In the forward of the report, Andrew Lemer of TRB writes:
NCHRP Report 697: Design Guidelines for Increasing the Lateral Resistance of Highway- Bridge Pile Foundations by Improving Weak Soils presents design guidance for strengthening of soils to resist lateral forces on bridge pile foundations. Lateral loads may be produced by wave action, wind, seismic events, ship impact, or traffic. Strengthening of soil surrounding the upper portions of piles and pile groups—for example by compaction, replacement of native soil with granular material, or mixing of cement with soil—may be more cost-effective than driving additional piles and extending pile caps as ways to increase the bridge foundation’s capacity to resist lateral forces associated with these loads. This report presents computational methods for assessing soil-strengthening options using finite-element analysis of single piles and pile groups and a simplified approach employing commercially available software. The Additional resources and design guidelines will be helpful to designers responsible for bridge foundations likely to be exposed to significant lateral loads.
DBA has had the pleasure of working with T.Y. Lin and Slayden–Sundt JV in their effort to replace the Sellwood Bridge over the Willamette River in Multnomah County, Oregon, near Portland. Designed by Gustav Lindenthal, the existing Sellwood Bridge was constructed in 1925 to replace the Spokane Street Ferry, connecting the communities of Sellwood and West Portland. In response to budget issues at the time, the Sellwood Bridge design was scaled back to minimize costs. Fast forward to 2014 and the existing Sellwood Bridge is now the only four-span continuous truss highway bridge in Oregon and possibly the nation. The bridge is extremely narrow, two lanes, no shoulder or median, and one small 4-ft sidewalk. In addition to these shortcomings in design with respect to the modern age, the west end of the bridge was constructed on fill, and the hillside above the bridge is now slowly sliding toward the river. Ground movements have caused some of the girders to crack. Furthermore, the existing bridge was not designed to any seismic standards which present a major concern given the bridge’s location in the seismically active Pacific Northwest.
The new Sellwood Bridge will be a deck arch structure with three arches supporting the deck of the main river spans and is designed to the latest seismic standards. It will feature two 12-ft travel lanes, two-12 ft shared use sidewalks, and two 6.5-ft bike lane/emergency shoulders. Multnomah County is using the existing bridge truss on temporary pile foundations as a detour to save time and money during construction with minimal impact to traffic, people can always get quick loans without credit check process at any time if they have financial problems. According to www.cyclonebuildings.com, the original bridge truss was shifted on January 19, 2013. Complicating the move was the enormity of the bridge, an 1100-ft single truss weighing 3400 tons. In addition to the size and weight of the span, old age and its curved alignment added to the technical challenges. The impressive move took only 14 hours. The detour bridge is currently fully operational and will continue to carry traffic until the summer of 2015 when the new bridge is scheduled to open.
DBA played key roles in the design and construction of the main arch piers. As part of the VE Design, DBA assumed engineering responsibility for the 10-ft diameter drilled shafts supporting Piers 4, 5, and 6 (4 & 5 being in the river and 6 on the eastern shore). The lengths of these shafts ranged from 81 ft to 225 ft through a number of subsurface conditions which posed many challenges to construction. Subsurface conditions ranged from large loose cobbles/gravel (Catastrophic Flood Deposits) to cemented cobbles and gravel (Troutdale Formation), to very hard intact basalt bedrock. Due to the challenging geologic conditions and variability of these conditions across the site, DBA implemented an observational method in which the final shaft length determination was made on the basis of our on-site observations in relation to a set of predefined criteria. This approach provided the necessary flexibility to efficiently confront different subsurface conditions in a timely manner. Drilling subcontractor Malcolm Drilling successfully completed construction of the last of these shafts in mid-October 2013.
You can learn more about the bridge and the project at Multnomah County’s website, SellwoodBridge.org. The website has current field work updates, photo gallery, history of the project, and a live construction camera with daily, weekly, and monthly time-lapse videos. There is also a time-lapse of the moving of the old truss.
As reported by the Minneapolis Star Tribune, Case Foundation recently finished constructing 40 drilled shafts at the St Croix River Crossing Project. Since early June, Case has been working at a feverish pace to construct the drilled shaft foundations for the new extradosed bridge between Minnesota and Wisconsin. As of November 8th, all of the drilled shafts are officially complete. General contractor Kramer is working to finish the pier footings and support tower bases by early 2014. Soon, the joint venture of Lunda and Ames will begin construction of the $380 million bridge superstructure.
As MnDOT’s foundation consultant for the project, DBA has been on site during much of the foundation construction over the past five months. Some pictures taken during this time, along with several pictures from MnDOT are available for viewing on our Picasa Page. More pictures and information can be found on the project website and Facebook Page, and the project can be viewed live via webcam. Previous DBA blog posts about the main project and the predesign load test program can be found here.
