Salvatore Fragomeni

Ultimate Load Formula for Reinforced Concrete Wall Panels with Openings

Reinforced concrete walls with openings are tested in both one-way and two-way action. The test panels, with a slenderness ratio of 30 or 40, were subjected to a uniformly distributed axial load with an eccentricity of tw/6. Apart from highlighting the experimental set-up; typical crack patterns, failure modes, and load-deflection behaviour are also reported. Utilising these and other published test results, a formula predicting the ultimate load of walls with openings was derived. A comparative study of predicted to test results indicates that the new formula is accurate and reliable.

Evaluation of experimental work on concrete walls in one and two-way action

Abstract Currently, the design of reinforced concrete wall panels under eccentric axial loading only is carried out using empirical or semi-empirical methods. These methods involve approximations, which are not always reliable and being empirical, their scope of application is limited. In particular walls supported on all sides (i.e. two-way action behaviour), made of high strength concrete strength or high slenderness ratios have been given little treatment in research. In view of this, the authors have undertaken an extensive investigation on the development of a more reliable and accurate wall design equation. This paper initially presents a brief overview of an experimental program undertaken. The experimental results are compared to the proposed design equation. Also the proposed design equation is compared to results from previous studies on this topic, confirming that the new equation is accurate and reliable.

The Damping Analysis of Experimental Concrete Beams under Free-Vibration:

This paper presents an overview of the free-vibration damping analysis technique commonly employed by laboratories to determine the amount of material damping contained by a concrete specimen. From laboratory investigations the difficulties associated with a technique often employed for the extraction of damping from the free-vibration decay curve are identified. Extensive free-vibration tests undertaken on a wide variety of concrete beams indicate that for the traditional logdec technique, damping is to be extracted from the optimal peak ratio (An/A1) region of the free-vibration decay curve. An analysis of the effect of experimental test variables; hammer weight and hammer excitation position, on the calculation of damping is undertaken. The results show that neither test variable produces measurable impact on the calculation of damping.

Damping Formulae for Reinforced and Partially Prestressed Concrete Beams

A full-size test program was carried out on 26 simply-supported and continuous reinforced and partially prestressed concrete beams to study the cracking behaviour and damping characteristics of concrete beams. The beams were subjected to free vibration tests and logarithmic decrement values corresponding to each load level were measured. Separate regression analyses on the reinforced and the partially prestressed beams were undertaken. These analyses resulted in two separate empirical formulae for predicting the logarithmic decrement of damping in reinforced and in partially prestressed beams. Comparison with test results from all 26 beams indicates that the predictions are accurate. It is also found that the damping formula for reinforced beams is applicable to both single and continuous spans. The proposed damping formulae predict damping from the residual crack widths of the beams. As such, formulae developed for predicting residual crack widths from given variables defining the beams and their deflection-span ratios are also reported.

PRELIMINARY ANALYSIS OF NORMAL STRENGTH CONCRETE WALLS WITH OPENINGS USING LAYERED FINITE ELEMENT METHOD

A nonlinear Layered Finite Element Method (LFEM) is applied to investigate the structural behaviour of reinforced concrete walls with openings. Four half-scale concrete walls with openings, tested recently in the laboratory, are analysed. The test variables are the wall slenderness ratio and the size and location of openings. The walls are axially loaded at an eccentricity of one-sixth of the wall thickness. The ultimate loads, the load–deflection responses and the crack patterns predicted by the LFEM are compared with the experimental results. The comparison shows that the LFEM is effective and accurate.

Corbel Design Chart for 20-100 MPa Concrete

Abstract This paper utilises the strut and tie method, recommended in the AS3600–2001 concrete structures code1 to develep a corbel design chart for 20 to 100MPa concrete. The method encompasses a trial and error procedure to determine the amount of tension reinforcement required in a corbel to resist the anticipated loading. Relevant design constraints from various major design codes are highlighted and a modified efficiency factor is used to enable the chart to be used for concrete strengths up to 100MPa. The results of recent research are used to ascertain the adequacy of the design charts developed. The chart provides a useful tool for designers by eliminating the need for an iterative design procedure, enabling the direct design of concrete corbels to take place.

Experimental and numerical study for the shaping formation of SCST structures by cable-tensioning

This paper discusses the behaviour characteristics of the shaping formation of Single-Chorded Space Truss (SCST) structures by means of cable-tensioning of bottom chords. The innovative technique is fast and economical and issued in many types of space structures. The small-scale test models presented herein consist of uniform pyramids with multi-directional ball type joints which are erected into their final shape by cable-tensioning. Since the joint behaviour is very significant in studying the shaping of SCST structures, basic tests for beam and pyramidal units were performed. The feasibility of the proposed cable-tensioning technique and the reliability of the established geometric model were con- firmed by finite element analysis. The proposed cable-tensioning technique indicates that the behaviour characteristic of joints is very important in the shaping formation of SCST structures. More specifically in situations where heavy cranes are inaccessible, the cable-tensioning construction technique has proven to be an easy and reasonable method compared to conventional construction methods that typically include heavy cranes and scaffolding.

Asian Concrete Model Code (ACMC) and Australian Concrete Structures Standard (AS3600) Compared

Abstract The first ever Asian Concrete Model Code (ACMC 2001) has recently been published and prepared by an international committee, drawn from various Asian countries including Australia. This paper serves to introduce the Model code by providing an evaluation of its contents and brief history of its origins. Co-incidentally, Standards Australia has also recently released the latest version of the Australian Concrete Structures Standard, AS3600–2001. The contents of AS3600 are also discussed briefly. The paper will then focus on comparisons between the new ACMC and the well-established AS3600. The comparisons are made on philosophical and general grounds, and in some instances more direct comparisons are made.