Anchors In Concrete Research Articles

Analysis of Temperature Sensitivity and Cracking Causes in Suspension Bridge Anchorage Based on Numerical Simulation

Mass concrete, a common structure in bridge engineering, is frequently threatened by cracking. Based on the gravity anchorage of a long-span suspension bridge that has been in operation for more than ten years, the causes of the cracks growing year by year in the anchorage were analyzed in this paper. The refined numerical model of the anchorage was established using the space finite-element software. Taking full account of the environmental characteristics of the bridge site, the temperature sensitivity of the anchorage was simulated and analyzed, as well as the stress distributions on the surface of each side of the anchorage at different temperatures. The calculation results showed that there is little correlation between anchorage cracking and anchorage bolt force. Under condition two, the temperature increased 20°C, the principal tensile stress of anchorage reached to 1.5 times of the allowable stress. Under condition six, the anchorage surface temperature at 40°C suddenly dropped to 20°C, and the principal tensile stress reached 2.4 times the allowable stress. Thus, under the dual effects of internal and external constraints, the cold hit effect of the mass concrete anchorage resulted in the sudden drop of the surface temperature of the anchorage concrete to produce “internal constraint cracks”, and the overall temperature rise caused the expansion of the anchorage concrete to produce “external constraint cracks.” The two types of cracks led to the vertical cracks of the anchorage. Additionally, the environmental and construction factors were the main causes of the cracking in transverse construction joints. Finally, the anchorage was reinforced with high-performance concrete with an anticrack reinforcement mesh, which presented good results in the follow-up observation, providing a certain reference value for similar projects.

Investigation on mechanical properties of lightweight sandwich exterior wall with thermal blocking shear connector

In order to solve the problems of obvious thermal bridge effect for metal shear connectors and the lower shear bearing capacity for non-metal shear connectors, two new types of thermal blocking shear connectors (TBSC) were investigated. One is made by bond stress between glass fiber reinforced polymer (GFRP) sleeve and reinforcement, and the other is made by mechanical connection between the steel sleeve and GFRP bar. The goal is to study the mechanical properties of the lightweight sandwich exterior wall with TBSC. There are 18 specimens were conducted based on the mechanical properties, and the parameters of different types, different embedded depths and different bending angles were considered. The pull-out and direct shear tests were carried out, and each parameter's influence on the result was compared and analyzed. The test results show that with the increase of bending angle, the bearing capacity of GFRP sleeve TBSC increases. When the embedded depth of the TBSC increases from 25 mm to 40 mm, the pull-out test and direct shear test values increase by 95 % and 59 %, respectively. The main failure mode of specimens is the concrete anchorage failure. According to the phenomenon of concrete anchorage failure, the calculation formulas of flexural and direct shear capacity were proposed. Moreover, the finite element simulation is used to extend and validate, providing a theoretical reference for designing and applying a lightweight sandwich external wall with TBSC.

Shear behavior of single cast-in anchor simulating characteristics of bridge bearing anchor

A bridge bearing anchor transmits various loads of a superstructure to a substructure. Most anchors are generally designed without consideration of characteristics such as concrete pedestal, grout bedding, and anchor socket. This study investigated the shear behavior of anchors in accordance with the edge distance, embedment depth, compressive strength of concrete, and height of the concrete pedestal in order to simulate the practical characteristics of the bridge bearing anchors. The actual shear capacity of the anchor differs from the shear strengths calculated by the ACI 318 and EN 1992-4; especially, the importance of the embedment depth is underestimated in these codes. An increase in the height of the concrete pedestal has a negative effect on the shear capacity because of the stress concentration. The grout is fractured prior to the occurrence of local damages in concrete, resulting in a secondary moment. As a result, the effect of the level arm is observed. An equation, which can predict the relative cracking degree of concrete, is proposed by analyzing the displacement of grout and concrete. High strain occurs in the stirrups close to the anchor, and the behavior of the strain is more influenced by the embedment depth than the edge distance. The comparison of obtained and analytically evaluated failure loads by calculations according to EN 1992-4, Schmid model and Sharma model was conducted to consider the effect of supplementary reinforcement. Finally, the design equation of concrete breakout strength is modified to predict the more precise shear resistance of a bridge bearing anchor.

