scholarly journals Characterization of Existing Steel Racks via Dynamic Identification

Buildings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 603
Author(s):  
Claudio Bernuzzi ◽  
Claudia Pellegrino ◽  
Marco Simoncelli
Keyword(s):  
Base Plate ◽  
Longitudinal Direction ◽  
Testing Procedure ◽  
Elastic Stiffness ◽  
Modal Identification ◽  
Dynamic Identification ◽  
Measurement Systems ◽  
Load Carrying ◽  
Plate Connections

Steel storage racks are widely used in logistics for storing materials and goods. Rack design is carried out by adopting the so-called design-assisted-by-testing procedure. In particular, experimental analyses must be carried out by rack producers on the key structural components in order to adopt the design approach proposed for the more traditional carpentry frames. For existing racks, i.e., those in-service for decades, it is required to evaluate the load carrying capacity in accordance with the design provisions currently in use. The main problem in several cases should be the appraisal of the key component performance, owing to the impossibility to obtain specimens from in-service racks without reduction or interruption of the logistic flows. To overcome this problem, a quite innovative procedure for the identification of the structural unknowns of existing racks has been proposed in the paper. The method is based on in-situ modal identification tests combined with extensive numerical analyses. To develop the procedure, cheap measurement systems are required, and they could be immediately applied to existing racks. A real case study is discussed, showing the efficiency of the procedure in the evaluation of the effective elastic stiffness of beam-to-column joints and base plate connections, that are parameters which remarkably affect the rack performance. The structural unknowns have been determined based on four sets of modal tests (two configurations on the longitudinal direction and two in the transversal direction) plus 9079 iterative structural analyses. The results obtained were then directly compared with experimental component tests, showing differences lower than 9%.

Fatigue strength of steel pipe-base plate connections

1983 ◽  
Vol 5 (1) ◽  
pp. 87
Author(s):  
John W Fisher ◽  
Chitoshi Miki ◽  
Roger G Slutter ◽  
Denis R Mertz ◽  
William Frank
Keyword(s):  
Fatigue Strength ◽  
Base Plate ◽  
Steel Pipe ◽  
Plate Connections

Numerical Limit Analysis of Slab Bridges with Construction Joints

2018 ◽  
Author(s):  
Thomas Westergaard Jensen ◽  
Linh Cao Hoang
Keyword(s):  
Carrying Capacity ◽  
Limit Analysis ◽  
Concrete Slabs ◽  
Load Carrying Capacity ◽  
Layer Model ◽  
Yield Criteria ◽  
Reinforced Concrete Slabs ◽  
Load Carrying ◽  
Construction Joints

The conic yield criteria for reinforced concrete slabs in bending are often used when evaluating the load‐carrying capacity of slab bridges. In the last decades, the yield criteria combined with numerical limit analysis have shown to be efficient methods to determine the load carrying capacity of slabs. However, the yield criteria overestimate the torsion capacity of slabs with high reinforcement ratios and it cannot handle slabs with construction joints. In this paper, numerical limit analysis with the conic yield criteria are compared with yield criteria based on an optimized layer model. The analysis show an increasing overestimation of the load carrying capacity for increasing reinforcement degrees. Furthermore, yield criteria, which combine the conic yield criteria with an extra linear criterion due to friction, are presented for slab bridges with construction joints. The yield criteria for slabs with construction joints are used, in combination with limit analysis, to evaluate a bridge constructed of pre‐cast overturned T‐beams and in‐situ concrete. The analysis show that the load carrying capacity is overestimated, when the construction joints are not considered in the yield criteria.

scholarly journals Effect of alkaline solutions on the tensile properties of glass-polyester pipes

2011 ◽  
pp. 185-195 ◽  
Author(s):  
Slavisa Putic ◽  
Marina Stamenovic ◽  
Jelena Petrovic ◽  
Marko Rakin ◽  
Bojan Medjo
Keyword(s):  
Tensile Properties ◽  
Construction Materials ◽  
Ammonium Hydroxide ◽  
Longitudinal Direction ◽  
Testing Procedure ◽  
Circumferential Direction ◽  
Process Equipment ◽  
Alkaline Solutions ◽  
Ph Values ◽  
Definite Structure

Construction materials, traditionally used in process equipment, are today successfully replaced by composite materials. Hence, many pipes are made of these materials. The subject of this study was the influence of liquids on the state of stresses and tensile strengths in the longitudinal and circumferential direction of glass-polyester pipes of a definite structure and known fabrication process. These analyses are of great importance for the use of glass-polyester pipes in the chemical industry. The tensile properties (the ultimate tensile strength and the modulus of elasticity) were tested and determined for specimens cut out of the pipes; flat specimens for the tensile properties in the longitudinal direction and ring specimens for the tensile properties in the circumferential direction. First, the tension test was performed on virgin samples (without the influence of any liquid), to obtain knowledge about the original tensile properties of the material composite studied. Subsequently, the specimens were soaked in alkaline solutions: sodium hydroxide (strong alkali) and ammonium hydroxide (weak alkali). These solutions were selected because of their considerable difference in pH values. The specimens and rings were left for 3, 10, 30 and 60 days in each liquid at room temperature. Then, the samples were tested on tension by the standard testing procedure. A comparison of the obtained results was made based on the pH values of the aggressive media in which the examined material had been soaked, as well as based on the original tensile properties and the number of days of treatment. Micromechanical analyses of sample breakage helped in the elucidation of the influence of the liquids on the structure of the composite pipe and enabled models and mechanisms that produced the change of strength to be proposed.

