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In order to improve structural efficiency, environmental performance, and constructability, a new type of one-way composite voided slab system (TUBEDECK) has been recently proposed which combines profiled steel decks with cast-in-situ RC slabs. Because eliminating concrete volume to optimize flexural strength can significantly reduce the shear strength of nonprestressed concrete or composite slabs without shear reinforcement, a clarification of the shear resistance capacity is required. In this study, shear tests on a total of 12 specimens were conducted with slab thickness, the presence or absence of voids and/or steel decks, and tension reinforcement ratio as variables. The results show that combined flexure and shear dominated the behavior of both voided (V) slabs and TUBEDECK (TD) slabs, and web-shear cracking did not affect strength. Predicted shear strength based on the minimum web width was too conservative. Conversely, the shear strength prediction equations, which were proposed on the basis of the real cross-sectional area of concrete, predicted the capacity of both V slabs and TD slabs from a reasonably conservative perspective. A discussion on the influence of moment–shear interaction is also included, and an interaction design model is proposed in a further investigation.

To explore the application of environmental protection material-paper straw board in cold-formed thin-walled steel (CFS) structures and further develop the sheathing system, an innovative CFS framing wall sheathed by paper straw board (CFSSB) is proposed. Eight CFSSB composite wall specimens and one CFS frame without sheathing were tested under monotonic and reversed cyclic horizontal loads to study the shear performance of the CFSSB composite wall. Also, the shear performance of the wall specimens can be obtained. The key parameters include the value of the vertical load and the form of the CFS frame in this experimental program. By analyzing the specimen’s failure forms and failure process, the characteristic values of the bearing capacity, lateral stiffness, ductility coefficient and energy dissipation coefficient are obtained. The results show that the existence of paper straw board and adding diagonal braces to the CFS frame can significantly improve the shear capacity of CFSSB composite walls. The favorable seismic performance of the CFSSB composite wall was demonstrated in the experiment. In addition, a finite element model for CFSSB composite wall is developed using the software package ANSYS. The finite element analysis (FEA) results show a good agreement with the experiment results in terms of failure modes and skeleton curves, which verify the feasibility of the FEA model. Furthermore, extensive parametric analysis was carried out to analyze the factors affecting the shear capacity of the CFSSB composite wall. The FEA results show that the spacing of studs and self-tapping screws greatly influences the shear capacity of walls. Moreover, based on the failure of the screw connections, a formula for calculating the shear capacity of the CFSSB composite wall is proposed. The results of the formula calculation show good agreement with the experiment and FEA results, and it can provide a reference for engineering design.

In the aforementioned paper, optimum design of tuned mass dampers (TMD) installed on multiple degree of freedom (MDOF) structures under seismic excitations is proposed. Equations of motion for structures with and without TMD were solved by the modal analysis procedure. Results of numerical studies in this discussion show that using modal method for solving the differential equations governing the motion of controlled structures by TMD dampers usually is not corrected because such systems essentially have not classical damping.

In the aforementioned paper, the optimum parameters of tuned mass dampers (TMD) are determined by the Harmony search (HS) algorithm in multiple degree of freedom (MDOF) structures under seismic excitations. The proposed approach is original; however, the mechanical model for the damped structure is not in agreement with previous results reported in the literature. Thus, the main focus of this discussion is to highlight the differences and analyze the impact on the obtained results.

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The dynamic response of hyperbolic cooling towers on soils are calculated in this paper based on a dynamic region-wise variational principle and the modes of free vibrations reported elsewhere by the authors. The spectrum method of random vibration theory and wind load data from full-scale measurements are used. Gust factors for hyperbolic cooling towers and footings on different soils are presented.

