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ELIMINATING COLUMN FORMWORK USING PREFABRICATED
UHPC SHELLS
Quarterly Progress Report
For the period ending August 31, 2019
Submitted by: Nerma Caluk, Research Assistant
Islam Mantawy, Ph.D., Research Assistant Professor
Atorod Azizinamini, Ph.D., PE., Director of ABC-UTC
Graduate Student: Nerma Caluk
Affiliation: Department of Civil and Environmental Engineering
Florida International University
Miami, FL
Submitted to:
ABC-UTC
Florida International University
Miami, FL
1. Background and Introduction
Traditional formwork acts as molds for wet concrete and supports concrete wet weight and live
load of equipment and workers temporarily. Scaffolding acts as a supporting platform and provides
temporary access to structures under construction. Erecting components of formworks and
scaffolding together takes time, can cause traffic congestion, and increase the construction cost. It
is also possible that the design cannot be incorporated due to unexpected site conditions, and
formwork failures can occur because of deviations from the original design. Formwork failures
can also occur due to possible human errors or crushing of wooden surface where the heavy loads
are placed if the bearing surface of joins is not appropriately designed. Based on “Use and Re-use
of Formwork: Safety Risks and Reliability Assessment” report, the re-used formwork is not
factored into its design, and since it is subjected to wide range of loads and exposures, it can
experience possible degradation in its structural capacity. Furthermore, failure of formwork can
also occur during concrete pours and can cause concrete leaking, failure of formwork components,
complete structural collapse, and serious injuries or deaths. Possible failures of formwork can be
caused by mistake during erection, wrong calculations of weight acting on formwork, extra loads
or due to natural disasters.
2. Problem Statement
In order to prevent possible hazards of formwork and scaffolding failure, a new concept is
being developed using ultra-high performance concrete (UHPC) to prefabricate a shell which acts
as permanently stay-in-place form for bridge elements. The prefabricated shell is intended to
eliminate the conventional formwork and scaffolding, reducing the on-site construction time and
acting as a durable protective layer for the normal strength concrete inside it.
3. Objectives and Research Approach
The main objectives of this project are:
a) The development of prefabricated UHPC shell for bridge column
b) The development of column-to-cap beam and column-to-footing connections for the
proposed precast UHPC shell column
c) Performing analysis on the collected data from the experimental study done on the 1st
bridge column utilizing UHPC shell under constant axial and lateral cycle loads
d) The development of 2nd specimen based on the numerical analysis of the 1st specimen
e) Conducting numerical modeling using finite element models on the tested specimen
4. Description of Research Project Tasks
The following is a description of tasks carried out to date.
Task 1 – Design and analysis of the column specimens
In this task, the first and second column were designed and analyzed, using smooth surface
between the UHPC shell and normal concrete inside for the first specimen and shared longitudinal
reinforcement between UHPC shell and normal concrete for the second specimen. Furthermore,
the connection between the column and footing was studied using UHPC to reduce lap splice
length between column longitudinal reinforcement and footing dowels. Moment curvature analysis
was performed on both specimens prior to construction of the first specimen in order to compare
different sections and predict where the failure will be localized.
Progress: This task is completed and the two specimen are designed and analyzed
Task 2 – Construction of the first Specimen
In this task, the construction of the first specimen will be conducted. A construction procedure
will be proposed for field implementation.
Progress: This task is completed. The first step of construction was fabricating the footing and its
reinforcement using conventional methods. The precast shell for the first specimen was shaped
using a sonotube as the outside layer, and Styrofoam as the inside layer in order to shape the one-
inch shell thickness. No reinforcement was embedded for this specimen; instead, the steel cage
was placed later inside the shell as the reinforcement of the conventional concrete core. For the
lab construction environment, the steel cage had to be placed in the shell prior to its placement on
the footing. Thus, both elements were lifted together and placed on the footing, where the steel
cage was spliced with the dowels in the footing. Once the splicing was completed, the shell was
released to sit over the footing and the UHPC step was cast inside a 406.4-mm diameter sonotube
with a height of 177.8 mm. The concrete for the column core and cap beam was poured after the
UHPC in the step had hardened; then, the shell and steel reinforcement were stable, as shown in
Figure 1. Construction steps for the first specimen. More information about the construction, test
setup, instrumentation, are presented in (Caluk et al. 2019).
Task 3 – Experimental work on the first Specimen
In this task, experimental work will be conducted on the first specimen. The column will be
tested under constant axial and lateral cyclic loads.
