Experimental strain data from edge-restrained concrete walls are widely used for calibration and validation of numerical and data-driven models. In practice, these data are often preprocessed through spatial averaging, assuming approximately uniform strain behaviour. While this reduces data complexity, its implications for the physical representativeness of modelling targets have not been systematically examined. This study investigates strain variability in four large-scale edge-restrained wall experiments. The results show that variability is systematic, spatially structured, and evolves with time, consistently exceeding measurement uncertainty and confirming its physical origin. Differences between measurements at equivalent locations frequently exceed 100-200 mu epsilon. It is demonstrated that averaged strain values can deviate substantially from the experimentally observed range and, in a significant proportion of cases, do not correspond to physically realised states, introducing inconsistency when used as modelling targets. To address this, strain variability is quantified using range envelopes that define the bounds of observed behaviour, and a structured procedure is outlined for utilising experimental data in model calibration. The findings establish that preserving variability is essential for physically consistent modelling. They further provide an empirical basis for subsequent modelling of early-age behaviour in edge-restrained walls, encompassing traditional numerical simulation, machine learning, and hybrid physics-informed approaches.

Steel fiber reinforced concrete pipes are commonly used in the municipal, agricultural, and industrial fields because of their superior internal water pressure performance. However, the randomly distributed steel fibers hinder the further improvement of internal water pressure performance. To maximise the reinforcement effect of steel fibers and improve the internal water pressure performance, an external circular magnetic field was first utilised to prepare annularly aligned steel fiber reinforced cementitious composite (AASFRC) pipes in which the steel fibers were aligned in the direction of tensile stress. Subsequently, the internal water pressure performance of AASFRC and steel fiber reinforced cementitious composite (SFRC) pipes was experimentally and numerically investigated. Finally, the reinforcement mechanism of the annularly aligned steel fibers was revealed from the aspects of fiber distribution and fiber resultant force. The results showed that the deformation and bearing capacity were enhanced by annularly aligned steel fibers. The ultimate internal water pressure of the AASFRC pipes was greater than that of the SFRC pipes by 22–32% with fiber volume fractions (Vf) of 0.8%, 1.2%, and 1.6%, implying that using less fiber in AASFRC pipes can ensure an internal water pressure performance equivalent to that of SFRC pipes. Both the fiber orientation efficiency factor and number of fibers bridging the principal cracking section of the AASFRC pipes were greater than those of the SFRC pipes. The fiber resultant force of AASFRC specimens was 2.04–2.64 times greater than that of SFRC, contributing to the enhancement in the bearing capacity of AASFRC pipes.

The vertical movement strains of full-scale single-leaf clay brickwork walls (18 brick wide × 13 high) exhibiting enlarged expansion (cryptoflorescence) were monitored in the laboratory over a duration of 90 days, so that a composite model could be developed that would accurately predict the moisture movement strain. Previous studies have failed in their ability to predict the enlarged expansion of clay brickwork walls. Two brickwork walls were constructed, one with ‘kiln fresh’ and one with 28-day old Fletton clay bricks. Using the vertical moisture movement composite model developed by Brooks resulted in a significant underestimation of the amount of measured moisture movement strain. Using the measured strains, equations were developed for the vertical enlarged expansion movement of walls built from ‘kiln fresh’ and 28-day-old Fletton clay bricks. Along with a mortar modification factor, which was applied to the unbonded mortar strains to allow for a better representation of the shrinkage within the masonry to be acknowledged, these equations were used to enhance Brooks’ vertical moisture movement composite model. Whereas previously the composite model failed to predict the movement of masonry exhibiting enlarged expansion (its predictions underestimated the ‘kiln fresh’ and 28-day-old brickwork walls, with a percentage difference of 110 and 177

Externally restraining volume changes of concrete, that is, thermal effects and shrinkage, may result in tensile stresses and eventually cracking. Such cracking risk is controlled/mitigated by the provision of steel reinforcement, which presumes a correct understanding of the cracking patterns under different types of restraint conditions. Reinforced concrete (RC) members may be restrained at their edges or end, or in many cases a combination of the two. Existing guidance on the subject is mostly based on end restrained members, however, it is applied to predict the behavior under edge restraint too. Researchers have identified that the mechanisms of cracking associated with edge and end restraints are quite different. To this purpose, findings from an experimental investigation aiming to understand the behavior of edge restrained RC walls were utilized to validate a finite element (FE) model. Subsequently, this FE model was used to parametrically study walls having different aspect ratios and subjected to different forms of restraint. Cracking patterns, widths, and extent appeared to greatly depend on the type of restraint and wall aspect ratio. The influence of combined restraint, for instance, was found to be more significant in walls with aspect ratio less than 4. The study provides clear evidence on why similar studies, are needed to support engineers in designing against cracking due to restraints.

