Engineer completes courthouse survey

By Russell Hood

The Webster Progress-Times

 

The fire-damaged courthouse is structurally sound and repairable but more testing is needed to verify the load-carrying capacity of the second-floor structure, according to an engineer’s survey.

Structural engineer Mark Watson of Shannon prepared the “Fire Damage Structural Evaluation,” dated July 6, for the Webster County Board of Supervisors. Board President Pat Cummings distributed copies to fellow supervisors on July 15; no action was taken.

The board contracted with Watson to provide a structural evaluation of the courthouse, and with Belinda Stewart Architects to provide architectural cost estimates to determine the feasibility of restoration of the existing structure. Stewart was to present those estimates to supervisors Wednesday afternoon.

The purpose of the survey was to investigate structural concerns related to the Jan. 17 fire that caused significant damage to the 98-year-old building in Walthall. Watson conducted a visual structural evaluation with minimal destructive testing on the courthouse in late May and early June.

These are excerpts from Watson’s commentary, in which he discusses his findings, conclusions and recommendations:

Introduction

The predawn fire developed in the southwest corner of the building, which was the tax assessor’s office, and subsequently spread to the attic space. The fire gutted most of the second-floor level and all of the roof framing and attic. The wood roof framing and decking was destroyed and structural collapse of the large steel support trusses over the courtroom occurred. Significant damage to remaining roof support beams and columns followed along with varying degrees of fire, smoke and water damage throughout the interior and exterior.

The courthouse is a two-story structure that used an interior structural steel frame with reinforced concrete floor and load-bearing brick masonry walls constructed with cast-in-place, reinforced, concrete foundation walls.

Observations

Generally, the exterior walls, which had been faced with 2-inch thick clay tile block and cement plaster, were straight, plumb and free of structural damage. However, many sections of the brick extension above the stone frieze failed when the roof trusses, beams and rafters collapsed.

Moderate to severe diagonal cracks were found along the perimeter wall sections above the frieze. The perimeter roof cornice (an alteration to the original roof overhang) collapsed and burned, causing some spalling and impact damage.

Watson found no visible deformation or structural damage to the patented concrete floor system, nor any areas of structural failure in the first-floor rooms.

On the second floor, the roof beams and accompanying columns were severely deformed from the heat. Twisting of the structural steel border at the balcony overhang’s edge also occurred.

Conclusions

“Clearly, the courthouse sustained severe damages during the fire,” Watson concluded. “The roof structure was completely destroyed and its collapse further damaged the upper perimeter walls, above the stone frieze. Heat-related damages also impacted the structural steel beams and columns above the second floor, including the balcony overhang edge. Otherwise, the building structure performed quite well.

“There are certainly smoke, soot, and water damages to address along with the leftover

burned debris, the collapsed interior non-loadbearing walls, damages to wall, floor, ceiling finishes, the destruction of HVAC, electrical, plumbing, computer and communication systems, and the needed replacement of doors and windows throughout the building. The remaining structural components (loadbearing walls, reinforced concrete floors, structural steel floor beams and accompanying columns, and foundation) were not damaged and remain in sound condition. This would render the building repairable.

“Most of the structural rehabilitation would involve repairing the upper perimeter wall

extension (above the stone frieze), reconstructing a new roof framing system, reconstructing the balcony overhang edge, and various wall repairs to the locations with chimney flues built within.

“Great concerns have been expressed over the second-floor structure. The Kahn floor system presents no evidence of structural failure or even unacceptable deflection. Load testing of the floor system could be performed, if desired, to verify its existing load capacity.”

Recommendations

“Based on the degree of damage found to the outer brick walls, recommendations would

include reconstructing the upper walls from the stone frieze up to the roof-bearing point for the entire perimeter.” Watson stated.

“In lieu of restoring the original structural truss and steel roof beam system, it would be more beneficial to utilize light-gauge steel trusses spaced at closer intervals to avoid having such large concentrated loads. This even distribution of weight would be well served by the existing loadbearing walls. This could also eliminate the need for interior columns at the second-floor level.

“Presently, significant structural repairs to the second-floor system do not appear to be justified. Certainly, load testing as previously mentioned can be performed and would

probably be prudent to verify the actual load-carrying capacity. … Numerous interior non-loadbearing walls will need to be reconstructed. The elevator shaft is structurally unharmed and the only present repair needed is to correct the damaged corner edge.

“From a moisture-related perspective, considerable mitigation of saturated materials and accompanying mold/mildew growth is needed. … Prior to the commencement of substantial repairs, temporary bracing should be installed to properly secure the perimeter walls above the second floor. Presently the walls are unbraced and much more vulnerable to unwanted movement, even collapse, during strong wind forces.

“Once the upper framing has been restored, the walls will again be braced and retain their original lateral strength. Considerations of temporary bracing as a separate phase to protect the exterior walls prior to the commencement of even the renovation and repair plans would be prudent and is strongly recommended.”