scholarly journals Limit states design of antenna towers

1994 ◽  
Vol 21 (6) ◽  
pp. 913-923 ◽  
Author(s):  
Yohanna M. F. Wahba ◽  
Murty K. S. Madugula ◽  
Gerard R. Monforton
Keyword(s):  
Direct Interaction ◽  
Steel Structures ◽  
Ice Accretion ◽  
Structural Behaviour ◽  
Limit States ◽  
Working Stress ◽  
Load Factors ◽  
Partial Load ◽  
Wind Pressures ◽  
Supporting Structures

The Canadian Standard CAN/CSA-S37-M86 “Antennas, towers and antenna supporting structures” follows a quasi-limit states approach in which the member forces determined for specified loads are multiplied by a unified factor and compared with factored resistances given in CAN3-S16.1-M84. This results in designs basically the same as those resulting from a working stress design with a factor of safety of 5/3. Such structures exhibit a non-linear structural behaviour even under service loads. Thus the effect of ice accretion and direct interaction between wind and ice does not permit the load factors specified in CAN/CSA-S16.1-M89 “Limit states design of steel structures” to be directly applied to antenna supporting structures.In this study, 41 different towers (representing various heights and designed for different ice classes and wind pressures) were analyzed under specified loads and then under a set of factored loads. From the comparison of the design forces in the towers with those calculated according to the existing standard, a set of partial load factors was derived. The new load factors to be used in the 1993 edition of S37 are presented and justified. Key words: antenna towers, guyed towers, ice and wind loads, limit states design, self-supporting towers, working stress design.

Eighteenth Canadian Geotechnical Colloquium: Limit States Design For Foundations. Part I. An overview of the foundation design process

1996 ◽  
Vol 33 (6) ◽  
pp. 956-983 ◽  
Author(s):  
Dennis E Becker
Keyword(s):  
Design Process ◽  
Theoretical Models ◽  
Mean Value ◽  
Limit States ◽  
Foundation Design ◽  
The North ◽  
Working Stress ◽  
Characteristic Value ◽  
Partial Load ◽  
Resistance Approach

This paper examines the foundation design process in terms of level of safety associated with current state-of-practice, sources of uncertainty and how they are handled, importance of engineering judgement and experience, and the role of codes of practice. Working stress, limit states, reliability-based design approcahes are described and discussed in terms of their historical development, fundamental bases and differences, advantages, and limitations. Limit states are conditions under which a structure no longer performs its intended function. Limit states design considers seperately the two classes of ultimate and serviceability limit states using partial factors of safety. The European factored strength approach and the North American factored overall resistance approach are compared and discussed. The factored resistance approach is a logical extension of working stress design and has the significant advantage that it reflects not only uncertainty in strength, but also in theoretical models, site conditions, construction tolerances, and failure mechanisms. The partial load and resistance factors are interrelated and are a function of characteristic values. A consistent, rational basis for the selection of the geotechnical characteristic value is required. The use of a conservatively assessed mean value is recommended, and an approach for its interpretation is presented. Key words: limit states design, working stress design, characteristic value, partial factors, factored resistance, load and resistance factor design.

The Method Research for Appraisal of Reliability of Existing Lightweight Steel Structures

2014 ◽  
Vol 578-579 ◽  
pp. 1562-1566
Author(s):  
Zhong Yang Liu ◽  
Wei Chen ◽  
Li Jun Zhang
Keyword(s):  
Structural Analysis ◽  
Steel Structures ◽  
Conversion Factors ◽  
Lightweight Steel ◽  
Load Factors ◽  
Partial Load

Combined with the characteristics of existing lightweight steel structures, the paper gives an adapted method and flowchart for appraisal of reliability of these structures, and explains objectives appraisal of existing lightweight steel structures. It indicates that assessment based on structural analysis is the available method for scientific and saving, according to the demond of market and owner. It also discussed the central technique and the main problems of appraisal in current, such as revision of partial load factors, consideration of conversion factors, etc.

