This paper is an attempt to provide a detailed procedure for the finite element modelling and simulation of concrete-filled steel tubular (CFST) columns subjected to axial compression using the commercial software package ANSYS 12. A modified material model for modelling the concrete core is described and explained. Composite action is modelled between the concrete core and the steel tube and the procedure is presented with the recommended properties for modelling such behaviour. The proposed model is then validated by comparing its numerical results with selected experimental results available in the literature. The proposed model is used to investigate numerically the load transfer mechanism of CFST columns filled with different grades of concrete in order to study the effect of this parameter - i.e. compressive strength of concrete core - on the load transfer mechanism in such columns. Further, the proposed model has been employed for investigating the confining pressure provided by the steel tube on the concrete core along the length of the CFST column.

Steel composite hollow columns have been studied in order to ease their construction. Welding or bolting are mostly used for connecting the steel tubes of precast steel composite hollow columns. However, welding generally results in temperatures of about 20000 °C in the welding zone and 1300 °C around the welding zone. Thus, the strength of the concrete in regions close to a welding zone is reduced. In this paper, the effects of arc welding and electro-slag welding - two widely used methods for connecting the column modules of steel composite hollow columns - on the temperature change in the welding zone are studied by performing heat transfer analysis. The changes in the strength of the concrete are investigated for each welding method. The rate of decrease in concrete strength due to electro-slag welding was greater than that due to arc welding. In addition, an effective method using ceramic fibres is suggested for preventing strength reduction in concrete due to welding heat.

The prescriptions provided by codes of practice for assessing the minimum reinforcement amount for strength purposes in reinforced concrete beams usually disregard the non-linear contribution of concrete in tension and size-scale effects. In the present paper, these phenomena are taken into account correctly in the description of the flexural failure in lightly reinforced concrete beams by means of a numerical algorithm based on non-linear fracture mechanics. In this context, the application of dimensional analysis permits a reduction in the number of governing parameters. In particular, it is demonstrated analytically that only two dimensionless parameters, referred to as reinforcement brittleness number and stress brittleness number, are responsible for the brittle-to-ductile transition in the mechanical response. According to this approach, new formulae suitable for evaluating the minimum reinforcement in practical applications is proposed for both rectangular and T-sections. A comparison with experimental results demonstrates the effectiveness of the proposed model for different reinforcement percentages and beam depths.

This paper aims to put into perspective the influence of long-term effects, such as concrete creep and shrinkage, on concrete cracking. Long-term experimental results obtained at the Centre for Infrastructure Engineering & Safety (CIES) are reported and compared to design estimates made using the fib Model Code for Concrete Structures 2010. The influence of factors such as stirrup spacing and concrete cover are discussed. Results show that time-dependent shrinkage-induced cracking can considerably modify the cracking patterns obtained in short-term tests. For crack control in real structures and for the development of models for inclusion in codes of practice, it is strongly recommended that account be taken of time-dependent effects. Limiting observations to those made in short-term tests may lead to erroneous conclusions that are simply not applicable for structures that are more than a few weeks old.

The experimental results for quasi-brittle materials such as concrete and fibre-reinforced concrete exhibit high variability due to the heterogeneity of their aggregates, additives and general composition. An accurate assessment of the fracture-mechanical parameters of such materials (e.g. compressive strength fc and specific fracture energy Gf) turns out to be much more difficult and problematic than for other engineering materials. The practical design of quasi-brittle material-based structures requires virtual statistical approaches, simulations and probabilistic assessment procedures in order to be able to characterize the variability of these materials. A key parameter of non-linear fracture mechanics modelling is the specific fracture energy Gf and its variability, which has been a research subject for numerous authors although we will mention only [1, 2] at this point. The aim of this contribution is the characterization of stochastic fracture-mechanical properties of four specific, frequently used classes of concrete on the basis of a comprehensive experimental testing programme.

After a concrete structure has been exposed to fire, a combination of destructive and non-destructive testing, expert judgment and calculations is used to decide whether the structure should be demolished or repaired, or can continue to be used without repairs or rehabilitation. However, there are many uncertainties associated with both the fire duration and the effect of elevated temperatures on the residual mechanical properties of the materials. Consequently, the maximum service load after fire exposure should be assessed based on reliability considerations in order to provide an adequate level of safety. As this type of calculation is too complex and time-consuming for practical use, a reliability-based assessment tool has been developed for concrete structures and applied to slabs to determine the maximum service load after fire. When using the proposed method, a safety level is targeted which is comparable with the safety level associated with the Eurocode format for the design of new structures. It is concluded that the proposed assessment method is both user-friendly and directly applicable in practice.

