Wall Loading Research Articles

Quasi-static compression response of the origami thin-walled structure

In this paper, a novel metamaterial fabricated by origami methods is proposed. The quasi-static compression tests and numerical simulations are carried out to explore its deformation mechanisms and energy absorption performances. The numerical results agree well with the experimental results. The effects of the geometrical parameters and load conditions including the wall thickness, load velocity, opening radius and fold number on the energy absorption capacity and crush response are discussed. Finally, the sequential response surface method (SRSM) is applied to solve a structural optimization problem and find the optimal design. Results show that the deformation modes with bending and unfolding of the unit cells contribute to energy dissipation. Increasing the wall thickness and load velocity can raise the specific energy absorption (SEA) and the initial peak crushing force (PCF) level substantially. Introducing the horizontal opening, the SEA and mean crushing force (MCF) level can be enhanced, while the SEA and MCF level are decreased when the openings are introduced in the vertical direction or both horizontal and vertical directions. The structures which increase fold numbers in the two orthogonal directions exhibit better energy absorption and impact resistance capacities. Based on the surrogate optimization, the SEA level of the structure is increased by 10.04% compared with the original design.

Simulation of radio-frequency heating and fast-ion generation in Wendelstein 7-X

The next scientific operation phase of Wendelstein 7-X (W7-X) is scheduled to begin in late autumn of 2022 and will, for the first time, include experiments in which the ICRH (ion-cyclotron-resonance heating) antenna will be used.In addition to heating the plasma, this system will generate fast ions and thus offers a new way to assess fast-ion confinement in a stellarator such as W7-X. The first plasmas that will be used for the upcoming ICRH operation will be Helium-4 plasmas with a small Hydrogen minority on the order of about 10%. In tokamaks such plasmas typically offer good power absorption and are thus considered a safe way for gaining first experiences with the new antenna in W7-X.This assessment is confirmed by the SCENIC simulations carried out in this contribution that use profiles foreseen for the upcoming campaign as input. The simulations are carried out in the standard configuration of W7-X in low-beta (0.3% ≲ 〈β〉 ≲ 1%) plasmas. However, also scans over minority concentration and background-plasma density are performed. We find that the power absorbed by the Hydrogen minority directly from the radio-frequency wave is typically (provided that the minority concentration is not too high) on the order of about 90% with the rest going to the electrons. Very little power goes to the Helium-4 ions. Under the present simulation conditions only fast-ion energies up to about E ≈ 50 keV can be reached.Combining SCENIC and ASCOT simulations enables us to track lost particles through the scrape-off-layer to the 3D wall of W7-X and to compute wall loads caused by ICRH. The results show that the wall loads that can be expected from ICRH under the first operating conditions are benign.

Behaviour of masonry lateral loaded walls made with sediment-based bricks from the Usumacinta river (Mexico)

A feasibility study on Usumacinta River sediment-based bricks for resilient housing adapted to both climate change and seismic risks is performed on laterally loaded reduced-scale walls. Mortar formulations with different volume ratios of lime and sand (2/1, 1/2, 1/4, 1/6) are prepared while different types of sediment-based bricks are thoroughly investigated, manufactured and strength characterized. Commercial fired bricks as reference bricks completed the set of bricks tested (FRS: Fired River Sediment-based brick (at 850 °C); LRS: Lime treated River Sediment-based unfired brick (1.5% of lime addition); NRS: Natural fiber Reinforced river Sediment-based unfired brick and FR: commercial Fired Reference brick made without sediment). Walls of different sizes were built with these types of bricks and mortars. Tests under lateral in-plane loads of walls i.e. pushover tests , were conducted. The most significant results are as follows:(1) the addition of lime increases the strength of the mortar; (2) the wall size effect is observed for wall built with reference bricks (FR) and mortar ratio (1/2), where, large walls (LW), intermediate walls (IW) and small walls (SW) exhibiting maximum load of about 1200 N, 440 N and 260 N respectively. Rocking failure mode is the most observed unlike shear and sliding mode which are rarer. (3) maximum load measured during a pushover test performed on walls with sediment-based bricks provides a satisfactory average of 130 N, which exceeds the strength recommended for light buildings; The failure mode is sliding for fired bricks and rocking for unfired bricks. (4) the sediment-based bricks walls give an interesting ductility to pushover test while (2.6–40). These results show promising perspectives on the possibility of using the Usumacinta River sediment-based bricks in walls for light constructions under seismic loading. • The use of Usumacinta River sediment-based bricks is suitable in light buildings (80). • Fired, unfired: lime treated and fibered sediment-based bricks are used for wall tests (86). • The sediment-based brick wall gives satisfactory pushover resistance (68). • The ductility of the walls demonstrates significant seismic resistance (69).

