reprinted with permission from Modern STEEL CONSTRUCTION | JULY 2017

THE SOUTHWESTERN MEDICAL DISTRICT—which is actually northwest of downtown Dallas—hosts nearly 2.6 million patient visits per year.

Home to medical facilities including Parkland Memorial Hospital, Children’s Medical Center of Dallas and the vast University of Texas Southwestern Medical Center complex, the district grew even larger in the last couple of years with Park-land’s addition of a new 2.5-million-sq.-ft, 862-bed hospital.

The new building is located across the busy six-lane Harry Hines Boulevard from the existing facilities. That’s where a new 830-ft-long curving pedestrian bridge comes in. The high-

visibility location mandated attractive structure that would contribute to the overall architectural expression of the hospital—but as a public hospital, an economical solution was essential and always the primary driving criteria. Structural steel truss framing was chosen as the solution to achieve both goals.

Due to a tight budget and the need to build over a busy road-way, both the fabricator and erector, Irwin Steel and Bosworth Steel Erectors, were added to the team early in the process to ad-vise structural engineer Datum Gojer Engineers on economics and constructability. During this process, the team determined that the most economical construction approach would be to erect the bridge in segments. The original concept was to ship the segments as fully fabricated boxes, but this wasn’t possible due to the size of the boxes and the constraints along the delivery path. There are a total of 15 segments of varying lengths, with 60 ft being the most typical. All of the vertical and diagonal truss members are 8-in. round hollow structural sections (HSS) with varying wall thicknesses, providing a uniform appearance along the length of the bridge. The top and bottom chords of the trusses are W14 members.

The floor and roof structures were also trussed. While the floor slab would have laterally braced the floor against wind forc-es once poured, the structure was exposed to torsional stresses due to the curved sections and lateral erection and wind forces during construction. The horizontal trusses in the floor and roof provided added stiffness during construction and contributed to resisting the torsional stresses in the curved sections.

The solution was to prefabricate the wall truss sections of each bridge segment in the plant and deliver them to the site to

A Healthy CONNECTION

BY THOMAS TAYLOR, PE, AND DAVE THOMAS, SE, PE

An attractive new pedestrian bridge over

a busy roadway stitches together

Dallas’ Southwestern

Medical District.

Thomas Taylor is principal design engineer and Dave Thomas is an associate, both with Datum Gojer Engineers.

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reprinted with permission from Modern STEEL CONSTRUCTION | JULY 2017

The bridge, by the numbers.

The new bridge links buildings on the Southwest Medical District campus near downtown Dallas.

The completed bridge. Installing one of the truss segments.

The sculptural HSS support in the middle of Harry Hines Boulevard.

Knight Visions Photography

PRAXIS

PRAXIS

Aerial Photography, Inc.

reprinted with permission from Modern STEEL CONSTRUCTION | JULY 2017

be assembled. The new hospital building was still under construction, but General Contractor Azteca worked with Bosworth to locate an area, intended for future parking, that was close to the bridge site and could be used for the assembly process. Irwin fabricated and shipped the wall trusses to the site, then connected the floor and roof elements to the trusses in this parking lot. Once a segment was completed, Bos-worth lifted it into place. Traffic on Harry Hines could not be affected during peak periods, so erection times were closely coordinated with the City of Dallas and the Texas State Highway Department. Bridge segment placement required a full northbound closure/detour over one weekend and a full southbound closure/detour over another weekend. Each time, the work began on a Saturday afternoon and was completed by Sunday afternoon.

Erection was broken into three phases: east, center and west. The east phase was on the new hospital side where the future parking lot could be used to assemble three segments with a crawler crane with minimal restrictions. The center segment was built in the median between the northbound and southbound lanes of Harry Hines us-ing a crane in a fenced-off area, and the west segments were built in sectioned-off areas of an active parking lot.

By using value engineering, a structural steel support was installed in the center of Harry

Hines Boulevard.

Two truss segments.

Erection was broken into three phases: east, center and west.

Interior glass and exposed trusses.

A 3D view of the framing for part of the bridge, including the HSS support.

Azteca

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DETAIL A

TYPICAL ROOF DRAIN FRAME

70'-6

ROOF "DROP IN" DRAIN FRAME LOCATIONS

99'-8

1 2

DRAIN POSITION MUST BE PUSHEDNORTH IN ORDER TO AVOID BEAM

DRAIN POSITION MUST BE PUSHEDNORTH IN ORDER TO AVOID BEAM

88'-6

2'-0

15'-0

9M19M2

3'-7

3'-7

9M3

2'-0

9M2

3'-7

76'-41 2

10M210M2

2'-0

9M49M4

3'-1 78

2'-0

3'-5 916

10M110M1

2'-0

78'-6

21'-32'-0

3'-7

3'-2

10M4

11M1

71'-10

DET. A

10M210M2

10M310M3

2'-0

3'-7

3'-7

2'-0

12'-812

2'-3

3 8

2'-0

10M5

9M5

11M511M4

3'-7

DRAIN POSITION MUST BE PUSHEDNORTH IN ORDER TO AVOID BEAM

11M211M3

83'-0

24'-6 12

2'-0

2'-0

3'-7

LESS

THA

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-7"

WH

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EQU

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101'-2

2'-0

77

77

316

3 SIDESTYP

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reprinted with permission from Modern STEEL CONSTRUCTION | JULY 2017

Erecting one segment during the day...

