Core Wall Research Articles

Experimental Investigation of Green Façade Components for Industrial and Storage Buildings

This paper deals with vertical greenery applied on the external side of lightweight walls for industrial and storage buildings. The greenery is expected to have some positive impacts on the building performance, in particular reduction of building energy consumption and peak cooling power. The achievable benefits are however dependent on local climatic conditions, hygro-thermal properties of the building enclosure, the requirements for the indoor environment and on the system of greenery applied on the walls. The side-by-side real-scale experiment involving three different test walls was built in two test windows with dimensions of 3.0 x 3.2 m. A climatic test room with controlled indoor environment is located behind test windows. Two reference walls present current standard technical solutions constructed as metal frame filled with thermal insulation with metal sheets on the exterior side, either in direct contact with core wall or with ventilated air gap. The third wall replaces the external metal sheets by the system of baskets filled by soil substrate and greenery with integrated irrigation pipes. The experiment was built in June 2019 and is extensively monitored since beginning of July 2019. Temperatures, relative humidity, heat fluxes, moisture content of soil substrate, inflow and outflow of irrigation water, and environmental boundary conditions are continuously recorded. Results of the first year of monitoring are presented and discussed in the paper. The measured results showed reduction of daily peak values of heat flux on the internal surface during hot summer days and evaluated power of evaporative cooling.

Preparation and Optimization of Waterborne Acrylic Core Microcapsules for Waterborne Wood Coatings and Comparison with Epoxy Resin Core.

Microcapsules were prepared by in situ polymerization with urea formaldehyde resin as the wall material and Dulux waterborne acrylic acid as the core material. The effects of the core–wall ratio, water bath temperature and depositing time on the morphology, particle size, yield and encapsulation ratio of microcapsules were investigated by orthogonal experiment of three factors and two levels. The results showed that the core–wall ratio had the greatest influence on the performance of microcapsules. When the core–wall ratio was 0.58:1, the water bath temperature was 70 °C, and the depositing time was 5 d, the microcapsule performance was the best. With the increase in depositing time, the yield of microcapsule particles increased gradually, and the microcapsules appeared to show an adhesive phenomenon. However, the long-term depositing time did not lead to complete deposition and agglomeration of microcapsules. When 10.0% concentration of the waterborne acrylic microcapsules with 0.58:1 of core–wall ratio was added to the coatings, the mechanical and optical properties of the coatings did not decrease significantly, but the elongation at break increased significantly. Therefore, this study offers a new prospect for using waterborne acrylic microcapsules to improve the toughness of waterborne paint film which can be cured at room temperature on a wood surface.

Cyclic behavior of c-shaped composite plate shear walls – Concrete filled

A Composite Plate Shear Wall/Concrete Filled (C-PSW/CF) is a special lateral-force resisting system consisting a sandwiched panel of two steel plates with concrete infill in between them, ideally suited for core-wall structures in high-rise construction. The steel plates are connected to each other using tie bars that are embedded in the concrete infill and, in some instances, steel-headed stud anchors. This research project was conducted to investigate the cyclic lateral load behavior of these walls, in terms of strength, and drift capacity. The testing program includes two large-scale C-shaped concrete filled composite plate shear core walls subjected to flexure and axial loads together. Their dimensions were the same, but different axial loads were applied up to 19% of axial loading capacity. The composite behavior and the plastic hinge development were investigated and compared to results from plastic moment calculations. This provides valuable results on the expected behavior of one composite cross-section that is frequently used in full core wall. This is done to support the development of design guidelines for high-rise core-wall steel buildings having C-PSW/CF as the primary lateral force resisting system.

Internal blast resistance of sandwich cylinder with lattice cores

This work focuses on investigation of the internal blast resistance of metal sandwich cylinder with lattice cores. Six types of the geometries designed by the square, hexagonal, semi-re-entrant, re-entrant, sinusoidal and Kagome honeycombs are selected as the cores of sandwich cylinders. Effects of core geometry, core arrangement, core wall thickness, shell mass distribution and cover on blast resistance of sandwich cylinders are explored and identified. Results reveal that both the core geometry and arrangement have significant effects on the blast resistance and deformation mechanism of sandwich cylinders. Thick core wall decreases the energy absorption efficiency of lattice cores. The asymmetrical design of the inner and outer shells enhances the internal blast resistance of the sandwich cylinders. The covers added on the sandwich cylinder result in increasing the deformation degree and energy absorption of sandwich cylinders with various lattice cores.

