Load-bearing Masonry Buildings Research Articles

Seismic Evaluation and Methods of Rehabilitation of Old Masonry Buildings in the Bay of Kotor (Montenegro)

Old load-bearing masonry buildings exist all around the world. The cultural and architectural heritage value of these buildings and the consciousness of public opinion have led to a need for safeguarding and preservation policies for these architecturally valued buildings and urban aggregates. This paper provides the information on the constructive and structural details of the old buildings dating from the 12th to 19th century in the Bay of Kotor and discusses their seismic and dynamic behaviour, identifying structural fragilities and consequently their vulnerability. One factor that significantly influences the seismic vulnerability is the quality of workmanship, which has, in conjunction with the lack of maintenance of the buildings, increased the seismic vulnerability of heritage masonry buildings in general. Masonry constructions represent an important part of Montenegrin Architectural Heritage. The existing heritage masonry buildings in the Bay of Kotor suffered major earthquakes with repairs ranging from minor repairs to partial rebuilding. No degree of seismic resistance to any potentially severe shaking levels has been determined for the surviving buildings. The lack of strategies, policies and actions by the institutions responsible for this domain in the course of the second half of the 20th century drove these buildings to the state of serious degradation. The adoption of intrusive and inadequate rehabilitation and conservation practices, using new materials and construction techniques on structural and nonstructural elements, has strayed away from traditional knowledge and practices. The main objective of this research is understanding the whole building process that underpins a historical construction, and building techniques and other methods applied in building the architectural and engineering structures constituting the present Historical Heritage in Montenegro.

Structural conditioning factors of the installation of rooftop hvac equipment on existing load-bearing masonry buildings: case study

El interes creciente por dotar de unas adecuadas condiciones de climatizacion a los edificios de uso publico que no disponian en origen de estas conlleva, en muchos casos, a la necesidad de implantar instalaciones de climatizacion de dimensiones y pesos significativos. Maxime en el caso de edificios situados en nucleos urbanos, la ausencia de superficie disponible para implantar dichas instalaciones ha motivado que se dispongan en sus cubiertas. A partir del caso de estudio de un edificio notable de fabrica de ladrillo del casco historico de Madrid, se analizan los condicionantes estructurales que supone la implantacion de importantes aparatos de climatizacion en la cubierta de edificios existentes de muros de carga, asi como las tipologias de actuacion de acondicionamiento estructural necesarias al efecto. Asimismo, el estudio realizado se centro, por una parte, en el analisis de la repercusion de la disposicion de nuevas cargas sobre las condiciones de seguridad previas de la estructura y la necesidad de adoptar en esta medidas de refuerzo que permitan asegurar unas adecuadas condiciones de seguridad futuras y, por otro lado, en el analisis de los condicionantes a tener en cuenta en el diseno de la estructura auxiliar de apoyo y sujecion de dichas instalaciones .

Strength development and masonry properties of geopolymer stabilised soil-LPC (lime-pozzolana cement) mixes

Soil-based blocks and binders have emerged as sustainable alternatives to masonry units, and alkali-activated polymers (geopolymers) are being studied as alternatives to cement. This study attempts to stabilise soil using a combination of geopolymerisation and hydration. Strength gain and applicability of soil-based lime-pozzolana cement (LPC)-industrial by-products-geopolymer mortar have been studied. In order to optimise usage of alkaline materials, a series of parametric studies were carried out. A combination of LPC and flyash led to wet compressive strength of around 7.0 MPa, while a combination of LPC and ultra-fine slag resulted in strength of nearly 18.0 MPa. One of these mixes was used to develop bricks in order to investigate its masonry properties. Besides obtaining masonry strength parameters such as shear strength, bond strength and tensile strength for mortars, an attempt has additionally been made to obtain masonry prism strength and modulus of elasticity of prism assemblage. The masonry properties were found to be satisfactory for construction of low-rise, load-bearing masonry buildings.

