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To develop a non-bearing prefabricated straw sandwich concrete wallboard (I-beam beetle elytron plate: IBEPsc), the effect of certain structural parameters (e.g. panel thickness, T, number of I-cores, N, and core height, h) on mechanical and thermal insulation performance was investigated using the finite-element method, with the following results. (a) Bearing capacity of the IBEPsc is controlled by the maximum principal tensile stress; the optimal structural parameters of the IBEPsc for a self-insulated wall with a large safety margin are presented. (b) The consideration of strips as opposed to whole plates and the selected upper bearing constraint type have little influence on the mechanical properties. In practical applications, the strips and whole plates can be reasonably selected according to engineering needs, and these components can be connected with the main structure by conventional mortar. (c) According to qualitative analysis and comparison with common I-shaped thermal insulation walls, the IBEPsc requires the least material and weight while ensuring a sufficient safety margin in terms of mechanical and thermal insulation performance. Hence, biomimetic techniques can play a key role in breaking through the limitations of traditional structures. This paper can help direct the application of beetle elytron plates in prefabricated wallboards. [ABSTRACT FROM AUTHOR]

One approach to reducing embodied carbon dioxide of buildings is the increased use of plant-based construction materials such as prefabricated straw bale panels. This paper presents findings from the development and structural testing of an innovative load-bearing prefabricated straw bale building. Work on panel development is summarised ahead of presenting two numerical computer-based models that support the building design. The computer models are validated using data from a full-scale simulated static wind load test on a two-storey building. The prefabricated straw bale structural system is shown to be suitable for two- and three-storey domestic structures in a range of locations. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) design is in a state of perpetual revision of ever-increasing complexity. However, preventing the recurrence of unexpected types of brittle failure is yet to be achieved. It is argued that the causes of such types of failure reflect conflicts between assumed and actual behaviour of concrete at both material and structural levels. This paper presents available information on the fundamental properties of concrete, which current design assumptions are incompatible with, and points towards the work required for really improving RC design. [ABSTRACT FROM AUTHOR]

This paper considers the problem of human acceptance of vibration in grandstands. It adopts the BS frequency weighting methodology and uses the vibration dose value (VDV) as an indication of when adverse comments may be expected. Measurements were taken on a number of cantilever grandstands during concerts and football matches. These were analysed to determine peak accelerations and VDVs and some empirical relationships were derived. As human reaction at these events relates more to vibration tolerance than perception, it has been necessary to consider a logical extrapolation based on current BS guidance to suggest VDVs that are appropriate for grandstand vibration. The reactions and VDVs recorded on the grandstands appear to support this suggestion. The calculation of VDVs is also considered, but this depends to a great extent on the calculation of peak accelerations, which is considered in another paper. Finally a number of key points arising from this work are discussed. [ABSTRACT FROM AUTHOR]

Presents the author's comments on a paper related to constructions. Criteria for loading slabs during construction; Interpretation of data from the Cardington building case; Deflections of real slabs under real loads.

Presents the author's comments on the paper that presented the results of the full-scale fire test carried out in Cardington. Damage of the first floor slab of the building beyond repair; Assessment of the damage caused by a severe fire on a reinforced concrete building under construction in the Middle East; Aggregate used on the building under construction.

This paper offers practical guidance to engineers using finite-element analysis software packages for the design of modern glass structures. The target audience is structural engineers with a knowledge of typical structural materials but who are less experienced in glass. The principles of typical modelling procedures are discussed, and the specific techniques of sub-modelling and sub-structuring are introduced. Issues that are particular to the behaviour of statically loaded structural glass are addressed, including interaction with supporting structure, evaluating composite action in laminates and lateral buckling of slender elements. The primarily academic, more advanced modelling techniques of adaptive meshing, rezoning, using birth and death elements, and probabilistic analysis are introduced. The potential power of these techniques in the field of structural glass is presented. Finally, suggested methods for result verification are presented. These include both pre-processor and post-processor methods. Real project examples are used to illustrate discussion points throughout the paper. [ABSTRACT FROM AUTHOR]

