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By Tracy Brettmann

The Highway 146 Bridge Expansion Project across the Clear Creek Channel in Houston, Texas was designed on driven precast concrete piles. However, during construction, the piles along one side of the bridge along the main channel encountered obstructions and couldn’t be installed. These obstructions turned out to be the remnants of a previous bridge foundation at this location, which was unknown to the designers since that bridge had been demolished 40 years ago. Those old foundations were massive 20 ft by 40 ft (6 m by 12 m) pile caps 11 ft (3.3 m) thick supported on precast concrete piles 37 to 55 ft (11 to 17 m) long. The foundation re-design for these locations involved installing a single 78 inch (2 m) diameter drilled shaft up to 125 ft (38 m) long to replace the originally planned driven pile supported pile cap. The drilled shafts would need to be installed within very tight tolerances since they were supporting a single bridge column directly above it. In addition to drilling through the obstructions, this work would need to be completed from barges in 30 ft (9 m) of water capable of dealing with both the current and tides affecting this area. The shafts were installed using a multi-step process. The first step involved coring a larger diameter 100 inch (2.5 m) hole through the reinforced concrete pile cap and removing the concrete inside. This was followed by the installation of a 72 ft (22 m) long permanent casing to and removing the soil and existing precast piles inside. Finally, the drilled shaft excavations were advanced to the completion depths (uncased) using bentonite slurry as the support fluid.

May 1, 2022

By Marwa Nabil, Alaa A. Ata

"Recent developments in the analysis of piled rafts has incorporated the load sharing of the raft and the piles to support the superstructure. In the piled-raft system, piles are cast monolithically with the raft and the load is partly transmitted by the raft to the soil directly below it, and partly by the piles to more competent deep soil. While these piles are effective in increasing the bearing capacity and reducing the settlements, they often lead to significant straining actions at the pile head-raft connection which may constitute the weakest link. An attempt to provide a more economical solution, that at the same time overcomes this weak link, is to disconnect the pile heads from the raft and introduce an intermediate cushion of compacted fill. In this case, the piles are considered as reinforcement to the subsoil and will also act as settlement reducers. This paper investigates the load transfers mechanism of the unconnected piled raft with cushion using ABAQUS finite elements Program. The main objective is to provide an in depth analysis of the raft–soil–pile interactions in multi-layered soil under static and seismic loads. The investigated system provides an economical alternative for traditional connected piled raft foundation, where there is no need to reinforce the piles, no need for pile head demolition or expensive waterproofing of the pile head connection. Cost analyses of unconnected versus connected piled raft systems confirmed a cost savings in the construction that may reach from 50 to 70 percent.INTRODUCTIONDesigners around the world have gained more confidence to use the piled-raft as a more realistic system where the raft and the piles share transferring the superstructure loads to shallow and deep soil layers. A further advancement is to use unconnected piled rafts as another practical and economical alternative to the traditional piled rafts. Unconnected piled raft is also synonymous to settlement reducing piles; or simply, soil improvement piles. Liang et al. (2003) has extended the concept of pile-raft-foundation to a new type of foundation called composite piled raft foundation or unconnected piled raft foundation. The foundation is composed of a sand/gravel cushion sandwiched between the raft and piles. The piles group may contain short and long piles. The short piles are constructed of flexible materials such as soil-cement columns or sand-gravel columns, and are used mainly to improve the bearing capacity of shallow soft soil; the long piles, which are made of relatively rigid materials such as concrete, and their main function is to reduce settlements. The cushion plays an important role in mobilizing the bearing capacity of the subsoil and in modifying the load transfer mechanism of the piles. In Shanghai, China, this system of unconnected piled raft has proved to be quite suitable and effective in coastal areas, where deep soft soil deposits exist."

