Many reinforced concrete bridges in Europe and around the world are damaged by reinforcement corrosion and the annual maintenance costs are enormous. It is therefore important to develop reliable methods to assess the structural capacity of corroded reinforced concrete structures and avoid unnecessary maintenance costs. Although there are advanced models for determining the load carrying capacity of structures, it is not obvious how they should be used to verify the performance of existing structures. To confidently assess the bond of corroded reinforcement in concrete, for example, the calculation model must give a sufficient safety margin. When designing new structures, semi-probabilistic approaches (such as the partial safety factor method) are adopted to achieve the target reliabilities specified in structural design codes. This paper uses probabilistic methods to develop partial factors for application in an existing bond model, to assess the safety of corroded reinforced concrete structures. The response of the bond model was studied using Monte Carlo (MC) simulations for several design cases, with probability distributions fitted to the results. Partial factors were then derived, based on these distributions. Furthermore, an MC-based simulation technique called “importance sampling” was used to study the reliability of several deterministic bond assessments conducted using these partial factors. The results show that deterministic assessments which use the proposed partial factors lead to a safety level at least equal to the target value. The results presented in this paper will support the assessment of reinforced concrete structures with anchorage problems and give a reasonable approximation of the anchorage capacity with sufficient safety margin. When generalised to cover other failure modes and structural configurations, this will enable better utilisation of damaged structures and lead to major environmental and economical savings for society.

Corrosion of the reinforcement in concrete structures affects their structural capacity. This problem affects many existing concrete bridges and climate change is expected to worsen the situation in future. At the same time, assessment engineers lack simple and reliable calculation methods for assessing the structural capacity of structures damaged by corrosion. This paper further develops an existing model for assessing the anchorage capacity of corroded reinforcement. The new version is based on the local bond stress-slip relationships from fib Model Code 2010 and has been modified to account for corrosion. The model is verified against a database containing the results from nearly 500 bond tests and by comparison with an empirical model from the literature. The results show that the inherent scatter among bond tests is large, even within groups of similar confinement and corrosion level. Nevertheless, the assessment model that has been developed can represent the degradation of anchorage capacity due to corrosion reasonably well. This new development of the model is shown to represent the experimental data better than the previous version; it yields similar results to an empirical model in the literature. In contrast to many empirical models, the model developed here represents physical behaviour and shows the full local bond stress-slip relationship. Using this assessment model will increase the ability of professional engineers to estimate the anchorage capacity of corroded concrete structures.

In the design of two-way reinforced concrete slabs, e.g. using the strip or yield line design method, the possibility of redistributing the load between different loading directions is used. The main aim of the present study was to investigate how fibres affect the structural behaviour such as the possibility for redistribution, crack patterns and load-carrying capacity. The investigation was conducted by means of experiments on two-way octagonal slabs, simply supported on four edges, centrically loaded with a point load. The slabs spanned 2.2m in both directions and the reinforcement amount was twice as large in one direction as in the other, in order to provoke uneven load distribution. Three slabs of each reinforcement configuration were produced and tested: conventionally reinforced slabs, steel fibre reinforced slabs and a combination of both reinforcement types. The reaction force on each supported edge was measured on five rollers per edge. A moderate fibre content (35kg/m3) of double hook-end steel fibres was used. The steel fibres affected the structural behaviour significantly by providing post-cracking ductility and by increasing the ultimate load-carrying capacity by approximately 20%. Most significant, the steel fibres influenced the load redistribution in such a way that more load could be transferred to supports in the weaker direction after cracking. Further, more evenly distributed support reactions were obtained in the slabs containing both reinforcement types compared to the case when only conventional reinforcement was used. The slabs reinforced by steel fibres alone did not experience any bending hardening; however, a considerable post-cracking ductility was observed. Furthermore, the work presented in this paper will provide results suitable for use in benchmarking numerical and analytical modelling methods for steel fibre reinforced concrete, as the experimental programme also included extensive testing of material properties.

