scholarly journals Improved SDOF Approach to Incorporate the Effects of Axial Loads on the Dynamic Responses of Steel Columns Subjected to Blast Loads

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Junbo Yan ◽  
Yan Liu ◽  
Fenglei Huang
Keyword(s):  
Axial Loading ◽  
Material Behavior ◽  
Dynamic Responses ◽  
Axial Loads ◽  
Global Response ◽  
Single Degree Of Freedom ◽  
Steel Columns ◽  
Transverse Loads ◽  
Good Consistency ◽  
Complex Features

In this paper, a complicated single-degree-of-freedom (SDOF) approach was developed to determine the global response of steel columns under combined axial and blast-induced transverse loads. Nonlinear section and member analyses were incorporated into the suggested SDOF method to account for the complex features of the material behavior, the high strain rate effect, and the column geometry. The SDOF technique was validated through comparisons with available finite element and experimental data, and a good consistency was obtained. Then, the validated SDOF approach was utilized to derive the pressure-impulse curves under various levels of axial loading. The level of the axial load was shown to have a significant influence on the dynamic behavior of a steel column subjected to a blast load.

Dynamic Responses of Vehicle-Track-Foundation System under Axial Loads

2012 ◽  
Vol 249-250 ◽  
pp. 274-277
Author(s):  
H.L. Zhu ◽  
Li Feng Yu ◽  
E.N. Yuan ◽  
X. Wang
Keyword(s):  
Rigid Body ◽  
High Speed ◽  
Tensile Force ◽  
Hybrid Approach ◽  
Axial Loading ◽  
Dynamic Responses ◽  
Dynamic Equations ◽  
Axial Loads ◽  
Euler Beam ◽  
Ballastless Track

Considering the effect of axial loads in the rail, this study presents a hybrid approach to investigate the dynamic responses of vehicle-track-foundation system. In this model, the vehicle is taken as a multi-rigid-body subsystem, and the ballastless track is simulated as Euler beam supported by two-layer elastic foundation. The coupled dynamic equations of system with axial loads are derived based on D’Alembert’s and Hamilton’s principles. The proposed methodology is validated through the real example to be numerically analyzed. The results show that the tensile force in rail is tending to have the amplitude of vibration decrease, and the compress force would bring the amplitude of vibration going up. So a rational axial loading is necessary to suppress the vibration of vehicle-track-foundation system when the car moving at a high speed.

Theoretical and Numerical Analysis on the Seismic Response of Underground Structures in Existence of Isolators

2011 ◽  
Vol 368-373 ◽  
pp. 710-714
Author(s):  
Jin Chun Liu ◽  
Yi Huan
Keyword(s):  
Dynamic Response ◽  
Analytical Procedure ◽  
Axial Loading ◽  
Seismic Loading ◽  
Underground Structures ◽  
Structural Dynamic ◽  
Metro Station ◽  
Single Degree Of Freedom ◽  
Theoretical And Numerical Analysis ◽  
Elastically Supported

In this paper, an analytical method of the beam with springs and dampers fixed at the ends was proposed based on equivalent single degree of freedom (SDOF) system and secondary Lagrange’s dynamic equations, in order to develop a new effective method to enhance the aseismic capability of underground structures. The dynamic response of elastically supported and damply supported beams subjected to both seismic loading and static axial loading was analyzed by the proposed analytical procedure. The theoretical results were validated by the numerical simulation. In order to further investigate the effects of springs and dampers fixed at the ends of the columns in nonlinear response situation, the 3D nonlinear seismic responses of the Dakai metro station structure with and without the isolators were analyzed by ABAQUS respectively. It is demonstrated that: (1) the proposed analytical procedure can predict the dynamic response of beams with elastic and damper supports subjected to both seismic loading and axial loading. (2) Setting isolators at the supports of the column could enhance the aseismic capability of the structure effectively. (3) The axial static loading induced by the gravity of the soil and structure provide the constraint on the column, and therefore could not be neglected in the structural dynamic analysis.