...and another at night.

And

re Gray

The bridge is made of 15 segments of varying lengths, with 60 ft being the most typical length.

Without it, a 250-ft clear-span curved truss would have been required, adding significant cost to the project. While there were concerns regarding the appearance of the support in the middle of the road—which was originally designed as a cast-in-place concrete structure with four columns curving upward from a single base—Datum Gojer proposed four steel columns to help resist torsional forces and to create an in-teresting steel “sculpture” as opposed to a more traditional column support. The architect approved the concept from an aesthetic standpoint, it was within budget and it solved struc-

tural issues in a visually pleasing way. It was also a more con-structable option.

By teaming up and conceiving the most economical struc-ture and construction process, the handsome architectural concept was built for $13 million, well under the initial budget of $20 million (the total cost of the hospital project was $1.2 billion). In addition, substantial completion was accomplished two months ahead of the contract date, and the final certifi-cate of occupancy was received weeks ahead of the hospital’s planned opening.

9/22/20140 For Field Use MDS ME

8/12/2014A For Approval ME MDS

REV. DESCRIPTION DATE DWN CHK

GENERAL NOTESELECTRODES:

CONN'S:

REF. DRG.

JOB USE

SHOP

APPROVAL

DESCRIPTION:

PROJECT NAMELOCATION

CONTRACTORDRAWN BY DATE

CHKD. BY DATE

JOB No. DRG. No. REV.

E70XX UNO

SEQ 4 HARRY HINES

PARKLAND SKY BRIDGE5201 HARRY HINES BLVD., DALLAS TX 75235

IRWIN STEEL

IRWIN STEEL15740 HIGHWAY 114

JUSTIN, TX 76247(817)636-2508

Detailer 08/12/2014

Checker 01/01/2000

1402 E402 0

4

D

D

D

C

C

B

B

A

A

D

A - A

B - B

C - C

D

D - D

E - E

HARRY HINES COLUMN SETTING PLAN

8'-0116

8'-0

E

E

WP 1a

WP 2a

WP 3a

WP 4a

WP 4

WP 3

WP 2

WP 1

416A2PIPE8STD

416A4PIPE8STD

416A5PIPE8STD

416A3PIPE8STD

416A1PIPE8STD

414C

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S30"

X1 2

415C1CHS30"X 12

412C1CHS30"X 12

413C

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X1 2

12

11 78

12 11 78

12

109

16

12

107

16

15'-1 18

3 38

7'-81116

7'-11 14

3 38

31116

16'-21516

31116

33

8

15'-1 14

33

8

312

15'-518

3127'-8

716

7'-11 38

8'-538

8'-478

31116 16'-21516 31116

16'-1014

WP 4WP 3

WP 4a WP 3a

338 15'-438 18

15'-778

WP 1WP 4

WP 4aWP 1a

312 15'-518 312

16'-0116

1 - 78Ø x 10A325N TYP

WP 1a

WP 1

WP 2a

WP 2

338 15'-114 338

15'-8

WP 2a

WP 2

WP 3a

WP 3

TYPICAL @ EACH BASEPLATE

The day it opened, patients were transferred from the old hospital into the new one. Donor names, etched into tree patterns, adorn the glass walls of the bridge and mir-ror tree patterns on the new hospital. The bridge was so well received that one donor even contributed the entire cost of the bridge, which is now named the Mike A. My-ers Sky Bridge. ■

OwnerParkland Health and Hospital System, Dallas

General ContractorAzteca Enterprises, Dallas

ArchitectsMoody Nolan, Dallas

Structural EngineerDatum Gojer Engineers, Dallas

Steel TeamFabricatorIrwin Steel, Justin, Texas

ErectorBosworth Steel Erectors, Inc., Dallas

reprinted with permission from Modern STEEL CONSTRUCTION | JULY 2017

An overhead view of the bridge spanning over Harry Hines Boulevard.

A segment awaiting erection.

An erection drawing of the HSS support.

Knight Visions Photography

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Construction NotesThe complexity of installing the trusses over a the major thoroughfare required street closures and constant mindful-ness of the traffic flow below. Prior to mobilizing, an inves-tigation of the street and substrate was performed to verify that both were able to support the cranes and loads. From there, we developed a detailed lifting plan.

Safety cables were required on the truss sections prior to and during erection. After this process, the crane was assembled at a nearby laydown area and moved into place after all traffic controls were implemented. Once the crane was secured, the trusses were moved into position, the rig-ging was completed and the trusses were lifted into place during nighttime hours on preapproved weekends. The trusses remained under load until reaching their final loca-tion with permanent connections made and the area se-cured. At that time, the crane released the load, equipment was demobilized and the street was reopened to traffic.

— Contributed by Azteca

The floor and roof framing was also trussed.

reprinted with permission from Modern STEEL CONSTRUCTION | JULY 2017

A Healthy CONNECTION

BY THOMAS TAYLOR, PE, AND DAVE THOMAS, SE, PE

An attractive new pedestrian bridge over a busy roadway stitches

together Dallas’ Southwestern Medical District.