Data-driven machine learning prediction models for the tensile capacity of anchors in thin concrete

Data-driven machine learning prediction models for the tensile capacity of anchors in thin concrete

Stability Analysis of Concrete Block Anchor on Steep-Slope Floating Breakwater

The floating breakwater is a protective structure that can absorb waves and can be used effectively in coastal areas with moderate wave environmental conditions. The stability of the floating breakwater is affected by the tension of the mooring line and the weight of the anchor. This research was conducted experimentally with a model scale of 1:10 on a floating breakwater with mooring systems and concrete anchor blocks with three types of configurations. The experiment was carried out on irregular waves with the following variations: wave height and period, mooring angle, structure width, and anchor weight. The results of this study indicate that at a wave steepness of 0.02–0.025 floating breakwater, which is installed with a mooring angle of 45 deg, configuration 3 has the largest stability parameter among other configurations. However, if the structure is installed at a mooring angle of 90 deg and cross, configurations 2 and 3 have almost the same stability. The test results also show that the relative width will affect the stability parameters. Configuration 3 (B = 30 cm) has the largest stability-parameter value among other configurations (B = 10 cm and 20 cm).

Tensile behaviour of cast-in headed anchors in ambient-temperature cured geopolymer concrete

In recent years, the construction and research community have gained interest in geopolymer concrete as it uses fly ash as an alternative to normal concrete using Portland cement. Geopolymer concrete is more suited for off-site or precast construction due to the requirement for laboratory prepared alkaline solution in the production and its high susceptibility to temperature variation at an early age, hence the need for a controlled environment. Cast-in anchors are usually used as a lifting insert in precast members. Currently, researchers and practitioners rely on the well-established concrete capacity design (CCD) model to predict the concrete cone capacity of anchors in all types of concrete. However, research is still ongoing to determine the suitability of the CCD model for the use of anchorages in different types of concrete. For geopolymer concrete, the CCD model may be non-conservative because of its much lower mode I fracture energy and elastic modulus compared to its normal concrete counterpart. In this study, the tensile behaviour of cast-in headed anchors is investigated in ambient-temperature cured geopolymer concrete. Anchors of varying sizes (1.3 T, 2.5 T and 5 T) were installed at effective embedment depths of 40 mm, 70 mm and 90 mm. The results show that the CCD model overestimated the capacity of anchors in geopolymer concrete by 40%, whereas, the linear fracture mechanics (LFM) model predicted the capacity of the anchor with sufficient accuracy. The results also show a significant influence of anchor head size on the anchor capacity, displacement at peak loads and concrete cone size. Compared to anchors installed in normal concrete at the same compressive strength, the results show a 25% lower capacity in tension.

Calculation model of shotcrete support thickness based on elastic thin plate theory

In order to accurately calculate the thickness of shotcrete in tunnel, the support load, inter-anchor row distance and concrete mechanical properties are selected as influencing factors, and a mechanical model of shotcrete support thickness is established based on the elastic thin plate theory to derive the relationship between support load, inter-anchor row distance, concrete mechanical properties and concrete thickness. The controlled variable method (CVM) was used to study the variation law of support load and inter-anchor row distance with concrete thickness. The results show that: the mechanical properties of the concrete slurry remain unchanged, the required thickness of the concrete support increases with the increase of the support load, in a power of 1/2 relationship, with the increasing thickness of the shotcrete, the concrete is prone to shear damage to tensile damage until the thickness meets the engineering requirements; the support load remains unchanged, the thickness of the concrete support is linearly related to the anchor rod spacing, with the increase of the anchor rod spacing As the anchor spacing increases, the required thickness of concrete support also increases linearly. This paper successfully defines the relationship between the required concrete support thickness, support load and anchor rod parameters for shear and tensile damage, and through the analysis of the anchor spraying case, it is believed that the calculation model is reasonable and the results can provide a theoretical basis for the quantitative design of the support system.

