Comprehensive data collection for the development of anchorage lifetime prediction models

Nowadays, fastening systems represent a very important part of the construction industry due to their versatility and use in reconstruction. Therefore, it is essential to study and understand phenomena and effects influencing the lifetime of a fastening system. However, the mechanisms are complex and not yet fully understood. As a result, numerical models, which are reliable and are able to capture all involved effects, are needed. The basis of these models is a wide range of high quality data, for model development, calibration, and validation purposes. Within the 7‐year Christian Doppler Laboratory (CDL) of Life Cycle Robustness, an extensive concrete data base, consisting of short‐term mechanical properties of concrete, time‐dependent measurements as well as tests on full fastening systems, was generated. The material tests reach from compression, indirect tensile, and fracture tests to long‐term creep and shrinkage tests. Shear and pull‐out tests were carried out on bonded and mechanical anchors. In order to characterize the long‐term performance, sustained load and time to failure tests were conducted at a system level. In total, 12 concrete mixes were tested. This contribution will give an overview of the performed tests and will highlight the importance of sound experimental data

Probabilistic and semi-probabilistic analysis of slender columns frequently used in structural engineering

The stability of slender columns is a topic that has been dealt with in research and practice for many years. The importance of this topic also increases with the possibility of using non-linear modeling approaches to determine the stability and with the increasingly complex safety formats. In order to show the complexity and the variability associated with the non-linear models, two previous contributions discussed and compared (a) the results of the Round Robin Non-Linear Modeling, and (b) the existing international associated standard specifications and safety concepts with respect to experimental results. The aim herein is to determine the reliability level (safety index) on the basis of these investigations and findings and to examine the existing safety formats of classical and extended probabilistic analyses and to derive any necessary adjustments. In addition, the method of the safety format Estimation of Coefficient of Variance of resistance (ECOV) is used for the determination of the global safety resistance factors based on the non-linear analyses’ findings of the Round Robin modeling partners.This paper describes work mainly carried out during IABSE activities. The authors would like to acknowledge IABSE Commission 1 for supporting this project, the authors acknowledge the financial support provided by the Interreg project ATCZ190 SAFEBRIDGE. The authors also gratefully acknowledge Scientific Grant Agency of the Ministry of Education. This work was supported by the Slovak Research and Development Agency under the contract No. APVV-150658. The authors also would like to express their thanks for the support provided from the Czech Science Foundation project MUFRAS No. 19-09491S. In addition, this work was partly financed by: (1) national funds through the Foundation for Science and Technology (FCT) under Grant No. PD/BD/143003/2018 attributed to the seventh author; and (2) FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under Reference UIDB/04029/2020

The influence of continuing reinforcement on the load capacity of a RC beam previously exposed to high temperatures

The paper describes the RC beam model development and the influence exerted by the main longitudinal reinforcement overlapping and transverse reinforcement (ties) on the bearing capacity of a RC load bearing structure for several cases of load, with an emphasis on the influence of high temperatures. Several RC beam models are made and relevant calculations and results are presented, which show the influence of the reinforcement method on the bearing capacity of structures, i.e. of the main-reinforcement continuing as related to the one-part reinforcement, as well as the influence of transverse reinforcement (ties)

Modeling Adhesive Anchors in a Discrete Element Framework

In recent years, post-installed anchors are widely used to connect structural members and to fix appliances to load-bearing elements. A bonded anchor typically denotes a threaded bar placed into a borehole filled with adhesive mortar. The high complexity of the problem, owing to the multiple materials and failure mechanisms involved, requires a numerical support for the experimental investigation. A reliable model able to reproduce a system’s short-term behavior is needed before the development of a more complex framework for the subsequent investigation of the lifetime of fasteners subjected to various deterioration processes can commence. The focus of this contribution is the development and validation of such a model for bonded anchors under pure tension load. Compression, modulus, fracture and splitting tests are performed on standard concrete specimens. These serve for the calibration and validation of the concrete constitutive model. The behavior of the adhesive mortar layer is modeled with a stress-slip law, calibrated on a set of confined pull-out tests. The model validation is performed on tests with different configurations comparing load-displacement curves, crack patterns and concrete cone shapes. A model sensitivity analysis and the evaluation of the bond stress and slippage along the anchor complete the study

Creep rate based time-to-failure prediction of adhesive anchor systems under sustained load

