Moisture-induced static and cyclic properties of sisal fiber reinforced soil for resilient earthen construction

Abstract: This study focused on investigating strength properties of the randomly distributed sisal fiberreinforced soil subjected to applied static and dynamic loading conditions. Series of static laboratory tests were performed to determine compaction characteristics, compressive and interfacial shear strength properties of the composite. Dynamic properties were investigated by subjecting the composite to cyclic loading under undrained soil condition. The moisture induced properties were established by performing matric suction and desiccation cracking tests. The effects of soil matrix density, moisture content and fiber properties (content, length and surface coating with gum rosin) on the mechanical and macro structural properties were determined from the laboratory experiments. Furthermore, unconfined compression and tensile tests were performed on the lime-fly ash stabilised soil composite to investigate the potential strength improvements. The synergic effects of pre-compression and moisture exposure on the mechanical performance of the stabilised composite were also investigated to establish the resilience of the material. The strength of sisal fiber-reinforced adobe masonry construction was eventually determined by performing series of laboratory tests on the reinforced masonry elements and structures. Finite-Element modelling of masonry construction was employed to validate results from the experiments. ..D.Phil. (Civil Engineering Science

Role of fiber inclusion in adobe masonry construction

Adobe masonry construction constitutes a notable portion of the buildings in both urban and rural areas in less developed countries. Seismic performance of adobe buildings is poor, and low-cost retrofitting measures are required to enhance the resilience of such buildings during an earthquake. In this study, mechanical properties of fiber reinforced and unreinforced adobe masonry were investigated. Sisal fibers with length of 25 mm were used as reinforcing elements for mortar and adobe bricks at a fiber content of 0.75%. A series of laboratory tests were performed on masonry triplets, couplets and prisms to determine shear strength, tensile resistance and compressive strength, respectively. Uniaxial compression and diagonal compression shear tests were performed on wallets and wall panels, respectively to determine compressive strength and shear strength of the adobe masonry. Finite element linear elastic analysis was conducted using ANSYS Finite-Element code to evaluate the stress state of loaded wall panels. The structural design of adobe masonry walls was carried out according to BS5628 and Eurocode 6 standards, by utilising material properties acquired from the experiments. The results showed that fiber inclusion in the mortar caused an increase in tensile strength of 31%, friction coefficient of 22%, and prism compressive strength of 25% compared with unreinforced mortar. The reinforced wallets exhibited a twofold increase in compressive strength while reinforced wall panels indicated threefold increase in shear strength. The stress state in the reinforced and unreinforced wall panels was not a pure shear state and was better described by RILEM recommendations. The allowable vertical load resistance was found to be 40 kN/m and 100 kN/m for unreinforced and reinforced walls, respectively. The allowable lateral shear resistance was found to be 25 kN/m and 80 kN/m for unreinforced and reinforced walls, respectively. Reinforced masonry elements exhibited considerable ductility and unreinforced masonry elements showed brittle behaviour

Investigation of Methods and Motives for Water Theft in A Suburb Township

Theft of water from water urban authorities is fast growing to a level of severe concern with the perpetrators moving several steps ahead of water utility companies. Consequently, counter-measures that are in tandem with the ever-changing business environment are greatly desired to empower water utility companies with effective methods to prevent the ever-growing water theft challenges.  To ascertain the significance of the methods used to steal water, a study was undertaken in one of the suburbs of Blantyre in Malawi. A questionnaire survey was employed to elicit data on the methods used for stealing water and the motivations behind the thefts.  The results indicated that the most prevalent method for stealing water was bursting pipes followed by vandalizing. Poor service was the most compelling reason behind water theft from the water utility company. The severity indices for the constructs used to steal water in this study can be used to design intervention frameworks for water utility companies. Additionally, iso-theft-index maps can be produced for suburb areas where water utility companies have water distribution networks to guide surveillance operations. Keywords: water theft methods, non-revenue water, challenges, Malawi DOI: 10.7176/JEES/12-8-04 Publication date:August 31st 202

Strength of materials and masonry structures in Malawi

Strength properties of masonry materials commonly used for housing construction in formal and informal settlements in Malawi are investigated by means of laboratory testing, conducted on masonry prisms and panels. The tests are aimed at simulating actual field conditions and construction practices in the country. Based on observations from previous field surveys, specimens were prepared by local artisans using local commercially-produced bricks and various mortar types which were cured in uncontrolled conditions. The results reveal that the behaviour of the masonry in compression is governed by the low compressive strength of the bricks. It was also found that it is the quality of the brick-mortar bonding that governs the in-plane shear and out-ofplane flexural behaviour, which are critical for the resistance to horizontal loading, such as the earthquake action

Building classification and seismic vulnerability of current housing construction in Malawi