Impact of bi-directional loading on the seismic performance of C-shaped piers of core walls

Reinforced concrete structural walls are commonly used as the primary lateral load resisting system in modern buildings constructed in high seismic regions. Most walls in high-rise buildings are C-shaped to accommodate elevators or other architectural features. C-shaped walls have complex loading and response including: (1) symmetric response in the direction of the web, (2) asymmetric response in the direction of the flange and (3) high compression and shear demands when used as a pier in a coupled-wall configuration. A research study was conducted on C-shaped walls tested under (1) uni-directional and (2) bi-directional loading of an isolated walls and (3) bi-directional loading of a c-shaped pier in a coupled wall system. Each of the walls failed in flexure with strength loss resulting from low-cycle fatigue of the boundary element longitudinal reinforcement with buckling followed by fracture. The damage progression was as follows: (1) cracking at the wall-foundation interface, (2) concrete spalling in the web, (3) buckling and fracture of web reinforcement, (4) spalling in the flanges, (5) buckling and fracture of the bars in the boundary elements. Concrete spalling and steel bar damage occurred at lower strong-axis drift levels for the bi-directionally loaded, resulting in lower drift capacities for these loading protocols. However, for the strong-axis direction, bi-directional loading does not reduce flexural or shear effective stiffness values suggesting that current values are appropriate for design and evaluation of buildings with c-shaped walls.

Experimental and computational modeling of thermal conductivity of cementitious syntactic foams filled with hollow glass microspheres

Insulating cementitious syntactic foams (CSFs) reinforced hollow glass microspheres (HGMs) have been paid much attention for the growing requirement of energy savings. In this paper, the CSF plates with different volume contents of HGMs are manufactured by a novel three-step manufacturing process and then they are tested by transient plane source (TPS) method to investigate their heat insulation performance. The filler volume content is in the range of 0–56 vol%. The experimental results reveal that the effective value of thermal conductivity of the foam decreases roughly linearly with increasing the HGM volume content. The addition of 56 vol% HGMs brings over 47% decrease of the thermal conductivity of the foam, in contrast to the pure cement material. In addition, the heat transfer mechanisms in the CSFs are further investigated by the developed computational model with randomly dispersed HGMs to approximate the real arrangement of microspheres in the foam. The experimental data are in good agreement with the numerical estimations. Moreover, the resulting numerical predictions demonstrate that the effective thermal conductivity coefficient of the foam increases as the constituent thermal conductivity increases. However, compared to the core and solid wall material, the matrix material gives significant influence to the foam. Finally, a two-phase composite model with equivalent solid spherical inclusion is presented based on Eshelby’s equivalent inclusion theory to indirectly determine the thermal conductivity of pure HGM, which are important for guiding the predesign of syntactic foams with desired low thermal conductivity.

Effect of Microcapsules with Different Core–Wall Ratios on Properties of Waterborne Primer Coating for European Linden

Waterborne acrylic-resin-filled urea–formaldehyde-based microcapsules with core–wall ratios of 0.42:1, 0.50:1, 0.58:1, 0.67:1, 0.75:1, 0.83:1 and 0.92:1 were prepared via in situ polymerization. Microcapsules were added into the primer to investigate the optical and mechanical properties of the coating on European linden. The results indicated that under the condition of the same core–wall ratio, chroma differences increased gradually with increasing concentration. The coating gloss decreased with increasing concentration. The hardness of 10.0–15.0% microcapsules increased more obviously, with the highest elongations at the break of the coating. At the 0.58:1 core–wall ratio and the 10.0% concentration, the coating adhesion was level 1 and the impact resistance was 10.0 kg cm. Microcapsule concentration did not affect the coating’s liquid resistance. The coating with 10.0% microcapsules added at a 0.58:1 core–wall ratio had a better self-healing property, a good stability and aging resistance. This paper lays a technical basis for the manufacturing and utilization of self-healing waterborne wood coatings.

