Materials

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33 pages, 54343 KiB

Open AccessArticle

Behavior of Partially Grouted Concrete Masonry Walls under Quasi-Static Cyclic Lateral Loading

by Sebastián Calderón, Laura Vargas, Cristián Sandoval and Gerardo Araya-Letelier

Materials 2020, 13(10), 2424; https://doi.org/10.3390/ma13102424 - 25 May 2020

Cited by 24 | Viewed by 3222

Eight partially grouted (PG-RM) concrete masonry walls were tested to study the influence of the strength and width of blocks, the wall aspect ratio, the horizontal and vertical reinforcement ratio, and the presence of edge elements (flanges). The results were analyzed in terms [...] Read more.

Eight partially grouted (PG-RM) concrete masonry walls were tested to study the influence of the strength and width of blocks, the wall aspect ratio, the horizontal and vertical reinforcement ratio, and the presence of edge elements (flanges). The results were analyzed in terms of the failure mode, damage progression, shear strength, lateral stiffness degradation, equivalent viscous damping ratio, and displacement ductility. Additionally, the performances of some existing shear expressions were analyzed by comparing the measured and predicted lateral load capacity of the tested walls. Based on the results, a slight increment in the lateral stiffness was achieved when employing stronger blocks, while the shear strength remained constant. Besides, increasing the width of concrete blocks did not have a significant effect on the shear strength nor in the initial tangential stiffness, but it generated a softer post-peak strength degradation. Increasing the wall aspect ratio reduced the brittleness of the response and the shear strength. Reducing the amount of vertical reinforcement lowered the resulting shear strength, although it also slowed down the post-peak resistance degradation. Transversal edge elements provided integrity to the wall response, generated softer resistance degradation, and improved the symmetry of the response, but they did not raise the lateral resistance. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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22 pages, 10047 KiB

Open AccessArticle

Study on the Restoration of a Masonry Arch Viaduct: Numerical Analysis and Lab Tests

by Damian Beben, Janusz Ukleja, Tomasz Maleska and Wojciech Anigacz

Materials 2020, 13(8), 1846; https://doi.org/10.3390/ma13081846 - 14 Apr 2020

Cited by 5 | Viewed by 3464

Abstract

This article presents an analysis of the load-carrying capacity of a historic masonry arch viaduct. The vault was made of bricks and lime-cement mortar. It was built in 1886 and, therefore, its historical character had to be included in the restoration project. The [...] Read more.

This article presents an analysis of the load-carrying capacity of a historic masonry arch viaduct. The vault was made of bricks and lime-cement mortar. It was built in 1886 and, therefore, its historical character had to be included in the restoration project. The main task of the restoration was to bring the viaduct to a technical condition corresponding to the current requirements to allow normal (or limited) service. The strength of the brickwork and joints (mortar) was examined experimentally in the laboratory and on the viaduct. This paper presents numerical calculations for the masonry viaduct that were performed using two programs based on the finite element method. As the project documentation was unknown, two- and three-hinged models of the masonry arch were analyzed. The axial forces, shear forces, bending moments, displacement, normal stresses, and shear stresses generated from the numerical analysis have been discussed. The conditions of the load capacity of the arch viaduct due to compression and shearing have been met. The safety of a masonry arch of the viaduct was determined. Finally, the restoration scope of the masonry viaduct was proposed. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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17 pages, 3861 KiB

Open AccessArticle

Study on Rheological Behavior and Surface Properties of Epoxy Resin Chemical Grouting Material Considering Time Variation

by Zhenhua Su, Zaiqin Wang, Da Zhang and Tao Wei

Materials 2019, 12(20), 3277; https://doi.org/10.3390/ma12203277 - 9 Oct 2019

Cited by 20 | Viewed by 3381

Abstract

Epoxy resins are widely used for repairing cracks in stone, mortar and masonry. A main factor that influences the grouting quality is the permeability of grout. However, the permeability will deteriorate over time because of the reaction of chemical grouting materials, which will [...] Read more.