Most types of infills cannot be regarded as engineered elements, especially owing to the lack of sufficient ductility, and they are normally ignored in the analysis of structures. Recently a new type of infill has been proposed that has a frictional fuse at the mid-height. High ductility and strength of such infills have been confirmed through experimental studies. A formula is proposed in this paper for the ultimate strength of the fused infilled frame, based on finite-element analyses, verified by experimental data, depending on the material properties, dimensions of the frame and infill and the fuse sliding strength. The infill can be applied in newly designed or rehabilitated buildings. Such buildings can easily conform to the new version of codes, with more restricting criteria for seismic design, by regulating the infills for higher strengths, estimated by the proposed formula presented in this paper. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation into the behaviour of high-strength steel (HSS) structures (i.e. yield strength between 460 and 700 N/mm2) in fire conditions. The paper proceeds with a description of the experimental programme that includes two different grades of HSS with the aim of assessing ( a) the mechanical properties at elevated temperature through tensile testing and ( b) the effect of chemical composition and processing route on the microstructure through a detailed metallurgical investigation. The investigation takes a holistic view of the analysis whereby the effect of processing route and composition on the microstructure and hence mechanical properties are assessed. In this paper, following a detailed description of the tests under isothermal conditions, the results are analysed to determine strength and stiffness reduction factors at elevated temperatures and these values are compared with the literature and design standards. [ABSTRACT FROM AUTHOR]

The poor durability of ordinary Portland cement concrete and the corrosion of conventional steel reinforcement have a major impact on the viability, safety and serviceability of reinforced concrete structures, particularly in marine environments. Geopolymer concrete (GPC) reinforced with corrosion-free glass-fibre-reinforced polymer bars is ideal for projects such as bridge piers in coastal zones where corrosion is severe. This paper reports on an examination into the behaviour of this novel construction material under axial, combined and flexural loading and validation of a numerical model of the material. To this end, 11 GPC specimens constructed with various stirrup spacings were subjected to a range of loading conditions. The concrete was modelled using the widely used concrete damage plasticity model and linear elastic behaviour was used for the fibreglass bars and stirrups. The predicted axial load–deflection responses were in close agreement with the experimental data, especially for concentrically loaded columns. The load capacities of eccentrically loaded columns and beams were slightly overpredicted by the model due to a tendency of the fibreglass stirrups to open up prematurely. [ABSTRACT FROM AUTHOR]

For decades bamboo has been identified as one of the most promising alternatives to help reduce the rising demand for industrialised building materials in the global south but numerous technical, normative and cultural challenges have so far prevented its widespread use in construction. In response, significant resources are currently being invested in the development of standardised, highly processed structural bamboo components following the unsustainable model of mass industrialisation prevalent in the global north. As a counterpoint, this research re-examines the structural use of natural bamboo culms against the backdrop of the digital age and postulates a new design and fabrication framework to support the construction of high-quality, sustainable and resilient bamboo structures suitable for the twenty-first century. This framework is based on the principles of building information modelling and is focused on managing, as opposed to forcibly eliminating, the inherent variability of a natural structural element through modern three-dimensional scanning, digital modelling and robotic fabrication. This paper presents the conceptual details of this framework with a particular focus on Mexico, one of the largest emergent economies in the world, as a potential implementation platform. [ABSTRACT FROM AUTHOR]

Both the flexural and shear strengths of reinforced concrete (RC) beams can be substantially increased using externally bonded fibre-reinforced polymer (FRP) reinforcement in the forms of sheets/strips/plates (all referred to as plates for brevity). Failures of such FRP-plated RC beams often occur by debonding of the FRP plate from the RC beam in a number of distinct modes. This paper provides a summary of the current understanding of the mechanics of debonding failures in FRP-plated RC beams largely based on the research of the authors and their co-workers. A systematic classification of possible debonding failure modes is presented following a brief outline of the common strengthening methods. The interfacial stresses and bond behaviour between FRP and concrete are then discussed before the mechanisms and processes of debonding failures are examined. Furthermore, advanced strength models for the key debonding failure modes are presented. The paper concludes with a brief discussion of future research needs. [ABSTRACT FROM AUTHOR]

Circumferential confinement of reinforced concrete columns with externally bonded fibre-reinforced polymer (FRP) wraps is now widely implemented as a method to strengthen and/or enhance the deformability of deficient or damaged reinforced concrete columns. A fundamentally important parameter in the design of these members is the so-called strain efficiency of the FRP wraps - the ratio of the tensile hoop strain in the FRP at failure to the average failure strain observed in direct uniaxial tensile coupon tests. Available experimental hoop strain data obtained using localised strain gauges provide little insight into the variation of hoop strain over the surface of FRP wraps, the factors influencing strain efficiency and the resulting strain efficiency that should be assumed in design, and these remain essentially unknown. In this paper, a novel digital image correlation technique is used to provide a detailed experimental quantification of the axial and hoop strain variation over the surface of FRP confined concrete cylinders. Potential implications for the analysis and design of FRP confined concrete are discussed. [ABSTRACT FROM AUTHOR]

