Aggregate effect on the concrete cone capacity of an undercut anchor under quasi-static tensile load

In the last decades, fastening systems have become an essential part of the construction industry. Post-installed mechanical anchors are frequently used in concrete members to connect them with other load bearing structural members, or to attach appliances. Their performance is limited by the concrete related failure modes which are highly influenced by the concrete mix design. This paper aims at investigating the effect that different aggregates used in the concrete mix have on the capacity of an undercut anchor under tensile quasi-static loading. Three concrete batches were cast utilising three different aggregate types. For two concrete ages (28 and 70 days), anchor tensile capacity and concrete properties were obtained. Concrete compressive strength, fracture energy and elastic modulus are used to normalize and compare the undercut anchor concrete tensile capacity employing some of the most widely used prediction models. For a more insightful comparison, a statistical method that yields also scatter information is introduced. Finally, the height and shape of the concrete cones are compared by highly precise and objective photogrammetric means

Consistent time-to-failure tests and analyses of adhesive anchor systems

Motivated by tunnel accidents in the recent past, several investigations into the sustained load behavior of adhesive anchors have been initiated. Nevertheless, the reliable lifetime prediction of bonded anchor systems based on a relatively short testing period still represents an unsolved challenge due to the complex nonlinear viscoelastic behavior of concrete and adhesives alike. This contribution summarizes the results of a comprehensive experimental investigation and systematically carried out time-to-failure analysis performed on bonded anchors under sustained tensile load. Two different adhesive materials that find widespread application in the building industry were used, one epoxy and one vinylester based. Performed experiments include full material characterizations of concrete and the adhesives, bonded anchor pull-out tests at different loading rates, and time-to-failure sustained load tests. All anchor tests are performed in a confined configuration with close support. After a thorough review of available experimental data and analysis methods in the literature, the experimental data are presented with the main goal to (i) provide guidance for the analysis of load versus time-to-failure test data, and (ii) to derive a set of recommendations for efficient time-to-failure tests having in mind the needs associated with different analysis techniques. Finally, a new approach based on a sigmoid function, previously used only for concrete, is for the first time applied to bonded anchors systems and compared to the established regression models

Round-Robin modelling of the load-bearing capacity of slender columns by using classical and advanced non-linear numerical and analytical prediction tools

Non-linear finite element analyses have intrinsic model and user factors that influence the results of the analyses. However, non-linear finite element analysis can provide a tool to assess safety using realistic descriptions of material behaviour with actual material properties. A realistic estimation of the existing safety and capacity of slender column elements can be achieved by means of "true" material properties. Nevertheless, it seems that for some structural components, such as slender columns, non-linear finite element analyses can, due to its complexity and its various setting parameters, cause the risk of overestimating the real performance of analysed components or systems. Hence, an invited expert group has carried out an investigation into the experimental testing and the prediction of the bearing capacity of slender columns by performing independent non-linear finite element analyses in order to determine the practical applicability, and its inconsistencies, with respect to the stability failure of slender columns. This work aims the characterization of modelling uncertainties, concerning the prediction of slender columns stability when forecasted by non-linear finite element analysis.This paper was partly carried out during research exchanges at TU Brno (BUT), Lehigh University (LU). The authors acknowledge also the financial support provided by the SAFEBRIDGE ATCZ190 EU Interreg project, the Scientific Grant Agency of the Ministry of Education of Slovak Republic, the Slovak Academy of Sciences VEGA No. 1/0696/14, and Slovak Research and Development Agency under the contract No. APVV-150658. The computational results presented have been achieved [in part] using the Vienna Scientific Cluster (VSC)

On the dependence of concrete edge breakout on concrete age and coarse aggregate type

A large experimental campaign and its analysis are presented with the main goal to experimentally investigate possibly significant influence factors on concrete edge breakout, tested on bonded anchors that are loaded in shear towards a free edge. The main investigated influence factors are (i) the used coarse aggregate type, and (ii) the concrete age. Three normal strength concretes with different coarse aggregate type (quartz, limestone, and basalt) were cast and tested at two different ages-28 and 70 days. The experimental investigation comprised material characterization tests performed on aggregates and concretes, and structural tests, that is, quasi-static shear tests on installed anchors for three edge distances. The concrete failure surfaces were measured by means of photogrammetry in order to detect variations in cone size and shape dependent on coarse aggregate type and concrete age. The analysis based on the available data, normalizing with compressive strength obtained at the age of the anchor tests, reveals only a minor aggregate effect for the two larger investigated edge distances. Additionally, present differences between concretes are found to be smaller than those between different ages of the same concrete

Aggregate effect on concrete cone capacity

Recently, a large experimental campaign was completed that attempted to establish a link between petrography of the coarse aggregate, the concrete material properties and the system response in terms of concrete cone capacity. The investigation focused on three normal strength concretes having different coarse aggregate types (quartz, limestone, basalt) but otherwise similar mix design. All specimens of each concrete were cast from the same batch, carefully cured following three sets of curing protocols, and systematically characterized. The investigation comprised aggregate and concrete characterization, and structural tests performed at two ages on cast-in headed stud anchors under tensile loading. The aggregate characterization included the determination of Los Angeles coefficient, hardness and Young's modulus. In order to characterize the concretes, standard compression and indirect tension tests, were performed together with fracture tests. The experimentally obtained material and structural data finally served for the evaluation of current predictive models in terms of concrete compressive strength or concrete fracture properties as well as a correlation study. Aided by photogrammetric analysis, the concrete cone shape was determined for each individual test and analyzed to uncover possible dependencies on the coarse aggregate typ

Sustained load and time to failure of fastening systems

Fastening systems play a crucial role in structural engineering, e.g. connection of structural elements, assemble precast elements, and attach non-load bearing components. The significance of fastening systems can be found due to the fact that the potential damage caused by failed fasteners could be quite higher than the value of the products themselves. Fastening systems are usually designed to serve for a long time horizon under constant loading. Thus, a safe design requires a thorough insight of all involved mechanisms, e.g. creep, shrinkage, and their potential change with time, for all in-volved materials. In case of sustained loading, it is necessary to define load level limits that do not lead to failure during service lifetime. Therefore, characterization of the viscoelastic properties, as well as of the loading rate strength dependency of all involved material is required. The aim of the present contribution is to characterize experimentally the viscoelastic and the time dependent fracture properties of fastening systems. Consequently, sustained load tests for different fastening systems, mechanical and chemical adhesive, loaded at different load levels, are tested. In parallel full material characterization, as well as characterization of the viscoelastic properties and of the loading rate dependency of the involved materials is carried out. In particular, various tests, including standard cylinder and cube compression, three point bending, and Brazilian splitting are performed. Addition-ally, the loading rate strength dependency is characterized through three point bending tests per-formed at different loading rates, while the fracture time dependency is characterized through three point bending time to failure tests

Numerical investigation of anchors under shear loading

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