Effect of the Size of Multiple Perforations on the Performance of Long Reinforced Concrete Shear Walls

This paper investigates the effect of the size of multiple openings on the behavior of shear walls. In this study, the wall span is 24 m, the wall depth is 4 m, and is 0.3 m thick. The work involves the discussion of the three main kinematic and strength indicators that influence the shear wall performance. They are the load displacement relationship for the wall top edge, the equivalent concrete stress flow within the body of the wall, and the bending stress gradient at the bottom of the wall. The wall is constructed of reinforced concrete. A nonlinear finite element push over analysis has been carried out using Ansys software. The element Solid65 presented by Ansys effectively simulates the true behavior of concrete. The steel reinforcement has been modeled by link180 element. Primarily a finite element model for the solid bearing RC shear wall has been constructed and analyzed. The primary step has involved calibration and validation of the finite element model. Thereafter, pushover analysis has been performed for four perforated walls of various opening sizes. The study has indicated that when the percentage of the sum of the perforations’ areas to the total wall area surpasses 8.35%, the shear wall load carrying capacity starts to degrade. When the percentage of the sum of perforations surpasses 16.7% of the total wall area, the shear wall behavior starts to convert to that of two coupled shear walls. The larger the opening size is, the higher the stresses are, and the less the wall load carrying capacity is. When the percentage of the sum of the perforations’ areas to the wall total area surpasses 25%, the behavior of the shear wall converts to that of a frame. The study recommends that further future studies should be carried out on the effect of providing CFRP sheets on the edges of the openings, especially at lower stories in order to control concrete cracks at the edges of the perforations resulting from the developed large concrete equivalent stresses.

Cyclic Behavior of Multiple Hardening Precast Concrete Shear Walls

Precast Concrete (PC) shear walls are becoming popular in building structures. With “wet” connection techniques, PC shear walls often behave like conventional cast-in-place walls, where hardening occurs after yielding. In this study, two PC shear walls assembled by the “dry” connection technique, and one cast-in-place shear wall, were tested by means of quasi-static cyclic loading. The main purpose of the experiment was to systematically investigate the cyclic response of PC shear walls with varying types of vertical connection in the form of a friction-bearing device. The results showed that vertical bearing in devices, which mainly stems from the longitudinal elongation of PC wall panels, could enlarge the axial force of end column so that it provided an additional resistance moment. The PC shear wall with weak connection achieved ductile failure and second ascending branches on load-displacement relationship, i.e., secondary hardening, and the wall with strong vertical connection performed great moment capacity as well as tertiary hardening. Compared to cast-in-place walls, the peak load and cumulative hysteretic energy of PC shear walls increased by about 60% and 100%, respectively. A conceptual analysis of the multiple hardening phenomenon is presented based on experimental results.

Identification of fast ion wall loads in Wendelstein 7-X from thermographic measurements

