CivilEng, Volume 1, Issue 3 (December 2020) – 12 articles

Currently, the determination of the shear capacity $V_{Rk,s}^0$ of post installed adhesive anchors is already included in the current standardization and approval documents. Considering that EAD 330499-00-0601 allows for determining the shear resistance of a fastener only based on the characteristic steel ultimate tensile strength $f_{uk}$ determined from the material tensile tests, and without considering the actual ductility of the material used, this leads to a severe underestimation of the actual steel shear resistance. In order to efficiently determine the shear strength by calculation based on material characteristics, tensile and shear tests were carried out on metallic threaded rods and rebars to show their correlation with the material properties. A new correlation between tensile and shear strength is presented, which is based on the plasticity module $E_{pl}$ and allows a good prognosis of the shear strength. Full article

This article investigates the development of the following material properties of concrete with time: compressive strength, tensile strength, modulus of elasticity, and fracture energy. These properties were determined at seven different hydration ages (18 h, 30 h, 48 h, 72 h, 7 days, 14 days, 28 days) for four pure cement concrete mixes totaling 336 specimens tested throughout the study. Experimental data obtained were used to assess the relationship of the above properties with the concrete compressive strength and how these relationships are affected with age. Further, this study investigates prediction models available in literature and recommendations are made for models that are found suitable for application to early age concrete. Results obtained indicate that the relationship between the splitting tensile strength and concrete compressive strength can be approximated with a power function between 0.7 and 0.8, and this correlation is not affected by age. Fracture energy of the concrete and modulus of elasticity values obtained in this study correlate well with the square root of the compressive strength and it was found that this relationship holds true for all hydration ages investigated in this paper. Inverse analysis on the wedge-splitting test was conducted to determine the direct tensile strength. Values of tensile strength obtained from the inverse analysis have been validated numerically by carrying out finite element analysis on the wedge split, and anchor pull-out tests. The ratio of the tensile strength obtained from the inverse analysis to the splitting tensile strength was found to be in the range of 0.5–0.9 and 0.7 on average. Full article

Oil and gas offshore structures are essential infrastructures which are subjected to several categories of environmental loads such as wave and wind actions. These loads commonly designate the structural design of offshore platforms. Additionally, several offshore platforms are founded in earthquake-prone areas and the design of them is intensely affected by seismic ground motions. To be sure, various investigations have studied the earthquake response of offshore structures under the action of far-field seismic events. However, the inelastic behavior of platforms under the action of simple pulses has not been examined yet, where the latter loads can successfully simulate near-fault earthquakes. This work investigates, for the first time to our knowledge, the dynamic inelastic response of offshore platforms subjected to triangular, exponential, sinusoidal, and rectangular pulses. Thus, three-dimensional offshore structures are examined also considering the dynamic soil-pile-platform interaction effects, satisfying all the pertinent provisions of European Codes and taking into account geometric and material nonlinearities as well as the effects of the different angles of incidence of seismic waves on the overall/global response of offshore platforms. Full article

The problem of managing existing structures before and after seismic events has led to the development of many different strategies across the globe. These aim to mitigate the catastrophic effects of earthquakes on the occupants of a building, as well as improve the management of the emergency that inevitably ensues. This paper explores the use of an openBIM approach to resolve the issues referred to above, which is possible because of two new standards: Industry Foundation Classes and Information Delivery Manuals. A review of the most popular strategies adopted in both the pre- and post-earthquake phases is conducted using a process map. This organizes the relevant steps and processes into tasks, and additionally identifies the points at which information is produced and exchanged and the party responsible for doing so. Also described is how BIM models can be utilized in essential pre- and post-earthquake activities, as well as current benefits and ongoing developments intended to improve the processes themselves. Full article