Jan 1, 2016

By Salim Mezazigh

Usually different methods for designing a single pile submitted to a lateral loading are available. They are based on theory of elasticity with the parameters E,v or subgrade reaction method using the p-y curves. The subgrade reaction methods are commonly used. They allow determining the efforts exerted along the piles and their corresponding displacements. Before any design the reaction curves P-y must be well defined for each foundation soil layer. These curves link the pile horizontal displacement y to the subgrade reaction of soil P. Different in situ tests such as the static penetrometer or the pressuremeter give a possibility to get the P-y curves in the case of a single pile installed in sand with an horizontal surface and statically laterally loaded. These ideal conditions are not always respected on the site around the pile if appear slopes, embankments, or buildings... The behaviour of such configurations of piles is more sophisticated due to the proximity ( slope, embankment, earthworks, buildings,..). A research program has been conducted to determine the influence of a slope on the P-y curves by centrifuge modelling. The centrifuge tests constitutes an experimental approach allowing parametric studies in respect with similitude laws in geotechnique. Before all, repeatable tests have demonstrated that the test conditions, the instrumentation equipment and the installation method for piles are well controlled. By this way, the obtained results from centrifuge tests can be transferred to the prototype i.e. the in situ piles. Many tests have been performed on piles in sand to determine the influence of a pile on the p-y curves. The main objective is to give for practice some coefficients to apply to p-y single pile curve to take into account the proximity slope effect. Here the experimental set up is described and in particular the proximity slope effect is discussed. Deduced subgrade reaction reduction factors are proposed for piles in sand under lateral loading.

Jan 1, 2002

By D. Vanni

Constructing new infrastructure in urban areas increasingly entails the use of sophisticated techniques for soil improvement in order to minimize surface disturbances in adjacent areas and damage to existing structures. In Naples, at the new Piazza Garibaldi subway station, TREVI built a 45 m deep shaft using a hydromill, and utilized soil freezing for the excavation of the four station's tunnels, fifty meter long, located approximately 30 meters below the water table. An innovative use of directional drilling was specially developed by TREVI to successfully complete this challenging job.

Jan 1, 2006

By Alan Alhadeff

Why is mediation being hailed as the wave of the future? The high cost of putting on a trial, over-crowded court calendars and long trial delays have resulted in what prominent attorneys and leading jurists are calling a litigation crisis. In no segment of the legal world are these pressures greater felt than in the trial of the serious construction case. Furthermore, the siege mentality of both the plaintiff and defense bar often leads to a reluctance by either side to make the first reasonable offer for fear of showing weakness. Attorneys operating in the serious construction case arena express concerns that there exist insufficient opportunities for the parties to meet, tell their stories, and negotiate settlement prior to the eve of trial. Mediation, by opening lines of effective communication and encouraging meaningful settlement negotiation, has proven to be a very effective antidote to the litigation crisis.

Jan 1, 1990

By Graeme Smart, Thomas Fiala

"Yorkville Plaza II, a 40-storey signature condominium residence, is scheduled to open on Avenue Road in Toronto’s prestigious Bloor-Yorkville neighbourhood in spring 2017. In close proximity to Toronto’s subway system, the new tower requires six levels of underground parking, founded in wet, silty sand.Isherwood Geostructural Engineers (Isherwood) was retained in April 2012 by developer Camrost-Felcorp to provide a shoring and excavation solution to address the challenging site conditions. A 31-storey upscale residential building under renovation with three levels of parking, owned by Camrost-Felcorp, flanks the site on the north. Situated on the eastern border is a 7-storey building with three levels of parking. Avenue Road, a four-lane arterial road that brings heavy commuter traffic into downtown Toronto, runs along the western border, and on the southern border of the site is a busy City road that brings traffic into the popular Yorkville area. The tunnel for the Toronto Transit Commission’s (TTC) overburdened east-west subway is located 14.5 m to the south, running below an existing 26-storey neighbouring building. Electrical and communication utilities (Bell) are closely located along the southern side. Non-documented existing excavation shoring, installed in the early 1970s, on the southern and western sides compounded the difficulties presented by the TTC tunnel.This paper presents the unique, non-conventional hybrid shoring solutions Isherwood developed to address the challenges presented by the site, as well as other complications that surfaced during the project: non-encroachment requirements (no tiebacks) beneath uncooperative neighbours, tight geometry to install shoring, and Toronto’s two coldest winters in decades.THE PROJECTBecause of circumstances associated with this site, for this project Isherwood designed two unique shoring walls which drew on their experience and expertise they had gained over the last 40 years. The following is the story of this site:Yorkville is an affluent neighbourhood in the heart of Toronto with a vibrant mix of high-rise towers, residential homes, tony restaurants and flagship shops. The development requires six levels of underground parking (a 20m deep excavation), with three levels undermining the high-rise buildings to the north and east and extending into wet, silty sand.Isherwood was retained in the spring of 2012 to design the excavation shoring. Isherwood’s scope also included field support, design, verification and monitoring. Finite Element Analysis was employed to confirm Isherwood’s design and anticipated movement of the south shoring wall and the TTC subway tunnel.The existing site was severed in two, with the proposed condominium tower slated for the southern portion. On the north half of the site stands a 31-storey building (Yorkville Plaza I at 21 Avenue Road), with three levels of underground parking, sitting on belled caissons which were one foot from the back of the proposed shoring wall so this would have to be considered in relation to the design and drilling methods. Constructed in the early 1970s, Yorkville Plaza I is currently being converted from the Four Seasons hotel to luxury condominiums by Camrost-Felcorp. To the east, directly adjacent to the proposed shoring, stands a 7-storey building (164 Cumberland Road) with three levels of parking, supported on spread footings founded on stiff clayey silt. The tunnel for the TTC’s busy east-west subway, a double box structure built by cut-and-cover in the 1960s, is located 14.5 m to the south, 9 m below grade, and running below an existing 26-storey building. Bell fibre optic communication cables and electrical lines, along with storm and sanitary sewers, are situated on the south and west sides of the site, leaving limited room to install shoring. Due to the heavy volume of commuter traffic on the four-lane arterial road (Avenue Road) to the west, site access and lane closure were not permitted here."

