ENTRY FORM. DVASE 2015 Excellence in Structural Engineering Awards Program

Transcription

1 ENTRY FORM DVASE 2015 Excellence in Structural Engineering Awards Program PROJECT CATEGORY (check one): Buildings under $2M Buildings Over $100M Buildings $2M-$10M X Other Structures Under $5M Buildings $10M - $30M Other Structures Over $5M Buildings $30M - $100M Single Family Home Approximate construction cost of facility submitted: Entry Fee: Name of Project: Location of Project: Date construction was completed (M/Y): Structural Design Firm: Affiliation: Architect: General Contractor: $5 million FREE Nimitz Library - Foundation Repairs US Naval Academy - Annapolis, MD April 2015 W.J. Castle, P.E. & Associates, P.C. All entries must be submitted by DVASE member firms or members. NA Prime/Management: G-W Management Services, LLC Subcontractor: Hydro-Marine Construction, Inc. Company Logo (insert.jpg in box below) Important Notes: Please.pdf your completed entry form and to bkoroncai@barrpino.com. Please also separately 2-3 of the best.jpg images of your project, for the slide presentation at the May dinner and for the DVASE website. Include a brief (approx. 4 sentences) summary of the project for the DVASE Awards Presentation with this separate .

2 Provide a concise project description in the following box (one page maximum). Include the significant aspects of the project and their relationship to the judging criteria. Waterfront Facility - Structural Foundation Rehabilitation at US Naval Academy In 2013, W.J. Castle, P.E. & Associates, P.C. and Hydro Marine Construction Co., Inc. were contracted by G-W Management Services, LLC for the design-build foundation repair design of the Nimitz Library at the US Naval Academy in Annapolis, MD. The existing foundation consists of concrete framing on concrete pile caps with steel pipe piles. This coastal foundation is exposed to brackish tidal waters. Deficiencies included common tidal zone deterioration, such as spalling, cracking, delamination, chemical attack and discoloration of the caps. The work would require commercial divers, and the environment prevented the use of a conventional design approach. Castle presented the Navy with a complete structural re-design. Castle proposed a combination of FRP, and a steel grillage system installed below the existing caps, connected to the framing above with columns and the piles below with friction clamps. The grillage would work with the existing caps to support the full facility loads. Based on inspections, stiffness modeling, and testing results, the grillage was assumed to support 50% of load. This load sharing greatly reduced stresses in the existing cap, while still transferring the full load into the piles. Structural analysis modeling was performed to validate the load path concept using RISA. The design required out-of-the-box thinking in order to apply traditional engineering concepts to this unique and non-traditional design approach. Castle combined this engineering with proven underwater construction techniques to develop and constructible solution for the Navy. This design alternate offered several advantages: Weight. The steel grillage was estimated at approximately 1/10th the weight of the concrete. Durability. Both repairs would be submerged or exposed to wet-dry cycles. Historically, the existing concrete has deteriorated in this environment, while the bare steel piles exhibit minor deterioration only. Furthermore, all new steel would receive a protective coating to further increase the lifespan and minimize maintenance. Constructability. Despite being a simple concept, the concrete collar presented many construction challenges, including pumping over very long distances, and constructing formwork and placing rebar underwater with limited space and in complex configurations. Also, a support system similar to the grillage would have been required anyway to temporarily support the concrete. Alternatively, the grillage is easily transportable in pieces and allows for simpler field adjustments via field drilling and slotted holes. Castle designed only bolted connections, eliminating all underwater welding. Other work included: concrete spall and crack repairs of grade beam and slab, stormwater pipe replacement; and protection of existing structural members using pile jackets, epoxy coatings and specialty paints to reduce chemical exposure in the tidal zone. Castle designed FRP to increase the shear capacity of the grade beams at the new support point. During steel installation, Castle engineers identified additional deteriorated caps, and designed a full encasement with a FRP wrap. Because of our expertise in marine/coastal engineering, and underwater construction experience, Castle was able to meet and exceed the Navy's needs with an innovative structural design for a unique problem.

3 The following 5 pages (maximum) can be used to portray your project to the awards committee through photos, renderings, sketches, plans, etc Background Information Aerial View of the Nimitz Library The Nimitz Library was constructed in the early to mid 1970 s and is the main library for the U.S. Naval Academy. The building footprint is approximately 280 x280. Originally, these piles caps were formed on grade, which was later removed during a landfill stabilization project. As a result, the foundation is exposed to tidal waters (brackish) of College (Dorsey) Creek and the Severn River. During construction of an adjacent structure, severe deterioration of the exterior pile caps under Nimitz Library was noted. Castle performed a full underwater inspection with video in the summer of 2013 prior to design, as seen below. Above: Castle divers preparing for the underwater inspection All diver operations were completed to Navy requirements. Right: Diver with video system and inspection tools.

4 Concept Development The original repair concept was a massive concrete collar that would extend 1-6 around the entire cap, 2-6 below the cap and 2-0 above the cap, with concrete stub columns to frame into the grade beams above and shear tabs welded to the piles below for load transfer, as seen at left. Elevation of Original Repair Concrete Collar Castle brainstormed an alternative solution to address concerns of constructability and excessive dead load, while still meeting the needs of the client and working within the original Navy budget, schedule and construction constraints. We developed preliminary sketches of a steel grillage system supported by friction clamps, as seen below. Proposed Castle Redesign Steel Grillage with Friction Clamps Plan and Elevation Views

5 Structural Design Typical pile cap configurations analyzed were 6-pile rectangular caps and 3-pile triangular caps. Steel members were first sized based on the building loads determined using tributary areas based on the available drawings. Additional analysis was completed using RISA-3D design/analysis software to verify the load path concept by using a multi-material model of the foundation. The pile cap was analyzed using a modified Strut and Tie distribution model with notional loads, as seen on right top. The ground floor load was supported directly on the stub column and a portion of the upper floor load is redirected into the repair steel, reducing the load on the pile cap by 50%. RISA model showing 2-pile/2 column view and loads. The model results were used to size the proposed members for the required system stiffness to redirect the load into the steel, resulting in the larger members seen on right bottom. Castle also designed supplemental FRP to reinforce the grade beams at the new support columns, as seen on right bottom. Steel Grillage and FRP Installed at Cap J-11

6 Materials Part of the design goal was long-term capacity (70yr design life) with minimized maintenance costs. The assumed lifespan of the protective coatings and exposed steel were combined to achieve the design life goals. Castle worked closely with manufacturers using inspection findings, previous testing results, and design criteria to develop a complete repair system as shown above schematically and below installed. Low Tide View of Installed Grillage, Clamps, Jackets & Protective Paints

7 Construction Support Many existing configurations varied greatly from the as-built plans. As a result, many of the steel layouts needed to be modified to fit the actual geometries. Most of the existing structure was not plumb and the piles were typically underwater, making field measurements particularly challenging. Field Drilling Topside Diver Field drilling in place It was determined to use a combination of field drilling topside and in-place, seen above. Because of the variations, some steel configurations became increasingly complex, as seen below. Castle engineers worked closely with the dive construction team to develop the most constructible layouts. Low Tide View of Installed Grillage at a 3-Pile/Triangle Location

8