DBA is pleased to wrap up its role on the St Croix Crossing Project with a very positive outlook. The drilled shaft construction proceeded on schedule and as planned without unexpected challenges, and our strong client relationships with MnDOT continued to grow stronger. It was also nice to see familar faces from Case, Braun Intertec, and Parsons Transportation Group, many of whom we worked with us at Hastings. We very much look forward to working with these partners again in the future!
As involved as we are in the deep foundations industry (and just returning from the DFI annual conference), it seemed appropriate to take time to highlight several upcoming events in the industry. All of these are great opportunities to get PDH credits, do some networking, and build relationships in the deep foundations industry. Most are cooperative efforts of one or more of the G-I, DFI, PDCA, and ADSC. All of them have a line-up of great speakers that are leaders in the industry. Click on the links below to learn more about each one.
The DICEP conference will present modern approaches to maximize Efficiency, Effectiveness and Economy (E3) of driven piles through a series of presentations including driven pile design, testing, evaluation and case studies. Steel sheet pile design and corrosion protection are also addressed.
The program will feature presentations by leading industry design engineers and civil engineering contractors on some problems encountered with drilled shaft foundations and how those problems were solved.
Cover Image of the Hastings Mississippi River Arch Bridge
The featured article in the July/August 2013 issue of Deep Foundations, the magazine of the Deep Foundations Institute, is coauthored by Dan, Paul, and Rich Lamb, P.E., of the Minnesota Department of Transportation (MnDOT). The article summarizes how load testing has been used successfully as part of the foundation design process by DBA and MnDOT on five major bridge projects along the Mississippi and St. Croix Rivers during the last 10 years and the lessons learned from these successive projects. The featured bridge projects include two major design-build projects, the emergency replacement of the I-35W St. Anthony Falls Bridge (2007) and the Hastings Mississippi River Arch Bridge (2011). The other traditional design-bid-build projects include the I-494 Wakota Mississippi River Bridge, the U.S. Hwy 52 Lafayette Mississippi River Bridge, and the St Croix River Bridge. As is often the case, each of these projects presented unique geological and hydrogeological challenges to foundation design – despite the projects all being within 30 miles of each other – including thick layers of highly organic compressible soils overlying bedrock, layers of cobbles and boulders, artesian groundwater conditions, and bedrock ranging from weak weathered sandstone to very hard dolostone. These varying conditions resulted in the use and testing of a variety of foundations. Load testing “with a purpose” has proven to be an integral part of the design and construction process on these projects, as the load tests were not simply for verification of a design but provided valuable information used to optimize the designs and provide quality assurance of the construction practices.
Please read the full article here or in a copy of Deep Foundations, a bi-monthly magazine published by the Deep Foundations Institute. DFI is an international technical association of firms and individuals involved in the deep foundations and related industry. More information about DFI and how to become a member can be found at www.dfi.org.
Also see our Projects Page for more about some of these projects and our other major projects.
NCHRP Synthesis 429 – Geotechnical Information Practices in Design-Build Projects is a report on the current practices of allocating and managing geotechnical risk through the use (or lack of!) geotechnical information in transportation project bid documents. Even though design-build as a delivery process for projects has been around for a while now, the allocation of risk due to subsurface conditions is an issue still treated with a variety of approaches.
Those of us who have been in this industry for a while know that a thorough geotechnical investigation reduces both cost risk and construction/schedule risk. Design-build is an effective method for accelerating project construction and delivery; however, the acceleration of the schedule puts more pressure on the geotechnical design since “geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award.”
Because geotechnical investigation and design is usually the first design package that must be completed and geotechnical uncertainty is usually high at the time of DB contract award, the design-builder’s geotechnical designers are under pressure to complete their work and enable foundation and other subsurface construction to commence. Successfully managing the geotechnical risk in a DB project is imperative to achieving the requisite level of quality in the finished product. The purpose of this synthesis is to benchmark the state of the practice regarding the use of geotechnical information in DB solicitation documents and contracts. The high level federal encouragement through EDC for state DOTs to accelerate project delivery by using DB elevates the need to manage geotechnical risk while expediting geotechnical design to a critical project success factor, and makes the results of this synthesis both timely and valuable.
As is the case with NCHRP synthesis reports, the authors conducted a literature review, conducted a survey of state DOTs and other agencies, and developed some conclusions that include effective practices for managing geotechnical risk.
The synthesis was based on a comprehensive literature review; a survey of U.S. DOTs, which received responses from 42 states (response rate = 84%); a content analysis of DB solicitation documents from 26 states; a content analysis of DB policy documents/guidelines from 12 state DOTs and 5 federal agencies; and interviews of 11 DB contractors whose markets encompass more than 30 states. The synthesis also furnishes three legal case studies (Colorado, Illinois, and Virginia) on cogent geotechnical issues and four geotechnical engineering case studies (Hawaii, Minnesota, Missouri, and Montana) that illustrate the methods transportation agencies use to deal with geotechnical issues on DB projects. Conclusions were drawn from the intersection of independent sources of information from the survey, case studies, and literature.
