Ring Beam Research Articles

Implementation of Livable House Standards for Earthquake Resistance in Bandung Regency

The BSPS (Bantuan Stimulan Perumahan Swadaya) program organized by the Directorate General of Housing of the Ministry of Public Works and Public Housing is a program implemented as a form of improving the quality of self-help housing. Although simple, building like this requires sufficient resistance to earthquakes. The results of the calculation of earthquake resistance that begins with loading the roof obtained a live load of 1.38 N, a super dead load of 0.75 N, and a dead load of 132102.5 N. Further testing on the calculation of ring beams results in ring beams being able to withstand a load of 1 .7191 kN with the help of the column interaction diagram states that the column is able to withstand a load of 252.6964 kN. The results of the ground spectrum response test show that Bandung district has a high earthquake risk and a class II risk period. Static power testing in the x and y directions is 270 kg and 260 kg. the level deviation on the x-axis is 0.0706500 mm and on the y-axis is 0.05575000 mm. This has proven the house to be resistant to earthquakes. Subsequent work can be in accordance with the standards given during the construction process. This building is resistant to earthquakes but the work requires more careful supervision.

Numerical simulation and theoretical analysis on RECC ring beam joints for RECC-encased CFST composite columns

The failure mechanisms of reinforced engineered cementitious composite (RECC) ring beam joints were numerically analysed using finite element (FE) software of ATENA. The failure mode, load-carrying capacity, ductility, and distribution of the strain in the steel reinforcement were comprehensively investigated. The simulation results showed that the RECC ring beam significantly contributed to the mechanical property of the joint. Part of the circumferential reinforcement in the ring beam contributed to the shear strength and improved the strength of the core ECC by the restraint effect. A total of 46 specimens were subsequently investigated to examine the influences of the circumferential reinforcement ratio, stirrup ratio, axial compressive ratio, tensile properties and compressive strength of ECC on the seismic behaviour of RECC ring beam joints. Finally, a simplified softened strut-and-tie model was proposed to predict the shear-carrying capacity of the RECC ring beam joint.

A RETROFIT SOLUTION FOR UNCODED STEEL RAFTER TO CONCRETE RING BEAM CONNECTIONS

Some building contractors in the Caribbean have been constructing non-coded steel rafter to concrete ring beam connections on low budget residential buildings. These connections may resist failure under normal loading conditions, but critical connections fail under moderate to high loads resulting in partial or full dislodgement of the roof. In this study, the performance of non-coded steel rafter to concrete ring beam designs were analyzed in a finite element program and a retrofit solution for the failed uncoded connections were designed and modeled. Nine versions of the connection were identified and consisted of several variations including mechanically anchoring the rebar to the rafter without welds, using one and two rebars, varying the rebar embedment depth and using 90 degree hooks and straight rebars. A standard, code-compliant, bolted-endplate connection was used as the control for the investigation. The connections were analyzed in “ABAQUS” with a bond slip and damage plasticity model. The maximum load resistances were compared with category 1 hurricane loads for the region. The load capacities of all the connections were found to be lower than the control connection but were still adequate for hurricane category 1 loads, with the exception of the connection in which the rebars were mechanically anchored to the rafter without welds. Connections with welds to the top flange of the rafter were less stiff, experienced larger rafter displacements, inflicted less damage on the concrete ring beam, and required less rebar embedment to prevent pull out failure than the connections to the bottom flange.

A simple and fast approach for computing the fusion reactivities with arbitrary ion velocity distributions

Calculating fusion reactivity involves a complex six-dimensional integral of the fusion cross section and ion velocity distributions of two reactants. We demonstrate a simple Monte Carlo approach that efficiently computes this integral for arbitrary ion velocity distributions with a time complexity of O(N), where N is the number of samples. This approach generates random numbers that satisfy the reactant velocity distributions. In cases where these numbers are not readily available, we propose using Gaussian random numbers with weighted factors. For cases where only a small number of N samples are available, a O(N2) method can be used. We benchmarked this approach against analytical results for drift bi-Maxwellian distributions and provided examples of drift ring beam and slowing down distributions. Our results show that the error can be less than 1% with N∼104 samples for our standard approach.

