Prediction and Validation of Design Loads of Satellite Components Using Modal Mass Acceleration Curve

A process, called Bio-Denipho, for combined biological phosphorus and nitrogen removal in a combination of an anaerobic tank and two oxidation ditches is described. In this process the anaerobic tank consisting of three sections working in series is followed by two oxidation ditches. These too are working in series, but with both inlet to and outlet from the tanks changing in a cycle. The Bio-Denipho process is described specifically for the process itself and as a case study for the implementation of the process on a 265,000 pe wastewater treatment plant for the city of Aalborg in Denmark. The plant was designed and erected in two stages and the last stage was inaugurated October 31,1989. Lay-out and functions for the plant is described and design loads, plan lay-out and tank volumes are given in this paper together with performance data for the first year in operation.

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Flexural Performance of RC Beams Strengthened with Externally-Side Bonded Reinforcement (E-SBR) Technique Using CFRP Composites

Materials ◽

10.3390/ma14112809 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2809

Author(s):

Md. Akter Hosen ◽

Fadi Althoey ◽

Mohd Zamin Jumaat ◽

U. Johnson Alengaram ◽

N. H. Ramli Sulong

Keyword(s):

Absorption Capacity ◽

Experimental Program ◽

Rc Beams ◽

Rc Structures ◽

Functional Changes ◽

Flexural Strengthening ◽

Cfrp Laminates ◽

Flexural Performance ◽

Design Loads ◽

Predicted Values

Reinforced concrete (RC) structures necessitate strengthening for various reasons. These include ageing, deterioration of materials due to environmental effects, trivial initial design and construction, deficiency of maintenance, the advancement of design loads, and functional changes. RC structures strengthening with the carbon fiber reinforced polymer (CFRP) has been used extensively during the last few decades due to their advantages over steel reinforcement. This paper introduces an experimental approach for flexural strengthening of RC beams with Externally-Side Bonded Reinforcement (E-SBR) using CFRP fabrics. The experimental program comprises eight full-scale RC beams tested under a four-point flexural test up to failure. The parameters investigated include the main tensile steel reinforcing ratio and the width of CFRP fabrics. The experimental outcomes show that an increase in the tensile reinforcement ratio and width of the CFRP laminates enhanced the first cracking and ultimate load-bearing capacities of the strengthened beams up to 141 and 174%, respectively, compared to the control beam. The strengthened RC beams exhibited superior energy absorption capacity, stiffness, and ductile response. The comparison of the experimental and predicted values shows that these two are in good agreement.

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Effect of Frequency Characteristics of Ground Motion on Response of Tuned Mass Damper Controlled Inelastic Concrete Frame

Buildings ◽

10.3390/buildings11020074 ◽

2021 ◽

Vol 11 (2) ◽

pp. 74

Author(s):

Md Motiur Rahman ◽

Tahmina Tasnim Nahar ◽

Dookie Kim

Keyword(s):

Ground Motion ◽

Structural Response ◽

Tuned Mass Damper ◽

Frequency Characteristics ◽

Building Frames ◽

Concrete Frame ◽

Finite Element Software ◽

Mass Damper ◽

Lateral Displacements ◽

Modal Mass

This paper investigates the performance of tuned mass damper (TMD) and dynamic behavior of TMD-controlled concrete structure considering the ground motion (GM) characteristics based on frequency content. The effectiveness of TMD in reducing the structural response and probability of collapse of the building frames are affected by the frequency characteristics of GMs. To attenuate the seismic vibration of the buildings, the TMD controlled building has been designed based on the modal analysis (modal frequencies and modal mass participation ratio). In this study, to investigate the performance of TMD, four different heights (i.e., 3, 5, 10, 20 stories) inelastic concrete moment-resisting frames equipped with TMDs are developed using an open-source finite element software. A series of numerical analyses have been conducted using sixty earthquakes classified into three categories corresponding to low, medium, and high-frequency characteristics of GMs. To evaluate the proposed strategy, peak lateral displacements, inter-story drift, and the probability of collapse using fragility analysis have been investigated through the structures equipped with and without TMD. The results appraise the effect of TMD and compare the seismic responses of earthquake frequency contents and the vibration control system of the inelastic building frames.

