scholarly journals Analysis of the Behaviour of Rocks Under Cyclic Loads

2021 ◽  
Author(s):  
Marilena Cardu ◽  
Simone Saltarin ◽  
Carmine Todaro
Keyword(s):  
Structural Design ◽  
Cyclic Load ◽  
Historical Review ◽  
Cyclic Loads ◽  
Case Histories ◽  
Mining Operations ◽  
Rock Materials ◽  
Cyclic Stresses ◽  
Different Types ◽  
Rock Parameters

The cyclic load applied to civil and mining structures can lead to a reduction of the materials’ strength, different from that which would occur with a monotonous load. Numerous cases can be found where the decay of the rock parameters subjected to this type of stress leads to progressive or sudden collapse: among them, tunnel walls, pillars and slabs in mining operations, roads with a heavy vehicle transit, abutments of bridges and dams can be quoted. The topic can therefore be fundamental for a correct structural design, to avoid problems during the life of the structure. However, given the heterogeneity of the rock materials and the difficulty of their characterization under this aspect, an unequivocal analysis is hardly achievable. Then, the discussion initially develops through a general historical review of the concept of fatigue, with a synthetic collection of case histories. The laboratory tests on rock samples are then examined and the most important results obtained are discussed. Finally, a comparison between different types of tests is proposed. The experimental data are expressed through the Wӧhler diagram. The goal is to fill the lack of design codes or standards in the field of cyclic stresses applied to rock materials, the understanding of its effect being of great interest in order to apply suitable parameters in the design phase.

scholarly journals Comparison of Safety Factor Values for Soderberg and DIN 743 Fatigue Analyses

2021 ◽  
Vol 7 (2) ◽  
pp. 11-21
Author(s):  
Beatriz Henriques ◽  
Mariana Carvalho ◽  
Sérgio Tavares ◽  
Paulo De Castro
Keyword(s):  
Safety Factor ◽  
Cyclic Load ◽  
High Cycle Fatigue ◽  
Load Capacity ◽  
Cyclic Loads ◽  
Correction Factors ◽  
Fatigue Design ◽  
Different Types ◽  
Machine Elements ◽  
Critical Aspects

Fatigue phenomena are critical aspects of the life cycle of many components or structures. The variety of cyclic load situations led to the emergence, throughout the years, of different types of studies as high-cycle, low-cycle, and fatigue crack growth, among others. Particularly for machine elements, high-cycle fatigue situations are the more frequent, and simplified approaches taking into account the Soderberg criterion have been commonly used. Meanwhile, the German Institute for Standardization put forward a procedure for fatigue design of shafts, DIN 743, based on the use of Smith diagrams and considering separately the safety factor (SF) for static and for cyclic loads. The present paper compares Soderberg and DIN 743 approaches, focusing on SF obtained when load capacity is calculated considering equal correction factors in both methods. A set of representative situations was defined, and the comparison was carried out parametrically using Matlab software. The SF values of the Soderberg method were always found to be lower than those of DIN 743, indicating that the Soderberg method is more conservative than DIN 743.

scholarly journals Integration of different-quality data in short-term mining planning

2015 ◽  
Vol 68 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Cristina Paixão Araújo ◽  
João Felipe Coimbra Leite Costa
Keyword(s):  
Mineral Exploration ◽  
Quality Data ◽  
Imprecise Data ◽  
Short Term ◽  
Mining Operations ◽  
Different Types ◽  
Block Models ◽  
The Impact ◽  
Block Distribution ◽  
Ordinary Cokriging

AbstractDecisions, from mineral exploration to mining operations, are based on grade block models obtained from samples. This study evaluates the impact of using imprecise data in short-term planning. The exhaustive Walker Lake dataset is used and is considered as the source for obtaining the true grades. Initially, samples are obtained from the exhaustive dataset at regularly spaced grids of 20 × 20 m and 5 × 5 m. A relative error (imprecision) of ±25% and a 10% bias are added to the data spaced at 5 × 5 m (short-term geological data) in different scenarios. To combine these different types of data, two methodologies are investigated: cokriging and ordinary kriging. Both types of data are used to estimate blocks with the two methodologies. The grade tonnage curves and swath plots are used to compare the results against the true block grade distribution. In addition, the block misclassification is evaluated. The results show that standardized ordinary cokriging is a better methodology for imprecise and biased data and produces estimates closer to the true grade block distribution, reducing block misclassification.