Effect of MF-Coated Epoxy Resin Microcapsules on Properties of Waterborne Wood Coating on Basswood

In this paper, melamine–formaldehyde (MF) was used as the wall material, and epoxy resin was used as the core material to prepare microcapsules. The optical properties, mechanical properties and ageing resistance of waterborne topcoat were investigated by adding different mass fractions of microcapsules into the waterborne topcoat. Through scanning electron microscopy and infrared spectroscopy analysis, the prepared microcapsules of core-wall ratio of 0.50 were more uniform. It was found that when the mass fraction of microcapsules is less than 10.0% and the core–wall ratio is 0.50, the original color difference of the coating can be maintained. With the increase in microcapsule mass fraction, the gloss of the topcoat film gradually decreases. The mass fraction of the microcapsule of 4.0% with the core–wall ratio of 0.50 can maintain the original gloss of 30.0 GU. The topcoat film with the MF-coated epoxy resin microcapsules of the core–wall ratio of 0.50 has high impact resistance, adhesion and hardness. The results showed that the gloss loss and color difference of the coating with the MF-coated epoxy microcapsules were the lowest when the mass fraction of microcapsules was 4.0%, indicating that microcapsules can improve the stability of coating. These results lay a technical foundation for the development and application of high-performance wood coatings.

Seismic performance of concrete core walls reinforced with shape memory alloy bars

Reinforced Concrete (RC) core walls are widely used to resist lateral loads because of their high flexural and torsional stiffnesses. Their seismic performance parameters, including residual displacement, floor acceleration, and residual in-plane rotation, were examined by many researchers. However, reports from previous earthquakes have highlighted the difficulties of repairs addressing their residual displacements and/or rotations. This paper addresses this problem by investigating the influence of self-centering superelastic shape memory alloy (SMA) bars on the seismic performance parameters of RC core walls. A case study building is analyzed, considering both steel and SMA reinforcement, for unidirectional and bidirectional seismic excitations. Different mass eccentricities are assumed. SMA RC core walls are found to have significantly reduced floor accelerations, residual displacements, and residual in-plane rotations as compared to steel RC core walls.

Study on Seepage Characteristics and Stability of Core Dam Under the Combined Action of the Variation of Reservoir Water Level and Rainfall

To study the influence of the variation of reservoir water level and rainfall on the seepage characteristics and stability of the core dam, considering the coupling effect of seepage field and stress field, finite element simulation of seepage and stability of dam slope when the core dam encounters the variation of reservoir water level and rainfall was carried out based on the unsaturated seepage principle, different rainfall intensities, different rainfall types and different variation rates of reservoir water level were selected for finite element simulation. The results show that: The variation rate of water level mainly affects the time when pore water pressure tends to be stable. The rainfall intensity and rainfall type mainly affect the pore water pressure in the upper part of the dam, and the higher the rainfall intensity, the more drastically the pore water pressure changes in the upper area of the core dam. Rainfall type and rainfall intensity are the main factors that affect the safety factor of the downstream slope of the core wall dam, but have little effect on the safety factor of the upstream slope. When the safety factor of the downstream dam slope tends to be stable, the order of the safety factor of different rainfall type is: forward type > = center type > average type > post-peak type. Whether the water level rises or falls, rainfall will reduce the safety factor of downstream dam slope. The results of this study provide a reference for correctly understanding the seepage and stability law of the slope of core dam and a reference for risk analysis and emergency management when the core dam encounters extreme working conditions.

Modulational-instability-free pulse compression in anti-resonant hollow-core photonic crystal fiber.

Gas-filled hollow-core photonic crystal fiber (PCF) is used for efficient nonlinear temporal compression of femtosecond laser pulses, two main schemes being direct soliton-effect self-compression and spectral broadening followed by phase compensation. To obtain stable compressed pulses, it is crucial to avoid decoherence through modulational instability (MI) during spectral broadening. Here, we show that changes in dispersion due to spectral anti-crossings between the fundamental-core mode and core wall resonances in anti-resonant-guiding hollow-core PCF can strongly alter the MI gain spectrum, enabling MI-free pulse compression for optimized fiber designs. The results are important, since MI cannot always be suppressed by pumping in the normal dispersion regime.

Effect of fuel isotope mass on q-profile formation in JET hybrid plasmas

The initial current ramp phase of JET hybrid plasmas is used to optimise the target q-profile for main heating to allow access to high β and avoid MHD instabilities. Mixed protium-deuterium experiments, carried out at JET since the installation of the beryllium-tungsten wall, have shown that the q-profile evolution during this Ohmic phase varies systematically with average main ion isotope mass, indicating the need for re-optimisation for future T and mixed D-T experiments. Current diffusion modelling shows that the key factor was a reduction in electron temperature profile peaking as the hydrogenic isotope mass was increased. This was correlated with an increase in plasma radiation by metallic impurities, consistent with the increased sputtering yield by higher mass isotopes during the current ramp phase. Reduced electron temperature peaking can lead to magnetic shear reversal and the appearance of a 2/1 mode, which can lock, causing the JET massive gas injection system to be triggered to avoid an unmitigated disruption. The potential for a further reduction in electron temperature peaking in T and D-T plasmas could, therefore, result in an increased risk of disruptions. To mitigate this risk, electron temperature peaking measurements have been included in the real-time control system to allow this type of disruption to be avoided by central heating, density increase or early pulse termination. These experiments indicate the need for integrated modelling of impurity behaviour, including the plasma core, scrape-off layer and plasma wall interactions, to predict q-profile evolution in the current ramp phase and anticipate the effects of isotope changes.