The influence of sustained eccentric loads including torsion on the time-dependent behaviour of monolithically framed RC beams into columns is investigated in this paper. The adopted experimental program entails a number of beam-column assemblies tested under sustained concentric and eccentric combined loads (bending, shear, and torsion). The presence of Fibre Reinforced Polymers (FRP) wraps applied to the beam is considered and the time-dependent performance was thoroughly assessed. The outcomes of the experimental program complemented with finite element (F.E.) results illustrated a significant increase in the time-dependent beam's twisting and deflection levels. The rise in the beam's time-dependent deflections was quantified in comparison with those predicted according to Eurocode 2. This rise can be explained by the extent of torsional cracks observed, accompanied by high strain levels, resulting from the interaction between combined loads and the timedependent deformations of concrete. While the FRP wraps considerably improved the time-dependent torsional stiffness compared to the un-strengthened specimens. The numerical models under different loads ratios (torsion to bending-shear ratio) confirmed the role of the level of combined loads and the developed time-dependent cracks of reducing the members' stiffness and affecting the twisting levels and hence increased the deflection values. A refined approach of the Eurocode 2 modal has been proposed which considers the interaction of combined forces and hence, the developed stresses on the degrees of the loss of tension stiffening.

Through cracking resulting from external restraint of early-age thermal and long-term shrinkage strain is a significant issue in the construction industry as it causes leakage in water retaining and resisting structures. Concerningly, a recent field study found restraint induced crack widths to frequently exceed crack widths calculated in accordance with UK design practice (BS EN 1992-3 and CIRIA C766). Due to a lack of pertinent data, the reasons for this are uncertain. This paper compares measured and predicted crack widths in a series of 12 full-scale edge restrained walls constructed in the laboratory. The tests examine the influence on cracking of key parameters including concrete mix design, wall reinforcement ratio, wall aspect ratio and relative wall to base cross-sectional area. The measured and calculated crack widths are compared at first cracking and at the end of monitoring. Two types of behaviour were noted in the tests, dependent on when the first cracks formed. Cracking either occurred at early age, within 24 h of stripping the formwork, or later due to restraint of combined early age thermal contraction and shrinkage. The final crack widths were greatest, by a considerable margin, in walls where cracks formed at early age, despite the initial cracks being very narrow. BS EN 1992-3 gives the best estimates of crack width in the two walls that cracked at early age. Crack widths in these walls were significantly underestimated by C766. In the other 10 walls, which cracked later, C766 tends to give the best estimate of crack width.

This paper presents experimental results on the long-term loss of tension stiffening of concrete containing recycled aggregate and steel fibres. Washed construction and demolition wastes (CDW) size 20 mm were used as a replacement for the natural coarse aggregate, and hooked-end steel fibres (DRAMIX 3D 65/35BG) were added to the mixes. Square section prisms of concrete (120x120x1200 mm) reinforced with a central steel bar were prepared and cast with different replacement percentages of recycled aggregate and volume fractions of steel fibres. A direct tensile load was applied to the steel bar and the measurements of the strain on the concrete surfaces were then recorded for a period of 35 days to assess the long-term loss of tension stiffening. The results indicated that the substitution of NA by RA increased the loss of tension stiffening over time up to 12.9%. However, the addition of steel fibres proved to be highly beneficial; the inclusion of 0.5% and 1.0% steel fibre content to the NC and RAC reduced the loss up to 9.8% and 20.4%, respectively. According to the obtained results, modifications to the Eurocode2 method for predicting the long-term deflection of reinforced concrete beams were proposed to be implicated in the calculation steps for this type of concrete.

Excessive cracking due to restraint of thermal and shrinkage strains is a widespread problem in the concrete construction industry. In design, restraint induced cracking is managed by the provision of reinforcement intended to distribute internal strains in such a way as to control the cracking pattern and limit crack widths. The area of secondary (horizontal) reinforcement required in members such as retaining walls and water tanks is often governed by the need to control early age thermal cracking. This paper presents results from four edge restrained walls tested at Imperial College London and the University of Leeds as part of an Engineering and Physical Sciences Research Council funded project into restraint induced cracking. The paper describes the development of volumetric strain and cracking in the tested walls. The cracking performance is assessed by comparing the restrained strain with the tensile strain capacity of concrete.