Assessment of the tensile behaviour of post-installed screw anchors in early age concrete

This study investigates the tensile behaviour of post-installed screw anchors in early-age concrete. The investigation included an experimental study including testing of 38 screw anchors at 6 different hydration ages. The experimental program aimed to investigate: (i) the effect of early-age installation on the 28 day behaviour; (ii) and performance when screw anchors are installed and tested in early-age concrete. The experimental results demonstrated the capability of the concrete capacity method model in capturing the behaviour of screw anchors in early-age concrete with reasonable accuracy. Further, early-age installation of screw anchors did not impact the performance of the anchors when tested in tension at 28 days. This study also included a detailed finite element analysis of screw anchors in early-age concrete to further understand the behaviour of this type of anchors and the failure mechanism governing the capacity under pure tension loading.

Multilateral Assessment of Anchorage Bond Characteristics in Steel Fibre Reinforced Concrete.

Anchorage to concrete is a recurring application in construction. For such applications, bonded anchors, formed by means of a polymer adhesive injection into a borehole, are a widely used product due to their flexibility in regards to the construction logistics and positioning of the attached element as well as high load capacities. At the same time, fibre-reinforced concrete is the material of choice for many engineering applications where anchors have to be installed. Moreover, the use of steel fibre-reinforced concrete is likely to increase, since it now falls in the scope of the second-generation Eurocode 2 (exp. 2023). Therefore, the condition of the anchor installation borehole—mainly the roughness and grip of its internal surface—is known to play a critical role in the stress transfer from the attached component, through the fastening and into the concrete, and, hence, to the load-bearing performance. At the same time, drilling through the steel fibre reinforcement, along with the accelerated wear of the drilling tools, can in turn influence the borehole’s roughness and the overall installation quality. Furthermore, steel fibre may lead to an additional local stiffening of the concrete where the anchor is installed. These complex elements are discussed herein on the basis of multiple tests on anchors in plain and steel fibre concrete, as well as numerical analyses. The results indicate particular aspects of bonded anchor design and product certification for different polymer-based construction adhesives.

Enhanced service life of existing infrastructure buildings by use of concrete screw anchors as post-installed shear reinforcement

In the last decades, traffic on railways and roads has increased significantly in Central Europe. On the other hand, the existing infrastructure mainly origins from the late 1950s to the 1970s. This applies also for the existing bridge and tunnel infrastructure which is now up to 60 years old. Due to this age and new standards in the current codes, quite often the amount of shear reinforcement does not fulfil the current design code rules. As a replacement of existing structures is often highly unsustainable, methods to improve the shear strength are needed. Therefore, a new system for post-installed shear reinforcement by the use of concrete screws was developed at the University of Innsbruck in the last years. The idea is to use concrete screw anchors - already known as anchoring element - aspost-installed reinforcement. In over 60 shear tests with girders and slabs the excellent applicability of concrete screw anchors as post-installed shear reinforcement has been proven. Also shear tests with cyclic loading were performed prove the use for dynamically loaded structures, such as bridges. Based on these test results a design approach was determined to meet the Eurocode-2 assessment standards.Several pilot-projects with concrete screws have been realised in Austria and Germany. For example a rail-road-bridge over a German highway with a remaining service life of zero years was strengthened to a new service life of over 20 years. Also a city-centre tunnel in Munich which was erected below a historic building is currently strengthened under ongoing traffic in the tunnel using concrete screw anchors as post-installed reinforcement.