A Ring-Shear Radial-Seepage Apparatus for Evaluating the Permeability of Shear Bands in Compacted Clay

Compacted clay cores are extensively used in rockfill dams to cut off water flow because of their low permeability and wide availability. Large differential settlement often occurs at certain locations in a dam, causing large shear concentrations in the compacted clay core in the form of shear bands. This raises concern about the permeability evolution in the shear bands in compacted clay during a large shear process. Thus, a ring-shear radial-seepage apparatus was developed for evaluating the permeability of the shear bands in compacted clay. The apparatus tests hollow cylindrical specimens that are held in a shear box, which consists of an upper box, lower box, and inner chamber. The specimen is compressed in the height direction and sheared in the circumferential direction to form a concentrated shear band. The permeability of the shear band is measured by radial-seepage from the inner side to the outer side of the hollow cylinder. To demonstrate the performance of the apparatus, a series of tests was conducted on compacted specimens of a clay used for the core wall of a high rockfill dam. The test results showed that the change in permeability of the shear bands in compacted clay was dependent on the surcharge pressure. If the current surcharge pressure was far less than the preconsolidation pressure caused by the previous compaction process, the permeability of the shear band might increase significantly. This experimental finding can be useful for identifying high-risk leakage zones in a dam with a compacted clay core.

The effect of core geometry on flexural stiffness and transverse shear rigidity of weight‐wise identical corrugated core sandwich panels reinforced with 3D flat spacer knitted fabric

AbstractThis article aims to evaluate the effect of core geometry on flexural stiffness and transverse shear rigidity of corrugated core sandwich panels both experimentally and numerically. Using vacuum‐assisted resin transfer molding (VARTM) method, three composite sandwich panels reinforced with 3D weft knitted spacer fabric with rectangular, hat‐type (trapezoidal) and triangular cross‐sectional geometries were produced. In order to eliminate weight variation among the produced sandwich panel samples, the unit cell dimensions, core wall to skin angle, and the yarn count used to knit the core wall were carefully chosen. Results pointed to existence of statistically significant difference between the load‐carrying capacity and transverse shear rigidity in the direction of corrugation of the structures. It was concluded that triangular and rectangular structures have the highest and lowest load‐carrying capacity, transverse shear rigidity, and core shear modulus in the direction of corrugation, respectively.

Analysing the cumulative energy demand of external bearing walls

The assessment of environmental properties of buildings is now commonly using a life cycle analysis (LCA). Due to the rapidly evolving construction industry, LCA research is carried out in many areas, from building materials and components to overall building system. Life Cycle Assessment (LCA) is a tool used to compare environmental impacts along the life cycle of products or services. This paper presents an evaluation and comparing of two external bearing walls of different material compositions regarding the materials´ total energy consumption within the cradle to gate boundaries. Impact categories were calculated by the software SimaPro using Cumulative Energy Demand (CED) method and applying the Ecoinvent database. A renewable (biomass, wind, solar, geothermal, water) and non-renewable (fossil, nuclear, biomass) energies were under consideration. The composition with brick as a core wall material achieved worse results in all categories than the wall composition with aerated concrete block.

Discussion on deformation monitoring method of asphalt concrete core wall of high earth-rock dam

The deformation of asphalt concrete core wall of earth rock dam is an important monitoring item of safety management in the construction and operation period of the project. This paper summarizes the conventional monitoring methods and principles of the deformation of asphalt concrete core wall, analyzes the application scope and existing problems of the conventional monitoring methods, and introduces a new method and principle of the deformation monitoring of asphalt concrete core wall of high earth rock dam, which effectively solves the problems The problems of conventional monitoring methods are solved, and the three-dimensional deformation monitoring of asphalt concrete core wall is realized.

