The $16.5 million expansion and renovation of the Long Beach High School is underway and Stalco Construction is assigned to work on the concrete portion of the project. The existing structure has not received any significant updates or renovations since the early 1970s. The project includes construction of a new, three-story, 20,000-square-foot addition to the main building, renovation of the existing three-story structure, demolition of a separate building, and construction of new outdoor sports facilities. “The construction crews face numerous logistical challenges related to the location of the site and work taking place in and near an occupied school,” says Stalco President Alan Nahmias.
Challenges included developing a structural design that would provide the necessary lateral force resistance at the new building’s grade level that’s very open and features limited exterior walls. “The team also had to address a poor soil condition at the addition’s site,” says Christopher A. Lesher, senior associate at Ryan-Biggs Associates, structural engineer for the project. “We provided the lateral strength by designing 12-inch shear walls and two columns on the ground level. The higher floors feature bearing CMU walls and four concrete beams on each floor.”
Due to the low bearing soil, the addition’s foundation system incorporates 128 auger cast piles. The design calls for piles to be topped with reinforced concrete caps, which vary in size. Concrete grade beams will then span the caps, with the bearing shear walls and concrete columns resting atop the beams. The depth of new caps matches the depth of caps below the existing high school building. The structural system also includes precast concrete plank floors and precast concrete plank roof structure as well as concrete columns and concrete beams. The masonry walls on the second and third floors will be constructed of CMUs. The project is scheduled for completion in 2014.
In the initial phase of the project, Stalco is undertaking the ground-up construction of the new addition, including the auger piles. The construction process for the piles calls for grout corks to be installed at the bottom of each auger-drilled, 60-foot-deep hole. Corks are attached to the augers prior to the beginning of the drilling of each hole. Once the auger reaches the desired depth, a #10 rebar is inserted through the auger’s central tube in order to disconnect the cork from the auger and provide reinforcement for the entire pile. Following installation of the corks and central rebars, the crews pump in a 5000 psi compressive strength grout mix to create 12-inch diameter piles. With the grout in place, the crews drop rebar cages 30 feet deep into the piles, installing them around the central rebars. The rebar cages will later provide lateral force resistance on the grade level by ensuring rigid connections between the addition’s structure and the piles below. The cages, fabricated onsite, consist of four vertical #4 rebars and approximately 40 horizontal perimeter stirrups spaced at eight-inch intervals throughout the entire length of the cage.
In the following phase, Stalco will replace the deteriorated three-foot-wide concrete outriggers with sunshade panels installed on the south and east sides of the existing high school. The renovations will involve cutting 14 inches off the existing outriggers, repairing the remaining concrete, and anchoring new steel supports in the repaired concrete outriggers. New, clear anodized aluminum shade panels will rest on the steel supports. The color and look of the sunshade aluminum will match the color of the new window frames for architectural consistency. The sunshades, custom manufactured by Atoms Architectural Products, will feature extruded aluminum, airfoil-shaped blades with bullnose fascias. In total, Stalco will install in excess of 1400 linear feet of new sunshades.
The two buildings will be connected through expansion joints on the second, third, and roof levels. Concrete sunshade outriggers on the west side of the existing building, adjacent to the addition, will be removed prior to the construction of the new structure. The crews will install new steel framing anchored in the concrete wall of the original building’s second and third floors. The framing will support new concrete slabs, protruding out by two feet and eight inches. The concrete protrusions will allow seamless internal connections between the two buildings.
In addition to Stalco and CS Arch, the project team includes construction manager Savin Engineers, P.C.; structural engineer Ryan-Biggs Associates, PC; MEP (mechanical, electrical, plumbing) engineer Lewis Engineering, P.C., civil engineer The Chazen Companies; and athletic facilities consultant HMH Site & Sports Design.