East Elevation First United Methodist Church of Napa.
Owner 
Napa First Methodist Church
Location 
Napa, CA
Project Team 
Pullman
Specialty Contractor

Earthquake Damage Repair & Retrofit for Napa First United Methodist Church

Project Highlights 
  • Historic Restoration
  • Seismic Improvements and Building Façade Repairs
  • Concrete Restoration
Project Description 

Built in 1917, the First United Methodist Church (Napa FUMC), located in Napa, CA, is a large scale multistory historical structure, constructed primarily of conventional wood framing with six-inch thick reinforced concrete perimeter walls. It houses a 1,600 SF fellowship hall and offices along with a 2,500 SF sanctuary where as many as 400 people can congregate. The building is used for worship services, youth services and to provide support for the homeless in the area.

In August 2014, Napa FUMC sustained notable structural damage from a magnitude 6.0 South Napa earthquake. Portions of the exterior east wall separated from the roof by about three feet, resulting in the building being red-tagged. After immediate stabilization measures were taken, a detailed condition assessment was conducted by the PULLMAN design-build team for all accessible areas of the building to determine the extent of the earthquake damage and the building’s seismic risk level.

Technical Summary 

Repair strategy and execution

The PULLMAN design-build team formulated a phased approach to fast track repairs and seismic improvements while preserving the structure’s historical integrity. There were two kinds of repairs:

Structural Repairs

A series of winches and cables attached to one of the steel trusses was devised and installed in the east wall to gradually pull the wall back to the roof.

Following realignment of the east concrete wall, crews repaired cracks, voids, and spalling found beneath the exterior plaster coat on the wall. Expanded polystyrene pieces were fabricated to replicate the perimeter concrete and plaster segments that extend around the curved portions of the stained glass windows. Further, new roof-to-diaphragm connections were installed throughout the building at roof level.

The brick chimney that fell onto the roof was removed and hauled away. The remaining brick was cut off at the roof level, and tied back to the diaphragm. The damaged roof framing was repaired by sistering new roof joists to the existing framing and adding new framing where appropriate.

Repairs to the scissors trusses consisted of re-establishing connections to the vertical rods that had broken, and stabilizing the shifted members of the trusses. New positive anchorage measures at the supports of the trusses were installed, and the ceiling strong-back supports were replaced, enabling crews to eliminate some of the remaining residual deflection.

 

Seismic Repairs and Improvements

The selected approach to addressing seismic repairs and improvements was formulated with an emphasis on diaphragm strengthening and exterior wall support. The diaphragm strengthening approach included the roof, the ceiling level of the second floor of the building, and wall-to-diaphragm anchorage at the perimeter walls of the building. Further, the mezzanine level of the sanctuary was strengthened to create a functioning diaphragm to brace the tall gable walls for out-of-plane loads. At the ends of this diaphragm, collector elements were established or added to transfer the force into the concrete walls. The mezzanine and ceiling diaphragms are instrumental in effectively reducing the unbraced height of the exterior walls in the area of the steeply pitched gable roofs.

Additional seismic improvements included a number of new positive connections at post-to-beam and post-to-footing connections.

During construction, large cracks were observed at the high bell tower during the installation of the temporary scaffolding for concrete and plaster repair operations. A solution was developed that applied glass fiber reinforced polymer (FRP) systems to the concrete surfaces at the inner corner of the high bell tower to restore and enhance the overall strength of the tower walls. The FRP provided the necessary strength to accommodate computed shear demands without impacting the aesthetics of the tower.

The building remained operational during all phases of construction. Extensive shoring and scaffolding was needed on the exterior and interior of the building in order to perform repairs.The team worked within a limited construction site and put a high degree of emphasis on a site safety plan. Just fifteen months after the earthquake damaged the church, the project was successfully completed within the confines of a limited budget and with a fast-tracked schedule.