Unequal Depth Research Articles

Seismic behavior of steel frames with H-shaped damper

This paper investigates the effect of dampers on the seismic performance of steel frames with unequal depth beam-column (UDBC) joints. First of all, the finite element (FE) models of the UDBC joint and steel frame were regenerated by ABAQUS and verified by experimental results. Secondly, the design method for three H-shaped dampers with different web perforation forms (vertical, elliptical, and diamond) was provided. Finally, five steel frames were built using ABAQUS, and pushover analysis and dynamic time-history analysis were performed on them. The results indicated that dampers could decrease the maximum vertex displacement and inter-story shift angle of steel frames with UDBC joints under three seismic waves by 4.47% to 17.17% and 7.71% to 23.88%. The effect of H-shaped dampers was similar to that of T-shaped connectors. Under the action of the Kobe wave and the Qian'an wave, the H-shaped damper exhibited more excellent seismic performance. Compared with frames with T-shaped connectors, the maximum vertex displacement and the maximum inter-story shift angle of frames with H-shaped dampers decreased by 3.44% to 12.39% and 9.55% to 16.15%. The web perforation form of H-shaped dampers somewhat affected the seismic behavior of steel frame structures. Among them, diamond dampers could minimize structural deformation.

Asymmetric Graph Contrastive Learning

Learning effective graph representations in an unsupervised manner is a popular research topic in graph data analysis. Recently, contrastive learning has shown its success in unsupervised graph representation learning. However, how to avoid collapsing solutions for contrastive learning methods remains a critical challenge. In this paper, a simple method is proposed to solve this problem for graph representation learning, which is different from existing commonly used techniques (such as negative samples or predictor network). The proposed model mainly relies on an asymmetric design that consists of two graph neural networks (GNNs) with unequal depth layers to learn node representations from two augmented views and defines contrastive loss only based on positive sample pairs. The simple method has lower computational and memory complexity than existing methods. Furthermore, a theoretical analysis proves that the asymmetric design avoids collapsing solutions when training together with a stop-gradient operation. Our method is compared to nine state-of-the-art methods on six real-world datasets to demonstrate its validity and superiority. The ablation experiments further validated the essential role of the asymmetric architecture.

Continuous Wavelet Transformation to Quantify small-scale Cycles of Petrophysical Properties; a New Approach Applied in a Potential Disposal Repository of Nuclear Waste, SW Hungary

Continuous Wavelet Transformation (CWT) was applied to study the small-scale repetitive oscillations of porosity distribution patterns in a 5 m silty-claystone core sample of the Boda Claystone Formation. We handled the fluctuations in voxel porosity averages over unequal depth distributions as signals over uneven time intervals. The strength of wavelet analysis lies in the ability to study the fluctuation of a signal in detail, i.e., the wavelet transforms permit automatic localization of the cyclic attributes' sequences both in time (the depth domain) and according to their frequency (the frequency domain). Thereupon, three main frequency branches (cycles) were discerned: small scale (5, 6.67, and 11 cm), intermediate scale (20, 30 cm), and large scale (66.67 cm). Depending on the CWT coefficients magnitude plot, we were able to detect the developments of porosity oscillation according to the depth variable. Thus, small-scale cycles were seen throughout the core sample., the intermediate-scale cycles were strong in the upper parts of the core sample and dwindled toward greater depths, and the large cycle was predominant in the lower part of the core sample. The cross-correlation of the wavelet coefficients of porosity and rock-forming components allows a detailed study of the inter-dependence of such parameters as their relationship changes over time. The distinct peaks at zero lag indicates that the measured wavelet coefficient series were contemporaneously correlated; their strong positive correlations suggest that both examined series respond similarly and simultaneously to other exogenous factors. The results emphasize that cyclical porosity fluctuations at all scales would concern three main factors; sediment deposition, diagenetic processes, and structural deformation (i.e., convolute laminations).