Investigation of Composite Hydrodynamic Thrust Bearing Operating Temperature Under Varying Axial Loads

2017 ◽  
Author(s):  
Kyle Myers ◽  
Collier Fais ◽  
Matthew Zacharias ◽  
Muhammad Ali ◽  
Khairul Alam
Keyword(s):  
Composite Materials ◽  
Operating Temperature ◽  
Sampling Rate ◽  
Axial Loading ◽  
Axial Loads ◽  
Axial Thrust ◽  
Thrust Bearings ◽  
Average Operating ◽  
Thrust Load ◽  
Proper Movement

The purpose of this experiment was to explore the operational behavior of hydrodynamic thrust bearings machined from various composite materials (PTFE-Filled Delrin Acetal Resin and MDS-Filled Nylon) and general Aluminum under a set of different axial loading conditions. Since thrust bearings allow mechanical components subjected to axial loads to rotate more freely, they must counter a great deal of friction which can cause bearing failure in order to maintain proper movement. In order to reduce friction and weight, this research posits that thrust bearings machined from composite materials of lower friction coefficients and densities to that of conventionally used materials such as aluminum may provide some advantages. This hypothesis was tested by machining three thrust bearings, all to the same geometric specifications (two composites and one Aluminum) and subjecting them to thrust loads of 25, 50, 75, and 100 pounds while rotating them at a constant rotational speed of 3050 RPM for 10 minutes at each load using a customized test rig. A thermocouple implanted into the bearings themselves recorded the operation temperatures at a sampling rate of 20 Hz. Based on the average temperatures recorded at the 100 pound axial/thrust load, the experiments suggest that the PTFE-Filled Delrin Acetal maintains the lowest average operating temperature of 29.5 °C, followed by the MDS-Filled Nylon at 41.6 °C and lastly the Aluminum at 54.4 °C — a trend that is observed at each axial load albeit less pronounced. These results suggest that composite materials such as PTFE-Filled Acetal and MDS-Filled Nylon to be used in lieu of conventional metals and operate at lower temperatures and lower friction.

Effects of human-induced load models on tuned mass damper in reducing floor vibration

2019 ◽  
Vol 22 (11) ◽  
pp. 2449-2463
Author(s):  
Jun Chen ◽  
Ziping Han ◽  
Ruotian Xu
Keyword(s):  
Response Spectra ◽  
Tuned Mass Damper ◽  
Design Guidelines ◽  
Degree Of Freedom ◽  
Dynamic Responses ◽  
Single Degree Of Freedom ◽  
Load Model ◽  
Load Models ◽  
Single Degree ◽  
Mass Damper

Dozens of human-induced load models for individual walking and jumping have been proposed in the past decades by researchers and are recommended in various design guidelines. These models differ from each other in terms of function orders, coefficients, and phase angles. When designing structures subjected to human-induced loads, in many cases, a load model is subjectively selected by the design engineer. The effects of different models on prediction of structural responses and efficiency of vibration control devices such as a tuned mass damper, however, are not clear. This article investigates the influence of human-induced load models on performance of tuned mass damper in reducing floor vibrations. Extensive numerical simulations were conducted on a single-degree-of-freedom system with one tuned mass damper, whose dynamic responses to six walking and four jumping load models were calculated and compared. The results show a maximum three times difference in the acceleration responses among all load models. Acceleration response spectra of the single-degree-of-freedom system with and without a tuned mass damper were also computed and the response reduction coefficients were determined accordingly. Comparison shows that the reduction coefficient curves have nearly the same tendency for different load models and a tuned mass damper with 5% mass ratio is able to achieve 50%–75% response reduction when the structure’s natural frequency is in multiples of the walking or jumping frequency. All the results indicate that a proper load model is crucial for structural response calculation and consequently the design of tuned mass damper device.

Adaptive Amplifier for a Test Vehicle Moving Over Bridges: Theoretical Study

2020 ◽  
pp. 2150042
Author(s):  
Y. B. Yang ◽  
Z. L. Wang ◽  
K. Shi ◽  
H. Xu ◽  
J. P. Yang
Keyword(s):  
Dynamic Responses ◽  
Vehicle Speed ◽  
Test Vehicle ◽  
Vehicle Performance ◽  
Single Degree Of Freedom ◽  
Closed Form Solutions ◽  
Numerical Studies ◽  
Element Simulation ◽  
Road Roughness ◽  
Overall Performance

A vibration amplifier is first proposed for adding to a test vehicle to enhance its capability to detect frequencies of the bridge under scanning. The test vehicle adopted is of single-axle and modeled as a single degree-of-freedom (DOF) system, which was proved to be successful in previous studies. The amplifier is also modeled as a single-DOF system, and the bridge as a simple beam of the Bernoulli–Euler type. To unveil the mechanism involved, closed-form solutions were first derived for the dynamic responses of each component, together with the transmissibility from the vehicle to amplifier. Also presented is a conceptual design for the amplifier. The approximations adopted in the theory were verified to be acceptable by the finite element simulation without such approximations. Since road roughness can never be avoided in practice and the test vehicle has to be towed by a tractor in the field test, both road roughness and the tractor are included in the numerical studies. For the general case, when the amplifier is not tuned to the vehicle frequency, the bridge frequencies can better be identified from the amplifier than vehicle response, and the tractor is helpful in enhancing the overall performance of the amplifier. Besides, the amplifier can be adaptively adjusted to target and detect the bridge frequency of concern. For the special case when the amplifier is tuned to the vehicle frequency, the amplifier can improve the vehicle performance by serving as a tuned mass damper, as conventionally known. This case is of limited use since it does not allow us to target the bridge frequencies. Both bridge damping and vehicle speed are also assessed with their effects addressed.