Epoxy resins are widely used for repairing cracks in stone, mortar and masonry. A main factor that influences the grouting quality is the permeability of grout. However, the permeability will deteriorate over time because of the reaction of chemical grouting materials, which will greatly affect the results of grouting. To the best of our knowledge, there are few reports that focus on the time-varying properties of viscosity and affinity of epoxy resins grouting material. In this paper, we investigate the changing rules of viscosity and affinity with time by studying the viscosity, surface tension and contact angle of the epoxy grouting material. We establish the mathematical model for the time-dependent properties of CW epoxy resin on viscosity and affinity with experimental verification. Moreover, we make a detailed discussion on the modeling of viscosity variation considering both time and temperature. The results show important guiding significance and application value for judging the grout irrigability in the construction process. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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21 pages, 8957 KiB

Open AccessArticle

Effectiveness and Compatibility of a Novel Sustainable Method for Stone Consolidation Based on Di-Ammonium Phosphate and Calcium-Based Nanomaterials

by Cecilia Pesce, Ligia M. Moretto, Emilio F. Orsega, Giovanni L. Pesce, Marco Corradi and Johannes Weber

Materials 2019, 12(18), 3025; https://doi.org/10.3390/ma12183025 - 18 Sep 2019

Cited by 26 | Viewed by 3868

Abstract

External surfaces of stones used in historic buildings often carry high artistic value and need to be preserved from the damages of time, especially from the detrimental effects of the weathering. This study aimed to test the effectiveness and compatibility of some new [...] Read more.

External surfaces of stones used in historic buildings often carry high artistic value and need to be preserved from the damages of time, especially from the detrimental effects of the weathering. This study aimed to test the effectiveness and compatibility of some new environmentally-friendly materials for stone consolidation, as the use thereof has been so far poorly investigated. The treatments were based on combinations of an aqueous solution of di-ammonium phosphate (DAP) and two calcium-based nanomaterials, namely a commercial nanosuspension of Ca(OH)₂ and a novel nanosuspension of calcite. The treatments were applied to samples of two porous stones: a limestone and a sandstone. The effectiveness of the treatments was assessed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, ultrasound pulse velocity test, colour measurements, and capillary water absorption test. The results suggest that the combined use of DAP and Ca-based nanosuspensions can be advantageous over other commonly used consolidants in terms of retreatability and physical-chemical compatibility with the stone. Some limitations are also highlighted, such as the uneven distribution and low penetration of the consolidants. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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9 pages, 4148 KiB

Open AccessArticle

Yearly Energy Performance Assessment of Employing Expanded Polystyrene with Variable Temperature and Moisture–Thermal Conductivity Relationship

by Maatouk Khoukhi, Shaimaa Abdelbaqi and Ahmed Hassan

Materials 2019, 12(18), 3000; https://doi.org/10.3390/ma12183000 - 16 Sep 2019

Cited by 13 | Viewed by 2225

Abstract

This paper investigated the impact of the changes of thermal conductivity of an expanded polystyrene insulation layer embedded in a typical residential building on the cooling effect at different temperatures and moisture contents. The simulation was performed using expanded polystyrene (EPS) in the [...] Read more.

This paper investigated the impact of the changes of thermal conductivity of an expanded polystyrene insulation layer embedded in a typical residential building on the cooling effect at different temperatures and moisture contents. The simulation was performed using expanded polystyrene (EPS) in the extremely hot conditions of Al-Ain (United Arab Emirates, UAE) at different levels of density, denoted as low density LD (12 kg/m³), high density HD (20 kg/m³), ultra-high density UHD (30 kg/m³), and super-high density SHD (35 kg/m³), and three moisture content levels (10%, 20%, and 30%), compared to dry LD insulation material. The thermal performance of the building incorporating polystyrene with variable thermal conductivity (λ-value) was compared to one with a constant thermal conductivity by assessing the additional cooling demand and capacity due to the λ-relationship with time, using e-quest as a building energy analysis tool. The results showed that, when the λ-value was modeled as a function of operating temperature, its effect on the temperature profile during daytime was significant compared with the use of a constant λ-value. The monthly energy consumption for cooling required by the building was found to be higher in the case of variable thermal conductivity for the LD sample. The yearly average change in space cooling demand and cooling capacity when employing polystyrenes with constant and variable thermal conductivity increased with the increase of the moisture content. Indeed, the highest changes in cooling demand and capacity were 6.5% and 8.8% with 30% moisture content polystyrene. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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35 pages, 22893 KiB

