DA Nethercot | Imperial College London (original) (raw)

Papers by DA Nethercot

The design of slender beams is frequently controlled by the tendency of the beams to buckle later... more The design of slender beams is frequently controlled by the tendency of the beams to buckle laterally. This paper examines the effect which various types of semi rigid bracing have in stabilizing beams against lateral buckling. Theoretical relationships,dealing with both discrete and continuous restraints, are presented which enable a designer to determine the buckling load of beams stabilized by restraints possessing both lateral and torsional stiffness. It is shown that the method of attachment is of particular importance when dealing with bracing designed to provide a torsional restraint. Good correlation is obtained between these theoretical results and the results of an experimental study which has been conducted to examine the effectiveness of corrugated sheeting as a stabilizing medium. 1.

A series of tests designed to investigate the interaction of a variety of different steel beam to... more A series of tests designed to investigate the interaction of a variety of different steel beam to column connection details with a composite metal deck floor is described. The main emphasis is on assessing the connections' moment capacity, rotational stiffness and rotation capacity. The full details of the experimental behaviour of the flush end plate and partial depth end plate connections will be described in this paper. A simple method for moment capacity calculation based on the test results is proposed herein.

Analysis and Design of Plated Structures, 2022

The Journal of Strain Analysis for Engineering Design, 1991

... Minor axis moment: My, = E*Zyy* (-El + E2 + E3 - E4) 4 EZ, . 4 Warping bi-moment : B = -(-El ... more ... Minor axis moment: My, = E*Zyy* (-El + E2 + E3 - E4) 4 EZ, . 4 Warping bi-moment : B = -(-El +82 - 83 + 84) where el, t2, c3, and e4 represent the total strains at the four comers due to the individual load components. 81 = &a + Eb + 8, + Ed 82 = 8, + Eb - &c + Ed ...

Journal of Constructional Steel Research, 2009

This paper presents a generalised component-based model for semi-rigid beam-tocolumn connections ... more This paper presents a generalised component-based model for semi-rigid beam-tocolumn connections including the axial force versus bending moment interaction. The detailed formulation of the proposed analytical model is fully described in this paper, as well as all the analytical expressions used to evaluate the model properties. This paper also illustrates detailed examples of how to use this model to predict moment-rotation curves for any axial force level, the numerical results that were generated and validated against experimental tests, and a tri-linear approach to characterise the forcedisplacement relationship of the joint components. A bibliographical review containing a brief description of the most important available techniques to predict the joint structural behaviour, using mechanical models, and some experimental tests is also presented.

Journal of Constructional Steel Research, 2006

The appropriate use of special metals such as stainless steels (SSs) for structural applications ... more The appropriate use of special metals such as stainless steels (SSs) for structural applications in building systems provides possibilities for a more efficient balance between whole-life costs and in-service performance. The present paper assesses the feasibility of the application of SSs for seismic retrofitting of framed structures, either braced (CBFs) or moment resisting (MRFs) frames. In so doing, inelastic analyses have been carried out on a set of multi-storey CBFs and MRFs. The results of both inelastic static (pushovers) and dynamic (response history) analyses demonstrate that systems retrofitted with SSs exhibit enhanced plastic deformations and excellent energy absorbing capacity. The augmented strain hardening of SS is beneficial in preventing local buckling in steel members in both MRFs and CBFs. The analytical results also demonstrate that, when SS is spread within columns, the system over-strength increases by 30% with respect to the carbon-steel benchmark structure. The design over-strength, plastic redistribution and energy dissipation capacity increase by the same amount.