Low-velocity impact of clamped slender rectangular sandwich tubes with metal foam core

The main purpose of this work is to investigate the yield criterion and dynamic response of fully clamped slender rectangular sandwich tubes with metal foam core struck by a low-velocity heavy mass. A plastic yield criterion is proposed for the rectangular sandwich tubes with metal foam core. Using the yield criterion, analytical solutions are derived for the dynamic response of fully clamped slender rectangular sandwich tubes with metal foam core struck by a low-velocity heavy mass, in which the foam core strength effect and the interaction of bending and stretching are considered. Numerical calculations are carried out to predict the dynamic response of the rectangular sandwich tubes under low-velocity impact. The analytical model captures the numerical results reasonably. The effects of foam core strength and wall thickness of tube on the dynamic response are discussed in detail. It is shown that the present analytical model can reasonably predict the dynamic response of the rectangular sandwich tube with metal foam core under the low-velocity impact.

Uncoupled rocking and shear base‐mechanisms for resilient reinforced concrete high‐rise buildings

SummaryHigh‐rise buildings are an efficient solution to meet the housing challenges of global urbanization that is happening at an incredible pace. Code‐based seismic design philosophies are aimed at achieving collapse‐prevention under major earthquakes, implying extensive structural damage associated with important losses. A number of high‐performance systems have been investigated for enhancing the resilience of high‐rise buildings whose design is especially challenging due to higher‐mode effects even when a flexural mechanism is formed at the base of the structure. To this end, this paper proposes a new concept consisting of a three‐dimensional uncoupled rocking and shear mechanism system for high‐rise buildings where reinforced concrete (RC) core walls are used as the lateral‐force‐resisting system. The proposed system provides a dual‐mechanism at the base that independently limits both overturning moments (OTMs) and shear forces and thus more effectively mitigates higher‐mode effects. The characteristic mechanics of the proposed system are first studied through an idealized model. A physical embodiment is then designed, detailed, and validated through advanced models and extensive nonlinear dynamic analyses. A 42‐story RC core‐wall building that is located in Los Angeles and was studied as part of the PEER Tall Buildings Initiative is used as a reference structure in this study. Results confirmed that the proposed system eliminates damage at the base of the walls and minimizes the inelastic demands over the height of the building. In a general sense, the proposed concept provides a framework in which the intended dual mechanism can be implemented to a wider range of high‐rise structures.

Seismic design of outrigger systems using equivalent energy design procedure

SummaryAn outrigger system is an effective structural scheme that is commonly used in high‐rise construction to increase the stiffness of concrete core walls and to reduce the moment demand within the walls. Despite the on‐going use of outrigger systems around the world, a formal seismic design procedure is yet available. This paper presents an equivalent energy design procedure (EEDP) to design outrigger systems for seismic applications. Three prototype outrigger‐wall buildings of various heights are designed for Vancouver, Canada. Detailed finite element models are developed to assess the seismic performance of the prototype buildings and to assess the safety using the FEMA P695 methodology. The result shows that EEDP is an efficient method to design outrigger systems which results in structures that can achieve sufficient margin of safety against collapse and satisfy multiple performance objectives at different seismic hazard levels.

Seismic performance of steel-enhanced damping concrete core walls with concealed steel plate bracings

Experimental study was conducted on six 1/6 scale steel-enhanced damping concrete composite core walls (SEDCCW) with steel plate bracings under cyclic load reversals and constant axial load, to investigate the influences of stirrups in boundary zone, layer number of X-shaped steel plate bracing, encased steel arrangements of boundary zones and coupling beams, the aspect ratio (AR) and the axial compression load ratio (ALR) on the seismic behavior of the specimens. The cracking patterns, failure modes, load-bearing capacities, ductility factors, energy dissipation capacities and shear lag effects of the specimens were discussed. Then parametric analysis was carried out on 27 numerical models based on verified finite element models to assess the influences of the ALR and the AR of specimens, span-to-depth ratios of coupling beams, the encased steel ratios of corner columns, hidden columns and coupling beams, steel ratios of wall bracings on the overall seismic performance of the SEDCCW specimens. The analysis results indicate that the SEDCCW specimens can also obtain good deformation capacity when the design axial load ratio is less than 1. 0 or span-to-depth ratio of coupling beam is larger than 1.0; the steel ratio of wall bracing is the most influential factor on load bearing capacity and deformation capacity of the SEDCCW specimens, the influence of encased steel ratios of corner columns and hidden columns on ductility of the SEDCCW specimens is greater than that of encased steel ratios of coupling beams.