The aim of this paper is to stimulate a wider interest in the built heritage of industrial Britain amongst civil engineers. Britain has a greater number and variety of iron roofs than found anywhere else in the world. From the tentative iron roofs over the attic workrooms of the first iron-framed factories, this paper traces the development of greater spans using arch and truss forms to meet the needs of a diverse range of building types, among which the railway station passenger train shed is most significant. The confused issue of design and construction responsibilities for some of the great roofs of the nineteenth century is partially unravelled. The paper shows how innovations in iron roofing were at first introduced by a handful of structural ironwork contractors, further advances being made by a small group of specialist engineers expert in the analysis, design and detailing of structural works in iron. [ABSTRACT FROM AUTHOR]

This paper describes some yield line collapse patterns for interior flat slab panels supported on a parallelogram column grid. These patterns were used to analyse six model slabs tested at the Cambridge University Engineering Department as part of ongoing research. Further confirmation of the failure modes was obtained from observed changes in deflection at the final stages of loading, from crack patterns, and from readings from strain gauges stuck on reinforcement bars. For the experimental slabs, the calculations were done using the work equation. In this paper it is demonstrated that by drawing a few yield line patterns on a reinforcement detail drawing, and sketching the corresponding hodographs, ultimate load calculations can be performed on a piece of paper or a spreadsheet. Predictions from such calculations are accurate enough to avoid over- design and save valuable time and effort in assessing the ultimate collapse load for flat slabs supported on a non-rectangular column grid. [ABSTRACT FROM AUTHOR]

Fibre-reinforced polymers (FRPs) have found increasing use in construction applications over the last four decades. One of the key factors in their success is the long-term durability they offer. Structures erected in the late 1960s and early 1970s are still meeting performance requirements, and several examples of these are cited in this paper. Improvements in materials technology mean that the properties of FRP components produced today are at least as good as, if not much improved on, those available 40 years ago. This, along with the need for improved construction processes, suggests an increase in the application of FRP materials in construction in the future. The work reported in this paper forms part of a much larger site investigation project, funded through the UK's Department of Trade and Industry, covering many types of application of composites in construction. The results reported here confirm that modern durable FRP structures can be designed and constructed. [ABSTRACT FROM AUTHOR]

Fibre-reinforced self-compacting concrete (FRSCC) is a high-performance building material that combines the positive aspects of the fresh properties of self-compacting concrete (SCC) with the improved characteristics of hardened concrete as a result of fibre addition. To produce SCC, either the constituent materials or the corresponding mix proportions may notably differ from conventional concrete (CC). Therefore, it is vital to investigate whether all the assumed hypotheses about CC are also valid for SCC structures. This paper reports a study in which eight SCC and FRSCC slabs of similar cross-section were monitored under service loads for up to 240 d. The recorded time-dependent cracking and deflections are presented. The steel strains within the high-moment regions, the concrete surface strains at the tensile steel level, deflection at the mid-span, crack widths and crack spacing were recorded throughout the testing period. The experimental results show that the instantaneous crack widths and spacings for the normal SCC slab series were close to and much less than, respectively, the corresponding variables for the normal CC slab series. [ABSTRACT FROM AUTHOR]

One approach to reducing embodied carbon dioxide of buildings is the increased use of plant-based construction materials such as prefabricated straw bale panels. This paper presents findings from the development and structural testing of an innovative load-bearing prefabricated straw bale building. Work on panel development is summarised ahead of presenting two numerical computer-based models that support the building design. The computer models are validated using data from a full-scale simulated static wind load test on a two-storey building. The prefabricated straw bale structural system is shown to be suitable for two- and three-storey domestic structures in a range of locations. [ABSTRACT FROM AUTHOR]

Concrete structures suffer from corrosion if chloride ions in the environment penetrate to the depth of reinforcing steel; surfaces periodically wetted with chloride solution are at most risk, when chloride ions can enter concrete by combined diffusion and absorption. BS8500-1 recommended minimum cover requirements primarily assume that chloride ingress is diffusion controlled, and absorption is only partly accounted for, so cover values may be inadequate. This paper investigates factors that influence absorption of chloride ions into concrete and how this affects distribution of chloride at different depths from the surface. Concrete cubes (CEM I cement; water/cement ratio 0·45) are subjected to repeated wetting (with 50% saturated salt solution) and drying cycles, during which their mass is monitored. The effective porosity, weight and distance sorptivity and chloride penetration depths are calculated for a number of curing, conditioning and drying conditions. Samples are extracted from the cubes at a range of depths and analysed for chloride content. Results show that the quantity of chloride entering the concrete, and in particular surface chloride content, is very sensitive to effective porosity/drying conditions immediately before wetting; also as much as 31% of the protection provided by concrete cover can be lost after exposure to just one wet/dry cycle, thereby significantly reducing time to corrosion of concrete structures. [ABSTRACT FROM AUTHOR]

