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The use of unbonded posttensioned (UPT) precast concrete walls with horizontal joints as the primary lateral load resisting system in seismic zones has been considered in several previous studies. This paper introduces a design-oriented analytical model that uses simple formulae to estimate the nonlinear lateral load behavior of UPT walls, and compares this simple model with available experimental results. A previously developed UPT wall model based on fiber elements is also compared with experimental results. Each model is formulated to consider several critical limit states in the lateral load behavior of UPT walls. Comparisons showed generally good agreement between analytical and experimental results for three different test walls under monotonic and cyclic loading. The simple model is found to be sufficiently accurate for seismic design of UPT walls, and the fiber model is found to be sufficiently accurate for estimating UPT wall response under earthquake loading. DOI: 10.1061/(ASCE)0733-9445 (2007) 133:11 (1531) CE Database subject headings: Concrete, precast; Concrete, prestressed; Shear walls; Post tensioning; Seismic design; Seismic analysis.

The construction of low damage, self-centering, unbonded post-tensioned seismic systems requires special techniques and equipment such as hydraulic jacks to stress tendons that may not be readily available in developing communities. The recently proposed spring anchored rocking system (SARS) uses a spring at the anchorage of the post-tensioning tendon to facilitate applying force to the tendons using simple techniques such as torque wrenches. The seismic behaviour of the SARS is investigated using finite element models developed in OpenSees. The self-centering lateral force resisting system of a 3-story timber structure was anchored with springs having four different configurations, and subjected to a set of 22-pair ground motions. The finite element models consisted of elastic beam column elements to model the frame members, nonlinear truss element to model the post-tensioning tendon, spring element to model the anchorage of the tendon, and gap element to model the spring closure. It is found that the spring at the post-tensioning anchorage introduces flexibility, reduces the tendon force, and generally increases the rigid body deformations of the SARS compared to conventionally anchored systems using nuts set on bearing plates. [ABSTRACT FROM AUTHOR]

This article investigates the use of photon attenuating inclusions (PAI) for enhancing radiographic imaging of cementitious materials in composite structures. By targeting characteristic high attenuation regions in the photon energy spectrum, PAI can improve void detection in the parent material by increasing contrast in radiographic images. Radiographic imaging of cementitious grout specimens with 5% and 15% weight fractions of candidate PAI materials (Fe, BaCO3, BaSO4) was performed to characterize X-ray attenuation. Virtual radiography simulations were then conducted to evaluate the application of PAI to grout void detection in post-tensioned concrete construction. The simulations demonstrate that grout void detection is most effective when the high energy region of the emission spectrum is near the K-edge of the PAI material. [ABSTRACT FROM AUTHOR]