In this study, a series of new beam-column connections was proposed for large-span steel hyperbolic towers. The mechanical performance of the connections under an out-of-plane bending moment and a shear force was studied via experimental tests and numerical simulation. Different parameters such as the connector type, row number of the bolts, and plate thickness were considered during the study. The moment–rotation curves and main failure modes of the connections were obtained and discussed in detail. The results showed that the new beam-column connections proposed in this paper had excellent bending stiffness and ultimate bending capacities. In addition, the finite element model of the connections was established by ABAQUS software, and the experimental and numerical results were compared. The comparison results showed that the numerical model could predict the moment–rotation curve and different failure modes accurately. The new joint system and study presented in this paper are relevant references for the study of large-span steel hyperbolic towers, which are increasingly becoming the prominent options compared with concrete cooling towers.

This paper presents outcomes of experimental and numerical studies completed on unreinforced, collar plate reinforced and doubler plate reinforced Square Hollow Section (SHS) T-joints subjected to axial compressive loading on the brace member. A total of nine full-scale SHS T-joint specimens were fabricated and tested, in which six specimens were reinforced with collar plate and doubler plate. Non-linear finite element (FE) models were developed using finite element code, ABAQUS. Test data was used to validate these FE models. Subsequently, validated FE models were used to conduct an extensive parametric study to investigate the effect of various geometrical parameters of main members and reinforcement plates on the ultimate capacity of reinforced SHS T-joints. The parametric study found that use of both collar and doubler plate reinforcements significantly increase the ultimate capacity of SHS T-joints. Thickness of the reinforcing plate has a positive effect if the thickness of the reinforcing plate is limited to twice the thickness of the chord member. This study, however, found that the capacity of a reinforced SHS T-joint is not dependent on the type of reinforcing plate. The study concludes that the maximum capacity that can be achieved from a reinforced joint is about double the capacity of a similar unreinforced joint. It was found that the Eurocode EN 1993-1-8 overestimates the capacity of reinforced SHS T-joints. Therefore, a new design method for predicting the ultimate capacity of the collar plate and doubler plate reinforced SHS T-joints was developed and this new design method is presented in this paper.

This paper describes quasi-static cyclic shear-compression tests on six plastered single-leaf stone masonry walls. Of the six walls, four are tested under different axial load ratios, performing a cyclic load history with two cycles per increasing drift demand. Three are tested under the same axial load ratio but are subjected to different load histories, namely, one monotonic loading, one cyclic loading with two cycles per drift level and one cyclic loading with one hundred cycles per drift level. Stiffness, force capacity and drift measures corresponding to six different limit states of the walls are extracted from each test and the effect of the axial load ratio and of the load history on these parameters is investigated. Changing the axial load ratio on the tested walls confirms findings from previous studies, according to which, with increasing axial load the wall stiffness and the force capacity increase while the ultimate drift decreases. Varying the number of cycles in the applied load history brings new findings, showing that all the drift measures of the walls, especially those corresponding to limit states attained in the post-peak regime, are very sensitive to the number of cycles applied while the stiffness and the force capacity are not. These trends are shown in the paper and compared against code and literature provisions for in-plane loaded walls. One face of each wall is plastered and the damage of the plaster is compared to the damage of the stone and mortar. This information is required when assessing the non-structural damage of the walls.

The underground ecological granary has the advantages of low temperature, heat insulation, safety, and mechanization operation of moving grain in and out of the granary. It is the most suitable environmentally friendly warehouse for long-term grain storage at present. Traditional underground granary supporting structures mostly use cement materials and present disadvantages including long periods of construction, difficulties in repairing cracks and leakages, and difficulties in demolition. Based on a steel skeleton supporting structure and flexible waterproof polymers, this paper proposed a new rigid-flexible composite recyclable supporting structure for underground storage granaries. Through the use of ABAQUS software, this paper established a three-dimensional finite element numerical model for excavation of the new supporting structure; analyzed stresses and deformations of the steel pile, middle beam, and steel plate and ground settlement at different excavation steps; and checked the stability of the new supporting structure. Additionally, considering a certain ecological storage granary in Zhongmou County of Henan Province, this paper developed a full-scale test for the new supporting structure. By monitoring the stresses of the supporting structure and ground settlement during excavation, it was concluded that the field monitoring results basically matched the results from numerical simulation. The new supporting structure has the advantages of good stability, quick construction, recyclable usage, low cost, and broad application prospects.