Impact of the Crossrail tunnelling project on masonry buildings with shallow foundations

Building monitoring and protection are important components of underground projects in urban areas. Typically the procedures applied for the assessment of settlement-induced damage to buildings are based on simplified assumptions that do not take into account soil–structure interaction. Assessment methods based on the relative stiffness between the structure and the soil exist, but they are rarely applied in practice due to concerns about the accuracy and reliability. The primary aim of this work is to use the large amount of monitoring data provided by the Crossrail project in London to improve understanding of building performance and existing damage assessment methods. The paper gives an initial overview of the available monitoring data by presenting four representative case studies for load-bearing masonry buildings on shallow foundations. Structural data are then used to evaluate the consistency of predictions produced by different relative stiffness formulations. The results show the effect of building stiffness on the soil surface settlements and clarify the effects of various assumptions made during prediction. The conclusions highlight opportunities to improve prediction procedures and the need for more detailed monitoring data for future tunnelling projects.

Failure analysis of earthen, masonry and concrete buildings during the 2017 Tripura earthquake

This paper reports on an evaluation of failures of non-engineered earthen buildings, timber-framed buildings with bamboo matting, unreinforced load-bearing masonry buildings and framed reinforced-concrete structures with brick infill during the 5·7 magnitude 2017 Tripura earthquake in India. Field observations showed that some of the concrete and masonry buildings, and many of the non-engineered earthen buildings in the Dhalai and Unokoti districts, suffered damage due to this moderate earthquake. Out-of-plane failure, corner cracks, shear cracks and damage of infill wall materials were among the predominant forms of seismic damage. On the basis of the analysis, some remedial measures are proposed in this paper, which will require future research and testing.

Seismic Evaluation and Strengthening of an Existing Masonry Building in Sarajevo, B&H

A significant number of old unreinforced load-bearing masonry (URM) buildings exist in many countries worldwide, but especially in Europe. In particular, Bosnia and Herzegovina has an important stock of masonry buildings constructed from the 1920s until the 1960s without application of any seismic code, due to their nonexistence at that time. With the 1963 Skopje earthquake, this class of buildings were shown to be rather vulnerable to seismic actions, which exhibited serious damage. This article assesses the seismic vulnerability of a typical multi-storey residential unreinforced load-bearing masonry building located in the heart of Sarajevo, which may be exposed to an earthquake of magnitude up to 6 by Richter’s scale. The buildings of this kind make up to 6% of the entire housing stock in the urban region of Sarajevo, while in Slovenia this percentage is much higher (around 30%). The analysis of a typical building located in Sarajevo revealed its drawbacks and the need for some kind of strengthening intervention to be implemented. Additionally, many structures of this type are overstressed by one to two additional floors (not the case of the analyzed structure) constructed from 1996 onwards. This was due to the massive population increase in the city center of Sarajevo and further increased the vulnerability of these buildings.

Parametric Study on Seismic Rehabilitation of Masonry Buildings Using FRP Based upon 3D Non-Linear Dynamic Analysis

Unreinforced load-bearing masonry (URM) buildings represent a significant portion of the non-engineered old buildings in many developing countries aiming to reduce the construction cost. The walls of those buildings are developed to resist gravity loads. Lateral loads induced by earthquakes or wind may cause severe their damage. In the current study, a numerical investigation is carried out for a seismic assessment of a typical four-story, load-bearing building in Giza, Egypt. The full 3D nonlinear dynamic analysis is carried out using the Applied Element Method (AEM), which proved to be efficient in such case where partial or total collapse is expected. The study includes two earthquake zones in Egypt called zone (3) and zone (5B), which are the actual studied building seismic zone and the highest seismic activity zone in Egypt, respectively. Carbon fiber reinforced polymers (CFRP) laminates with different thicknesses and different configurations are used in strengthening unreinforced masonry walls to study the efficiency of the proposed rehabilitation technique on a realistic structure.

Seismic and Energy Retrofit of the Historic Urban Fabric of Enna (Italy)

This paper exemplifies several methods for retrofitting existing housing through four case studies, representative of the historical centre of Enna, a small town in Sicily, according to the requirements of static safety, typological adaptation and indoor comfort. These buildings were mostly built in the nineteenth century, up to three floors based on load-bearing masonry, iron joists and hollow tile floors and wooden roofs. A typological and construction analysis of these buildings was carried out to identify the stratigraphy of the different technical elements. Static and energy audits had been previously undertaken to understand the gap between the current state of the buildings and Italian standards and to develop appropriate interventions taking into account the site characteristics and the energy and seismic risk class pre- and post-retrofit intervention. The analyses and the retrofit interventions were performed in compliance with Italian standards and laws and strove to reach the minimum level. The study supports the planning of structural and energy retrofit interventions designed for historic load-bearing masonry buildings. Finally, the study simulates a strategy of action to provide subsidies and tax relief related to effective seismic and/or energy improvement that could be relevant for owners/builders as well as for local authorities.