Jan 1, 2015

By Gerry Houlahan

The east span of the 3.5 km long SF-Oakland Bay Bridge is supported by different types of foundations along its span. Starting from the west, its first 460 m section comprising twin concrete box-girders is supported by sands and rock on Yerba Buena Island. A 620 m long steel suspension span then bridges a 25 m deep channel that is formed in sediments overlying rock. Twin concrete box girder structures, each 2.4 km long, complete the stretch over the remainder of San Francisco Bay to the engineered earth fill landing at its east end. For most of its length, the Skyway bridges water 3 to 10 m deep over soft surficial Young Bay Mud. The foundation types include spread footings with hold-downs, steel and concrete piles that are set in drilled rock sockets up to 3 m in diameter and 2.5 m diameter steel tubular piles driven to penetrations of up to 100 m. The design and construction-related considerations are presented. The different foundation types, influences of the site geology and earthquake demands on the substructures are discussed. The seismic motions of the bridge superstructures and substructures, as well as the depth-varying soil motions, influenced the foundation design. Together with performance-based design criteria, including post-earthquake footing displacement limits, these seismic demands influenced various aspects of the foundation design, including the use of battered and vertical piles.

Jan 1, 2013

By Chandrasegaran, Tamilmani

"This paper describes a case study of a retaining wall structure using a diaphragm wall to construct a stilling basin at Tanjung Bin T4 power plant in Johor Bahru, Malaysia. The stilling basin is part of the Phase IV (T4) 1x1000MW power plant’s offshore cooling water discharge culverts. The site is located close to the sea with 5m of fill on top of very soft sediments of marine origin up to 20m thick underlain by fluvial clay and metasedimentary rock. Stringent wall deflection criteria and construction program dictated adopting an efficient solution with 800mm thick diaphragm wall supported by permanent top support as the temporary prop and improved horizontal restraint provided by deep mix piles acting as a slab (ground improvement layer) below the final excavation level. The depth of excavation is about 10.12m from the existing ground level. The proposed solution kept the wall deflection below the limit of 0.7% of the depth of bulk excavation and avoided additional props leading to faster completion of the structure. With unsymmetrical loading behind the retaining walls, 2D finite element analysis was carried out to assess the wall deflection and stresses in the wall and the grout layer below. The diaphragm wall is instrumented to monitor the behavior and the findings are discussed in the paper.INTRODUCTIONConstruction in soft marine clay has always been a challenge to the engineer because of its very low shear strength and its sensitivity to disturbance. In the case of excavation projects the problem becomes even more complicated with development of excess pore pressure during excavation. Marine clay with its low shear strength and lesser passive resistance, generally leads to large wall movements and settlement behind the wall. Increased passive resistance coming from increased number of props is useful but has its limits and it is no longer the most effective way in containing or reducing the wall movements or forces in the wall. One of the solutions to these problems is to improve the soil shear strength by means of ground improvement infront of the wall at an elevation most appropriate to maximize wall performance. There are several methods adopted in improving a soil layer including mixing additives to the ground to improve the shear strength to partially replacing the weak soil while others are fully replacing the weak soil. This paper discusses the case study of approximately 10m of excavation in soft marine clay using 800mm thick diaphragm wall supported by Deep Mix Piles (DMP) being used to improve soft marine deposit to form a slab just below the formation level and thus improving passive resistance significantly. The ground improvement layer helped to reduce the wall forces and deflections making it possible to remove the need for additional temporary props leading to significant savings is time and productivity. The paper presents the various options explored before this method is adopted, the design approach, instrumentation data and the monitored results."