In the paper, a numerical procedure for investigation of slender reinforced concrete columns and steel-concrete composite columns at normal and high temperatures is presented. The procedure is based on sectional analysis and moment-curvature approach. Its applicability is illustrated on validation examples in which the results obtained by the simulations are compared with the test data given in literature. It is shown that the procedure provides sufficiently accurate results. The procedure was implemented in an in-house MATLAB code. The code is employed for the calculation of the examples presented in the paper. The code was also included in freely available scientific computer programs. The procedure is applicable for normal and high temperature conditions and for columns of symmetrical cross-sections of any type and shape. It is applicable in connection with any type of temperature-time curve, heat transfer model, and material models.

This paper presents the results of an experimental and numerical study on strapping method for retrofitting deficient interior RC beam-column joints, which do not meet the requirements of current seismic design codes due to some deficiencies including low strength of concrete, inadequate transverse reinforcements, and low construction quality. In order to explore the seismic behavior of the retrofitted RC joints, six interior joint specimens, including two deficient RC joints with inadequate transverse rebar, three RC joints retrofitted with prestressed high-strength steel strips and one RC joint retrofitted with adhesively-bonded steel and prestressed high-strength steel strips, were designed and tested under cyclic loading. The main variables included the retrofit methods, axial compression ratio and volume of steel strips. The test results indicated that the prestressed steel strips worked together well with the deficient RC joints, and the retrofitted specimens exhibited better seismic behavior than the deficient control specimens, especially in deformability and energy dissipation. On the basis of the experimental study, the corresponding numerical model was established using the Open System for Earthquake Engineering Simulation (OpenSEES) and then verified to be valid. Finally, the modified softened strut and tie model was proposed in this paper to calculate the shear capacities of the specimens, and the calculated results agreed well with the test results.

Past experimental studies have demonstrated that reinforced masonry shear walls (RMSWs) can provide adequate ductility and energy dissipation capacity when acting as the seismic force-resisting system in low-rise buildings. However, slender RMSWs used for these applications, characterized by high height-to-thickness (h/t) ratios, may be vulnerable to out-of-plane instability failure modes when subjected to in-plane seismic loading. Out-of-plane instability may develop when a wall end zone undergoes cycles of high tensile strain, followed by compressive strain during in-plane seismic loading. Out-of-plane instability has the potential to cause unexpected and rapid strength degradation, which can lead to a global collapse. Provisions of the Canadian masonry design standard CSA S304 currently aim to prevent out-of-plane instability by prescribing h/t restrictions. Relaxation provisions were introduced in CSA S304-14 for walls with flanges or boundary elements and for walls subjected to low axial stress, however these provisions have not been experimentally verified. Moreover, prescriptive h/t restrictions disregard many important factors that affect failure modes for RMSWs under in-plane reversed-cyclic loading, including the type of loading protocol (symmetrical or asymmetrical) and the effect of flanges for T-shaped walls. This paper presents a detailed experimental study on the influence of these latter two factors on the out-of-plane response of slender RMSWs subjected to in-plane cyclic loading. The testing program comprised three full-scale RMSW specimens (two T-shaped and one rectangular) subjected to reversed-cyclic loading. A displacement-controlled loading protocol was applied until the lateral load capacity of the specimen was reduced to 80% of its maximum value. The test specimens were designed to be vulnerable to out-of-plane instability, however, although significant out-of-plane displacements were observed in one of the tests, failure of the test specimens was not governed by out-of-plane instability. Detailed descriptions of the specimen responses and a discussion on the key factors affecting the out-of-plane instability failure modes are provided in the paper. The test results confirm that the out-of-plane behaviour of slender RMSWs is similar to reinforced concrete shear walls (RCSWs) in that it is significantly affected by the presence of boundary elements (e.g. [18] , [11] , [31] , [1] ) and the type of loading protocol (e.g. [23] , [24] ). This leads to the conclusion that seismic design and detailing provisions for preventing out-of-plane instability in RMSWs and RCSWs should consider these parameters.