Shake table tests of concrete anchors for non-structural components including innovative and alternative anchorage detailing

In recent years, the growing need for reducing non-structural damage after earthquakes has stimulated a dedicated effort to develop innovative types of fasteners for anchoring non-structural components (NSCs) to reinforced concrete (RC) host-structures. To contribute to such need, and building on previous research, this paper presents the results of a series of uni-directional shake-table tests of simulated NSCs anchored to concrete via: (1) expansion, and (2) chemical anchors; post-installed into: (a) uncracked, and (b) cracked concrete. Considering different construction details, the experimental investigation focused on traditional anchorage systems, alternative solutions comprising mortar filling into the gap clearance, and a low-damage system relying on supplemental damping devices, capable of reducing the acceleration of the NSCs as well as the force of the anchorage during seismic shakings. The experimental tests provided significant evidence on the beneficial effects of a dissipative anchorage protecting both the non-structural component and the anchorage itself, even during strong earthquakes. Moreover, when construction details allow to close the fixture clearance with a mortar filling, this stiffer solution provide an additional reduction of NSCs seismic accelerations and forces. Therefore, suggestions for further improvements of the adopted low-damage solution are also proposed.

Tensile Performance of Headed Anchors in Steel Fiber Reinforced and Conventional Concrete in Uncracked and Cracked State.

Steel fiber reinforced concrete (SFRC) is currently the material of choice for a broad range of structural components. Through the use of SFRC, the entire, or a large portion of, conventional rebar reinforcement can be replaced, in order to improve the load-bearing behavior but also the serviceability and durability characteristics of engineering structures. The use of fiber reinforcement therefore plays a vital role in acute current and future construction industry objectives, these being a simultaneous increase in the service life of structures and the reduction of their environmental impact, in addition to resilience to extreme loads and environmental actions. Next to the extended use of SFRC, modern construction relies heavily on structural connections and assembly technologies, typically by use of bolt-type cast-in and post-installed concrete anchors. This paper addresses the influence of fiber reinforcement on the structural performance of such anchors in SFRC and, particularly, the load bearing behavior of single headed anchors under axial static loads in uncracked and cracked concrete. Along with a presentation of background information on previous studies of SFRC with a focus on anchor concrete breakout failure, the experimental investigations are described, and their results are presented and elaborated on by consideration of various research parameters. A comparison with current design approaches is also provided. The conclusions are deemed useful for structural engineering research and practice.

First trial of wild juvenile collection of tropical sea cucumbers from settling larvae, using coconut fibre from waste husks in Solomon Islands: A new conservation tool

Abstract Wild juvenile collection (WJC) from settling larvae has been reported for two temperate holothurians (Apostichopus japonicus and Apostichopus californicus), mainly for the objective of restocking, but its applicability to tropical holothurians is unknown. This study, for the first time, tested the applicability of WJC for tropical sea cucumbers. First, hatchery‐produced larvae of peanutfish (Stichopus horrens) before settlement were introduced in a tank in which bundles of coconut fibre, rolled mesh bags, and oyster shells were suspended to identify the most suitable settlement material. The results showed that the coconut fibre and mesh bags collected more settling larvae than the oyster shells. Second, 25 collectors were installed for 3 months in the field in Nggela, Solomon Islands. The newly designed simple collector comprised between two and four net bags filled with coconut fibre, which were tied to a rope vertically moored between a concrete block anchor and polyethylene terephthalate (PET) bottle floats. A total of 14 juvenile holothurians were collected, including Stichopus cf. horrens, stonefish (Actinopyga lecanora), kingfish (Synapta maculata), and five unidentified species. It is characteristic of tropical WJC that diverse species can be collected simultaneously (including rare, non‐culturable species), which is advantageous over hatchery production for restocking purposes. The total yield corresponded to approximately 1% of the total abundance of the ambient holothurian community, demonstrating potential for restocking, considering the ease of the extension and repetition of the trials. Collection in the inner bay areas was successful, whereas rough weather physically damaged the collectors in areas open to the ocean. These results show that WJC is a viable option for tropical holothurians. Thus, the use of the low‐cost, simple collectors using coconut fibre could be a new conservation measure for endangered holothurian resources, and are manageable by local communities.