In order to stabilize timber-framed buildings against lateral loads, the diaphragm action of roofs, floors and walls is often used. This paper deals with the influence of imperfections such as gaps and uplift on the stiffness and the horizontal displacement of fully anchored shear walls. The significance of analyzing the effects of imperfections is evident when evaluating the stiffness of shear walls; tests of walls show that the horizontal displacement is underestimated in calculations using the stiffness of sheathing-to-framing joints as obtained from experiments. Also, in real structures where hold-downs are used, the influence of gaps and uplift should be included in order to obtain realistic displacements in the serviceability limit state. The analytical model is based on ideal plastic behavior of the mechanical sheathing-to-timber joints with stresses parallel to the perimeter of the frame and on linear elastic behavior for stresses perpendicular to the bottom rail. Using this elasto-plastic model, the equations for the stiffness and the deflection versus the number of segments in the wall are derived. The fully anchored condition for the shear walls is simulated by applying a diagonal load to the shear wall. Three types of imperfections are evaluated: Walls with gaps at all studs, a gap only at the trailing stud, and gaps at all studs, except at the trailing stud. It is shown that the effect of imperfections on the stiffness of the wall in the initial stage is considerable. Depending on the distribution of the gaps and the number of segments included in the shear wall, the displacement of the shear wall is increased several times compared to that of a fully anchored wall diaphragm with no gaps; e.g. for a single segment wall more than four times. However, for walls with more than six segments the effect of imperfections can be neglected. Finally, the theoretical model is experimentally verified.

Masonry walls are bulky and heavy and have therefore the potential to act naturally as a protective system to blasts. Yet, they are known to have a limited flexural and torsional capacity, particularly when unreinforced. When exposed to shockwaves, they experience out-of-plane failure mechanisms which may affect the overall stability of the building and engender flying debris inside the building. The out-of-plane response of unreinforced masonry walls to blasts depends on many factors characterizing both the wall and blast action, making any sort of prediction difficult. In this context, experimental tests and numerical models become key tools that can be used to study the wall’s response on a case-by-case basis. This review covers the major experimental and numerical approaches to assess the out-of-plane response of unreinforced masonry walls subjected to blasts. A methodological appraisal is used for the test methods, focusing on the preparation of the test items and test setup, the boundary conditions and failure mechanisms investigated, as well as the commonly employed measurement techniques. The survey on the modelling approaches includes key topics such as level of detail and cost, and reports strategies to model the wall and blast scenario. The review provides a thematic analysis of the available literature, aimed to assist the analyst in selecting a suitable tool for the investigation of masonry in the field of blast engineering. Furthermore, the findings presented herein can support amendments of existing codes and guidelines pertaining to the design of protective masonry structures.

Natural frequencies, damping ratios and mode shapes of a prefabricated timber floor element have been assessed experimentally in laboratory with different boundary conditions and in situ (in field) at different stages of construction. In laboratory the change in modal parameters was studied with free-free boundary conditions and simply supported on two sides. Three different simply supported tests with changes in boundary conditions were carried out; the floor placed on the support without any fastening or interlayer between support and floor, the floor screwed to the supports and the floor placed on an elastic interlayer between support and floor. The in situ tests were carried out first on the single floor element and then on the entire floor of the room into which the floor element was built in. The damping ratio of the floor increased from 1% to 3% when simply supported in laboratory to approximately 5% when placed upon a polyurethane interlayer (Sylodyn®) in situ, and to approximately 6% when fully integrated in the building. Thus the in situconditions have considerable influence on the damping and the values assessed are very high in comparison with damping values suggested in design codes. Regarding natural frequencies it was concluded that the major change in these occur as the floor element is coupled to the adjacent elements and when partitions are built in the studied room, the largest effect is on those modes of vibration that are largely constrained in their movement.

In order to stabilise timber-framed buildings against lateral loads, the diaphragm action of roofs, floors and walls is often used. This paper deals with plastic analysis models for fully anchored sheathed shear walls. The models are based on the assumption of plastic load–slip relations for the sheathing-to-framing joints. Only static loads are considered. The basic structural behaviour and assumptions for the plastic models are elucidated. Both upper and lower bound methods are applied. The load-bearing capacity and the deformation of the shear walls in the ultimate and serviceability limit states, respectively, are derived. Both a discrete point description and a continuous flow per unit length modelling of the fasteners are discussed. Also, the forces and displacements of the fasteners and sheathing are derived. The influence of flexible framing members and shear deformations in the sheets, and also the effect of vertical loads on the shear wall, both with respect to tilting and second order effects, on the horizontal load-bearing capacity and displacement are evaluated. The stress distribution and the reaction forces at the ends of the different framing members are derived. The elastic model is experimentally verified and an illustrative example is given. The main objective of this work is to contribute to a better understanding of the structural behaviour of these fully anchored walls and form the basis for establishing a new plastic design method for partially anchored shear walls, i.e. a design method capable of analysing the more practical conditions of no or partial anchorage of the studs and/or bottom rail in real structures.