Jan 1, 2015

By Y. Z. Wang

Zhengzhou Yellow River Highway Bridge, which is under construction, has a total length of 5550 meters with bored cast-in-place concrete piles as the foundations of its piers which have a diameter of 2.20 m with a length of approximately 65 m. This paper attempts, through the introduction of the said bridge's footing pile design and construction, mainly to give an account of the following points: 1) experiment and research on deep friction pile with a large diameter, 2) calculation of vertical carrying capacity of the pile with a large diameter, 3) analy­sis of horizontal forces the footing-piles of the column-shaped piers, 4) application of normal and reverse-circulation rotary drilling technologies to the construction of bored cast-in-place concrete piles with a large diameter and 5) applying super-sonic impulse on destruction detective device to examine the quality of the pile concrete.

Jan 1, 2010

By Takeshi Maki, Kh. Adeel Tariq

"The lateral resistance of the structure plays an important role during seismic event and it can be increased by using ground improvement. In this study an attempt has been made to investigate the effect of cement-treated sand on the lateral capacity of the pile. The behavior of piles surrounded by sand only and cement-treated sand confined in a steel box (30 x 30 x 50 cm) which is subjected to lateral cyclic load has been investigated. Piles having a diameter of 2.5 cm and embedded to a depth of 45 cm were used. Steel and aluminum piles were used to investigate the effect of flexural stiffness on the lateral capacity of the pile. Bottom supports of piles were also changed from pinned to fix. Well graded sand compacted to 70% of relative density (RD) was used. Cement-treated sand having a compressive strength of 3.7 MPa was used. Displacement controled lateral load tests were performed and cyclic loads were applied until pile displacement was 4%, 10%, 20%, 35%, 50%, 75% and 100% of pile diameter. Results evaluated are compared with common method of analysis like Brinch hansen (1961), Brom (1964), Poluos (1980) etc. Results have indicated that the stiffness of a pile affects its lateral capacity. The introduction of central cement-treated sand part increased 5 times the lateral capacity of piles as compared with a sand only condition.IntroductionPiles are used extensively around the world to support loads of structures. Piles are commonly used to carry axial load, but in some structures, the lateral capacity of the pile is more important than the axial capacity: for example piles supporting earth retaining structures, electric tower foundation, etc. Structures can be subjected to both axial and lateral forces, like structures constructed at harbor that are subjected to lateral force due to waves action; and structures built in earthquake prone areas like Japan."

Jan 1, 2017

By Bastian Hoffmann, Christian Moormann

The paper presents results of an experimental study on the axial load bearing behavior of vibratory driven full displacement piles in comparison with impact driven and cyclic quasi-static installed piles in dense sand. The test setup and the measurement devices used to this end are explained. Subsequently, the results of the axial loading like load settlement curves are shown and the impact of the installation method is interpreted. The results presented in this work are mainly based on three installation methods: test series one investigates axial behavior of vibratory driven piles, test series two describe the same cyclic pile installation process but without dynamic influence wherein a special test setup developed to install the piles cyclic quasi-static in the soil was used. A third test series carried out using the conventional impact pile driving method served the purpose of not only comparing the results against vibratory driving, but also aided in isolating the effects of dynamics inherent to the vibratory driving process.

May 1, 2022

By Tai Luu, Maxim C. Schisler, Yaser Taheri

The Stevens Gateway Project is an expansion of the Stevens Institute campus overlooking the Hudson River in Hoboken, NJ. The plans call for 90,000 ft2 (8360 m2) of new classroom, research, and student life facilities in new, 4-story buildings. The excavations for the building footprints were bounded by city streets and existing buildings, including the historic Carnegie Laboratory of Engineering, built in 1902. Pit underpinning was originally specified for the Carnegie building. However, given the depth of cut, construction time required for the 13 ft (4.9 m) deep pits would be substantial. The geotechnical contractor retained for the support of excavation work therefore offered an innovative active soil nail wall design that would meet project requirements in a shorter timeframe. Unlike the passive soil nail systems common in the industry that are chiefly used for soil slope stabilization, active soil nail walls contain pre-stressed anchor components to resist soil movement and limit settlement of soil and structures being contained. In addition to a discussion of the overall design approach of the active soil nail wall system, this paper will include a detailed description of its constructability and effectiveness. This project’s use of a conventional slope stabilization technique for an unconventional purpose may have positive implications going forward. INTRODUCTION Stevens Institute of Technology is a private university in Hoboken, New Jersey that sits on the cliffs of the City of Hoboken overlooking the Hudson River and Manhattan Island to the east of the campus. In recent years, the university has executed numerous plans to expand and upgrade its campus academic, student life, and residential facilities. One such project is the Academic Gateway Complex. The plan adds 90,000 ft2 (8360 m2) of new classroom, research, and residential facilities while also enhancing community connections by building a park to serve as a green corridor for the city. The proposed construction took place on the north and south side of 6th Street between Hudson Street and River Street. The project included the demolition of an existing university building followed by the construction of two, 4-story buildings on the north and south property lots. The north and south buildings will be connected by a second floor bridge spanning 6th Street. The buildings each contain a full basement extending from the proposed ground floor at approximately El. 41ft (12.5 m) to the basement subgrade at El. 26 ft (7.9 m). Each building will be constructed on respective mat foundations. Figure 1 presents an overview of the project area.