Fastenings are becoming increasingly important in modern building practice. A wide range of products cover for the great flexibility that they provide in a large variety of applications. In order to ensure the safe and economical use of the fastenings, a combined effort of manufacturing firms, practicing engineers and constructors, research organizations, and public authorities has led to the establishment of interrelated design standards, application guidance, and product approvals. It is however evident that failures, in fact even small defects, of fastenings can lead to disproportionate catastrophic events. In addition to these state-of-the-art documents, which reflect the most precise knowledge possible, a management of possible residual risks and hence causes of failure is also indispensable. Due to the great range of fastening systems with different dimensioning and assembly guidelines, load-bearing behaviour and areas of application, and the overall complexity of the subject, a coherent risk management procedure against structural risks can be very helpful in this respect. This article deals with the technical and load-bearing related risks of fastening technology in construction. The objective of the paper is to introduce fundamental concepts and significant risks met in the fastenings design specification and installation. Moreover, it provides a rating of the identified risks and it transfers recommendations for risk mitigation, based on semi-structured interviews with expert professionals who are active in the field. The results are accumulated in a dedicated risk register as a standard tool of the risk management process in civil engineering, which is the first of its kind in current scientific literature. The aim is to assist future practice and research by providing a basis for risk management considerations for fastenings, which moreover reflects actual risks indicated in the outcome of an industry survey. Full article

The excessive production of worn tires remaining from the transportation system and the lack of proper procedures to recycle or reuse these materials have caused critical environmental issues. Due to the rubber’s toughness, this material could be implemented to increase concrete toughness, and by crushing the tires concrete aggregates can be replaced proportionally with rubber crumbs and large quantities of scrapped rubber. However, this substitution decreases the concrete strength. In this study, crushed rubber with sizes from 1 to 3 mm and 3 to 6 mm were replaced by 5%, 10%, and 15% sand; the combination of two additives of nano silica and metakaolin additives with optimum values was used to compensate the degradation of the strength and improve the workability of the concrete. Moreover, the compressive strength, tensile behavior, and modulus of elasticity were measured and compared. The results indicate that the optimum use of nano silica and metakaolin additives could compensate the negative effects of the rubber material implementation in the concrete mixture while improving the overall workability and flowability of the concrete mixture. Full article

The form and the perpendicularity of boreholes influence the ultimate behaviour of post-installed fasteners and are restricted with regard to the concrete surface to 5° in Europe and to 6° in the United States in various regulations (e.g., EAD 330232-00-0601 resp. ACI 355.2-19). It is assumed that the deviation of the borehole from the vertical axis has an effect on the load transfer behaviour of an anchorage. This article investigates on the perpendicularity of vertically downward drilled boreholes using different drilling tools considering hammer drilling, hollow drilling and diamond core drilling. It can be shown that the requirements of e.g., EAD 330232-00-0601 of a maximum deviation to the concrete surface of 5° can be fulfilled for approximately 95% of the determined values for different drilling methods. This is based on a considerable number of measurements (generated from drilled boreholes) in different concrete types. As a result, a detailed statistical evaluation is provided to describe the borehole perpendicularity by means of statistical methods. Full article

Anchor channels are cast in concrete and allow the connection of components using channel bolts. In recent years, the design to value resulted in ever thinner concrete elements, which often cannot accommodate the required embedment depth of standard anchor channels. For this reason, channels may be fitted with short anchors. While existing design provisions allow for the calculation of the tension capacity also for shallow embedded anchor channels, tests are required to determine product-specific parameters for the economic shear loads design. The presented study investigated the performance of shallow embedded anchor channels tested in shear. The detailed evaluation of the test data demonstrates that testing of the minimum embedment is conservative and that the load-displacement behavior of channels with welded I-sections is comparable to that of channels with forged headed studs. In addition, a new evaluation approach is proposed. Full article

