International Concrete Abstracts Portal

Through a Change Proposal by Facca Incorporated, the Ontario Ministry of Transportation (MTO) approved the replacement of the as-tendered steel H-piles by newly designed prestressed/precast Ultra-High-Performance Concrete (UHPC) piles for supporting the west abutment of the Lily River Detour Bridge. The 300 mm (~12”) deep UHPC piles were designed and installed at the west abutment based on the previous successful development and testing of a tapered H-shaped pile at Iowa State University. The east abutment, as tendered, was designed to be supported by six steel H-shaped battered piles driven to bedrock. For the west abutment, six UHPC piles were produced and installed using the same batter. Since the site contained occasional boulders and the design intent to drive the piles to bedrock, the UHPC piles were fitted with steel shoes for the first time. All piles were successfully installed to reach the targeted load bearing capacities. After the replacement bridge was constructed, the detour bridge was removed and the UHPC piles were extracted to examine the conditions of the piles. This presentation will provide details of the innovative design of the piles, fabrication and driving of the piles, and lessons learned from analyzing the driving data and removal of the piles. Fellowship and Scholarship recipients. With the help of generous donors from the concrete community, the ACI Foundation awards high-potential undergraduate and graduate students in engineering, construction management, and other appropriate curricula.

The “Notional Pile” formulation is developed for modeling a group of piles in a foundation. It is a new procedure for foundation modeling for dynamic analysis in conformance with ACI 351.3R. It is an augmentation of the well-known Novak procedure. Foundation stiffness is represented as a set of notional pile elements. This differs from conventional procedures in which the pile group stiffness is represented by a set of springs lumped at one point. With notional piles and finite element modeling of the cap, flexible-cap modes of vibration can be extracted. With conventional procedures, only lower-frequency rigid body modes can be extracted. Notional piles distribute stiffness more realistically and enable cap-pile interaction. A specific case is used to illustrate the new procedure. For that case, the cap did not have a regular distribution of mass or stiffness. Dynamic loads were applied with considerable eccentricity, at multiple locations and with multiple frequencies. Notional piles accommodated these irregularities. The notional pile formulation was validated by comparing measured to computed foundation responses. The comparison was good but not great. The foundation was to be reconfigured for new machinery. The retrofit design was modeled using notional piles. Responses were computed and compared to applicable limits.

Many common building materials, such as concrete and steel, are understood to experience a change in apparent material properties under high strain rates. This effect is often incorporated into impact and blast design by using dynamic increase factors (DIFs) that modify properties of the material such as strength and stiffness when subjected to high strain rates. There is currently limited guidance on dynamic properties of fiber reinforced polymer (FRP) sheets bonded to concrete. Since FRP is a common retrofit material for blast and impact load vulnerable structures, it is important to have a full understanding on the behaviour of the FRP material and of the composite action between the FRP sheet and the substrate it is bonded to. Important parameters for blast and impact resistant design of reinforced concrete structures retrofitted with surface bonded FRP include dynamic measures of debonding strain, development length, and bond stress. This paper presents the results of an experimental program measuring the dynamic properties of carbon fiber reinforced polymer (CFRP) sheets bonded to concrete under impact induced high strain rates.

A series of rectangular concrete prisms were cast and fitted with surface bonded CFRP sheets to facilitate pull-out shear tests that directly measure the FRP to concrete bond. The bonded length of the CFRP sheet was variable with three different lengths explored. A series of static tests have been conducted to measure the strain fields on the FRP sheets under load up to failure. These strain fields, which were measured with digital image correlation techniques, were used to determine development length, bond stress, and ultimate strain of the FRP sheet prior to debonding. A companion set of prisms have also been cast and will be tested under impact loading to explore the same properties at high strain rates of around 1 s-1. Initial test results indicate a potential increase in both ultimate strain and bond stress, and a decrease in development length under high strain rates. The results of the larger study will be compiled and, when compared with the static companion set, be used to propose DIFs for FRP sheets bonded to concrete for use in design in high strain rate applications.

However, the main constitutive phases of SHCC, i.e. matrix, fibers and interphase between them, are highly rate sensitive. Depending on the SHCC composition, the increase in loading rates can negatively alter the balanced micromechanical interactions, leading to a pronounced reduction in strain capacity. Thus, there is need for a detailed investigation of the strain rate sensitivity of SHCC at different levels of observation for enabling a targeted material design with respect to high loading rates.

The crack opening behavior is an essential material parameter for SHCC, since it defines to a large extent the tensile properties of the composite. In the paper at hand, the rate effects on the crack opening and fracture behavior of SHCC are analyzed based on quasi-static and impact tensile tests on notched specimens made of three different types of SHCC. Two SHCC consisted of a normal-strength cementitious matrix and were reinforced with polyvinyl-alcohol (PVA) and ultra-high molecular weight polyethylene (UHMWPE) fibers, respectively. The third type consisted of a high-strength cementitious matrix and UHMWPE fibers. The dynamic tests were performed in a split Hopkinson tension bar and enabled an accurate description of the crack opening behavior in terms of force-displacement relationships at displacement rates of up to 6 m/s (19.7 ft/s).

The purpose of the LaGuardia Runway Extension Project is to extend existing runways 4-22 and 13-31 into Flushing Bay, at the inshore end of Long Island Sound, to support Engineered Material Arresting System (EMAS) - a crushable material installed at the end of each runway to reduce the risk of a plane overrun during takeoff.

The new runway deck extensions are marine concrete structures which utilize precast prestressed pile caps with a pre and post-tensioned composite precast deck and cast-in-place concrete topping slab. The concrete decks are supported by 250 ton (227 tonnes) 24 inch (61cm) diameter epoxy coated closed end concrete filled steel pipe piles with specialized wraps and sacrificial zinc anodes for corrosion protection. The piles are approximately 100 feet (30m) long and driven in about 30 feet (9m) of water through soft organic clay and dense glacial soils and founded on bedrock.

This paper provides an overall description of the runway extensions and a detailed account of both the technical and logistical challenges. Challenges included a prestressed composite deck design for both the aircraft impact and braking loads. Maintaining and replacing the lightbars of the Approach Lighting Systems (ALS) used to visually identify the runways was required, along with optimizing the pile hammer selection and driveability with wave equation analyses and dynamic pile driving PDA testing. Extensive coordination was necessary with the PANYNJ, FAA and various other stakeholders involved in this fast-paced design build project.

This paper presents the development of a new type of fiber reinforced polymer (FRP) composites jacket and the evaluation to demonstrate the application of this pre-fabricated composite repair system for rehabilitation of deteriorating concrete columns. The novelty of this fiber composite strengthening system is that it is quick and safe to install due to the easy-fit and self-locking mechanical joint. An intensive characterisation of the mechanical properties of the composite resin for the interlocking teeth and locking key of the jacket was conducted. Similarly, finite element (FE) simulation on the behaviour of the FRP jacket subjected to internal pressure was performed and verified through full-scale experimental testing. Finally, the behaviour of concrete columns with simulated steel corrosion defect and repaired with a composite jacket was investigated. The results showed that the provision of FRP jacket restored the axial capacity of concrete columns with 25% and 50% corrosion damage up to 99% and 95%, respectively.