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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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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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

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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.