Fast ion wall loads can result in excessively high heat fluxes to the plasma-facing components (PFCs). To allow for the development of mitigation strategies, and thereby protect the PFCs, the fast ion losses have to be predicted by faithful models. To ensure that fast ion models are an accurate representation of the real world, they need to be verified. The neutral-beam experiments performed in Wendelstein 7-X (W7-X) allow to investigate and verify models of the fast ion losses in the stellarator configuration. Infrared thermographic measurements were used to obtain the heat flux to both the baffle plates and the divertor. We found evidence of fast ion wall loads on the baffle plates, with loads between 100 kW m−2 and 1 MW m−2. The loads are attributed to fast ions which escape the main plasma via magnetic ripples. The fast ion wall loads on the baffle plates show up-down and toroidal asymmetry. The experimental results were compared to numerical simulations performed by the BEAMS3D and ASCOT codes. Qualitative agreement in up-down asymmetry is found, but the magnitude and toroidal asymmetry are not yet well predicted by the simulations. The asymmetries of the strike lines on the divertor suggest that fast ions also play a role here. Specifically, a second strike line emerged consistently in the high-iota configuration on the horizontal divertor. The shape and magnitude of the strike lines changed considerably during the neutral-beam injection (NBI) operation phase. Although no damage to steel components of W7-X was found, fast ion loads to the baffle plates could possibly limit the NBI operation in the upcoming campaigns of W7-X.

Comparison of the simulated seismic behavior of small- and large-scale cripple walls: PEER-CEA Project test programs

As part of the Pacific Earthquake Engineering Research Center (PEER)-California Earthquake Authority (CEA) project, experimental programs were performed at UC San Diego and UC Berkeley, with the former focusing on small-component testing and the latter focusing on large-component testing. During the small-component testing program, a suite of 28 cripple wall-only specimens was tested under quasi-static reverse cyclic lateral loading with variations in exterior finishes, retrofit condition, cripple wall height, anchorage condition, boundary conditions, vertical load, and loading protocol. In the large-component testing program, cripple wall-first story specimens, load path connections, and combined materials in occupied stories were tested. The more easily performed small-component specimens facilitate comparison with the large-component specimens to allow the assessment of their potential to emulate large-scale specimen behavior, with a particular interest in cross-comparing their global hysteresis and physical damage evolution. This cross-comparison among small- and large-scale specimen test results is intended to offer best practices for the future design of cripple wall seismic retrofits in residential housing, with a particular interest in: (1) supporting the realistic design of small-component specimens that may capture the response of large-component specimens and (2) to qualitatively determine where the small-component tests fall in the range of lower- to upper-bound estimation of strength and deformation capacity for the purposes of numerical modeling. Data from both test programs were utilized in the PEER-CEA project to assist with validating numerical modeling tools, which in turn were used to generate seismic loss models capable of quantifying the reduction of loss achieved by applying state-of-practice retrofit methods as identified in FEMA P-1100 Vulnerability-Base Seismic Assessment and Retrofit of One- and Two-Family Dwellings. The objective of this article is to present an overview of the small- and large-component testing programs and key results pertaining to exterior finishes, boundary conditions, the FEMA P-1100 retrofit, and cripple wall height.

Seismic Performance and Vibration Control of Rapid Construction Environmental Protection Wall Based on Artificial Intelligence

With the continuous increase in building types, people's demand for buildings is increasing. In addition to focusing on the work of the building itself, high requirements are also placed on the safety, stability, and durability of the building. Especially in other earthquake-prone areas, it is even more necessary to strengthen seismic isolation research to reduce vibration. Rapid construction of environmental protection walls pays attention to environmental protection and efficiency during construction, which can effectively solve problems in the construction process, but the seismic resistance of rapid construction environmental protection walls is unknown. Therefore, this paper used artificial intelligence technology to study the seismic performance of rapid construction environmental protection walls and analyzed its vibration control. This paper firstly established the seismic performance analysis model of the environmental protection wall, used the finite element method to construct the environmental protection wall model, and then used the artificial intelligence algorithm to analyze the seismic performance of the rapid construction environmental protection wall. The experimental results showed that the peak load of the rapid construction environmental protection wall was about 250 KN, and the seismic performance was good.

