Performance of maturity method for estimation of concrete strength based on cubic specimens

To assess the condition of the structures of buildings and structures, a comprehensive analysis of the factors affecting their performance characteristics - concrete strength, protective layer, and rebar diameter, thermal conductivity and moisture content of concrete, adhesion of protective and facing coatings, frost resistance and water resistance of concrete - is required. However, with all the variety of monitored parameters the control of concrete strength has a special place because when assessing the condition of the structure the determining factor is the compliance of the actual strength of concrete to the design requirements. This paper presents studies on the determination of concrete strength based on modern technology, wireless sensor as well as instrumentation IPS. These methods are particularly effective in the case of non-linear relationships between different system parameters, as in the behavior of concrete parameters. They can also provide rapid measurements by continuously monitoring the internal condition of the reinforced concrete structure. The features of each method are given, as well as an analysis of the convergence of the results.

Aspects of Selecting Appropriate Conveyor Belt Strength

Breaks in the so-called “continuous” (unspliced) belt sections, and not in the spliced areas, are infrequent but do happen in practice. This article presents some aspects, which may account for such breaks in conveyor belts. It indicates the so-called “sensitive points” in design, especially in the transition section of the conveyor belt and in identifying the actual strength of the belt. The presented results include the influence of the width of a belt specimen on the identified belt tensile strength. An increase in the specimen width entails a decrease in the belt strength. The research involved develops a universal theoretical model of the belt on a transition section of a troughed conveyor in which, in the case of steel-cord belts, the belt is composed of cords and layers of rubber, and in the case of a textile belt, of narrow strips. The article also describes geometrical forces in the transition section of the belt and an illustrative analysis of loads acting on the belt. Attention was also devoted to the influence of the belt type on the non-uniform character of loads in the transition section of the conveyor. A replacement of a conveyor belt with a belt having different elastic properties may increase the non-uniformity of belt loads in the transition section of the conveyor, even by 100%.

The Size Effects of Point Defect on the Mechanical Properties of Monocrystalline Silicon: A Molecular Dynamics Study

The molecular dynamics method was used to simulate the fracture process of monocrystalline silicon with different sizes of point defect under a constant strain rate. The mechanism of the defect size on the mechanical properties of monocrystalline silicon was also investigated. The results suggested that the point defect significantly reduces the yield strength of monocrystalline silicon. The relationships between the yield strength variation and the size of point defect fitted an exponential function. By statistically analyzing the internal stress in monocrystalline silicon, it was found that the stress concentration induced by the point defect led to the decrease in the yield strength. A comparison between the theoretical strength given by the four theories of strength and actual strength proved that the Mises theory was the best theory of strength to describe the yield strength of monocrystalline silicon. The dynamic evolution process of Mises stress and dislocation showed that the fracture was caused by the concentration effect of Mises stress and dislocation slip. Finally, the fractured microstructures were similar to a kind of two-dimensional grid which distributed along the cleavage planes while visualizing the specimens. The results of this article provide a reference for evaluating the size effects of point defects on the mechanical properties of monocrystalline silicon.

Methods for Advancing an Open, Replicable, and Inclusive Science of Social Cognition

This chapter is divided into three sections. In the first section, we describe concrete practices that researchers can use to calibrate their confidence in a significant finding to the actual strength of evidence provided by that finding. In the second section, we discuss how researchers can calibrate the scope of the conclusions they draw from a study to the stimuli and participants sampled in that study. In the third section, we highlight the importance of approaching scientific inquiry from diverse vantage points, and provide specific recommendations for enhancing diversity and inclusion in social cognition research. Together, these three sections offer researchers a roadmap for enhancing what we learn from the work that we do.

Towards a Robust Offshore Bonded Repair Strength Evaluation

Since the early 2000s, the number of Floating Production, Storage and Offloading (FPSO) units is increasing significantly. And so now, half of the fleet is over than 10 years old. As FPSO are mainly installed in tropical areas, with marine environment, high temperature and high humidity, corrosion is a permanent threat. Maintenance of steel structures become a challenge for oil major companies in offshore operation. Indeed, when allowable corrosion limit are reached, plates are to be repaired. However the current “crop and renew” technique implies a number of major issues for owners such as: “hot work”, i.e., welding; temporary structure weakening; necessity to empty, clean and vent oil tanks, leading to a long down time and an expensive solution. “Cold repair”, such as bonded repair, is an obvious solution, due to a short down-time and non-intrusively process. However, currently no standards or rules exist for this kind of repair and engineering faces problems as basic as strength qualification. To address the lack of knowledge on the strength assessment of bonded repair for primary structure, Bureau Veritas Marine & Offshore launched a Joint Industrial Project (JIP) named StrenghBond Offshore with oil companies, shipyards and suppliers. The main objectives of the JIP are to: Assess short term and fatigue strength of typical bonded repairs, Enrich knowledge of adhesive joints strength on typical offshore repairs cases, Enable a better evaluation of the margin between the actual strength of a repair and the design load, Validate the characterisation procedure for strength prediction of bonded assembly, Define a robust strength prediction method, Gather the collected experience in a industrially applicable guideline, Standardise qualification process for offshore composite bonded repairs. The project intends to provide a design approach for bonded reinforcement that is design orientated, accurate and recognized by the offshore industry.