This paper presents the partial internal forces method – a method for the assessment of the cross section capacity based on the plastic theory. The method is based on mechanical principles, promotes a fundamental understanding and is therefore very popular in education and engineering practice. A main advantage of the method is that it can easily take into account all internal forces and moments of steel members of arbitrary cross-sections. The basics of the method are presented for double symmetric I-sections without fillets. In principle, the allocation of the internal forces and moments to the individual partial elements, i.e. flanges and web, of the cross-section takes place, taking into account the equilibrium conditions. This results in partial internal forces and moments. The capacities of rectangular shaped partial elements define the limits of the partial internal forces and moments. Additionally, the paper compares different cross section verification methods (plastic linear interaction, interaction according to EN 1993-1-1 and a strain based approach) in form of the yield surfaces using different combinations of internal forces and moments. The results of the strain-based method are almost identical to those according to the partial internal forces method. Compared to the linear plastic interaction, the partial internal forces method facilitates more economic design results. EN 1993-1-1 provides simplified interaction formulae for specific internal force combinations. The approach may lead to non-conservative results compared to the partial internal forces method and the strain based approach.

The purpose of this paper is to quantify the extent of damage of rectangular reinforced concrete shear walls after an earthquake using surface crack patterns. One of the most important tasks after an earthquake is to assess the safety and classify the performance level of buildings. This assessment is usually performed by visual inspection that is prone to significant errors. In this research, an extensive database on the images of damaged rectangular reinforced concrete shear walls is collected from the literature. This database includes more than 200 images from experimental quasi-static cyclic tests. Using the concept of fractal geometry, several probabilistic models are developed by extracting and regenerating the surface crack patterns of the collected walls. These models can estimate the peak drift ratio that the structure has experienced. The peak drift ratio predicted by the proposed models of this paper can be used to calculate the probability of exceedance of different damage states using existing fragility models. Furthermore, new fragility models are directly developed using the images of the damaged walls of the collected database. The proposed fragility curves calculate the probability of exceedance of damage states using the crack pattern of the damaged shear walls and consequently provide an estimation of the loss, repair cost, and repair time of the walls.

This paper examines low cycle fatigue in seismically isolated regular (SIR) bridges, taking into account the steady-state vibrations due to the lateral force of vehicles or any other lateral impacts of a permanent character. Bridges are modeled as two-degree-of-freedom (TDOF) systems in which the force presents sinusoidal impact on the centre of gravity of the bridge superstructure. Inelastic stiffnesses and modal damping ratios for the column and isolation bearing are obtained using the rheological-dynamical analogy (RDA). The background of this inelastic theory is presented in the framework of a mathematical-physical analogy between the rheological model of viscoelastoplastic (VEP) material and dynamical model with viscous damping. To estimate quantitatively the influence of isolation material characteristics on damping, corresponding frequency response functions for bent column and isolation bearings in bridges are analyzed. In addition, the paper develops the real damping matrix, which includes effects of damages due to fatigue, using the modal damping matrix and taking account of mode orthogonality.

An important issue in structural health monitoring (SHM) is to develop appropriate algorithms that can explicitly extract meaningful changes in measurements due to structural anomalies, especially damage. However, the effects due to environmental factors, especially temperature variations may produce significant misinterpretations. Consequently, developing solutions to identify the structural anomaly, accounting for temperature influence, from measurements, is crucial and highly anticipated. This paper presents a Temperature-driven Moving Principal Component Analysis method, designated as Td-MPCA, for anomaly detection. The Td-MPCA introduces the idea of blind source separation (BSS) for thermal identification with intent to enhance the performance of Moving Principal Component Analysis (MPCA) for anomaly detection. To achieve this target, temperature-induced strain variations are first investigated and revealed by employing Independent Component Analysis based on maximization non-Gaussianity, also known as Fast ICA. Afterwards, the MPCA is adopted for anomaly detection on the separated temperature-related response. Three case studies are provided in this paper to evaluate the proposed method. The first one is a numerical truss bridge with a simulated 5% stiffness reduction. The results confirm that Td-MPCA is more sensitive than MPCA in detecting anomalies, where the simulated stiffness loss fails to be detected by MPCA. The second case study is on an experimental truss bridge where two damage scenarios are introduced and interpreted. The detection results show that Td-MPCA outperforms MPCA since the damage is identified at the expected time by Td-MPCA but not by MPCA. The third case study is an in-situ curved viaduct in Switzerland. Data acquired during both construction period and normal service period has been used for interpretation. Results demonstrate that Td-MPCA is able to identify the date of change in construction process without any delay when compared with the application of MPCA only.