Mechanics of the human femoral adventitia including the high-pressure response

2002 ◽  
Vol 282 (6) ◽  
pp. H2427-H2440 ◽  
Author(s):  
Christian A. J. Schulze-Bauer ◽  
Peter Regitnig ◽  
Gerhard A. Holzapfel
Keyword(s):  
High Pressures ◽  
Energy Functions ◽  
Mean Values ◽  
Mechanical Responses ◽  
Strongly Nonlinear ◽  
Pressure Load ◽  
Nonlinear Mechanical ◽  
Load Carrying

Adventitial mechanics were studied on the basis of adventitial tube tests and associated stress analyses utilizing a thin-walled model. Inflation tests of 11 nonstenotic human femoral arteries (79.3 ± 8.2 yr, means ± SD) were performed during autopsy. Adventitial tubes were separated anatomically and underwent cyclic, quasistatic extension-inflation tests using physiological pressures and high pressures up to 100 kPa. Associated circumferential and axial stretches were typically <20%, indicating “adventitiosclerosis.” Adventitias behaved nearly elastically for both loading domains, demonstrating high tensile strengths (>1 MPa). The anisotropic and strongly nonlinear mechanical responses were represented appropriately by two-dimensional Fung-type stored-energy functions. At physiological pressure (13.3 kPa), adventitias carry ∼25% of the pressure load in situ, whereas their circumferential and axial stresses were similar to the total wall stresses (∼50 kPa in both directions), supporting a “uniform stress hypothesis.” At higher pressures, they became the mechanically predominant layer, carrying >50% of the pressure load. These significant load-carrying capabilities depended strongly on circumferential and axial in-vessel prestretches (mean values: 0.95 and 1.08). On the basis of these results, the mechanical role of the adventitia at physiological and hypertensive states and during balloon angioplasty was characterized.

Instantaneous Identification of Polynomial Nonlinearity Based on Volterra Series Representation

2005 ◽  
Vol 293-294 ◽  
pp. 703-710 ◽  
Author(s):  
Giacomo V. Demarie ◽  
Rosario Ceravolo ◽  
Alessandro de Stefano
Keyword(s):  
Structural Engineering ◽  
Volterra Series ◽  
Series Representation ◽  
Consistent Estimate ◽  
Short Time Fourier Transform ◽  
Dynamic Identification ◽  
Polynomial Nonlinearity ◽  
Definition Of ◽  
Short Time

In structural engineering applications a sufficient quantity of experimental data to be able to achieve a consistent estimate of nonlinear quantities is seldom available: this applies in particular when the structures are to be tested in situ. This report discusses the definition of instantaneous estimators to be used in the dynamic identification of invariant nonlinear systems on the basis of Short-Time Fourier Transform representation of excitation and system’s response and within the framework of a Volterra series representation of the input/output relationship. An estimation of the parameters of a dynamic system can be worked out from the evolution of such instantaneous estimators.

S7-13 Detecting Voids in Tendon Ducts of Post-Tensioned Bridge Girders

2013 ◽  
Vol 639-640 ◽  
pp. 1015-1020
Author(s):  
Gui Hua Dai ◽  
Xian Yan Zhou
Keyword(s):  
Frequency Domain ◽  
Data Interpretation ◽  
Bridge Girders ◽  
Impact Echo ◽  
Condition Evaluation ◽  
Load Carrying ◽  
History Of ◽  
Post Tensioned

The tendon ducts in post-tensioned bridge girders must be grouted fully so as to prevent water and oil stain from entering the ducts, which will decrease the durability and load-carrying capacity of post-tensioned bridges badly. This paper describes the motivations for and recent history of Impact-Echo (IE) scanning applications to internal grout condition evaluation of tendon ducts in post-tensioned girders. The tendon ducts’ internal injection quality of a railway bridge in Yichang city was evaluated using IE technology. During the in-situ testing, the IE signals were collected firstly, then the transformation from the time to the frequency domain was carried out using the principles of the fast Fourier transform, data interpretation was much simpler and quicker in the frequency domain. The grout condition of tendon ducts could be determined according to the frequency analysis, poorly grouted sections can be differentiated from the well-grouted sections within the tendon ducts. Results show that the IE method can be employed to detect voids in the grouted tendon ducts of many types of post-tensioned structures.