Journal of Constructional Steel Research, 2004

Basic material properties and cross-sectional data (stress-strain curves and load-end shortening ... more Basic material properties and cross-sectional data (stress-strain curves and load-end shortening curves) are presented for square, rectangular and circular hollow section specimens in Grade 1.4301 stainless steel. The material tests cover flat material in tension and in compression as well as corner material in tension. Modifications to the Ramberg-Osgood representation are suggested to ensure a close fit to both tensile and compressive behaviour over the full range of strains of interest. Results, including full load-end shortening curves, for a total of 37 stub column tests have been presented. The results have been used to develop an explicit relationship between cross-sectional slenderness and cross-sectional deformation capacity, which forms the basis for a proposed new design approach for stainless steel structures.

Journal of Constructional Steel Research, 2003

Many existing steel multi-storey frames in Europe were designed prior to the provisions of modern... more Many existing steel multi-storey frames in Europe were designed prior to the provisions of modern seismic design codes; therefore, they often exhibit low resistance to earthquakes due to their insufficient energy dissipation capacity. However, the current framework for assessing existing structures in EC8-3 is inadequate and should be reviewed. Particular attention should be paid to the contribution from masonry infill walls as they significantly affect the modal properties and the lateral stiffness of structures. To this end, two 3D models of a two-storey steel moment-resisting frame were developed to assess the applicability of the current framework in EC8-3 to the infilled structures under multiple earthquakes through nonlinear analyses. The modelling of masonry infill walls was achieved through a macro-model using equivalent diagonal struts. The ground motions utilised during the analyses took the records of the recent 2016 Central Italy earthquake sequence. As part of the project HITFRAMES, this paper serves as a preparation for the experiment to be conducted in Greece.

Structural sections manufactured from stainless steel possess several features that mean that the... more Structural sections manufactured from stainless steel possess several features that mean that their response to loading differs from that of equivalent members made from carbon steel. To date these features have not really been recognised in design codes, which have largely adapted rules devised for carbon steel in a rather simplistic fashion. Recently, a new approach for dealing with local buckling and the associated loss of effectiveness that does not utilise the concepts of either cross-sectional classification or effective cross-sectional properties has been developed; it is therefore particularly well suited to dealing with stainless steel. Originally the concept was restricted in application to closed sections. It is extended herein to cover both open and closed cross-sections. It is then incorporated in the procedures for designing columns and beam-columns based on the Eurocode approaches and it is shown that by making further modifications the accuracy of these methods can be significantly improved. The resulting design procedures are no lengthier than those currently given in the stainless steel part of EC3.

Structural Engineering International, 1997

Genocide, crimes against humanity and war crimes are among the most serious categories of crimes ... more Genocide, crimes against humanity and war crimes are among the most serious categories of crimes known to international law. For decades lawyers and others debated whether a standing international court should be established to prosecute and punish such crimes. In 1998 the debate ended with the adoption of the Rome Statute for the establishment of an International Criminal Court (ICC). The Statute defines the elements of each of these crimes and includes them in the ICC's jurisdiction. The idea of including "grave crimes of international terrorism" as an additional category in the ICC's jurisdiction was considered, but abandoned as too difficult. Firstly, there is at present no universally agreed definition of terrorism and the whole subject is politically sensitive. Secondly, democratic and other States have long recognised that certain acts that would ordinarily be considered criminal should be treated differently if they can be characterised as "political offences". This paper argues that both these difficulties can be overcome. A solution to the problem of definition is to confine "terrorism" to those acts that are outlawed by existing anti-terrorist multilateral conventions, as listed by the UN, at least to the extent that those conventions are declaratory of customary international law. It is also argued that the "political offence" issue has been rendered obsolete by the creation of the ICC, with its numerous safeguards to ensure the Court's impartiality. In 2009 the Rome Statute will be reviewed and there will be an opportunity to expand the ICC's jurisdiction to include grave crimes of international terrorism. For the international rule of law to be supported and strengthened, that opportunity should not be missed.