Bond can play an important role in the assessment of existing structures, particularly when corrosion of reinforcement is to be expected. The results of bond tests on corroded bars embedded in concrete are not yet fully conclusive for the definition of bond degradation due to the effect of corroded reinforcement. The structural effects of bond degradation can assume a different importance following the resisting mechanism that is activated within the structure. A critical review of the data available is presented here; some aspects such as embedment length, corrosion rate and type of test are analysed.

This article provides an overview of the findings and production processes for the mineral materials that have been developed and tested worldwide in the past with regard to the establishment of a lunar base. Firstly, the aim of and procedure for constructing a lunar base are briefly outlined. Following that, the lunar environment factors and their influence on a possible structure are described. The paper then presents the advantages and disadvantages of the materials examined, such as sulphur concrete, cast basalt, lunar concrete or polymer concrete, on the one hand, as well as production processes investigated previously, such as sintering, geothermite reaction and 3D printing, on the other. One promising method is the dry-mix/steam-injection (DMSI) method for producing a lunar concrete as a possible material which was developed by T. D. Lin and is based on cement made from lunar resources.

AAYE: award opportunity for young engineers; First fib PhD Symposium held in North America; International conference in Moscow attracts renowned specialists; Innovation in Oslo; NZCS: New Zealand's member group; Structural Concrete impact factor on the rise; fib Bulletin 72; Montreal: the state-of-the-art in FRC; Short notes; EWH Gifford † 1921-2014; Congresses and symposia; Acknowledgement

No short description available.

No short description available.

The Norwegian Public Roads Administration started a programme named “National Tourist Routes in Norway” in 1994. Today it includes 18 selected routes from south to north. The uniqueness of these attractions lies in the spectacular architecture found at the viewpoints, places of interest and visitor centres located amid magnificent scenery.
The aim of the tourist routes was to strengthen Norway's position in the marketing of international tourism and to help promote local business.
The routes are carefully selected and allow tourists to enjoy some of the most spectacular scenery in the country. Young Norwegian sculptors and architects, and a few renowned ones from abroad too, were invited to take up the challenge of creating unique viewing platforms, service buildings, footbridges, ramps, benches and stairs to be placed along the different routes. All are so unique that tourists automatically stop as they drive along, not just to admire the scenery, but also the special objects.
Several of these objects are in concrete, and four are presented below. (Map references for the individual projects are listed for easy searching on Google Earth)

The pullout behaviour of single steel fibres embedded in a concrete matrix is investigated for various configurations of fibre types and embedment lengths and angles by means of laboratory tests and analytical models. Laboratory tests for fibre pullout are performed to investigate the fibre-matrix bond mechanisms. Parameters influencing the fibre pullout response, such as fibre shape, fibre tensile strength, concrete strength and fibre inclination angle are systematically studied. The effects of these parameters on the pullout force versus displacement relationship, fibre efficiency and fibre/matrix failure response are analysed based on the experimental results. For the analytical modelling of the fibre pullout behaviour of straight fibres, an interface law is proposed for the frictional behaviour between fibre and matrix. In the case of inclined fibres, the plastic deformation of the fibre and the local damage to the concrete are also considered. For hooked-end fibres, the anchorage effect due to the hook is analysed. Combining these sub-models allows the pullout response of single fibres embedded in a concrete matrix to be predicted. In addition, numerical simulations of pullout tests are performed to obtain insights into the local fibre-concrete interactions and to provide supporting information for the analytical modelling. The models are successfully validated with the experimental results.

This paper presents an experimental campaign aiming to assess the cracking behaviour of flexural members made with self-compacting concrete (SCC) and reinforced with both rebars and steel fibres recycled from end-of-life tyres (ELT). The characteristics, constructability and performance of this new type of fibre are first discussed. The results of the tests carried out are then presented and discussed. The parameters that have been investigated are: &phgr;/&rgr;s,ef, concrete cover and fibre content. The results obtained show improvement in cracking behaviour, especially for low reinforcement ratios and large covers. Results are compared with the predictions of the recently published fib Model Code for Concrete Structures 2010. The main objective of this investigation is to evaluate the efficiency of a new type of fibre technology for crack width control of RC elements, with advantages in sustainability from the point of view of recycling and durability.