A novel bridge repair method has been developed to strengthen steel bridge girders with section loss due to end corrosion. The repair comprises of welding headed shear studs to the non-corroded portion of the web plate and encasing them in ultra-high performance concrete (UHPC) to create an alternate bearing load path. The interaction between the headed studs and the UHPC panels is crucial in the force transfer. Therefore, a careful study is needed through high-fidelity finite element analysis to complement the experimental results. This paper presents the development of a model in Abaqus finite element software that enables capturing the behavior of studs embedded in UHPC. The model was validated using a series of experimental results from push-out tests with headed shear studs welded onto a thin web plate. Experimental results from push-out tests performed on stud diameters of 12, 16 and 19 mm and two levels of eccentric loadings were used to calibrate the modeling methodology. The model explicitly considers effects of material damage, contact between the studs and UHPC, and the precise geometry of the weld collar of studs. After validation, design parameters such as interaction of in-plane torsion and direct shear, and limits for web thickness-to-stud diameter ratio were studied to compliment the experimental data. The results are expected to inform engineers about the design of this novel repair method. In addition, this paper may enable future finite element studies on the performance of studs in UHPC.

The first part of the paper focuses on briefly presenting the background referring to the necessity of rehabilitating the heritage church buildings and to the general principles and strategies that dominate the rehabilitation processes and techniques. Also, some of the most important buildings that underwent through a base isolation process are exemplified, from ancient to present times, both world wide and in Romania. The second part of the paper presents a case study referring to the first historic heritage church building that was base isolated in Romania, St. Nicolae Aroneanu Orthodox Church, located in Iasi County. Being erected in 1594, the church follows the traditional orthodox architectural patterns of those times, from both esthetical and structural points of view. The rehabilitation necessity was imperative, since the church was severely damaged by numerous strong seismic actions during the last 400 years. After extensive and wide-ranging investigations and evaluations, the base isolation method was selected as the appropriate rehabilitation solution. The system consists in installing 48 friction pendulum sliding (FPS) isolators, between two horizontal reinforced concrete carrying elements that were casted at the infrastructure level, followed by decoupling the superstructure of the church from the existing foundation system and transferring it to the seismic isolators. Since it has never been previously applied to Romanian heritage church buildings, the execution process was divided into several technological stages, each of them being extensively discussed, by highlighting the advantages and drawbacks that arose. The main advantages that derived from applying the base isolation rehabilitation strategy refer to a considerably improved response of the structure to the high intensity seismic actions that are specific to the north-eastern part of Romania and to a significant reduction of the drift displacements and of the shear forces in the structural masonry walls. Nevertheless, by far the most important advantage consists in the fact that all necessary rehabilitation works are performed at the infrastructure level, without generating risks of damaging the heritage architectural and artistic components of the church.

The current recommendations given in the codes and guidelines for design of anchorages to concrete are limited in scope to rectangular and regular anchor groups with a maximum of three anchors in a row. Furthermore, several assumptions are made, which may render the designs conservative but may also lead to unconservative results such as the required base plate thickness and the cracked concrete assumption. The aim of this experimental study was to investigate the load-displacement behaviour of tension loaded anchor group configurations that are either only partly covered or not covered by the current design provisions. Furthermore, this work aimed to generate an experimental database on the concrete cone failure of anchor groups under tension loading. The results of a comprehensive experimental program carried out on diverse anchor group configurations within and beyond the scope of the European Standard EN1992-4 are discussed focusing on several aspects such as (i) different geometric configurations, (ii) varying stiffness of the base plate, and (iii) influence of eccentricity. The experimental program contains tests on single anchors and on anchor groups in normal- and high-strength concrete. The testing concept, test setup and the test results are discussed in detail in this paper. Based on the evaluation of the test results presented here, a new analytical model is being developed for the concrete cone failure mode of tension loaded anchor groups that will be presented in a future paper.

