scholarly journals Design of lattice towers from hot-rolled equal leg steel angles

2021 ◽  
Author(s):  
Μάριος-Ζώης Μπέζας
Keyword(s):  
Steel Angles ◽  
Lattice Towers ◽  
Hot Rolled

Τα προφίλ γωνιακών διατομών χρησιμοποιούνται από τα πρώτα χρόνια των χαλύβδινων κατασκευών λόγω της εύκολης μεταφοράς τους και της επί τόπου συναρμολόγησής τους. Ωστόσο, παρουσιάζουν συγκεκριμένα χαρακτηριστικά που τα διαφοροποιούν από τους άλλους τύπους κοινών διατομών, γεγονός που οδηγεί αναπόφευκτα στην ανάγκη ανάπτυξης ειδικών κανόνων σχεδιασμού. Σε πρώτη φάση ελέγχθηκαν και αξιολογήθηκαν οι υφιστάμενες ευρωπαϊκές διατάξεις για τα ισοσκελή γωνιακά θερμής έλασης, και στη συνέχεια, διεξήχθησαν εκτεταμένες πειραματικές, αναλυτικές και αριθμητικές μελέτες ώστε να προταθεί ένα ολοκληρωμένο και πλήρως επικυρωμένο σύνολο κανόνων σχεδιασμού που να καλύπτει όλες τις πτυχές του σχεδιασμού των γωνιακών. Οι κανόνες αυτοί περιλαμβάνουν την ταξινόμηση της διατομής, την αντοχή της διατομής για όλους τους τύπους φόρτισης, καθώς και κανόνες για το σχεδιασμό μελών υπό μεμονωμένες ή και συνδυασμένες εσωτερικές αξονικές δυνάμεις και ροπές. Όλοι οι προτεινόμενοι κανόνες είναι γραμμένοι υπό την μορφή των διατάξεων του Ευρωκώδικα 3, ώστε να είναι δυνατή η άμεση ενσωμάτωσή τους στην επερχόμενη έκδοση. Επιπλέον, τα γωνιακά προφίλ χρησιμοποιούνται ευρέως σε δικτυωτούς πύργους και ιστούς για τηλεπικοινωνιακούς σκοπούς ή για τη μεταφορά ηλεκτρικής ενέργειας. Τέτοιοι τύποι πύργων σχεδιάζονται κυρίως σύμφωνα με τα πρότυπα EN 1993-3-1 και EN 50341-1, βάσει μιας γραμμικής ελαστικής ανάλυσης πρώτης τάξεως όπου η κατασκευή προσομοιώνεται ως ένα δικτύωμα. Στην παρούσα εργασία πραγματοποιείται αξιολόγηση της τρέχουσας προσέγγισης σχεδιασμού, όπου ο πύργος προσομοιώνεται με ένα λογισμικό μη γραμμικών πεπερασμένων στοιχείων, λαμβάνοντας υπόψη τις αρχικές ατέλειες στην κατασκευή καθώς και τις μη γραμμικότητες του υλικού και της γεωμετρίας. Υπογραμμίζεται η σημασία των φαινομένων δευτέρας τάξεως στην ανάλυση, ενώ επισημαίνεται η ύπαρξη μιας μορφής αστάθειας που δεν καλύπτεται άμεσα από τους κανονισμούς και ως εκ τούτου, συνήθως δεν ελέγχεται. Στην συνέχεια, δύο αναλυτικά μοντέλα για την πρόβλεψη του κρίσιμου φορτίου του νέου τρόπου λυγισμού προτείνονται και επικυρώνονται αριθμητικά. Και τα δύο προτεινόμενα μοντέλα είναι εύκολα στην εφαρμογή τους και μπορούν να καλύψουν το κενό στις υπάρχουσες συστάσεις σχεδιασμού για δικτυωτούς πύργους.

scholarly journals End Restraints in Steel Angles in Lattice Towers

2017 ◽  
Vol 11 (1) ◽  
pp. 738-747
Author(s):  
Sriram Kalaga
Keyword(s):  
Test Data ◽  
Effective Length ◽  
Compression Members ◽  
Adjustment Factors ◽  
Lattice Tower ◽  
Steel Angles ◽  
Lattice Towers ◽  
Connection Length

Introduction: Test data on single angle compression members with various end connection arrangements is used to develop adjustment factors for effective buckling lengths. A connection length parameter is proposed and evaluated based on test data. Results from a total of 31 equal leg test angles with single-, double- bolts and fixed ends are used. Methods: Slenderness ratios considered ranged from 150 to 312. Angle sizes ranged from 38 x 38 x 3.2 (mm) to 89 x 89 x 6.4 (mm). Estimated connection lengths were about 12.5% of the member length for single-bolt joints; 24.7% for double-bolt joints and 45.6% for fixed joints. Computed effective length factors ranged from 0.544 to 0.875. Results: Results seem to indicate that it is possible to define and calculate connection length of a lattice tower angle member. Suggestions for incorporating connection length issues in routine designs are made.