The rise of wood buildings in the skylines of cities forces structural dynamic and timber experts to team up to solve one of the new civil-engineering challenges, namely comfort at the higher levels, in light weight buildings, with respect to wind-induced vibrations. Large laminated timber structures with mechanical joints are exposed to turbulent horizontal excitation with most of the wind energy blowing around the lowest resonance frequencies of 50 to 150 m tall buildings. Good knowledge of the spatial distribution of mass, stiffness and damping is needed to predict and mitigate the sway in lighter, flexible buildings. This paper presents vibration tests and reductions of a detailed FE-model of a truss with dowel-type connections leading to models that will be useful for structural engineers. The models also enable further investigations about the parameters of the slotted-in steel plates and dowels connections governing the dynamical response of timber trusses. © 2022 The Author(s)

The Pacific Earthquake Engineering Research (PEER) Center's Performance Based Earthquake Engineering (PBEE) framework is well documented. The framework is a linear methodology which is based upon obtaining in turn output from each of the following analyses: hazard analysis; structural analysis; loss analysis, and finally decision making based on variables of interest, such as downtime or cost to repair. The strength of the framework is in its linearity, its clear flexibility and in the consideration of uncertainty at every stage of the analysis. The framework has potential applications to other forms of extreme loading; however in order for this to be achieved the 'mapping' of the framework to the analysis of structures for other loading situations must be successful.This paper illustrates one such 'mapping' of the framework for Performance Based Fire Engineering (PBFE) of structures. Using a combination of simple analytical techniques and codified methods as well as random sampling techniques to develop a range of response records, the PEER framework is followed to illustrate its application to structural fire engineering. The end result is a successful application of the earthquake framework to fire which highlights both the assumptions which are inherent in the performance based design framework as well as subjects of future research which will allow more confidence in the design of structures for fire using performance based techniques.This article describes the PEER framework applied to structural earthquake design then follows the framework from start to completion applying suitable alternative tools to perform each stage of the analysis for structures in fire.

High performance concrete (HPC) is a quite novel material which has been rapidly developed in the last few decades. It exhibits superior mechanical properties and durability comparing to normal concrete. HPC can achieve also superior tensile performance if strong fibres (steel or carbon) are implemented in the matrix. Thus, there exist the unabated interest in studying how the addition of different types of fibres modifies the behaviour of HPC. Nowadays, a standard numerical approaches to model the behaviour of fibre reinforced concrete (FRC) are carried out by means of the smeared or discrete crack modelling of homogenous media with appropriately changed stress-strain relationships. The objective of this paper is to develop a new and efficient mesoscale modelling approach for steel fibre reinforced high-performance concrete. The main idea of presented approach is to assume the fully 3D modelling with taking into account explicitly the distribution and orientation of the steel fibres. As a benchmark, results obtained from experimental campaign on beams and panels made from high-performance concrete with steel fibres of different sizes and dosages were taken. Results of numerical simulations were directly compared with experimental outcomes in order to validate and calibrate FE-model and to introduce the efficient numerical modelling tool.

The purpose of this paper is to numerically simulate the in-plane behaviour of rammed earth walls under cyclic shear-compression tests. The experimental testing allowed obtaining the maximum horizontal loads, the displacement capacity and the level of non-linear behaviour of the respective load-displacement relationships as well as the failure modes. The calibration of the numerical model (finite element method) was carried out based on the experimental results. Within this framework, a micro-modelling approach was considered. The behaviour of the rammed earth material was simulated using a total strain rotating crack model. A Mohr-Coulomb failure criterion was used to reproduce the behaviour of the interfaces between the layers. Although the numerical results achieved a satisfactory agreement with the experimental results a sensitivity analysis of the parameters involved was performed. The sensitivity analysis aimed at determining which parameters of the model have a significant impact in the model's results. As expected the sensitivity analysis pointed out that the sliding failure occurrence is mainly influenced by two parameters of the interface elements: the interface tensile strength fit and the friction angle φ. Moreover the cohesion c and the layers thickness showed a limited effect on the shear behaviour. It should be noted that the results mentioned above are related to the cases where a significant level of vertical compressive stress σ is employed.

The current paper focuses on the determination of reliable numerical models of earth block masonry wallettes under different loading conditions. Uniaxial compression and diagonal compression tests were performed. Experimental behaviour was modelled with a non-linear model able to describe the cracking behaviour. The simplified approach based on macro-modelling shows a satisfactory accuracy and low computational costs. The results reproducing the uniaxial compression are in good correspondence with the post-elastic behaviour observed in the experimental campaign. The micro-modelling approach adopted to reproduce the shear behaviour, even with high computational cost, represents a suitable tool to predict the masonry collapse mechanism.

