Behavior Of Walls Research Articles

Advancing plant cell wall modelling: Atomistic insights into cellulose, disordered cellulose, and hemicelluloses – A review

The complexity of plant cell walls on different hierarchical levels still impedes the detailed understanding of biosynthetic pathways, interferes with processing in industry and finally limits applicability of cellulose materials. While there exist many challenges to readily accessing these hierarchies at (sub-) angström resolution, the development of advanced computational methods has the potential to unravel important questions in this field. Here, we summarize the contributions of molecular dynamics simulations in advancing the understanding of the physico-chemical properties of natural fibres. We aim to present a comprehensive view of the advancements and insights gained from molecular dynamics simulations in the field of carbohydrate polymers research. The review holds immense value as a vital reference for researchers seeking to undertake atomistic simulations of plant cell wall constituents. Its significance extends beyond the realm of molecular modeling and chemistry, as it offers a pathway to develop a more profound comprehension of plant cell wall chemistry, interactions, and behavior. By delving into these fundamental aspects, the review provides invaluable insights into future perspectives for exploration. Researchers within the molecular modeling and carbohydrates community can greatly benefit from this resource, enabling them to make significant strides in unraveling the intricacies of plant cell wall dynamics.

Centrifuge Modeling of Backfill Consolidation in Soil-bentonite Cutoff Walls

Soil-bentonite (SB) is commonly adopted for the backfill of vertical cutoff walls to contain contaminated groundwater. The permeability of SB backfill is dependent on its effective stress state, which is affected by the backfill consolidation process. This paper presents a geotechnical centrifuge model test to simulate the primary consolidation of typical SB cutoff walls with the advantages of reduced scale in time and size. The moisture content and earth pressure of the wall were monitored at varied depths. Test results showed that the rapid consolidation stage developed swiftly and various consolidation indicators exhibited significant development. Within the buried depth over the half (approximately two-thirds), the distribution of vertical effective stress was similar to the Bucknell field testing results, namely that it increased nonlinearly and then tended to stabilize. Also, the cumulative effect of lateral frictional resistance increased with depth and reached its peak value. In the deeper buried areas, lateral frictional resistance decreased sharply before increasing again with increasing depth, while vertical effective stress followed a pattern of significant increase followed by a decrease. This centrifuge test may be useful for achieving a comprehensive evaluation of the consolidation behaviour and mechanism of SB cutoff walls.

Effect of in-plane damage on the out-of-plane strength of masonry walls with openings

Past earthquakes have shown that masonry walls are vulnerable to fail near the openings. Openings such as doors and windows are an essential part of the structure. The presence of an opening reduces the strength and stiffness of the masonry structures. It also affects the load-resistant mechanism of the masonry walls. The walls are subjected to simultaneous in-plane and out-of-plane forces during seismic events. Therefore, the analysis of the masonry walls either in in-plane or out-of-plane direction may not give a proper picture of the global behavior of the masonry structures. The masonry walls deform primarily in the in-plane direction if the walls are properly tied with each other, and the structure is constructed by following codal provisions. Under this situation, it is necessary to investigate the effect of in-plane damage on the out-of-plane strength of the masonry walls. Few researchers have studied the behavior of solid unreinforced masonry walls under combined loading. However, limited work can be found for masonry walls with openings. Therefore, the present study focuses on the effect of different types of opening layouts on the combined in-plane and out-of-plane behavior of masonry walls incorporating varying pre-compression. Further, in masonry buildings, walls are interconnected, making the masonry walls of various shapes. In this study, masonry walls of rectangular and I shapes have been considered to examine the effect of cross-walls under combined loading. Interaction curves have been developed for the walls subjected to the in-plane loading followed by an out-of-plane pressure. Based on the results, the maximum opening percentage in the masonry walls has been suggested, which is desirable in the case of masonry buildings constructed in high seismic zones.

Out-of-plane interactive behavior and design of novel T-hooked buckling-restrained steel plate shear walls

To eliminate the use of a large number of connecting bolts for the cover panels in conventional buckling-restrained steel plate shear walls (BRSPSWs), T-hooked BRSPSW was proposed by using T-sectional stiffeners for restraining the out-of-plane deformation of the cover panels. With larger-sized flexural cover panels that provide confinement effects to the infilled steel plate, the out-of-plane interactive behavior between the infilled steel plate and each cover panel is greatly concerned for safe designs of the T-hooked BRSPSW. In this paper, a refined finite element (FE) model was established for evaluating the out-of-plane restraining effects in the T-hooked BRSPSW. The key parameters affecting the high-order buckling modes of the infilled steel plate were analyzed. The average spacing between adjacent buckling half-waves varied from 0.15 to 0.7 times the height of the steel sub-plate across common parameter ranges. Furthermore, a formula that estimates the total extrusion force produced by the buckled steel plate was corrected. By simplifying the cover panels into one-way flexural plates under uniform force, a flexural moment amplification coefficient in the range of 1.11 − 9.74 was defined to consider the difference between the actual strip-shaped interaction forces and the simplified model. Finally, a formula to calculate the bending moment of cover panels was proposed to safely design the T-hooked BRSPSWs.