Prefabricated steel structure is widely used as a kind of green building structure with life cycle significance. As the key link in steel structure design, the beam-column joint design has been deeply studied. Based on this, the paper proposes earthquake-resilient prefabricated steel beam-column joints (PSBCJs) with different connection forms. The main components of the joints are circle tubular steel column with cantilever beam and common I-beam, and the differences are the change of connection forms of flanges and webs. In this paper, five specimens were designed, and the low-cycle reciprocating test and numerical simulation were carried out on these specimens and the corresponding repaired specimens. The parameters such as the forms of flange cover plates, the forms of connecting plates, the middle bolts interval and the influence of the earthquake-resilient behavior on the mechanical properties of the joints are investigated, and the load-displacement curves, skeleton curves and damage models of each specimen are obtained. Test results and numerical analysis were mutually verified. The results of the tests showed that the new PSBCJs can effectively dissipate energy through the plastic deformation of the flange cover plates; the middle bolts interval has a great influence on the bearing capacity and energy dissipation performance of the joints; under the premise of the same main structure, the reasonable changes of the connection forms of the flange cover plates and the web connectors have little effect on the deformation mode of PSBCJs; after the completion of the loading, the main components such as beams and columns are basically kept elastic, and the seismic performance of the joints after replacing the connection devices are still favorable.

The wind tunnel test of static aeroelastics is a basic method to study the static aeroelastic phenomena of aircraft and other similar structures. As the test objects, the static models need to meet similar requirements, such as geometric similarity and stiffness similarity. The traditional models adopt a spar-frame-skin hybrid structure. The multiple frame segments (skins) of the models are separated from each other, and it is difficult to ensure the geometrical similarity of the aerodynamic shapes of the models during the tests. The overall stiffness of the models with this structure is borne by the metal spars, which makes it difficult to design and manufacture the models. Replacing the segmented frame/skins in the hybrid structure, an integrated shell structure made of additive manufacturing technology (AM) that contributes partial stiffness is proposed in this paper. Based on the structure, a static aeroelastic model is designed in two phases: the similarity design and stiffness design. The stiffness design is formulated as a constrained single-objective optimization problem, and the gradient-based optimization algorithm is adopted to implement the optimization to obtained structural dimensions of the model in the hybrid structure. The errors of the stiffness design are checked and the contribution of integrated shell to the overall stiffness is discussed. A large-aspect-ratio aircraft is chosen as the prototype and a static aeroelastic model with the integrated resin shell is designed, calibrated, and tested in this paper. The results show that the static aeroelastic model with the proposed AM integrated shell is feasible and can be used to study the static aeroelastics reliably and efficiently.

Damage detection of civil engineering structures relies heavily on the use of outlier analysis/novelty detection analysis. Generally, data captured from a structure in its normal environmental condition are used to create a model and compute control limits to represent the normal range of variations of damage sensitive features of the structure. However, the training database used usually includes outlier measurements, which may introduce masking effect. These outlier measurements can affect the mean and standard deviation/covariance matrix of the training database, and hence, affect the model and the control limits. As a result, small damage may not be detected. Therefore, this paper proposes an approach of selecting a ‘clean’ training database for the construction of the baseline of the undamaged structure so as to detect damage at an earlier stage. The approach makes use of Principal Component Analysis and Median Absolute Deviation to identify outlier measurements. This approach can be applied before the application of damage detection methods to allow damage to be detected at an earlier stage. The proposed approach is applied to a numerical beam model and the Z24 Bridge, in Switzerland. The results obtained demonstrate that damage can be detected at an earlier stage using the approach proposed in this paper. The proposed method also allows the determination of the model (e.g. linear or nonlinear) to be used for damage detection.

