scholarly journals Estados limites determinantes no dimensionamento da armadura longitudinal de vigas pós-tracionadas sem aderência

2020 ◽  
Vol 1 (51) ◽  
pp. 226
Author(s):  
João Paulo Boff Almeida ◽  
Renato Silva Nicoletti ◽  
Anderson Renato Vobornik Wolenski ◽  
Rafael Lemes Bezerra ◽  
Alex Sander Clemente de Souza ◽  
...  
Keyword(s):  
Prestressed Concrete ◽  
Limit State ◽  
Ultimate Limit State ◽  
Longitudinal Reinforcement ◽  
Structural Elements ◽  
Limit States ◽  
The Common ◽  
Lower Height ◽  
Ultimate Limit ◽  
Range Of Values

<p>In the design of prestressed concrete structural elements, due to the fact that prestressing introduces actions in the structure, the limit states of crack formation service (SLS-F), decompression (SLS-D), and the ultimate limit state in the act of prestressing (ULS-ACT) are determinants in the dimensioning of the longitudinal reinforcement (Ap). In most cases, the longitudinal reinforcement required for the limit states is not exact, and the solution, if any, is within a range of values defined by the voltage limits of the SLS-F, SLS-D, and ULSACT. In this context, this paper aimed to verify, analytically, the limit states, service or ultimate, determinants in the calculation of Ap of unbonded post-tensioned beams. For this purpose, beams with material properties, environmental conditions, the width of the cross-section, and identical loads (except for their own weight) were analyzed, varying the height between 50 and 70 cm. It was found that the limits of tensile stress in the SLS-D and compression in the ULS-ACT for the lower edge, defined the intervals that were requested, simultaneously, by SLS-F, SLS-D, and ULS-ACT. For beams of lower height, the common range of solutions became more restricted and the ULS became decisive in the dimensioning of the longitudinal reinforcement, which did not occur for the higher beams.</p>

Seismic Test Methods for Architectural Glazing Systems

1996 ◽  
Vol 12 (1) ◽  
pp. 129-143 ◽  
Author(s):  
Richard A. Behr ◽  
Abdeldjelil Belarbi
Keyword(s):  
Rational Design ◽  
Limit State ◽  
Test Methods ◽  
Test Method ◽  
Ultimate Limit State ◽  
Limit States ◽  
State Data ◽  
Design Procedures ◽  
Seismic Loadings ◽  
Ultimate Limit

An ongoing effort is being made at the University of Missouri-Rolla to develop standard laboratory test methods and codified design procedures for architectural glass under seismic loadings. Recent laboratory work has yielded some promising results regarding the development of an appropriate seismic test method for architectural glass, as well as identifying ultimate limit states that quantify the seismic performance and damage thresholds of various glass types. Specifically, a straightforward “crescendo-like” in-plane dynamic racking test, performed at a constant frequency, has been employed successfully. Two ultimate limit states for architectural glass have been defined: (1) a lower ultimate limit state corresponding to major glass crack pattern formation; and (2) an upper limit state corresponding to significant glass fallout. Early crescendo tests have yielded distinct and repeatable ultimate limit state data for various storefront glass types tested under dynamic racking motions. Crescendo tests will also be used to identify and quantify serviceability limit states for architectural glass and associated glazing components under dynamic loadings. These limit state data will support the development of rational design procedures for architectural glass under seismic loadings.

An Automated Approach for Designing Monopiles Subjected to Lateral Loads

2017 ◽  
Author(s):  
James P. Doherty ◽  
Barry M. Lehane
Keyword(s):  
Limit State ◽  
Ultimate Limit State ◽  
Lateral Loads ◽  
Limit States ◽  
Laterally Loaded Piles ◽  
Improve Design ◽  
Design Procedures ◽  
Automated Algorithm ◽  
Laterally Loaded ◽  
Ultimate Limit