Limit States Design—An Innovation in Design Standards for Steel Structures

1974 ◽  
Vol 1 (1) ◽  
pp. 1-13 ◽  
Author(s):  
D. J. Laurie Kennedy
Keyword(s):  
Design Method ◽  
Steel Structures ◽  
Probability Of Failure ◽  
Simple Design ◽  
Design Standards ◽  
Limit States ◽  
Working Stress ◽  
Wide Range ◽  
Ultimate Resistance ◽  
Two Sides

The greater rationality of limit states design as compared to working stress design is developed to show that limit states design leads to a more consistent probability of failure and that neither overly safe and therefore uneconomic structures nor structures with insufficient safety should result from this design methodology.This rationality is extended in the limit states design method in that the performance of the structure and its components is checked against the various limit states at the appropriate load levels. Thus the limit states of serviceability are checked at specified load levels and of strength and stability at the factored load levels.Functions are presented for the two sides of the inequality:[Formula: see text]A comparative design of a 20-storey structure selected to provide a wide range of variables shows that limit states design as proposed results in a structure comparable to that designed by working stress method with a moderate saving in the weight of steel. Some simple design examples are worked out to show the basic similarities between working stress design and limit states design and that the two methods are of about equal complexity or simplicity. It is believed, because the designer will have to check the ultimate resistance against the effect of the factored loads, that he will develop a greater awareness of the behavior of the material and members with which he is working.

scholarly journals Some Comments on Designing of Steel Structures According to European Standards

2019 ◽  
Vol 18 (2) ◽  
pp. 113-120
Author(s):  
Y. Y. Davydov
Keyword(s):  
Steel Structures ◽  
Load Combination ◽  
Load Factors ◽  
Partial Load ◽  
Calculated Load ◽  
Similar Materials ◽  
Technical Specifications ◽  
The Republic ◽  
European Standards ◽  
Materials Used

Critical comments on the European standards for designing steel structures including welded and bolted joints have been given on the basis of application experience and executed analysis. Comments are presented in comparison with similar regulatory documents which are in effect in Belarus. European standards concerning loads (determination of calculated load values and drawing up of design load combination) have been also analyzed. Particular attention has been paid to the analysis of European standard requirements to steel and welding materials and their comparison with mechanical characteristics of similar materials used for manufacture of steel structures in Belarus. The paper gives notice to the rules which are accepted in the European norms and the rules being compared with the similar rules used in Construction rules and regulations (SNiP) lead to a significant increase in material consumption of steel structures. First of all, it concerns assignment of partial load factors and classification of sections for ensuring local stability of compressed and partially compressed elements. The paper pays a special notice to the rules of Eurocodes that do not meet requirements of State standards and technical specifications operating in the Republic of Belarus. Significant limitations of some European rules regarding calculation of centrally and eccentrically compressed elements, absence of rules for testing overall stability of through and step columns which are widely used while implementing projects Belarus have been described in the paper. Conclusions have been made on the basis of the analysis results and according to them application of European standards for designing steel structures has significant limitations on the territory of the Republic of Belarus.

Anchor rod forces and maximum bending moments in sheet pile walls using the factored strength approach

1996 ◽  
Vol 33 (5) ◽  
pp. 815-821 ◽  
Author(s):  
A B Schriver ◽  
A J Valsangkar
Keyword(s):  
Water Pressure ◽  
Limit State ◽  
Bending Moment ◽  
Ultimate Limit State ◽  
Sheet Pile ◽  
Limit States ◽  
Working Stress ◽  
Geotechnical Design ◽  
Ultimate Limit State Design ◽  
Sheet Pile Wall

Recently, the limit states approach using factored strength has been recommended in geotechnical design. Some recent research has indicated that the application of limit states design using recommended load and strength factors leads to conservative designs compared with the conventional methods. In this study the influence of sheet pile wall geometry, type of water pressure distribution, and different methods of analysis on the maximum bending moment and achor rod force are presented. Recommendations are made to make the factored strength design compatible with conventional design. Key words: factored strength, working stress design, ultimate limit state design, anchored sheet pile wall, bending moment, anchor rod force.

scholarly journals Partial factors for cross-section resistance of elements in steel structures

2013 ◽  
Vol 12 (2) ◽  
pp. 213-220
Author(s):  
Marian Giżejowski ◽  
Zbigniew Stachura
Keyword(s):  
Cross Section ◽  
Steel Structures ◽  
Partial Cross Section ◽  
Live Load ◽  
Practical Application ◽  
Limit States ◽  
Resistance Factors ◽  
Safety Requirements ◽  
Permanent Load ◽  
Load Component

Issues related to safety requirements for steel elements subjected to different stress resultants in reference to limit states design philosophy according to Structural Eurocodes PN-EN and national codes PN-B are dealt with in the paper. The calibration of partial cross-section resistance factors is discussed on the basis of elements of steel floor structures where the permanent load component and the live load component of variable actions are the only components of load combinations. Final conclusions for their practical application in the codification process are formulated and values of partial factors for cross section resistance are proposed.

scholarly journals Calibrating Partial Factors – Methodology, Input Data and Case Study of Steel Structures