Open AccessFeature PaperArticle

Wire Ropes and CFRP Strips to Provide Masonry Walls with Out-Of-Plane Strengthening

by Elena Ferretti

Materials 2019, 12(17), 2712; https://doi.org/10.3390/ma12172712 - 24 Aug 2019

Cited by 3 | Viewed by 4559

Abstract

The present paper deals with an improvement of the strengthening technique consisting in the combined use of straps—made of stainless steel ribbons—and CFRP (Carbon Fiber Reinforced Polymer) strips, to increase the out-of-plane ultimate load of masonry walls. The straps of both the previous [...] Read more.

The present paper deals with an improvement of the strengthening technique consisting in the combined use of straps—made of stainless steel ribbons—and CFRP (Carbon Fiber Reinforced Polymer) strips, to increase the out-of-plane ultimate load of masonry walls. The straps of both the previous and the new combined technique pass from one face to the opposite face of the masonry wall through some holes made along the thickness, giving rise to a three-dimensional net of loop-shaped straps, closed on themselves. The new technique replaces the stainless steel ribbons with steel wire ropes, which form closed loops around the masonry units and the CFRP strips as in the previous technique. A turnbuckle for each steel wire rope allows the closure of the loops and provides the desired pre-tension to the straps. The mechanical coupling—given by the frictional forces—between the straps and the CFRP strips on the two faces of the masonry wall gives rise to an I-beam behavior that forces the CFRP strips to resist the load as if they were the two flanges of the same I-beam. Even the previous combined technique exploits the ideal I-beam mechanism, but the greater stiffness of the steel wire ropes compared to the stiffness of the steel ribbons makes the constraint between the facing CFRP strips stiffer. This gives the reinforced structural element a greater stiffness and delamination load. In particular, the experimental results show that the maximum load achievable with the second combined technique is much greater than the maximum load provided by the CFRP strips. Even the ultimate displacement turns out to be increased, allowing us to state that the second combined technique improves both strength and ductility. Since the CFRP strips of the combined technique run along the vertical direction of the wall, the ideal I-beam mechanism is particularly useful to counteract the hammering action provided by the floors on the perimeter walls, during an earthquake. Lastly, when the building suffers heavy structural damage due to a strong earthquake, the box-type behavior offered by the three-dimensional net of straps prevents the building from collapsing, acting as a device for safeguarding life. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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17 pages, 8820 KiB

Open AccessFeature PaperArticle

Effectiveness of Nanolime as a Stone Consolidant: A 4-Year Study of Six Common UK Limestones

by Stelios Tzavellos, Giovanni L. Pesce, Yu Wu, Alison Henry, Simon Robson and Richard J. Ball

Materials 2019, 12(17), 2673; https://doi.org/10.3390/ma12172673 - 22 Aug 2019

Cited by 15 | Viewed by 3628

Abstract

Protecting stone buildings from weathering and decay is a major challenge in the conservation of built heritage. Most of the stone consolidants currently available are well suited to silicate stones, but are less compatible with limestone. In this paper we present for the [...] Read more.

Protecting stone buildings from weathering and decay is a major challenge in the conservation of built heritage. Most of the stone consolidants currently available are well suited to silicate stones, but are less compatible with limestone. In this paper we present for the first time the results over a 4-year period of various consolidation treatments carried out using nanolime on 6 of the most representative and significant stones used in historic buildings in the United Kingdom. Tests investigated the influence of stone type, environmental conditions and pre-treatments on the effectiveness of the consolidation treatment. A comprehensive and rigorous testing programme was carried out to evaluate the short (12 weeks) and longer-term (4 years) effects. Stone samples were characterised before and after treatment using light and electron microscopy, sorptivity tests and a novel methodology employing drilling resistance to interrogate the near surface effects. Results show that for some of the stones, such as Clunch and Bath Stone, the positive effect of the treatment with nanolime is noticeable after 4 years since application. However, results for other stones such as Portland and magnesian limestone showed that the initial beneficial effect of the treatment is reduced after 4 years. Nanolime treatment of Ham Stone produced an unnoticeable effect on the continuous natural reduction of the drilling resistance of the specimen over time. The results presented are of immense value to conservators as they provide essential guidance on the most appropriate repair approach. Impact to the conservation industry will be to avoid the use of nanolime on stones where there is no perceivable benefit, reducing the risk of adverse effects, including potential damage to buildings. In additional costs will be saved which might otherwise have been spent on ineffective treatments. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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26 pages, 10421 KiB