Seismic performance of confined prestressed hollow core wall panels Part I: Experiment

Concrete prefabrication techniques have been popularized and utilized in building construction industry for years. To further improve the construction efficiency and quality for low-rise buildings, a confined prestressed hollow core wall system is proposed. The new system employs the standardized prestressed hollow cores that are commonly used for floors to be vertical structural elements to resist gravity and lateral loads. The panels are confined by a precast constructional frame that is composed of precast concrete ring beams and tie columns to improve its ductility and strength. A series of experimental tests were conducted to study the axial and in-plane/out-of-plane lateral behaviors of the new proposed system. The test included 19 specimens with various parameters of geometric properties, prestressing forces and binding details between panels and constructional frames. The experimental results showed that prestressed hollow core walls experienced shear-flexural behaviors at small lateral drifts and were controlled by a braced-frame deformation mode at large drifts with opening and splitting of horizontal and vertical joints between panels and frames. The confining frames were able to significantly increase the structural ductility, prevent hollow core units from collapse as well as maintain a considerable post-cracking load bearing capacity. The ultimate lateral drift of prestressed hollow core walls generally exceeded 1%–2%, and thus the structural system was preliminarily proved feasible for engineering practice. Numerical simulation and analysis of the proposed system is discussed in Part II of this study.

Out-of-Plane Dynamical Strength of Masonry Walls Under Seismic Actions

ABSTRACT The dynamic analysis of the out-of-plane response of masonry walls, with different reinforcing systems and hit by sequences of pulses alternating in sign, representative of the seismic action, is the aim of the paper. The analysis is done in the context of the Heyman model of the no tension masonry structures. We consider the wall of the last story of a simple masonry house, commonly reinforced at its head by a ring beam, usually in a reinforced concrete. It has also been considered the retrofitting of the wall by applying, on both its sides, vertical bands in FRP, or similar. The dynamics of the wall, activated by sequences of pulses, is analyzed in detail, considering the change of geometry occurring in the mechanism during the motion. The corresponding differential equation is integrated in a closed form. It is shown that, under the alternating sequence of shocks, the dynamical collapse of the wall takes place immediately after the occurrence of an accumulation of out-of-plane deformation of the wall that drags it into the configuration of zero strength, where any resistance, due to the weight, has been lost. The collapse takes place right after when the subsequent incoming pulse pushes the wall to go further beyond this configuration. The check of the seismic safety of the masonry wall concludes the paper. The smallest limit static strength of the wall required in order the wall, having pulsation p, could be able to sustain, at the limit of the dynamical collapse, the action of the asymptotic pulse sequence with acceleration intensity PGA and specific duration p T E /2 of the expected earthquake. It is shown that the wall, reinforced by a top ring beam, with the addition of vertical bands of glass or similar, of suitable length, pasted with lime mortar, can reach the required level of seismic safety.

Programmable Cone Shell Configuration Based Depth-Sensitive Fluorescence Spectroscopy With Flexible Target Depth and Depth Sensitivity

Depthsensitivefluorescencespectroscopycanextract the depth dependent distribution of fluorophores, which is closely associated with disease progresses in layered tissues. However, the conventional contact fiber-optic probe or non-contact lens setup based fluorescence measurements often suffer from insufficient depth sensitivity for precise diagnosis. Although a modified non-contactlenssetup, usingaxiconlensinsteadof conventional convex lens, has successfully achieved improved depth sensitivity by forming a cone-shell configuration, challenges remain in incompletely flexible target depth and limited depth sensitivity. In this study, a programmable cone shell configuration based depth-sensitive fluorescence spectroscopy was proposed and tested on a two-layered agar phantom. According to the experimental results, the target depth can be altered arbitrarily by digitally tuning the ring beam radius, even switching between two distant target depths. In addition to better depth sensitivity than conventional methods, its capability of flexibly narrowing the ring beam width can promote further improvement on depth sensitivity. Various aspects can benefit from its capabilities of flexibly switching among different target depths and depth sensitivities, thus the proposed programmable cone shell configuration based depth-sensitive fluorescence spectroscopy is expected to promote its wider applications in biomedicine.

