C O N S U L T I N G E N G I N E E R S , I N C .

Sample Project:

Collar Joint Stabilization Grace Episcopal Church, New Bedford, MA

Owner: Grace Episcopal Church

Engineer: Structures North Consulting Engineers, Inc.

General Contractor: Aniceto, Inc.

Grouting Contractor: Special Breaks, LTD

C O N S U L T I N G E N G I N E E R S , I N C .

The Challenge: The Grace Episcopal Church in New

Bedford, MA (USA) was constructed

in late 19th century as a stone

masonry tower with massive brick

pilasters at each corner. These

shared load with the stone shaft of

the tower, and above transitioned to

brick piers that supported nearly all of

the weight of the combined brick and

stone spire.

As the tower acclimatized and aged,

the brick piers swelled, as materials

normally do, and attempted to

additionally lift the structure causing

the tower to contort.

C O N S U L T I N G E N G I N E E R S , I N C .

f

Field notes

describing

the masonry

contortions

f

As the brick pilasters grew, the

stone shell of the tower did not.

This caused the brick piers to

“fight” the shell, and one of the

piers to peel itself off.

Delaminating

and

Separating

Pilaster

C O N S U L T I N G E N G I N E E R S , I N C .

Delaminating and

Separating Pilaster

C O N S U L T I N G E N G I N E E R S , I N C .

The brick pilaster had

separated from the stone shell

by up to 4-inches

C O N S U L T I N G E N G I N E E R S , I N C .

The brick pilaster movement

caused a similar buckling effect

in the stonework below, and a

similar movement

C O N S U L T I N G E N G I N E E R S , I N C .

In its buckled state, the pilaster had a

fraction of its original strength, as 24-

inches of composite masonry became

8 to 12 inches of brick running past

12 to 16 inches of stone.

While one consider shoring and

reconstructing the separated brick,

the intensity of the structural load and

the precariousness of its support

precluded this. Additionally, simply

pinning the pilaster back to the stone

back-up would only have resulted in

two thin elements tied together, rather

than one thick element- the

perpendicular wall was made

discontinuous below the adjacent

roof by a beam supported opening.

A system would need to be selected,

or devised, that would compositely

bond the corner of the tower back

together.

Delaminated

and

Buckled

Pilaster

Massive

Structural

Load

C O N S U L T I N G E N G I N E E R S , I N C .

In-Place Stabilization Options:

• Injection Grouting Systems- no cross tie when used alone, and thus no way of

resisting internal grouting pressures without external bracing or tying.

• Resin-Based Anchor Systems with Screen Tubes- marginal ability to span

gaps, shear transfer only through dowel action.

• Mechanical Wedge Anchor Based Systems- no shear transfer

• Sock Anchor Systems- better but shear transfer dependent upon dowel action.

• Self-Grouting Port Anchor System- The only system that not only ties

both surfaces against further separation, but while provides a port through

separated cavities and can be cleaned, inject a compatible grout and

knitted back together.

C O N S U L T I N G E N G I N E E R S , I N C .

Port Anchor Design Parameters: Non-corroding all stainless steel construction.

Must provide a clear pathway for inspection and cleaning of void then injection of grout

while resisting at least two 3-foot lifts of grouting pressures.

Detail to suit loading, grouting conditions and injection pressures- grouted anchor socks

possible at either or both ends, with bearing plates available in lieu of or in addition to the

socks.

Removable threaded rods socket into outer ends of anchor in order to directly attach

dunnage to counter injection pressures- The port anchor doubles as the fastening system

for the dunnage, avoiding the need for external bracing.

Double ended anchors possible where dunnage needed on both faces of masonry.

Anchor shear capacity not reliant on dowel action but based upon shear friction “haunch”

theory, with the maximum tie capacity provided at the point of best grout compaction- At

the anchor. No shear lag, no bending or crushing, only direct fixation.

Hollow or open shank allows insertion of secondary rods for additional shear capacity, and

electric heating wands if needed for installation during cold weather conditions.

C O N S U L T I N G E N G I N E E R S , I N C .

Void Filling Grout Design Parameters

• Must be flowable and have ultra-low shrinkage.

• Must stiffen fast enough to safely support an unlimited number of successive 36-inch grout lifts

every 20-hours.

• Must be more breathable than Cement, more forgiving of building movements, and generally

more compatible with older structures that have lime mortars.

• Must cure without needing significant carbon from the atmosphere.

• Should have a proportionately high tensile strength and a low compressive strength with good

adhesion.

•Should meet the material requirements of ASTM C1713: Standard Specification of Mortars for the

Repair of Historic Masonry to serve as a fluid-applied historic mortar replacement

C O N S U L T I N G E N G I N E E R S , I N C .

C O N S U L T I N G E N G I N E E R S , I N C .

Anchor Installation

C O N S U L T I N G E N G I N E E R S , I N C .

Sock Inflation

C O N S U L T I N G E N G I N E E R S , I N C .

Grout Mixing

C O N S U L T I N G E N G I N E E R S , I N C .

Void Filling

C O N S U L T I N G E N G I N E E R S , I N C .

Port Removal

C O N S U L T I N G E N G I N E E R S , I N C .

Completed

Stabilization