Concrete Pile Caps Research Articles

Crack Down on Water Tank Foundation Problems

This article discusses how to determine if cracks in the foundation of concrete storage tanks are superficial or are a real structural problem. The article describes the city of Virginia Beach, Virginia's experience with alkali silica reaction (ASR) on the deteriorating concrete pile caps of the tank foundations, discusses how the city investigated and evaluated the damage, and the repairs that were required. The article provides an inset of information from AWWA Manual M42, Steel Water Storage Tanks, that indicates who should be responsible for storage tank foundation design.

Failure Probabilities of Reinforced Concrete Square Pile Caps

AbstractAn analytical model for determining the shear strength of concrete pile caps under the failure mode of diagonal-compression originally based on the softened strut-and-tie model is proposed. The failure probabilities of reinforced concrete pile caps are investigated by Monte Carlo method. The results indicate that the proposed model can accurately predict the shear strength of the pile caps. The distribution of the failure probabilities for pile caps designed to ACI 318-02 Appendix A and the proposed design method are more uniform than that designed to the ACI 318-99. The ACI 318-99 is very conservative and cannot provide a consistent safety for pile caps design. It is suggested that the procedures in the ACI 318-02 Appendix A should be moved to the main body of ACI 318-02 and the proposed design method should be incorporated into the current reinforced concrete pile cap design methods.

Cyclic Lateral Load Behavior of a Pile Cap and Backfill

A series of static cyclic lateral load tests were performed on a full-scale 4×3 pile group driven into a cohesive soil profile. Twelve 324-mm steel pipe piles were attached to a concrete pile cap 5.18×3.05 m in plan and 1.12 m in height. Pile–soil–pile interaction and passive earth pressure provided lateral resistance. Seven lateral load tests were conducted in total; four tests with backfill compacted in front of the pile cap; two tests without backfill; and one test with a narrow trench between the pile cap and backfill soil. The formation of gaps around the piles at larger deflections reduced the pile–soil–pile interaction resulting in a degraded linear load versus deflection response that was very similar for the two tests without backfill and the trenched test. A typical nonlinear backbone curve was observed for the backfill tests. However, for deflections greater than 5 mm, the load-deflection behavior significantly changed from a concave down shape for the first cycle to a concave up shape for the ...

Seismic Retrofit of State Street Bridge on Interstate 80

The State Street Bridge, in Salt Lake City, was designed and built in 1965 according to the 1961 AASHO specifications; the design did not include earthquake-induced forces or displacements since only wind loads were considered. The bridge consists of four reinforced concrete (RC) bents supporting composite welded steel girders; the bents are supported on cast-in-place concrete piles and pile caps. A vulnerability analysis of the bridge was conducted that determined deficiencies in (1) confinement of column lap splice regions, (2) anchorage of longitudinal column bars in the bent cap, (3) confinement of column plastic hinge zones, and (4) shear capacity of columns and bent cap.column joints. Seismic retrofit designs using carbon-fiber-reinforced-polymer (CFRP) composites and steel jackets were performed and compared for three design spectra, including the 10% probability of exceedance in 250 years earthquake. The CFRP composite design was selected for implementation and application of the composite was carried out in the summer of 2000 and 2001, while the bridge was in service. The paper describes the CFRP composite design, which, in addition to column jackets, implemented an ”ankle wrap” for improving joint shear strength and a ”U-strap” for improving anchorage of column bars in the bent cap; other retrofit measures were implemented, such as bumper brackets and a deck slab retrofit. A capacity versus demand evaluation of the as-built and retrofitted bents is presented.

Development of a Specification for Bridge Seismic Retrofit with Carbon Fiber Reinforced Polymer Composites

The U.S. Interstate 80 bridge over State Street in Salt Lake City is very near the Wasatch fault, which is active and capable of producing large earthquakes. The bridge was designed and built in 1965 according to the 1961 American Association of State Highway Officials specifications, which did not consider earthquake-induced forces or displacements. The bridge consists of reinforced concrete bents supporting steel plate welded girders. The bents are supported on cast-in-place concrete piles and pile caps. A seismic retrofit design was developed using carbon fiber reinforced polymer (CFRP) composites, which was implemented in the summer of 2000 and the summer of 2001, to improve the displacement ductility of the bridge. The seismic retrofit included column jacketing, as well as wrapping of the bent cap and bent cap-column joints for confinement, flexural, and shear strength increase. This paper describes the specifications developed for the CFRP composite column jackets and composite bent wrap. The specifications included provisions for materials, constructed thickness based on strength capacity, and an environmental durability reduction factor. Surface preparation, finish coat requirements, quality assurance provisions, which included sampling and testing, and constructability issues regarding the application of fiber composite materials in the retrofit of concrete bridges are also described.