Case descriptions for use when training users of the IDEAL schedule

2019 ◽  
pp. 63-76
Author(s):  
Maya Semrau ◽  
Alistair Burns ◽  
Antonio Lobo ◽  
Marcel Olde Rikkert ◽  
Philippe Robert ◽  
...  
Keyword(s):  
Integrated Assessment ◽  
Case Histories ◽  
Local Case ◽  
Different Types ◽  
Severity Levels ◽  
The Ideal

This chapter provides four case histories that can be used in the training of future users of the International Schedule for the Integrated Assessment and Staging of Care for Dementia (IDEAL schedule) and its accompanying ‘Menu of care options’. The case histories describe patients with different types and severity levels of dementia and have been written in a manner that makes them understandable in different settings or countries, as well as having been shown to be useful in the training of users of the schedule in different countries. Ratings for the case histories are provided according to the seven dimensions of the IDEAL schedule, with the consequent links to the ‘Menu of care options’. The chapter also includes suggestions about the development of local case histories typical for the setting in which the schedule will be used when training users in that setting.

SMALL CATAMARANS: DESIGN APPROACHES AND CASE STUDIES

2015 ◽  
Vol 157 (B1) ◽  
Author(s):  
A Nazarov
Keyword(s):  
Structural Design ◽  
Special Interest ◽  
Applied Research ◽  
Comparison Of Methods ◽  
Theoretical Methods ◽  
Seakeeping Performance ◽  
Different Types ◽  
Shape Selection ◽  
Vertical Accelerations ◽  
Design Experience

The paper presents the review of design experience and applied research of catamaran craft, up to 30m in length, of total over 30 catamaran designs, developed by ‘Albatross Marine Design’ and launched during recent years. Architecture of catamarans is discussed; typical catamaran hull shapes are reviewed and their suitability for different applications and desired speeds are studied. Recommendations are given for hull shape particulars selection. Performance issues are studied using available theoretical methods and sea-trials data of number catamarans. Components of resistance of catamarans and methods of their prediction are reviewed. Comparison of methods is presented and samples of their applications for hull shape selection are shown. Seakeeping performance is discussed in terms of vertical accelerations. Results of full-scale measurements of vertical accelerations on number of craft are presented. Controllability discussion is based on turning track measurements for power catamarans of different configurations at different speeds. Structural design issues are reviewed with special interest in composite craft and their improvements. Perspective applications of catamaran concept for different types of craft are indicated. Presented are samples of catamaran designs for special, small commercial and pleasure catamarans.

scholarly journals Determination of Cohesion values of Rock Materials using Double Shear Jaws

2018 ◽  
Author(s):  
Eren Komurlu ◽  
Aysegul Durmus Demir
Keyword(s):  
Failure Mechanisms ◽  
Shear Stresses ◽  
Compressive Test ◽  
Contact Conditions ◽  
Testing Conditions ◽  
Rock Materials ◽  
Double Shear ◽  
Different Types ◽  
Shear Planes

In this study, experimental and numerical analyses were carried out for determination of cohesion values of different types of rock materials using double shear jaws (DSJ) which can be practically used with the conventional compressive test equipment, to make shear planes in the rock core specimens. Effects of various parameters like jaw dimensions, gaps between triple blocks of the DSJ and contact conditions of the jaw on the results and validity of the cohesion test were investigated considering failure mechanisms of rock core specimens. Instead of a failure induced due to the shear stresses, tensile failures are mostly seen from conventional shear testing conditions. For a valid failure under the control of shear stresses, a DSJ design was suggested to be used in cohesion determination tests according to the results obtained from this study.