This paper describes an automated algorithm for determining the length and diameter of monopile foundations subject to lateral loads with the aim of minimising the pile weight, whilst satisfying both ultimate and serviceability limit states. The algorithm works by wrapping an optimisation routine around a finite element p - y model for laterally loaded piles. The objective function is expressed as a function representing the pile volume, while the ultimate limit state and serviceability limit states are expressed as optimisation constraints. The approach was found to be accurate and near instantaneous when compared to manual design procedures and may improve design outcomes and reduce design time and costs.

scholarly journals Secondary Moments due to Prestressing with Different Bond at the Ultimate Limit State

2018 ◽  
Vol 26 (1) ◽  
pp. 10-18
Author(s):  
Jaroslav Halvoník ◽  
Peter Pažma ◽  
Radoslav Vida
Keyword(s):  
Limit State ◽  
Plastic Hinge ◽  
Ultimate Limit State ◽  
Critical Cross Section ◽  
Structural System ◽  
Secondary Effects ◽  
Limit States ◽  
Internal Forces ◽  
Ultimate Limit ◽  
Kinematic Mechanism

Abstract Secondary effects of prestressing develop in statically indeterminate structures (e.g., continuous beams) due to the restraint of deformations imposed by hyperstatic restraints. These effects may significantly influence internal forces and stresses in prestressed structures. Secondary effects are influenced by the redundancy of a structural system, which raises the question of whether they will remain constant after a change in the structural system, e.g., due to the development of plastic hinge(s) in a critical cross-section(s) or after the development of a kinematic mechanism, or if they will disappear when the structure changes into a sequence of simply supported beams. The paper deals with an investigation of the behavior of continuous post-tensioned beams subjected to an ultimate load with significant secondary effects from prestressing. A total of 6 two-span beams prestressed by tendons with different bonds were tested in a laboratory with a load that changed their structural system into a kinematic mechanism. The internal forces and secondary effects of the prestressing were controlled through measurements of the reactions in all the supports. The results revealed that the secondary effects remained as a permanent part of the action on the experimental beams, even after the development of the kinematic mechanism. The results obtained confirmed that secondary effects should be included in all combinations of actions for verifications of ultimate limit states (ULS).

scholarly journals A Structural Analysis Of A Factory Hall With A Two-Story Office Building As A Precast And Prestressed Concrete Construction

2021 ◽  
Author(s):  
Olesja Befus
Keyword(s):  
Structural Analysis ◽  
Prestressed Concrete ◽  
Limit State ◽  
Steel Structure ◽  
Ultimate Limit State ◽  
Limit State Design ◽  
European Standards ◽  
Ultimate Limit State Design ◽  
Manual Calculation ◽  
Ultimate Limit

The objective of this thesis is to develop a precast and prestressed concrete design for a factory hall, which was initially planned as a steel structure. Furthermore, a structural analysis is conducted on several chosen structural elements according to the European Standards and the German Annexes respectively. The analysis is done both by manual calculation and software calculation for comparison and includes the ultimate limit state design, the serviceability limit state design and the design for the state of transportation and assembly of the precast members. Lastly, to illustrate the results of the analysis, an overview drawing with the new concrete design as well as formwork and reinforcement drawings for each of the analyzed structural members are developed.

DESIGN OF BOLTED CONNECTIONS SUBJECT TO TORSION AND SHEAR IN THE ULTIMATE LIMIT STRESS STATE

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mohamed S. Abu-Yosef ◽  
Ezzeldin Y. Sayed-Ahmed ◽  
Emam A. Soliman
Keyword(s):  
Failure Modes ◽  
Focal Point ◽  
Design Method ◽  
Limit State ◽  
Bending Moment ◽  
Steel Structures ◽  
Ultimate Limit State ◽  
Shear Forces ◽  
Limit States ◽  
Ultimate Limit