Influence of staggered floor and unequal height of left and right beam on seismic behavior of CFSST column-to-HSS beam composite frames

One-third scale models of three concrete-filled square steel tubular (CFSST) column-to-H-shaped steel (HSS) beam composite frames with two bays and three stories were designed and manufactured. A failure test of the specimens under lateral cyclic loading was conducted. The experimental parameters included a staggered floor ratio and unequal depth ratio, staggered floor ratios of 0 and 0.5, and unequal height ratios of 0 and 0.75. The skeleton curves, hysteresis curves, and the stiffness and strength degradation of the CFSST column-to-HSS beam composite frame were analyzed. The results showed that the test frames exhibited excellent seismic performance, and the order is KJ-1, KJ-2 and KJ-3. The drift ratio ranges of δy, δm, δu were 1/123-1/191, 1/37-1/38, and 1/27-1/29, respectively, indicating that the three test frames possessed sufficient ductility and met the seismic objective of not collapsing in large earthquakes. The equivalent viscous damping coefficients of the specimens in the failure stage were in the range of 0.24–0.18, meeting the earthquake protection requirements. A simulation model have developed to predict the P-Δ response envelope. The model results were consistent with the test results.

Parametric study and design method on unequal depth beams to corner column joints with H-damper

The paper presents the parametric studies and design method of unequal depth H beams-HSS steel column corner joints with H-dampers. According to corresponding experimental studies, nineteen numerical models were created by ABAQUS and their reliability was validated by comparative tests. The design methods and corresponding calculation of H-dampers with three perforated shapes (diamond, ellipse, and vertical) are exhibited. The primary analyzed variables were beam depth ratio (Dbs/Dbw), H-damper types, limb breadth (B), and limb length (lf) of H-dampers. Then, the bearing capacities and initial stiffness of beams and bearing capacities and energy dissipation in H-dampers were studied through parametric analysis. The results indicated that T-connectors and H-dampers could elevate the bearing capacity and initial stiffness of shallow beams. H-dampers exhibited better energy dissipation performance. Besides, web-perforated forms of dampers affected the beams and dampers. Wider limb breadth and shorter limb length enhanced the bearing capacity and initial stiffness of beams, and reduced energy dissipation of H-dampers.

Rossby waves and dipole blocking of barotropic-baroclinic coherent structures in unequal depth two-layer fluids

In this paper, coupled Kadomtsev-Petviashvili (KP) equations describing Rossby waves in barotropic-baroclinic coherent structures are derived from the two-layer quasi-geostrophic vortex equations using multi-scale analysis. The soliton solutions of the coupled KP equations are obtained by applying the elliptic function expansion method. On this basis, the structural distribution and climatic effects of dipole blocking are discussed. The results show that increasing the meridional wave number tilts the symmetric structure of the dipole in the east-west direction, and the dipole structure affects the airflow in the blocked region. In addition, stability conditions for the coupled KP equations are given.

Variations of aerosol and cloud vertical characteristics based on aircraft measurements in upstream of Shanghai during the 2020 China international import expo

Vertical information about aerosols and clouds is vital to understanding aerosol transport, aerosol-cloud interactions, and pollution-weather-climate feedback so as to reduce uncertainties in estimating their climatic effects. The combination of sounding, lidar, aircraft, and satellite measurements is widely used to obtain the vertical information of aerosols and clouds. We used an aircraft measurement over southern Anhui, the upstream regions of Shanghai, on 1 November which conducted to ensure good air quality for the Third China International Import Expo to examine the vertical characteristics of aerosol and cloud microphysical properties and their variations before and after cloud seeding. Observations showed aerosols and clouds were vertically stratified. Most aerosols trapped within the boundary layer are small particles with sizes less than 0.12 µm. Aerosol number concentrations (Na) generally decreased with altitude in the cloudless atmosphere, with the largest particles occurring in 2500–3500 m due to dust transported from distant regions and high ambient humidity. Four separate cloud layers with unequal depths dominated by altostratus and nimbostratus appeared at different heights. The maximum cloud droplet concentration (Nc) and the minimum cloud droplet diameter (Dc) that appeared in the mid-level cloud (2246–2482 m) were 107.7 cm−3 and 4.03 μm, respectively, owing to the high proportion of hygroscopic particles. Hygroscopic particles played an important role in the growth of droplets and the activation of cloud condensation nuclei, especially under high ambient humidity. Cloud droplet size spectrum showed a unimodal distribution with a single peak at 5 µm in low- (970–1000 m) and mid-level clouds, but a trimodal distribution with peaks at 7 μm, 12 μm, and 17 μm in the mid-high- and high-level clouds, indicating the broadening of spectra with increasing altitude. An artificial seeding experiment was conducted in the high-level clouds. Big cloud droplets and ice crystals increased significantly after cloud seeding. Meanwhile, cloud particle populations showed less Nc, larger Dc, and a wider size spectrum. Our results suggest that the artificial precipitation experiment promoted rainfall to a certain extent and contributed to the removal of pollutants from upstream regions, which is beneficial to the air quality of Shanghai.

