Equivalent Design Method Research Articles

Experimental study of boiling critical heat flux with low mass flux under motion condition in a wetted perimeter equivalent rod

The significance of floating nuclear power plant has recently surged as a viable solution for addressing ocean energy supply issues, while also meeting energy conservation and emission reduction goals. During the initial phase of nuclear reactor startup or in the event of a LOCA (Loss of Coolant Accident), the occurrence of critical heat flux (CHF) at exceptionally low mass flux in the core of floating nuclear power plant is a possibility. This underscores the importance of CHF safety characteristics of floating nuclear power plant. Despite this, there has been a noticeable absence of published experimental research on CHF under motion conditions with high operational parameters. To bridge this gap, CHF experiments were carried out on rod test sections under both static and motion conditions, employing the wetted perimeter equivalent design method. This study scrutinized the impact of system variables on CHF and evaluated the effectiveness of the design strategy based on the wetted perimeter equivalent method, using experimental data as a reference. Additionally, it elucidated the CHF mechanism and identified the penalty factor on CHF under conditions of inclination, rolling, and heaving, with the maximum penalty factor reaching up to 15%. The insights gained from this research are instrumental in guiding the CHF test scheme design under motion conditions and lay a foundational basis for the thermal design of floating nuclear power plant.

Probabilistic Seismic Evaluation and Experimental Tests of Multi-Direction Damping System on a Super-Long Column-Pylon Cable-Stayed Bridge

ABSTRACT In view of the insufficiency of bidirectional seismic control of long-span cable-stayed bridges as well as the limitations of existing schemes, a multi-direction damping system (MDDS) was proposed and investigated in this manuscript, which can provide seismic resistance bidirectionally. The new damping system owned a unique middle connecting structure, which overcomes the disadvantages that axial instability caused of excessive long rod and the demand of large installing space of traditional dampers. Both the performance stability and constitutive relationship of MDDS were verified by engineering tests, and the equivalent design method was then proposed and proved to be applicable. A detailed finite element numerical model of a super-long (main span over 800 m) column-type pylon cable-stayed bridge which equipped with MDDS in practice was established, the fragility curves of critical components were obtained by non-linear time history analysis, which exhibited the high efficiency of MDDS seismic performance in both transversal and longitudinal directions. Through extracting the median fragility value of 35 sections of the pylon under four damping cases, i.e. setting dampers transversely (TDS), longitudinally (LDS), bidirectionally (BDS), and MDDS, it can be concluded that MDDS performed far better on seismic resistance than LDS and TDS, and made the similar contribution with BDS. On account of half number of damper setting and the reduction in installing space demand, MDDS becomes the optimal choice in practical application for its economic efficiency and superiority. Furthermore, the optimal horizontal installing angle of MDDS was derived through six angle cases which was based on the system-level fragility curves comparison.

Simplified implementation of equivalent and ductile performance for steel-FRP composite bars reinforced seawater sea-sand concrete beams: equal-stiffness design method

To overcome the steel corrosion and shortage of river sand and freshwater, the combination of steel-FRP composite bar (SFCB) and seawater sea-sand concrete provides a promising alternative. As the stress–strain relationship of SFCB is quite different, the design method of steel bar or FRP bar reinforced concrete beam cannot be applied directly to SFCB reinforced concrete (SFCB-RC) beam. Here, a simplified equivalent design method, i.e. equal-stiffness design method, is proposed, where the total longitudinal reinforcement stiffness of SFCB-RC beam is equal to that of steel bar reinforced concrete (S-RC) beam. The flexural behavior of equal-stiffness-designed SFCB-RC beams is investigated experimentally. The results show that compared with S-RC beams, equal-stiffness-designed SFCB-RC beams have similar failure modes, equal deflection, and acceptable crack width. The post-yielding stiffness contributes to 14.3%-54.5% larger load-carrying capacity and 47.0%-189.1% higher ductility coefficient. Consequently, equal-stiffness design method contributes to a better flexural performance of SFCB-RC beams compared with S-RC beams and provides a simple and reliable way to directly refer to the design method of S-RC beams, facilitating the design and application of SFCB-RC beams. Furthermore, an analytical model to predict the load-carrying capacity, deflection, and crack width of SFCB-RC beams is preliminarily developed and evaluated.

Mean‐square strong stability and stabilization of discrete‐time stochastic systems with multiplicative noises

AbstractThis article investigates the mean‐square strong stability and stabilization of a discrete‐time stochastic system corrupted by multiplicative noises. First, the definition of the mean‐square (MS) strong stability is addressed to avoid overshoots in system dynamics, and two necessary and sufficient conditions for the MS‐strong stability are derived. Moreover, the relationship between MS‐strong stability and MS‐stability is given. Second, some necessary and sufficient conditions of the MS‐strong stabilization via state feedback (SF) and output feedback are obtained, respectively. Furthermore, analytical expressions of SF controller and static output feedback (SOF) controller are proposed, respectively. Finally, an equivalent design method for SOF controller and dynamic output feedback controller is presented.

