Clay Masonry Research Articles

Influence of Prior Distributions and Fragility assessment methods in the estimation of the Magnitude of a Historical Seismic Event

The production of fragility functions describing the probable behaviour and damage on historical buildings is a key step in a method for the estimation of the magnitude of historical seismic events that uses a Bayes'. The fragilities are estimated by integrating the structural capacity with the seismic demand using either static methods, as the Capacity Spectrum Method (CSM), or dynamic methods, as Incremental Dynamic (IDA) and Multiple Stripes Analysis (MSA). Uncertainties in both resistance, demand, and distance and magnitude models propagate to the posterior magnitude distribution. The present paper studies the effect of uncertainties related both to the production of fragility functions and prior distributions, in the estimation of the magnitude of the 1763 Komárom earthquake (in historical Hungary). In the XVIII century most of the structures in the region were built of earth, adobe, clay or stone masonry, which is complex to model. While micro or detailed macro-modelling strategies are computationally costly, simplified macro-approaches are often more efficient, but require a pre-identification of the failure mode(s) and the determination of the backbone curve. For this study, a simplified macro-model of a Hungarian peasant house archetype is calibrated for CSM and IDA. The physical and geometrical uncertainties are incorporated in the fragilities using Monte-Carlo simulation. Prior magnitude and distance distributions are studied. The final magnitude estimates are presented and discussed.

Influence of Prior Distributions and Fragility assessment methods in the estimation of the Magnitude of a Historical Seismic Event

The production of fragility functions describing the probable behaviour and damage on historical buildings is a key step in a method for the estimation of the magnitude of historical seismic events that uses a Bayes'. The fragilities are estimated by integrating the structural capacity with the seismic demand using either static methods, as the Capacity Spectrum Method (CSM), or dynamic methods, as Incremental Dynamic (IDA) and Multiple Stripes Analysis (MSA). Uncertainties in both resistance, demand, and distance and magnitude models propagate to the posterior magnitude distribution. The present paper studies the effect of uncertainties related both to the production of fragility functions and prior distributions, in the estimation of the magnitude of the 1763 Komárom earthquake (in historical Hungary). In the XVIII century most of the structures in the region were built of earth, adobe, clay or stone masonry, which is complex to model. While micro or detailed macro-modelling strategies are computationally costly, simplified macro-approaches are often more efficient, but require a pre-identification of the failure mode(s) and the determination of the backbone curve. For this study, a simplified macro-model of a Hungarian peasant house archetype is calibrated for CSM and IDA. The physical and geometrical uncertainties are incorporated in the fragilities using Monte-Carlo simulation. Prior magnitude and distance distributions are studied. The final magnitude estimates are presented and discussed.

Performance-based interpretation of in-plane cyclic tests on RC frames with strong masonry infills

In line with the current European building practice, clay masonry infills are commonly adopted for the construction of enclosures and partitions in RC frame structures. In order to improve further the understanding of the seismic response of masonry infills in newly designed RC structures, within the scope of a systematic numerical and experimental research program, the in-plane experimental response of external masonry infills constructed with tongue and groove clay units has been studied. Particular attention has been devoted to the infill performance, the related damage distribution, the lateral stiffness, strength and dissipation capacity and a possible definition of performance limit states for future developments in the current design approach. This paper reports the framework and discusses the results of in-plane static cyclic tests on full-scale, single-storey, single-bay RC frame specimens with strong masonry infills with and without opening designed following European seismic design provisions, carried out at the laboratory of the Department of Civil Engineering and Architecture of the University of Pavia. Based on the observations during the tests, drift levels at the different limit states have been evaluated, with the attainment of large values for the solid specimen (0.30%, 0.50% and 1.75% at the operation, damage limitation and ultimate limit state, respectively), but lower performance for the panel with opening. The experimentally obtained lateral stiffness and strength have been compared with the results of some of the most common analytical models based on single diagonal equivalent strut, underlining the formulations that better fit the test outcomes.

Burglary resistance of thermal insulating clay unit masonry (RC 3)

AbstractIn 2017 the Austrian Clay Masonry Industry carried out a test of burglary resistance according to ÖNORM EN 1627 for the first time. A window was fixed in a highly insulated clay masonry wall (with declared compressive strength of the clay units 7.5 N/mm2). Resistance class RC 3 was verified for the window, the fixing to the wall and the wall itself.

