November 30, University of Virginia Facilities Management Engineering & Design Division P.O. Box Charlottesville, VA

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1 University of Virginia Facilities Management Engineering & Design Division P.O. Box Charlottesville, VA Attention: Reference: William Blodgett, AIA Project Manager University of Virginia Dear Mr. Blodgett: Whitlock Dalrymple Poston & Associates, P.C. (WDP) has completed the investigation of Gilmer Hall to evaluate the cause of parapet stone masonry distress and determine if there are any unstable conditions that might pose a safety issue to pedestrians and building occupants. The investigation consisted of an initial review of the original construction documents, visual observations of the distress in the field, and probe openings at the top of the parapet wall. The following report summarizes the findings of this investigation and our recommendations for correcting the deficiencies observed in the parapet wall. BACKGROUND Gilmer Hall was built in the early 1960 s (Photograph 1). The building can be separated into three main structures (Structures A, B, and C) as shown in Photograph 1. Structures A and B were included in the current investigation, and Structure C was excluded. It is noted that almost all the distress was observed in Structure B and the report will focus on this portion of the building. The building is three stories tall on the north elevation and five stories tall on the south elevation (Photograph 2). Conventional reinforced concrete was used for the structural framing system. Stone, architectural block masonry, and clay brick were used for cladding. During recent inspections by UVA Facilities personnel, visual signs of distress and displacement were observed in the exterior stone units of the parapets and column SO. NORWALK, CONNECTICUT AUSTIN, TEXAS CHARLOTTESVILLE, VIRGINIA MANASSAS, VIRGINIA GATEWAY BLVD. SUITE 200 MANASSAS, VA TEL FAX

2 Page 2 covers. These displacements and visible signs of distress, coupled with the proximity of student pedestrian traffic prompted the investigation. Test Cut #2 Test Cut #3 Test Cut #1 N Structure C Structure B Structure A Photograph 1 Gilmer Hall Parapet Stone Architectural Block Masonry Column Cover Photograph 2 Gilmer Hall North Elevation

3 Page 3 DOCUMENT REVIEW WDP reviewed the original construction documents for the building (dated 1961) related to the design and construction of the exterior parapet wall. The exterior parapet wall stone was designed to be supported by a shelf angle in a slotted kerf of the stone and stone strap anchor at the top of the wall as shown in Figure 1. The shelf angle is bolted to the structural concrete beam with wedge inserts embedded in the element. Figure 2 shows the stone detail surrounding the concrete column. Note that dovetail anchors were designed to laterally restrain the column cover panels. Stone Anchor Tieback Shelf Angle Figure 1 Parapet Stone Anchorage Detail

4 Page 4 Concrete Column Column Cover Column Cover Dovetail Anchor Figure 2 Column Cover Detail VISUAL OBSERVATIONS Photograph 3 depicts the typical stone distress at exterior parapet wall of the Gilmer Hall. The distress was observed at the 5 th column cover location from the west end on the north elevation. The parapet stone directly above the column cover measured approximately 5/8 inch of out-of-plane displacement (Photograph 4). The parapet stone was also slightly higher in elevation with regard to the adjacent parapet stones with roughly 1/8 inch of relative vertical displacement measured at the joint. The parapet stone appeared to be bearing directly on the column cover below. The joint between the parapet stone and the column cover was filled with mortar. The 3 inch thick column cover also measured 3/8 inch of out-of-plane displacement (Photograph 5). The column cover displacement was relatively large at the top and decreased as they progressed to the lower column covers. It appeared that the top two column covers were the most significantly displaced. Similar conditions were observed at the 4 th column cover location from the west end on the north elevation. Approximately 1/2 inch of out-of-plane displacement was measured at the bottom of the parapet stone and 3/8 inch of relative vertical displacement was measured between the parapet stone bearing on the column cover and

5 Page 5 the adjacent parapet stone (Photograph 6). The column cover also measured about 1/4 inch of out-of-plane displacement. Other select column cover locations on the north elevation were examined using a boom lift. Similar distress was observed at the top of most column cover locations. The south elevation was examined from the 1 st floor balcony level with binoculars. Although visible displacement was observed, the distress appeared to be less severe than the north elevation. The column cover displacement was also observed at building corners of Structure B shown in Photograph 1. Separation was relatively large at the top of the cover and decreased to lower panels (Photographs 7 through 9). The column cover connection was examined non-destructively using a pachometer to identify anchors, angles, or other attachment details to the back-up. Although two vertical pins were identified in the mortar joint dowelling the top and bottom of the stone units together (Photograph 10), no dovetail anchors were found in the joint, as indicated in Figure 2. The existing column covers included two pins per unit (which may or may not have been retrofit anchors installed in post construction) which were placed at 1/3 and 2/3 points of the cover height. The existing flexible sealant covering the head of the pin was removed from the face of the panel revealing an unbonded condition of the pin to the panel (Photograph 11). The anchor bolt appears to be fixed at concrete column backup, but no engagement of the column cover was observed to transfer the lateral loads. Photograph 3 Typical Parapet Stone Displacement Over Column Cover

