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e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 1 of 12
Optimization of Caisson with ChromX Steel
Example Used in
Bon Air Road Bridge
Replacement Project
Larkspur, CA
PROPOSED BY: E.CONSTRUCT
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 2 of 12
TABLE OF CONTENTS
INTRODUCTION ............................................................................................................................................... 3 DESIGN COMPARISON ................................................................................................................................... 3
ABUTMENT PILE ASSESMENT ................................................................................................................. 3 PIER PILE ASSESMENT ............................................................................................................................... 8
SUMMARY ........................................................................................................................................................ 12
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 3 of 12
INTRODUCTION The purpose of this report is to investigate the possibility of replacing the currently used Grade 60 steel with high-strength
reinforcement, ChromX Grade 100 steel, in caissons. The benefits include substantial savings in reinforcing steel weight,
reduction in reinforcing steel fabrication, and an improved reinforcement layout. The following section of this report
provides a detailed example of the current design vs. the proposed design for both a Cast-in-Drilled-Hole (CIDH) Pile for
bridge abutments and a concrete column at bridge piers.
DESIGN COMPARISON
ABUTMENT PILE ASSESMENT The current design for an abutment pile can be seen in Figure 1.
Figure 1. Existing CIDH Pile Elevation and Section
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 4 of 12
Figure 2 shows the proposed section for a CIDH pile using ChromX. The total number of bars are reduced when utilizing
high-strength steel reinforcement (Grade 100).
The following spreadsheet was used to analyze the performance of a CIDH pile by using both Grade 60 and ChromX Grade
100 steel. The pile interaction diagrams were then plotted to better represent this comparison. A reduction of 0.5 in. of
cover was used in accordance with AASHTO LRFD 8th Edition, Chapter 5 provisions.
Figure 2. Proposed Section for a CIDH Pile
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 5 of 12
The pure flexural strength for the column based on the current design, with 12#10 Gr. 60 reinforcement, is ɸMn = 609
kip-ft/ft.
Figure 3. Pure Flexural Capacity Summary for Current Section (Grade 60)
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 6 of 12
Figure 4. Pure Flexural Capacity Summary of Proposed Section (Grade 100)
The pure flexural strength of the proposed column design using 8#10 Gr. 100 reinforcement is ɸMn = 656 kip-ft/ft.
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 7 of 12
Below, Figures 5 & 6 show the interaction diagrams, P-M, for both the current and the proposed column sections.
Figure 5. P-M Interaction Diagram for the Current Column Design (Grade 60)
Figure 6. P-M Interaction Diagram for the Proposed Column Design (Grade 100)
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 8 of 12
A reinforcement reduction of 33% can be achieved by using ChromX rebar while maintaining the same flexural strength.
PIER COLUMN ASSESMENT The current design for a concrete column can be seen in Figure 7:
Figure 7. Current Section for a Concrete Column
The proposed section for a concrete column is shown in Figure 8. A reduction of 0.5 in. of cover was used in accordance
with AASHTO LRFD 8th Edition, Chapter 5 provisions.
Figure 8. Proposed Section for a Concrete Column
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 9 of 12
Figure 9. Pure Flexural Capacity Summary for Current Section (Grade 60)
The pure flexural strength for the column based on the current design with 40#14 grade 60 is ɸMn = 9541 kip-ft/ft.
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 10 of 12
Figure 10. Pure Flexural Capacity Summary for Proposed Section (Grade 100)
The pure flexural strength for the column proposed, designed with 36#11 Gr. 60 reinforcement, is ɸMn = 9783 kip-ft/ft.
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 11 of 12
Figures 11 & 12 show the interaction diagrams P-M for both the current and the proposed column sections.
Figure 11. P-M Interaction Diagram For the Current Column Section (Grade 60)
Figure 12. P-M Interaction Diagram for the Proposed Column Section (Grade 100)
e.CONSTRUCT USA LLC
11823 Arbor Street, Omaha NE 68144
(402) 884-9998
Project: Optimization of Caisson with ChromX Steel Designed By: DK Date: 8/27/2019
Subject: Example used in Bon Air Road Bridge
Project Checked By: AG Sheet 12 of 12
A reinforcement reduction of 38% can be achieved by using ChromX rebar while maintaining the same flexural strength.
SUMMARY
The results of this investigation demonstrate that ChromX Grade 100 Steel can be effectively implemented in this
project. The benefits include substantial savings in reinforcing steel weight, reduction in reinforcing steel fabrication and
an improved reinforcement layout. Table 1 and Figure 13 summarize the achieved weight reduction.
Table 1. Weight Comparison Between Current and Proposed Column Sections
Element Current Area of
Longitudinal Steel (in2) Grade 60
Proposed Area of Longitudinal Steel (in2)
Grade 100
CIDH Pile 15.24 10.16
Concrete Column (6') 90.0 56.16
A reduction in the total amount of reinforcement and weight per element will simplify the column construction and could
lead to reduced labor and an improved quality of the structural element.
Figure 13. Weight comparison between current and proposed column sections.