In-plane structural response of single-storey unreinforced walls constructed using alternative masonry units

Shiso, Etobo Prince (2019-04)

Thesis (MEng)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: Studies on alternative masonry units (AMUs) at Stellenbosch University seek to reduce the environmental impact that conventional masonry units (concrete masonry units [CMUs] and fired clay) cause, by developing masonry units that are environmentally friendly, socially acceptable and structurally sound. The introduction of AMUs in the construction industry as construction components for low-income housing depends on the determination of their minimum mechanical specifications. The three AMU types being investigated include compressed stabilized earth blocks (CSEBs), Adobe blocks, and alkali-activated concrete blocks (AACBs). Various experimental tests are being conducted in the laboratory on AMUs as well as concrete masonry blocks (CMUs), which aim to provide sufficient information on the technical performances of these masonry units. Further, as certain areas in South Africa have been identified to be at risk of low to moderate seismic activities, the South African loading code requires that single storey masonry structures be designed for seismic actions. To use AMUs as construction components for such structures necessitates, as part of the determination of mechanical specifications, that an investigation be carried out on the seismic behaviour of a masonry structure constructed with AMUs. Such investigation is often conducted in a laboratory setting by subjecting masonry walls of pre-defined geometry and with restraint, as in a structural building system, to similar loading conditions a wall would experience during an earthquake. In this study, in-plane shear-compression tests on large scale masonry wall, constructed with CMUs and AMUs respectively, are conducted to determine the in-plane structural response of these walls. This was achieved by designing and constructing an appropriate test set-up capable of undertaking such tests, and by manufacturing a large quantity of masonry units. Characterisation tests were performed on masonry units as well as wallets to determine their respective compressive strength and modulus of elasticity. Density tests were also performed on masonry units, the results of which are within the range of values provided in literature. Performed at various stages on the experimental programme and at different ages of masonry units, an increase over time in the strength and stiffiness was observed in the four different masonry units. While AACBs showed a higher compressive strength than the CMUs, they had a lower modulus of elasticity. On the other hand, the Adobe blocks had the lowest compressive strength and modulus of elasticity, and exhibited little increase of these properties over time. Difficulties were encountered while performing tests on masonry wallets as adequate boundary conditions were required at the top and bottom of the specimens. However, sufficient results were obtained which were used to determine the pre-compression levels applied on top of the wall specimens. Further, two test set-up configurations for the in-plane shear-compression tests were adopted based on the boundary conditions (BC) the wall was subjected to, i.e. fixed-free and fixed-fixed BC. The test results of AMU walls indicated that with the fixed-free BC, the specimen exhibited a rather large lateral capacity as compared to the results from a fixed-fixed BC configuration. Although difficulties were encountered while performing tests on CMU wall specimens, it was found that with few adjustments of the test set-up these tests could be performed successfully. Forming part of the technical performances of the masonry units, the results obtained and presented in this study can further be used in forthcoming studies for validation of numerical modelling and, ultimately, the determination of minimum mechanical specifications of AMUs.

ENGLISH ABSTRACT: Studies oor alternatiewe messelwerkeenhede (AME's) by Universiteit Stellenbosch word gedoen in 'n poging om die omgewingsimpak te verminder wat deur konvensionele messelwerkeenhede (betonmesselwerkeenhede [BME's] en gebrande klei stene) veroorsaak word deur messelwerkeenhede as boukomponente te ontwikkel wat omgewingsvriendelik, sosiaal aanvaarbaar en struktureel betroubaar is. Die benuttiging van AME's in die boubedryf as boukomponente vir laeinkomste-behuising hang van die bepaling van hul minimum meganiese spesifikasies af. Die drie soorte AME's wat ondersoek word, sluit in saamgeperste gestabiliseerde grondblokke (SSGB, Adobe-blokke en alkali-geaktiveerde betonblokke (AGBB's). Verskeie eksperimentele toetse is op AME's asook BME's in die laboratorium uitgevoer met die doel om voldoende inligting oor die tegniese verrigting van hierdie messelwerkeenhede te verskaf. Op grond van waarnemings dat sekere gebiede in Suid-Afrika 'n risiko van lae tot matige seismiese aktiwiteite loop, vereis die Suid-Afrikaanse laskode dat enkelvlak-messelwerkstrukture vir seismiese aksies ontwerp moet word. Om AME's as boukomponent vir sodanige strukture te gebruik, noodsaak, as deel van die bepaling van meganiese spesifikasies, 'n ondersoek na die seismiese gedrag van 'n messelwerkstruktuur wat met AME's gebou is. Sodanige ondersoek word dikwels in 'n laboratoriumomgewing uitgevoer deur messelwerkmure met 'n voorafbepaalde geometrie en met randvoorwaardes, soos in 'n strukturele boustelsel, aan soortgelyke lastoestande te onderwerp as wat 'n muur tydens 'n aardbewing sou ervaar. In hierdie studie is in-vlak-skuifdruktoetse op grootskaalse messelwerkmure met onderskeidelik BME's en AME's uitgevoer om die in-vlak-strukturele reaksie van hierdie mure te bepaal. Dit is bereik iv deur die ontwerp en samestelling van 'n geskikte toetsopstelling en die vervaardiging van 'n groot hoeveelheid messelwerkeenhede. Karakteriseringstoetse is op messelwerkeenhede asook klein blokmure uitgevoer om hul druksterkte en elastisiteitsmodulus te bepaal. Digtheidstoetse is ook op messelwerkeenhede uitgevoer, waarvan die resultate binne die omvang was van waardes wat in die literatuur beskikbaar is. In die toetse, wat in verskillende fases van die eksperimentele program en op verskillende ouderdomme van messelwerkeenhede uitgevoer is, is 'n toename met verloop van tyd in die sterkte en styfheid in die vier verskillende messelwerkeenhede waargeneem. Alhoewel AGBB's 'n hoër druksterkte as BME's getoon het, het dit 'n laer elastisiteitsmodulus gehad. Aan die ander kant het die Adobe-blokke die laagste druksterkte en elastisiteitsmodulus gehad, en min toename in hierdie eienskappe met verloop van tyd getoon. Probleme is ondervind met die uitvoer van toetse op klein blokmure, aangesien voldoende randvoorwaardes (RV's) aan die bo- en onderkante van die monsters nodig was. Voldoende resultate is egter verkry, wat gebruik is om die voorspanningsvlakke te bepaal wat op die bokant van die muurmonsters toegepas is. Twee toetsopstellingskonfigurasies vir die in-vlak-skuifdruktoetse is gebruik op grond van die RV's waaraan die muur onderwerp is, naamlik vaste-vry en vaste-vaste RV's. Die toetsresultate van AME-mure het getoon dat met die vaste-vry RV, die toetsopstelling 'n redelike groot laterale kapasiteit getoon het in vergelyking met die resultate van 'n vaste-vaste RV-konfigurasie. Alhoewel probleme ervaar is toe die toetse op BME-muur toetsopstellings uitgevoer is, is gevind dat hierdie toetse met sukses uitgevoer kan word met min verstellings van die toetsopstelling. Die resultate wat in hierdie studie verkry is en aangebied word, wat deel vorm van die tegniese evaluering van messelwerkeenhede, kan in toekomstige studies gebruik word vir data vir numeriese modellering en, uiteindelik, die bepaling van minimum meganiese spesifikasies van AME's.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/105889
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