Proposals for seismic retrofitting of timber roofs to enhance their in-plane stiffness and diaphragm action at historical masonry buildings in Cairo

Abstract The in-plane stiffness of flat roofs plays crucial role in the structural stability and safety of historical load bearing masonry buildings under lateral hazardous loads. For decades, many restorers of historical buildings used to provide the original timber roofs with rigid diaphragms action using modern engineering systems; such as building reinforced concrete (R.C.) thin slabs. The present research studies analytically the installation of simple and robust timber bracing system above timber boards and under flooring layers of timber flat roofs; to improve the seismic behavior and stability of their historical load bearing masonry buildings in Cairo. The study will evaluate among various alternatives of bracing systems using numerical modelling techniques of computer software that applies Finite Element (F.E.) method. The research applies the numerical investigation to one of archaeological buildings in Cairo from Ottoman era, which is the “Sabil” of “Khusraw Pasha” (1535 A.D./942 A.H.). The timber x-bracing system provides remarkable results relative to rigid diaphragm and steel bracing for seismic retrofitting of historical timber roofs.

Seismic vulnerability of historic masonry buildings: a case study in the center of Lucca

The Italian territory, as that of many other European countries, is currently defined as a total seismic territory. The cultural heritage is generally made of historic constructions of load-bearing masonry buildings, organized in complex aggregates. These structures, due to their intrinsic vulnerability and their reciprocal interactions, are particularly susceptible to local or global collapses in case of seismic loading.This paper aims at analyzing the seismic vulnerability of the masonry aggregate of Civitali Insitut, located in the city center of Lucca (Italy). After a description of the complete knowledge process done, based also to partially destructive onsite tests of double flat-jacks, the static and seismic assessment of the complex has been discussed analyzing both local mechanisms and global behavior by assuming different structural configurations according to the level of connections between structural elements. Particular attention has been paid to the study of the vaults covering the ground floor. The analyses have highlighted some critical issues typical of that type of building structures such as the weak walls’ connections and the poor quality of the masonry type.

A simplified methodology for the seismic assessment of masonry buildings with RC slabs

The present paper aims to contribute to the knowledge concerning the seismic assessment of load bearing masonry buildings with reinforced concrete slabs. The final goal of the present research was to propose a simple, yet accurate, methodology to assess the seismic safety of existing masonry buildings. The methodology here presented was based on the so-called ICIST/ACSS methodology with major improvements such as the extension to load bearing masonry wall buildings and the consideration of the effects of one of the most common strengthening solutions for masonry walls, here referred to as reinforced plastering mortar, as well as the possibility of considering four levels of increasing refinement: global, by alignment, by wall panel and by wall element. An extended research was performed on the existing methodologies to evaluate the seismic structural risk of load bearing masonry buildings, briefly describing methodologies similar to the one proposed, namely all of those that have in common the fact that they are based in the physical comparison between the resisting and acting shear forces at all storeys and along the two orthogonal horizontal directions. A case study is presented to check the applicability of the proposed methodology. The case study showed that the proposed methodology is relatively simple to apply and has a sufficiently good accuracy when compared with alternative methodologies. The degree of refinement of the analysis (global, by alignment, by wall panel and by wall element) must be taken into consideration and successively more complex analyses may be required when the results of simpler analyses are inconclusive.

Seismic vulnerability of traditional masonry building a case study of Byasi, Bhaktapur

Historic buildings of Nepal are mainly constructed from masonry structure. Since masonry structures are weak in tension which leads to the failure of structure. So, to avoid possible damage in environment lives and property it is urgent to conduct vulnerability assessments. Seismic vulnerability of historic masonry buildings constructed in Bhaktapur at Byasi area is carried out for the case study. Five load bearing masonry buildings were selected out of 147 buildings considering opening percentage, storey and type of floor for modeling in SAP 2000 V10 Various methods of rapid visual screening (FEMA 154, EMS 98) are used to determine the vulnerability of the selected building. The Selected Building response is carried out by linear time history analysis. The seismic vulnerability of masonry structures is determined in terms of fragility curves which represent the probability of failure or damage due to various levels of strong ground motions for different damage state slight, moderate, extensive and collapse. From the result of Rapid Visual Screening (RVS) and Fragility curves of the buildings it is found that whole, buildings are found vulnerable from future earthquake.

