- Title
- Spatial variability and stochastic strength prediction of unreinforced masonry walls subjected to out-of-plane bending
- Creator
- Li, Jie
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2016
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Past research has produced extensive information on the material properties of brickwork, and found that random variations of the material and mechanical properties of brickwork could have a significant effect on the wall performance and capacity when the wall is required to resist lateral out-of-plane loads due to the actions of wind or earthquake. Few scholars state that the consideration of the unit to unit spatial variability of the brickwork material can improve the modelling of wall failure progression, strength prediction and structural reliability. Very few studies have considered the computational methods for calculating the structural reliability of masonry structures. Previous investigations have identified that there is a need for developing theoretical and computational models to enable the accurate and efficient calculation of reliability for new and existing masonry structures. Although extensive work has been directed at developing predictive strength models for masonry, very little effort has so far been directed towards the issues of model error (degree of accuracy of the predictive strength models); material behaviour (unit strength) uncertainty and variability; unit-to-unit spatial strength variability; and their effect on wall strength and reliability. A reliability analysis requires probabilistic information for all of these variables. A stochastic computational model is established in this research project which combines the Finite Element Method and Monte Carlo simulation to study how the spatial variability of material properties affects the non-load bearing wall failure progression, wall strength and the reliability index. The work described in this thesis takes the unit to unit spatial variability of the material properties of brickwork into account, and conducts a comparison of the results with those obtained when the wall is a uniform material. The first stage of the thesis involves a comparison of the failure progression and wall strength of the full-sized wall using two methods, with and without the spatial variability of the material properties when the wall is subject to one way vertical bending. The probabilistic information of the material properties is obtained from a literature review. It is found that the failure mode without a consideration of spatial variability is symmetrical, while the failure processes are random and asymmetrical for the wall when there is a consideration of the spatial variability of the brickwork, which is considered as the more realistic failure mode. Furthermore, it is found that an analysis which excludes spatial variability will over estimate the probability of wall failure compared to an analysis which includes spatial variability. The second stage of the thesis involves developing a stochastic FEA model which reproduces the horizontal bending of a four course beam studied in the experimental work, comparing the numerical results with experimental results in terms of the failure mode and peak load. This numerical simulation work is concluded using the two methods previously mentioned. The comparison can illustrate which method is more realistic based on how closely the numerical results match the experimental results. The results in this section show that the analysis which considers the spatial variability of the brickwork can give a more reasonable agreement, in terms of the peak load prediction and the failure location observed in the experimental work compared to the analysis without a consideration of spatial variability. The third stage of the thesis involves conducting the numerical work of simulating the full sized wall when it is subject to two way bending in the experimental work using the same two methods mentioned above. The numerical results are compared to the experimental results, in terms of the wall failure progression and wall capacity. It is shown that the model which considers the spatial variability of the brickwork can capture the failure pattern and predict the cracking load and ultimate load quite well for walls with two way bending. The final stage of the thesis involves calculating the probability of failure and the reliability index of the full sized wall subject to one way vertical and two way bending, analysing how the wall strength distributions and spatial variability of the material properties affects the probability of failure and reliability index. The reliability analysis shows that, in achieving the target reliability index for the wall subject to one-way vertical bending and two way bending, the capacity reduction factor is heavily affected by the model error statistics. Different model error statistics may lead to other trends being observed about the conservatism or not of AS3700. The results need to be further studied with more experimental data collection to determine an accurate model error, but the present study still can show how the FEA model error affects the code calibration.
- Subject
- masonry wall; spatial variability; reliability; one way vertical bending; horizontal bending; two way bending
- Identifier
- http://hdl.handle.net/1959.13/1312792
- Identifier
- uon:22462
- Rights
- Copyright 2016 Jie Li
- Language
- eng
- Full Text
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| View Details Download | ATTACHMENT02 | Thesis | 3 MB | Adobe Acrobat PDF | View Details Download |