A numerical insight into the reliability of seismic strength models for masonry piers and spandrels

With the aim to provide an insight on the effectiveness of existing formulae for the flexural and shear strength of masonry piers and spandrels, this paper reports and compares results obtained from pushover analyses performed on a set of plane masonry walls. As reference, the formulae provided by the Italian Building Code (IBC) were considered. Nonetheless, the formulations provided by IBC are similar to the ones reported in the Eurocode Standards (ES), and thus conclusions of this paper can be extended to the latter. Three types of masonry walls were considered which differ in the span-to-height ratio b/h of the masonry beams, namely: a) slender beams (b/h = 2.0); b) intermediate beams (b/h = 1.00) and c) short beams (b/h = 0.75). For each masonry wall, the unreinforced configuration (URS) was compared with two resisting schemes: concrete ring beams (RSB) and steel chains (RSC). Therefore, a total of 9 types of masonry walls were considered which differ in terms of geometry and resistance mechanisms. To perform the pushover analyses, the finite element technique was employed by using three different load distributions. The results expressed in terms of inner forces on the piers and spandrels were subsequently compared with the formulae for flexural and shear strength provided by IBC. The comparisons showed that the reliability of these equations is at least questionable, especially for the prediction of the spandrels’ strength. In this case, the strength models provided by the Standards underestimate by a large amount the real strength both for the unreinforced and the strengthened walls, especially in the case of slender spandrels in strengthened walls.

Local dynamic behavior of dark beams in self-defocusing Kerr media

We study the local dynamic behavior of dark beams in self-defocusing Kerr media. In this, we are encouraged by the interesting results obtained in Refs. [1,2], although these papers are concerned with the bright beams in self-focusing Kerr media. Similar to these papers, we are interested in the two-dimensional (2D) necklace ring beams, but under certain circumstances. Different from these papers, we are interested in the dark necklace beams in self-defocusing media. When the dimensionless ring radius L is far greater than the ring thickness w, the 2D defocusing nonlinear Schrödinger equation in cylindrical coordinates can be simplified to the standard 1D defocused nonlinear Schrödinger (NLS) equation. Then, an approximate solution of the 1D NLS equation can be constructed by different means, for example by a simple combination of exponential and trigonometric functions. In general, such a necklace solution can be described by two parameters: the ring radius L and the topological charge m. Hence, we study the local dynamic behavior of dark beams with different topological charges m and different ring radii L when they are much larger that the ring thickness w. Different spatial distributions of dark beams are obtained for m zero, positive integer, and half-integer. We use direct numerical simulation to confirm the validity of our analytical approximate solution. Our results show that the structure of dark beams can be well controlled by adjusting the ring radius and the topological charge. Our procedure provides a new method for dealing with high-dimensional nonlinear equations of different origin.

Behavior of reinforced concrete ring beams strengthened with sustainable materials

Reinforced Concrete Ring Beams (RCRBs) have been used in Reinforced Concrete (RC) buildings, tanks, and roof shell structures, such as domes and cones. The curviness feature of RCRBs may result in excessive tensile stresses that may consequently generate critical cracks in concrete, particularly when the beams are constructed with Normal Concrete (NC). This paper presents experimental and numerical investigations on the structural behavior of RCRBs strengthened with sustainable materials. The experimental results on 12 RCRBs constructed with various types of concrete and strengthened with several techniques are presented and discussed. The specimens were made of NC, Engineered Cementitious Composite (ECC), High Strength Concrete (HSC), and High Strength Fiber Reinforced Concrete (HSFRC). Three strengthening techniques were employed for strengthening, including the External Bonded Reinforcement (EBR) with stainless-steel plates (SSPs), the Near Surface Mounted (NSM) with steel bars, and the pre-stressing system. Three-dimensional Finite Element Models (FEMs) were developed by using ABAQUS software to simulate the nonlinear performance of RCRBs. The test results show that the use of sustainable materials in RCRBs can remarkably improve the strength and ductility of RCRBs. In addition, the strengthening techniques are effective in enhancing the responses of RCRBs against the applied loads. Moreover, the thickness and configuration of SSPs significantly affect the ultimate and energy absorption capacities of RCRBs. Finally, a good agreement is observed between numerical predictions and experimental results, suggesting that the finite element model can be employed for further investigations.

