John B. Mander

Bio: John B. Mander is an academic researcher from Texas A&M University. The author has contributed to research in topics: Precast concrete & Earthquake engineering. The author has an hindex of 44, co-authored 237 publications receiving 12167 citations. Previous affiliations of John B. Mander include University at Buffalo & State University of New York System.

Theoretical stress strain model for confined concrete

Abstract: A stress‐strain model is developed for concrete subjected to uniaxial compressive loading and confined by transverse reinforcement. The concrete section may contain any general type of confining steel: either spiral or circular hoops; or rectangular hoops with or without supplementary cross ties. These cross ties can have either equal or unequal confining stresses along each of the transverse axes. A single equation is used for the stress‐strain equation. The model allows for cyclic loading and includes the effect of strain rate. The influence of various types of confinement is taken into account by defining an effective lateral confining stress, which is dependent on the configuration of the transverse and longitudinal reinforcement. An energy balance approach is used to predict the longitudinal compressive strain in the concrete corresponding to first fracture of the transverse reinforcement by equating the strain energy capacity of the transverse reinforcement to the strain energy stored in the concret...

Observed Stress‐Strain Behavior of Confined Concrete

Abstract: Thirty‐one nearly full‐size reinforced concrete columns, of circular, square, or rectangular wall cross section, and containing various arrangements of reinforcement, were loaded concentrically with axial compressive strain rates of up to 0.0167/s. The circular sections contained longitudinal and spiral reinforcement, the square sections contained longitudinal reinforcement and square and octagonal transverse hoops, and the rectangular wall sections contained longitudinal reinforcement and rectangular hoops with or without supplementary cross ties. The longitudinal stress‐strain behavior of the confined concrete was measured and compared with that predicted by a previously derived stress‐strain model with allows for the effects of various configurations of transverse confining reinforcement, cyclic loading, and strain rate. The measured longitudinal concrete compressive strain when the transverse steel first fractured was also compared with that predicted by equating the strain energy capacity of the tran...

Seismic Performance of Precast Reinforced and Prestressed Concrete Walls

Abstract: Two geometrically identical half-scale precast concrete cantilever wall units were constructed and tested under quasi-static reversed cyclic lateral loading. One unit was a code compliant conventionally reinforced specimen, designed to emulate the behavior of a ductile cast-in-place concrete wall. The other unit was part of a precast partially prestressed system that incorporated post-tensioned unbonded carbon fiber tendons and steel fiber reinforced concrete. Hysteretic energy dissipation devices were provided in the latter unit in the form of low yield strength tapered longitudinal reinforcement, acting as a fuse connection between the wall panel and the foundation beam. The conventional precast reinforced wall performed very well in terms of the ductility capacity and energy absorption capability, reaching 2.5% drift before significant strength degradation occurred. The precast partially prestressed wall unit achieved drift levels well in excess of 3% with no visible damage to the wall panel prior to failure. Test results and performance comparisons between the precast partially prestressed wall system and the precast conventionally reinforced unit are presented.

Seismic design of bridge piers

Abstract: This thesis studies the seismic design of bridge piers. An analytical model for predicting the stress-strain behaviour of reinforcing steel under dynamic cyclic loading was derived. A generalised stress-strain model for plain or confined concrete under dynamic cyclic axial compression loading is presented. To verify the model, axial compression tests were carried out on 15 circular columns with spiral reinforcement, 16 rectangular walls and 5 square columns with rectilinear hoops. In the case of both models theoretical predictions compare well with experimental behaviour. A ductile design methodology for bridges is presented. A theoretical model is developed to predict the lateral load-deformation behaviour, and thus ductility capability, of reinforced concrete columns under axial load and cyclic flexure. Design charts are prepared to enable the rotational capacity of columns with confined concrete to be assessed. An experimental investigation into the seismic performance of ductile hollow reinforced concrete columns is described, in which 40 percent full size specimens, containing different amounts of confining steel in the plastic hinge zone were subjected to constant axial load and cyclic lateral displacements. Member ductilities between 6 and 8 were obtained and no significant strength degradation under cyclic loading was observed. Predictions from the model are found to compare well with experimental results. (TRRL)

Theoretical stress strain model for confined concrete

Abstract: A stress‐strain model is developed for concrete subjected to uniaxial compressive loading and confined by transverse reinforcement. The concrete section may contain any general type of confining steel: either spiral or circular hoops; or rectangular hoops with or without supplementary cross ties. These cross ties can have either equal or unequal confining stresses along each of the transverse axes. A single equation is used for the stress‐strain equation. The model allows for cyclic loading and includes the effect of strain rate. The influence of various types of confinement is taken into account by defining an effective lateral confining stress, which is dependent on the configuration of the transverse and longitudinal reinforcement. An energy balance approach is used to predict the longitudinal compressive strain in the concrete corresponding to first fracture of the transverse reinforcement by equating the strain energy capacity of the transverse reinforcement to the strain energy stored in the concret...

Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Concrete Structures

Abstract: *Co-chairs of the subcommittee that prepared this document. Note: The committee acknowledges the contribution of associate member Paul Kelley. ACI encourages the development and appropriate use of new and emerging technologies through the publication of the Emerging Technology Series. This series presents information and recommendations based on available test data, technical reports, limited experience with field applications, and the opinions of committee members. The presented information and recommendations, and their basis, may be less fully developed and tested than those for more mature technologies. This report identifies areas in which information is believed to be less fully developed, and describes research needs. The professional using this document should understand the limitations of this document and exercise judgment as to the appropriate application of this emerging technology.

Compressive behaviour of concrete at high strain rates

Abstract: Experimental techniques commonly used for high strain-rate testing of concrete in compression, together with the methods used for measurement and recording of stress and strain, are critically assessed in the first part of this paper. The physical capability of each loading method is discussed and some consideration is given to the definitions used for specifying the loading rate. The second part reviews the dynamic compressive strength (mostly uniaxial rather than bi- or triaxial) of plain concrete, while in the third part a review on deformation behaviour indicates that uncertainty and disagreement exist concerning changes in axial strain at high strain rates.

Design-oriented stress–strain model for FRP-confined concrete

Abstract: External confinement by the wrapping of FRP sheets (or FRP jacketing) provides a very effective method for the retrofit of reinforced concrete (RC) columns subject to either static or seismic loads. For the reliable and cost-effective design of FRP jackets, an accurate stress–strain model is required for FRP-confined concrete. In this paper, a new design-oriented stress–strain model is proposed for concrete confined by FRP wraps with fibres only or predominantly in the hoop direction based on a careful interpretation of existing test data and observations. This model is simple, so it is suitable for direct use in design, but in the meantime, it captures all the main characteristics of the stress–strain behavior of concrete confined by different types of FRP. In addition, for unconfined concrete, this model reduces directly to idealized stress–strain curves in existing design codes. In the development of this model, a number of important issues including the actual hoop strains in FRP jackets at rupture, the sufficiency of FRP confinement for a significant strength enhancement, and the effect of jacket stiffness on the ultimate axial strain, were all carefully examined and appropriately resolved. The predictions of the model are shown to agree well with test data.