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Technical Papers

BergerABAM is devoted to exploring innovative solutions to real-world problems and pioneering research in engineering. Browse the broad selection of technical articles composed by our staff to examine interesting and unique ideas and applications. Please also reference our technical presentations for additional insight into pioneering methods and technologies. For information on any of our technical papers or presentations, please e-mail marketing [at]

  • Heavy Rail Below the 100-Year Flood Elevation - Innovations in Design - A Case Study (1.63 MB pdf) Proceedings of the 2015 Structure Congress, April 2015

    To decouple the heavy rail entrance into the Port of Vancouver USA from a major north/south mainline of the nation’s rail system, a rail-under-rail grade-separation structure was designed along the northern bank of the Columbia River in Vancouver, Washington.... To provide the required 23.5 foot (7.2 meter) clearance below an existing 100-year old rail bridge that crosses the river, the new rail line needed to descend more than 14 feet (4.3 meters) below the 100-year flood elevation. Because trains need to remain in operation during this flood condition, protection of the rail line from flood waters was required. Several innovative design solutions were developed to meet this design criteria in the most efficient manner. This case study is of regional, national and international interest. The paper will discuss the project’s constraints, design challenges, and solutions utilized to meet the project criteria. The location and configuration of the structure posed special challenges and the solutions for this project will be of interest to practicing structural engineers as well as rail operators, owners, and land use professionals. The rail structure itself, a 1,350-foot (411.5 meter) long portion of the new rail entrance for the port, is a partially elevated reinforced concrete structure that protects the rail from flood waters and supports it along the irregular river bank. To resist flood waters, a continuous reinforced concrete U-shaped trench was selected as the optimal solution. This selection of structure type was the first of many challenges for this project. The superstructure borrows design innovations from the continuously reinforced concrete pavement industry to help eliminate expansion joints over the entire length of the structure. This helps minimize water infiltration during flood events and reduces lifetime maintenance costs. The substructure consists of closely spaced driven steel batter piles that support the majority of the rail trench structure and is extremely compatible with the expansion joint-free design. The new rail trench structure provides a unique facility that meets the design challenges of the site, maximizes operational efficiency for the port, and relieves congestion at this critical location along the Pacific Northwest’s high-speed rail corridor. Full abstract »

  • Development of Large-Scale Precast, Prestressed Concrete Liquefied Natural Gas Storage Tanks (520.82 KB pdf) PCI Journal, Fall 2013

    Conventional technology for liquefied natural gas (LNG) tanks uses 9 percent nickel steel for the primary containment tank. This material is often in limited supply and is difficult to weld. Secondary containment tanks surrounding the primary tank are typically constructed using cast-in-place concrete.... The composite concrete cryogenic tank incorporates integrated biaxially prestressed concrete tank walls and is one of the first cryogenic tanks designed to the provisions of the American Concrete Institute’s <i>Code Requirements for Design and Construction of Concrete Structures for the Containment of Refrigerated Liquefied Gases</i>. This paper discusses the unique design and construction challenges encountered in the development of large-scale precast concrete cryogenic storage tanks, along with special considerations necessary when fabricating, handling, erecting, temporarily supporting, integrating, and posttensioning long and slender precast concrete wall elements. This concept takes advantage of the unique features of precast, prestressed concrete technology applied to a market currently held by cast-in-place concrete and welded steel. Full abstract »

  • Effect of Differential Creep and Shrinkage on Prestressed Composite Concrete Sections (638.1 KB pdf) 2013 PCI Annual Convention and National Bridge Conference, September 2013

    Differential creep and shrinkage in composite decks made of precast panels with cast-in-place topping concrete can yield to unacceptable cracking and adversely affect durability of a structure.... The common design procedure to include creep and shrinkage is to consider the differential strain between the time of construction and the life time of the structure as a single step analysis. The paper shows that this simplified assumption can significantly overestimate the stresses as it does not consider stress redistribution due to creep over time. This paper discusses time dependent viscoelastic procedures that consider stress redistribution over time, updating the creep behavior according to the stress state at each time step. The analysis has been performed on typical berthing pier decks following the definitions of the creep and shrinkage behavior per American Concrete Institute (ACI) 209R-92 and Model Code 90. It was found that the results between the two code approaches are also significantly different and that the change in the parameters, such as the age of precast elements and concrete curing time, significantly affect the stresses from differential creep and shrinkage. The paper suggests using such design approaches that are used in standard software with caution. Full abstract »

  • Composite Concrete Cryogenic Tank (C3T): A Precast Concrete Alternative for LNG Storage (2.74 MB pdf) The 17th International Conference & Exhibition on Liquefied Natural Gas, April 2013