Structures, systems and components that are essential for the safe operation and shutdown of a nuclear power plant may be subject to a variety of impulsive loads. This paper presents an experimental and numerical evaluation of the influence of ground shock and airblast forces on the structural response of a 1:8 scale reactor containment structure founded on schist. The numerical model, including both free air and schist properties, was programmed and linked to finite-element software as its user-provided subroutines. The numerical and experimental scaled model results demonstrate good agreement with each other. The full-scale simulation of typical reactor containment was subjected to surface explosions through the developed relationship for structural response analysis. The proposed methodology can be employed to evaluate the blast response of a concrete shell type containment structure and to estimate the integrity of containment. [ABSTRACT FROM AUTHOR]

The trend of adopting architectural designs with irregularities in elevation, meaning that the shape of the building is irregular, is on the increase. Seismically deficient structures are found in abundance in developing countries such as Pakistan, and structures with irregularities in elevation may result in failures due to sudden changes in stiffness, mass or strength along the building height. The aim of the work reported in this paper was to develop analytical seismic vulnerability curves for deficient mid-rise reinforced concrete building frames with setbacks. The vulnerability curves were derived by adopting a framework used in a previous study. Along with a regular frame, six-storey frames with different setback configurations were considered. The frames were modelled using the numerical analysis program Drain-3DX and their responses were estimated by generating force–displacement envelopes using non-linear static analysis. The response spectrum of the Uniform Building Code was used to impose a seismic demand. The hazard levels were evaluated at every point of the capacity envelope using a reverse procedure of Fema 440. The damage in the studied building frames was quantified through a direct correlation with the natural period of vibration of the buildings, as suggested in previous studies. The developed vulnerability curves showed brittle failure modes in seismically deficient buildings. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental investigation to evaluate the contribution of carbon-fibre-reinforced polymer sheets in enhancing the shear strength of continuous reinforced concrete beams. A total of five, two-span concrete continuous beams with rectangular cross-section were tested. One beam without strengthening was used as the control and the other four beams were strengthened with different arrangements of polymer sheets. The variables selected were various wrapping schemes and anchorage length of the polymer sheet. The aim was to develop a better understanding of the shear contribution of polymer and to investigate the potential for cost savings by minimising the area of externally bonded polymer sheets. Test results were compared with four existing shear prediction models available in the literature. The results indicate that the polymer sheet significantly enhanced the shear strength of the beams, and that the area of polymer sheet can be minimised with marginal compromise on the shear carrying capacity of strengthened concrete beams. [ABSTRACT FROM AUTHOR]

The increasing awareness of the environmental impacts of construction materials has resulted in an increasing interest in earth masonry in the UK in recent years. The use of traditional vernacular techniques has raised the profile of earthen architecture but wider impact is likely to come from commercially produced, thin-walled, earth masonry as a replacement for blockwork, brickwork or timber-framed non-structural internal walls. Earth masonry is susceptible to changes in moisture, and this paper investigates the potential for early-age cracking from changes in moisture content during the most critical period for these materials, namely during construction. It is shown that internal stresses generated by moisture-driven expansion after rendering may exceed masonry flexural (flexure-induced tensile) capacity leading to premature wall failure. This failure mechanism was observed in a test panel and has potential to occur in real walls. Recommendations on how to minimise the risk of early-age cracking are presented. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical results of intermediate-scale and full-scale fire tests conducted on flexurally strengthened reinforced concrete members. Two full-scale reinforced concrete T-beams and two intermediate-scale slabs were strengthened in flexure with carbon fibre reinforced polymer sheets or plates and insulated with a layer of spray-on material. T-beams and slabs were then exposed to a standard fire. T-beams were loaded to their service load. Deflections and temperatures were measured during the tests. A numerical finite-difference/volume heat transfer model was used to simulate the temperature field inside the section. The validity of the numerical model was verified by comparing the predicted temperatures with those recorded during the fire test. Fire test results show that fire endurances of more than 4 h can be achieved using an appropriate insulation system. [ABSTRACT FROM AUTHOR]