Chest wall loading during supine and prone position in patients with COVID-19 ARDS: effects on respiratory mechanics and gas exchange

BackgroundRecent reports of patients with severe, late-stage COVID-19 ARDS with reduced respiratory system compliance described paradoxical decreases in plateau pressure and increases in respiratory system compliance in response to anterior chest wall loading. We aimed to assess the effect of chest wall loading during supine and prone position in ill patients with COVID-19-related ARDS and to investigate the effect of a low or normal baseline respiratory system compliance on the findings.MethodsThis is a single-center, prospective, cohort study in the intensive care unit of a COVID-19 referral center. Consecutive mechanically ventilated, critically ill patients with COVID-19-related ARDS were enrolled and classified as higher (≥ 40 ml/cmH2O) or lower respiratory system compliance (< 40 ml/cmH2O). The study included four steps, each lasting 6 h: Step 1, supine position, Step 2, 10-kg continuous chest wall compression (supine + weight), Step 3, prone position, Step 4, 10-kg continuous chest wall compression (prone + weight). The mechanical properties of the respiratory system, gas exchange and alveolar dead space were measured at the end of each step.ResultsTotally, 40 patients were enrolled. In the whole cohort, neither oxygenation nor respiratory system compliance changed between supine and supine + weight; both increased during prone positioning and were unaffected by chest wall loading in the prone position. Alveolar dead space was unchanged during all the steps. In 16 patients with reduced compliance, PaO2/FiO2 significantly increased from supine to supine + weight and further with prone and prone + weight (107 ± 15.4 vs. 120 ± 18.5 vs. 146 ± 27.0 vs. 159 ± 30.4, respectively; p < 0.001); alveolar dead space decreased from both supine and prone position after chest wall loading, and respiratory system compliance significantly increased from supine to supine + weight and from prone to prone + weight (23.9 ± 3.5 vs. 30.9 ± 5.7 and 31.1 ± 5.7 vs. 37.8 ± 8.7 ml/cmH2O, p < 0.001). The improvement was higher the lower the baseline compliance.ConclusionsUnlike prone positioning, chest wall loading had no effects on respiratory system compliance, gas exchange or alveolar dead space in an unselected cohort of critically ill patients with C-ARDS. Only patients with a low respiratory system compliance experienced an improvement, with a higher response the lower the baseline compliance.

Analysis of Retaining Walls Subjected to Concentrated Loads

Structural analysis of reinforced concrete retaining walls is commonly performed on a two-dimensional model. This approach is suitable only when the applied loads are evenly distributed over the wall length. In cases of concentrated loads (e.g. vehicle impact), two-dimensional modelling brings highly distorted results in comparison to the more realistic three-dimensional modelling. This article presents a study on how wall height and load position affect the result distortion, comparing the outcomes of two-and three-dimensional modelling. The peak value of bending moment was chosen to be the parameter used for the comparison. The error due to the use of two-dimensional model for concentrated loads was quantified. The conclusion of the study is a proposal of correction coefficients that can be applied to the results of two-dimensional analysis, in order to acquire results of equal precision as these from three-dimensional analysis.

Design and simulation investigations of a high gain millimeter wave gyro-twystron amplifier

In this paper, the design and multimode analysis of a single cavity Ka-band gyro-twystron have been presented. The present amplifier has been studied for its beam-wave interaction by using a nonlinear multimode analysis, which has also been verified with a 3D Particle-In-Cell (PIC) simulation. A single anode magnetron injection gun (MIG) has been designed with a ∼4% velocity spread using electron optics code. The PIC simulation of the current amplifier predicted an RF output power of ∼240 kW in TE01 mode at 35 GHz. The power gain, electronic efficiency, and 3-dB bandwidth were calculated as ∼53 dB, ∼37%, and ∼2 GHz, respectively, using the electron beam of 65 kV, 10 A with the velocity ratio of 1.4. Also, a collector is designed with a heat wall loading 0.116 kW/cm2 for the proposed design.

Numerical Limit Analysis of the Stability of Reinforced Retaining Walls with the Strength Reduction Method

The failure mechanism of MSE (mechanically stabilized earth) walls was studied via numerical analysis with the finite element strength reduction method, which was verified as an effective technique by simulating the experimental results reported in previous papers. The finite element program was applied to explore the effects of reinforcement, geometry, and seismic parameters on failure mechanism control at the design stage of MSE walls to avoid the unavoidable errors experienced in common numerical analysis caused by the assumptions of the failure mode and complex input parameters. The research parameters included the wall height, length, and spacing of the geogrid-reinforced retaining wall and seismic load. The results indicated that the wall height and reinforcement length play a major role in failure mode change. When the reinforcement length is less than 2 m, overturning failure could occur, which was unrelated to the other parameters in all cases studied in this paper. In this paper, the parametric study results were presented by evaluating the critical reinforcement length, generating the failure surface pattern, and summarizing design recommendation.