Open AccessArticle

A Simulation Study to Calculate a Structure Conceived by Eugène Viollet-le-Duc in 1850 with Finite Element Analysis

by Adela Rueda Márquez de la Plata and Pablo Alejandro Cruz Franco

Materials 2019, 12(16), 2576; https://doi.org/10.3390/ma12162576 - 13 Aug 2019

Cited by 5 | Viewed by 3753

Abstract

This study aims to investigate the application of finite element calculations to mixed structures of complex materials. As an example, we chose a vault designed by Eugène Viollet-le-Duc in 1850, at which time it was not possible to verify the complexities of the [...] Read more.

This study aims to investigate the application of finite element calculations to mixed structures of complex materials. As an example, we chose a vault designed by Eugène Viollet-le-Duc in 1850, at which time it was not possible to verify the complexities of the different materials working together in a single structure using these calculation methods. To carry out the simulation, the internal qualities of each material and its current equivalent are taken into account. Thus, the composition of each element is crucial for its integration into the whole structure and its modeling and subsequent calculation. With this research, we show that a finite element analysis can also be applied to structures that are yet to be built. Furthermore, we verify the technological, construction and materials knowledge that has led us here and demonstrate that what was once a utopian vision can now be realized using the structures and materials we have access to today. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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28 pages, 8830 KiB

Open AccessArticle

Research on the Influence of Bed Joint Reinforcement on Strength and Deformability of Masonry Shear Walls

by Radosław Jasiński

Materials 2019, 12(16), 2543; https://doi.org/10.3390/ma12162543 - 9 Aug 2019

Cited by 18 | Viewed by 3307

Abstract

The areas of Central and Eastern Europe and, thus, Poland are not exposed to the effects of seismic actions. Any possible tremors can be caused by coal or copper mining. Wind, rheological effects, the impact of other objects, or a nonuniform substrate are [...] Read more.

The areas of Central and Eastern Europe and, thus, Poland are not exposed to the effects of seismic actions. Any possible tremors can be caused by coal or copper mining. Wind, rheological effects, the impact of other objects, or a nonuniform substrate are the predominant types of loading included in the calculations for stiffening walls. The majority of buildings in Poland, as in most other European countries, are low, medium-high brick buildings. Some traditional materials, like solid brick (>10% of construction materials market) are still used, but autoclaved aerated concrete (AAC) and cement-sand calcium-silicate (Ca-Si) elements with thin joints are prevailing (>70% of the market) on the Polish market. Adding reinforcement only to bed joints in a wall is a satisfactory solution (in addition to confining) for seismic actions occurring in Poland that improves ULS (ultimate limit state) and SLS (serviceability limit state). This paper presents results from our own tests on testing horizontal shear walls without reinforcement and with different types of reinforcement. This discussion includes 51 walls made of solid brick (CB) reinforced with steel bars and steel trusses and results from tests on 15 walls made of calcium-silicate (Ca-Si) and AAC masonry units reinforced with steel trusses and plastic meshes. Taking into account our own tests and those conducted by other authors, empirical relationships were determined on the basis of more than 90 walls. They are applicable to the design and construction phases to determine the likely effect of reinforcements on cracking stress that damage shear deformation and wall stiffness. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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18 pages, 9766 KiB

Open AccessArticle

Repair of Block Masonry Panels with CFRP Sheets

by Marco Corradi, Giulio Castori, Romina Sisti, Antonio Borri and Giovanni Luca Pesce

Materials 2019, 12(15), 2363; https://doi.org/10.3390/ma12152363 - 25 Jul 2019

Cited by 12 | Viewed by 4593

Abstract

In the 1980s, block masonry started to be widely used for new constructions in Italy’s earthquake prone areas. However, recent seismic events demonstrated that block masonry buildings may need to be repaired after earthquakes due to cracking. Construction defects are the main cause [...] Read more.