As part of an extensive experimental study into the influence of semi-rigid connections on the be... more As part of an extensive experimental study into the influence of semi-rigid connections on the behaviour of steel columns, a measurement device has been developed which permits the six individual components of three-dimensional deformation to be monitored. The theory used to process the measured deformations and the subsequent testing of a prototype device is described. A comparison between the deformations measured using the device, and those predicted using a column sub-assemblage finite element model is also presented. 1

The companion paper presents the principles of a new design-oriented methodology for progressive ... more The companion paper presents the principles of a new design-oriented methodology for progressive collapse assessment of multi-storey buildings. The proposed procedure, which can be implemented at various levels of structural idealisation, determines ductility demand and supply in assessing the potential for progressive collapse initiated by instantaneous loss of a vertical support member. This paper demonstrates the applicability of the proposed approach by means of a case study, which considers sudden removal of a ground floor column in a typical steel-framed composite building. In line with current progressive collapse guidelines for buildings with a relatively simple and repetitive layout, the two principal scenarios investigated include removal of a peripheral column and a corner column. The study shows that such structures can be prone to progressive collapse, especially due to failure of the internal secondary beam support joints to safely transfer the gravity loads to the sur...

A simplified framework is proposed for progressive collapse assessment of multi-storey buildings,... more A simplified framework is proposed for progressive collapse assessment of multi-storey buildings, considering sudden column loss as a design scenario. This framework can be applied at various levels of structural idealisation, and enables the quantification of structural robustness taking into account the combined influences of redundancy, ductility and energy absorption. Three main stages are involved in the proposed approach: i) determination of the nonlinear static response, ii) dynamic assessment using a novel simplified approach based on energy conservation, and iii) ductility assessment at the maximum dynamic deformed configuration. The application of the proposed method is illustrated on a multi-storey steel-framed composite building, where the relative importance of various joint details and levels of axial restraint is highlighted. Importantly, the study underlines the inadequacy of prescriptive tying force requirements that neglect ductility issues, and demonstrates that t...

This paper focuses on the role of the IT tools that have enabled the development of a decision su... more This paper focuses on the role of the IT tools that have enabled the development of a decision support system, the Integrated Design System (IDS). The IDS facilitates the derivation of production related designs for structural steelwork, by integrating the information flow from each of the existing processes. It will enable the designer to investigate the effects of conceptual decisions on fabrication, transportation, and erection costs, and assess the constructability of designs, providing advice on feasible and economic alternatives. This has beneficial implications for the overall economy and constructability of the finished design.

ABSTRACT: Drawing on over 30 years of personal involvement with the preparation of codes of pract... more ABSTRACT: Drawing on over 30 years of personal involvement with the preparation of codes of practice for structural steel design, the issue of academic elegance versus practitioner practicality is discussed. Several examples taken from recently produced codes are used to illustrate different manifestations of the issue. The matter is discussed within the wider context of both the growing internationalisation of codes and the substantial supporting infrastructure needed by designers to efficiently implement their provisions. Although the specifics relate largely to the design of steel buildings in the UK and the wider European context, it is thought that the points stated, lessons learned and recommendations made are of general relevance.

Composite Construction in Steel and Concrete IV

A procedure is presented for checking that composite beams and frames designed according to the p... more A procedure is presented for checking that composite beams and frames designed according to the principles of semi-continuous construction possess sufficient ductility to ensure that the presumed pattern of moments at the ultimate limit state design condition is achieved. The procedure provides for this in terms of the available and required inelastic rotations at each notional plastic hinge in the system as devised by detailed evaluations of numerous previous studies of the subject area.

Steel construction today, 1991

The Structural engineer, 1975

The influence of the conditions of loading and lateral support on the inelastic lateral buckling ... more The influence of the conditions of loading and lateral support on the inelastic lateral buckling of rolled steel beams is studied using a finite element approach. The numerical results obtained are subsequently used to assess the accuracy of simplified methods of allowing for these factors. Changes in the form of the applied loading are found to affect the critical moment much less in the inelastic range than in the elastic range and it is therefore suggested that the use of an effective length approach provides the most appropriate method of dealing with such factors. (A) /TRRL/