), edge configuration (anchorage at an edge, a corner and thin member), edge distance and adhesive system (glass capsule type, film foil type and injection type). In those tests, we investigated failure mode and failure load of bonded anchor close to the edge(s), and discussed about resistance of anchors to tensile load. Further, the method to estimate the tensile strength (failure load) of single-anchor or of anchors in the groups was proposed with the influence on edge(s). The method in bond failure type is modeled based on a uniform bond stress, and the uniform bond strength is evaluated with reduction coefficient which considered the number of edges and the edge distance.