Paediatric Partial-Thickness Burn Therapy: A Meta-Analysis and Systematic Review of Randomised Controlled Trials.

Background: Paediatric second-degree burn injuries are a significant source of medical challenges to the population that may cause severe, lifelong complications. Currently, there are dozens of therapeutic modalities and we aimed to summarise their reported outcomes and determine their effectiveness, compared to the widely used silver sulphadiazine (SSD). Methods: We conducted the meta-analysis and systematic review of randomised controlled trials (RCTs), which investigated the performance of dressings in acute paediatric partial-thickness burns. The evaluated endpoints were time until wound closure, grafting and infection rate, number of dressing changes and length of hospitalisation. Results: Twenty-nine RCTs were included in the qualitative and 25 in the quantitative synthesis, but only three trials compared SSD directly to the same intervention (Biobrane). Data analysis showed a tendency for faster healing times and a reduced complication rate linked to biosynthetic, silver foam and amnion membrane dressings. A substantial difference was found between the number of dressing changes associated with less pain, narcosis and treatment duration. Conclusions: Considerable between-study heterogeneity was caused by the unequal depth subcategory ratio and surface area of the injuries; therefore, no significant difference was found in the main outcomes. Further research is necessary to establish the most effective treatment for these burns.

Unequal depth beam-column joints with H-shaped damper: Parametric study and design method

This paper proposes new types of unequal depth beam-column (UDBC) steel joints with H-shaped damper. The seismic energy was dissipated through the elastoplastic deformation of H-shaped steel dampers. Based on the experimental results, detailed three-dimensional finite element models were built to identify the response of UDBC joints under cyclic loadings. Three types of H-shaped dampers (vertical damper, elliptical damper, and diamond damper) were designed. Then, the shear capacity of the unequal-depth panel zones and the energy dissipation capacity of H-shaped damper were studied by the parametric analysis. The result showed that H-shaped dampers could improve the shear strength and deformation of the panel zone significantly. Moreover, web perforated forms influenced the performance of the H-shaped damper. With the increasing of limb width or decreasing of limb height, the shear strength and shear deformation of the panel zone increased, and cumulative energy dissipation of dampers decreased.

Coherent structures of nonlinear barotropic-baroclinic interaction in unequal depth two-layer model

The nonlinear barotropic-baroclinic interaction theory is of great importance for the understanding of the atmosphere and the oceans. In this paper, a mathematical model based on analytical methods is established to discuss the propagation of the coherent structure of the nonlinear barotropic-baroclinic interaction of two-layer fluids in geophysics. It is the first time that the coupled Boussinesq equations are derived by using perturbation and spatiotemporal extensions transformations to simulate the evolutions of nonlinear barotropic and baroclinic waves. The solitary wave solutions are analytically obtained to explain the excitation, propagation and decrease of the coherent structures. The physical mechanism of the nonlinear wave-wave coherent structures is discussed by considering the effects of different physical factors, such as the topography, the Earth’s rotation and the basic shear flow. It is found that both topography and beta parameter have essential effects on the evolutions of the coherent structures. Furthermore, the effect of the unequal-depth parameter on the propagation of coherent structures is discussed.