    Traditional LNG storage tanks are built with significant amounts of 9 percent nickel steel and require extensive on-site welding of thick plating and a large construction area to assemble.... Conventional tanks of 160,000m3 capacity can take over 34 months to construct and cost $130 million or more, depending on a variety of factors including the location of the plant. In Regasification plants and Liquefaction plant additions/expansions, the tanks can be a critical path item for commissioning. The Composite Concrete Cryogenic Tank, C3T, is a modular design that replaces much of the 9 percent nickel steel with concrete, carbon steel, and wire wrapping, simplifying assembly, reducing material cost and speeding construction. It also introduces the ability to move a portion of the tank labor off-site. C3T was initially designed as part of a joint industry project (JIP), updating the design, construction, and application of concrete LNG tanks which were constructed without directly applicable design codes until the downturn in the LNG market in the 1980s. After the conclusion of the JIP, Chevron continued to develop the C3T concept. This work included evaluation using Chevron’s internal Technology Qualification Program (TQP), a constructability review, laboratory testing, and development of a construction demonstration plan. As a result of this work, Chevron is expected to receive endorsement from a third party accredited certification institution for Fitness for Service for C3T. This technical paper offers Chevron’s perspective on C3T, explain the benefits and risks of this technology, and provide an update on the progress made after the conclusion of the JIP and introduction of the new American Concrete Institute (ACI) code for design and construction of concrete structures for containment of refrigerated fluids, ACI-376. Comparisons will be made between C3T and the traditional 9 percent nickel steel LNG storage tanks. Full abstract »

  • Storm Water Management and the HOA Manager (52.74 KB pdf) Washington State Chapter Community Associations Institute, Community Associations Journal, April 2012

    The focus on storm water is becoming more important and the governmental enforcement is increasing. In fact, the EPA has identified “keeping contaminated storm water out of our nation’s waters” as their number one enforcement initiative for the Fiscal Year 2011-2013.... They are beginning to back up this enforcement need with inspections and even large fines for non-compliant sites. Third party environmental groups are beginning to take note, too, and file suits against private entities found to be polluting. You need to know how to take care of your storm drainage system and how to avoid contamination of the storm water on your sites. So how is this done? To do an adequate job, managers and community leaders should become familiar with three requirements of a storm drainage system: Post-Construction Maintenance, Good Housekeeping, and Pollution Prevention. Full abstract »

  • Manzanillo Container Terminal Redevelopment: Maximizing Throughput in a Limited Space (431.17 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    Increased container volumes make Manzanillo one of the fastest-growing ports on the west coast of Mexico.... In the 14 years since the concession for the dedicated container terminal was awarded as a single berth, annual traffic has grown from 50,000 to approximately 750,000 20-foot equivalent units (TEUs), the number of berths has grown to four, and the container yard has been expanded almost four-fold to its practical limit of 30 hectares (approximately 74 acres). Because the yard expansion followed a layout established when the original single-berth facility was constructed, it required reconfiguration to attain maximum efficiency in terms of TEU throughput per hectare of yard. This paper describes the planning, design, and construction involved in retrofitting and redeveloping the terminal. The terminal was redeveloped with a revised yard layout and retrofitted with new lighting, utilities, and a heavy-duty paving system to maximize density and allow the effective use of electrified rubber-tired gantry cranes. The yard is located in an area of high seismic hazard and the paper also discusses the ground improvement program that was implemented to mitigate the risk of earthquake-induced liquefaction. Finally, the paper discusses the retrofit of the existing container wharves to accommodate four post-Panamax container cranes. Two cranes were modified to match the existing rail gauge of 16.76 meters (55 feet), while two were left with the original 34.80-meter (115-foot) gauge and required construction of a third rail. The installation of the cranes required retrofitting the crane cable infrastructure and relocating cable slots from the backreach area to the opposite side of the waterside crane rail. Full abstract »

  • Seismic Retrofit of Piers Supported on Battered Piles Using Lead-Rubber Bearings (684.62 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    The use of battered piles in the design of new piers located in areas of seismic risk is discouraged based on the poor performance of battered piles observed in previous earthquakes. However, there are a significant number of existing piers with battered piles in service that may require seismic retrofitting.... Typical retrofit schemes involve driving additional plumb or batter piles that are integrated into the existing deck with new pile caps or other means but permitting restrictions, pile installation difficulties, and interruptions to facility operations may preclude this approach. In this paper, the use of lead-rubber bearings (LRB) is proposed as an alternative seismic retrofit concept for batter pile-supported piers. The paper summarizes the basic principles of base isolation and presents a case study of an example pier retrofitted using two concepts, one with new driven piles and the other with LRBs mounted on new subcaps supported by the existing battered piles. The seismic performance of the example pier and the two retrofitted structures was evaluated using displacement-based analysis method. Budget cost estimates developed for both retrofit concepts indicate that the LRB retrofit may be more economical than the driven pile concept for the configurations studied. Full abstract »