This contribution studies a well-known failure criterion and its application to the life-time prediction of adhesive anchor systems under sustained load. The Monkman-Grant relation, which has been previously applied to a wide range of materials, is for the first time applied to adhesive anchors installed in concrete. It postulates a linear relationship between the logarithms of minimum creep rate and time-to-failure leading to fundamental answers of problems emerging both from research and industry practice. In this paper the criterion is evaluated first on a large experimental campaign on one concrete involving two chemically different adhesives and then by several experimental data sets reported in literature. In all cases the data is well represented and highly accurate predictions are obtained. The second part of the paper focuses on the relationship between minimum creep rate and applied relative load level based on the Norton-Bailey and the Prandtl-Garofalo creep laws. The latter was found to perform better on fitting the experimental data. Finally, the combination of the Monkman-Grant criterion and the aforementioned creep laws allows the prediction of stress versus time-to-failure curves including uncertainty bounds that are in very good agreement with all experimental data sets, making it an interesting alternative to existing test methods for adhesive anchor systems under sustained loads

Mortar cure-dependent effects on adhesive anchor systems loaded in tension

This paper presents a large experimental campaign and the corresponding analysis quantifying mortar curing effects on the pull-out performance of bonded anchor systems. Standard confined pull-out tests were performed on two commonly used adhesive anchor systems. The two investigated bonded anchor systems were based on different materials, where the mortar of the first bonded anchor system (BAS-VE) was a vinyl-ester based product and the second bonded anchor system (BAS-EP) contained an epoxy-based mortar. In order to isolate the mortar curing effects on the anchor performance, a mature concrete was used as base material minimizing well-known aging and curing effects related to the substrate, concrete. In total, 93 pull-out tests were performed for various curing times in order to characterize influences on bond strength, stiffness, and peak displacement. Depending on the product specifications and corresponding approval documents, tests were carried out in a time-range of a few minutes up to three months after the anchor installations. Measured temperature (and humidity histories) of the environment have been utilized for predicting the mortars’ degree of cure for each structural anchor test. The results show a cure-dependent behavior in BAS-VE and BAS-EP. Although the bond strength fails to increase significantly after reaching the manufacturer approved minimum curing time, the stiffness shows an increase for longer cured anchors

Aggregate Type and Concrete Age Effects on Anchor Breakout Performance: Large Database and Insights

This contribution summarizes the largest available literature data collection on tensile and shear loaded anchor tests, obtained in two independent studies and performed by two different research groups. It was the objective of the two studies to investigate a possible effect that petrographically different coarse aggregate types may have on the tensile and shear load capacity for concrete breakout failure modes. In total, seven normal-strength and four high-strength concretes were tested at two different ages. Structural tests were performed on cast-in (tensile and shear tests) and post-installed adhesive anchors (shear tests). Parallel to the structural tests, each concrete was characterized in terms of compressive and tensile strength. Finally, the combined experimental data offer novel insights into the predictive quality of available design models for concrete cone capacity in tension and edge breakout in shear with respect to a potential aggregate effect. Systematic analyses indicate only minor aggregate effects after normalization by compressive strength (less than 7% difference between normalized values). However, the study reveals potential curing and concrete age effects where a 9% increase in predicted values is shown when concrete cures longer. The predictive equations remain conservative in comparison to all the investigated properties and their validity is shown in this study

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 on 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 peformance 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

Genome-wide Association Study of Anthropometric Traits in Korčula Island, Croatia

AIM: To identify genetic variants underlying six anthropometric traits: body height, body weight, body mass index, brachial circumference, waist circumference, and hip circumference, using a genome-wide association study. ----- METHODS: The study was carried out in the isolated population of the island of Korcula, Croatia, with 898 adult examinees who participated in the larger DNA-based genetic epidemiological study in 2007. Anthropometric measurements followed standard internationally accepted procedures. Examinees were genotyped using HumanHap 370CNV chip by Illumina, with a genome-wide scan containing 316730 single nucleotide polymorphisms (SNP). ----- RESULTS: A total of 11 SNPs were associated with the investigated traits at the level of P<10(-5), with one SNP (rs7792939 in gene zinc finger protein 498, ZNF498) associated with body weight, hip circumference, and brachial circumference (P=3.59-5.73 x 10(-6)), and another one (rs157350 in gene delta-sarcoglycan, SGCD) with both brachial and hip circumference (P=3.70-6.08 x 10(-6). Variants in CRIM1, a gene regulating delivery of bone morphogenetic proteins to the cell surface, and ITGA1, involved in the regulation of mesenchymal stem cell proliferation and cartilage production, were also associated with brachial circumference (P=7.82 and 9.68 x 10(-6), respectively) and represent interesting functional candidates. Other associations involved those between genes SEZ6L2 and MAX and waist circumference, XTP6 and brachial circumference, and AMPA1/GRIA1 and height. ----- CONCLUSION: Although the study was underpowered for the reported associations to reach formal threshold of genome-wide significance under the assumption of independent multiple testing, the consistency of association between the 2 variants and a set of anthropometric traits makes CRIM1 and ITGA1 highly interesting for further replication and functional follow-up. Increased linkage disequilibrium between the used markers in an isolated population makes the formal significance threshold overly stringent, and changed allele frequencies in isolate population may contribute to identifying variants that would not be easily identified in large outbred populations