Research on shear strength of CFSST column and H-section with beam composite joint of unequal depth

Four concrete-filled square steel tube (CFSST) columns and H-sections with beam composite joints of unequal depth were designed based on existing specifications and manufactured at ⅓ scale. A failure test of the specimens was carried out under lateral cyclic loading. Different height ratios between the left and right beam, ζ, (ζ = 0.52, 0.39, 0.26, 0.13) were tested to analyze the failure mode, hysteresis characteristics, ductility, strain, and deformation of the specimens and the damage characteristics of the structure. An equation was established to determine the shear bearing capacity of the CFSST column and H-section. The results show that shear failure in the joint core area is the dominant failure mode of the specimen. The greater the beam ratio, the smaller the yield displacement of the specimen is, and the earlier the joint core area reaches the yield strain. The damage value obtained from Chen's model is in good agreement with that obtained from the test and accurately describes the damage evolution and damage limit of the specimen from “basically intact” to “completely damaged”. The shear resistance of the joint core area is primarily borne by the steel tube web, the main concrete compression strut in the core area, and the restrained compression strut. The theoretical values and the experimental values of the shear bearing capacity of the CFSST column and H-section are in good agreement, demonstrating the accuracy of the proposed theoretical equation.

Morphological evolution of bifurcations in tide-influenced deltas

Abstract. In river-dominated deltas, bifurcations often develop an asymmetrical morphology; i.e. one of the downstream channels silts up, while the other becomes the dominant one. In tide-influenced systems, bifurcations are thought to be less asymmetric and both downstream channels of the bifurcation remain open. The main aim of this study is to understand how tides influence the morphological development of bifurcations. By using a depth-averaged (2DH, two-dimensional horizontal) morphodynamic model (Delft3D), we simulated the morphological development of tide-influenced bifurcations on millennial timescales. The schematized bifurcation consists of an upstream channel forced by river discharge and two downstream channels forced by tides. Two different cases were examined. In the first case, the downstream channels started with unequal depth or length but had equal tidal forcing, while in the second case the morphology was initially symmetric but the downstream channels were forced with unequal tides. Furthermore, we studied the sensitivity of results to the relative role of river flow and tides. We find that with increasing influence of tides over river, the morphology of the downstream channels becomes less asymmetric. Increasing tidal influence can be achieved by either reduced river flow with respect to the tidal flow or by asymmetrical tidal forcing of the downstream channels. The main reason for this behaviour is that tidal flows tend to be less unequal than river flows when geometry is asymmetric. For increasing tidal influence, this causes less asymmetric sediment mobility and therefore transport in both downstream channels. Furthermore, our results show that bedload tends to divide less asymmetrically compared to suspended load and confirm the stabilizing effect of lateral bed slopes on morphological evolution as was also found in previous studies. We show that the more tide-dominated systems tend to have a larger ratio of bedload-to-suspended-load transport due to periodic low sediment mobility conditions during a transition between ebb and flood. Our results explain why distributary channel networks on deltas with strong tidal influence are more stable than river-dominated ones.

Experimental and Numerical Assessment of Reinforced Concrete Beams with Disturbed Depth

This paper investigates numerically and experimentally the performance of reinforced concrete (RC) beam with unequal depths subjected to combined bending and shear. Such beams can geometrically be considered for unleveled reinforced concrete (RC) floor slab-beam system. However, it may generate critical disturbances in stress flow at the re-entrant corner (i.e. location of drop in beam depth). This research investigates the use of shear reinforcement and geometric properties to enhance cracking characteristics, yielding, ultimate load-carrying capacity, and exhibiting ductile failure mode. Ten reinforced concrete (RC) beams were constructed and tested experimentally considering the following key parameters: recess length, depth of smaller beam nib, and amount and layout of shear reinforcement at re-entrant corner. Finite element analysis (FEA) with material non-linearity was conducted in two RC beams that were tested experimentally to validate the computer modelling. The FEA models were then extended to conduct a parametric study to investigate the influence of geometric parameters (beam shape and width) and amount and arrangement of shear reinforcement on the structural response. Results confirmed that geometric properties and ratio of shear reinforcement at the re-entrant region significantly affect the behavior of reinforced concrete beam with unequal depths in terms of first cracking, yielding level, ultimate load carrying capacity and mode of failure.