6 Page 6 Parapet Stone Over Column Cover Photograph 4 Parapet Stone Out-of-Plane Displacement (Looking up) Parapet Stone Over Column Cover Side Column Cover Front Column Cover Photograph 5 Column Cover Out-of-Plane Displacement (Looking up)

7 Page 7 Parapet Stone Over Column Cover Photograph 6 Parapet Stone Relative Vertical Displacement (Looking up) Photograph 7 Column Cover Displacement at Northwest Corner (Looking Down)

8 Page 8 Photograph 8 Column Cover Displacement at Northeast Corner (Looking Down) Photograph 9 Column Cover Displacement at Southeast Corner (Looking Down)

9 Page 9 Vertical Pin Photograph 10 Column Cover Connection Void Around Anchor Bolt Photograph 11 Column Cover Pin in Face of Panel

10 Page 10 TEST CUTS Three test cuts were made at the top of the wall to examine the as-built conditions of the parapet and the connection for the parapet stone. All three test cuts were made by cutting the coping flashing material at the top of the parapet wall. Two test cuts were made at the north elevation where the parapet stone units appeared to be significantly displaced. One test cut was randomly selected at the south elevation. The existing coping flashing was fabricated from lead coated copper set over a membrane strip and secured with a sheet metal cleat fastened to the parapet stone and spanning to a reglet in the concrete beam (Figure 3, and Photographs 12 and 13). The first test cut was made on the north elevation parapet wall, 4 th column cover location from west end. The parapet stone was 7 inches thick at the top of the section and 5 feet long. Unlike the stone anchor tieback embedded in Figure 1, two stone strap anchors were observed per stone and were located approximately 6 inches from each end. 1 inch wide and 1/8 inch thick galvanized steel was used for the stone strap anchors that were bent and inserted into the reglets in both the parapet stone and the concrete beam (Photograph 14). As shown in Figure 3, the strap anchor end in the concrete beam was bent twice and shaped into the dovetail reglet, but the opposite end of the stone strap anchor in the parapet stone was only bent once with a 90 degree hook and 3/4 inch leg. The parapet stone and concrete in the vicinity of the strap anchor was closely examined, and no cracking was observed at the anchor bearing locations. However, a crack was observed at the bridging mortar parallel to parapet wall. A vertical leg of the shelf angle and one anchor bolt were examined from the test cut; no sign of corrosion was observed (Photograph 15). The second test cut was made on the north elevation parapet wall, 5 th column cover location from the west end. Similar coping flashing construction was observed and the stone strap anchorage detail was also the same. A 1/4 inch wide crack was observed at the interface between the bridging mortar and the concrete beam at the top of the parapet wall (Photograph 16). One end of the strap anchor had a dovetail end (Photograph 17). No corrosion was observed at the top of the shelf angle from the test cut opening. However, mild corrosion was observed at the bottom of the shelf angle which was identified by a borescope examination (Photograph 18). The third test cut was made on the south elevation parapet wall, 5 th column cover location from the west end. Similar coping flashing and strap anchorage construction were observed as compared to the north elevation test cuts. A light corrosion was observed at the shelf angle anchor bolt.

11 Page 11 In all three test cuts, the sealant material placed in the concrete beam reglet was severely deteriorated or completely failed at many locations. In addition, the membrane sheet under the flashing was also deteriorated and the edge embedded in the reglet was very stiff and brittle. Other distress was observed during the field investigation including column cover joint and stone joint material deterioration (Photographs 19 and 20); parapet wall concrete beam joint distress (Photograph 21); parapet wall joint waterproofing cracking (Photograph 22); parapet wall panel cracking (Photograph 23); and parapet concrete column cracking (Photograph 24). Figure 3 Parapet Coping Flashing Detail

12 Page 12 Photograph 12 Parapet Coping Flashing Prior to Removal Photograph 13 Parapet Coping Flashing After Top Metal Flashing Removal