Inelastic collision effects of high-energy neutrons in tungsten materials

Because the inelastic impact of high flux, high-energy neutrons on tungsten material in a commercial fusion reactor would drastically decrease the service life and steady-state functioning of the core plasma in the future, it is vital to investigate the damage process. In this paper, a particle sputtering theory approach is used to derive an equation for calculating the sputtering yield of high-energy neutrons by simulating the transport of primary knocked-out atoms (PKA) resulting from inelastic collisions of 14.1 MeV neutrons with tungsten materials at different depth levels, namely Y =∫E0Emaxf(E)*Y(E)dE, where f (E) is the energy probability distribution function of PKA, Y (E) is the sputtering yield at a given energy of PKA particles generated by inelastic scattering collisions, Emax is the maximum kinetic energy of PKA, and E0 is the minimum kinetic energy of PKA (generally taken as 0). According to the result, when the neutron wall load is 1 MW/m2, and the annual average equivalent material wastage is less than 1 nm, sputtering damage to tungsten material can be ignored. However, it must be kept in mind that the reflection of the PKA into the plasma will have an impact on the performance of the plasma confinement system and the damage caused by the PKA's internal energy.

Characterization of beam ion loss in high poloidal beta regime on EAST

A critical issue for achieving the integrated operation of steady-state long-pulse high-confinement (H-mode) plasmas on experimental advanced superconducting tokamak (EAST) is to improve beam ion population confinement during neutral beam injection (NBI). To study the characterization of beam ion loss and improve beam ion confinement, the steady-state long pulse scenario discharges were conducted on EAST (β p ⩾ 2.0, β N ⩾ 1.7, q 95 ⩾ 6.7 and H 98y2 ⩾ 1.1) with NBI heating. Based on neutron yield, the beam voltage and line-averaged electron density were adjusted from 50 kV to 60 kV and 4.4 × 1019 m−3 to 5.0 × 1019 m−3, respectively. The results show that the dominant mechanisms of beam ion loss are shine-through loss, prompt loss, and stochastic ripple loss. The shine-through loss fraction is determined by initial velocity, flight time and entire beam path. The change in prompt loss fraction is caused by the change in the deposition of beam ions. The change in stochastic ripple loss fraction is caused by the change in the initial fraction of trapped-confined ions. Detailed physics shows that the prompt loss fraction during counter-Ip injections (∼45%) is far larger than during co-Ip injections (∼5%) due to the finite orbit width. The lost ions are mainly deposited on the lower divertor or below the midplane since the direction of magnetic drift is vertical down. The orbit types of prompt loss during counter-Ip injections are mainly trapped-lost and ctr-passing lost. To minimize the prompt loss fraction during counter-Ip injections, a reversed Ip configuration (rev-Ip) discharge #94758 was conducted. The result suggests that the beam ion wall load fraction during counter-Ip tangential injection (∼3%) is far lower than that in normal Ip configuration (nor-Ip) discharge #94820. It is also found that the confinement of beam ion population in the counter-Ip injection #94758 was greatly improved when compared to #94820. This study can provide unique support for the improvement of beam ion population confinement and for the performance evaluation of the NBI system on EAST and future tokamaks.