Distribution characteristics of circular grounding ground potential in HVDC transmission system

This paper presents a model of double-ring type grounding pole unequal depth embedding for high-voltage direct current (HVDC) transmission system; and introduces calculation formula of DC ground potential distribution when double-ring type grounding pole is unequal buried. Furthermore the ground potential distribution and stride voltage level around the grounding pole and influence of grounding depth and soil parameters on the current field are discussed in this paper. The electric field zoning model of the ring current source is established by using the power system grounding pole analysis software CDEGS to verify the feasibility of this method. As the model is able to make the grounding current overflow density and potential distribution as uniform as possible, there is no serious local current concentration.

Effect of channel tributaries on the evolution of submarine channel confluences (Espírito Santo Basin, SE Brazil)

AbstractConfluences are geomorphologic features fed by distinct channel tributaries that record the contribution of multiple sediment sources. They are key features of both fluvial and submarine channels in geomorphologic and sedimentologic terms. Here, we use high-quality three-dimensional seismic data from SE Brazil to document the response of a submarine channel confluence to turbidity currents originating from a tributary. The studied channel system consists of a west tributary, an east tributary, and a postconfluence channel, with the last two comprising the main channel at present. Downstream from the confluence, changes in planform morphology and architecture were found due to the effect of turbidity currents sourced from the west tributary channel. A channel bend in the main channel curved toward the west when it was first formed but later curved toward the east, and so remains until the present day. This process led to the migration of the confluence point ∼500 m to the east, and changed the bed morphology from discordant (where the beds of tributaries and main channels meet at an unequal depth) to concordant (where the beds of tributaries and main channels meet at approximately the same depth). In addition to the channel bend near the confluence, two other bends further downstream recorded significant changes with time, increasing channel sinuosity from 1.11 to 1.72. These three channel bends near the confluence accumulated a large volume of sediment at their inner banks, generating depositional bars. Multiple channel forms within the depositional bars indicate the occurrence of large-scale lateral migration near the confluence. Hence, turbidity currents from the west tributary are shown to influence the submarine channel by promoting lateral channel migration, confluence migration, increases in channel sinuosity, and the formation of large depositional bars. These variations near the confluence reveal a change in tributary activity and a shift in sediment sources from east to west on the continental shelf. Such a shift suggests variations in sedimentary processes on the continental shelf probably due to avulsions on Doce River Delta.

Characteristics of convergence zone formed by bottom reflection in deep water

There appears a convergence effect on the sound filed under the condition of sound channel in the deep sea due to the refraction effect of the sea water. For the deep water environment with an incomplete channel, sea bottom has an important influence on sound propagation. A long-range sound propagation experiment was conducted in the South China Sea in April 2018. Hyperbolic frequency modulated (HFM) signals with a frequency band of 250-350 Hz are transmitted by an acoustic source which is towed at a speed of 4 knots away from a vertical line array (VLA). The VLA consists of 20 hydrophones which are arranged from 85 m to 3400 m with an unequal depth space. Using the data collected in the experiment, the effects of bathymetry variation on sound propagation are studied. The physical causes of the seafloor reflection convergence phenomenon are explained by using the parabolic equation combined with ray theory. The observed phenomenon is different from the convergence phenomenon in the typical deep water environment, the spatial variation of bathymetry contributes to the formation of the seafloor reflection convergence zone in advance, and the sound intensity in part of shadow zone is significantly increased. Due to the reflection from the seabed, two obvious seafloor reflection convergence zones are observed near the range of 20 km and 40 km respectively, in which both gains increase up to 10 dB, and a high sound intensity area is formed in the shadow zone near the range of 11 km, where the gain is less than the gains in the two convergence zones. In addition, the grazing angle of the sound ray reaching the second convergence zone is smaller than that reaching the first convergence zone when the receiving depth is the same as the source depth, and the rays with smaller glancing angle have less reflection loss, which leads to a higher gain in the second convergence zone. As the water depth becomes gradually shallower with range increasing, the convergence zone near the range of 51 km under the SOFAR channel is destroyed, and the sound field energy in the corresponding range is much smaller since the number of arriving refracted sound rays is reduced. In the first convergence zone, the path of arriving rays is gradually increased as the receiver becomes deeper. Therefore, the arrival structure tends to be complicated, and the multi-path effect is more obvious. The study result is meaningful for the performance analysis of sonar in complex deep water environment.