Performance Evaluation of Construction and Demolition Waste Materials for Pavement Construction in Egypt

AbstractThis paper focuses on the feasibility of using construction and demolition (C&D) waste materials, particularly blends of recycled concrete aggregate (RCA) with recycled clay masonry (RCM), ...

Effect of drywall and brick wall on fire behavior of concrete‐filled steel tube column

The walls around the columns play a decisive role in temperature distribution and mechanical behavior of the column under fire. This study has been conducted to investigate the effects of the presence of two types of walls, including clay masonry wall and dry wall on temperature distribution, and mechanical behaviors of the column compared to the adiabatic condition. A three‐dimensional finite element model was developed and validated using the experimental results of the column under the non‐uniform fire. In this state, three different wall locations around the columns were considered. In modeling clay masonry wall, the thermal properties of the brick block and the cement mortar and in dry wall modeling the thermal properties of Gypsum panel and the applied insulator were extracted from the prior research. The outputs of the model consist of temperature distribution in the cross section of the wall and the column, fire resistance time, and residual strength of the column. The results of the research showed that the presence of brick and dry walls, under the best conditions, increases the resistance time to 46 and 53%, respectively, and residual strength of concrete‐filled steel tube to 27% as compared to the adiabatic condition.

Characterization of the clay masonry units and construction technique at the ancient city of Nippur

Abstract This paper describes a programme of experimental measurements performed in support of a parallel programme of field investigations to evaluate the construction methods used at the site of the ancient city of Nippur. The experimental programme investigated both the mechanical properties and durability of the ancient clay masonry units used in the construction of buildings at Nippur including tests for dimensional consistency and flatness, density, compressive strength, initial rate of water absorption and thermal properties. The test results have been compared with those for modern brick units available nowadays in Iraq and with hard natural stone samples. The field investigations showed that the important buildings were constructed using composite walls inclusion firing clay masonry units with two nominal dimensions (30 × 30 × 7) cm and (30 × 15 × 7) cm (l, w and h). The formulation of working design technique was followed to achieve the member stability under applied loads. Layers of bitumen material were used as a binder for both bed and head joints in order to provide the desired strength level for the masonry wall. The experimental results show that the ancient brick units and stone samples exceed the tolerance and range of dimensions limits recommended by current EN Standards. Lower density values were recorded for the ancient brick units compared with that for both modern clay brick and stone specimens and these values showed agreement with the modern classification of high density (HD) units. Approximately similar values of compressive strength were observed for both ancient brick units and natural stone samples reaching about 17 MPa, whilst modern clay brick samples showed lower compressive strength value suitable for application of partition walls. The initial rate of water absorption increases with an increase of the soaking time, but tends to decrease after 90 min for both ancient and modern brick units. Superior performance in terms of thermal conductivity, thermal resistance and durability under fire action were observed for the ancient brick samples compared with modern clay brick and stone samples.

Study of the block/grout interface in concrete and clay block masonry structures

ABSTRACT This work aims to study the behavior of the block/grout interface for concrete and clay block masonry. This was achieved by push-out and pull-out experimental tests including reinforcement bar in the latter one. The experimental result showed that there is a good bond between the concrete blocks internal faces and the grout, enough to prevent infill-slippage, and that the whole tensile strength of the usual reinforcement bars is achieved provided they are properly anchored. Nevertheless, for clay blocks there is a low bond between the clay blocks internal faces and the grout, allowing the infill-slippage before the reinforcement bars reach their yield stress.

Confinement of Clay Masonry Columns with SRG

In this study, the behavior of clay masonry columns confined by steel reinforced grout (SRG) composite with a natural hydraulic lime mortar is investigated. An experimental study was carried out to understand the behavior of masonry prisms with a square cross-section confined by SRG composite jackets subjected to a monotonic concentric compressive load. Test parameters considered in this study are the density of steel fibers and column corner radius. The effectiveness of the confinement is studied in terms of load-bearing capacity with respect to unconfined columns.