The results of 45 pullout tests on 8, 10 and 12 mm diameter deformed steel bars concentrically embedded in recycled aggregate concrete designed using equivalent mix proportions with coarse recycled concrete aggregate (RCA) replacement levels of 25, 50, 75 and 100 % are described here. Although consistent results were not obtained for the 8 mm bars, the normalized bond strengths of the 10 and 12 mm bars across all RCA replacement levels were higher for the RCA concretes compared with the natural coarse aggregate concrete, and they increased with RCA replacement levels. Brittleness index, an analogous parameter from rock mechanics, has been shown to be a relevant predictor of the measured bond strengths. An empirical bond stress-slip relationship has been proposed and it has been conservatively suggested that anchorage lengths for the 10 and 12 mm deformed bars in recycled aggregate concrete may be taken to be the same as those in natural aggregate concrete.

This paper first presents an experimental study on the shrinkage and creep behaviour of recycled aggregate concrete (RAC) with different recycled coarse aggregate (RCA) replacement percentages (i.e. 0 %, 33 %, 66 %, 100 %). The experimental results reveal that increasing the RCA replacement percentage can increase the shrinkage and creep of RAC. A numerical method for creep behaviour with old adhering mortar is also proposed by analysing the influence mechanism of creep and the volume content of old adhering mortar on the creep of RAC. It is found that the RAC creep is significantly influenced by old adhering mortar properties and its volume content. Finally, a numerical model of RAC creep is established by considering the influence of mechanical properties and the creep behaviour of old adhering mortar. It is proved that this model can calculate the creep of RAC.

Engineers know only too well that early-age cracking accounts for the decrease of long-term serviceability for a majority of infrastructure. In immersed tunnels, early-age cracks may leave paths for aggressive media, which lead to deterioration and thus compromise durability. On the other hand, the cracking risk in concrete structures depends on a number of factors, such as material properties, construction methods, curing measures, etc., which make decisions complex.
This work presents the results of a sensitivity analysis of early-age behaviour for an immersed tunnel cast in situ. Numerical modelling and local sensitivity methods are employed to evaluate the sensitivity of early-age cracking to casting temperature, formwork conductivity, formwork removal time, curing temperature and ambient temperature. The numerical results indicate that the casting and curing temperatures appear to be the most dominant factors with regard to the whole fabrication period.
This study provides a realistic method for determining the uncertainty analysis of concrete structures at an early age, and identifies the most important factors during the fabrication of immersed tunnel segments, which is beneficial for further decisions related to the control of early-age cracking.

Concrete structures can suffer from water permeating under stresses. This paper investigates the surface water permeability of reinforced concrete elements subjected to uniaxial tension. A testing system was developed to combine a conventional loading machine with a surface permeameter. To eliminate the effect of initial absorption of water, calibration tests were conducted on plain concrete samples with different surface saturated states. The experiment presented is designed to test the surface water permeability of a structural member under uniaxial tension. Specimens were reinforced centrally with different sizes of steel bar and fabricated with normal-strength and high-strength concrete. A uniaxial tensile load was applied from 0.10 to 0.80 of estimated ultimate cracking load in 0.10 increments. At the same time, water permeability was measured at each load step. Test results give the relationship between water permeability of concrete member and tensile load levels.

This study investigates the dynamic biaxial behaviour of concrete by testing more than 60 cubic specimens on a custom-designed, servo-hydraulic-controlled machine. Each specimen was axially loaded in compression at a constant strain rate of 10-5, 10-4, 10-3 or 10-2 s-1 while two opposite side faces were subjected to a constant confining pressure and the other two side faces were free. The confining pressure applied to each specimen was 0, 30.5, 61.0 or 91.5 % of its uniaxial compressive strength. Test results indicate that the biaxial strength of concrete increases with strain rate at a reduced slope as confining pressure increases. The failure mode of the concrete specimens was basically unaffected by the strain rate. An empirical relation for the ultimate strength of concrete in a biaxial stress state was developed taking into account the effects of both confinement and strain rate.

This paper discusses the residual modulus of elasticity of and maximum compressive strain in high-strength concrete (HSC) and fibre-reinforced high-strength concrete (FRHSC) after being subjected to axial high-stress-level cyclic loading. The paper presents a specific procedure for evaluating the residual values of these mechanical parameters of concrete specimens.
This procedure reveals that there is no monotonic decrease in the residual modulus of elasticity with number of cycles; an initial decrease occurs in all cases, followed by an increase and, finally, another decrease. Similarly, there is no monotonic increase in the residual maximum compressive strain.
The results show substantial changes in both the residual modulus of elasticity of and the residual maximum compressive strain in concrete depending on the number of cycles. These variations are due to the combined action of two concrete phenomena: microcracking and reconsolidation of the concrete microstructure.