Viscoelastic properties of the equine hoof wall

The equine hoof wall has outstanding impact resistance, which enables high-velocity gallop over hard terrain with minimum damage. To better understand its viscoelastic behavior, complex moduli were determined using two complementary techniques: conventional (∼5 mm length scale) and nano (∼1 µm length scale) dynamic mechanical analysis (DMA). The evolution of their magnitudes was measured for two hydration conditions: fully hydrated and ambient. The storage modulus of the ambient hoof wall was approximately 400 MPa in macro-scale experiments, decreasing to ∼250 MPa with hydration. In contrast, the loss tangent decreased for both hydrated (∼0.1–0.07) and ambient (∼0.04–0.01) conditions, over the frequency range of 1–10 Hz. Nano-DMA indentation tests conducted up to 200 Hz showed little frequency dependence beyond 10 Hz. The loss tangent of tubular regions showed more hydration sensitivity than in intertubular regions, but no significant difference in storage modulus was observed. Loss tangent and effective stiffness were higher in indentations for both hydration levels. This behavior is attributed to the hoof wall's hierarchical structure, which has porosity, functionally graded aspects, and material interfaces that are not captured at the scale of indentation. The hoof wall's viscoelasticity characterized in this work has implications for the design of bioinspired impact-resistant materials and structures. Statement of significanceThe outer wall of horse hooves evolved to withstand heavy impacts during gallop. While previous studies have measured the properties of the hoof wall in slowly changing conditions, we wanted to quantify its behavior using experiments that replicate the quickly changing forces of impact. Since the hoof wall's structure is complex and contributes to its overall performance, smaller scale experiments were also performed. The behavior of the hoof wall was within the range of other biological materials and polymers. When hydrated, it becomes softer and can dissipate more energy. This work improves our understanding of the hoof's function and allows for more accurate simulations that can account for different impact speeds.

Out-of-plane impact behavior and post-impact damage evaluation of GFRP bar-reinforced concrete shear walls in fire

Fiber-reinforced polymers (FRP) have been a prospective material in engineering. However, the attenuation of FRP bar-reinforced concrete members in fire is unclear. This paper studies the impact resistance of glass fiber-reinforced polymer bar-reinforced concrete (GFRP-RC) shear walls under high temperatures. Considering the impacts of strain rate enhancement and high temperature softening on GFRP bars and concrete, a numerical model with finite elements in three dimensions was created. To verify the model, three cases were simulated and compared with the test records, including the seismic performance of FRP-RC shear walls under axial compression, the seismic behavior of reinforced concrete (RC) shear walls under high temperatures, and RC shear walls' impact response. Based on the calibrated numerical model, the displacement, impact force, reaction force, failure mode, energy distribution, internal force and the residual shear bearing capacity of GFRP-RC shear wall subjected to impact under different fire times were analyzed. The influence of fire time on the failure mechanism of GFRP-RC shear walls was studied. Taking the mid-span displacement as the damage index, the evaluation criteria for the four damage levels were determined. The findings indicate that the type of reinforcement has little effect on the shape of impact force, reaction force and displacement time history curve. The peak values of impact force and reaction force of RC walls are larger than those of GFRP-RC shear walls, while the former has smaller peak displacements and residual displacements. The damage of shear walls becomes more severe as the fire time increases, as does the displacement. Also, the impact force, reaction force, shear force and bending moment decrease gradually. The energy absorbed by shear walls is primarily dissipated by concrete, the part by GFRP bars accounting for a small proportion. The post-impact residual bearing capacity of GFRP-RC shear walls is linearly related to the mid-span displacement under impact loads, primarily influenced by high-temperature exposure.