The development of a seismic vulnerability assessment methodology for contemporary loadbearing masonry buildings in the Maltese Islands

This study focuses on the development of a seismic vulnerability assessment method adapted for use on the contemporary loadbearing masonry building typology present in the Maltese Islands. This assessment methodology refers to existing vulnerability assessment methodologies, preand post-earthquake survey methods and manuals developed for different Italian regions. The methodology refers to seismic vulnerability characteristics present in the building typology under study. The method was tested in a pilot study in Msida and then in the test sites of Xemxija and Nadur covering 183 individual buildings. The assessment was carried out through site surveys and information extracted from the Development Permit Drawings. FEMA 154 and a GNDT level II seismic vulnerability evaluation were carried out to assess the differences between the methods when these are applied to the typology analysed and also to assess the merits of the proposed new method developed for the Maltese Islands.

An inventory of unreinforced load-bearing stone masonry buildings in New Zealand

Almost all unreinforced stone masonry (URSM) buildings in New Zealand were constructed between 1860 and 1910, typically in regions where natural stone was sourced from local quarries, fields and rivers. These buildings form an important part of the country’s architectural heritage, but the performance of URSM buildings during earthquake induced shaking can differ widely due to many aspects related to the constituent construction materials and type of masonry wall cross-section morphology. Consequently, as a step towards gaining greater knowledge of the New Zealand URSM building stock and its features, an exercise was undertaken to identify and document the country-wide URSM building inventory. The compiled building inventory database includes: (i) general building information, such as address, building owner/tenant and building use; (ii) architectural configuration, such as approximate floor area, number of storeys, connection with other buildings, plan and elevation regularity; and (iii) masonry type, such as stone and mortar types, wall texture and wall cross-section morphology. From this exercise it is estimated that there is in excess of 668 URSM buildings currently in existence throughout New Zealand. A large number of these vintage URSM buildings require detailed seismic assessment and the implementation of seismic strengthening interventions in order to conserve and enhance this component of New Zealand’s cultural and national identity. The entire stock of identified buildings is reported in the appended annex (688 total), including 20 URSM buildings that were demolished following the Canterbury earthquake sequence.

Low embodied energy cement stabilised rammed earth building—A case study

Rammed earth is a monolithic construction and the construction process involves compaction of processed soil in progressive layers in a rigid formwork. Durable and thinner load bearing walls can be built using stabilised rammed earth. Use of inorganic additives such as cement for rammed earth walls has been in practice since the last 5–6 decades and cement stabilised rammed earth (CSRE) buildings can be seen across the world. The paper deals with the construction aspects, structural design and embodied energy analysis of a three storey load bearing school building complex. The CSRE school complex consists of 15 classrooms, an open air theatre and a service block. The complex has a built-up area of 1691.3m2 and was constructed employing manual construction techniques. This case study shows low embodied energy of 1.15GJ/m2 for the CSRE building as against 3–4GJ/m2 for conventional burnt clay brick load bearing masonry buildings.

Influence of Joint Thickness and Mortar-Block Elastic Properties on the Strength and Stresses Developed in Soil-Cement Block Masonry

Soil-cement blocks are employed for load bearing masonry buildings. This paper deals with the study on the influence of bed joint thickness and elastic properties of the soil-cement blocks, and the mortar on the strength and behavior of soil-cement block masonry prisms. Influence of joint thickness on compressive strength has been examined through an experimental program. The nature of stresses developed and their distribution, in the block and the mortar of the soil-cement block masonry prism under compression, has been analyzed by an elastic analysis using FEM. Influence of various parameters like joint thickness, ratio of block to mortar modulus, and Poisson’s ratio of the block and the mortar are considered in FEM analysis. Some of the major conclusions of the study are: (1) masonry compressive strength is sensitive to the ratio of modulus of block to that of the mortar ( Eb / Em ) and masonry compressive strength decreases as the mortar joint thickness is increased for the case where the ratio of blo...