Strength of reinforced concrete pile caps

Discrepancies exist in the provisions for the design of reinforced concrete pile caps with regard to shear, between the two UK codes for structural concrete design, namely BS 8110 and BS 5400. These discrepancies have arisen in the historical development of the codes, and the implication is that one code is unsafe or the other is over-conservative. This paper summarises the current code requirements, the nature of the discrepancies, and the reasons why they have arisen. A review is given of the available experimental data on the strength of pile caps, and their usefulness in addressing the code discrepancies. Inadequacies in this experimental knowledge base, and the need for further research, are highlighted.

Strength of reinforced concrete pile caps

Discrepancies exist in the provisions for the design of reinforced concrete pile caps with regard to shear, between the two UK codes for structural concrete design, namely BS 8110 and BS 5400. These discrepancies have arisen in the historical development of the codes, and the implication is that one code is unsafe or the other is over-conservative. This paper summarises the current code requirements, the nature of the discrepancies, and the reasons why they have arisen. A review is given of the available experimental data on the strength of pile caps, and their usefulness in addressing the code discrepancies. Inadequacies in this experimental knowledge base, and the need for further research, are highlighted.

Single Piles in Lateral Spreads: Field Bending Moment Evaluation

The results of the six centrifuge models of instrumented single pile foundations presented in a companion paper, are used to calibrate two limit equilibrium (LE) methods to evaluate bending response and factor of safety against bending failure of piles in the field subjected to lateral spreading. These six models simulate single reinforced concrete piles in two- and three-layer soil profiles, mostly end bearing but including also one floating pile, with and without a reinforced concrete pile cap, and one model where the liquefiable sand layer was densified locally around the pile to simulate the effect of pile driving. The measured permanent maximum bending moments in the pile, Mmax, invariably occurred at the boundaries between liquefied and nonliquefied soil layers, and in most cases the moments at such boundaries reached their peak Mmax and then decreased during shaking. These values of Mmax before decrease, which were associated with failure of the soil against the deep foundation, are used to calibra...

Rotational Restraint of Pile Caps during Lateral Loading

A pure fixed-head (zero-rotation) condition at the top of a group of laterally loaded piles is seldom achievable in the field, even when piles are installed in a group that is “rigidly” constrained by a stiff concrete pile cap. Assuming complete fixity during design (zero rotation at the pile head) can result in underestimated values of pile-head deflection, and incorrect estimates of the magnitude and the location of maximum bending moments. A simple and practical approach is presented for estimating the moment restraint that is provided by the pile cap at the top of a pile group. The moment restraint, represented by the rotational restraint coefficient (KMθ), serves as a boundary condition for analyzing groups of laterally loaded piles. Full-scale field tests performed on two pile groups with concrete pile caps show that the proposed method for estimating rotational restraint provides results that are in good agreement with measured field performance.

Lateral Resistance of Full-Scale Pile Cap with Gravel Backfill

A static lateral load test was performed on a full-scale 3×3 pile group driven in saturated low-plasticity silts and clays. The steel pipe piles were attached to a concrete pile cap which created a “fixed-head” end constraint. A gravel backfill was compacted in place on the backside of the cap. Lateral resistance was therefore provided by pile–soil–pile interaction, as well as base friction and passive pressure on the cap. In this case, passive resistance contributed about 40% of the total resistance. The log–spiral method provided the best agreement with measured resistance. Estimates of passive pressure computed using the Rankine method significantly underestimated the resistance while the Coulomb method overestimated resistance. The cap movement required to fully mobilize passive resistance in the gravel backfill was about 6% of the cap height. This is somewhat larger than reported in other studies likely due to the underlying clay layer. The p-multipliers developed for the free-head pile group provided reasonable estimates of the pile–soil–pile resistance for the fixed-head pile group once gaps adjacent to the pile were considered.