An Innovative, Lightweight, and Sustainable Solution for the Integrated Seismic Energy Retrofit of Existing Masonry Structures

A large percentage of existing building stock in Italy and throughout Europe is ageing and no longer complies with current regulations, particularly in terms of sustainability. For these reasons, an urgent consolidation plan is needed to ensure an increase in both seismic response and energy response. Indeed, these constructions were built before the actual technical codes, and currently, they are not able to withstand seismic actions. Meanwhile, they are subject to thermal dispersions that could be due to the use of materials with poor properties or construction errors. Among the numerous consolidation techniques, an innovative solution consisting of a coating system has appeared on the construction market in recent decades. It is an integrated solution that simultaneously improves the seismic and energy behaviour of the building. The paper proposes the evaluation of this lightweight and sustainable solution through some experimental tests which were performed at the National Institute for Research and Development in Constructions, located in the city of Timişoara (Romania). The tests were aimed to investigate the out-of-plane behaviour of a masonry wall (1.20 m × 2.40 m × 0.60 m) obtained by combining two smaller panels with mortar and subjecting them to constant vertical force and pushing by an increasing horizontal one. Its response was assessed before and after the application of extruded aluminium alloy base profiles belonging to the system under study.

Design & Analysis of Non-Linear Property of Material for Semi-Rigit, Fixed & Flexible Structural Frames

During an earthquake, failure of structure starts off-evolved at factors of weak spot. This weak point arises due to discontinuity in mass, stiffness and geometry of structure. The systems having this discontinuity are termed as irregular systems. Irregular structures contribute a massive portion of city infrastructure. The effect of vertically irregularities within the seismic overall performance of systems will become definitely vital. The main objective of the analysis is to study the behavior of flat slab system in vertical irregular multi-storied building against different forces acting on it during earthquake. Also, the objective of analysis is to study the structural behavior of shear wall – flat slab interaction with opening. The analysis is made between in the three types of G+9 storey building with 0 % vertical irregularity, 200 % vertical irregularity and 300% vertical irregularity. In all these building’s shear wall is provided with & without 20% opening. Total 15 modeled are studied and their results were compared. Key Words: Flat slab, Vertical Geometric Irregularity, Shear wall with opening, Response Spectrum analysis, STAAD Pro2007

Behavior of MSE wall under static load with different strips shapes

Behavior of MSE wall under static load with different strips shapes

Structural assessment of translucent walls built with a novel type of insulating aerogel-filled glass bricks

Among a multitude of functions, the façade is responsible for providing sufficient thermal insulation and supplying the building interior with enough natural light. For the latter, transparent glazed areas are essential. However, compromises in terms of the glass-to-wall ratio are often necessary since large glazed areas lead to overheating in summer and heat loss in winter. A novel type of highly insulating translucent glass brick made from annealed glass and filled with aerogel granulate was developed recently as an alternative in this regard. The bricks are not supposed to replace the transparent glass areas, but to offer a translucent alternative for part of the otherwise opaque wall areas. This paper focuses on the structural behaviour of walls composed of such aerogel-filled glass bricks. The components of such a brick and their functions are described. Moreover, two prototype systems for supporting the bricks in translucent walls are introduced—one with interlocking connections and pre-stressed wires, the other with interlocking connections and edge clamping. Both systems are analysed in finite element simulations from a structural point of view under out-of-plane loading. The resulting global deformations as well as occurring stresses in different components are analysed. Based on the findings, advantages and limitations of the different systems are highlighted and suggestions for improved alternative systems for translucent walls with insulating aerogel-filled glass bricks are made.

Torsional behavior of composite shear walls and load‐bearing sandwich panels: An experimental investigation

Torsional behavior of composite shear walls and load‐bearing sandwich panels: An experimental investigation

Experimental research on the out-of-plane performance of traditional residential timber frame-wall with embedded metal connectors in central China

Traditional residential brick walls in central China typically employ metal connectors to connect with embedded timber columns for out-of-plane tensioning. To analyze the influence of metal connectors on the out-of-plane mechanical behavior of brick walls, several wall specimens were fabricated. The specimens comprised one without any connectors and three with different quantities of metal connectors placed at various locations. Static tests were conducted using gasbag loading. The deformation histories, failure modes, characteristic points of the specimens were obtained, and the shear force distribution patterns were analyzed. Furthermore, the influence of metal connectors on the collaborative performance of timber frames and brick walls in terms of their out-of-plane behavior was examined. The results indicate that walls partially equipped with metal connectors show an enhanced bearing capacity of around 17.50 % and the lateral deformation capacity of 28.38 % compared to walls without connectors. Furthermore, walls fully equipped with connectors show an increased bearing capacity by 22.51 % and lateral deformation capacity by 57.17 %. In comparison to walls without connectors, those fully equipped with connectors exhibit a 7.69 % increase in the column head shear force ratio. Consequently, the distribution of shear forces on column head is notably influenced by the presence of connectors.

