The New Zealand Structural Loading Standard, until its latest revision, was using the structural displacement ductility factor as a measure of the deformation demand of all potential plastic hinges in a structure. In the revised version of New Zealand Structural Loading Standard for Earthquake Actions (NZS 1170.5:2004) the detailing of potential plastic regions is determined according to the local inelastic deformation demand in these regions. The change has been prompted by evidence that the structural ductility factor gives a poor indication of the demand on individual plastic regions. This is a major paradigm shift in international design codes. This new approach has been adopted by the New Zealand Concrete Structures Standard (NZS 3101:2006) which classifies potential plastic regions into three categories (namely ductile, limited ductile and nominally ductile) based upon their inelastic deformation demand which has been specified in terms of material strain limits in the form of curvatures or shear deformations. The values of material strain limits currently used in New Zealand Concrete Standard (NZS 3101:2006) to categorise the plastic regions are based on limited evidence and need a closer revision. This research attempts to obtain more justifiable values of material strain limits through experimental data existing in literature. Moreover, experimental testing is also conducted to compensate for a lack of data in the nominally ductile range of detailing. The experimental work explores the effects of transverse reinforcement arrangement, reinforcing steel grade and plastic hinge type. Together the literature review and experimental work provide a sound basis for re-defining the material strain limits for different plastic regions.

Glass Fibre Reinforced Polymer (GFRP) internal reinforcing bars are being increasingly considered as a potential corrosion free alternative to regular and stainless steel reinforcing bars. In spite of the availability of code provisions governing both design and certification of the GFRP bars, their use within concrete structures is currently limited to very specific applications unless some behaviour aspects are further investigated. In particular, crack control, ultimate member deformability and the behaviour of the bent GFRP bars are areas in need of such further investigation. An experimental program was conducted consisting of 24 large-scale beams reinforced with various types of GFRP and steel bars complying with CSA certification standards. The results of which show that the stress in the bent bar stirrups at beam failure exceeded minimum code-prescribed values for design (CSA S6, CSA S806, ACI440). An alternative bend-less system of shear reinforcement using straight double headed bars was successful as shear reinforcement but did however result in significant reductions to member deformability. A critical review of the various design provisions incorporating GFRP shear reinforcement, it was found that many of the design codes use conservative shear reinforcement strengths coupled with unconservative values of either the angle of inclination of the compression strut or the concrete contribution to shear resistance. A new relationship for the inclination of the compression strut was proposed for use within the Simplified Modified Compression Field Theory which when combined with the bend/anchor strength of the shear reinforcement correlate well with the experimental results. Also, it was determined that the design strain limits for GFRP shear reinforcement should not be increased until more detailed studies on the long-term performance of the stirrups are conducted. Finally, advanced analysis techniques like layered sectional- and finite element-analysis both gave excellent analytical estimates of the experimental beam response.

This thesis presents a finite element (FE) modelling approach investigating the effects of corroded shear reinforcement on the capacity and behaviour of shear critical reinforced concrete (RC) beams. Shear reinforcement was modelled using a “locally smeared” approach, wherein the shear reinforcement is smeared within a series of plane-stress concrete elements at the specific stirrup location. This was done with the objective of incorporating both the reduction in cross-sectional area due to corrosion and the corresponding expansion of corrosion products build up. Corrosion damage was incorporated through equivalent straining induced by the corrosion build up on the affected surrounding concrete where the concrete cover was treated as a thick-wall cylinder subjected to internal pressure. Strains were introduced in the FE model using fictitious smeared horizontal pre-stressing steel, with a compressive pre-straining level related to the degree of corrosion penetration of the reinforcement. The FE modelling approach was first validated against published test data of shear critical RC beams with and without stirrup corrosion. The proposed modelling approach successfully reproduces the load deformation response as well as the failure mode and cracking patterns of the published experimental tests. Upon validation of the FE model, the work was extended to a parametric analysis of important shear design variables, such as the shear span-to-depth ratio, beam width and stirrup spacing The FE analyses were carried out for three increasing levels of corrosion (low, moderate and high) applied to affected stirrups within the critical section of the beams and based on steel mass loss (10%, 30% and 50%, respectively). In general, the results show a reduction in load carrying capacity accompanied by a softening of the load-deformation curves with each increasing level of corrosion. In most of the cases, a reduction in deflection associated to peak loads was also observed for moderate and high levels of corrosion. The impact of the various parameters was studied with respect to strength and deformation, as well as crack angle and mid-height horizontal strain. This was done in an effort to compare FE values to those provided by the CSA A23.3 design equations. The CSA A23.3 shear design equations were compared against FE analysis data in terms of residual shear strength estimation and individual component contributions to shear resistance (i.e., concrete and steel). The comparisons revealed an over conservative estimation for both strength and concrete contributions and an overestimation of the steel contribution. This divergence was attributed to a transition in shear behaviour within the critical section. Based on the progression of the concrete compressive struts with increasing corrosion and predicted crack angle, it was found that stresses in affected sections are redistributed towards adjacent undamaged material. The shear resistance mechanism generally transitioned from typical beam behaviour towards an arching-dominated one. Finally, based on important findings from the literature and the work conducted within this research, important considerations for assessment practice are suggested.