2019 ◽  
Author(s):  
Vitali Nadolski ◽  
Árpád Rózsás ◽  
Miroslav Sýkora
Keyword(s):  
Input Data ◽  
Structural Reliability ◽  
Construction Materials ◽  
Steel Structures ◽  
Structural Performance ◽  
Limit States ◽  
Different Types ◽  
Load Effects ◽  
Previous Design

Partial factors are commonly based on expert judgements and on calibration to previous design formats. This inevitably results in unbalanced structural reliability for different types of construction materials, loads and limit states. Probabilistic calibration makes it possible to account for plentiful requirements on structural performance, environmental conditions, production and execution quality etc. In the light of ongoing revisions of Eurocodes and the development of National Annexes, the study overviews the methodology of probabilistic calibration, provides input data for models of basic variables and illustrates the application by a case study. It appears that the partial factors recommended in the current standards provide for a lower reliability level than that indicated in EN 1990. Different values should be considered for the partial factors for imposed, wind and snow loads, appreciating the distinct nature of uncertainties in their load effects.

Allowable Load Derivation of Single Angle Members for Small Bore Pipe Supports Welded on 4-Bolt CEA Plate in APR1400

2008 ◽  
Author(s):  
Joon-Ho Lee ◽  
Hee-Cheon Choo ◽  
Jae-Hwan Bae
Keyword(s):  
Finite Element ◽  
Nuclear Power ◽  
Steel Structures ◽  
Integrated Analysis ◽  
Piping System ◽  
Finite Element Models ◽  
Support Design ◽  
Anchor System ◽  
Consensus Standard ◽  
Supporting Structures

Single angle members have been rarely used as supporting structures in nuclear power plant because they are open sections which have significantly reduced capacities when considered in comparison to closed sections, and have weakness for twisting load such as local torsion caused by loading eccentricity of geometric center and shear center. However, in APR1400 (Advanced Power Reactor 1400 MW-class in Korea), the extended application of single angle members for supporting structures of small bore piping systems is considered to enhance the constructability and economics of plant. Furthermore, although it is general guideline for support design in APR1400 that supporting structures for equipment should be directly welded to embedded plates or steel structures in buildings as far as possible, in the case of small bore piping system, for the low level priority of construction in site, supporting steel structures for small bore piping could not be evitable to be welded onto the CEA (Concrete Expansion Anchor) plate. Per the ACI 318, ACI 349 and ACI 355.2, most CEA plate designs and anchor bolt load determinations are now based on finite element models that many applications have been individually made for CEA plates. If single angle members are attached onto these plates, integrated finite element models should be developed and analyzed in detail accroding to NRC IEB 79-02. Such a detailed analysis may appear to be excessive to small bore pipe supports which have diverse design materials and frequently subjected to field changes requiring rapid revision. Consideration should be given to reviewing current practices and reducing the level of effort being used for the integrated analysis of support and CEA plate by developing consensus standard regarding reasonable support and CEA plate designs. In this paper, allowable piping loads for single angle members such as L2×2×1/4, L2-1/2×2-1/2×1/4, L3×3×3/8, and L4×4×1/2 welded on the 4-bolt CEA assembly are derived and reviewed for general use for small bore pipe support design, and L2-1/2×2-1/2×1/4 and L3×3×3/8 welded onto 4-bolt (3/8″Φ sleeve type) CEA plate (1/2″×9″×9″) are recommended as standard small bore pipe supports with post-installed anchor system in APR1400.

Seismic retrofit of structures using rotational friction dampers with restoring force

2020 ◽  
Vol 23 (16) ◽  
pp. 3525-3540
Author(s):  
Asad Naeem ◽  
Jinkoo Kim
Keyword(s):  
Ground Motions ◽  
Design Procedure ◽  
Steel Structures ◽  
Friction Damper ◽  
Heavy Duty ◽  
Limit States ◽  
Restoring Force ◽  
Friction Dampers ◽  
Torsional Spring ◽  
Capacity Spectrum

In this study, the seismic performance of a rotational friction damper with restoring force is presented. The torsional spring friction damper consists of rotational friction pads with the heavy duty torsional springs attached on both sides of the friction damper. An analytical model and a design procedure for the damper are developed using capacity spectrum method. A parametric study is carried out to investigate the influence of the torsional spring in the response of the structure when subjected to ground motions. The seismic performances of steel structures retrofitted with the torsional spring friction damper and conventional rotational friction dampers are evaluated using fragility analysis, which shows that the structure retrofitted with the torsional spring friction damper has the smallest probability of reaching the specific limit states.

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