Some of the effective practices highlighted include the use of confidential Alternative Technical Concepts (ATC) during pre-bid, explicit differing site conditions (DSC) clauses that clearly quantify the design-build team’s risk and the threshold above which the DOT assumes the risk, the use of qualified personnel, and timely review schedules for geotechnical design items early in the project.
Our (DBA) experience in design-build has seen the range from effective practices to poor practices. This report provides a great summary of many of the effective practices we have found to be beneficial and that help reduce conflicts and delays. We can’t completely eliminate geotechnical risk, but it can be effectively and equitably managed.
Looking north towards Hastings as traffic travels on both bridges
Looking west from the Hastings’ river bank
I had the unique opportunity to be among the first people to cross the new Hastings bridge and among the last to cross the old Hastings bridge, during the short period of time when the two bridges were simultaneously carrying traffic.
Yesterday evening, Monday, June 3rd, crews shifted southbound traffic onto the new bridge for the first time. This evening, the old bridge will be closed to traffic for good as crews shift northbound traffic onto the new bridge. According to the Minneapolis Star Tribune, there will be a funeral service of sorts for the 1950’s era truss bridge tonight, complete with a bagpiper and hearse.
Being just up the road for the St. Croix Bridge Project, I took the opportunity to travel across both bridges today and take a few pictures like the ones above. It is not every day that we, as foundation designers, get a chance to see this stage of a project. Luckily, I was in the right place at the right time.
Earlier this week, officials from the Minnesota and Wisconsin departments of transportation (MnDOT and WisDOT) met for an official groundbreaking ceremony on the projected $629 million bridge and highway project that will connect Oak Park Heights, Minnesota, to St. Joseph, Wisconsin, just south of Stillwater, Minnesota, as highlighted in yesterday’s edition of The Minneapolis St. Paul Business Journal. The new bridge will replace the 80-year-old Stillwater Lift Bridge and relieve traffic congestion in nearby Stillwater.
DBA has been retained by MnDOT as the lead geotechnical consultant and foundation designer for the extradosed river bridge. Last summer, DBA aided MnDOT in the design and oversight of a load test program described in my blog post, “DBA Wraps Up Load Test Program and Proceeds with Design on St. Croix Bridge.” Following final design, which took place over the fall and winter, construction of the foundations will begin next week with the installation of a technique shaft. DBA will participate in construction as well, providing construction observation and review of the technique shaft and at least one shaft at each of the five production piers. Edward Kraemer & Sons, Inc. of Plain, Wisconsin, has been selected as the general contractor for the foundation contract with sub-contractor Case Foundation Company of Chicago, Illinois, performing the drilling. The extradosed bridge will feature five main river towers, each resting on two footings supported by a 4-shaft group of 8.5-foot drilled shafts, socketed 25-feet or more into sandstone bedrock.
I hope to have some more updates soon with some pictures following my upcoming site visits to observe the construction operations. In the mean time, you can stay updated by visiting the MnDOT project page and watching the “action” live via the construction webcam.
In the course of digging throughout the internet for data and information for a couple of projects using one of the best wifi routers, I came across some (relatively) recent research reports geared toward improving design of driven piles based on field testing. A report from The Illinois Center for Transportation at the University of Illinois at Urbana-Champaign is focused on improving pile design through increased resistance factors and nominal bearing values. A project by the Institute for Transportation at Iowa State University focuses on developing LRFD design procedures for steel piles in Iowa. It was published in two volumes, with Volume I covering the development of LRFD calibrations and a load test database, and Volume II covering field load tests performed for the project.
I have not had time to dig into them yet, so I just offer the links and abstracts to pique your curiosity. Perhaps you may find something interesting in them, or maybe something applicable to a project. There is a lot of research going on out there for TRB and NHI, so I figure sharing interesting tidbits helps get things circulated.
Click on the name of each of the research centers above to find out what other things they are doing, available reports, etc.
Dynamic pile testing and one static load test was performed in accordance with ICT project R27-69, “Improved Design for Driven Piles Based on a Pile Load Test Program in Illinois.” The objectives of this project are to (1) increase the maximum nominal required bearing that designers can specify to reduce the number and/or weight of piles, (2) decrease the difference between estimated and driven pile lengths to reduce cutoffs and splice lengths by development of local bias factors for predictive methods used in design, (3) increase reliance of pile setup to increase the factored resistance available to designers, (4) reduce the risk of pile driving damage during construction, and (5) increase the resistance factor (decrease in factor of safety) based on increased data and confidence from load tests in and near Illinois. Project deliverables can be categorized as (1) better prediction methods for stresses during driving, (2) better prediction methods for pile capacities using resistance factors for driven piling based on local calibrations that consider the effects of pile setups, and (3) collections of static and dynamic load test data focused on Illinois soils and geology.