The compressive strength of vertically perforated clay block masonry predicted by means of a unit-cell type numerical simulation tool taking discrete cracking into account

Vertically perforated clay blocks with an excellent ratio of load-bearing capacity to thermal properties are highly sophisticated products, which due to their higher complexity require advanced design concepts for a reliable prediction of performance characteristics. Since the contact between blocks strongly influences the compressive strength, it is insufficient to consider single block strengths. To tackle this challenge, our numerical simulation tool is based on a unit-cell approach with periodic boundary conditions, so interaction between blocks can be considered. An extended finite element approach allows for modelling discrete cracks and, thus, brittle failure modes and compressive strengths can be predicted correctly.

Titelbild: Mauerwerk 3/2017

AbstractTimeless elegance and organic forms – these are the characteristics of a detached house in Medebach. For good reason, the house won first place in the competition ”MASSIVHAUS 2017“. The photo house competition MASSIVHAUS 2017 awards prizes to the most attractive massively built houses in Germany. It looks for examples of innovative and modernistic detached and semi‐detached houses. The only conditions of entry: the house must be built with masonry of calcium silicate, lightweight concrete or aerated concrete blocks or clay masonry units (s. p. 205).(Photo: Massiv mein Haus/Christoph Hesse Architekten)

Sustainable building for the future: Contemporary clay masonry – Resource‐saving building

AbstractClay as a building material has a long tradition in Europe, largely losing its importance with industrialisation. Since the 1980s, clay building activity has steadily increased. Standard guidelines (Lehmbau‐Regeln) introduced in the 1990s, however, appear to be rather too cautious when examined in the light of current research findings on the load bearing capabilities of clay walls. Based on the evidence of historic clay buildings, on structural engineering calculations and building physics – the authors' research supports the assumption that masonry with modern unfired clay bricks has a much higher performance potential than previously assumed, which applies particularly to its sustainability. The biggest apprehension relates to the water‐sensitivity of this building material with regard to structural soundness. This can be countered however with the appropriate construction principles.

In-plane lateral load behaviour of confined masonry walls retrofitted using carbon-fibre-reinforced polymers

This paper investigates the behaviour of retrofitted confined masonry walls subjected to in-plane lateral loads. Three full-scale retrofitted wall assemblies with carbon-fibre-reinforced polymer sheets, consisting of a clay masonry panel, two confining columns and a tie beam, were tested under a combination of vertical load and monotonic pushover up to failure. Wall panels had various configurations, namely solid and perforated walls with window and door openings. The walls were compared to the performance of similar un-retrofitted walls. Experimental results showed the ability of the retrofitting scheme to significantly enhance both the load-carrying capacity and displacement ductility of the walls. An analytical investigation was conducted using the finite element method to build a model capable of simulating the response of the tested walls. The validated model was used to conduct a parametric study on untested design configurations. Alternative retrofitting schemes showed either response or economic merits over the experimentally tested one.

Identification of equivalent mechanical properties for unreinforced masonry walls

Transverse vibrations of beams are an interesting topic for numerous engineering fields. The equations of motion develop under various assumptions and associate a frequency equation. This paper expresses the frequency equation for two specific models, using the Timoshenko beam theory. The first model is a typical cantilever beam with an additional mass attached to the free end. The second model considers a beam partially clamped at the base and with an elastic connection of the additional mass to the free end. The relevance of the used theory is discussed and the importance of each term of the equation is studied. These models find applications in unreinforced masonry. They are indeed fitted to identify, from white noise tests, equivalent mechanical properties of unreinforced load-bearing clay masonry walls including soundproofing devices in the perspective of modelling these elements with a macro-scale approach. Discrepancies with respect to current standards are underscored.

Identification of equivalent mechanical properties for unreinforced masonry walls

Transverse vibrations of beams are an interesting topic for numerous engineering fields. The equations of motion develop under various assumptions and associate a frequency equation. This paper expresses the frequency equation for two specific models, using the Timoshenko beam theory. The first model is a typical cantilever beam with an additional mass attached to the free end. The second model considers a beam partially clamped at the base and with an elastic connection of the additional mass to the free end. The relevance of the used theory is discussed and the importance of each term of the equation is studied. These models find applications in unreinforced masonry. They are indeed fitted to identify, from white noise tests, equivalent mechanical properties of unreinforced load-bearing clay masonry walls including soundproofing devices in the perspective of modelling these elements with a macro-scale approach. Discrepancies with respect to current standards are underscored.