This dissertation reports investigations on shear in cracked reinforced concrete (RC) elements including the development and implementation of a material subroutine for the commercial finite element (FE) program ABAQUS. The material subroutine UMAT is intended to substantially improve the shear behaviour of the standard concrete options of ABAQUS. At first the important shear theories are reviewed in detail and their advantages and drawbacks are summarised. The modified compression field theory (MCFT) is identified as a suitable shear theory worth being coded for its application in FE analysis. A comprehensive check on the MCFT confirms its suitability in a slightly modified form for the investigation of a variety of cracked structural RC elements. This check is conducted on a section analysis level by means of a developed program called LAYER which is coded according to the MCFT. The main part of the work is the implementation and testing of the material subroutine UMAT which is added to the source code of ABAQUS via an interface provided by the commercial FE program. Finally, the UMAT is utilised for examining the ductility of RC walls. It is concluded that shear deflections can influence the displacement and curvature ductility of squat structures in a substantial way, even though a flexural type of failure might prevail.

No description available.

Rational decisions about cost-effecctive bridge designs, optimum inspection strategies and repair are hampered by the absence of comprehensive data on the mechanical performance of deteriorated concrete elements. One of the most important causes of concrete deterioration is corrosion of the steel reinforcement. In general corrosion of reinforcement is believed to affect the structural performance of concrete elements in two ways. First, by increasing the stress concentration on the rebar cross section, due to corrosion-induced reduction in the rebar cross-sectional area, which may lead to premature failure if the stresses in the rebar exceeds its yield strength. Second, by weakening the transmission of stresses in the composite resulting from the loss of bond strength between concrete and the steel reinforcement and the growth of cracks due to the formation of corrosion products at concrete/reinforcement interface. As part of a 'Brite Euram' Project, sponsored by the E.E.C., the author has developed procedures for assessing the influence of reinforcement corrosion on the structural performance of reinforced concrete flexural members. The experimental work was carried out on reinforced concrete beams which were subjected to accelerated reinforcement corrosion and then tested in flexure. Corrosion was induced in reinforcement by means of two external power supplies. The results obtained from the experiments show that reinforcement corrosion reduced the stiffness and the load carrying capacity of concrete beams significantly. Structural analysis and reliability analysis techniques were applied to the results of the study, and simple models for predicting the flexural load capacity of corroded beams were produced. The effect of reinforcement corrosion on the bond strength at the steel/concrete interface was also investigated. The results of the study provide evidence to indicate a trend of increased bond strength associated with small degrees of corrosion in reinforcement (≤0.4% reduction in rebar diameter).

No description available.

Reinforced concrete structures are usually vulnerable to collapse in areas where the earthquakes are frequent. Although plenty of research has been carried out in that regard the problem is still in place. Furthermore, there are buildings that did not collapse with the first and second earthquake but with the third one. That happens because many buildings are generally declared safe after being thoroughly inspected in the visible areas only, ignoring the extent of the damage in the column-to-foundation connections. The criterion of identifying the failure at the base of the columns of the ground floor is that after the earthquake there are no traces of failure. In other words, the cracks at the base of the columns have been healed and concealed the damage in the core of the columns. / Thesis (PhDCivilEngineering)--University of South Australia, 2005.

Errata pasted onto front end-paper. / Includes bibliographical references. / xv, 593 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Studies the peeling mechanism in plated beams and develops analytical procedures to quantify the shear peeling strength of steel plated beams.. / Thesis (Ph.D.)--University of Adelaide, Dept. of Civil and Environmental Engineering, 2000

Title page, abstract and table of contents only. The complete thesis in print form is available from the University of Adelaide Library. / The major contribution of this thesis is towards the shear capacity and shear failure mechanism of reinforced concrete beams with adhesively bonded transverse near surface mounted fiber reinforced plastic plates. In shear strengthening, there are two forms of plate debonding that interact with each other consisting of intermediate crack debonding that is governed by the axial forces in the plate are induced by shear deformations. This research considers both forms of debonding and in particularl their interaction. -- From abstract. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1283733 / Thesis (Ph.D.) -- University of Adelaide, School of Civil and Environmental Engineering, 2007