Copyright © 2009 by Dr. Thomas W. Rioux
Students taking this course may print one copy of this document for their personal class use.

Objectives:   Use the features of MicroStation, GEOPAK, and engineering judgment to design one side of a grade-separated, Two-Quadrant, Partial Cloverleaf A Interchange as depicted in AASHTO 2004 on page 791.   Learn to work on a team and make effective project presentations.   Recognize the value of  interactions with other professional disciplines.

Activity:   The Design Project will be performed by teams of 2 students with no more than 1 graduate student per team. Design Project Part 1 will be to Define the Vertical Alignment for Road 2000 over the Freeway using GEOPAK.   Design Project Part 2 will be to Design the Intersection Channelization of the Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange using MicroStation.   Design Project Part 3 will be to Design the Freeway Entrance Ramp of the Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange using GEOPAK.   Design Project Part 4 will be to Design the Freeway Exit Ramp of the Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange using GEOPAK.   Design Project Part 5 will be to Define the Superelevation and Complete the Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange using GEOPAK. 

Design Project Considerations:   Although the Design Project is primarily focused on the geometric roadway design, each team should consider the complete life cycle of the project including planning, design, construction, and maintenance.   In addition, other items such as cost, right-of-way acquisition, signalization, lighting, landscaping, signing, pavement markings, drainage, pavement design, and constructability should be addressed.   Each team will be required to define the data that they should provide to other professionals in Civil Engineering and other disciplines and define the data that they should receive from other professionals in Civil Engineering and other disciplines.   Each team should consider the associated safety, aesthetics, schedule, and social and environmental issues.   Each team should develop a plan for public input into the design process.   The report should contain a discussion of all design project considerations.

Background:   There is an existing Freeway which runs due East and West.   The objective is to design Road 2000 which runs due North and South to cross over the Freeway.   There is a large building in the southeast quadrant prohibiting the use of that quadrant.   Using a Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange, you will design the exit ramp from the Freeway to Road 2000, the entrance ramp from Road 2000 to the Freeway, and the intersection of the ramps and Road 2000 in the southwest quadrant.   The Freeway and Road 2000 intersect at Freeway Station 80+00.00 and Road 2000 Station 20+00.00.   The intersection of the Freeway and Road 2000 is at coordinate (5000,5000).   The portion of the Freeway for this project is 4500 feet long, 3000 feet to the west of the centerline for Road 2000, 1500 feet to the east of the centerline for Road 2000, and the centerline elevation is at elevation 200.00.   The portion of Road 2000 for this project is 3650 feet long, 1400 feet to the north of the centerline of the Freeway, 2250 feet to the south of the centerline of the Freeway, and the centerline elevation is at elevation 200.0 at each end. Stationing increases from west to east on the Freeway and from north to south on Road 2000.   There are 12 columns with 1.5 foot radius for the overpass bridge represented in the reference file in blue and the bridge should accommodate a WB-50 design vehicle.   The Freeway is a 4-lane, divided highway with a median, does not have frontage roads, accommodates a design speed of 70 miles/hr, has a normal 2% crown, and stationing increases from West to East.   Road 2000 is a 4-lane, undivided highway (without a median), accommodates a design speed of 50 miles/hr with a maximum grade of 6 percent, has a normal crown of 2%, stationing increases from North to South.   To provide adequate lateral and vertical clearance over the Freeway, the centerline profile of the finished grade (the bridge deck) on Road 2000 should pass through a point located 85 feet laterally from the centerline of the Freeway and 22.5 feet above the centerline elevation of the Freeway.   The entrance ramp and the exit ramp accommodate a design speed of 50 miles/hr, will have a 4 foot median at their closest points (edge of shoulder to edge of shoulder), and will have a normal 2% crown on tangent sections.   Each ramp will be 14 feet wide with a 8 foot right-hand shoulder and a 2 foot left-hand shoulder in the direction of travel (24 feet total width).   There should be a minimum of 0 feet and a maximum of 100 feet of tangent section between adjacent spirals.   The right turn from Road 2000 southbound to the Entrance Ramp westbound should accommodate a design speed of 15 miles/hr.   The right turn from the Exit Ramp eastbound to Road 2000 southbound should accommodate a design speed of 25 miles/hr.   Superelevation and spirals will be used with all horizontal curves designed using GEOPAK.   The maximum superelevation rate should be 8%.   The intersection of the Entrance/Exit Ramps and Road 2000 occurs at an 85 degree angle and should accommodate a WB-50 design vehicle.   Use the Texas Department of Transportation entrance and exit ramp terminal designs for connections with the Freeway.   Use the tables and charts in the 2004 AASHTO Green Book for all other design values.

Design Questions:   In addition to the final plot of your design, you should list and answer the design questions in your report and turn your report in with your final plot.   The names of the team members should be prominently printed on the cover of your report.   The file "Design Project Overview.doc" may be downloaded from \\disk.austin.utexas.edu\root\engrstu\class\caee\ce367.   Adequate information should be provided in your answers to the design questions to properly support the design decisions that you made as if your were defending your work in a court of law.  All numbers used in the design shall be documented with specific references to AASHTO and/or TxDOT standards.  All manual calculations shall be shown with specific references to AASHTO and/or TxDOT standards.