  • Proposed Seismic Detailing Criteria for Piers and Wharves (507.09 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    A new ASCE standard, Seismic Design of Pile Supported Piers and Wharves, is being developed by the Coasts, Oceans, Ports, and Rivers Institute.... The standard will use displacement-based methods and build on the provisions of similar standards such as the Marine Oil Terminal Engineering and Maintenance Standards, the Port of Long Beach Wharf Design Criteria, and the Port of Los Angeles Container Terminal Seismic Code. As part of the development of the proposed standard, a significant effort was expended reviewing test data for a wide variety of deck systems and pileto- deck connections commonly used throughout North America. A common finding of the tests is that the rotation at the pile-to-deck connection is concentrated at a large crack at the interface between the pile and the deck rather than over a short length of the pile at the top of the pile, which is the expected behavior for reinforced concrete in flexure. This paper focuses on the detailing of pile-to-deck connections and summarizes the available test data for the connections that are considered in the proposed standard, along with permitted strategies for reducing earthquake damage at pile-to-deck connections. Full abstract »

  • Analysis of Seawall Concepts Using Yielding Soil Anchors (862.7 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    Stretching 8,016 feet (2,443 meters) along downtown Seattle’s waterfront, the 75-year-old Alaskan Way Seawall provides the interface between the city’s downtown core and Elliott Bay.... Damage to the seawall during the 2001 Nisqually earthquake led to investigations that confirmed the seawall is deteriorating and seismically vulnerable to potential liquefaction of the loose soils that underlie the structure. The City of Seattle is planning to replace the seawall. To further advance the proposed replacement program, two replacement concepts were developed. One used secant pile technology while the other used yielding soil anchors in combination with soil cement (jet grouting). A soil-structure interaction program was used successfully to model the complex dynamic interaction between the soil, the existing seawall and timber relieving platform, and the structures proposed to replace the seawall. The structural and geotechnical engineers collaborated on the development of an innovative hybrid system in which the soil improvement or secant pile wall resists service loads and liquefied soil pressures while the yielding soil anchors resist the inertial effects of a seismic event. This paper will review the development of the replacement alternatives analysis, the lessons learned, and the importance of successful structural-geotechnical collaboration in order to provide a solution to a complex soil-structure interaction problem. Full abstract »

  • Hybrid Design/Build Approach for Quaywall 729 (858.64 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    To support aircraft carrier maintenance at Puget Sound Naval Shipyard & Intermediate Maintenance Facility, the U.S. Navy retained BergerABAM to develop a request for proposal (RFP) for the replacement of Pier B and the retrofit of Quaywall 729.... Due to a confined design and construction schedule for the design/build (D/B) team, the substructure design of Quaywall 729 was performed by BergerABAM and incorporated into the RFP document as a prescriptive design. This paper highlights the benefits and challenges associated with the combination of D/B with prescriptive requirements (design/bid/build) from the development of the RFP package through final design and construction by the D/B team. Full abstract »

  • Development of the SP-SSA International Terminal, Vietnam (667.4 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    Located on the Cai Mep River in southern Vietnam near Vung Tau, approximately 85 kilometers (53 miles) from Ho Chi Minh City and 25 kilometers (15.5 miles) from the South China Sea, the new SP-SSA International Terminal (SSIT) will be able to handle 1.5 million 20-foot equivalent units at buildout.... In 2006, Vietnam was the fastest-growing economy in Southeast Asia at 7.8 percent for the year, and SSIT is being developed to ensure that Vietnam’s port infrastructure is adequate to sustain this growth. Master planning and bringing this modern container terminal online presented great challenges. The terminal’s 60-hectare (148-acre) site was an intertidal salt marsh covered with date palm, and geotechnical testing showed that the upper 45 meters (150 feet) of soils were poorly consolidated clays and would require substantial ground improvement. The first stage of construction reclaimed the site with approximately 3.5 million cubic meters (4.6 million cubic yards) of sand and 6.6 million meters (4,100 miles) of wick drains. Dredging and slope revetment constituted the second stage of construction. The project also constructed the marine works, consisting of a pile-supported quay capable of supporting multiple tandem-lift super post-Panamax ship-to-shore gantry cranes and a pile-supported barge quay dedicated to supporting the barge traffic that prevails in Vietnam. The final stage of construction involves paving, utilities, and miscellaneous support buildings. Based on its current progress, the project will be complete and the terminal will be operational by January 2012. This paper describes the background, planning, design, and construction challenges involved in creating and implementing a master plan for a modern container terminal over a soft-soiled environment. Full abstract »