Fibre-reinforced concrete (FRC) has been increasingly used in construction for several decades to reduce crack growth by incorporating one or two types of fibre in reinforced concrete elements under the static load. This paper intends to investigate experimentally how hybrid fibre systems (micro and macro polypropylene fibres and steel fibres) can enhance the performance of RC beams subjected to static loading by restricting the development of micro-cracks and macro-cracks. The test programme consisted of testing six full-scale simply supported beams. The main parameters were fibres’ addition (i.e. steel and polypropylene fibres) and volume fraction (i.e. 1 and 1.5% for steel and hybrid fibre system (1% steel, 0.1% micro, and 0.4% macro polypropylene fibres)). From the test data analysis, it was found that the hybrid fibre system decreased the deflection, reduced the strain in the steel reinforcement bars, and reduced the crack width. The splitting tensile strength and compressive strength of the hybrid fibre-reinforced concrete was greater than that of the single fibre-reinforced concrete. The addition of more than two types of fibres illustrates a pronounced beneficial hybrid effect.

Externally restraining volume changes of concrete, i.e. thermal effects and shrinkage, may result in tensile stresses and eventually cracking. Such cracking risk is controlled / mitigated by the provision of steel reinforcement, which presumes correct understanding of the cracking patterns under different types of restraint conditions. Reinforced concrete (RC) members may be restrained at their edges or end, or in many cases a combination of the two. Existing guidance on the subject is mostly based on end restrained members, however it is applied to predict the behaviour under edge restraint too. Until now the behaviour of members subjected to edge restraint or combined restraint has not been studied separately in considerable detail. Yet, lately researchers have identified that the mechanisms of cracking associated to edge and end restraints are quite different.

This paper presents the results of an investigation into the long-term flexural behaviour of cracked reinforced recycled aggregate concrete (RAC) beams. Washed construction and demolition wastes (CDW) with a maximum size of 20 mm were used as the coarse recycled aggregate. The main variable in the research was the replacement ratio of recycled aggregate. Specimens with 0%, 50% and 100% recycled aggregate were cast and tested. The experimental results showed that samples with an increased amount of recycled aggregate had significantly reduced strength and a noticeable increase in both short-term and long-term deflection of RAC beams over equivalent normal concrete (NC) beams. Increased levels of RA resulted in greater creep and shrinkage of RAC and greater long-term loss of tension stiffening in RAC reinforced tension specimens. Prediction of long-term deflections using Eurocode 2, even after incorporating the experimental concrete properties within the Code method, underestimated the experimental deflections of the RAC beams. However, by modifying the tension stiffening factor, β used in Eurocode 2, deflections were predicted to within approximately 1%. From this investigation, it is recommended that the factor β be reduced from 0.5 (for NC) to 0.4 (for RAC @50% replacement) and 0.3 (for RAC @100% replacement).

Abstract Three equivalent exterior precast concrete beam-column (PCBC) connections have been investigated in this study in orderto analyze the effect of steel fiber reinforced concrete (SFRC) as cast-in-place (CIP) on the seismic performance of the PCBC connection. The connection was designed as a ductile connection for a moment-resisting frame and consists of a precast U-beam, precast column with corbel, interlocking bars, and CIP-concrete to connect the precast beam to precast column. The volume fractions of steel fiber incorporated within the CIP-concrete were 0%, 0.5% and 1%. A quasi-static load was applied vertically to the beam tip of the PCBC specimen. The results showed that the steel fibers contained within the CIP-concrete provided 2% increase of the maximum load, 17.7% increase of the energy dissipation, and increase in the joint stiffness of the PCBC connection. The steel fibers delayed the onset of cracking and slowed down the crack propagation, resulting in shorter cracks in the joint core of PCBC specimen, which correlates well with the deflection-hardening characteristic found from the modulus of rupture test.

This paper investigates the experimental and analytical behaviour of beam-column joints that are subjected to a combination of torque, flexural and direct shear forces, where different Carbon Fibre Polymer (CFRP) strengthening wraps have been applied only to the beam. These wrapping schemes have previously been determined by the research community as an effective method of enhancing the torsional capacities of simply supported reinforced concrete beams. In this investigation, four 3/4-scale exterior beam-column joints were subjected to combined monotonic loading; three different beam wrapping schemes were employed to strengthen the beam region of the joint. The paper suggests a series of rational formulae, based on the space truss mechanism, which can be used to evaluate the joint shear demand of the beams wrapped in these various ways. Further, an iterative model, based on the average stress-strain method, has been introduced to predict joint strength. The proposed analytical approaches show good agreement with the experimental results. The experimental outcomes along with the adopted analytical methods reflect the consistent influence of the wrapping ratio, the interaction between the combined forces, the concrete strut capacity and the fibre orientation on the joint forces, the failure mode and the distortion levels. A large rise in the strut force resulting from shear stresses generated from this combination of forces is demonstrated and leads to a sudden-brittle failure. Likewise, increases in the beams' main steel rebar strains are identified at the column face, again influenced by the load interactions and the wrapping systems used.