Local Generation of Magnetosonic Waves by Ring Beam Hot Protons in the Martian Ionosphere

AbstractMagnetosonic (MS) waves are dominant plasma waves causing severe Martian ionospheric erosion. They are generally considered to originate upstream of Martian bow shock with frequencies near the upstream proton gyrofrequency. However, whether MS waves can be locally excited lacks theoretical analysis. Here we present an event of MS waves with frequencies above and closely related to the local proton gyrofrequency in the Martian ionosphere. Concurrently, ring beam hot proton distributions are observed due to the penetration of magnetosheath protons. By employing the observed plasma and magnetic field data, the calculated linear growth rates for MS waves agree well with the observed wave power spectra, demonstrating that they can be locally excited by unstable ring beam hot protons at Mars. Our results could be of great help in understanding the excitation of MS waves in a heavy ion‐rich environment around unmagnetized planets.

Analytical and experimental study on honeycomb sandwich plates reinforced by ring beam of satellites

The equivalent parameters of hexagon aluminum honeycombs are work out with the theories of sandwich plates in this paper. The honeycomb sandwich plate reinforced by ring beam applied with static load is simulated by the finite element model of honeycomb sandwich plates, which is validated by static test. The research results show that the numerical calculation error of the honeycomb sandwich plate is less than 10% compared with test results, which is acceptable for an engineering project, and the mechanical behavior of the honeycomb sandwich plate can be described in detail. Thus, the method of equivalent honeycomb parameter is proved to be effective for the design and analysis of honeycomb sandwich plates. The influence of equivalent elasticity modulus and equivalent shear modulus to honeycomb sandwich plates can be reflected exactly from the results which are figured out with the equivalent theories of sandwich plates. The assembly clearance and assembly accuracy have a significant influence to the test results of honeycomb sandwich plates, which is obvious especially at a lower load level.

Force-Displacement Hysteresis Model of Exterior PCRB Joints under Low Cyclic Loading.

The seismic behaviors of exterior polyvinyl chloride-carbon-fiber-reinforced polymer (PVC-CFRP) confined concrete (PCCC) column-ring-beam joints (hereafter referred to as exterior PCRB joints) under low cyclic loading were investigated. A total of 11 specimens were tested to analyze the effects of the structural parameters (i.e., the reinforcement ratio of the ring beam, the CFRP-strip spacing, the ring-beam width, the reinforcement ratio of the frame beam, and the axial compression ratio) on the failure modes and hysteretic behavior. Three different failure modes, including the failure of the frame beam, the failure of the junction between the frame beam and the ring beam, and the shear failure of the ring-beam joint, were observed. The experimental results showed that the pinching effects of the hysteresis curves decreased and that the slope of the descending stage of the skeleton curves gradually decreased with the enhancement of the reinforcement ratio of the ring beam, axial compression ratio, and ring-beam width. The effects of the CFRP-strip spacing and the reinforcement ratio of the frame beam on the hysteresis loops and skeleton curves were marginal, while the reinforcement ratio of the frame beam exerted significant effects on the failure modes. Therefore, a model for predicting the skeleton curves of exterior PCRB joints and hysteresis rules was proposed, based on the softening constitutive relation of the concrete and a regression analysis of the test data. Ultimately, a load-displacement hysteresis model of the exterior PCRB joints was established and validated by the test data, with good agreement.