Design Project General Design Elements:   The following are general design elements that are to be incorporated into your design.

Design Project Part 1 will be to Define the Vertical Alignment for Road 2000 over the Freeway using GEOPAK.   Part of Design Project Part 1 is to calculate (1) the required grade G to minimize the tangent grade distance between the ends of the sag and crest curves given K_s, K_c, H, and W using the formula derived by Dr. Clyde E. Lee below; (2) the length of crest curve L_c, and (3) the length of sag curve L_s for 50 miles/hr design speed.

Design Project Part 2 will be to Design the Intersection Channelization of the Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange using MicroStation.   Part of Design Project Part 2 is to place a cell RC2KCC composed of three circular curves with radii of 120, 40, and 200 feet.   These values come from Exhibit 9-20 in the 2004 AASHTO Green Book on page 589 for an Angle of Turn of 90 degrees, a Design Vehicle of WB-50, and the asymmetric three-centered compound curve section and from Exhibit 9-25 in the 2004 AASHTO Green Book on page 602.

Another part of Design Project Part 2 is to place a cell RAMPCC composed of five circular curves with radii of 800, 400, 200, 400, and 800 feet and with arc lengths of 233.4, 120, 60, 120, and 233.4 feet respectively.   These values are derived from Exhibit 3-27 in the 2004 AASHTO Green Book on page 170 and Exhibit 3-23 in the 2004 AASHTO Green Book on page 181 for a minimum for 8% maximum superelevation and a design speed of 25 mph and from Exhibit 3-24 in the 2004 AASHTO Green Book on page 165.

When completed, Design Project Part 2 will look similar to the following:

Design Project Part 3 will be to Design the Freeway Entrance Ramp of the Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange using GEOPAK.   Part of Design Project Part 3 is to place a cell ENTRMP composed of a circular arc with 3025 foot radius and 6 degree sweep angle followed by a 1050 foot 50:1 tangent taper section.   If desired, the sweep angle may be modified by dropping the complex cell for the entrance ramp and using the modify arc angle command.   These values are derived from the Texas Department of Transportation Design Division Roadway Design Manual 2/2004 Table 2-3 Horizontal Curvature of High-Speed Highways and Connecting Roadways with Superelevation on page 2-14 and Figure 3-29 (US) Entrance/Exit Ramps For One-Way Frontage Roads on page 3-97.   The information can also be found online at http://www.dot.state.tx.us then TxDOT Library then Online Manuals then Search then List all manuals alphabetically then (a) Roadway Design Manual then 2 Basic Design Criteria then 4 Horizontal Alignment then Curve Radius and finally Table 2-3 Horizontal Curvature of High-Speed Highways and Connecting Roadways with Superelevation and (b) Roadway Design Manual then 3 New Location and Reconstruction (4R) Design Criteria then 6 Freeways then General Information and finally Figure 3-35 (US) Entrance/Exit Ramps For One-Way Frontage Roads.

Design Project Part 4 will be to Design the Freeway Exit Ramp of the Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange using GEOPAK.   Part of Design Project Part 4 is to place a cell EXTRMP composed of a circular arc with 3025 foot radius and 3.1859334418394 degree sweep angle followed by a 471.7948 foot tangent section.   The 340 foot portion of the tangent section is the deceleration length and starts where the exit ramp is 12 feet from the freeway lane edge.   These values are derived from the Texas Department of Transportation Design Division Roadway Design Manual 2/2004 Table 2-3 Horizontal Curvature of High-Speed Highways and Connecting Roadways with Superelevation on page 2-14 and Figure 3-33 (US) Typical Exit Ramps Without Frontage Roads on page 3-105.   The information can also be found online at http://www.dot.state.tx.us then TxDOT Library then Online Manuals then Search then List all manuals alphabetically then (a) Roadway Design Manual then 2 Basic Design Criteria then 4 Horizontal Alignment then Curve Radius and finally Table 2-3 Horizontal Curvature of High-Speed Highways and Connecting Roadways with Superelevation and (b) Roadway Design Manual then 3 New Location and Reconstruction (4R) Design Criteria then 6 Freeways then General Information and finally Figure 3-43 (US) Typical Exit Ramps Without Frontage Roads.   The deceleration length information can be found in the Texas Department of Transportation Design Division Roadway Design Manual 2/2004 Figure 3-36 (US) Lengths of Exit and Entrance Ramp Speed Change Lanes on page 3-113.   The information can also be found online at http://www.dot.state.tx.us then TxDOT Library then Online Manuals then Search then List all manuals alphabetically then Roadway Design Manual then 3 New Location and Reconstruction (4R) Design Criteria then 6 Freeways then Horizontal Geometrics and finally Figure 3-49 (US) Lengths of Exit and Entrance Ramp Speed Change Lanes.

Design Project Part 5 will be to Define the Superelevation and Complete the Grade-Separated, Two-Quadrant, Partial Cloverleaf A Interchange using GEOPAK.

Geometric Design Lab Spring 2011 web page

Latest Update: 11 Feb 2011 02:48 PM