Tubular construction is synonymous with modern architecture. The familiar range of tubular sections - square, rectangular and circular hollow sections - has been recently extended to include elliptical hollow sections (EHSs). Due to differing flexural rigidities about the two principal axes, these new sections combine the elegance of circular hollow sections with the improved structural efficiency in bending of rectangular hollow sections. Following the introduction of structural steel EHSs, a number of investigations into their structural response have been carried out. This paper presents a state-of-the-art review of recent research on EHSs together with a sample of practical applications. The paper addresses fundamental research on elastic local buckling and post-buckling, cross-section classification, response in shear, member instabilities, connections and the behaviour of concrete-filled EHSs. Details of full-scale testing and numerical modelling studies are described, and the generation of statistically validated structural design rules, suitable for incorporation into international design codes, is outlined. [ABSTRACT FROM AUTHOR]

Drystone walling is an ancient form of wall construction, used worldwide wherever there is an abundance of raw building materials. However, very little research has been conducted on these structures, making their analysis difficult. As part of an ongoing investigation, four full-scale drystone retaining walls were built and tested to failure in a bespoke outdoor test laboratory. Through the course of the testing, the distinctive bulge patterns that are found in many in situ walls were successfully recreated. This paper describes the set-up of the test laboratory and instrumentation used, in addition to the proceedings of each wall test. Initial findings of the project tests and a discussion regarding the underlying reasons behind bulging in drystone walls are presented. [ABSTRACT FROM AUTHOR]

This paper presents the results of an extensive programme of research carried out jointly at the University of Leeds and the University of Durham to clarify various aspects of cracking behaviour particularly in the tension zones of flexural members. The results show that concrete cover is the only parameter affecting the transfer length at load levels close to cracking and up to service load. An attempt has also been made to show the bond mechanism at the bar-concrete interface using the technique of ink injection. Unfortunately, this technique failed to reveal internal cracks between two major cracks when the stress in the reinforcement was increased up to approximately 200 MPa; whether this was attributed to their absence or to faults in the testing procedure was unclear. The current paper also proposes an empirical formula to predict the transfer length in slabs. The input data required are more simple and convenient to collect than using a crack width microscope and the predictions from the formula are just as accurate. [ABSTRACT FROM AUTHOR]

It is well established that tension stiffening, the contribution of the concrete in tension to the stiffness of a reinforced concrete member, is a significant parameter in deflection calculations and this is recognised by design codes such as BS 8110 and Eurocode 2. These codes make provision for tension stiffening effects and also distinguish between short- and long-term behaviour. What is not known, however, is how rapidly tension stiffening decays with time or how significant this rate of decay might be for deflection calculations. This paper reviews the current approaches to tension stiffening in BS 8110 and Eurocode 2 and then summarises a major experimental investigation which was undertaken to explore time dependent aspects. Revisions to BS 8110 and Eurocode 2 are proposed as a result of this work Further refinements for modelling tension stiffening effects in reinforced concrete members are also described. [ABSTRACT FROM AUTHOR]

The paper is devoted to the analysis of crack evolution of fibre-reinforced polymers (FRP) reinforced concrete tension members and, as a consequence, their deformability in terms of load-elongation relationships. Such analysis permits the determination of tension stiffening effects. The stiffness of the reinforced tension members, in fact, can be evaluated and compared to rebars whilst the scatter gives a measure of the reduced deformability due to the contribution of the tensile concrete. Results of an experimental investigation, carried out on cylindrical concrete specimens in order to analyse the influence of geometrical properties on cracking and deformability of the members, are reported in the paper. Comparisons with results obtained from a theoretical analysis and from code relationships are also made, aiming to give useful information from a design point of view. [ABSTRACT FROM AUTHOR]

This paper discusses the definition of, and the distinction between, deformability and ductility of reinforced concrete (RC) beams that are strengthened by advanced composites. The study examines the suitability of a new, design-based method for the determination of deformability, as well as an energy-based process, which is found to be suitable for quantifying the ductility levels of fibre-reinforced polymer (FRP)-strengthened RC members. Ten FRP-strengthened RC beams and four slabs have been load-tested to ultimate failure in the current study. The test results, together with the load-deflection data of an additional 26 beams from literature, form the basis of analyses and discussions. The paper concludes that high deformability does not necessarily lead to good ductility, as very brittle failure modes of such beams have been observed in the experimental studies and reported in literature. It was found that a ductility index of between 2.0 and 2.5 reflects 25-33% of elastic energy stored in the strengthened system. This level of elastic energy is considered to be the maximum acceptable in FRP-strengthened concrete flexural elements for ductile behaviour. It was also found that for ductile failure modes the deformability and ductility indices tend to converge, whereas for brittle behaviour the deformability index could be up to 33% higher. The results presented in this paper provide a rationale for the ductility considerations to be incorporated into the development of design equations for FRP strengthening. [ABSTRACT FROM AUTHOR]