Earthquake Design of Unreinforced Masonry Residential Buildings up to 15 Metres in Height

The paper summarises the results of a displacement-based assessment (DBA) of the seismic capacity of typical load-bearing unreinforced masonry buildings between two and five storeys in height across a range of site sub-soil classes (B to D) and earthquake hazard factors (0.05 to 0.12), covering all of the capital cities and major regional centres in Australia. The study found that the DBA for out-of-plane bending of walls in the top storey of buildings identified far fewer cases of failure than did a traditional strength-based assessment. A similar trend was observed for the DBA for in-plane shear of walls at the ground storey of buildings. The DBA implied, for all practical purposes, that typical walls will have the in-plane shear displacement capacity to withstand the earthquake induced loads and displacements for any site soil conditions, and earthquake hazard factor up to 0.12. This contrasts with the corresponding strength-based calculations, which identified significant numbers of cases where failure would occur.

Earthquake Shear Load in Load-Bearing Masonry Buildings

Load-bearing masonry buildings are composed of concrete slabs and supporting masonry walls, and in Australia usually incorporate slip joints in the interfaces between walls and slabs for serviceability reasons. The apparent conflicting requirements of the slip joints, to slip under long-term loads and to transmit short-term loading from wind and earthquake actions, together with the lack of attention to the design of slip joints, make slip in the joints likely to occur when the building is subjected to a lateral loading. Joint slip leads to a redistribution of loading in the building wall system, resulting in wall shear loads different from that determined using the current standard elastic design procedures. Redistribution of loading may be also caused by softening of the masonry. This paper has assessed the realistic response of various load-bearing masonry buildings, including the potential for slip in the joints and softening of the masonry, and evaluated the level of wall shear load deviations resulting from the application of current design procedures. Analyses of the buildings, using non-linear static and dynamic finite element models, have indicated that joint slip may occur in buildings subjected to earthquake loading. The application of current elastic design procedures, which do not account for loading redistribution, resulted in major wall shear load deviations, such as overestimations of up to +75% and underestimations of up to-62%. It was therefore concluded that improvements in the current design procedures are required for a more accurate evaluation of wall shear loads in load-bearing masonry buildings subjected to the lateral loading.

Engineered design of masonry buildings: fifty years development in Europe

AbstractThis paper describes the development of the structural design of multi‐storey, load‐bearing masonry buildings in the United Kingdom and the European Community over the second half of the 20th century. Tall buildings of this type had fallen into disuse in the first half of the century as the empirical rules governing their design led to walls of excessive thickness. The application of engineering principles to load‐bearing masonry was pioneered in Switzerland, and in the United Kingdom a rudimentary code of practice appeared in 1949. This was used for the design of buildings in the following decade, but its limitations led to research work on a number of key problems, and eventually to the publication of a completely new code, based on limit state principles, in 1978. Parallel work by international organizations and later in the European Union led to the publication of a draft code, intended for use in countries of the EU in 1995. Essential problems of overall stability and safety and the design of walls in compression and under combined compressive and lateral loads have been addressed. The paper summarizes the approach to these problems which has been adopted in the UK and EU codes with reference to relevant research work, in particular to projects with which the author has been associated.

Embodied energy of common and alternative building materials and technologies

Considerable amount of energy is spent in the manufacturing processes and transportation of various building materials. Conservation of energy becomes important in the context of limiting of green house gases emission into the atmosphere and reducing costs of materials. The paper is focused around some issues pertaining to embodied energy in buildings particularly in the Indian context. Energy consumption in the production of basic building materials (such as cement, steel, etc.) and different types of materials used for construction has been discussed. Energy spent in transportation of various building materials is presented. A comparison of energy in different types of masonry has been made. Energy in different types of alternative roofing systems has been discussed and compared with the energy of conventional reinforced concrete (RC) slab roof. Total embodied energy of a multi-storeyed building, a load bearing brickwork building and a soil–cement block building using alternative building materials has been compared. It has been shown that total embodied energy of load bearing masonry buildings can be reduced by 50% when energy efficient/alternative building materials are used.