Gear root bending strength: a comparison between Single Tooth Bending Fatigue Tests and meshing gears

Gear tooth breakage due to bending fatigue is one of the most dangerous failure modes of gears. Therefore, the precise definition of tooth bending strength is of utmost importance in gear design. Single Tooth Bending Fatigue (STBF) tests are usually used to study this failure mode, since they allow to test gears, realized and finished with the actual industrial processes. Nevertheless, STBF tests do not reproduce exactly the loading conditions of meshing gears. The load is applied in a pre-determined position, while in meshing gears it moves along the active flank; all the teeth can be tested and have the same importance, while the actual strength of a meshing gear, practically, is strongly influenced by the strength of the weakest tooth of the gear. These differences have to be (and obviously are) taken into account when using the results of STBF tests to design gear sets. The aim of this paper is to investigate in detail the first aspect, i.e. the role of the differences between two tooth root stress histories. In particular, this paper presents a methodology based on high-cycle multi-axial fatigue criteria in order to translate STBF test data to the real working condition; residual stresses are also taken into account

Predicting strength of Finnish birch veneers based on three different failure criteria

The use of wood in high-performance composites based on laminated veneer products, plywood or wood hybrid elements thereof requires accurate prediction of strength of each individual ply. Previous research has shown that one dominating factor influencing the strength of birch veneers is the fibre orientation. The present study investigates the validity of the failure criteria after Tsai-Hill, Hoffmann and Kollmann for thin birch veneers under tensile loading. The fibre orientation in- and out-of-plane was measured by means of wide-angle X-ray scattering. Tensile strength and threshold values were determined in laboratory experiments. Pearson correlation between the predicted strength and actual strength ranged from 0.836 up to 0.883. Best correlation (r = 0.883) was achieved for Kollmann using a combined angle between in- and out-of-plane fibre orientation. It was shown that the failure criteria commonly used for manmade fibre reinforced composites are also applicable for thin birch veneers.

Evaluation of Concrete Breakout Capacity of Single Anchors at Bridge Bearing Connection under Shear Loading

In this study, the breakout capacity of a single anchor specimen in concrete simulating the bridge bearing connection with the characteristics of reinforcement, anchor socket, bed concrete, and mortar was evaluated for shear. The concrete breakout capacities were compared based on the embedment length of the anchor socket and edge distance, and the difference between the existing design strength and the actual strength was determined, which indicated safety issues. In addition, the shear resistance performance of the effective anchor reinforcement was evaluated through the strain analysis of the reinforcement. Finally, Through the results of this study, a concrete breakout capacity formula that reflects the characteristics of the bridge bearing connection has been proposed.

Load bearing capacity and cracking resistance to off-center compression of hollow concrete blocks

The research is about concrete hollow blocks that have been and still are used widely in basement wall construction. It shows that only 10… 30% of their strength is used even for mid and high-rise construction. Therefore massive foundation blocks should be made with hollows. By design, optimized blocks can be combined into the following groups: with large cavities, open from below, with vertical closed and through cavities, horizontal cavities and ribbed. The developed designs of effective blocks of walls of basements potentially give the chance to facilitate them considerably and to save concrete. However, almost of the proposed solutions have not been widely used in practice - mainly due to technological problems. It is necessary to continue the search for effective structural and technological solutions of basement wall blocks and their research. The article shows the result of experimental and theoretic research of two types of concrete blocks: FBH-1 with two top opened hollows and FBH-2 with 4 enclosed hollows. FBH-2 block has hollows with arbolite insertions. His type is efficient for basement external wall due superior thermal performance. The blocks were texted as a part of 3-storey masonry of 1.8 m height applying off-centric loads to it. Those texts allowed to get its actual strength capacity as well as cracking resistance. The load bearing capacity and cracking resistance have been calculated using a deformation method according to current codes. The method takes into account an idealized diagram of concrete stretching.The calculations according to developed method showed satisfactory matching with experimental data of load bearing capacity and cracking resistance.

STRONG TEST PRESSURE CONCRETE USE OF ASBEST WASTE

Concrete is a significant and most dominant material used in building structures. Concrete consists of a mixture of cement, aggregate, water, and added ingredients. Concrete said material has an essential role in making concrete because it can change the real properties to suit the needs. Li, asbestos is a concrete-added material that can reduce the use of cement and produce concrete with absolute consistency. The purpose of this study was to determine how the effect of adding asbestos waste to cement. The method used is an experimental method based on previous research. The specimen used was cylindrical with a diameter of 15 cm and a height of 30 cm. The percentage variation of asbestos waste addition is 0%, 50%, and 100% of the weight of cement used. Typical concrete test results obtained an average value of 22.08 MPa, a 50% percentage produces an average compressive strength of 21.32 MPa, and a portion of 100% provides a compressive strength of 22.93 MPa. Then the results of the then actual strength test have increased in the percentage of asbestos waste 100%.