For well over 100 years, the Working Stress Design (WSD) approach has been the traditional basis for geotechnical design with regard to settlements or failure conditions. However, considerable effort has been put forth over the past couple of decades in relation to the adoption of the Load and Resistance Factor Design (LRFD) approach into geotechnical design. With the goal of producing engineered designs with consistent levels of reliability, the Federal Highway Administration (FHWA) issued a policy memorandum on June 28, 2000, requiring all new bridges initiated after October 1, 2007, to be designed according to the LRFD approach. Likewise, regionally calibrated LRFD resistance factors were permitted by the American Association of State Highway and Transportation Officials (AASHTO) to improve the economy of bridge foundation elements. Thus, projects TR-573, TR-583 and TR-584 were undertaken by a research team at Iowa State University’s Bridge Engineering Center with the goal of developing resistance factors for pile design using available pile static load test data. To accomplish this goal, the available data were first analyzed for reliability and then placed in a newly designed relational database management system termed PIle LOad Tests (PILOT), to which this first volume of the final report for project TR-573 is dedicated. PILOT is an amalgamated, electronic source of information consisting of both static and dynamic data for pile load tests conducted in the State of Iowa. The database, which includes historical data on pile load tests dating back to 1966, is intended for use in the establishment of LRFD resistance factors for design and construction control of driven pile foundations in Iowa. Although a considerable amount of geotechnical and pile load test data is available in literature as well as in various State Department of Transportation files, PILOT is one of the first regional databases to be exclusively used in the development of LRFD resistance factors for the design and construction control of driven pile foundations. Currently providing an electronically organized assimilation of geotechnical and pile load test data for 274 piles of various types (e.g., steel H-shaped, timber, pipe, Monotube, and concrete), PILOT (http://srg.cce.iastate.edu/lrfd/) is on par with such familiar national databases used in the calibration of LRFD resistance factors for pile foundations as the FHWA’s Deep Foundation Load Test Database. By narrowing geographical boundaries while maintaining a high number of pile load tests, PILOT exemplifies a model for effective regional LRFD calibration procedures.
In response to the mandate on Load and Resistance Factor Design (LRFD) implementations by the Federal Highway Administration (FHWA) on all new bridge projects initiated after October 1, 2007, the Iowa Highway Research Board (IHRB) sponsored these research projects to develop regional LRFD recommendations. The LRFD development was performed using the Iowa Department of Transportation (DOT) Pile Load Test database (PILOT). To increase the data points for LRFD development, develop LRFD recommendations for dynamic methods, and validate the results of LRFD calibration, 10 full-scale field tests on the most commonly used steel H-piles (e.g., HP 10 x 42) were conducted throughout Iowa. Detailed in situ soil investigations were carried out, push-in pressure cells were installed, and laboratory soil tests were performed. Pile responses during driving, at the end of driving (EOD), and at re-strikes were monitored using the Pile Driving Analyzer (PDA), following with the CAse Pile Wave Analysis Program (CAPWAP) analysis. The hammer blow counts were recorded for Wave Equation Analysis Program (WEAP) and dynamic formulas. Static load tests (SLTs) were performed and the pile capacities were determined based on the Davisson’s criteria. The extensive experimental research studies generated important data for analytical and computational investigations. The SLT measured loaddisplacements were compared with the simulated results obtained using a model of the TZPILE program and using the modified borehole shear test method. Two analytical pile setup quantification methods, in terms of soil properties, were developed and validated. A new calibration procedure was developed to incorporate pile setup into LRFD
Note: Okay – I’ll admit – I also do a blog for the Geo-Institute Deep Foundations Committee. as such, there are often things that I feel should be posted at both – to get the widest possible audience! So, if you have already been over there, this post will look very familiar. It is much easier to reuse a post written by yourself. – Robert
As a continuing effort to implement the LRFD design methodology for deep foundations in Louisiana, this report will present the reliability-based analyses for the calibration of the resistance factor for LRFD design of axially loaded drilled shafts using Brown et al. method (2010 FHWA design method). Twenty-six drilled shaft tests collected from previous research (LTRC Final Report 449) and eight new drilled shaft tests were selected for statistical reliability analysis; the predictions of total, side, and tip resistance versus settlement behavior of drilled shafts were established from soil borings using both 1999 FHWA design method (O’Neill and Reese method) and 2010 FHWA design method (Brown et al. method). The measured drilled shaft axial nominal resistance was determined from either the Osterberg cell (O-cell) test or the conventional top-down static load test.