The paper describes the development of a numerical model for analysis of beams retrofitted with external unbonded reinforcement. The experimental phase of the investigation is described in a companion paper, which also outlines the advantages of the method. Because external reinforcement is not bonded to the beam throughout its span, but is anchored only at the ends, normal plane section behaviour assumptions cannot be used. The numerical model is based on section analysis, and incorporates non-linear material behaviour and non-linear geometric effects. The model is first validated against results from an experimental programme comprising 35 physical tests on laboratory specimens. The model is then used to supplement the experimental study by exploring parameters which could not receive adequate experimental coverage. The influence of the shape of the bending moment diagram and of span/depth ratio, parameters which were not adequately explored in the experimental investigation, are reported. Deflectors were typically calculated to double strength enhancement at shorter span/depth ratios; the benefits were greater with higher ratios. Their use will be advantageous in the majority of situations. [ABSTRACT FROM AUTHOR]

In an earlier study the authors outlined a strengthening technique for reinforced concrete beams using external unbonded reinforcement. It was shown that the technique could provide useful enhancements in load capacity in all but heavily reinforced cross-sections. The technique offers advantages in speed and simplicity of installation over other, established, strengthening techniques. The earlier work used deflectors in order that supplementary external bars would follow the curvature of the original beam. If these deflectors could be dispensed with, further simplifications could be made in installation procedures. A more extensive programme of physical testing and associated modelling of behaviour has now been performed in order to further explore the capabilities of the technique and to determine the circumstances under which deflectors should be installed. The paper provides a general description of structural behaviour of beams strengthened using the technique. Results of 27 physical tests on strengthened reinforced concrete beams are reported and compared with those from a further eight reference specimens. It is shown that the technique can provide greater strength enhancements to lightly reinforced sections and that provision of deflectors enhances efficiency. The danger of sudden collapse is found to be no greater than that for equivalent conventionally reinforced beams. The various parameters which affect strength enhancements attainable with the technique are reviewed. [ABSTRACT FROM AUTHOR]

High-strength quenched and tempered structural steel has seen an increased usage in the application to heavily loaded columns in multi-storey building construction. This has been particularly true in nations where such steels are abundantly produced, particularly Australia and Japan. Many current international codes do not cater for the use of high-strength steel and thus research is required to give structural engineers the confidence to use this new and innovative material in a safe and efficient manner in construction. Previous research on the use of high-strength structural steel for columns is outlined herein and a summary of previous applications in multi-storey buildings is provided. The paper provides a very comprehensive summary of experimental results on the uses of high-strength structural steel in composite columns specifically for multi-storey building construction. Calibration of these experiments with theoretical models and the Eurocode 4 approach has highlighted some of the differences that need to be implemented in order to design building structures safely with this material. Suggested design recommendations as well as further research is therefore summarised. [ABSTRACT FROM AUTHOR]

The capability of endurance time analysis as an appropriate tool in performance-based earthquake engineering is assessed in this paper. Seismic performance of a comprehensive database of reinforced concrete moment-resisting frames is studied using endurance time and time history analysis. Ground motions used in this study are spectrally matched to the design spectrum which was used for the generation of the input motions of endurance time analysis. This matching facilitates the comparison of the results of two methods at different seismic hazard levels. Comparisons are done for different engineering demand parameters and the pros and cons of the endurance time method are discussed. The endurance time method is shown to provide an estimate of maximum inter-storey drift ratio, roof displacement and plastic hinge rotations that is very close to the results of time history analysis. This method can also correctly predict the distribution of displacement and lateral forces over all storeys. Results are compared with the results of pushover analysis, and the endurance time analysis results are found to be more compatible with the results of time history analysis. In addition, in most frames, the coefficient of variation of engineering demand parameters is less for endurance time analysis than for time history analysis. Results show that input motions of the endurance time method, generated based on a design response spectrum, can be used to assess frames at different seismic hazard levels correctly. [ABSTRACT FROM AUTHOR]