3D finite-element brain modeling of lateral ventricular wall loading to rationalize periventricular white matter hyperintensity locations

Aging-related periventricular white matter hyperintensities (pvWMHs) are a common observation in medical images of the aging brain. The underlying tissue damage is part of the complex pathophysiology associated with age-related microstructural changes and cognitive decline. PvWMH formation is linked to blood–brain barrier dysfunction from cerebral small vessel disease as well as the accumulation of cerebrospinal fluid in periventricular tissue due to progressive denudation of the ventricular wall. In need of a unifying theory for pvWMH etiology, image-based finite-element modeling is used to demonstrate that ventricular expansion from age-related cerebral atrophy and hemodynamic loading leads to maximum mechanical loading of the ventricular wall in the same locations that show pvWMHs. Ventricular inflation, induced via pressurization of the ventricular wall, creates significant ventricular wall stretch and stress on the ependymal cells lining the wall, that are linked to cerebrospinal fluid leaking from the lateral ventricles into periventricular white matter tissue. Eight anatomically accurate 3D brain models of cognitively healthy subjects with a wide range of ventricular shapes are created. For all models, our simulations show that mechanomarkers of mechanical wall loading are consistently highest in pvWMHs locations (p < 0.05). Maximum principal strain, the ependymal cell thinning ratio, and wall curvature are on average 14%, 8%, and 24% higher in pvWMH regions compared to the remaining ventricular wall, respectively. Computational modeling provides a powerful framework to systematically study pvWMH formation and growth with the goal to develop pharmacological interventions in the future.

A new empirical formulation for the out-of-plane resistance of masonry infills in reinforced concrete frames

The paper presents a new empirical expression estimating the out-of-plane (OOP) resistance of infilled reinforced concrete frames subject to horizontal forces. The new model is calibrated through an optimization process based on a hybrid dataset, including experimental data from real tests and from numerical simulations obtained from a refined FE micro-model realized in Abaqus®. The new expression considers the effect of vertical loads and also introduces a conversion factor to uniformize point-load and uniform load out-of-plane tests. The final expression is also flexible with respect to available data on the infill material properties, as it is specialized in two versions, one providing the conventional compressive strength of the units, the other providing the conventional compressive strength of masonry as possible inputs. Results presented in the paper will show a noticeable accuracy of the proposed model in estimating the ultimate out-of-plane load of a masonry infill wall, with respect to available models. The formula provides the reference undamaged OOP resistance and can be easily combined with available strength-reduction functions to consider the effect of prior in-plane loading.

Paradoxical response to chest wall loading predicts a favorable mechanical response to reduction in tidal volume or PEEP

BackgroundChest wall loading has been shown to paradoxically improve respiratory system compliance (CRS) in patients with moderate to severe acute respiratory distress syndrome (ARDS). The most likely, albeit unconfirmed, mechanism is relief of end-tidal overdistension in ‘baby lungs’ of low-capacity. The purpose of this study was to define how small changes of tidal volume (VT) and positive end-expiratory pressure (PEEP) affect CRS (and its associated airway pressures) in patients with ARDS who demonstrate a paradoxical response to chest wall loading. We hypothesized that small reductions of VT or PEEP would alleviate overdistension and favorably affect CRS and conversely, that small increases of VT or PEEP would worsen CRS.MethodsProspective, multi-center physiologic study of seventeen patients with moderate to severe ARDS who demonstrated paradoxical responses to chest wall loading. All patients received mechanical ventilation in volume control mode and were passively ventilated. Airway pressures were measured before and after decreasing/increasing VT by 1 ml/kg predicted body weight and decreasing/increasing PEEP by 2.5 cmH2O.ResultsDecreasing either VT or PEEP improved CRS in all patients. Driving pressure (DP) decreased by a mean of 4.9 cmH2O (supine) and by 4.3 cmH2O (prone) after decreasing VT, and by a mean of 2.9 cmH2O (supine) and 2.2 cmH2O (prone) after decreasing PEEP. CRS increased by a mean of 3.1 ml/cmH2O (supine) and by 2.5 ml/cmH2O (prone) after decreasing VT. CRS increased by a mean of 5.2 ml/cmH2O (supine) and 3.6 ml/cmH2O (prone) after decreasing PEEP (P < 0.01 for all). Small increments of either VT or PEEP worsened CRS in the majority of patients.ConclusionPatients with a paradoxical response to chest wall loading demonstrate uniform improvement in both DP and CRS following a reduction in either VT or PEEP, findings in keeping with prior evidence suggesting its presence is a sign of end-tidal overdistension. The presence of ‘paradox’ should prompt re-evaluation of modifiable determinants of end-tidal overdistension, including VT, PEEP, and body position.