  • Design and Construction of Cruise Berth for Colon 2000, Panama (375.83 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    Colón 2000 operates a one-berth cruise facility on the Caribbean coast of Panama. In late 2007, the owner decided to build another berth and terminal dedicated to serving Royal Caribbean Cruise Lines. The owner selected Intercoastal Marine Inc. (IMI) to furnish the berth within a year on a design/build basis.... IMI selected BergerABAM to provide pre-award engineering, construction documents, and construction support services for the berthing structure, which was planned as a marginal wharf and mooring dolphins. The main elements of the project included a 200-meter-long (656 feet) by 20-meterwide (66 feet) marginal wharf, two 160-tonne breasting line dolphins, and two 120- tonne mooring line dolphins. After initial study, using a sheet pile bulkhead concept was eliminated due to weak soils above the bearing Gatun stratum, high cost, and schedule risk. An open pile-supported wharf concept that overcame the cost and schedule risks was selected instead, to be built over an engineered underdeck slope. The wharf option was made more viable by installing stone columns under the wharf footprint to improve the weak soils and increase the slope stability for both static and dynamic conditions. The wharf structural system consists of precast concrete piles supporting a platform made of precast concrete transverse cap beams, precast concrete deck panels, and cast-in-place topping. This system, which resulted in a very durable structure, used locally produced components and expedited construction to complete wharf design and construction in only 10 months and allow IMI to meet the tight December 2008 deadline for berthing the first vessel. Construction challenges included stone column installation using a top-feeding system, close interaction with dredging activities, and slope dredging in presence of coral. The Colón 2000 terminal became the first homeport for Freedom-class cruise vessels in the southern Caribbean that sail from Colón to other Caribbean destinations. Latin American tourists no longer need to begin their cruise at a U.S. port which requires obtaining a U.S. visa. The new berth supplements the existing terminal and allows more than double the vessel calls during the short cruise season. Full abstract »

  • Seismic Analysis and Design of Berth 14 Extension, Balboa, Panama (432.88 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    Berth 14 is located near the Pacific end of the Panama Canal and is part of a marginal wharf system built by the U.S. Army Corps of Engineers in the early 1900s.... It consists of a hybrid concrete-steel superstructure supported on large and brittle concrete shafts of up to 2.4 meters (7.9 feet) in diameter. This paper describes the challenges encountered in the construction of a finger pier extension 85 meters (279 feet) long by 50 meters (164 feet) wide to Berth 14. The extension was designed for repairable damage under a contingency level earthquake and minor damage and disruption to operations under an operating level earthquake. A flexible structural system consisting of 700-millimeter (28-inch) octagonal precast, prestressed concrete plumb piles was chosen as the most practical and cost efficient solution to construct the extension. Careful detailing of a full force-transfer mechanism from the new structure into existing Berth 14 was required as part of the design. Potentially imposing large inertial forces on the drilled shafts of the existing berth—an initial concern—was proved to be irrelevant through analytical modeling of the connected new and existing structures. The paper addresses the analytical tools and techniques employed to evaluate possible substructure alternatives as well as the seismic assessment of the existing Berth 14. Full abstract »

  • Design of Container Yard at Port of Balboa (1.49 MB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    Committed to converting the Port of Balboa into a major transshipment hub, Panama Ports Company (PPC) launched in 2006 a $300-million expansion program to increase berthing and stacking space that would almost triple the port capacity.... The site’s history of marine-related activities, deteriorating facilities, buried structures, and poor soils mandated significant investment in clearing and preparation. Of the 25-hectare container yard to be built, about 15 hectares were dredged to remove poor soils and reclaimed by filling/compacting with imported sand. Ground conditions in a 5-hectare area were also improved by a wick drain and surcharge program. Most container yards in North America are built with continuous asphalt or jointed portland cement concrete (JPCC) pavement. However, the Balboa yard features a discrete paving system for container stacking that is suited for rubber-tire gantry (RTG) crane operations. It consists of narrow reinforced concrete (RC) beams (serving as container bases) with a thin asphalt sealed crushed rock base around them. Support for the RTGs consists of continuous jointed RC strip footings, with JPCC pavement provided at yard tractor lanes and other roads for circulation of reach stackers and empty container handlers. In addition to providing savings relative to the continuous PCC solution, this discrete system eliminates container stacking on sloped planes, which is undesirable for very high stacking. This paper describes the design and construction processes associated with site improvement and the pavement system. Traffic demand on truck and passing lanes was evaluated based on estimated throughput including the effects of container type, size, block size and dwell time. The design followed the 1993 AASHTO Guidelines. Load equivalency factors were used to account for non-linearity of axle load effects from different yard equipment. Finite element modeling was used to determine shortterm load demands on pavement elements to account for complex loading conditions. Full abstract »