Design of 60° equal-leg steel angles according to CSA Standard S37-94

1995 ◽  
Vol 22 (3) ◽  
pp. 603-610
Author(s):  
Murty K. S. Madugula ◽  
Seshu Madhava Rao Adluri
Keyword(s):  
Experimental Studies ◽  
Local Buckling ◽  
Design Procedure ◽  
Technical Committee ◽  
Design Strength ◽  
Widespread Application ◽  
Flexural Buckling ◽  
Steel Angles ◽  
Lattice Towers ◽  
First Time

Sixty-degree equal-leg steel angles find widespread application as leg members of triangular-base lattice towers. Compared to 90° angles of the same size, these angles are weaker in torsional-flexural buckling. The design of such angles is being explicitly covered for the first time in CSA Standard S37-94, "Antennas, towers and antenna-supporting structures." Recent experimental studies have shown that the design of 60° angles will be quite safe, if design is carried out using the expressions for factored axial compressive resistances given in CAN/CSA-S16.1-M89, taking into account only the effect of local buckling and flexural buckling about minor axis, and neglecting torsional-flexural buckling. The Canadian Standards Association Technical Committee on Antenna Towers also noted that the calculated resistances will still be less than the strengths according to the widely used Standard ANSI/ASCE 10-90, "Design of latticed steel transmission structures," which considers all the three modes of buckling. The present paper explains the rationale behind the design procedure adopted by the Technical Committee. Key words: angles, buckling, compression, design strength, schifflerized angles, specifications, steel towers, 60° angles.

Torsional – flexural buckling strength of steel angles

1996 ◽  
Vol 23 (1) ◽  
pp. 260-271 ◽  
Author(s):  
Seshu M. R. Adluri ◽  
Murty K. S. Madugula
Keyword(s):  
Local Buckling ◽  
Rolled Steel ◽  
Design Strength ◽  
Flexural Buckling ◽  
Plate Buckling ◽  
Steel Members ◽  
Steel Angles ◽  
Hot Rolled ◽  
Hot Rolled Steel ◽  
Steel Design

Although structural steel angles have a wide variety of applications, they have not received attention comparable to that given to heavy shapes such as wide-flange sections. Because steel angles are singly symmetric or asymmetric, torsional-flexural buckling is an important mode of failure. The Canadian steel design practice for hot-rolled steel members (as given by CAN/CSA-S16.1-94) does not give a detailed procedure applicable to all sizes of steel angles. Some of the world codes applicable for steel angles specify torsional–flexural buckling check and plate buckling check to be considered simultaneously wherever applicable. The paper presents the results of an experimental investigation consisting of 34 hot-rolled steel angles under concentric compression (slenderness ratios between 50 and 150) failing in torsional?flexural buckling. The width to thickness ratios of test specimens ranged from 13 to 20. The results give a continuous spread of compressive strengths for practical ranges of slenderness parameters. The results show that torsional–flexural buckling and plate buckling need not be considered simultaneously even for unequal angles if they are designed according to CAN/CSA-S16.1-94. Key words: angle, buckling, codes and standards, compression, design strength, flexural buckling, local buckling, specifications, steel, torsional–flexural buckling.

FLEXURAL AND LOCAL BUCKLING INTERACTION OF STEEL ANGLES

2005 ◽  
Vol 05 (02) ◽  
pp. 143-162 ◽  
Author(s):  
S. J. MOHAN ◽  
N. PRASAD RAO ◽  
N. LAKSHMANAN
Keyword(s):  
Local Buckling ◽  
Research Station ◽  
Column Buckling ◽  
Inelastic Buckling ◽  
The Past ◽  
Plate Buckling ◽  
Transmission Towers ◽  
Experimental Works ◽  
Steel Angles ◽  
Hot Rolled

The column buckling equation and plate buckling equation are merged to obtain a graphical relation in the elastic and inelastic buckling ranges. This graphical relation has been used to classify all possible modes of hot rolled angle sections investigated by previous researchers in their experimental works. Forced plate buckling experiments have been carried out to verify the graphical relation for plate buckling. Design practices adopted by various standards for design of steel angles, have been compared with respect to this graphical relation and discussed. The importance of width to thickness ratio has been used to emphasize the buckling characteristics of hot rolled angle sections. The objective of this paper is to discuss the plate buckling failures of the angle sections recorded during full scale testing of transmission towers at Tower Testing and Research Station, SERC, Chennai, India. The plate buckling failures in tower testing for the past eighteen years have been analyzed and suggestions are given to avoid such failures in real structures and during testing.

