Book or guidelines for joint spacing in retaining walls 1

I'm looking for guidelines or a book regarding the spacing of joints in concrete retaining walls. All my text books go to great detail for concrete and reinforcing design, but don't say anything about joints.

Do you run expansion joints through the footing?

For an 8' wall, what would be the spacing for expansion, construction, and contraction joints? What determines the spacing?

When footings are stepped and the bottom of one footing is 2' above the top of the lower footing, is there a concrete connection, or just 2' of dirt between the ends?

 

[boo1]

Expansion Joints - Vertical expansion joints or movement control jointsto account for expansion due mainly to temperature changes and moisture conditions. On changing from a saturated to a dry condition, average concrete will contract approximately 2/3 of an inch per 100 linear feet. Place Vertical expansion joints 1/2 inch in width at Max intervals of 90 feet throughout the length of retaining walls and fill with expansion joint material. All exposed edges shall be beveled 3/4 inch. The footings should incorporate an expansion joint too.

Construction Joints - These can be vertical or horizontal joints between successive pours of concrete. When it is not practical to pour the wall to full height in one operation, ensure construction joints are truly horizontal and provide a bond between the sections with keys formed by beveled timbers. Where necessary to provide construction joints in the length of the wall, ensure joints are truly vertical and provide a bond between the sections with shear and sliding resistance keys formed by beveled timbers. Spacing depends of project and crew.

Contraction Joints - Vertical joints cut (or formed)into the wall. Allows the concrete to shrink without showing the cracks. Place 24-inch long, 1/2-inch diameter, commercial grade steel dowels and 12-inch long, 5/8-inch inside diameter, commercial grade steel dowel sleeves across the joint. Provide caps on one end of the sleeves. Grease one end of the dowel and insert into the sleeve. Space dowels and sleeves at 12-inch intervals along the centerline of the wall stem. Do not pass reinforcing steel through either joint. Seal joints from top to bottom with waterstops. Provide contraction joints at 30-foot intervals


One area that can be commonly overlooked, or at least underestimated, is the necessity to drain the backfill of rainwater and/or groundwater. Hydrostatic pressure can cause or induce retaining wall failure, or at least damage
Provide 4-inch weephole drains at 8-foot intervals through standard gravity. Weepholes should have material between the wall and the backfill to prevent fines migration, and weephole clogging. If required drainage lines are required, consider perforated pipe and wrapped in geotextile or buried in a granular filter bed, and serve to carry water to the weepholes from areas deeper within the backfill.

 

Thank you boo1. One more question dealing with joints. If you have a 90 degree angle in the wall would you make it continuous around the corner or put an expansion joint at the corner? How about angles less than 90 degrees, such as 30 or 45 degrees?

 

[boo1]

The ones I have seen are continous.

 

[DTGT2002]

Steps in footing must be connected to contain the earth below and maintain bearing upon the earth. A typical detail would have the bottom of the lower footing sloping up to the bottom of the high footing at a slope of 1 to 1 or 2 to 1. Analysis of the loading would dictate the proper detailing. Have you looked for a soil/foundations textbook. Foundation and wall design are more the focus here than in reinforced concrete design books.

Spacings of joints will vary with the site condiiotns, but minimums should be found in ACI 318

Whether or not to place expansion joints at the corners is a function of wall design. If the wall is designed as a fully cantilevered retaining wall, then it may not need to tie back into the soil or be fully connected to the side wall, allowing the wall to act as a beam. Good luck.

 

[versaengine]

check out the crsi (concrete reinforcing steel institute) handbook.