  • Installation of RMG Cranes at Intermodal Rail Yard (823.74 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    This paper presents the requirements, analysis, and items to be considered during design and installation of rail-mounted gantry (RMG) cranes at an intermodal rail yard or IMY.... Installing RMGs at intermodal rail yards has been considered for various locations; indeed, some are under construction and others are in operation at locations in the United States. RMG cranes increase throughput in an intermodal rail yard, allow densification of the yard, and represent a huge reduction in diesel emissions associated with the yard. The new generation of RMGs is typically electrically powered, resulting in a 100 percent reduction in diesel emissions from container handling equipment and greatly reducing noise pollution. RMGs can transfer containers directly between train and truck, thus eliminating the need for diesel-powered container handling equipment in the yard. RMGs are installed on foundations with a continuous crane rail supported by a continuous or noncontinuous foundation. Key elements in the structural and civil design of an intermodal rail yard are the layout of the yard and terminal entrance for efficiency; other considerations include the loading and stripping tracks, truck travel paths, the amount of ground storage, and the electrical supply. Full abstract »

  • Development and Qualification of a Floating Pier for the U.S. Navy Fleet (539.47 KB pdf) American Society of Civil Engineers' Ports 2010 Conference, April 2010

    The U.S. Naval Facilities Command plans to deploy a floating modular hybrid pier (MHP) to berth most major Navy ship classes.... Developed to replace deteriorating pile-supported piers, the MHP is made up of floating modules that can be assembled into any length of pier, and later disassembled and relocated separately or as a unit in another home port. This paper summarizes the development, testing, and evaluation of the MHP. The paper discusses the features of the pier that allow its reconfiguring for specific applications and introduces the most likely configurations for particular vessel support goals and mooring requirements. The paper also summarizes some of the key analyses performed to mitigate technical and functional risks. Full abstract »

  • Masonry Infill Walls: An Effective Alternative for Seismic Strengthening of Low-Rise Reinforced Concrete Building Structures (426.94 KB pdf) 14th World Conference on Earthquake Engineering, October 2008

    Masonry infill walls are widely used as partitions worldwide. Field evidence has shown that continuous infill masonry walls can help reduce the vulnerability of a reinforced concrete structure.... In order to test this hypothesis, a full-scale three-story flat-plate structure was strengthened with infill brick walls and tested under displacement reversals. The results of this test were compared with results from a previous experiment in which the same building was tested without infill walls. In the initial test, the structure experienced a punching shear failure at a slab-column connection. The addition of infill walls helped to prevent slab collapse and increased the stiffness and strength of the structure. The measured drift capacity of the repaired structure was 1.5%. A numerical model of the test structure was calibrated to match experimental results. Numerical simulations of the response of the strengthened structure to several scaled ground motion records suggest that the measured drift capacity would not be reached during strong ground motion. Full abstract »

  • Lateral Load Analysis of Waterfront Structures Supported on Plumb Piles (276.84 KB pdf) 14th World Conference on Earthquake Engineering, October 2008

    Analysis of wharves/piers under lateral loads is often conducted by assuming the piles to be fully restrained at a presumed distance below the mudline.... Once a reasonable point of fixity for each pile is estimated, the wharf/pier is modeled as a one-story structure comprising a slab supported by columns of different heights that are fully restrained at their bases. Strictly, this simplified approach is valid only if the response of both the soil and the piles are linear because the location of the point of fixity varies as the pile and/or the supporting soil softens with increase in lateral displacements. However, representing the flexibility of the supporting soil by assuming the piles to be restrained at invariable points of fixity may produce plausible results in relation to elaborate analysis methods. In this paper, case study of a marginal wharf structure supported on plumb piles is presented. The lateral resistance of the wharf computed from static lateral load (pushover) analysis was compared with the demand estimated using low to moderate seismic design spectra. It was demonstrated that, for the earthquake demands considered, modeling the soil-pile support by using points of fixity instead of a coupled nonlinear system leads to overestimation of the lateral displacement demand by only 20 percent. Full abstract »

  • Indirect Flexural Crack Control of Concrete Beams and One-Way Slabs Reinforced with FRP Bars (89.12 KB pdf) 8th International Symposium on Fiber-Reinforced Polymers for Reinforced Concrete Structures, July 2007

