ABSTRACT
This study focused on the
behavior of bamboo reinforced self-compacting concrete (BRSCC) beams and slabs
under monotonic loading. Both BRSCC and Bamboo Reinforced Natural Concrete
(BRNC) samples with varying percentages of bamboo (1.5 and 3% for beams and 1%,
2% and 3% for slabs) as longitudinal reinforcement were cast and tested to
study shear and flexure failure mechanisms and the contribution of concrete and
bamboo to their resistance. The beams were 100 mm wide and had different depths
of 150 mm, 250 mm and 275 mm with lengths of 1050 mm, 1200 mm and 2000mm
respectively and a span to depth ratio of 1.8. The slabs on the other hand had
dimensions of 1000 x 300 x 80 mm and a shear span- to - depth ratio of 2.5. All
the samples were simply supported and subjected to a four-point monotonic
loading. During testing, the characteristics of the samples under loading such
as deflection, cracking and failure were observed and recorded.
The study established that for
the same percentage longitudinal reinforcement and sectional properties, energy
dissipation capacity of the structural components (beams and slabs) of BRSCC
was higher than their BRNC counterparts. The average increase in the energy
dissipation was 17% and 15% for slabs and beams respectively. In addition, the
longitudinal reinforcement ratios greatly impacted the shear capacities and
degree of ductility of the structural components.
Though bamboo as a longitudinal
reinforcement contributes to shear resistance, it is recommended that a code
predictive equation that does not explicitly account for longitudinal shear
resistance e.g. CSA be utilized when designing BRSCC structural components.
BS, ACI, EC 2 and CSA
overestimated the prediction of the flexural capacities of the slabs when a
material factor of safety of 3 was used for the bamboo. Hence a reduction
factor of 0.5 must be applied to code prediction when designing BRSCC slabs to
ensure a high enough safety factor on ultimate strength.
CHAPTER 1: INTRODUCTION
1.1 Background of study
The United Nations (UN) initiative
of transforming the world by setting up targets for sustainable development has
identified the need to make cities and human settlement safe, resilient and
sustainable as much as possible (UNDP, 2015). Currently, shortage of adequate
housing and declining infrastructure are among the major challenges that have
to be addressed. For instance, in Ghana, the annual deficit in the building
industry is about 200,000 housing units (Adom-Asamoah and Afrifa, 2011). Beside
the shortfalls, most formal housing units are beyond the affordability level of
majority of the population. Extensive research efforts aimed at improving
housing affordability have emphasized the need for construction materials and
methods which will reduce total cost of structures as well as maintain a
sustainable construction industry.
In the construction industry,
concrete has been the most widely used material because of its versatility and
relative economy in meeting a wide range of needs. Nonetheless, a variety of
concrete types have been developed to address strength, durability and
constraints that can be met at construction sites. A typical example is the
introduction of Self-compacting Concrete (SCC) in Japan when the availability
of skilled labourers became a problem in the 1980s. An added advantage to the
use of SCC is its ability to help reduce time and cost of construction since
there is no need for mechanical vibration of the in-place concrete. For
instance, construction of the anchorages of the Akashi Kaikyo suspension bridge
took 2 years to complete when SCC was used. This would have taken 2.5 years for
completion with the use of Normal Concrete (NC). In another case when SCC was
used in the construction of a large liquefied natural gas (LNG)
tank belonging to Osaka Gas Company, it led to a reduction in the number of
workmen from 150 to 50 (Ouchi and Hibino, 2000). These benefits of using SCC in
the construction industry have proven how it can help maintain sustainable
development, particularly in rural and peri-urban areas worldwide.
An integral part of providing safe
and resilient structures for human settlement is the selection of construction
materials that give a great deal of reliability in terms of structural
performance and durability under all forms of external loads. Basically,
concrete has low tensile strength and as such, reinforcement (conventionally
steel) is used to supplement region of structural components (beams, columns
and slabs) that are subjected to high tensile stresses. Apart from steel, other
synthetic and natural materials such as fiber glass and cane have been found to
be good for resisting tensile stresses. One other natural material which is
readily available and easy to use in rural and farming communities is bamboo.
Unlike steel production which releases a lot of CO2; a major contributor to
global warming, bamboo, which is naturally occurring, tends to reduce the
amount of CO2 in the environment. Therefore, the extent of pollution will be
drastically reduced when bamboo is used as a reinforcing material, and long
term climatic goals of reducing carbon intensity by the UN can be effectively
addressed. Moreover, the cost of steel is comparatively higher than bamboo;
hence developing countries may opt for its usage to maintain an affordable and
sustainable infrastructural development especially in areas where it is in
abundance.
1.2 Problem Definition
The high demand for housing
facilities and the ever increasing cost of construction materials make building expensive.
There is, therefore, the need to explore suitable materials that have the potential
to maintain adequate structural performance and at the same time reduce the
cost of construction. The use of Bamboo Reinforced Self Compacting Concrete
(BRSCC) has the potential of providing affordable housing facilities at a
faster rate. However, concern about performance of bamboo for reinforcement
still remains an issue under study. This stems from the fact that, bamboo
possesses a very wide range of variability in mechanical properties,
particularly tensile and bond strength that are imperative for structural
integrity. Also, bamboo is vulnerable to insect attack and water absorption
which may have an adverse impact on its durability. On the other hand,
experimental test of structural components using SCC has shown a low resistance
to shear stresses as compared to NC (Lachemi et al., 2005). This is because of
the relatively low coarse aggregate content needed to achieve a flowable mix.
Consequently, aggregate interlock which is a major contributor to shear
resistance, accounting for about 35-50%, is greatly reduced. Since much
research work has not been done on the performance of BRSCC beams and slabs,
this dissertation seeks to set out the tone and advance knowledge in the
evaluation of their shear and flexural capacities.
1.3 Objectives
The objectives of the study were to
assess the variations in the strength characteristics of short span structural
components that use BRSCC and BRNC as structural materials and to provide
reliable estimates of the flexural contribution from bamboo.
The specific objectives were;
* To evaluate the shear capacities of
NC and SCC short span beams when bamboo is used as the longitudinal reinforcing
material.
* To evaluate the flexural strength
of NC and SCC short span one-way slabs when bamboo is used as reinforcement.
* To assess the impact of increasing
longitudinal reinforcement of bamboo on flexural and shear capacities.
* To evaluate the adequacy and
application of current code predictive equations to BRSCC specimens.
1.4 Organization of Thesis
This thesis is in five chapters.
Chapter 1 introduces SCC as another form of concrete technology and bamboo as a
viable replacement of steel in structural concrete production. It also presents
the objectives of the study. Chapter 2 presents a review of the related
literature on SCC and bamboo in NC and rationalizes the relevance of using SCC
and bamboo in structural concrete production. Chapter 3 gives an overview of
the research programme and procedures for experimental investigation and
highlights on concrete mix design as per different constituent materials
applied in the study. Chapter 4 presents results and discussions of the BRSCC
and BRNC specimens produced in the study and examines the suitability of the existing
code provisions for the design of BRSCC. Finally, Chapter 5 presents the
summary of findings and conclusions for the study and proffers recommendations
for future studies in the content area.
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