A piecewise-linear backbone model for unbonded post-tensioned concrete masonry shear walls

Unbonded post-tensioned concrete masonry (UPCM) shear walls present an effective seismic force resisting system due to their ability to mitigate expected damage risks through their self-centering capabilities. A few design procedures were proposed to predict the in-plane flexural response of UPCM walls, albeit following only basic mechanics and/or extensive iterative methods. Such procedures, however, may not be capable of capturing the complex nonlinear relationships between different parameters that affect UPCM walls’ behavior or are rather tedious to be adopted for design practice. In addition, the restricted datasets used to validate these procedures may cast doubt on their accuracy and validity for new, unseen data, further hindering their adoption by practitioners and design standards. To address these issues, an experimentally-validated nonlinear numerical model was adopted in this study and subsequently employed to simulate 95 UPCM walls with a range of different design parameters to compensate for the lack of relevant diverse experimental data in the current literature. Guided by mechanics, and employing this database, an evolutionary algorithm—multigene genetic programming (MGGP), was adopted to uncover the relationships controlling the response of UPCM walls, and subsequently develop simplified closed-form wall behavior prediction expressions. Specifically, through integrating MGGP and basic mechanics, a piecewise-linear backbone model was developed to predict the load-displacement backbone for UPCM walls up to 20% strength degradation. Compared to existing predictive procedures, the prediction accuracy of the developed model and its closed-form nature are expected to facilitate better understanding of such wall behaviors and subsequently open the gate to further incorporate other experimental and numerical results to ultimately deploy UPCM in mainstream building designs in the near future.

Experimental study on the load bearing behavior of shored mechanically stabilized earth wall

Shored mechanically stabilized earth (SMSE) walls have been increasingly applied in the projects of widening existing roads or new construction of roads on slopes because of their good carbon emission reduction and mechanical performance. In this paper, a scaled-down model test of SMSE wall with shoring wall batter of 1H:2V was conducted to study the load-bearing behavior of SMSE wall under this terrain condition, and the results including wall deformations, earth pressures, reinforcement strains, and potential failure surface were analyzed. The results show that although the backfill near the shoring wall was not directly compressed by the load, it still slipped along the backfill-shoring wall interface. The loading created a tensile pressure zone in the upper part of the backfill-shoring wall interface, which may lead to tensile cracking. The uppermost layer of geogrid was more prone to sliding, while the tensile deformation was smaller, and its strain value was overall smaller than the strain value of the geogrid below it. As the load increases, the potential failure surface changed from a Rankine failure surface to a bilinear potential failure surface. The potential failure surface did not pass through the heel of the SMSE wall under large loads.

Experimental studies on the mechanical behaviors of cold-formed thin-walled steel-foam concrete composite walls

This paper presents experimental studies to investigate the compressive and shear behaviors of cold-formed thin-walled steel-foam concrete composite walls. Three compressive walls and three shear walls were tested. The failure mode and load-displacement curve of the specimen were obtained from the compressive experiment. The compressive wall infilled with foam concrete mainly experienced distortion buckling of the end stud and local crushing failure of the concrete. The stud openings had a limited effect on the compressive bearing capacity of the composite wall. The failure mode and load-deformation curve were obtained in shear tests. The ductility index, shear stiffness, yield load, peak load, energy dissipation, and stiffness degradation were analyzed. The shear composite wall filled with foam concrete mainly occurred concrete crushing failure, local or distortional buckling failure of the end stud, and cracking failure of the calcium silicate board. The shear stiffness, shear capacity, ductility, and energy dissipation of the composite wall could be significantly improved after filling with foam concrete.

Self-organising maps in the analysis of strains of human abdominal wall to identify areas of similar mechanical behaviour

The study refers to the application of a type of artificial neural network called the Self-Organising Map (SOM) for the identification of areas of the human abdominal wall that behave in a similar mechanical way. The research is based on data acquired during in vivo tests using the digital image correlation technique (DIC). The mechanical behaviour of the human abdominal wall is analysed during changing intra-abdominal pressure. SOM allow to study simultaneously three variables in four time/load steps. The variables refer to the principal strains and their directions. SOM classifies all the abdominal surface data points into clusters that behave similarly in accordance with the 12 variables. The analysis of the clusters provides a better insight into abdominal wall deformation and its evolution under pressure than when observing a single mechanical variable. The presented results may provide a better understanding of the mechanics of the living human abdominal wall. It might be particularly useful when selecting proper implants as well as for the design of surgical meshes for the treatment of abdominal hernias, which would be mechanically compatible with identified regions of the human anterior abdominal wall, and possibly open the way for patient-specific solutions.

