Bethesda Triangle

Brian GroarkConstruction Management Faculty Consultant:

Dr. Messner

Bethesda Triangle 14 story apartment building Additional 4 stories below grade for

parking 580,000 SF Cast in place concrete structure Offices and retail on plaza level High end apartments on floors 12-14

Bethesda Triangle Owner: Bethesda Triangle, LLC CM: Encore Development Construction began on February 14,

2002 Phased occupancy Little site space

Bethesda Triangle

Thesis Overview SIPS Schedule Change emergency generator Change formwork Guidelines for mold prevention

CM Depth

Short Interval Production Schedule (SIPS)

Reasons for Using SIPS Lack of solid schedule for the project Project will finish extremely late Needs solid, detailed schedule for all

aspects of the project Repetitive floors work well for SIPS

SIPS Create a detailed SIPS schedule for

the concrete structure Compare it to the original duration

for the structure

SIPS Each floor is broken up into 4

sections Crews follow in progression through

all the sections and floors Each section has the same duration

Section Layout

SIPS Floors G4 – plaza level are the same Floors 2 – 14 are the same Each section takes 2 weeks to

complete

SIPS

Results Original duration was 44 weeks SIPS duration is 31 weeks Time saved is 13 weeks

Electrical Breadth

Change Emergency Generator

Original Generator 2 mega-watt generator Power entire building in the event of

a black out Sell extra power back to the grid at

times when the costs of running the generator are less than electricity costs

New Generator 350 kilo-watt generator Power only emergency systems

Emergency lighting and alarms Fire pump Stairwell pressurization Smoke exhaust Elevator

Initial Costs

2 mega-watt – $540,000 350 KW - $40,000

Cost Analysis

Hour Watts/SF Total SF Total KWHr Weekday Weekend0 1 380000 380 1900 7601 0.75 380000 285 1425 5702 0.65 380000 247 1235 4943 0.6 380000 228 1140 4564 0.5 380000 190 950 380

APARTMENT

Cost Analysis

Totals KWH Dist Tran Generation Total cost (week)Off peak 47563 0.289 0.266 1.99 $1,210.48On peak 26715 0.289 0.266 4.121 $1,249.19

Inter 27285 0.289 0.266 3.485 $1,102.31

$3,561.99

Cost Analysis Costs of running the generator to

power the building were compared to purchasing electricity on an hourly basis

Plus Garage Cost per KWH total cost Total cost to run gen Extra Power (KWH) profit from selling power Net Cost Profit from running gen580 2.545 $14.76 $117.13 1220 $31.05 $86.08 -$71.32485 2.545 $12.34 $117.13 1315 $33.47 $83.66 -$71.32447 2.545 $11.38 $117.13 1353 $34.43 $82.70 -$71.32

Results No profit is shown from running the

generator Price of diesel fuel has increased

Recommendation Use proposed generator Initial cost savings of approximately

$500,000

Structural Breadth

Change Formwork System

Original Formwork Traditional formwork

Built in place with shoring Stripped and re-shored

New Formwork System Symons flying truss system

Large aluminum forming tables are flown into position with a crane

Much higher productivity

Slab Original slab was a flat slab with

drop panels Flying truss system can only be used

with flat plate slabs Slab was redesigned to a 10” flat

plate to accommodate the new forming system

Productivity With a crew of six workers:

Hand set system – 544 sq ft per day Flying truss system – 7500 sq ft per day

System Sq Ft Sq ft /day DurationLabor Costs /

DayTotal Labor

CostsHand Set - Flat Slab w/ Drop Panels 380,000 544 699 $1,544 $1,078,529Flying Truss - Flat Plate 380,000 7500 51 $1,544 $78,229

Comparison

System Sq Ft Form Costs / SFTotal Mat.

CostsHand Set - Flat Slab w/ Drop Panels 380,000 $0.92 $349,600Flying Truss - Flat Plate 380,000 $0.40 $152,000

System Sq Ft Slab Costs / SFTotal Slab

CostsHand Set - Flat Slab w/ Drop Panels 380,000 $5.15 $1,957,000Flying Truss - Flat Plate 380,000 $5.82 $2,211,600

Form costs

Slab Costs

Results Total cost savings of approximately

$950,000

Research

Mold Prevention Guidelines

Effects of Mold in Buildings Less serious symptoms of toxic mold

poisoning Skin rashes Fatigue Coughing Headaches

Effects of Mold in Buildings More serious symptoms of toxic

mold poisoning Impaired breathing Memory loss Hearing, speech, and eyesight

degradation Loss of balance

Causes of Mold Moisture

Leaks Condensation

Guidelines for Prevention

1. Clear details of all exterior penetrations

2. Design must provide for adequate roof drainage

3. No changes to design of enclosure without architects approval

4. Proper slope of grading

Guidelines for Prevention

5. Drywall must remain dry 6. Complete enclosure of building

prior to drywall installation7. Use drywall designed to reduce

mold growth8. Proper inspection9. Proper operation of equipment

Conclusions SIPS can reduce schedule duration Larger generator is not profitable at

current fuel prices Flying truss formwork greatly

increases productivity Early mold prevention can save

costly repairs in the future

Questions