Shell folded footings using different angles and EPS cavity filling: experimental study

Shell folded footings have drawn the interest of researchers for decades as an alternative to typical flat isolated footings because folded footings can reduce the needed amount of reinforced concrete in addition to enhancing the overall geotechnical performance of the supporting soil medium. The main setback of utilizing such folded footings is the relatively complex geometry of the bottom cavity, which requires proper compaction of the soil used to fill that cavity. Current geosynthetic materials such as geofoam or expanded polystyrene (EPS) proved efficiency in many geotechnical applications, where EPS was adopted herein as a cavity-filling material for folded footings. EPS and footing concrete properties were determined using the ultrasonic test device, such as modulus of elasticity and damping coefficient. The main aim of this study was to experimentally assess the behavior of folded footings with and without EPS filling using seven fully instrumented footing models with folding angles ranging from 0° to 45°. Reinforcement was placed in the footing models and limited along the perimeter to act as a hidden ring beam. The models were load tested inside a sandbox to measure internal stresses induced in the soil and the overall settlement. Results showed a significant enhancement in the soil behavior after using EPS. Modification factors were developed for the standard bearing capacity and settlement equations to account for the folding angle and EPS filling effects.

Multistage Positron Acceleration by an Electron Beam-Driven Strong Terahertz Radiation

Laser–plasma accelerators (LPAs) have been demonstrated as one of the candidates for traditional accelerators and have attracted increasing attention due to their compact size, high acceleration gradients, low cost, etc. However, LPAs for positrons still face many challenges, such as the beam divergence controlling, large energy spread, and complicated plasma backgrounds. Here, we propose a possible multistage positron acceleration scheme for high energy positron beam acceleration and propagation. It is driven by the strong coherent THz radiation generated when an injected electron ring beam passes through one or more solid targets. Multidimensional particle-in-cell simulations demonstrated that each acceleration stage is able to provide nearly 200 MeV energy gain for the positrons. Meanwhile, the positron beam energy spread can be controlled within 2%, and the beam emittance can be maintained during the beam acceleration and propagation. This may attract one’s interests in potential experiments on both large laser facilities and a traditional accelerator together with a laser system.

Quality characteristics and analysis of input parameters on laser beam welding of hairpin windings in electric drives

The relevance of electric drives in individual mobility is continuously increasing. This requires the use of new manufacturing processes in automotive production. In modern stators, the so-called hairpin winding is used. The production process entails rectangular copper conductors (hairpin) to be contacted by laser beam welding. To avoid temperature peaks due to resistance heating in the current-carrying wire, a high cross-sectional area in the welding seam is required. Therefore, the pore volume must be considered. This is proven by thermographic investigations of electrically stressed hairpin connections. To optimize the welding process, effects of the previous manufacturing steps and the welding parameters themselves must be taken into account. This paper analyses systematically the impact of all translational and rotational deviations on the corresponding welding quality. The tests are performed by using a disk laser. A laser spot with a focus diameter of 170 μm is compared to a statically shaped beam, capable of distributing power in core and ring beam. As an additional parameter, the influence of oxygen content in the copper wire is investigated by using electrolytic tough pitch copper (Cu-ETP) and oxygen-free copper (Cu-OF). Furthermore, the interaction between an additional cutting step before contacting and the welding path is considered. X-ray computed tomography (CT) is used to analyse the welding quality. The main finding of the studies is the significant influence of the gap and height offset between the wire ends on the resulting cross-sectional area. In addition, a low oxygen content of the copper and the use of static beam shaping reduce weld spatters, porosity and increase process stability. Three geometries in the welding path perform better in gap bridging and cause less spatters.