Behaviour of precast reinforced concrete pile caps

The objective of this investigation is to study the behaviour of precast reinforced concrete pile caps and the ultimate load-carrying capacity. Three pile cap units were cast and tested to failure. One unit was a control pile cap cast in situ and the other two were precast reinforced units with in situ concrete infill. The experimental results showed that the precast pile cap behaved in a similar manner as compared with the conventional cast in situ pile cap. Furthermore, all the three units failed at loads exceeding the failure loads predicted using conventional design methods and exhibited predicted failure modes. In addition, there was a substantial increase in productivity as the precast pile caps could be constructed quickly and thus reducing the risk of exposing the excavated pit to rain and possible failure of the unsupported sides.

Lateral Load Capacity and Passive Resistance of Full-Scale Pile Group and Cap

Static and dynamic (statnamic) lateral load tests were performed on a full-scale 3 × 3 pile group driven in saturated low-plasticity silts and clays. The 324-mm outside diameter steel pipe piles were attached to a reinforced concrete pile cap (2.74 m square in plan and 1.21 m high), which created an essentially fixed-head end constraint. A gravel backfill was compacted in place on the back side of the cap. Lateral resistance was therefore provided by pile-soil-pile interaction as well as by base friction and passive pressure on the cap. In this case, passive resistance contributed about 40 percent of the measured static capacity. The measured resistance was compared with that computed by several techniques. The log-spiral method provided the best agreement with measured resistance. Estimates of passive pressure computed using the Rankine or GROUP p-y curve methods significantly underestimated the resistance, whereas the Coulomb method overestimated resistance. The wall movement required to fully mobilize passive resistance in the dense gravel backfill was approximately 0.06 times the wall height, which is in good agreement with design recommendations. The p-multipliers developed for the free-head pile group provided reasonable estimates of the pile-soil-pile resistance for the fixed-head pile group. Default p-multipliers in the program GROUP led to a 35 percent overestimate of pile capacity. Overall dynamic resistance was typically 100 to 125 percent higher than static; however, dynamic passive pressure resistance was over 200 percent higher than static.

4本杭支持独立フーチングの曲げ耐力に関する実験的研究

In this paper seventy-six reinforced concrete pile caps, each with four piles, were tested under vertical load. The variables involved were spacing of piles, arrangement of reinforcement, reinforcement ratio, side length of column and depth of pile cap. In regard to the bending ultimate strength the results of the test were compared with the calculated values according to the provision for the bending in A.I.J. Standard for Structural Calculation of Reinforced Concrete Structures and to the equations proposed by others as well as to that by authors. To conclude the discussions the calculated values according to the authors' equation agreed well with the experimental results.

Nonlinear finite element analysis of reinforced concrete four-pile caps

An investigation to study the behaviour of reinforced concrete four-pile caps by three-dimensional nonlinear finite element analysis is presented. Four-pile caps having different reinforcement layouts were considered. Eight-noded isoparametric brick elements with incompatible modes and two-noded three-dimensional truss elements were used to model the concrete and steel, respectively, of the pile caps. The steel elements were assumed to lie on the edges of the brick elements. The smeared cracking model was employed for modelling cracks during the analysis. The nonlinear components, such as multiaxial compressive behaviour of concrete, including strain softening, cracking of concrete and yielding of steel reinforcement, were considered. The load deflection characteristics, the strains in the reinforcement, the crack patterns and the ultimate loads are presented herein. Some of the theoretical results are compared with those obtained from experiments carried out on reinforced concrete pile cap specimens.

ORWELL BRIDGE - CONSTRUCTION.

Keywords SIR WILLIAM HALCROW STEVIN CONSTRUCTION ORWELL BRIDGE, CONSTRUCTION, BRIDGES, RIVERS, SITES, BANKS, PLANNING, STRUCTURES, VIADUCTS, MUD FLATS, COMPLETION, ABUTMENTS, SPANS, MAIN, CENTRAL, SECTIONS, ENDS, CONTRACTS, APPROACHES, EMBANKMENTS, CONTRACTORS, TENDERS, TEMPORARY, WORKS, METHODS, FOUNDATIONS, PILES, SUBSTRUCTURES, BORED, CAST, REINFORCED, CONCRETE, CAP, PIERS, PRESTRESSED, BOX, GIRDERS, DECKS, TWIN, EARTHWORKS, PILING, ACCESS, TESTING, THERMAL, CRACKING, CONTROL, NAVIGATION, CLOSURES, GROUTING, QUALITY, PLANT, EQUIPMENT, MIXERS, WORKSHOPS, COMMUNICATIONS, DISTRIBUTION ORWELL, IPSWICH, EAST ANGLIA UK... Show All