f parkmonroe mcdonald april11

7/27/2019 F Parkmonroe McDonald April11

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2/3STRUCTURE magazine April 201127

EXIST. CONC. COL.

ROUGHEN SURFACE

TO " AMPLITUDE

DOWEL SEE 14/S11

CONC. BEAM SEE

SCHEDULE FOR SIZE &

REINF.

PROVIDE 1 " NOTCH

6 - #7 - DRILL & EPOXY

INTO EXIST. CONC.

COL. W/ 6" MIN. EMB.

1'-

6"

1'-

6"

2'-

3"

1' - "6"

1"

4 - 1" DIA. A36

THREADED U

RODS W/ NUTS &

WASHERS - HOLD

RODS 6" FROM

EDGE OF HAUNCH

4 - #5 TIES - DRILL &

EPOXY INTO EXIST.

CONC. COL. W/ 6"

MIN. EMB.

P 3/4x 9x WIDTH OF

COL.

L

Te outdoor terrace, with up to 3 feet of soil in the landscapedareas, had a combined service load reaction o 250 kips at each slab toexisting column connection. o transer this large load to the existing

columns, shear collars were designed which relied on a combinationo shear riction and a 1-inch bearing around the perimeter o thecolumn (Figure 4, page 28).

Increasing Floor Capacities for the New Use

In an efort to increase the load carrying capacity o the 10-inch 2-wayslabs, 3-inch lightweight structural bonded overlay was utilized. Tis

occurred at several areas: 1) the north end o the 49th oor, where theuse changed rom oce (70 pounds per square oot) to outdoor terrace(100 pounds per square oot); 2) the roo o the 50th oor mechanical

level where a portion was upgraded to 100 pounds per square oot oran outdoor terrace; and, 3) the second oor oce space (70 poundsper square oot) to the tenant storage room (125 pounds per squareoot). In all o the above cases, the structural capacity was increasedefectively by taking advantage o the existing bottom steel reinorce-ment and the additional top steel reinorcement in areas o negativemoment. Tis is not always the case as, oten the additional weightof the overlay or oor height restrictions eliminate this approach

Figure 3: New concrete support beam below new swimming pool. Note the cast haunch and plate washer at back side of existing concrete column.

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3/3STRUCTURE magazine April 201128

EXIST. CONC. COL.

- SEE PLANS FOR

COL. SIZES

CHIP OUT SLAB TO

ACCOMMODATE NEW

THREADED RODS

AND GROUT SOLID THREADED ROD

W/ NUT

EXIST. CONC. COL.

- SEE PLANS FOR

COL. SIZES

3"TY

P.

3" TYP.

5 - " DIA.

THREADED ROD

U-BAR

12"

2-P x 3x3 PER

U-RODS

L

PLAN SECTION

Figure 5: Additional shear reinforcement detail to increase the punching shear capacity due to theunbalanced moment created by new roof openings.

to increasing capacity. As surface prepara-tion was key to ensure proper bond betweenthe existing 10-inch slab to the new 3-inchstructural overlay, construction documentsand specications dictated strict and clearinstructions to prepare the surface, basedon the guidelines by International ConcreteRepair Institute (ICRI). Tese guidelinesinclude roughening the surace, wetting the

substrate to provide a saturated surace dry(SSD) condition at the time o placement,application o a neat sand cement slurry, andproper curing procedures.

Large Openings in

Slabs and Walls

o provide additional outdoor space or theresidents, large openings were made in theroo slab at the north hal o the 49th oor.Te openings, which ranged in size rom 19eet by 9 eet to 19 eet by 17 eet, were stra-

tegically placed to avoid column strips. Teresulting unbalanced moments at columnsincreased the punching shear at several loca-tions. o increase the punching shear capacityand to avoid an underside concrete shearcollar for aesthetic reasons, u-shaped rein-orcing steel was drilled through the slab onall our sides (Figure 5). Te additional steelpushed the critical shear section away romthe column and thus increased the capacity.Tis analysis was completed similar to shearstud reinorcement in new construction.Te redesign and upgrade o the mechanical

systems necessitated large duct penetrationsthrough the existing 12- to 16-inch thick con-crete shear walls. A nite element structuralanalysis model was developed to evaluatevarious locations and conguration o new openings in the shear walls,and their efect on the structures lateral orce resisting system. Temechanical engineer was provided with a list o preerred locationsby the Structural Engineer o Record or the new openings, whichhelped accelerate the design and coordination process and minimizedthe efect o the mechanical upgrades on the structures lateral system.One o the major challenges o this project was that it took place

while 40 oors o oce and retail space below were occupied. Allconstruction materials were lited by using the reight elevator which

limited the length o the steel reinorcement to 12-oot long sections.

Terry McDonald, P.E., S.E. ([email protected])is a senior structural engineer with Klein and Homan, Inc. andserved as project manager for the adaptive reuse of 55 E. Monroe.

Homa Ghaemi, P.E., S.E. ([email protected]) isan Associate Principal with Klein and Homan, Inc. and served asthe Principal in Charge of this project.

Structural Engineer: Klein and Hofman, Inc., Chicago, ILDeveloper:Glenstar Properties, LLC and Walton Street Capital, LLC

Architect of Record: Goettsch Partners, Chicago, ILAssociate Architect: Papageorge Haymes Partners, Chicago, ILGeneral Contractor: Linn-Mathes, Inc., Chicago, IL

Acknowledgements

EXIST. COLUMN

NEW FLOOR

SLAB

ROUGHEN SURFACE

TO " AMPLITUDE

EXIST. 1st FLOOR SLAB

#6 C BAR @ 6" SPA. (5 EA.

FACE) EPOXY - GROUTED

W/ 3" EMBED.

1 " MIN.

8"

1' - 4"

2'-

"

4 - #6

6"3"

B

B

AA

SECTION A - A

Figure 4: Shear collar connection at new 49th oor slab to existing concrete column interface.

In addition, the weight limit on the reight elevator resulted in 1,600round trips or the concrete buggies alone. Needless to say, careulreview o the reinorcing steel shop drawings was necessary with thehigh number o splices.By employing various methods o strengthening, the architect and

developer were given the freedom and versatility to dream upsignicant changes and deliver an exceptionally unique urban livingexperience. Te new residents can truly live by the lake as they takeadvantage o all that Downtown Chicago business, theater and shop-

ping districts can ofer.

f parkmonroe mcdonald april11

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