Jan 1, 2019

By Juhyung Lee

Recently, large diameter drilled shafts are often used for foundations of large-scale marine bridges with high capacity and required to resist lateral loads. Steel casings are essential in supporting the hole-diving concrete installation of the drill shafts constructed in the sea. The casings, however, are usually not considered as the structural elements and their load bearing capacity is often overlooked in the design of drilled shafts. As the diameter of drilled shafts becomes larger, there are higher demands for more efficient and economical design of large-scaled drill shafts in the sea. Steel-concrete composite columns are popular for the superstructure of bridges, and the outer steel attached to the shaft increases the shaft resistance through confining the concrete. In this study, the lateral resistance of steel-concrete composite drilled shafts was evaluated quantitatively based on the numerical analysis. When steel casings are used as structural elements such as the composite columns. Ultimate lateral bearing capacity of composite drilled shafts with various diameters was numerically calculated through the 3D finite element analysis. For that, elasto-plastic model with the perfect plasticity is involved to capture the ultimate load. A commercial FEA program, MIDAS-GTS, is used in this study. Real field conditions of the west coast, Korea were examined to set up the ground conditions and pile lengths required for this parametric studies. Detailed characteristics of the stress and displacement distributions are evaluated for the better understanding on the mechanisms of the composite shaft behavior.

Jan 1, 2008

By R. Paul De Bruyn

A. Crane Check List -- Make -- Model -- Year of Manufacture -- Where is load chart? Is it for this crane? -- Boom style and length -- Boom tip drawing (sketch) for fixed lead connection. Has the crane manufacturer been consulted on the point of attachment? -- How many drums; diameter and length of wire rope. -- Is the single part line pull enough to lift pile or hammer on single part line? -- What is the effective weight of the whole driving system - leads, pile, hammer, etc? -- Are there any auxilliary hydraulic systems? Are the line pulls on these adequate to lift the pile or hammer? -- What is the anticipated working radius? Will the spotter collapse to that length? -- Nature of foundation under crane - barge, marsh, unstable sand, etc. -- Does the crane meet OSAH and state regulations -current certification. Note - the operator is responsible for compliance with regulations. -- Is there any extra weight added to counterweight by compressors or hydraulic systems? What does crane manufacturer say? Consult factory before adding.

Jan 1, 1990

By S. R. Nandargikar

Construction of open foundations for the Second Thane Creek Bridge was indeed a challenging task. Some major problems were encountered during the construction of foundations for pier No. P22 (S/N), P.6(S) and P.12(S) of this bridge. This paper describes these problems briefly and also highlights how they were solved.

Jan 1, 1996

By H. R. Masoumi

This paper presents a numerical model for the prediction of free field vibrations due to vibratory and impact driving. As the focus is on the response in the far field, where deformations are relatively small, a linear elastic constitutive behavior is assumed for the soil. The free field vibrations are calculated by means of a coupled FE-BE model using a subdomain formulation, proposed by Aubry and Clouteau (1992). The model is validated by means of the results of Kaynia and Kausel (1991) for the impedance of a single pile. First, the case of vibratory pile driving is considered, where the contributions of different types of waves are investigated for several penetration depths. The results show that in the near field, the response of the soil is dominated by a vertically polarized shear wave, whereas in the far field, Rayleigh waves dominate the ground vibration and body waves have been importantly attenuated. Second, the case of impact pile driving is considered. A linear wave equation model is used to estimate the impact force during the driving process. Furthermore, it is investigated how the soil stratification influences the ground vibration considering the case of a soft layer on a stiffer half space. The results show that when the penetration depth is smaller than the layer thickness, the layered medium has a small influence. However, when the penetration depth is larger than the layer thickness, these effects become more significant. Finally, the computed ground vibrations are compared with experimental data reported in the literature.

