Why did modern post-tensioned floors flourish in the us and not in europe -a matter of tradition?

Unlike in Europe, prestressed concrete with post-tensioned reinforcement came to be a standard technique in building construction in the US. Kenneth Bondy has been the only one who has made a significant contribution to clarify why this occurred, by writing about his insights on the origins of post-tensioned floors in the United States. His vision is completed here with new data and put into context. Moreover, the American and European situations are compared in an attempt to explain why things developed so differently on each side of the Atlantic.Peer ReviewedPostprint (published version

Modelling and parametric study of the re-anchorage of ruptured tendons in bonded post-tensioned concrete

The contribution of ruptured tendons to the residual strength of bonded post-tensioned concrete structures is currently assessed based on pre-tensioned concrete bond models. However, this approach is inaccurate due to the inherent differences between pre-tensioned and post-tensioned concrete. In this paper, a non-linear 3D finite element model is developed for the re-anchoring of a ruptured tendon in post-tensioned concrete. The model is validated using full-field displacement measurement from 33 post-tensioned concrete prisms and previous experimental data on beams from the literature. The influence of different parameters was investigated, including tendon properties (i.e. diameter, roughness), duct properties (i.e. diameter, thickness, material), initial prestress, concrete strength, grout strength, grout voids, stirrups, and strands, on the tendon re-anchorage. The most influential parameters are found to be tendon and duct properties

Preliminary performance-based design of a post-tensioned glue-laminated timber frame

Post-tensioned timber joints have been studied at the ,nstitute of Structural Engineering at the ETH =urich. A post-tensioned beam-column timber joint has been developed using glued laminated timber with local hardwood reinforcement. 2nly a single straight tendon is placed in the middle of the beam and post-tensioned to restrain the rotation of the joint. 1o additional steel elements are used. The developed joint is characterised by a high degree of pre-fabrication and easy assembly on site. The glue-laminated timber moment-resisting frame featuring this joint shows great potential for timber frame structures especially for multi-storey buildings. Robust performance-based design criteria are a necessity for a s uccessful market implementation of the proposed system. A simplified analytical model was developed in order to predict the structural performance of the post-tensioned timber connection and facilitate preliminary performance-based design. This model was implemented in 2penSees using a bi-linear rotational spring approach. The model was verified against an analytical model and validated against tests on a post-tensioned timber joints under gravity loading and under horizontal loading. Moreover, a complex numerical model was developed using 2penSees to check the accuracy of the proposed preliminary design model. The preliminary design model was used to design fictitious moment-resisting post-tensioned glue-laminated timber frame structures using the loads prescribed in the Swiss code. The design process showed that neither the gravity loads nor the seismic load controlled the design. The design was governed by the lateral deformations due to wind. Based on this finding it is recommended to focus further research on increasing the connection stiffness or on adding additional structural elements to address the seismic performance of post-tensioned timber frames in regions of high seismicity

Re-anchorage of a ruptured tendon in bonded post-tensioned concrete beams: model validation

Many post-tensioned concrete bridges have been reported to have ruptured tendons due to corrosion [1] and the assessment of their residual structural capacity has to account for the possibility of re-anchorage of failed tendons. This paper presents an experimental programme to validate a numerical model developed by the authors for the re-anchorage of a ruptured tendon in post-tensioned concrete [2]. The experimental programme considered 33 post-tensioned concrete prisms, in which the rupture of tendon was simulated by releasing the tendon at one end. The full field displacement at concrete surface after release was measured using 3D Electronic Speckle Pattern Interferometry (ESPI). A wide range of parameters: tendon diameter, duct material, grout strength, concrete strength and shear reinforcement were investigated to validate the proposed model, which is found to be suitable for use in assessing post-tensioned concrete bridges with damaged tendons

Experimental and numerical investigation of post-tensioned concrete flat slabs in fire

Purpose This paper aims to understand the structural fire performance of two-way post-tensioned flat slabs, particularly their deformations and load-carrying mechanisms in fire, and to explore the behaviour of post-tensioned high-strength self-compacting concrete flat slabs with unbonded tendons in fire. Design/methodology/approach Four tests of post-tensioned high-strength self-compacting concrete flat slabs were conducted under fire conditions. Numerical modelling using the commercial package ABAQUS was conducted to help interpret the test results. Findings Two of the specimens with lower moisture contents demonstrated excellent fire resistance performance, while the others with slightly higher moisture contents experienced severe concrete spalling. Originality/value The test results were discussed in respect of thermal profiles, deflections, crack patterns and concrete spalling. The performance of post-tensioned high-strength self-compacting concrete flat slabs with unbonded tendons under fire conditions was better understood.postprin

Towards the “ultimate earthquake-proof” building: Development of an integrated low-damage system

The 2010–2011 Canterbury earthquake sequence has highlighted the severe mismatch between societal expectations over the reality of seismic performance of modern buildings. A paradigm shift in performance-based design criteria and objectives towards damage-control or low-damage design philosophy and technologies is urgently required. The increased awareness by the general public, tenants, building owners, territorial authorities as well as (re)insurers, of the severe socio-economic impacts of moderate-strong earthquakes in terms of damage/dollars/ downtime, has indeed stimulated and facilitated the wider acceptance and implementation of cost-efficient damage-control (or low-damage) technologies. The ‘bar’ has been raised significantly with the request to fast-track the development of what the wider general public would hope, and somehow expect, to live in, i.e. an “earthquake-proof” building system, capable of sustaining the shaking of a severe earthquake basically unscathed. The paper provides an overview of recent advances through extensive research, carried out at the University of Canterbury in the past decade towards the development of a low-damage building system as a whole, within an integrated performance-based framework, including the skeleton of the superstructure, the non-structural components and the interaction with the soil/foundation system. Examples of real on site-applications of such technology in New Zealand, using concrete, timber (engineered wood), steel or a combination of these materials, and featuring some of the latest innovative technical solutions developed in the laboratory are presented as examples of successful transfer of performance-based seismic design approach and advanced technology from theory to practice

Prestress loss of post-tensioned clay diaphragm and fin brickwork

Unlike calcium silicate and concrete block masonry which undergo shrinkage with time, clay brickwork has been known to expand instead. Expansion of brick units in prestressed masonry will cause an increase in the prestressing force instead of prestress loss. However, not all clay brickwork expand with time; higher strength clay units tend to undergo shrinkage with time. The main objective of this paper is to present experimental data obtained for prestress loss in post-tensioned high strength clay diaphragm and fin brickwork. The main objective of this paper is to present experimental data obtained for prestress loss in posttensioned high strength clay diaphragm and fin brickwork. The brickwork were built from clmisB clay engineering brick with compressive strength of 103 MPa with designation (ii) mortar. The tests which involve monitoring prestress loss, creep and shrinkage of clay sections were carried out over a period of 120 days. Usiog the 120-day experimental data, the predicted long-term prestress loss is 20

Investigation of prestressed reinforced concrete for highway bridges, part V, analysis and control of anchorage-zone cracking in prestressed concrete

Cover title.Prepared as part of an investigation conducted by the Engineering Experiment Station, University of Illinois at Urbana-Champaign