Observations on the structure at the transformation interface of pearlite in steel

1990 ◽  
Vol 48 (4) ◽  
pp. 200-201
Author(s):  
F. A. Khalid ◽  
D. V. Edmonds
Keyword(s):  
Room Temperature ◽  
Thin Foil ◽  
Carbon Steels ◽  
Model Alloy ◽  
Growth Interface ◽  
Medium Carbon ◽  
Solution Treated ◽  
Medium Carbon Steels ◽  
Alloy Carbide ◽  
Hot Rolled

The austenite/pearlite growth interface in a model alloy steel (Fe-1 lMn-0.8C nominal wt%) is being investigated. In this particular alloy pearlite nodules can be grown isothermally in austenite that remains stable at room temperature, thus facilitating examination of the transformation interfaces. This study presents preliminary results of thin foil TEM of the austenite/pearlite interface, as part of a programme of aimed at studying alloy carbide precipitation reactions at this interface which can result in significant strengthening of microalloyed low- and medium- carbon steels L Similar studies of interface structure, made on a partially decomposed high- Mn austenitic alloy, have been reported recently.The experimental alloys were made as 50 g argon arc melts using high purity materials and homogenised. Samples were hot- rolled, swaged and machined to 3mm diameter rod, solution treated at 1300 °C for 1 hr and WQ. Specimens were then solutionised between 1250 °C and 1000 °C and isothermally transformed between 610 °C and 550 °C for 10-18 hr and WQ.

Development of trimming technology for hot rolled ultra-low carbon steel

1993 ◽  
Vol 90 (7-8) ◽  
pp. 917-922
Author(s):  
Y. Matsuda ◽  
M. Nishino ◽  
J. Ikeda
Keyword(s):  
Carbon Steel ◽  
Low Carbon Steel ◽  
Low Carbon ◽  
Ultra Low Carbon Steel ◽  
Hot Rolled

Investigation on the control of multiphase flow behavior in a continuous casting tundish during ladle change

2020 ◽  
Vol 117 (6) ◽  
pp. 619
Author(s):  
Rui Xu ◽  
Haitao Ling ◽  
Haijun Wang ◽  
Lizhong Chang ◽  
Shengtao Qiu
Keyword(s):  
Multiphase Flow ◽  
Flow Behavior ◽  
Rolled Strip ◽  
Impact Zone ◽  
Steel Cleanliness ◽  
Carry Over ◽  
Slag Carry Over ◽  
Hot Rolled ◽  
Turbulence Inhibitor ◽  
The Impact

The transient multiphase flow behavior in a single-strand tundish during ladle change was studied using physical modeling. The water and silicon oil were employed to simulate the liquid steel and slag. The effect of the turbulence inhibitor on the slag entrainment and the steel exposure during ladle change were evaluated and discussed. The effect of the slag carry-over on the water-oil-air flow was also analyzed. For the original tundish, the top oil phase in the impact zone was continuously dragged into the tundish bath and opened during ladle change, forming an emulsification phenomenon. By decreasing the liquid velocities in the upper part of the impact zone, the turbulence inhibitor decreased considerably the amount of entrained slag and the steel exposure during ladle change, thereby eliminating the emulsification phenomenon. Furthermore, the use of the TI-2 effectively lowered the effect of the slag carry-over on the steel cleanliness by controlling the movement of slag droplets. The results from industrial trials indicated that the application of the TI-2 reduced considerably the number of linear inclusions caused by ladle change in hot-rolled strip coils.

Hot-rolled strip re-reddening temperature changing law for late ultra fast-cooling in a CSP line

2015 ◽  
Vol 112 (3) ◽  
pp. 305 ◽  
Author(s):  
Lian-yun Jiang ◽  
Guo Yuan ◽  
Jian-hui Shi ◽  
Yue Xue ◽  
Di Wu ◽  
...  
Keyword(s):  
Rolled Strip ◽  
Hot Rolled Strip ◽  
Ultra Fast Cooling ◽  
Fast Cooling ◽  
Hot Rolled

Influence of Yield Strength Variability over Cross-Section to Steel Beam Load-Carrying Capacity

2005 ◽  
Vol 10 (2) ◽  
pp. 151-160 ◽  
Author(s):  
J. Kala ◽  
Z. Kala
Keyword(s):  
Yield Strength ◽  
Cross Section ◽  
Carrying Capacity ◽  
Bending Moment ◽  
Statistical Characteristics ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Strength Variability ◽  
Hot Rolled ◽  
Hot Rolled Steel

Authors of article analysed influence of variability of yield strength over cross-section of hot rolled steel member to its load-carrying capacity. In calculation models, the yield strength is usually taken as constant. But yield strength of a steel hot-rolled beam is generally a random quantity. Not only the whole beam but also its parts have slightly different material characteristics. According to the results of more accurate measurements, the statistical characteristics of the material taken from various cross-section points (e.g. from a web and a flange) are, however, more or less different. This variation is described by one dimensional random field. The load-carrying capacity of the beam IPE300 under bending moment at its ends with the lateral buckling influence included is analysed, nondimensional slenderness according to EC3 is λ¯ = 0.6. For this relatively low slender beam the influence of the yield strength on the load-carrying capacity is large. Also the influence of all the other imperfections as accurately as possible, the load-carrying capacity was determined by geometrically and materially nonlinear solution of very accurate FEM model by the ANSYS programme.

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