These recommendations have been prepared by the corresponding working group within RILEM TC 287-CCS “Early-age and long-term crack width analysis in RC structures”, following work by the previously ceased RILEM TC 254-CMS “Thermal cracking of massive concrete structures”. This recommendations document is developed in complementarity to the state-of-the-art report of RILEM TC 254-CMS and aims to provide expert advice and suggestions to engineers and scientists interested in modelling the thermo-chemo-mechanical behaviour of massive concrete structures since concrete casting. Recommendations regarding geometrical characteristics and complexities, concrete properties and appropriate material models, boundary conditions and loads, and numerical model peculiarities with relevance to the simulation of the thermo-chemo-mechanical behaviour of massive concrete structures are given herein. The recommendations have been reviewed and approved by all members of the TC 287-CCS.

The article “Uniaxial tensile behavior of aligned steel fibre reinforced cementitious composites”, written by “Longbang Qing, Kelai Yu, Ru Mu, John P. Forth”, was originally published electronically on the publisher’s Internet portal (currently SpringerLink) on 25 June 2019 without open access.

The restraint of imposed strains in edge-restrained members was investigated. In particular, the influence of vertical steel reinforcement between the restrained member (wall) and the restraining member (base) on the mechanism of restraint development was experimentally examined. Real-scale reinforced concrete (RC) walls on RC bases were constructed and the investigation analysed why previous studies, which have mostly utilised steel members to restrain the imposed strain, are inappropriate for gaining an understanding of edge restraint as they fail to reflect the heat transfer between the wall and the base. The results of this study revealed that the degree of restraint increased in the presence of vertical steel reinforcement from 0·37 to 0·72. It was also found that restraint increased over time due to the steel reinforcement and decreased in its absence. A finite-element analysis of the walls was also conducted to highlight the significance of correctly incorporating real-time boundary conditions.

The purpose of this short paper is threefold. First we discuss the underlying properties of the dominant organisational model for trade unions in Britain. Second, we look at options for changing this organisational model. Third, we conclude by looking at what this might imply for the future operation and organisation of trade unions and their engagement with their members.

Over the last few decades, progressive collapse disasters have drawn the attention of codified bodies around the globe; as a consequence, there has been a renewed research interest. Structural engineering systems are prone to progressive collapse when subjected to abnormal loads beyond the ultimate capacity of critical structural members. Sudden loss of critical structural member(s) triggers failure mechanisms which may result in a total or partial collapse of the structure proportionate or disproportionate to the triggering event. Currently, researchers adopt different modelling techniques to simulate the loss of critical load bearing members for progressive collapse assessment. GSA guidelines recommend a column removal time less than a tenth of the period of the structure in the vertical vibration mode. Consequently, this recommendation allows a wide range of column removal time which produces inconsistent results satisfying GSA recommendation. A choice of a load time history function assumed for gravity and the internal column force interaction affects the response of the structure. This paper compares different alternative numerical approaches to simulate the sudden column removal in frame buildings and to investigate the effect of rising time on the structural response.

This paper presents an experimental study on the influence of ambient relative humidity on tensile creep of plain concrete amended with Ground Granulated Blast - furnace Slag and compares it with its influence on compressive creep. Tensile and compressive creep tests were carried out on concrete specimens of 34.49 MPa compressive strength and 0.56 water/binder ratio at 51, 68 and 100% relative humidity. The results show a linear relationship between compressive creep and relative humidity; this cannot be said about tensile creep. Tensile creep was observed to be more sensitive to change in ambient humidity than compressive creep. Based on equal applied stress, tensile creep was found to be several times higher than compressive creep and the difference was great er in drying creep than in basic creep. On the basis of equal stress/strength ratio, tensile - to - compressive creep ratio was slightly less than 1 for drying creep and much less for basic creep. Keywords: Compressive Creep, Concrete, Relative Humidity, Strain, Strength, Tensile Creep

This paper compares the flexural behaviour of cracked partially bonded (in the mid-span, maximum moment zone) reinforced concrete beams subjected to (i) static sustained load and (ii) static sustained with cyclically repeating load. Information relating to surface strains and mid-span deflections were continuously recorded for a period of 90 days. The sustained load level represented that which produced the stabilized crack pattern. The amplitude of the superimposed cyclic load was considered to be a small fraction of the sustained load. The experimental outcome shows that under sustained load alone, the long-term mid-span deflection of reinforced concrete beams with artificially debonded reinforcement is substantially higher than that of normally bonded equivalent beams. For the cyclically exerted load addition there was no substantial difference between the observed ultimate deformations of bonded and debonded beams. Nonlinear finite element software (Midas FEA) was used to simulate these results and it was found that a numerical-experimental match can be achieved after applying necessary modifications to the distribution of shrinkage down through the beams' cross-section.