College of Engineering
http://hdl.handle.net/10092/1
2016-07-29T13:58:46ZSeismic performance of pre 1970s non-ductile reinforced concrete waffle slab frame structures constructed with plain round reinforcing steel.
http://hdl.handle.net/10092/12535
Seismic performance of pre 1970s non-ductile reinforced concrete waffle slab frame structures constructed with plain round reinforcing steel.
Saunders, Dean Bruce
This thesis investigates the seismic performance of components of a typical pre 1970's
New Zealand non-ductile reinforced concrete waffle slab frame structure constructed
with plain round reinforcing steel. The experimental program tests the top and bottom
sections of a typical concrete column, and a two-bay waffle floor slab sub-assemblage.
The specimen of the scaled bottom section of the typical column is an octagonal section
with a circular reinforcing steel arrangement on a pitch circle diameter of 41 Omm. The
reinforcing steel is lapped at the base with a lap length of 45db. The analysis and results
indicate a lap-splice failure mechanism with pinching of the hysteresis loops after the
nominal flexural capacity of the specimen is reached. The section has an effective
moment of inertia of O. l 6Ig and a yield drift, 8y of 0.62%. It is possible from the new
theory developed to predict whether a lap-splice failure mechanism will form and at
what stage strength degradation begins. Hysteretic · modelling of the experimental
results is possible with the proposed hysteresis rule.
The specimen of the scaled top section of the typical column is an octagonal section
with a 215mm high column capital. The reinforcing steel arrangement is circular on a
pitch circle diameter of 41 Omm with additional reinforcement at 45 degrees in the
column capital. The analysis and results indicate a flexural failure mechanism with
pinching of the hysteresis loops due to slip of the reinforcement. The section has an
effective moment of inertia of 0.19Ig and a yield drift, 8y of 0.65%. Hysteretic
modelling of the experimental results is possible with currently available hysteresis
rules.
The scaled two-bay waffle floor slab sub-assemblage supported by three central
columns is tested to determine the critical failure mechanism. Scaling symmetry and
elongation allowances are incorporated into the design of the testing setup. The results
match the structural assessment predictions of a unidirectional flexural yield line failure
mechanism. The effective moment of inertia of the floor slab is 0.43Ig and the full
flexural strength is reached at an interstorey drift of 1.0%. The bay elongation characteristics of the specimen are matched by the theory for elongation of
unidirectional hinges.
Elements of an assessment methodology for reinforced concrete structures are discussed
and the outcomes of such an assessment related to damage state indices for both pre and
post earthquake assessments. Specific examples from the experimental program are
used to illustrate the damage state outcomes of this testing.
2004-01-01T00:00:00ZOn approximation of optimizing phylogenetic diversity for cluster systems
http://hdl.handle.net/10092/12533
On approximation of optimizing phylogenetic diversity for cluster systems
Faller, Beáta; Semple, Charles; Steel, M. A.
A basic question in conservation biology is how to maximize future
biodiversity as species face extinction. One way to approach this question
is by measuring the diversity of a set of species in terms of the evolutionary
history that those species span in a phylogenetic tree. Maximizing the resulting
'phylogenetic diversity' (PD) is one prominent selection criteria for deciding
which species to conserve. The basic PD optimization problem aims to find a
k-element subset of a given species set that has maximum PD among all such
subsets. In this paper, we consider a generalization of this problem, which
arises in situations where we do not know the true tree, or where evolution is
not tree-like. We show that a greedy algorithm gives a (1-e⁻¹)-approximation
to the general PD optimization problem, and that there is no polynomial-time
algorithm that achieves a better approximation ratio unless P=NP.
2009-01-01T00:00:00ZPhylogenetic diversity and the greedy algorithm
http://hdl.handle.net/10092/12532
Phylogenetic diversity and the greedy algorithm
Steel, M. A.
Given a phylogenetic tree with leaves labelled by a collection of
species, and with weighted edges, the 'phylogenetic diversity' of any subset of
the species is the sum of the edge weights of the minimal subtree connecting
the species. This measure is relevant in biodiversity conservation where one
may wish to compare different subsets of species according to how much evolutionary
variation they encompass. In this note we show that phylogenetic
diversity has an attractive mathematical property that ensures that we can
solve the following problem easily by the greedy algorithm: find a subset of
the species of any given size k of maximal phylogenetic diversity. We also
describe an extension of this result that also allows weights to be assigned to
species.
2004-01-01T00:00:00ZA cluster reduction for computing the subtree distance between phylogenies
http://hdl.handle.net/10092/12531
A cluster reduction for computing the subtree distance between phylogenies
Linz, Simone; Semple, Charles
Calculating the rooted subtree prune and regraft (rSPR) distance
between two rooted binary phylogenetic trees is a frequently applied process in
various areas of molecular evolution. However, computing this distance is an
NP-hard problem and practical algorithms for computing it exactly are rare.
In this paper, a divide-and-conquer approach to calculating the rSPR distance
is established. This approach breaks the problem instance into a number of
smaller and more tractable subproblems. Two reduction rules which were
previously used to show that computing the rSPR distance is fixed-parameter
tractable can easily be used to complement this new theoretical result, and so
a significant positive impact on the running time of calculating this distance
in practice is likely.
2008-01-01T00:00:00Z