Steel connections transferring axial and shear forces in addition to bending moment and/or torsional moment are widely used in steel structures. Thus, design of such eccentric connections has become the focal point of any researches. Nonetheless, behavior of eccentric connections subjected to shear forces and torsion in the ultimate limit state is still ambiguous. Most design codes of practice still conservatively use the common elastic analysis for design of the said connections even in the ultimate limit states. Yet, there are some exceptions such as the design method proposed by CAN/CSA-S16-14 which gives tabulated design aid for the ultimate limit state design of these connections based on an empirical equation that is derived for ¾ inch diameter A325 bearing type bolts and A36 steel plates. It was argued that results can also be used with a margin of error for other grade bolts of different sizes and steel of other grades. As such, in this paper, the performance of bolted connection subject to shear and torsion is experimentally investigated. The behavior, failure modes and factors affecting both are scrutinized. Twelve connections subject to shear and torsion with different bolts configurations and diameters are experimentally tested to failure. The accuracy of the currently available design equations proposed is compared to the outcomes of these tests.

Analysis of the Superstructure of South-to-North Water Diversion Bridge

2012 ◽  
Vol 178-181 ◽  
pp. 2125-2130
Author(s):  
Ming Hong Li ◽  
Yi Li Wang ◽  
Shui Wan
Keyword(s):  
Prestressed Concrete ◽  
Limit State ◽  
Vertical Shear ◽  
Water Diversion ◽  
Ultimate Limit State ◽  
North Water ◽  
Corrugated Steel Web ◽  
Girder Bridge ◽  
Standard Limit ◽  
Ultimate Limit

Based on the South-to-North Water Diversion Bridge (70m+120m+70m prestressed concrete composite box-girder bridge with corrugated steel webs), structural static analysis of the bridge’s superstructure was taken out by finite element method, which were checked with the existing regulatory requirements. The result indicates that the carrying capacity in the ultimate limit state meet the requirement of the standard, the vertical shear stress of corrugated steel web satisfies the standard limit and the thickness of corrugated steel web satisfies the request, but the safety factor is not high.

scholarly journals Automation of the evaluation of bonded and unbonded prestressed concrete beams, according to brazilian and french code specifications

2013 ◽  
Vol 6 (1) ◽  
pp. 13-54
Author(s):  
P. M. Lazzari ◽  
A. Campos Filho ◽  
F. P. S. L. Gastal ◽  
R. A. Barbieri ◽  
R. C. Schwingel
Keyword(s):  
Prestressed Concrete ◽  
Geometric Nonlinearity ◽  
Computational Algorithm ◽  
Concrete Beams ◽  
Limit State ◽  
Ultimate Limit State ◽  
Flexural Members ◽  
Design Procedures ◽  
Planar Frames ◽  
Ultimate Limit

This paper presents a suggestion for the automation of the design procedures of bonded and unbonded prestressed concrete flexural members, according to the Brazilian (NBR 6118:2007) and French (Règles BPEL 91) norm specifications. Prestressing of concrete structures has been increasingly used, mainly due to its building advantages, as well as allowing reducing crack incidence and element dimensions by the use of more resistant materials. Structure is analyzed by a numerical model that employs a hybrid type finite element for planar frames, considering geometric nonlinearity, cyclic loading and composite construction. The computational algorithm implemented considers full, partial and limited prestressing situations, evaluating in each case decompression limit state, limit state of cracking, ultimate limit state and final prestressing state. Finally, two examples comparing design situations according to the Brazilian and French norms are presented.

Rehabilitation criteria for post-tensioned voided-slab bridges

2004 ◽  
Vol 31 (6) ◽  
pp. 977-987 ◽  
Author(s):  
C R Scollard ◽  
F M Bartlett
Keyword(s):  
Limit State ◽  
Ultimate Limit State ◽  
Limit States ◽  
Stress Cracking ◽  
Compressive Stresses ◽  
New Construction ◽  
Flexural Resistance ◽  
Ultimate Limit ◽  
Crack Widths ◽  
Post Tensioned