수상태양광 접지방안 분석

Floating Photovoltaic(PV) is one of the promising renewable alternative to replace fossil fuel energy. One of the issues about Floating PV(FPV) is how to ground its conductive materials effectively. Currently, the ground regulation of FPV denotes that grounding wire should not be floated in the water and laid in the ground. However, it is said that specific resistance of water is not higher than that of soil and water could be analyzed as soil. Two methods of water ground is suggested as water rectangular ground wire and conductive concrete anchor grounding. Test site of 100㎾ FPV is utilized to measure grounding resistance for each methods and GroundMat of PTW(Power Tools Window) is adopted to compare actual and theoretical values.

Methodology for development of AS 5216 using international harmonisation of construction products standard

ABSTRACT The adaptation of the design rules from one country for use in another country is becoming more frequent with growing international trade. For construction products, an individual country, however, still requires conformity assessment of the design rules to its own building regulation. Direct adoption of the design rule is usually not feasible due to differences in design format and material properties specifications. This paper demonstrates the process of adaptation of international design procedures to develop the Australian Standard AS 5216 for metal anchors (fasteners) in concrete. The original European design provisions has been adapted for Australian use. The paper outlines what factors need to be considered in the adaptation process for international harmonisation of structural design for metal anchors in concrete. Furthermore, the paper demonstrates the workability ofBV1 Verification Method in the Australian National Construction Code (NCC) and its limitations for the purpose of demonstration of conformity.

Improving the punching shear and shear capacity of reinforced concrete elements with a new post-installed retrofitting system

Finding appropriate strengthening solutions for existing reinforced concrete (RC) elements is always a challenge for structural engineers. Additional load capacity may be needed as the change of type of occupancy and more restrictive design standards require higher load levels or different detailing of reinforcement. This paper introduces a post-installed retrofitting system consisting of an adhesive and a concrete screw anchor that can be used to improve either the pure shear capacity or the punching shear capacity of a RC beam or slab. This post-installed retrofitting system acts as shear reinforcement that can be installed with relatively minimal disruption as it is only installed at the soffit of the RC element being strengthened. The system was tested for its suitability and the results were approved by the German Construction Authority with a National Technical Approval. Published parameters are used for the standard methods of detailing shear and punching shear of a RC element according to EN1992-1 and EN1992-2. Calculations and tests have shown that with the use of this post-installed retrofitting system, the shear strength of existing concrete elements can increase by up to 100% and consequently increase the lifetime of a structure. This paper also discusses the test methods employed, the test results, and sample projects that made use of the said system. Another important finding is the substantial savings in project cost attributed to the installation methodology that comes with the system.

ОБОСНОВАНИЕ ПАРАМЕТРОВ ПРОЧНОСТИ И УСТОЙЧИВОСТИ ГОРНОЙ ВЫРАБОТКИ В СИСТЕМЕ «ПОРОДНЫЙ МАССИВ – АНКЕР –МОДИФИЦИРОВАННЫЙ БЕТОН»

The absence of a rock mass anchoring in the Donetsk basin using modified concrete reduces the safety of mining operations and does not ensure its long-term strength and stability in the workings of deep coal mines. The object of the research is mining in the system "rock mass – modified concrete anchor". The subject of the research is the substantiation of the strength and stability parameters of mining. The purpose of the research is to reveal the regularities of the stress–strain state of the "rock mass - modified concrete anchor" system to substantiate the parameters of fixing the rock mass, ensuring the safety of mining operations, increasing stability and reducing the cost of mining deep coal mines. The research methods: mathematical modeling of the stress-strain state of the "rock mass – anchor – modified concrete" system. The design scheme of a rock mass presented in the form of a thick shell with anisotropic layers of rocks under the influence of rock pressure and two boundary conditions is considered. A mathematical model of the stress-strain state (VAT) of the "rock mass-anchor-modified concrete" system is given. The obtained results of stress studies and a nomogram for the dimensionless quantities determination allowed the authors to substantiate the parameters of the system that ensure its strength and stability in the mine workings of deep coal mines.