In the 1980s, block masonry started to be widely used for new constructions in Italy’s earthquake prone areas. However, recent seismic events demonstrated that block masonry buildings may need to be repaired after earthquakes due to cracking. Construction defects are the main cause for cracking of block work masonry. Carbon fiber reinforced polymer (CFRP) sheets have been used as a local repair method for non-defective and defective wall panels. An experimental program was formulated to investigate the shear behavior of block masonry walls repaired with CFRP sheets. A total of six wall panels were constructed in the laboratory and tested in shear (in-plane lateral loading). It was found that, although the control (non-defective) wall panels had a high ultimate load capacity, the use of CFRPs reduces the effects of construction defects and restores the lateral load capacity in non-defective walls. Overall, this research suggests that the use of epoxy-bonded CFRP sheets could be used for local repair of cracked wall panels. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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35 pages, 24459 KiB

Open AccessArticle

Combined Strengthening Techniques to Improve the Out-of-Plane Performance of Masonry Walls

by Elena Ferretti and Giovanni Pascale

Materials 2019, 12(7), 1171; https://doi.org/10.3390/ma12071171 - 10 Apr 2019

Cited by 13 | Viewed by 4977

Abstract

The purpose of this study is to improve the performance of walls under out-of-plane loads especially when subjected to the hammering action of the floors. The idea behind the paper is to provide the masonry walls with a device that behaves like a [...] Read more.

The purpose of this study is to improve the performance of walls under out-of-plane loads especially when subjected to the hammering action of the floors. The idea behind the paper is to provide the masonry walls with a device that behaves like a buttress, without having to build a traditional buttress. The solution presented in this paper consists of a mechanical coupling between the three-dimensional net of steel ribbons of the CAM (Active Confinement of Masonry) system and the CFRP (Carbon Fiber Reinforced Polymer) strips. Since the steel ribbons of the CAM system have a pre-tension, the mechanical coupling allows the steel ribbons to establish a semi-rigid transverse link between the CFRP strips bonded on the two opposite sides of a wall. Therefore, two vertical CFRP strips tied by the steel ribbons behave like the flanges of an I-beam and the flexural strength of the ideal I-beam counteracts the out-of-plane displacements of the wall. The experimental results showed that the combined technique inherits the strong points of both constituent techniques. In fact, the delamination load is comparable to that of the specimens reinforced with the CFRP strips and the overall behavior is as ductile as for the specimens reinforced with the CAM system. They also inspired a more performing combined technique. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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28 pages, 19172 KiB

Open AccessArticle

Some of the Latest Active Strengthening Techniques for Masonry Buildings: A Critical Analysis

by Elena Ferretti and Giovanni Pascale

Materials 2019, 12(7), 1151; https://doi.org/10.3390/ma12071151 - 9 Apr 2019

Cited by 21 | Viewed by 4163

Abstract

The present paper deals with the retrofitting of unreinforced masonry (URM) buildings, subjected to in-plane shear and out of-plane loading when struck by an earthquake. After an introductive comparison between some of the latest punctual and continuous active retrofitting methods, the authors focused [...] Read more.

The present paper deals with the retrofitting of unreinforced masonry (URM) buildings, subjected to in-plane shear and out of-plane loading when struck by an earthquake. After an introductive comparison between some of the latest punctual and continuous active retrofitting methods, the authors focused on the two most effective active continuous techniques, the CAM (Active Confinement of Masonry) system and the Φ system, which also improve the box-type behavior of buildings. These two retrofitting systems allow increasing both the static and dynamic load-bearing capacity of masonry buildings. Nevertheless, information on how they actually modify the stress field in static conditions is lacking and sometimes questionable in the literature. Therefore, the authors performed a static analysis in the plane of Mohr/Coulomb, with the dual intent to clarify which of the two is preferable under static conditions and whether the models currently used to design the retrofitting systems are fully adequate. Full article

(This article belongs to the Special Issue Reinforcement and Repair Materials for Masonry Structures)

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