Fibre-reinforced polymers (FRP) in the form of externally bonded reinforcement have been used successfully in the rehabilitation of concrete structures. Although considerable data has been produced on the performance of strengthened RC structures, the reliability of strengthened structures can be significantly reduced due to the variability in the FRP properties, especially when the wet layup technique is used. In addition to this, structural engineers are concerned about the durability of FRP-strengthened structures under extreme loading conditions. Nonetheless, knowledge of the behaviour of strengthened elements under fatigue loading may be important to raise confidence in the strengthening systems. This paper presents the results of an experimental programme developed to investigate the behaviour up to failure of RC beams strengthened with high-performance carbon and aramid fibre sheets and subjected to static and cyclic loadings in terms of ultimate loads, deflections, cracking behaviour, failure modes and fatigue life by means of loading, crack width and deflection monitoring. Experimental data on fatigue life were used to validate analytical models developed for strengthened and unstrengthened beams.

A series of 10 reinforced concrete T-beams, designed deficient in shear, were tested in order to investigate the shear performance achieved through externally applied U-shaped FRP composite strips. Key variables of the study were: type of FRP composite, type of surface bonding and type of end anchorage for the strips. Carbon fibre-reinforced polymer (CFRP), glass fibre-reinforced polymer (GFRP) and high modulus of elasticity carbon fibre-reinforced polymer (Hi-CFRP) strips were the special composite types with different elastic moduli, full or partial bonding of the strips to the beam surface were the variables for the type of surface bonding. All partially bonded FRP strips were free from surface bonding, whereas epoxy-bonded FRP anchors were used at their ends close to the slab-to-beam connection. Those strips with full surface bonding have either epoxy-bonded FRP anchors at their ends or the strip ends were without anchorage. The test results revealed that shear-deficient beams may well be strengthened by the externally applied FRP strips. However, the level of strength enhancement and the failure pattern is closely influenced by the composite's elastic modulus, the type of surface bonding and the type of end anchorage for the FRP strip itself. The enhancement of the Hi-CFRP strips did not live up to expectations. The use of unbonded FRP for shear strengthening yielded promising results.

The main objective of this investigation is to provide an alternative method for the damage detection and assessment of bridge structures based on comparisons between finite element (FE) modelling/analysis and field data. The field data reported in this paper refers to the use of a non-destructive structural testing method (IBIS-S sensor system - displacement/movement-detection sensors with interferometric capabilities) and visual inspections. The FE models developed and presented in this study demonstrate certain degrees of reliability in terms of predicting the mechanical behaviour of the bridge structure under investigation. The FE models were developed using the ANSYS software package. This investigation also provides a detailed report on the application of the field survey that was carried out on a rather heavily used bridge located in Chatham, Kent, UK. The field data concerning the IBIS-S sensors correspond to subjecting the bridge to different static and dynamic loading conditions. The static and dynamic structural responses of the bridge were created by driving a lorry up and down the bridge. The same loading conditions were then simulated using the FE model developed to verify the sensitivity of the model. This FE model was then used to study the response of the bridge to other loading conditions. It is believed that the proposed method could potentially be used for assessing bridge structures within the context of the health monitoring of structures.

Life-cycle civil engineering addresses, among other things, the growing number of deteriorating bridges and the associated economic challenges. As a consequence, government bodies, infrastructure and bridge owners as well as industry request objective and rational performance indicators for classification and intervention planning in structural engineering. This paper focuses on a methodology for analysing the damage-based robustness margins of bridge systems under traffic loading. In particular, a series of emergent deterioration-based damage scenarios are compared with the actual or virgin state in terms of loadbearing capacity and serviceability. Non-linear finite element analysis based on a detailed 3D model has a high potential for capturing the available bridge capacity for different degradation phenomena and levels, serving as an input for further reliability-based performance indicators. Notwithstanding, costs associated with fully probabilistic assessment measures are still prohibitive despite technological advances and new methods of reducing the sample size in Monte Carlo computations. In addition, considering the large uncertainties and imprecision involved, it is imperative that probabilistic schemes are preferred over deterministic assessments.
The objective of this article is to present strategies for robustness-based performance assessment using non-linear modelling and to discuss relevant reliability-based quantities and performance indicators in relation to structural damage using the example of specific degradation events in an existing prestressed box girder bridge. Furthermore, some strategies are developed on the basis of the new approach for general complex engineering structures.

Anchorage zones in post-tensioned concrete structures offered by the construction industry are subject to a certification process, which checks compliance with codes of practice and safety requirements. This certification is based on load transfer tests on specimens, which represent the real structural solutions. Such tests can be supplemented by numerical simulations based on computational mechanics. Those simulations represent a powerful tool for interpreting test results and contribute to a better understanding of the structural behaviour of anchorage zones.