Analysis of horizontal vibration characteristics of unequal height twin towers of rigid connected structure

The twin-tower concatenated building with unequal height is highly favored by architects, because of its distinctive appearance and specific building function. Recently, the dynamic characteristics and earthquake action of the unequal height twin towers with the rigid connected structures have been assessed utilizing engineering experience and finite element analysis. However, the technical guidance at the theoretical level is rarely reported. Here, to reveal the dynamic characteristics of unequal height twin towers with the rigid connected structures, the equivalent design method for isolated structures was employed. The Higher Tower (S1) is equivalent to a two-particle two-degree-of-freedom system in the unequal height twin towers with a maximum height of 60 m, while the Lower Tower (S2) is equivalent to a single particle one-degree-of-freedom system. The variation law of their first-order natural vibration periods in the parallel conjoined direction was then analyzed using a simplified structural dynamics method. To investigate the coupling of frequencies and changing law of mode shapes, a three-degree-of-freedom system was established in the vertical conjoined direction. The simplified structural dynamics models were compared to the finite element simulation and validated further by an engineering practice. The results indicate that there are numerous plane and torsion coupling modes in the direction of the vertical rigid connection. The equipment and function area with heavy load should be set in the S1 area when the total stiffness meets the requirements in the direction of the vertical rigid connecting body, whereas the stiffness of the S2 should be controlled to the lowest extent. By analyzing engineering examples and comparing them to numerical simulations, the simplified structural dynamics methods can be used to control and optimize the design scheme to determine a reasonable position for the connecting body within the tower height.

Novel adaptive hysteretic damper for enhanced seismic protection of braced buildings

Traditional bilinear hysteretic dampers (BHDs) are installed in buildings to enhance their seismic performance by increasing the effective stiffness and damping and are usually designed to guarantee the structural safety for severe ultimate limit state seismic events. As a negative consequence, only minimal damping is provided during weak but more frequent serviceability limit state earthquakes since BHDs mainly operate in their elastic regime. This can cause high peak floor accelerations (PFAs) that are detrimental for sensitive non-structural components (NSCs), like electric network, elevators, false ceilings, and computers, whose integrity is crucial in high-technological buildings (e.g. hospitals, and emergency centers). In order to improve this unacceptable situation, a novel adaptive hysteretic damper (AHD) has been developed by the authors. The AHD can modulate its effective damping and stiffness to the intensity (e.g. peak ground acceleration) of the occurring earthquake leading to: (i) reduced PFAs and enhanced NSCs protection for minor earthquakes; (ii) not impaired structural safety under major severe events. In this paper the force-displacement response of the AHD is experimentally assessed and a simple linear equivalent design method for braced buildings implementing this innovative technology is proposed and validated through comparison with non-linear time history analyses. The procedure is then exploited to design the seismic-retrofit intervention of a real case-study hospital and the enhanced seismic performances, compared to those offered by conventional BHDs, are quantified.

A Novel Dynamic Detection Method of Impact Factor Considering Deterioration of Pavement Roughness

Abstract The influence mechanism between the impact factor of bridge and pavement roughness was analyzed and a novel bridge dynamic detection method was presented in this article. Based on the vehicle-bridge vibration theory, the effect of both the spatial and frequency domain characters of pavement roughness on the impact factor were analyzed. Then, derived from the probability distribution model of the impact factor data, a new index for the dynamic increment that was excited by the pavement roughness was introduced. The new index can indicate the impact factors caused by the pavement roughness of different Power Spectral Density grades with selected assurance factors. Lastly, together with the new index, a novel dynamic detection method, which was developed from the obstacle moving truck testing method, was proposed. With a new equivalent design method, the dynamic increment excited by the artificial obstacles could be set similar to that which was caused by different degrees of pavement deterioration. The future dynamic response of the bridge could be predicted.

Equivalent design of stiffened panel bvased on load characteristics

In order to use a cheaper and homogeneous steel plate to replace the real stiffened panel in warhead tests, we numerically simulated and analyzed the deformation and failure characteristics of the stiffened panel as well as the force characteristics of the projectile in the warhead-target interaction. Based on the energy equivalence method, we first used the acceleration curve of the warhead in actual target penetration process as the reference for equivalent design and replaced it using a three-layered homogeneous steel plate. To visually assess their equivalence, we introduced Pearson correlation coefficient in statistical analysis to reflect their correlation. The results showed that the equivalent design method based on load characteristics make both consistent not only in the kinetic energy loss but also in the warhead’s target-piercing acceleration process, thus realizing the equivalence from process to final state.

Experimental and computational verification of reasonable design formulae for base‐isolated structures

AbstractIt is clear that base isolation is a sensible strategic design in attenuating the responses of a structural system induced by ground motions. The design of seismically isolated structures is mainly governed by the Uniform Building Code (UBC) published by the International Conference of Building Officials. The UBC code emphasizes a simple, statically equivalent design method that displacements of an isolated structure are concentrated at the isolation level. Therefore, the superstructure nearly moves as a rigid body and the design forces of elements above isolators are based on the behaviour of isolators at the design displacement. However, in the UBC code, the distribution of inertial (or lateral) forces over the height of the superstructure above isolation has been found to be too conservative for most isolated structures. In view of this, two simple and reasonable design formulae for the lateral force distribution on isolated structures have been proposed in this paper. Results obtained from a full‐scale isolated structure tested on the shaking table and numerical analyses of two additional examples verify the suitability of design formulae. It is illustrated that the proposed formulae can predict well the lateral force distribution on isolated structures during earthquakes. Copyright © 2003 John Wiley & Sons, Ltd.