Axial loading tests on short and long hollow structural steel columns retrofitted using carbon fibre reinforced polymers

2006 ◽  
Vol 33 (4) ◽  
pp. 458-470 ◽  
Author(s):  
Amr Shaat ◽  
Amir Fam
Keyword(s):  
Carbon Fibre ◽  
Load Capacity ◽  
Axial Loading ◽  
Longitudinal Direction ◽  
Maximum Strength ◽  
Strength Gain ◽  
Steel Columns ◽  
Cfrp Sheets ◽  
Short Columns ◽  
Carbon Fibre Reinforced Polymer

This paper describes the behaviour of axially loaded short and long square hollow structural section (HSS) columns, strengthened with carbon fibre reinforced polymer (CFRP) sheets. Twenty-seven short-column and five long-column HSS specimens were tested. The effect of CFRP sheet orientation in the longitudinal and transverse directions was studied for short columns. For long columns, CFRP sheets were oriented in the longitudinal direction only. A maximum strength gain of 18% was achieved for short columns with two transverse CFRP layers. For long columns, the maximum strength gain of 23% was achieved with three longitudinal CFRP layers applied on four sides. In all CFRP-strengthened long columns, lateral deflections were reduced. Strength gain in long columns was highly dependent on the column's imperfection. As such, no correlation was established between strength gain and number of CFRP layers. CAN/CSA 16-01 equation was modified to account for CFRP through transformed section analysis so that they could be used to predict the axial-load capacity of long columns.Key words: retrofit, steel, HSS, column, FRP, carbon, buckling, strength, stiffness.

Effect of auxetic honeycomb angular stiffeners in cold-formed perforated and webbed steel upright section under buckling modes

2021 ◽  
pp. 1045389X2110282
Author(s):  
Thasan Selvakumar ◽  
Rajendran Senthil ◽  
Rajan Raj Jawahar ◽  
Soundararajan Lakshmana kumar
Keyword(s):  
Axial Load ◽  
Strain Energy ◽  
Lateral Displacement ◽  
Lateral Load ◽  
Axial Loads ◽  
Buckling Loads ◽  
Buckling Modes ◽  
Steel Columns ◽  
Maximum Resistance ◽  
Lateral Displacements

This work was carried out on the buckling effects of cold-formed perforated steel columns with base auxetic polymer stiffeners. Buckling tests were carried out for three thicknesses of steel profiles (1.5–1.8 mm) with and without base stiffeners. Loading conditions were considered to be with displacement variation of 0.1 mm/s and respective axial loads and lateral displacements were noted. Results obtained states that the lateral displacement was found to be 2.2 for 1.8 mm CFS thickness and 93 kN of axial load with the use of auxetic stiffener with 14.8% of the variation in comparison without stiffener. The strain energy of absorption for auxetic stiffener is found to be high as 0.0523 at a lateral load of 80 kN for 1.8 mm CFS thickness. The maximum resistance to local, distortional, and Euler’s buckling loads was found to be high for 1.8 mm thick CFS with stiffener with 11.1%, 17.39%, and 10% in comparison without stiffener.

Application of a Fractional Viscoelastic Material Model to Rubber in Comparison to a Linear Approach

2017 ◽  
Author(s):  
Michael Burgwitz ◽  
Johan Steffen Bothe ◽  
Matthias Wangenheim
Keyword(s):  
Viscoelastic Material ◽  
Thermoplastic Polyurethane ◽  
Material Model ◽  
Material Behavior ◽  
Constitutive Law ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Linear Approach ◽  
Important Challenge ◽  
Linear Viscoelastic

The modeling of material behavior is an important challenge in structural dynamics. While some materials can be well represented by a linear constitutive law, this becomes more complex when dealing with viscoelastic components. In this paper we investigate a fractional viscoelastic material model and present our results of research, focusing on its parametrical characteristics. We compare the results to a classical linear viscoelastic standard model and highlight advantages of the particular approach: we conduct monofrequent sinusoidal excitations using a DMTA (Dynamic Mechanic Thermal Analysis) machine. We use a viscoelastic TPU (Thermoplastic Polyurethane) sheet as sample and apply varying excitation frequencies and amplitudes. In a first modeling step we reproduce the experimental results with a fractional single degree-of-freedom system with promising results.

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