The paper reports an experimental campaign to study the effectiveness of strengthening measures proposed for rammed earth (RE) wall in an out-of-plane direction. Two simple and feasible strengthening techniques were explored, namely, mesh-wrapped and timber-framed strengthening techniques. The test involved testing three full-scale U-shaped RE walls in an out-of-plane direction. The first specimen without any intervention served as the reference wall, while the two others were strengthened with two different strengthening methods. It was observed that both proposed strengthening techniques improved the load-carrying capacity of the wall and the maximum displacement and the energy absorption. The mesh-wrapped strengthening technique was found to be more effective than the timber-framed strengthening technique, which disrupted the visual aspects of the wall’s facade and needed proper anchoring to the foundation. Full article

Fire safety is a critical performance aspect of construction products, and post-installed anchors and rebars are no exemption in that regard. During their service life, anchors and rebars are subjected to different kinds of load actions, so they have to be qualified and designed for critical safety performance. While the qualification guidelines for static and seismic loading have matured to conclusive requirements over the past two decades, the requirements for determining the resistance to fire are just about to consolidate. This contribution strives to provide clarity on the fire rating of post-installed anchors and rebars. For this, the current status of the regulations, as well as the underlying background, is reviewed after a brief introduction. Typical examples of fire ratings in the field of post-installed anchors and rebars are given, and recent research undertaken to close the last regulative gaps is briefly presented. Full article

To ensure the stable operation of safety-related nuclear power plant (NPP) equipment, they are tested by following the seismic qualification procedures. The in-cabinet response spectrum (ICRS) is used to test the mounted components. However, the ICRS varies significantly with the number of uncertainties that include (1) loaded and unloaded condition of the cabinets, (2) the number of connected cabinets (grouping effects), and (3) higher frequency contents in the seismic inputs. This study focuses on the ICRS generation and alteration induced due to the listed uncertainties. A prototype of an electrical cabinet was experimentally examined. Followed by the numerical modeling of the cabinet, the seismic analysis for the group of cabinets was performed using artificial ground motion compatible with the standard design spectrum and the real accelerograms of high and low frequency contents. The seismic response using finite element (FE) analysis manifests (1) natural frequency of loaded cabinets reduced due to the in-cabinet components while for the unloaded cabinets it increased significantly, (2) a consistent reduction in ICRS due to the grouping effect was recorded when excited by the lower-frequency motion, while it was amplified dramatically due to high-frequency pulses. Interconnected cabinets under the low-frequency input motions have a significant reduction of 50% in the ICRS that corresponds to the higher stiffness of the cabinets, while a 100% increase under the high frequency of ground motion was obtained. High frequency of ground motion, usually above 10 Hz, can cause the interconnected cabinets to resonate as the natural frequency of these equipment lies in this range. Full article

The aim of this work is to reduce the overexploitation of river sand by proposing a combination of crushed sand and river sand to develop an optimal mix design for concrete. The approach used consisted of a physical, chemical, and mineralogical characterization of aggregates from three quarries located in Yaoundé (Cameroon), followed by the formulation of concrete by substituting 100%, 90%, 80%, 70%, 50%, and 0% of the river sand with crushed sand. A physical and mechanical characterization of the concrete was carried out, as well as a microstructural characterization using SEM/EDS. The results showed that the concrete made of crushed sand only had a higher drying shrinkage at a young age compared to the river sand concrete. Compared to conventional concrete (made using 100% of river sand), the concrete with 50% crushed sand reduces its slump value, has a lower porosity, and has a compressive strength value of 26.3 MPa at 28 days, which is very similar to that of conventional concrete (26.7 MPa). Moreover, it was found that the strength of the concrete increased by 14.4% and 20.6%, respectively, for concrete without crushed sand (BSR0) and concrete with 50% crushed sand (BSR50) by increasing the curing age from 28 to 90 days. The static modulus of elasticity for conventional concrete BSR0 and BSR50 concrete with 50% crushed sand at 90 days was 23.7 and 21.8 GPa, respectively. Thus, combining crushed sand with alluvial sand is a good method to reduce the depletion of alluvial sands in Cameroon. Full article