A semi-analytical procedure for the determination of the critical force of a pin-ended column loaded by axial force and bending moment is proposed. It is based on the principle of minimum potential energy of internal and external forces. The equations for strain energy have been derived for the first- and the second-order displacements per section, including compressed and tensile concrete and reinforcement. The energy of the external forces with axial and flexural displacement effects has been derived on the assumed sinusoidal deflection curve. The trapezoid rule is applied to integrate the segment internal energy. The proposed method uses a non-linear stress-strain curve for concrete; bilinear elastic-plastic relationship for reinforcement; equilibrium conditions at a sectional level to generate the strain energies along the member. The effects of shear deformations are neglected. The effect of lateral confining by the stirrups to strength is also analysed. The results obtained with the proposed model have been verified and compared with experimental results from the literature. [ABSTRACT FROM AUTHOR]

A simple and easily applicable analytical method is proposed to obtain the capacity curve of buildings with shear walls as the first stage of a seismic pushover analysis. The method is based on controlling the curvature distribution of shear walls. Accuracy of the method was examined based on data of three sample buildings compiled from the literature. The buildings have different floor areas, number of storeys and cross-sectional areas of shear walls. The method can be economically used with respect to both the computation time and the required equipment. The findings of this paper should be helpful for practising engineers as a quick and dependable hand calculation method for assessing the earthquake resilience of buildings. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including the concrete-based construction materials, computational efficiency on visco-elastic model and the flexural behaviour of concrete mixed with amorphous metal fibres.

Double-headed studs are used as punching shear reinforcement in reinforced or prestressed slabs and footings. Owing to an improved anchoring behaviour, double-headed studs have a higher load capacity than stirrups. Double-headed studs are quick to install and are therefore more cost-effective than stirrups. Previously in Europe, national technical approvals specified the design of double-headed studs. Since the end of 2012, European technical approvals have been available. All approvals are based on the same design method, which is used in combination with BS EN 1992-1-1. It is necessary to distinguish between punching shear failure in slabs and foundations with and without shear reinforcement. In slabs and foundations with shear reinforcement, a failure can occur at maximum load level, in and outside the shear-reinforced zone. The European technical approvals provide design equations for all types of failure modes. To quantify the safety level of the design provisions for slabs, footings, and ground slabs with and without shear reinforcement, test evaluations based on a reliable data bank are shown. The paper also provides useful background information and additional design recommendations for applications, which are not covered by the design provisions of the European technical approvals. [ABSTRACT FROM AUTHOR]

The behaviour of reinforced concrete members with ductile steel reinforcing bars at the ultimate limit state is extremely complex. Consequently, there has been a tendency for the seemingly disparate research areas of flexure, shear and confinement to follow separate paths in order to develop safe approaches to design. In this paper, it is shown how the already much researched and established, but somewhat peripheral, areas of reinforced concrete research of shear friction, partial interaction and rigid body displacements can be combined to produce a single unified reinforced concrete model that simulates the moment-rotation of hinges and their capacities, the shear deformation across critical diagonal cracks leading to failure and the effect of confinement on these behaviours. It is shown that this unified reinforced concrete model is completely generic, as it can be used to simulate reinforced concrete members with any type of reinforcement material (including brittle steel or fibre-reinforced polymer), various cross-sectional shapes of reinforcement (not only round bars but also flat externally bonded or rectangular near surface mounted adhesively bonded plates) and any type of concrete (e.g. high-strength or fibre-reinforced concrete). This new model, therefore, should allow the development of more accurate and safe design procedures as well as enabling more rapid development of new technologies. [ABSTRACT FROM AUTHOR]

Fire safety is the main precondition for the use of wood for multistorey timber buildings and is therefore an important criterion for the choice of material for buildings. The Institute of Structural Engineering at ETH Zurich has accomplished several research projects on the fire behaviour of timber structures over the past 15 years. The research projects aimed at supplying basic data and information on the safe use of timber, in particular for multistorey buildings. Further novel fire design concepts and models have been developed based on extensive theoretical studies, element and full-scale testing as well as a large statistical database on fires in timber. The better knowledge in the area of fire design of timber structures from the research projects, combined with technical measures, especially sprinkler and smoke detection systems, as well as well-trained and equipped fire brigades allow the safe use of timber and a wider field of application of timber for buildings. As a result the Swiss fire regulations of 2005 allow the use of timber structures in multistorey medium-rise residential buildings with up to six storeys. Many other countries have also liberalised the use of timber for buildings or introduced fire regulations that allow for the use of timber on the basis of performance. This paper describes the background of the design concept assumed for multistorey medium-rise buildings. It further presents an overview of two novel calculation models for the verification of the separating function of wall-and-floor timber assemblies as well as for the fire resistance of timber connections. [ABSTRACT FROM AUTHOR]