Dynamic Behavior of Pure Squeeze Films in Narrow Porous Bearings

1974 ◽  
Vol 96 (3) ◽  
pp. 361-364 ◽  
Author(s):  
P. R. K. Murti
Keyword(s):  
Dynamic Behavior ◽  
Cyclic Load ◽  
Journal Bearing ◽  
Load Capacity ◽  
Squeeze Film ◽  
Closed Form Expression ◽  
Cyclic Loads ◽  
Eccentricity Ratio ◽  
Form Expression ◽  
Bearing Material

The dynamic behavior of squeeze film in a narrow porous journal bearing under a cyclic load is analyzed. A thin-walled bearing with a nonrotating journal is considered and a closed form expression for the pressure distribution is derived. The locus of the journal center is found by numerical methods and it is established with an example that actual contact between the journal and bearing can be avoided by appropriate design of the bearing. Consequently, it is proved that pure squeeze films have a load capacity only under cyclic loads. The analysis also reveals that the permeability of the bearing material and the wall thickness of the bearing influence significantly the operating eccentricity ratio.

THE USE OF PLASTICS TO OBVIATE CORROSION

1965 ◽  
Vol 12 (1) ◽  
pp. 24-28
Author(s):  
R.L.H. Damerham
Keyword(s):  
Physical Properties ◽  
Corrosion Protection ◽  
Technical Information ◽  
Case Histories ◽  
New Approach ◽  
Present Practice ◽  
Different Types

This paper will deal with the following topics: 1. A new approach to corrosion technology whereby the use of non‐corrodible materials is studied as against the present practice of largely considering the protection of traditional materials which are subject to corrosion. 2. Types of corrosion for which the use of plastics materials are suitable. 3. The division of plastics into categories differentiated by their resistance to different types of corrosion. 4. The physical properties of importance in considering the use of plastics. 5. The education of (a) The user in the special characteristics of plastics which differ from traditional materials, and (b) Of the supplier to study the needs of the user and to make available to him all the technical information he will require. 6. Case histories in which the use of plastics has been successful where normal anti‐corrosion protection of traditional materials would not have been suitable. 7. Details of services which are available to users and which have been used on installations quoted above, in particular, installation services and prefabricated services. 8. Standards, British, American and International, which are now printed and others which are being worked out to give guidance both to user and manufacturer.

Analysis of creep-induced strains and stresses in notches subjected to a cyclic load

2007 ◽  
Vol 42 (5) ◽  
pp. 361-375 ◽  
Author(s):  
J E Nuñez ◽  
G Glinka
Keyword(s):  
Finite Element ◽  
Plane Stress ◽  
External Load ◽  
Cyclic Load ◽  
Time Dependent ◽  
Cyclic Loads ◽  
Creep Response ◽  
Stress Components ◽  
Estimation Of Time ◽  
Good Agreement

A method for the estimation of time-dependent strains and stresses in notches subjected to a cyclic load is discussed in the paper. The proposed solution is an extension of the methodology proposed previously for notches under a steady external load. A new algorithm is proposed to predict the creep response near notches in plane stress components subjected to cyclic loads. Predictions were compared with finite element data, and good agreement was obtained for various geometrical and material configurations.

Seismic Damage Characteristics of RC Shear Wall with Diagonal Profile Steel Braces by Experiment

2007 ◽  
Vol 340-341 ◽  
pp. 1115-1120
Author(s):  
Shi Yun Xiao ◽  
Hong Nan Li ◽  
Yan Gang Zhao ◽  
Jing Wei Zhang
Keyword(s):  
Mechanical Model ◽  
Shear Walls ◽  
Shear Wall ◽  
Seismic Damage ◽  
Cyclic Loads ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Different Types ◽  
Rc Shear Wall ◽  
Theoretical Results

This paper focuses on an experimental investigation and theoretical analysis of different types of RC shear wall with the profile steel braces in two side columns and diagonal profile steel braces of walls subjected to applied repeated cyclic loads. Fifteen RC shear walls with different shear span ratio are tested and their aseismic charactertics are studied. The effect of profile steel bracings on failure property, bearing capacity, ductility and hysteretical characteristic of shear wall is investigated based on experimental results. It is shown that adding the profile steel braces on the boundary column and inner of walls can obviously enhance the ultimate strength of specimens and improve their aseismic characteristics. Finally, the mechanical model of the shear wall is presented and the formulae for calculating the load-carrying capacity are developed. Numerical analyses indicate that the theoretical results agree well with those from experiments.

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