TRM strengthening as effective prevention against premature failure of masonry walls

Masonry structures are very prone to cracking and premature failure in the presence of shear loading. Therefore, effective prevention of their premature damage is needed. This paper presents laboratory tests of small models made of autoclaved aerated concrete (AAC) blocks, which were externally reinforced using two different strengthening sets consisting of mortar and mesh, and subjected to diagonal compression. The experiments used a commercialised system designed for the strengthening of typical masonry substrates (brick, stone) and a low-cost and lowstrength mesh and mortar set used as part of a system for insulating buildings. The analyses presented are of a comparative nature and describe changes in the behaviour of the models depending on the strengthening set used. The application of full-surface strengthening clearly changed the behaviour of AAC walls from brittle one to the ‘pseudo-ductile’ one observed after the appearance of the first cracks. In all strengthened models, a significant increase in the load capacity (from 3% to 62%) and a post-peak phase were reported. An interesting finding was the high efficiency of nonstructural materials (plastering system), comparable to the effects of the use of commercialised system solutions. This strengthening can be successfully considered as an effective preventive action. Finally, a simplified method is provided to calculate the contribution of the strengthening to the load bearing capacity of the strengthened models. The method defines the effect of the mesh and the mortar independently, based only on the basic material properties of these two components.

Bending behavior of segmental precast diaphragm walls using bolted sleeve joints

AbstractTo study the bending behavior of segmental precast diaphragm walls using bolted sleeve joints, 2 full size specimens were tested. Both BC and EC specimens were connected using bolts with steel sleeves as positioner. BC specimen was consisted of two fully RC plates while EC specimen had precast holes in the concrete walls for lightweight treatment. Ultimate strengths, deformations, strains and failure modes were obtained from the test results. Finite element models were developed using ABAQUS and verified against the test results. The verified finite element models were used to further analyze the stress state of specimens under different loading. It indicated that the bolted sleeve joint exhibited good bearing capacity and bending stiffness. The lightweight treatment in the concrete part had minor effect and the design requirement could be satisfied.

Study on hydraulic conductivity of dredged sediment-attapulgite vertical cutoff walls under confining pressure

Landfills require effective containment systems to prevent the leakage of leachate into the underground environment. Cutoff walls are commonly employed for this purpose, with options including rigid and flexible designs. In areas where structural strength is not a primary concern, flexible cutoff walls offer lower permeability and environmental benefits due to their lack of cement content, thereby reducing CO2 emissions. This study investigates the use of dredged sediment and attapulgite as materials for flexible cutoff walls. Through analyses of bound water content, free water content, hydraulic conductivity, and scanning electron microscopy, we explore the impact of confining pressures on cutoff wall permeability.Our findings reveal that the consolidation induced by confining pressure does not significantly alter the bound water content within the cutoff wall. Instead, changes in water content are predominantly attributed to variations in free water content. Under identical confining pressures, we observe a positive correlation between permeability and hydraulic gradient, with permeability increasing as the hydraulic gradient rises, and anti-permeability decreasing accordingly. Additionally, when holding the hydraulic gradient constant, increasing confining pressure leads to a continuous decrease in permeability. Microscopic analyses highlight that high confining pressure not only compresses pore diameter but also alters pore morphology, thereby influencing permeability.This study contributes to the understanding of cutoff wall behavior under different conditions. Our results demonstrate that increasing confining pressure during soil consolidation effectively reduces cutoff wall permeability to meet design standards. However, the influence of high leachate head on permeability should also be considered. These findings provide a more environmentally friendly and lower permeability option for landfill sites, which is significant for the design and enhancement of containment systems in landfill sites.

Behavior of steel liner tray walls under external blast: Experimental testing and numerical simulations

Explosions produced in urban or industrial areas due to accidental or intentional detonation of explosives are low-probability but high-impact events. If standoff distance from buildings or other constructions is small, explosions can cause structural failures and serious injuries or deaths of occupants. Although heavy/stiff enclosure systems were long considered appropriate to protect buildings against explosive threats, lighter and flexible steel-based systems, which are increasingly used for modern buildings, may also provide satisfactory performance. The study presents the results of full-scale blast tests on liner tray walls attached to a steel frame building. Walls were tested against increasing blast charges until failure. Due to very high peak pressures and very short durations, the loading regime could be classified as impulsive. The ultimate strength is given by the failure of the end fasteners, after large bolt hole elongations coupled with the pull-through of the end fasteners. If the insulation and outer cladding are lost, the liner trays are directly exposed to blast and the seaming fasteners at overlapping sheets are prematurely lost. As a result, the wall panels work mostly independently, as one-way elements. On the contrary, if the outer cladding protects the seaming fasteners, the overlapping provides additional capacity due to membrane effect (two-way behavior). Numerical models were calibrated using test data and were further used to obtain more information about liner tray behavior under blast.