13 Page 13 Photograph 14 Parapet Stone Anchor Tieback Photograph 15 Parapet Stone Shelf Angle and Bolt

14 Page 14 Photograph 16 Parapet Stone Anchor Tieback Photograph 17 Dovetail End for Parapet Stone Anchor Tieback

15 Page 15 Photograph 18 Parapet Stone Shelf Angle Corrosion Photograph 19 Column Cover Joint Material Deterioration

16 Page 16 Photograph 20 Stone Joint Material Deterioration Photograph 21 Parapet Wall Concrete Beam Corrosion

17 Page 17 Photograph 22 Parapet Wall Joint Waterproofing Cracking Photograph 23 Parapet Wall Panel Cracking

18 Page 18 Photograph 24 Parapet Concrete Column Cracking DISCUSSION Shrinkage and creep occur in concrete over time. These are common material characteristics of concrete. Concrete shrinkage occurs as the concrete dries out, changing its overall volume. Water content in the concrete mixture plays a significant role in concrete shrinkage and may vary significantly around the building. Concrete creep is the slow deformation of a material over considerable length of time from a constant stress or load. Shrinkage and creep are the main components in concrete frame shortening and often causes a problem with cladding when they are not controlled. According to W.G. Plewes, Cladding Problems Due to Frame Movements in a modest 60 ft. high building the cumulative shortening of the frame could amount to as little as 0.10 inch or more than 0.6 inch. Gilmer Hall is approximately 36 ft. tall where the column cover is place which would translate to up to 3/8 of an inch of relative movement between the frame back-up and the stone covers themselves. While the frame shortening occurs in the main structural frame, the cladding components of the stone column covers do not change in length resulting in differential movement. The stone at the top of the wall is then lifted by the stone below off of the shelf angle and the accompanying toe bar, effectively disengaging it from the frame. Because the column cover components do not have adequate connections to resist lateral movement, these elements also have progressively traveled away from the building.

19 Page 19 CONCLUSIONS Based on the results of the investigation conducted by WDP on Gilmer Hall s exterior parapet wall, the following conclusions have been developed: The current building distress in the stone panels of the parapets on Gilmer Hall appears to be related to concrete frame shortening of the structure. The parapet stone directly above the column cover experienced significant outof-plane displacement where the upper panels have moved relative to the lower panels over the column. The distress was typical on both north and south elevations of the building. Parapet stone connections were examined and minor corrosion was observed at the shelf angle and shelf angle anchor bolt, but there is no significant loss of section on the connections. However, the existing parapet stone connections differ from the original construction drawing details, particularly in the upper stones which may compromise the lateral capacity of the connection. In addition to the movement at the parapets, the stone column covers experienced visible out-of-plane displacements predominantly at the top panels and decreasing as they approach grade. This was typical on both north and south elevations of the building and at the building corners. Column cover connections were examined and determined to have inadequate lateral resistance based on the connection installed. Retrofit anchors (or original anchors) were not engaged at the column cover to effectively transfer the lateral loads. Cracking was observed at the parapet concrete column. Cracking was observed at the interface between the parapet wall panel and the concrete column. Joint material deterioration was observed at most stone areas on the building façade including the parapet stone and the column cover. Concrete cracking and spalling were observed at all parapet concrete beam joints. Also, previously applied membrane waterproofing repair material at the beam joint was cracked and debonded.

20 Page 20 Missing mortar was observed in the brick bed joints at the southwest building corner. RECOMMENDATIONS It is WDP s opinion that the observed problems at Gilmer Hall can be addressed through discrete repairs to re-align and re-anchor the panel systems. The repair would maintain the general appearance of the building and stabilize the existing stone, but would not be designed to significantly change the load path of the structural connections. A recommended conceptual scope of work is as follows: Temporary Protection Measures: The connections for the column covers are currently not considered to be structurally reliable. Although our inspection did not reveal any visibly unstable conditions, access to the areas directly below and adjacent to these column covers should be limited. In areas where access cannot be controlled such as at the building entrances, either temporary strapping of the covers or overhead protection should be designed until the final repair can be performed. Colum Cover Stabilization: Column cover connections should be repaired to provide the adequate lateral support necessary for the components to resist lateral loads such as wind and seismic forces. Displaced stone masonry units should be removed and the support shelf angles cleaned and field galvanized. Accommodation of the previous vertical displacement can be accomplished by saw cutting the top of the uppermost column cover to provide a movement joint between the panels. The parapet stones can then be reset to align with adjacent stone units. Lateral support using a modified lateral strap anchor should be installed when resetting the stone units. Stone And Concrete Material Repair: Stones damaged from the redistribution of forces should be repaired using either a limestone repair mortar or by utilizing a limestone Dutchman repair based on the severity of the damage. Cracking and spalling in the parapet concrete members including the precast concrete beam joints and the parapet concrete column should also be repaired to prevent future deterioration of the existing material. Further investigation of the materials may be required to find the cause and to determine the correct repair method for the distress.

21 Parapet Wall Waterproofing Repair: Page 21 Sealant replacement is recommended at parapet coping flashing to prevent additional water infiltration behind the stone units and onto the lateral ties. Parapet concrete beam joint waterproofing repair is also recommended to prevent moisture from seeping into concrete cold joints. Parapet Stone Anchorage Modification: Current existing parapet stone anchorage detail does not have a redundancy and its lateral strength solely depends on a 3/4 inch long bent leg of two strap anchors. Not only is the stress concentration a concern at the end of the strap anchor, but also minor cracking in the stone masonry can cause the condition of the stone masonry to be unstable. Thus, it is recommended that the parapet stone anchorage be modified to have adequate lateral strength and redundancy. We appreciate the opportunity to provide our continued service to the University. Should you have any additional questions regarding the information presented above, please contact our office at your convenience. Respectfully submitted, Whitlock Dalrymple Poston & Associates, P.C. BJ (Byoung-Jun Lee), Ph.D., P.E. Project Engineer J. Eric Peterson, P.E. Principal