Crashworthiness of foam filled truncated conical sandwich shells with corrugated cores

Polymeric foam filled truncated metallic conical sandwich shells with corrugated cores were proposed, and their energy absorption characteristics under axial compression were systematically investigated. The types of foam filling include: (i) foam filling inner cavity (FFIC), (ii) foam filling corrugated channel (FFCC), and (iii) foam filling inner cavity and corrugated channel (FFICCC). Test specimens were fabricated by combining the step-by-step molding method with the method of in-situ foam filling. Firstly, the crashworthiness of FFIC, FFCC and FFICCC subjected to axial compression was experimentally characterized. Secondly, numerical simulations with the method of finite elements (FE) were performed, with good agreement achieved between measurements and simulations. Subsequently, based upon the validated FE models, interaction mechanisms between foam filler and metallic shell were explored, and the influences of wall thickness, semi-apical angle and loading speed on energy absorption were quantified. The three different foam filled structures were found to exhibit higher energy absorption than their unfilled counterpart. Particularly, the specific energy absorption (SEA) of the FFCC was higher than that of the unfilled structure, attributed mainly to the participation of all foam fillers in the interaction with metal shells that was rarely found in other types of foam-filled structure.

COMPARATIVE STUDY OF MODIFIED CONSTRUCTION STAGE ANALYSIS AND CONSTRUCTION STAGE ANALYSIS FOR RC BUILDINGS

A significant difference is found in axial shortening of vertical members in tall concrete buildings when analyzed by Construction Stage Analysis considering the effect of creep and shrinkage as compared to the conventional One Step Analysis method. In Construction Stage Analysis the self-weight of structural members, and a load of brick walls along with floor finishing load, gets added sequentially as construction is carried out. In addition to the above loads, construction loads such as the weight of formwork, the weight of wet concrete, staking of materials, and other construction loads of men and machines get imposed on the structure during construction. Also, stagewise reduction of load due to removal of formwork, material staking, and other construction loads of men and machines should also be considered during the analysis with the Construction stage method. The axial shortening of vertical members of RC buildings was analyzed by the Conventional one-step method, Construction Stage method, considering self-weight along with brick wall and floor finishing load as sequential loads. Modified Construction Stage method-in which in addition to self-weight, brick wall, and floor finishing load, above mentioned all loads that appear during construction, were added, and removed sequentially in the analysis, by taking 20,30, and 40 floor RC building models. Modified CSA gives 2.068% to 20.56% lesser axial shortening in comparison to the CSA method. The study also concludes that the difference of axial shortening between Modified CSA &amp; CSA increases from first to a certain floor, after that it reduces till top floor.

Parametric analysis on performances of the pipe-encapsulated PCM (PenPCM) wall system coupled with gravity heat-pipe and nocturnal radiant cooler

To face the climate change and carbon neutrality, reductions of energy-uses and carbon emissions are imminent. Pipe-encapsulated phase change material (PenPCM) wall is a novel envelope system with renewable energy utilizations in buildings. It combines the PCMs, nocturnal radiant cooler and gravity heat-pipe with the wall to achieve the automatic heat insulation and removal without the mechanical energy. Parameters may have influences on system performances and the parametric analysis is understudied. In this study, the influences of parameters including phase-change temperature, PCM thickness, pipe-spacings, cooler areas and orientations are investigated. The system applicability for different climate regions is also studied. Results show that, when the phase-change temperature is 27–29 °C, the ratio of the cooling load reduction to the cooling load of the conventional wall reaches largest with 17.4%. Appropriately increasing the PCM quantity can improve the thermal-storage capacity and decrease the wall temperature fluctuation. Enlarging the cooler area can increase the energy-saving effect of the PenPCM wall system. For different climate regions, the PenPCM wall system is applicable. Compared with conventional wall, the ratio of the cooling load reduction from June to September can reach 11.7%, 16.1%, 21.1%, 28.6%, 44.2% respectively for Hong Kong, Wuhan, Beijing, Harbin and Kunming.