Shear Behavior of Panel Zones in Steel Beam-to-Column Connections with Unequal Depth of Outer Annular Stiffener

AbstractThis paper presents an experimental investigation of the shear behavior of steel beam-to-column connections with unequal depth of outer annular stiffener. The depth-to-thickness ratio (D∶t)...

Seismic demand assessment of code-designed continuity plate in panel zone

This study investigated the seismic demand of continuity plates (CP) in Special Moment Frames (SMFs), including built-up I-shape beams. Six reference experiments for SMF connections were considered, including beams with unequal depths on both sides of the column, to compare the seismic demand for CP with the corresponding value of the AISC code formula. The effects of beam shape properties, connection type, shear strain of the panel zone (PZ), different construction detailing and straight/inclined CP in dual/trapezoidal PZ were included in this study. In addition, companion analytical studies were performed to evaluate CP seismic demand. The results of the experiments and numerical analyses showed that the AISC code underestimates seismic demand for CP in joints with beams having sizes outside the geometries of hot-rolled structural sections. Poor seismic performance of the code-designed CP led to premature yielding and out-of-plane local buckling of CP, which were observed in the reference experiments and confirmed by numerical models. Finally, an equation for CP seismic demand was developed based on findings of this research. It was demonstrated that the proposed seismic demand met the required seismic criteria using this equation, and it also kept CP within the safe structural margins.

03.28: Performance of cruciform finite elements that model 2D steel joints with beams of unequal depth in frame analysis

ABSTRACTThis paper deals with the performance evaluation of cruciform finite elements with 4 nodes and 12 degrees of freedom that model 2D steel joints with beams of unequal depth in frame analysis. These elements are capable of modelling joints that have double rectangular panels, with or without horizontal stiffeners in the panel zone, due to beams of different depths at both sides of the joint. In addition, these cruciform elements are suitable for simple, rigid and semi‐rigid connections and therefore can be used for the global analysis of semi‐rigid steel frames. The performance of these elements is assessed by analysing steel frames under different loading conditions, and comparing the results with complete finite element models.The characteristics of these elements (stiffness and resistance) are generated by a previously proposed displacement based modal approach. All the forces and moments coming from the adjacent beams and columns concur at the joint, therefore, the complete force field in the panel zones is known with no need for a transformation parameter β (EC3‐Part 1.8). The proposed element also avoid the use of mechanical models (composed of springs and rigid bars) for frame analyses, which add complexity, numerical overhead —consequence of the larger number of degrees of freedom— and possible round off errors (due to the rigid bars) in the solution process.In addition, since the real dimensions of the joint are included in the proposed elements, the eccentric moments are automatically taken into account. Also, the interaction between the deep and the shallow sides of the column double panels are considered. Numerical simulations and comparison with complete finite element models are carried out that show the validity and computational efficiency of these elements.

Design methodology for inclined continuity plate of panel zone

This research aims to estimate the ultimate capacity and seismic demand of inclined continuity plate (ICP) connected to beams with unequal depths which are utilized in special moment resisting frames (SMRFs). Considering architectural issues, mostly two adjacent bays with different lengths are exerted in a structural framing, thus two beams with unequal depths are applied and lower ICP can be used to connect the bottom flanges of deep and shallow beams. Design method of ICP has not been addressed yet in structural design codes. Two full scale experiments were tested under standard cyclic loading, and more than 38 validated companion numerical analyses were performed in order to evaluate the seismic behavior of ICP. Furthermore, based on the experimental evidences, an analytical equation was developed for ICP capacity using plastic yield line mechanism theory. With regards to the consistent experimental, numerical and analytical results, a design methodology for ICP was verified. The results implied that current seismic provisions for straight continuity plates (CPs) cannot provide satisfactory criteria for designing ICP due to out of plane buckling behavior of ICP. The proposed closed-form equation could predict the ICP capacity with maximum error bounds less than 21% and the proposed design methodology could assure the acceptable seismic behavior of panel zone (PZ) with ICP.