ROBERT SILMAN ASSOCIATES, P.C./~r»MOI II TIM/-^ CM/^IMCCDO 88 UNIVERSITY PLACE. NEW YORK. NY 10003-4542 www.rsapc.comUUNoUL I IN(j hlNUINLLKo (212)620-7970 FAX(212)620-8157

INITIAL OBSERVATIONS AND RECOMMENDATIONS

FOR THE

GRINTON I. WILL LIBRARY BRANCH FACADE

Prepared For:

YONKERS PUBLIC LIBRARYStephen Force, Director

One Larkin CenterYonkers, New York 10701

Prepared By:

ROBERT SILMAN ASSOCIATES88 University Place

New York, NY 10003

October 6, 2005

File# 10916

Introduction:

At the request of Mr. Stephen Force, Director of the Yonkers Public Library, Robert SilmanAssociates (RSA) performed a cursory visual observation of the pre-cast concrete panels on the facades ofGrinton I. Will (Sprain) Branch Library, Central Park Avenue, Yonkers, New York. On June 8, 2005,Bob Silman, P.E., Paul Askham, P.E. and Eytan Solomon visited the site.

In general, the facade panels have noticeable bowing deformation and lateral displacement. Themost pronounced conditions are on the East elevation of the building. In addition to our visualobservations, RSA reviewed original architectural and structural drawings and two previous engineeringreports. This report includes a comparison of the conclusions offered by these reports.

Initial Visual Observations;

The fa9ade panels are pre-cast concrete with an exposed aggregate surface. The typical distressedconditions are outward bowing of individual panels about their horizontal in-plane axis. Some panels, onthe East fafade, are bowed out at their centers up to 2" relative to adjacent panel edges. Other panels onthe East elevation, above the garage and below the conference room windows, appear to be slidingoutward at their edges, again up to 2" relative to adjacent panels. The most pronounced bowingdeformation is at the East elevation of the building, but similar deformation was evident to a lesser degreeon the South and North sides, at both the ground and roof levels.

We did not observe spalling concrete on the pre-cast facade panels. Some minor spalling of thecast-in-place concrete structure was noted, but this does not relate to the facade panel conditions.

Review of Archive Drawings:

Original drawings were acquired from the City of Yonkers Department of Housing and Buildingsand also from Mr. Russell Deutschen of the Public Library. The drawings are by the Architect EliRabineau and the Structural Engineer Lev Zetlin, dated 1959. Although the drawings are detailed on mostaspects of the building construction, the pre-cast facade panel details are schematic and not specific; thepanels are indicated as 2" thick and haunched to 3.5" thick at each end. In general, the observed wallconstruction appears to be 10" concrete block with 4" air space and 2" thick concrete panels. Probes willexpose the wall and panel construction for verification with the existing drawings. Anchorage clips arevaguely referenced on the drawings, but not specific concerning the location, frequency, or type. Thedetails concerning the anchorage and panel fabrication may have been finalized during construction.Unfortunately, shop drawings and as-built drawings could not be located.

Review of Engineering Reports (by others):

1. Hastings Design Group, dated 19992. Orpheus Associates, dated 2003

The above referenced reports suggest that differential thermal expansion between the exposedaggregate surfaces and the concrete bases of the panels is the cause of the distress.

Robert Silman AssociatesConsulting Engineers

The Hastings report states that: "Upon removal of one bowed face panel, the panel seemed intactwith 'A " diameter reinforcing steel mesh embedded in the panel, and in full contact with the surroundingconcrete. The aggregate surface did not show signs of separation from the base concrete of the paneleither." This statement, in conjunction with the absence of spalled concrete at the panels, implies that theHastings report had contradictory conclusions. It is possible that the differential expansion is occurringbetween the panels, as whole units, and the backup block walls and not between the faces of the panelsand their bases. Removal of several panels and investigation of the exposed wall construction willconfirm or reject this theory.

Both of the above referenced reports indicate that corrosion of the steel anchorages as both thecause, and effect, of the deformation. The Hastings report states that there is rust on the steel anchorages.RSA suggests removal of several panels to determine whether the steel anchorages are deteriorated or not,and if and how the anchorages have contributed to the bowing and displacement of the panels.

Initial Conclusions:

The existing drawings indicate that each individual panel is anchored, and therefore constrained,at each of its longitudinal ends, to the block backup wall, via steel relief angles. The block backup wall isconstrained at the concrete floors and roof. The intent of the probes is to determine if the combinedeffects of differential thermal expansion, between the exterior panels and the interior backup block wall,in conjunction with the different types and locations of constraint resulted in the bowing and displacementof the panels. The amplitude of the bowing has increased, incrementally, over the past 45 years.

Hastings and Orpheus concluded that there is no practical solution for repair of the bowedconcrete panels and that the only solution is to fabricate new pre-cast panels to match the existing panels.The results of the probe investigation will confirm or reject this statement.

Recommendations:

In an effort to properly understand the existing construction and to provide appropriate remedialconstruction documents, we recommend that several panels be temporarily removed from the buildingfacades. These removals, or "probes", will facilitate an investigation, by RSA, of the panel fabrication andthe conditions of the miscellaneous steel and anchorage systems.

Please find enclosed sketches SK-1, by RSA, dated 09.16.05, indicating the suggested locationsof panels to be removed.

If you should have any questions about this report or probe drawings, require further information,or require suggestions for suitable contractors for the probe work, please contact us.

Sincerely yours,

ROBERT SILMAN ASSOCIATES, P.C.

Robert Silman, P.E.

Robert Silman AssociatesConsulting Engineers

East elevation over garage, bowing and displaced panels

East elevation over garage, bowing and displaced panels

South main fa?ade, bowing panels

Robert Silman AssociatesConsulting Engineers

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Robert Silman AssociatesConsulting Engineers

:D METHOD OF REMOVAL

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SOUTH ELEVATION

ROBERT SILMANASSOCIATES, P.C.CONSISTING ENGINEERS

GR1NTON I Via BRANCH LIBRARY1450-1514 KNTRAL PARK AVENUE,

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