Progress: This task is completed. Based on the collected data, experimental result analysis was
conducted on the first specimen, tested under constant axial and lateral cyclic loads. Figure 2
shows the test setup. Figure 3 shows the failure of the first specimen after the completion of the
test. Figure 4 shows force vs displacement graph of the first specimen. The specimen failed at 7.5%
drift ratio after the first bar fractured.
Figure 1. Construction sequence of the first specimen (Caluk et al. 2019).
Figure 2. Test setup for the first column specimen (Caluk et al. 2019).
Figure 3. Localized damage at UHPC step for the first specimen.
Figure 4. Force vs Displacement response of the first specimen.
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Forc
e (
kN
)
Displacement (mm)
Envelope
Hysteresis
Task 4 – Construction of the second specimen
Based on the numerical analysis of the first specimen, the design and analysis of the second column
was refined and construction was proceeded.
Progress: The construction of the footing of the second specimen was completed (Figure 5), after
which the shell was constructed using, comprising of Ultra High-Performance Concrete and #6
longitudinal reinforcement partially embedded in the shell (Figure 6). The shell component was
then placed onto the footing and spliced with the dowel bars coming out of the footing. A 7.5-inch
UHPC step was cast around the footing-shell interface. Once the UHPC step has cured, the
scaffolding has been placed (Figure 7) for the final casting of normal concrete in the inner core
and cap, which will be done beginning of 2020.
Figure 5. Completed footing of the second specimen
Figure 6. The formwork used for embedment of the longitudinal reinforcement (left); the
completed UHPC shell with the partially embedded longitudinal reinforcement (right)]
Figure 7. The completed scaffolding for the final cast of conventional concrete in the core
and cap beam (left) and the complete test set up of the second specimen (right)
Task 5 – Experimental work on the second specimen
In this task, experimental work will be conducted on the second specimen. The column will be
tested under constant axial and lateral cyclic loads.
Progress: This task is completed. Based on the collected data, experimental result analysis
was conducted on the second specimen, tested under constant axial and lateral cyclic loads. Figure
8 shows the behavior of the second specimen after testing, which is compared with the behavior of
the first specimen. The results indicate that the first specimen performed better than the second
specimen. Figure 9 shows the final damage of the second specimen after the completion of the test.
This specimen did not have any bar ruptures up to 6% drift ratio, however, the test was terminated
due to the loss in the lateral capacity (50% loss), as shown in Figure 8, indicating the failure of
the specimen. The energy dissipation for the second specimen matches the energy dissipation of
the first specimen up to 2% drift ratio, however, after 2% drift ratio the energy dissipation was
much less if compared to the first specimen, as shown in Figure 10.
Figure 8. Comparison of the results for the first and second specimen
Figure 9. The final damage of the second specimen after the test
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Mom
ent
(kip
-in)
Displacement (in)
2nd Specimen
1st Specimen
Figure 10. Energy dissipation comparison between the first and second specimen
Task 6 – Final Report
In this task, the full assessment of the findings for both 1st and 2nd specimen will be conducted,
and full report will be published containing the design recommendations for the prefabricated
UHPC shells.
Progress: Researchers have published a journal article (Caluk et al. 2019) on this concept and
the development of this research topic in addition. Another paper has been published by the
Transportation Research Record on the development of this concept, while also contained the
results and behavior of the first specimen after the testing and data analysis. (Caluk et al. 2020).
5. Expected Deliverables
Final report, journal articles, design guidelines, and five-minute video presentation will be the
expected deliverables
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0.50% 1% 1.50% 2% 3% 4% 5% 6.00%
Ene
rgy
Dis
sip
atio
n (
kip
-in
)
Drift Ratio (%)
ENERGY DISSIPATION FOR EACH DRIFT RATIO
1st Specimen Behaviour
2nd Specimen Behaviour
Linear (2nd Specimen Behaviour)
6. Schedule
Item % Completed
Percentage of Completion of this project to Date 90%
7. Reference
Caluk, N., Mantawy, I., & Azizinamini, A. (2019). Durable Bridge Columns using Stay-In-Place
UHPC Shells for Accelerated Bridge Construction. Infrastructures, 4(2), 25.
Caluk, Nerma, et al. “Cyclic Test of Concrete Bridge Column Utilizing Ultra-High Performance
Concrete Shell.” Transportation Research Record, Feb. 2020, doi:10.1177/0361198120906088.