scholarly journals Platform for dynamic tests: preliminary studies, design and construction

2013 ◽  
Vol 6 (1) ◽  
pp. 55-74 ◽  
Author(s):  
J. E. Campuzano ◽  
R. de Castro ◽  
S. Ávila ◽  
G. Doz
Keyword(s):  
Natural Frequencies ◽  
Limit State ◽  
Physical Space ◽  
Dynamic Responses ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Dynamic Tests ◽  
Short Columns ◽  
Brazilian Standard ◽  
Design And Construction

This paper is about the design and construction of a platform for dynamic tests especially with people jumping, walking, etc. Initially it was tried to find out projects already implemented in platforms and dynamic tests and to study the loads produced by movement of people on slabs and the structural response to these loads. The limits established by different standards have been also studied for these dynamic responses, taking into account the ultimate limit state, as well as the structure in service, since the human body is very sensitive to structural vibrations. Parametric studies were performed considering various configurations of slabs (different spans, thicknesses and conditions of support) have been done, looking for a configuration that could have natural frequency close to the frequencies of the human loads. The slab should have dimensions compatible with the available physical space, fundamental frequency below 5 Hz and maximum immediate deflection compatible with the indications of the Brazilian standard NBR6118: 2007. Based on these criteria was chosen a rectangular structure consists of a solid reinforced concrete rectangular slab studded in two opposite edges of steel beams with shear connectors type U. The other two edges are free. The steel beams supporting the slab, in turn, are supported on eight metal profiles (two in each corner of the slab) that are supported on two to two short columns of steel profile H. Profiles U in steel are welded to four columns, forming a horizontal frame. Numerical analysis of the dynamic test platform have been performed for free and forced vibration, for obtaining the natural frequencies and corresponding vibration modes, considering the self-weight of the structure and the load that simulates people's weight. After obtaining a structural configuration that fulfilled the stipulated requirements, the design of the slab taking into account the recommendations of the Brazilian standard NBR6118: 2007. The platform was built and has been done a preliminary experimental study to obtain the first natural frequencies.

Combined flexure and torsion of I-shaped steel beams

1989 ◽  
Vol 16 (2) ◽  
pp. 124-139 ◽  
Author(s):  
Robert G. Driver ◽  
D. J. Laurie Kennedy
Keyword(s):  
Limit State ◽  
Bending Moment ◽  
Phase Behaviour ◽  
Inelastic Interaction ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Second Phase ◽  
Design Standards ◽  
Limit States ◽  
Interaction Diagram

Design standards provide little information for the design of I-shaped steel beams not loaded through the shear centre and therefore subjected to combined flexure and torsion. In particular, methods for determining the ultimate capacity, as is required in limit states design standards, are not presented. The literature on elastic analysis is extensive, but only limited experimental and analytical work has been conducted in the inelastic region. No comprehensive design procedures, applicable to limit states design standards, have been developed.From four tests conducted on cantilever beams, with varying moment–torque ratios, it is established that the torsional behaviour has two distinct phases, with the second dominated by second-order geometric effects. This second phase is nonutilizable because the added torsional restraint developed is path dependent and, if deflections had been restricted, would not have been significant. Based on the first-phase behaviour, a normal and shearing stress distribution on the cross section is proposed. From this, a moment–torque ultimate strength interaction diagram is developed, applicable to a number of different end and loading conditions. This ultimate limit state interaction diagram and serviceability limit states, based on first yield and on distortion limitations, provide a comprehensive design approach for these members. Key words: beams, bending moment, flexure, inelastic, interaction diagram, I-shaped, limit states, serviceability, steel, torsion, torque, ultimate.