    This paper presents the fundamentals of an indirect flexural crack control procedure for the serviceability design of concrete beams and one-way slabs reinforced with FRP bars.... Rather than calculating crack widths, the proposed procedure follows the format of the flexural crack control model for structural concrete design recommended by ACI 318M-05 [1] in which cracks are controlled by specifying a maximum permissible reinforcing bar spacing. The objective of proposing a flexural crack control procedure in terms of maximum bar spacing rather than a crack width calculation and comparison with allowable limits is to avoid all the impracticalities associated with direct crack width measurements. The proposed procedure does not represent a significant departure from the current flexural crack control model for FRP-reinforced concrete structures reported in ACI 440.1R-06 [2]. Instead, the proposed approach is seen as a rearrangement of the flexural crack control rules of [2]. One additional advantage of the proposed crack control equation is that it can be used for both FRP- and steel-reinforced concrete design. The proposed procedure explicitly accounts for the dominant effects that bar cover and FRP reinforcement stress level, stiffness and bond properties have on flexural cracking. Full abstract »

  • Current FRP-Reinforced Concrete Design Trends in ACI 440.1R (191.36 KB pdf) 8th International Symposium on Fiber-Reinforced Polymers for Reinforced Concrete Structures, July 2007

    For the first time since its inception in 2001, the 2006 edition of ACI 440.1 R [1] for the design of structural concrete members reinforced with FRP bars has been published as a "conventional" technology document instead of an "emerging" technology guideline.... This category upgrading reflects the successful application of FRP reinforcing bars as concrete reinforcement in a wide variety of projects worldwide together with the rising consensus among researchers and design engineers that current FRP-reinforced concrete design theories and recommendations have also reached an acceptable level of maturity. The upgrading of [1] comes accompanied by the introduction of design recommendations for shear design, indirect deflection control and flexural crack control of concrete beams and one-way slabs reinforced with FRP bars, together with the addition of punching shear design provisions for two-way slabs with FRP bars. The indirect deflection control and punching shear design provisions were previously unavailable in earlier ACI 440.1 R versions. The most important feature of the newly adopted or improved design procedures is in the fact that they are mechanistic and general in nature. This feature represents a significant drifting from precursor ACI 440.1 R design procedures which were usually based on traditional steel-reinforced concrete design recommendations modified and empirically-tuned through modification factors. The main advantage of having incorporated mechanistic design procedures in ACI 440.1 R-06 lies in the fact that most of these design procedures can be applied equally well to FRP- or steel-reinforced concrete structures. This design philosophy trend not only provides designers with more transparent design methodologies but also paves the way for a potential unification of FRP- and steel-reinforced concrete design procedures in the future. This paper describes in detail the latest changes that were adopted in ACI 440.1 R-06. The information is divided into two categories: refined design procedures and new design procedures. The paper also describes those design aspects that are currently undergoing discussion at task group level to attempt replacing existing first generation design procedures with more robust design ru les for the next revision of ACI 440.1 R. The paper also identifies areas where additional research is needed. The main motivation behind the latter is to plan ahead and facilitate the job of professional designers when faced with the task of designing concrete structures or members in which the use of FRP reinforcing bars is not currently addressed by ACI 440.1 R-06. Full abstract »

  • The Efficiency of the Motion Amplification Device with Viscous Damper (621.15 KB pdf) Eighth Annual Conference for Earthquake Engineering, April 2006

    The motion amplification device with a viscous damper has been recognized as an effective solution to mitigate wind or seismic excitation especially for stiff-type structural systems. These devices are designed to amplify a small interstory drift to amplify the stroke of dampers attached.... The efficiency of such devices with dampers relies not only on geometric configurations but is highly dependent on the stiffness of support elements. In this paper, a "scissor-jack" type of motion amplification device, a "toggle brace damper" system, is investigated. A procedure for determining the relationship between the motion amplification factors with geometry of the toggle brace mechanism, which includes the elongation of the braces is proposed. It is demonstrated that the amplification factor is not merely a function of toggle brace configuration; it also depends on the brace stiffness, including toggle brace elongation. Accordingly, a mathematic model in the complex modulus of the toggle brace damper system is established and results are presented. The analysis results indicate that the efficiency of the toggle brace damper system significantly depends on support toggle brace stiffness, and this is an important design consideration. Full abstract »

  • Seismic Design of a Ferry Transfer Span Based on Two Performance Levels (610.68 KB pdf) Eighth Annual Conference for Earthquake Engineering, April 2006