Malawi experiences multiple natural hazards with severe effects on the population and the economy, amid challenging conditions of a rapidly degrading environment and limited resources. Recently, the Government of Malawi has taken the first major step to implement the national disaster risk management policy in close partnership with international aid organisations. Local communities and housing conditions are the key components for achieving sustainable development and for reducing the impact of natural disasters. This study presents the results of a recent building survey conducted in Central and Southern Malawi to understand the current situation of housing construction in Malawi more accurately. The survey focussed on the informal housing construction sector with respect to seismic vulnerability. The observed characteristics of local buildings are compared with the global building classifications that are widely used for evaluating seismic vulnerability of structures. Building typologies that are defined based on international building databases and those observed in the field are different, highlighting the importance of obtaining more realistic building information for seismic risk assessment

Mechanical performance and physico-chemical properties of limestone calcined clay cement (LC3) in Malawi

Malawi is one of the least-developed countries in Sub-Saharan Africa with disaster-prone housing infrastructure characterized by poor construction materials. Therefore, there is a need to provide resilient and cost-effective materials, such as limestone calcined clay cement (LC3). However, the exploitation of LC3 in Malawi is limited due to a lack of mineralogical information about the clays and limestone and related strength and durability when used as a cementitious material. In this study, the strength and physico-chemical properties of LC3 systems with 50% and 40% clinker contents (LC3-50 and LC3-40) were investigated. Cement mortar specimens were prepared at water to cement (w/c) ratios of 0.45, 0.5, and 0.6 with varying calcined clay (CC) to limestone (CC/LS) ratios (1:1, 2:1, and 3:1). The effects of CC/LS ratio on the fresh properties, strength, and durability were investigated. The results showed that specimens with 40% Portland cement replacement levels (LC3-40) exhibited higher standard consistency (up to 45%) than LC3-50, porosity in the range of 8.3–13.3%, and maximum water uptake in the range of 3.8–10.9%. On the other hand, LC3-50 samples offered the highest strength of approximately 40 MPa, complying with requirements for pozzolanic cementitious materials, whereas LC3-40 conforms to the strength requirements for masonry cements. This work shows that LC3 systems can be manufactured with local clays and limestone available in Malawi, and used as a sustainable construction material to mitigate carbon emissions as well as boost the local economy

Fragility curves for non-engineered masonry buildings in developing countries derived from real data based on structural surveys and laboratory tests

Malawi is located within the southern branch of the active East African Rift System, where earthquakes of moment magnitude (Mw) 7.0 or greater can occur along major faults. The majority of dwellings in the country are non-engineered unreinforced masonry constructions, built by local artisans with little input from engineers. These constructions are highly vulnerable to seismic events due to poor-quality materials and lack of construction detailing. This study presents a new methodology to assess the seismic fragility curves of typical dwellings located in the Central and Southern Malawi. On-site inspections of buildings are carried out to assess geometrical and structural features of 646 façades, and an experimental campaign is performed to characterise the mechanical properties of local construction materials. The collected data allow the identification of different building typologies in terms of quality of materials and construction techniques. The critical failure modes for each of the inspected façade at their ultimate limit state are evaluated analytically. Damage limit states are defined and adopted to derive simplified Static Push-Over (SPO) curves, transformed into incremental dynamic analysis (IDA) curves by using SPO2IDA. The IDA curves are then used to obtain fragility curves for the specific damage limit states. The fragility curves presented herein are the first to be calculated for these building typologies, based on local data, and unfortunately, they show that buildings in Malawi are far more vulnerable to earthquakes than estimated from previously available international reference data. The fragility curves developed in this study may prove useful for assessing the seismic risk of these building typologies in Malawi and other East African countries

Seismic fragility models for typical non-engineered URM residential buildings in Malawi

Malawi is an earthquake-prone country that lies within the East African Rift. A large proportion of its population lives in non-engineered single-storey constructions made of clay bricks and low-strength mortar. Walls are typically single-skin and often lack adequate wall-to-wall connections, leaving them vulnerable to seismic actions. This work reports a comprehensive study on the seismic fragility of unreinforced masonry buildings of the Malawi housing stock. The probability of exceeding different levels of in-plane/out-of-plane damage is estimated by considering the aleatory and epistemic uncertainties of the problem. Inter-building and intra-building variability are accounted for by adopting material test results and building survey data collected in Malawi. The in-plane capacity of building walls is calculated through a finite element model that considers the orthotropic properties of masonry. The out-of-plane capacity is computed using an analytical solution, developed for walls in one way bending. In addition, record-to-record variability is considered. The new country-specific fragility models result more conservative that global estimates, which reflects the high vulnerability of Malawian masonry buildings. These fragilities can be integrated into catastrophe modelling platforms for earthquake risk assessment in Malawi and in the wider East African region