Effects of sample disturbance on the stress-induced microfracturing characteristics of brittle rock

1999 ◽  
Vol 36 (2) ◽  
pp. 239-250 ◽  
Author(s):  
E Eberhardt ◽  
D Stead ◽  
B Stimpson
Keyword(s):  
Crack Initiation ◽  
Elastic Stiffness ◽  
In Situ Stress ◽  
Brittle Rock ◽  
Stress Threshold ◽  
Fracture Crack ◽  
Sample Disturbance ◽  
Underground Research Laboratory ◽  
Stress Domains

The effects of sampling disturbance on the laboratory-derived mechanical properties of brittle rock were measured on cored samples of Lac du Bonnet granite taken from three different in situ stress domains at the Underground Research Laboratory of Atomic Energy of Canada Limited. A variety of independent measurements and scanning electron microscope observations demonstrate that stress-induced sampling disturbance increased with increasing in situ stresses. The degree of damage was reflected in laboratory measurements of acoustic velocity and elastic stiffness. Examination of the stress-induced microfracturing characteristics during uniaxial compression of the samples revealed that the degree of sampling disturbance had only minor effects on the stress levels at which new cracks were generated (i.e., the crack initiation stress threshold). Crack-coalescence and crack-damage thresholds, on the other hand, significantly decreased with increased sampling disturbance. The presence of numerous stress-relief cracks in the samples retrieved from the highest in situ stress domains was seen to weaken the rock by providing an increased number of planes of weakness for active cracks to propagate along. A 36% strength decrease was seen in samples retrieved from the highest in situ stress domain (sigma1 - sigma3 approximate 40 MPa) as compared with those taken from the lowest in situ stress domain (sigma1 - sigma3 approximate 10 MPa).Key words: sample disturbance, brittle fracture, crack initiation, crack propagation, material properties, rock failure.

Experimental Test of Welded Wide Flange Fuses

2018 ◽  
Vol 763 ◽  
pp. 414-422 ◽  
Author(s):  
Tony Y. Yang ◽  
Winda Banjuradja ◽  
Lisa Tobber
Keyword(s):  
Energy Dissipation ◽  
Longitudinal Direction ◽  
Elastic Stiffness ◽  
Design Parameters ◽  
Structural Components ◽  
Earthquake Energy ◽  
Aspect Ratios ◽  
Metallic Dampers ◽  
Energy Dissipation Capacity ◽  
Metallic Damper

Metallic dampers are one of the most prevalent structural components that are used to dissipate earthquake energy. A novel metallic damper, named Welded Wide Flange Fuse (WWFF), is proposed in this paper. WWFF utilizes commonly available welded wide flange sections to dissipate the earthquake energy through shear yielding of the web in the longitudinal direction, which makes the WWFF easy to be fabricated and efficient in providing high elastic stiffness and stable energy dissipation capacity. In this paper, a detailed experimental study was conducted to examine the influence on the design parameters (such as aspect ratios and slenderness ratios) on the component response (such as yielding force and elastic stiffness). The result shows that the WWFF has stable energy dissipation capacity which can be used as an efficient and robust metallic damper.

Aeroderivative Gas Turbine Coupling Generator Redesign

2013 ◽  
Author(s):  
Alejandro Hernández Rossette ◽  
Rafael García Illescas ◽  
Zdzislaw Mazur
Keyword(s):  
Gas Turbines ◽  
Longitudinal Direction ◽  
Rehabilitation Process ◽  
Root Cause ◽  
Dynamic Forces ◽  
Failure Event ◽  
Couple Analysis ◽  
Original Configuration ◽  
Total Fracture

A major failure event was experienced at a 44 MW plant powered by four aeroderivative gas turbines arranged in two units, property of the Federal Commission of Electricity (CFE). The failure consisted of total fracture in the shaft coupling between the generator and free-turbine. Unit 2 has a twin pack configuration with two aero derivative Pratt&Whitney 20 MW gas turbines coupled to one generator at both end sides. The “A” side generator coupling was completely damaged as well as the coupling configuration at the free turbine. Failure analysis showed as root cause, an abnormal configuration of the coupling systems between the free turbine to rotor generator at side “A”. This side had an additional shaft component to compensate a longer coupling distance between the turbine and generator. This was longer than the original distance, generating additional dynamic forces during operation leading to a fatigue failure mechanism. The replacement coupling configuration for the rotor generator was different than the Original Equipment Manufacturer (OEM). The new (non-OEM) spare rotor generator was shorter in the longitudinal direction than the original one, forcing the addition of a new shaft in one side of the generator. This work describes the rehabilitation process of the generator coupling by the replacement of the old configuration by a new redesigned coupling. This was done keeping the original configuration distances and components for both end shaft sides of the rotor generator. The paper includes the redesigned couple analysis by finite element method and the in-situ activities for the installation of the new couple in the rotor generator.

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