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The Reduction of Bias Error in Transfer Function Estimates Using FFT-Based Analyzers

Journal of Vibration and Acoustics ◽

10.1115/1.3269148 ◽

1984 ◽

Vol 106 (1) ◽

pp. 29-35 ◽

Cited By ~ 7

Author(s):

P. Cawley

Keyword(s):

Transfer Function ◽

Random Excitation ◽

Analogue Computer ◽

Bias Error ◽

Testing Time ◽

Theoretical Predictions ◽

Set Up ◽

Modal Mass ◽

Time Required ◽

Good Agreement

The susceptibility to bias error of two methods for computing transfer (frequency response) functions from spectra produced by FFT-based analyzers using random excitation has been investigated. Results from tests with an FFT analyzer on a single degree-of-freedom system set up on an analogue computer show good agreement with the theoretical predictions. It has been shown that, around resonance, the bias error in the transfer function estimate H2 (Syy/Sxy*) is considerably less than that in the more commonly used estimate, H1 (Sxy/Sxx). The record length, and hence the testing time, required for a given accuracy is reduced by over 50 percent if the H2 calculation procedure is used. The analysis has also shown that if shaker excitation is used on lightly damped structures with low modal mass, it is important to minimize the mass of the force gage and the moving element of the shaker.

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Analytical Simulation of Dynamically Equivalent Components

Journal of Pressure Vessel Technology ◽

10.1115/1.3264803 ◽

1986 ◽

Vol 108 (4) ◽

pp. 394-400

Author(s):

Z. N. Ibrahim

Keyword(s):

Dynamic Characteristic ◽

Dynamic Model ◽

Single Degree Of Freedom ◽

Residual Mass ◽

Single Degree ◽

Modal Synthesis ◽

Stiffness Matrices ◽

Analytical Simulation ◽

Modal Mass ◽

Residual Stiffness

The inertia concept of modal mass was developed to provide a consistent methodology for establishing an analytically equivalent dynamic model of any discrete section within a complex piping network. The multidegree of freedom system is reduced to several multiple excitation single degree of freedom (SDOF) systems representing its modal masses and modal stiffnesses. The multiple excitation residual mass and residual stiffness matrices were also formulated. The combination of modal mass-modal stiffness SDOF systems and residual mass-residual stiffness matrices can simulate the complete dynamic characteristic of any desired portion of the piping network. This technique was extended to cover substructuring applications, and was proved mathematically to be equivalent to the conventional modal synthesis formulation.

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Design Forces for Drift and Damage Control: A Second Look at the Substitute Structure Approach

Earthquake Spectra ◽

10.1193/1.1585776 ◽

1994 ◽

Vol 10 (2) ◽

pp. 319-331 ◽

Cited By ~ 3

Author(s):

John F. Bonacci

Keyword(s):

Reinforced Concrete ◽

Damage Control ◽

Dynamic Test ◽

Frame Structures ◽

Rc Frame ◽

Test Results ◽

Structure Approach ◽

Maximum Displacement ◽

Design Loads ◽

Rc Frame Structures

This paper explores the development of a method that is useful for design of reinforced concrete (RC) frame structures to resist earthquakes. The substitute structure method, originally proposed in the 1970s, makes an analogy between viscously damped linear and hysteretic response for the purpose of estimating maximum displacement. The evolution of the method is retraced in order to emphasize its unique reliance on experimental results, which are needed to establish rules for assignment of substitute linear properties. Recent dynamic test results are used to extend significantly the calibration of the method, which furnishes design loads on the basis of drift and damage control.

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