Jan 1, 2006

By Wang Huichang

A tentative mathod for predicting load-settlement relationship and bearing capacity of single piles based directly on the results measured by cone penetrometer with local friction sleeve is presented. It is possible that the load-settlement curves can be constructed by means of CPT and the problem of both the bearing capacity and the settlement behaviour of single piles can be considered jointly. The proposed load-transfer functions are continuous, positive monotonic and nonlinear. a concept of weight mean point resistance 2D above and 4D underneath the pile base to determine the unit ultimate base resistance of piles is presented. The predicted results of seven jacked piles in loess are in good agreement with the load test data.

Jan 1, 1991

By Ernest Naesgaard

Post-grouted micro-piles were used for the seismic upgrading of the Vancouver International Airport Domestic Terminal Building (DTB). The micro-piles provided vertical resistance to both uplift and compression loads to supplement the existing timber pile foundations ability to resist the earthquake induced forces, and to provide foundation support at locations where the installation of traditional driven piles was difficult. This paper describes the site conditions, design rationale, installation method and quality control testing procedures. Site and Subsurface Conditions Vancouver International Airport is located within the central portion of Sea Island, Richmond, British Columbia (Fig. 1). Sea Island is bordered by branches of the Fraser River on the northeast and south sides and the Strait of Georgia along the west side. The natural grade of the island is part of a large delta that has been built up over several thousand years. The general pattern of sediment deposition has followed the direction of the Fraser River flow from east to west, and has built up soft sediments of about 200 m thickness at Sea Island (Luternauer, et al. 1993, Mathews and Shepard 1962). The original grade in 1962 prior to the existing Airport Terminal Building development was at about geodetic elevation 1.1 m with a grass and topsoil cover.

Jan 1, 2004

By Wolfgang G. Brunner

In the far north of Uttar Pradesh Province in the Indian Himalayas, the 280 MW Dhauliganga hydroelectric power plant is under construction by National Hydroelectric Power Corporation (NHPC), a state- owned enterprise, and a joint venture of Kajima Corporation of Tokyo and Daewoo Corporation of Seoul. This project sets out to develop the lower section of the mountain cascade of the Dhauliganga River, a tributary of the Sarda River, with a 311 m gross head. The 1360 km2 mountainous catchment area is bounded in the north- east by the Chinese border and in the south- east by the Nepalese border. The dam project is located in a remote area north of the principal town of Darchula of the upper Sarda valley, which is one of the seismically most active regions of India. The 56 m high rock fill dam, which will be the first of its kind in India, is faced with concrete and has a 1 m thick, at its crown 270 m long and over 70 m deep cut- off wall of plastic concrete below its toe. The cut- off wall, with a total area of 7500 m2, is constructed by a combination of Bauer hydraulic grabs, assisted by chisels and a Bauer BC 40 cutter which enables the overlapping joint system to be installed, guarantees optimum verticality and enables the cut- off to be keyed into the bedrock formation.

Jan 1, 2004

By Leonardo Massone

The p-y method is one of the most popular methods in pile design and has been calibrated for various boundary conditions using numerical and experimental studies during recent years. Most studies on reinforced concrete (RC) piles have included the impact of flexural nonlinearity, (e.g. nonlinear moment?curvature relations) but not considered associated pile shear deformations when deriving p-y curves from field data. Common p-y curves may be better applicable for piles with flexure dominated failures (e.g. piles with free- head boundary conditions). For piles with fixed head boundaries (i.e. rotation restrained piles) shear deformations could be of significant influence. To study this problem, a coupled shear flexure interaction model for axial-bending-shear behavior coded in OpenSees is applied to a 0.61 m flagpole and a 0.61m fixed head pile specimen to investigate the possible influence of shear deformations to the overall pile responses. The surrounding soil is represented by p-y curves derived from prior large scale testing on piles with similar boundary conditions. Analysis results show that for flagpole piles, shear forces and shear deformations were insignificant. Considerable contributions of pile shear displacements and forces were observed for the fixed head pile, with shear displacements contributing up to 40% of the total pile displacement. Results suggest that nonlinear shear deformations for reinforced concrete piles should be considered for fixed-head or similar conditions, and that currently used p-y curves may underestimate the actual lateral pile displacement and possibly lead to unsafe design for the particular boundary condition.

Jan 1, 2011