    Washington State Ferries (WSF) has recently initiated a new hydraulic lift transfer span (H-span) system to replace an existing counterweighted cable and winch system. The motivation for this change stems in part from failure of a pulley cable, resulting in the transfer span and its operator falling into the water, at a WSF ferry terminal.... The new H-span consists of multiple steel boxes with an orthotropic steel deck and provides adequate stiffness and strength to safely support live load if one of the two cylinders fails. The H-span is simply supported by bridge seats on the shore side and by two hydraulic cylinders on the offshore side. In the horizontal direction, the H-span reacts like a cantilever beam fixed at the shore side by the two bridge seats. The bridge seats are rigidly linked to the concrete trestle span supported on numerous piles. From the dynamic response spectra analysis, it was found that the response of the H-span along the transverse direction is substantially magnified due to a "whipping" effect triggered by the massive trestle structure. The resonant amplification was more than five times that of the AASHTO design spectra. To limit the structural response, the H-span was designed to meet two seismic performance levels. The bridge shall perform linear-elastically up to a defined Operational Earthquake (50 percent of design earthquake) before a fuse-mechanism reduces the fixity of the shore side of the bridge, allowing the bridge to slide at the bridge seat and sway horizontally offshore to contact a bumper system. This paper discusses the design considerations for the two performance levels and the consequential detailing of fuse and bumper systems. The dynamic impact on the bumper system is also discussed. Full abstract »

  • Displacement-Based Seismic Design of a Large Naval Pier (754.69 KB pdf) PCI National Bridge Conference, October 2005

    This paper discusses the displacement-based seismic design of the newest naval pier at Naval Station Bremerton in Bremerton, Washington. It is 45.72 meters wide by 399.3 meters long and is capable of simultaneously berthing two aircraft carriers.... Displacement-based design is the state-of-the-art in seismic design and its basic premise is to determine what displacement will occur during the design earthquake and detail the structure to accommodate its displacement. This is a significant change from most current codes, which are force based. The project enjoyed a 50 percent reduction in piling by using the displacement-based when compared to the force-based method. Soil-structure interaction, push-over analysis, material overstrengths, and site-specific response spectra are used to determine the displacement response of the pier under Levels 1 and 2 earthquakes, the “displacement demand.” A push-over analysis is then performed to the displacement demand and the expected capacity of individual members and connections are evaluated and compared to the displacement demand on each member and connection. Full abstract »

  • New Technologies Proven in Precast Concrete Modular Floating Pier for U.S. Navy (1.5 MB pdf) PCI Journal, July/August 2005

    Representing a breakthrough in naval vessel berthing infrastructure, a test bed structure for a large-scale modular hybrid floating pier was designed with state-of-the-art precast/prestressed concrete technology and a number of material and design innovations.... In 2004, the $5 million 15.2 × 30.5 × 8.8 m (50 × 100 × 29 ft) test structure was fabricated, erected, and open-ocean towed to its final destination in San Diego, California, as proof of concept for a future $45 million, 400 m (1300 ft) long double-deck floating pier for the U.S. Navy. The Modular Hybrid Pier was conceived as a replacement for obsolete and deteriorating naval berthing facilities. Designed for 100 years of repair-free service, the pier will provide a high level of support services to a variety of vessel classes and facilitate a rapid upgrade of vessel utilities with the advance of fleet support system technologies. More than 25 government, university, and private entities collaborated to develop this groundbreaking concept in precast concrete pier infrastructure. Full abstract »

  • Analysis and Design for End Effects in Twisted Double Tees (1.01 MB pdf) PCI Journal, May/June 2005

    Prestressed concrete double tees are sometimes set on non-parallel supports to facilitate drainage; this practice induces twisting in the members. If the twist angle is large enough, cracks may occur in the flanges adjacent to the web-flange junction.... This paper identifies the important modes of deformation and presents an analysis of the stresses and deformations caused by twisting. Local distortions of the cross section near the member ends are shown to play a pivotal role in bending and cracking of the flanges of double tees. A new theory of torsion that includes those deformations is developed, and a parametric study is carried out to show the effect of variations in the dimensions of the member. Finally, based on the new theory, the paper presents several graphs that facilitate the computation of the twist angle that causes cracking in a double tee of common dimensions. Full abstract »

  • Slack Rope Analysis for Moving Crane System (302.29 KB pdf) 13th World Conference on Earthquake Engineering, August 2004

    The reliability and security of rope design for moving crane are very important especially for the nuclear plant in high seismic zones. The conventional linear analysis indicates that a slack rope occurs very likely for severe earthquake load excitation. In other words, the rope will overcome its lifted weight and will go into compression.... The nonlinear time history method according to NOG-4154 shall be applied for slack rope design. In order to perform nonlinear time history analysis subject to earthquake excitation, the tension-only nonlinear properties of element shall be taken into account. The designated program – GTStrudl or other nonlinear – program may have such a capability for solving nonlinear dynamic systems. However, the result shows that the current tension-only nonlinear finite element in GTStrudl has the reasonable accurate results with comparing theoretical results for damped single degree-of-freedom (SDOF), but it fails to converge for a large-scale DOF of computer model for trolley-bridge system due to severe nonlinearity of rope. Simplified analysis shall be employed in rope slack nonlinear study. Because only vertical mass of lifted weight is included, the rope forces caused by horizontal earthquake load in high modes are very small and can be neglected. According to this dynamic characteristic, we simplify and use two-degree-of-freedom (2DOF) structural systems to represent a multi-DOF of bridge-trolley with lifted load system in vertical direction. The results show that this simplification proved to be very accurate and successful. This paper presents a very simple 2DOF nonlinear dynamic model and compares rope forces between linear dynamic analysis and nonlinear slack rope analysis. The results also show that rope force could be much larger than those from conventional linear dynamical analysis varied with rope length. The proposed slip-slack model shows that the brake slip device can limit rope force, predicts the displacement for prescribed design level, and prevents rope failure due to slack rope impact. Full abstract »