Analysis of Unreinforced Ceramic Wall Panels in the Mounting State

Properties of building materials used for the construction of surrounding structures significantly contribute to creating a healthy and comfortable microclimate inside the rooms. Ceramics belong among materials which exhibit very suitable properties for the formation of the healthy environment. It is also one of the reasons that the fired clay structures remain popular among builders and that recovery of ceramic prefabrication can be seen in the Czech Republic. The important step towards rediscovering the benefits of the prefabricated ceramic elements is forthcoming production of unreinforced ceramic wall panels made of fired clay masonry units with tongue and groove, connected in the bed joints by two-component adhesives. Conventional analytical model for vertical loads is used in the operating state. However, in the transport and mounting state it is a structure stressed by bending in its own plane. This paper is focused on the issue of load-bearing capacity of structures with masonry units cross-sections that are not filled in head joints and therefore are unable to transfer either tensile or compressive stresses. On the segment of the wall panel is performed numerical model analysis using the finite element method in the computing program ANSYS and comparison of this analysis results with the results of the experimental tests.

Characterization and evaluation of rice husk ash and wood ash in sustainable clay matrix bricks

This study analyzes the feasibility of using biomass combustion ash waste (rice husk or wood ash from boards) as secondary raw materials in the manufacture of clay bricks.The ash was characterized using particle size distribution analysis, chemical composition analysis by X-ray diffraction (XRD) and X-ray fluorescence (XRF), thermal analysis, elemental analysis, and scanning electron microscopy (SEM). Either rice husk ash or wood ash was used to replace different amounts (10–30wt%) of clay in brick manufacture. Brick samples were formed by compression at 54.5MPa and fired at temperatures of 900 or 1000°C for 4h, at a heating rate of 3°C/min. The bricks’ properties were compared to conventional products containing only clay and prepared following standard procedures. The bricks’ technological properties depended on type and amount of ash used, and firing temperature. The results showed small variations due to firing temperature. Firing at 1000°C achieved greater densification and thus lower water absorption and higher compressive strength firing at 900°C produced higher porosity, which reduced compressive strength. Based on the results, 1000°C was selected as the optimal firing temperature; and 10wt% rice husk ash and 20wt% wood ash as the optima amounts of biomass ash waste. Moreover, the bricks containing wood ash showed properties similar to the control bricks containing only clay and improved thermal conductivity. Finally, the bricks containing 10wt% rice husk ash and 30wt% wood ash fulfilled standard requirements for clay masonry units.

Compressive Strength of Unburned Clay Masonry

Clay is a traditional construction material which has got to background with introduction of modern materials to building practice. Nowadays, there are two main reasons for unfired clay materials interest grow. First, a clay masonry is in an agreement with sustainable development principles. Second, the unburned clay constructions have positive influence on a human health. However, there is not proper material available for clay constructions design due to lack of proper examination of its mechanical properties. This submission concerns with compressive strength of low walls made of unburned clay.

Three-dimensional micromodel of clay block masonry wall

In designing and implementing earthquake resistance for clay block masonry infill integrated into a structural frame, with or without openings, the infill wall should be taken into account. Presumably, simplified models, acceptable for practical use, could be applied for that purpose. However, the anisotropy of clay block masonry units, masonry mortar joints, and unit contact properties as well as the high variance of material properties limit their ability to describe the actual earthquake resistance of clay block masonry. In this work, we consider a three-dimensional micromodel of a clay block masonry wall, with the inclusion of masonry unit anisotropy and masonry mortar joint and unit contact properties. To avoid the excessive calibration procedure of the wall micromodel, the wall constituents were calibrated separately beforehand, which resulted in a high correlation of computational and experimental results without further need for calibration. Using a calibrated micromodel, the influence of variance in material properties on the wall's resistance was investigated. The influence was showed not to be negligible, which may significantly affect the presumed behaviour of the whole structure.

Three-dimensional micromodel of clay block masonry wall

Three-dimensional micromodel of clay block masonry wall