In recent years, research has shown that the lower frequency portion of impact sound, down to 20 Hz, is of significant importance to residents’ perception in buildings that have lightweight timber floors. At low frequencies, the finite element method is a useful tool for predictive analysis. Impact sound frequency response functions, which are easily calculated using finite element software, are useful as they offer a common ground for studies of correlations between measurements and analyzes. On the measurement side, the tapping machine is well defined and has become the standard excitation device for building acoustics. When using a tapping machine, the excitation force spectrum generated – necessary to achieving experimental frequency force to sound response functions – is unknown. Different equipment may be used for excitation and force measurements and if a structure behaves linearly, the use of any excitation devices should result in the same frequency response functions. Here, an ISO tapping machine hammer is fitted with an accelerometer, enabling estimates of input force spectra. In combination with measurements of the sound in the receiver room, frequency response functions are then achieved using an ISO tapping machine. Various excitation devices have been used on a floor partition in a timber building and on a cross-laminated timber (CLT) lab. floor in order to compare the resulting frequency response functions. Structural nonlinearities are evident, implying that for accurate frequency response measurements in acoustically low frequencies, excitation magnitudes and characteristics that are similar to these which stem from human excitations, should preferably be used.

Fires can cause substantial damage to structures, both non-structural and structural, with economic losses of almost 1% GDP in developed countries. Whilst design codes allow engineers to design for the primary design driver, property protection is rarely, if ever, designed for. Quantification and design around property protection has been used for some time in the seismic community, particularly the PEER framework and fragility analyses. Fragility concepts have now started to be researched predominantly for steel-composite structures, however, there has been little to no research into the quantification of property protection for concrete structures, whether in design or in post-fire assessments of fire damaged structures. This paper presents selected results from the thermal environment around, and the thermal response of, a concrete column from a large scale structural fire test conducted in Tisova, Czech Republic, inside a four-storey concrete frame building, with concrete and composite deck floors. From the results of the fire test, assessments of the fire intensity are made and used to model the potential thermal profiles within the concrete column and the implications that high temperature might have on the post-fire response of the concrete column. These thermal profiles are then used to assess the reduction of the columns cross-sectional area and are compared to a quantified damage scale for concrete columns exposed to fire. This analyses presented herein will also show that common methods of defining fire intensity through equivalent fire durations do not appropriately account for the complexities of the thermal and structural response of concrete columns exposed to a travelling fire

A Multi-Level Assessment Strategy has previously been proposed and proved feasible for structural analysis of existing RC slabs. In this paper, the Multi-Level Assessment Strategy, which focuses on sophisticated structural analysis, was used to investigate the load-carrying capacity and structural behaviour of a composite bridge with an RC bridge deck slab subjected to a concentrated load. In addition to more sophisticated structural analysis, improved knowledge content about the structure and more advanced models for uncertainty consideration were also incorporated in a systematic way for higher levels of assessment. Furthermore, a decision support system was adopted, in which the cost for different alternatives regarding if and how the assessment should be enhanced with respect to model sophistication, knowledge content and modelling uncertainty were compared in a systematic way. The results show not only that the load-carrying capacity and the structural behaviour can be assessed with different level of detailing, but also that the cost for each level of assessment can be evaluated with a decision support system, facilitating more sustainable management of infrastructure. 

Analyses of tested two-way reinforced concrete (RC) slabs were carried out with varying modelling choices to develop better modelling strategies. The aim was to study how accurately the response of a slab subjected to bending could be predicted with nonlinear finite element (FE) analysis using three-dimensional (3D) continuum elements, and how the modelling choices might influence the analysis results. The load-carrying capacity, load-deflection response, crack pattern and reaction-force distribution of the two-way slab studied were compared to experimental data available. The influence of several modelling parameters was investigated, including geometric nonlinearity, element properties, concrete model, reinforcement model and boundary condition. The results show the possibility of accurately reflecting the experimental results concerning load-carrying capacity, load-deflection response and crack pattern giving proper modelling choices. Moreover, the reaction force distribution was found to be highly influenced by the stiffness of the supports.

Failure of reinforced concrete (RC) slabs without shear reinforcement in punching has been a challenging problem for nonlinear finite element (FE) analysis. To improve the analysis approach, this study was conducted by developing a nonlinear FE analysis method for slabs subjected to punching failure without shear reinforcement, using three-dimensional continuum elements. The influence of several modelling choices were investigated by comparing such results as loadcarrying capacity, load-deflection response and crack pattern from the FE analyses with available experimental data. The proposed method shows the possibility of accurately predicting the load-carrying capacity and realistically describing the behaviour of slabs.