Dynamic Responses of Jacket-Type Offshore Wind Turbines Using Decoupled and Coupled Models

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Muk Chen Ong ◽  
Erin E. Bachynski ◽  
Ole David Økland
Keyword(s):  
Wind Turbines ◽  
Limit State ◽  
Coupled Model ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Ultimate Limit State ◽  
Coupled Models ◽  
Offshore Wind Turbines ◽  
Thrust And Torque ◽  
Rotor Model

This paper presents numerical studies of the dynamic responses of two jacket-type offshore wind turbines (OWTs) using both decoupled and coupled models. The investigated structures are the OC4 (Offshore Code Comparison Collaboration Continuation) jacket foundation and a full-lattice support structure presented by Long et al., 2012, “Lattice Towers for Bottom-Fixed Offshore Wind Turbines in the Ultimate Limit State: Variation of Some Geo metric Parameters,” ASME J. Offshore Mech. Arct. Eng., 134(2), p. 021202. Both structures support the NREL 5-MW wind turbine. Different operational wind and wave loadings at an offshore site with relatively high soil stiffness are investigated. In the decoupled (hydroelastic) model, the thrust and torque from an isolated rotor model were used as wind loads on the decoupled model together with a linear aerodynamic damper. The coupled model is a hydro-servo-aero-elastic representation of the system. The objective of this study is to evaluate the applicability of the computationally efficient linear decoupled model by comparing with the results obtained from the nonlinear coupled model. Good agreement was obtained in the eigen-frequency analysis, decay tests, and wave-only simulations. It was also found that, by applying the thrust force from an isolated rotor model in combination with linear damping, reasonable agreement could be obtained between the decoupled and coupled models in combined wind and wave simulations.

scholarly journals Design and Analysis of a Braceless Steel 5-MW Semi-Submersible Wind Turbine

2016 ◽  
Author(s):  
Chenyu Luan ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Numerical Analysis ◽  
Wind Turbine ◽  
Global Analysis ◽  
Limit State ◽  
Dynamic Responses ◽  
Ultimate Limit State ◽  
Horizontal Axis Wind Turbine ◽  
Design Data ◽  
Intact Stability ◽  
Central Column

This paper introduces the design data and numerical analysis of a braceless steel semi-submersible wind turbine. The hull of the semi-submersible wind turbine is designed to support a reference 5-MW horizontal axis wind turbine at a site in the northern North Sea. The hull is composed of a central column, three side columns and three pontoons. The side columns and pontoons are arranged radially outward from the central column which is used to support the wind turbine. The side columns form the corners of a triangle on the horizontal plane and are connected by the pontoons to the central column at the bottom to form an integrated structure. Numerical analysis has been carried out to analyze the intact stability, natural periods and modes and global dynamic responses in winds and waves. Results of the numerical analysis show that the design has very good intact stability, well designed natural periods and modes, moderate rigid-body motions in extreme environmental conditions and a reasonable structural design. This paper emphasizes the structural responses of the hull considering both the global and local load effects. The global forces and moments in the hull are calculated by carrying out time-domain global analysis and used as inputs for simplified ultimate limit state design checks for structural strength of the hull. The design can be used as a reference semi-submersible wind turbine.

Considering Catenary Action in Designing End-Restrained Steel Beams in Fire

2005 ◽  
Vol 8 (3) ◽  
pp. 309-324 ◽  
Author(s):  
H. X. Yu ◽  
J. Y. Richard Liew
Keyword(s):  
Design Method ◽  
Load Capacity ◽  
Limit State ◽  
Beam Deflection ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Ultimate Load Capacity ◽  
Element Analysis ◽  
Catenary Action ◽  
In Fire

When a building compartment is subjected to fire attack, there are complex interactions between the fire affected members with the surrounding members. The behaviour of the steel frame members in fire can be drastically different from that of its member in isolation. This paper studies the behaviour of steel beams with the increase of temperature from beam action phase to catenary action phase and until failure. The load bearing mechanism in the catenary action phase is discussed and the failure criterion is defined. A new ultimate limit state based on 15% maximum strain of steel material at elevated temperature is proposed to determine the ultimate load capacity of beams failed in the catenary action phase. Wide ranges of beam parameters including various beam sizes and span lengths with different degrees of end restraints are studied. Comparison of results with those obtained from nonlinear finite element analysis shows that the proposed design method could enhance the critical temperature of steel beams by over 200 °C if proper attention is given to the integrity of connections to resist the catenary force. In this respect, methods to estimate the catenary force and beam deflection are provided.