  • Seismic Evaluation of 32 Industrial Buildings by Screening Process and Analysis (74.22 KB pdf) 13th World Conference on Earthquake Engineering, August 2004

    Thirty-two buildings from the Puget Sound Naval Shipyard (PSNS), Washington, USA, were seismically evaluated by the two-tiered evaluation recommended by the U.S. Federal Emergency Management Agency (FEMA).... The buildings, many of them large industrial shops and offices, were built between 1897 and 1980 and represent a variety of building types with the largest category being steel moment frame structure. This paper presents the typical seismic deficiencies found during the evaluation and discusses the upgrade strategies and the affiliated costs in relationship to building age, size, type, and historic classification. The paper discusses the benefits and drawbacks of the seismic evaluation of large facilities, such as for PSNS. The paper concludes that the seismic evaluation succeeds in identifying and quantifying the structural upgrade needs of the buildings to full code performance levels, but does not address alternative solutions that consider partial upgrades or less severe performance goals to optimize upgrade works for the available funding. It also concludes that, for owners of large facilities, the seismic evaluation alone does not offer a satisfactory basis for establishing upgrade priorities and implementation strategies without developing upgrade concept studies with affiliated cost estimates. The study found that the building age and structural type are the most influential parameters on upgrade costs. Whether a building within the same age group is listed as historic or not, seems not to influence the upgrade costs. Similarly, a larger building seems not less expensive to upgrade on a square foot price basis than a smaller building. Full abstract »

  • Precast Framing System Provides Innovative Solution to Modernization of Shipbuilding Facility (1.04 MB pdf) PCI Journal, May/June 2003

    An historic world-class shipyard, Bath Iron Works — a subsidiary of General Dynamics and a major builder of complex, technologically advanced naval vessels — required a significant facility modernization and shipway expansion to meet contract production deadlines.... A value-engineered precast concrete redesign replaced the original cast-in-place plan for the pile-supported open wharf platform. An extensive precast concrete framing system provided the most efficient and durable solution to construct this large overwater shipbuilding platform in the harsh conditions of coastal Maine. Innovative detailing and a flexible precast redesign were key to meeting the owner’s accelerated schedule for critical shipbuilding capabilities. Moreover, the precast system enabled the contractor to overcome daunting site conditions, including a high mean water level, cold weather, tidal cycles and currents, strong winds, and the variable geotechnical substrate for this fast-track project. Full abstract »

  • Recommended LRFD Guidelines for the Seismic Design of Highway Bridges (505.77 KB pdf) National Seismic Conference and Workshop on Bridges and Highways, May 2002

    This paper provides an overview of the proposed seismic design provisions that have been developed to replace those currently in use throughout the United States.... The proposed provisions include two-level design procedures, advanced analytical tools such as push-over, updated ground motion data, new site characterizations, simplified methods for lower seismicity regions, and more comprehensive liquefaction provisions. Many of the developments that have followed in the wake of recent earthquakes have been incorporated into the proposed provisions. The effort has been conducted and overseen by broad-based and nationally recognized teams. The proposed provisions are now being used in trial designs around the country and will be considered for adoption in Guide Specification form next year by AASHTO. Full abstract »

  • Automated People-Mover Station Integration (240.01 KB pdf) 8th International Conference on Automated People Movers, July 2001

    An automated people-mover (APM) derives its worth from the urban activities it serves. Therefore, the number, placement, and configuration of stations have profound impacts on the value derived. This paper explores issues that surround APM station design. It presents information on a sample of existing installations.... It describes experience with and without platform walls and doors and discusses fire protection issues. It provides a framework to facilitate the integration of stations and guideways into nontransit buildings. Full abstract »

  • World's Largest Prestressed LPG Vessel (2.25 MB pdf) PCI Journal, January/February 1977

    The world’s largest precast prestressed concrete floating liquefied petroleum gas (LPG) facility is described. Criteria for design and construction of the 375,000-barrel floating facility are given. Construction procedures and prestressing methodology are discussed.... Problems related to the development and marketing of prestressed concrete for marine construction, and prospects for future applications of prestressed concrete sea structures are presented. Full abstract »