Corrosion of reinforcement affects anchorage capacity. In this study, four levels of analyses were, for the first time, compared with each other and to tests of naturally corroded beams. In the most advanced approach, three-dimensional non-linear finite element (3D NLFE) analyses employing previously developed bond and corrosion models were carried out. These analyses agreed well with the experiments in terms of crack pattern and maximum load capacity. The next approach consisted of 3D NLFE analyses with a pre-defined bond-slip relation between concrete and reinforcement, resulting in reasonable agreement; however, the anchorage capacity was overestimated and the crack pattern deviated from the experiments. At the next level, the bond-slip relation was used together with a measured available anchorage length, and the anchorage capacity was obtained by numerically solving the one-dimensional differential equation; the results were reasonably close to the experiments. In the most simplified approach, a constant bond stress was assumed together with the available anchorage length measured, which underestimated the capacities. In conclusion, the more advanced analyses provide reliable information regarding the structural behaviour, while the two simplified methods are well suited for use in practice.

This paper focuses on a particular application of birch plywood in adhesively bonded connections, namely, a node of a timber truss. The aim is to investigate the influence of the plywood’s additional width and the load-to-face grain angles on its load-bearing capacity in tension (tensile capacity). The experimental tests started from the case with the plywood width the same as the glulam width. The reference tensile strengths tested from the specimens with a small gap between glulam elements are high at any load-to-face grain angle, i.e., around 51 MPa, 44 MPa, and 41 MPa at 0°, 22.5°, and 45° to the face grain respectively, due to the changed crack paths of the 22.5° and 45° plywood. The very low angle-dependent tensile strength is unique for cross-grained veneer-based panels in adhesively bonded connections, and is promising for applications in truss nodes. With the increase of the plywood width, the tensile capacity of birch plywood tended to reach a plateau. Test results indicated a low angle-dependence of the maximum tensile capacities of birch plywood but the plateaus were reached at different plywood widths. This phenomenon can be well interpreted by introducing the concept of effective widths and spreading angles. The specific spreading angles were determined by comparing the predicted tensile capacity to the test results, which should be valid for adhesively bonded birch plywood plates in truss nodes irrespective of the geometrical parameters. 

The design of timber connections is of vital importance in timber structures. Bonded connections exhibit the advantages of lower cost, higher load-bearing capacity, and higher stiffness compared to conventional mechanical connections. However, the potential of the bonded connections has yet to be fully exploited, not only due to their sensitivity to the adhesive types and process-related parameters but also due to the lack of studies regarding the structural performance of the bonded connection in various loading conditions. In this paper, birch plywood plates were utilized to adhesively connect two glulam beam halves to create a longer span. Plywood made of birch was chosen because birch is highly resourced on the Eurasian continent, with its mechanical properties better than most softwoods. Specifically, glulam beams were connected by birch plywood plates at mid-span and then loaded in four-point bending. Four test series with two different bonding areas and birch plywood face grain orientations were carried out. The bonded region was designed as the weakest part to investigate the failure modes, moment capacity, bending stiffness, and moment-rotation angle relationships. Furthermore, numerical models were developed to predict the structural behaviors in the linear elastic stage, while analytical models were proposed and subsequently modified to predict the moment-carrying capacities. Both numerical and analytical models displayed satisfactory agreement with the test results.

This study investigates frame corner joints built of birch plywood plates and glulam elements connected via self-tapping screws. Analytical calculations based on the fastener group’s torsional moment resistance, the proposed fastener group’s elastic and post-elastic load-bearing criteria, and the design formulas in Eurocode 5 were performed to predict the connection capacity in both elastic and post-elastic stages. A combined action check formula was adopted to predict the capacity of birch plywood plates and glulam elements. Frame corner specimens constructed with three different plywood thicknesses were planned to study the influence on global behavior and rotational stiffness. The specimens were intentionally designed so that failure occurred either in plywood or in glulam, in order to examine the robustness and validity of analytical calculation models. Another supplementary test group with 21 mm plywood and fewer fasteners was also designed and tested, in which the plastic yield of fasteners was expected. The test results of this supplementary group served to calibrate the analytical model that predicts the elastic and post-elastic capacity of the connection group. As a result of the comparison, the analytical calculations gave reasonable predictions on the failure of plywood, glulam, and the capacity of the fastener group. Only when the exposed moment exceeded the post-elastic limit of the fastener group did the plastic yielding of fasteners become observable. Moreover, numerical finite element models adopting the foundation zone-modeling scheme were constructed, which were proven to capture all test configurations’ linear loading stiffness satisfactorily.