Feasibility of 3DP cob walls under compression loads in low-rise construction

The rapid adoption of 3D-printing (3DP) technologies in construction, combined with an increased willingness to reduce environmental impact, has facilitated reapproaching earth materials for modern building industry. The feasibility of 3DP earth-based materials has been under investigation in recent years, with a particular focus on cob due to its favourable characteristics toward the 3DP process. Yet, there is a lack of definitive information on the construction of 3DP cob. Hence this paper investigates the structural feasibility of 3D-printed cob walls in low-rise buildings. The investigation involved experimental compression tests on 3DP cob samples to obtain key mechanical properties including the compressive strength and elastic modulus. These properties were then used as inputs for structural analyses with respect to three alternate types of 3DP cob wall patterns to evaluate their load-carrying capacity based on a limit-state design framework. Results from the analyses were implemented in modelling an idealised low-rise cob building covering a range of floor spans and wall heights. The analytical study found that 3D-printed walls have the potential to sustain gravity loads typical of residential construction. Further, since the 3DP material was shown to have similar mechanical performance to conventional (non-3DP) cob on the material scale, the 3D-printing process provides the opportunity to produce wall sections that are structurally more efficient than the solid section used in conventional cob construction. This results in lower material consumption, making 3DP cob attractive from the point of view of resource efficiency. An important outcome of the study is the demonstration of a model design technique for low-rise 3DP cob buildings that could be implemented as part of a broader optimisation procedure to satisfy structural and architectural design objectives

Unreinforced masonry walls subjected to out-of-plane seismic actions.

During a seismic event, the walls within an unreinforced masonry (URM) building must possess sufficient capacity to withstand out-of-plane collapse. Traditionally, design against this type of failure has been performed using a force-based (FB) approach, in which the engineer must ensure that the force capacity of the wall is not exceeded during a design earthquake. In recent years, however, seismic design philosophy for ductile systems has experienced a move away from FB methods and toward displacement-based (DB) methods, where the aim is to ensure that structural deformations are kept within acceptable displacement limits. URM walls subjected to out-of-plane actions make a prime candidate for the development of such methodology. This is particularly true for two-way spanning walls, which have significant displacement capacity as well as good energy dissipation capability during cyclic response—both highly favourable characteristics with respect to seismic performance. This thesis documents research undertaken at the University of Adelaide into the seismic response of two-way URM walls subjected to out-of-plane actions. The aims of this work were to facilitate improvements to the presently-used FB design methods and to provide a basis for the development of a reliable DB design approach. The following outcomes have been achieved: • Characterisation of the load-displacement behaviour of two-way walls through quasistatic cyclic testing using airbags; • Verification of this behaviour under true seismic loading conditions by means of dynamic shaketable tests; • Improvements to the current state-of-the-art design approach for predicting the ultimate load capacity of walls possessing tensile bond strength; • A probabilistic approach to deal with the different modes of possible failure in horizontal bending; • Development of analytical methodology for predicting the load capacity of walls using the assumption of zero tensile bond strength; • A proposed model for representing the nonlinear inelastic load-displacement behaviour of two-way walls; and finally, • Implementation of the load-displacement model into a simple DB seismic assessment procedure. It is anticipated that this research will eventually culminate in a multi-tiered seismic design procedure incorporating both the FB and DB components, with applicability toward the design of new buildings and assessment of existing buildings alike.Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 201

Out-of-Plane Shaketable Testing of Unreinforced Masonry Walls in Two-Way Bending: Supplementary Material

This data set contains supplementary material for Vaculik and Griffith (2017) [full reference below].<br><br>Included are:<br>- Supplementary Material pdf document (120 pages)<br>- zip file containing time-domain data, both processed and unprocessed<br><br>Vaculik, J., and Griffith, M. C. (2017), Out-of-plane shaketable testing of unreinforced masonry walls in two-way bending, Bulletin of Earthquake Engineering, doi: 10.1007/s10518-017-0282-8<br

Recent developments in the seismic assessment of masonry buildings

Significant research has been conducted to establish the seismic capacity of unreinforced clay brick masonry buildings in Australia. In this paper, we consider modern and older existing construction typical of Australia. The paper presents results of laboratory tests on large scale walls, in-situ tests of walls in houses, and analytical predictions to estimate the level of damage that could be expected in a range of earthquake scenarios in Australia to support our conclusion that even a modest M6.0 earthquake within 10km of any capital city in Australia poses a significant life safety hazard to the public and a financial exposure to the nation in the order of $10 Billion

Recent developments in the seismic assessment of masonry buildings

Significant research has been conducted to establish the seismic capacity of unreinforced clay brick masonry buildings in Australia. In this paper, we consider modern and older existing construction typical of Australia. The paper presents results of laboratory tests on large scale walls, in-situ tests of walls in houses, and analytical predictions to estimate the level of damage that could be expected in a range of earthquake scenarios in Australia to support our conclusion that even a modest M6.0 earthquake within 10km of any capital city in Australia poses a significant life safety hazard to the public and a financial exposure to the nation in the order of $10 Billion

Seismic performance expectations for Australian unreinforced masonry buildings

Professor Griffith will give an overview of recent and ongoing research into the seismic behaviour of unreinforced masonry (URM) construction in Australia. His talk will focus primarily on: - the seismic vulnerability of URM walls to out-of-plane bending and the associated local failure mechanisms; - the influence of flexible floor and roof diaphragms on the seismic response of URM buildings up the height and the impact on non-structural components; and - a progress report on work studying the seismic resistance of Heritage URM (stone and brick) construction

High-speed pullout behavior of deep-mounted cfrp strips bonded with a flexible adhesive to clay brick masonry

An experimental campaign was initiated to determine the high-speed pullout behavior of deep-mounted carbon fibre-reinforced polymer (CFRP) strips bonded with a flexible, visco-elasto-plastic adhesive to clay brick masonry. A total of 14 direct pull-tests were conducted. Strong correlations were found between both the pull-out strength/bonded length relation and the pull-out strength/loading rate relation. The governing failure mechanism was either cohesive failure combined with brick splitting, or CFRP rupture without significant damage to the masonry prism. From the strain gauge readings, multiple bond-slip correlations were constructed and eventually generalized and simplified to a global, multi-linear bond-slip relation. Using the global bond-slip law as part of a partial-interaction analysis resulted in a good fit with the experimental results. Finally, the results of this study were compared to previous direct pull-tests found in literature, showing that the application of a flexible adhesive results in higher interfacial fracture energy and higher debonding slip