Current rehabilitation practices for aging, post-tensioned, voided-slab bridges typically reduce the geometric properties of the concrete cross section and so permanently increase post-tensioning stresses, change primary and secondary prestress moments, and create new primary and secondary moments because the original concrete restrains shrinkage of the new concrete. These changes affect the resistance of the rehabilitated bridge at limit states specified for new construction in the Canadian Highway Bridge Design Code (CHBDC) and may cause other limit states not currently identified in the CHBDC to govern. Rehabilitation schemes should be checked for a serviceability limit state of tensile stresses due to permanent service loads that exceed the cracking strength of the original concrete, which is typically not detailed to control crack widths. Ultimate limit states to check are (i) flexural resistance over interior supports, where the total factored demand can be increased markedly by the rehabilitation; and (ii) creep-initiated failure of concrete due to permanent compressive stresses. The application of these procedures is illustrated through example calculations for a typical continuous bridge.Key words: post-tensioned concrete, serviceability, ultimate limit state, restrained shrinkage, secondary prestress moments, critical stress, cracking.

Applications of Vector Evaluated Genetic Algorithms (VEGA) in Ultimate Limit State Based Ship Structural Design

2014 ◽  
Author(s):  
Owen Hughes ◽  
Ming Ma ◽  
Jeom Kee Paik
Keyword(s):  
Genetic Algorithms ◽  
Structural Design ◽  
Limit State ◽  
Structural Safety ◽  
Wall Structure ◽  
Ultimate Limit State ◽  
Thin Wall ◽  
Limit States ◽  
Multi Objective ◽  
Ultimate Limit

Ship structural design often deals with multiple objectives such as weight, safety, and cost. These objectives usually conflict with each other, and optimizing a particular solution with respect to a single objective can result in unacceptable results with respect to the other objectives. A reasonable solution to a multi-objective problem is to investigate a set of solutions, each of which satisfies the objectives at an acceptable level without being dominated by any other solution. Genetic algorithms have been demonstrated to be particularly effective to determine excellent solutions to these problems. In this paper a multi-objective GA, called Vector Evaluated Genetic Algorithm (VEGA) is formulated and used to optimize a large and complex thin-wall structure (a complete cargo hold of a 200,000 ton oil tanker) on the basis of weight, safety and cost. The structure weight and cost and all of the stresses are calculated using a realistic finite element model. The structure adequacy is then evaluated using the ALPS/ULSAP computer program (Paik and Thayamballi, 2003) which can efficiently evaluate all six ultimate limit states for stiffened panels and grillages. This example was chosen because the initial design is severely inadequate. The results show that the proposed method can perform ultimate strength based structural optimization with multi-objectives, namely minimization of the structural weight and cost and maximization of structural safety, and also that the method is very robust.

A proposed strategy for seismic design of steel buildings

1999 ◽  
Vol 26 (5) ◽  
pp. 564-571
Author(s):  
DJL Kennedy ◽  
M S Medhekar
Keyword(s):  
Seismic Design ◽  
Limit State ◽  
Evaluation Criteria ◽  
Design Procedure ◽  
Ultimate Limit State ◽  
Seismic Zone ◽  
Steel Buildings ◽  
Limit States ◽  
Design Earthquake ◽  
Ultimate Limit

The conceptual basis of the seismic design procedure in the National Building Code of Canada is reviewed. The design earthquake is specified only for the ultimate limit states at which the performance of both ordinary and important buildings is evaluated by an elastic static analysis in all zones. Criteria for checking the serviceability limit states, which apply to moderate earthquakes that may occur relatively frequently in the life of the building, are not specified explicitly. It is suggested that the current design approach could be improved by adopting a design strategy that addresses as well the serviceability limit states and associated evaluation criteria and gives methods for design and analysis as a function of the seismic zone and the importance of the structure. An earthquake with a return period of 1 in 50 years is proposed tentatively for the serviceability limit states with appropriate drift limits. The proposed serviceability limit states are shown to govern the design of buildings for values of the force modification factor greater, on average, than 3.Key words: analyses, earthquake, seismic design, serviceability limit state, steel, ultimate limit state.

Sign in / Sign up

Export Citation Format

Share Document