All-fiber cascaded combiners for high-power adjustable-ring mode laser beam with a flattop central beam

An all-fiber structure that obtains an adjustable-ring mode (ARM) beam with a uniformly distributed central beam is put forward for the first time based on the beam combining technology. This structure is all-fiber cascaded combiners consisting of a 3 × 1 combiner and a (6 + 1) × 1 combiner in series. A multi-mode fiber with core diameter of 50 µm acts as the connective fiber, transmitting the combined laser of the first 3 × 1 combiner into the center guide core of the output fiber by the well-designed (6 + 1) × 1 combiner. Through the independent transmission of the center and ring beams, an 8.8 kW uniformly distributed central output laser with a transmission efficiency of 96.2 % and M2 of 5.24 is obtained by the cascaded combiners. The feasibility of ARM laser beam with a 10 kW-level flattop central beam provides a new approach for high-power laser welding.

Light Source Optimization of 3D Inner Contour Measurement System Based on Ring Beam Method

Ring beam method is a simple and efficient method for measuring three-dimensional internal contour. The whole three-dimensional inner contour is stitched from the contour lines of cross-sectional images collected during scanning. The contour image with uniform and moderate light intensity and fine ring band is beneficial to the calculation of contour line extraction algorithm. In practice, due to the quality of the ring beam and the modulation effect of the sample surface microstructure, the light band of the contour image has local widening, overexposure and speckle phenomena, which directly affect the contour extraction effect. The ring beam generation system is optimized here, which makes the whole system have better size adaptability and convenient adjustment. In addition, experiments results show that the measurement repeatability of the cross-sectional profile obtained after the light source optimization has been effectively improved.

Seismic Retrofitting of Mid-Rise Unreinforced Masonry Residential Buildings after the 2010 Kraljevo, Serbia Earthquake: A Case Study

There is a significant building stock of post-WWII low- and mid-rise unreinforced masonry (URM) buildings in Serbia and the region (former Yugoslavia). Numerous buildings of this typology collapsed due to the devastating 1963 Skopje, Yugoslavia earthquake, causing fatalities, injuries, and property losses, as well as experienced damage in a few recent earthquakes in the region, including the 2010 Kraljevo, Serbia earthquake (MW 5.5) and the 2020 Petrinja, Croatia earthquake (M 6.4). These buildings are three- to five-stories high, have clay brick masonry walls, and rigid floor slabs, usually with an RC ring beam at each floor level. This paper presents a case study of a URM building which was damaged due to the 2010 Kraljevo earthquake and subsequently retrofitted. A comparison of seismic analysis results, including the capacity/demand ratio and displacement/drift values, for the original and retrofitted building according to the seismic design and retrofit codes which were followed in Serbia as well as some of the neighboring countries for several decades and Eurocode 8 has been presented. The results of this study show that the selected retrofit solution that satisfied the Yugoslav seismic code requirements is not adequate according to the Eurocode 8, primarily due to significantly higher seismic demand.

Shaking table experimental investigations on dynamic characteristics of CFRP cable dome

Carbon fiber reinforced polymer (CFRP) bars have the feature of lower density, higher strength and better anti-fatigue performance compared with steel bars. Therefore, CFRP is a kind of ideal material for a long-span spatial structure. To explore the dynamic performance of spatial structures and take full advantages of CFRP bars in long span cable dome structures, a CFRP cable dome scale model with a diameter of 5.4 m was designed for a shaking table test. In this model, struts and cables were made of CFRP material except that the internal ring beams were fabricated with steel. In the test, new types of joint forms and anchoring configurations for CFRP cable dome structures were proposed because the existing forms for steel domes cannot be applied to CFRP dome structures. In addition, three kinds of seismic waves including Elcentro wave, Kobe wave and Pasadena wave were selected to generate 12 load cases and the maximum acceleration was 900 Gal. The acceleration and strain response of the model under different types of seismic waves was researched. It is demonstrated that middle-ring upper joints have the largest acceleration response because the control vibration modes of the CFRP cable dome structure are anti-symmetric mode. In addition, a CFRP dome numerical model was established to carry out modal analysis by program ANSYS. By comparing the results of finite element modal analysis with the measured frequencies, the natural vibration modes of the structure are analyzed. Based on the results of seismic wave spectrum analysis and structural modal analysis, the Pasadena wave, which has a wide low frequency region for high Fourier amplitude, can excite the greatest acceleration response.