scholarly journals Graphical tool for assessing the critical temperatures of steel beams and columns in fire

Fire Research ◽  
2018 ◽  
Author(s):  
Valdir Pignatta Silva ◽  
Arthur Ribeiro Melão ◽  
Igor Pierin
Keyword(s):  
Critical Temperature ◽  
Design Method ◽  
Limit State ◽  
Local Buckling ◽  
Steel Beams ◽  
Ultimate Limit State ◽  
Structural Element ◽  
Critical Temperatures ◽  
Graphical Tool ◽  
In Fire

In a fire situation, the temperature in which the ultimate limit state of the structural element is reached is called critical temperature. It is very laborious to determine it. The aim of this work was to create a graphical tool to allow quick determination of the critical temperature of I shaped columns and beams without local buckling. The method used was based on the Brazilian standard and using AcoInc software developed by the authors. The result was a tool whose similarity was not found in the literature. The use of the tool developed in this study simplifies the use of the standardized design method. One conclusion to be highlighted is one in which constants values of the critical temperature, generally accepted in practice, may be unsafe.

scholarly journals Fragility curves for Italian URM buildings based on a hybrid method

2021 ◽  
Author(s):  
A. Sandoli ◽  
G. P. Lignola ◽  
B. Calderoni ◽  
A. Prota
Keyword(s):  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Limit State ◽  
Ultimate Limit State ◽  
Masonry Building ◽  
Masonry Buildings ◽  
Seismic Behaviour ◽  
Building Stock ◽  
Ground Acceleration ◽  
Damage Scenario

AbstractA hybrid seismic fragility model for territorial-scale seismic vulnerability assessment of masonry buildings is developed and presented in this paper. The method combines expert-judgment and mechanical approaches to derive typological fragility curves for Italian residential masonry building stock. The first classifies Italian masonry buildings in five different typological classes as function of age of construction, structural typology, and seismic behaviour and damaging of buildings observed following the most severe earthquakes occurred in Italy. The second, based on numerical analyses results conducted on building prototypes, provides all the parameters necessary for developing fragility functions. Peak-Ground Acceleration (PGA) at Ultimate Limit State attainable by each building’s class has been chosen as an Intensity Measure to represent fragility curves: three types of curve have been developed, each referred to mean, maximum and minimum value of PGAs defined for each building class. To represent the expected damage scenario for increasing earthquake intensities, a correlation between PGAs and Mercalli-Cancani-Sieber macroseismic intensity scale has been used and the corresponding fragility curves developed. Results show that the proposed building’s classes are representative of the Italian masonry building stock and that fragility curves are effective for predicting both seismic vulnerability and expected damage scenarios for seismic-prone areas. Finally, the fragility curves have been compared with empirical curves obtained through a macroseismic approach on Italian masonry buildings available in literature, underlining the differences between the methods.

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.

Inspection and Model Experiment of a Damaged Arch Bridge

2007 ◽  
Vol 340-341 ◽  
pp. 223-228
Author(s):  
Ying Fang Fan ◽  
Zhi Qiang Hu ◽  
Jing Zhou
Keyword(s):  
Model Experiment ◽  
Dynamic Test ◽  
Dynamic Responses ◽  
Dynamic Tests ◽  
Arch Bridge ◽  
Mechanical Responses ◽  
Organic Glasses ◽  
Bridge Model ◽  
Static And Dynamic Tests ◽  
Good Agreement

The structural behavior of an old six-span reinforced concrete arch bridge, which has been in service for about 40 years, is investigated. Field monitoring (inclusive of test of material property, static and dynamic test of the bridge) was conducted, static and dynamic responses of the bridge are obtained. Based on the primitive bridge, a scaled one-span bridge model was fabricated by organic-glasses. Both the static and dynamic tests were executed on the bridge model in the laboratory. Since the arch rib is the crucial member for the arch bridge, 7 notches were cut on both arch ribs of the bridge model to simulate different damages of the arch rib. Mechanical responses of the bridge with different damages on the arch ribs were achieved. FEM analyses were preformed on the bridge as well. Numerical results show good agreement with the experimental results.

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