Multiaxial Fatigue Life Assessment of Integral Concrete Bridge with a Real-Scale and Complicated Geometry Due to the Simultaneous Effects of Temperature Variations and Sea Waves Clash

In the present study, the authors attempted to predict the fatigue lifetime of a real-scale integral concrete bridge with H-shaped steel piles resulting from working and environmental conditions. In this regard, various types of nonproportional variable amplitude loads were applied on the bridge, such as temperature variations and sea waves clash. To this end, CATIA software was used to model the real-scale bridge with its accessories, such as a concrete deck, concrete anchors (walls), I-shaped concrete beams (Ribs), and steel piles. Subsequently, stress analysis was performed to determine the critical area apt to fail. The results showed that steel piles are the most critical bridge components. As a result, in future analysis, the purpose will be to study this critical area, and the effect of relative humidity on the fatigue properties of concrete was ignored. Subsequently, the time history of stress tensor components in the critical area was obtained by performing transient dynamic analysis. Various well-known equivalent stress fatigue theories (von Mises, Findley, Dang Van, McDiarmid, Carpinteri–Spagnoli, Modified Findley, Modified McDiarmid, and Liu–Zenner) were utilized to calculate the equivalent stress caused by the simultaneous effect of temperature variations and sea waves clash. Eventually, the fatigue life of the structure was predicted by employing the rainflow counting algorithm and the Palmgren–Miner damage accumulation rule. The results indicated a reduction in the multiaxial fatigue life of the structure under the simultaneous effects of two phenomena, the daily temperature variations and the sea waves clash, of approximately 87% and 66%, respectively, compared with the fatigue life of the structure under either the effect of temperature changes or the effect of sea waves clash, separately. Therefore, it was necessary to consider all the cyclic loads in the structural design step to estimate the fatigue life of the structure. Moreover, the findings of this case study revealed that the lowest value of multiaxial fatigue lifetime is related to the application of the Liu-Zenner criterion. In other words, this criterion is more conservative than the other used criteria.

Effect Steel Fibre Content on the Load-Carrying Capacity of Fibre-Reinforced Concrete Expansion Anchor.

The article presents the pull-out strength tests carried out on M10 expansion anchors in non-cracked and cracked concrete with a crack width cw = 0.30 mm. The breaking loads and the average pull-out strength of anchors in fibre-reinforced concrete substrates were determined. Fibre content ratios of 15, 30 and 50 kg/m3 were used. In addition, two different classes of concrete (C20/25 and C50/60) were tested. The addition of steel fibres caused a decrease in the pull-out strength by 5% for non-cracked concrete of C20/25 class and fibre content up to 30 kg/m3 and a further 7% for the remaining specified dosage. While for concrete of the C50/60 class, it a decrease in the pull-out strength of up to 20% was observed. For cracked concrete class C20/25 with crack initiation cw = 0.30 mm, the reduction was from 9% to 16% in relation to non-cracked concrete and a maximum of 18% for the fibre content of 50 kg/m3. The difference between the tensile load capacity of C50/60 class cracked and non-cracked concrete was lower than 5% and fell within the measurement error.

Design, construction and monitoring of concrete roadway pavement at extremely steep longitudinal slopes

ABSTRACT Most conventional roadway pavements are not constructed at grades greater than 15% due to construction limitations and/or motor vehicle operator safety concerns; however, there are conditions, especially in the developing world, where roadways must be built at extremely steep longitudinal slopes. Currently, there are limited published design procedures for extremely steep concrete roadways, and little guidance on either the type, shape, or spacing of sliding restraint devices for these pavements. This paper presents an original design methodology for concrete roadways at slopes of 15–60% with integral concrete lug anchors to resist sliding where the design computes a sliding factor of safety of the earth pressure resistance developed by the lug anchors as compared to the downhill forces acting on the concrete pavement from gravity, vehicle loading and vehicle braking. A case study of a concrete roadway construction project, which uses the lug anchor design methodology with slopes of 23–58% and with limited right of way, is also presented. Many valuable lessons were learned during the construction of a roadway at such steep grades, including novel ways to transport and place fresh concrete and the fabrication of specialised equipment to screed and smooth concrete on a steep slope.