Reinforced concrete connections, designed prior to the implementation of earthquake design standards, may be vulnerable to shear failure during a seismic attack. Addition of externally bonded fibre-reinforced polymer (FRP) composites can enhance not just the shear capacity but the deformation and energy absorption capacity of the connection. The majority of research studies to date have opted for complete or near-complete coverage of the joint region with FRP and have subjected the test specimens to cyclic (push-pull) loading. Such strengthening schemes and method of loading make it quite difficult to accurately monitor and hence understand the behaviour of the FRP and the concrete beneath. This paper presents results of a series of tests on the strengthening of shear deficient connections with FRP strips subjected to either cyclic or monotonic loading with the primary motivation being accurate description of the behaviour of the FRP. The tests also enable the failure modes to be more accurately reported and classified especially due to the use of monotonic loading. An analytical model is finally presented which accurately describes the mechanics of the FRP strengthening with the model predictions correlating reasonably well with the test data. [ABSTRACT FROM AUTHOR]

The shear capacity of existing concrete structures is often unable to meet current standards requirements. This may be attributable to increased load requirements, inadequate shear provisions in the original design, deterioration of materials or an increased demand in shear capacity owing to flexural strengthening. There are various approaches to the repair and strengthening of existing concrete structures in shear using fibre-reinforced polymer (FRP), involving the use of plates or fabrics externally bonded to the web, prestressed straps wrapped around the beam or the use of bars mounted near the surfaces of the web. However, when only the top or bottom faces of the concrete member are accessible, as in the case of bridge beams made contiguous within a deck or for corbels, a different approach is proposed, called the deep embedment technique: vertical holes are drilled into concrete upwards from the soffit in the shear zones, high-viscosity epoxy resin is injected and then FRP or steel bars are embedded into place. In this paper, the results of a series of tests on unstrengthened and strengthened small-scale and large-scale reinforced concrete and prestressed concrete specimens with and without stirrups are presented. The proposed technique is shown to be feasible, successful and potentially more effective than other shear strengthening approaches. A simple model derived from the truss analogy is shown to be able to predict the capacity of the strengthened beams and can therefore be used as a design tool for the scheme [ABSTRACT FROM AUTHOR]

Steel caging is routinely used to strengthen reinforced concrete (RC) columns in many countries. This paper studies the behaviour of RC columns strengthened by this technique. Following the results obtained from an experimental study, all the specimens are modelled by the finite-element (FE) method. After verifying the FE models, a parametric study is carried out, determining how variations in the parameters affect the behaviour of the strengthened column. FE models are used to compare the ultimate load of RC columns strengthened by steel cages with that obtained from two design rules, showing one of them very conservative and in good agreement with the other. This proposal can be used with confidence for design, since the results obtained are slightly conservative. [ABSTRACT FROM AUTHOR]

Fibre reinforcement increases the toughness of plain concrete under static compressive loading. The compressive toughness of fibre-reinforced concrete (FRC) under impact loading has not, however, previously been investigated. The current paper reviews the behaviour of high-strength fibre-reinforced concrete under uniaxial compressive impact loading. An instrumented drop weight impact machine was used to carry out compressive impact tests on various FRC systems with compressive strengths ranging from about 60 MPa to 120 MPa. The deformations of the FRC cylinders were determined using a high-speed video camera system. As expected, the compressive strength was found to increase with increasing drop height (or impact velocity). The dynamic compressive toughness was also found to increase with increasing drop height and with increasing matrix strength. It was observed that the mode of failure of the FRC was dependent upon the properties of the matrix and of the fibres, as well as on the drop height. Thus, the dynamic compressive toughness of FRC appeared to be dependent on the constitutive behaviour of the matrix, the fibre type and volume, the impact velocity and the mode of failure. [ABSTRACT FROM AUTHOR]

This paper describes a series of experimental studies to investigate the high-mass, low-velocity impact behaviour of reinforced concrete members including beams and slabs, and to provide high-quality input data and results to validate numerical modelling. Fourteen 2·7 m and four 1·5 m span beams, four 0·8 m square 76 mm thick and two 2·3 m square 150 mm thick slabs were tested under impact loads using a drop-weight facility. Measurements included transient impact loads, accelerations and strains in the steel reinforcement. Additionally the impact events were recorded using a high-speed video camera operated at up to 4500 frames per second. For the beam tests, the local failure pattern of a beam under the impact zone was examined by correlating the images of development of cracks, spalling and scabbing with the impact load history. For the slab tests, the imposed energy on a slab was compared with the minimum energy causing the slab to scab, which was predicted using empirical formulae. The investigations enabled a better understanding of the behaviour of reinforced concrete members subject to impact loads. [ABSTRACT FROM AUTHOR]