The popularity of steel modular construction is on the rise. This paper presents a new and innovative modular steel construction which uses state-of-the-art cast-steel connectors and hollow structural steel members. Structural behavior of a typical corner connection of this modular construction to be used in an assisted living facility was studied when the connection is subject to axial tension and axial compression loads. The study was completed using both experimental method and a numerical method. Six full-scale specimens were built and tested under axial compression and axial tension. It was found that this innovative modular connection satisfactorily carries the design loads. Based on the parametric study completed using finite element method, two significant design improvements are recommended. The cast-steel connector can be made 20% lighter without compromising the strength needed to satisfy the design loads. The locations of the connecting screws can be adjusted to achieve a higher stiffness and load carrying capacity of the connection when subjected to axial tension. This paper presents the new modular construction method in brief, the test method and test results, development of finite element model, and parametric study.

This paper presents an advanced finite element analysis (FEA) model to predict the fire behaviour of concrete-encased concrete-filled steel tube (CSFT) columns. The sequentially coupled thermal-stress analysis method provided in the software package ABAQUS was used. Full-range fire simulation given in this paper included four phases, i.e. loading (to a certain load level) at ambient temperature, standard fire exposure (heating) with the load applied, cooling down phase and postfire loading up to final failure. Calibrated empirical models for steel tube, unconfined and confined concrete (confined by steel tube and by reinforcement, respectively) over the four phases were chosen separately and applied to the FEA model. Numerical results from the model were compared with previously reported results of the experiments on the concrete-encased CFST columns, in terms of ultimate strength at ambient temperature, temperature field, failure modes, fire resistance, axial deformation versus time relationships, load versus axial deformation relationships and postfire residual strength. It is found that acceptable agreement was reached between the predictions and experimental observations, although some aspects could be further improved. Sensitivity analyses on several identified parameters of the modelling were conducted. Recommendations on simulating the full range fire behaviour of concrete-encased CFST columns were proposed based on the numerical study presented in this paper. In addition, the calculated internal force of the tested specimens was extracted and analysed, which confirmed the design concept of the composite action of concrete-encased CFST columns in fire.

Concrete-filled double-skin FRP tubes (CFDST) are increasingly attracting researchers’ interests due to the advantages of their reduced self-weight and higher bending stiffness than fully filled tubes. However, the structural behaviour of CFDST, especially the non-uniform confinement in annular concrete, has not ever been well addressed. This paper presents an analytic study on axial compressed circular stub CFDST with FRP wrap/tube as outer tube and steel/FRP as inner tube. Based on existing studies on actively confined concrete, a constitutive model for non-uniformly FRP-confined concrete is developed in this paper. The dilation model for concrete fully filled FRP tubes is modified to account for the effects of void ratio so that the hoop-axial strain curve of CFDST could be reasonably predicted. Behaviours of steel and FRP tubes in CFDST are investigated and proper stress-strain models are proposed to estimate the loads shared by tubes. The stress state in annular concrete is theoretically studied by dividing the cross-section into multiple circular layers. Finally, an analysis-oriented load-strain model, which accounts for the non-uniform confinement, effects of void ratio, buckling of FRP tube, and strain hardening of stainless steel, is proposed for CFDST. As validated by the experimental data from a wide range of literature, the proposed model is reasonable and of high accuracy.

This paper focuses on a new type of precast sandwich wall panels in which the expanded polystyrene (known as EPS) insulation layers are inserted between exterior reinforced concrete panels. The exterior reinforced concrete panels are held through diagonal steel bars to allow the sandwich panel to form the composite action to resist the bending moment demands. To investigate flexural behavior of the sandwich wall panels, four specimens with representative geometries and typical materials were designed. The four specimens included one with the flat exterior reinforced concrete panels and three with the ribbed exterior reinforced concrete panels. The specimens were tested using gradually increased uniformly distributed loads. It is found that all the specimens developed the composite action when resisting the bending moment demands and exhibited the same failure mode. Test results show that the specimens consisting of the ribbed exterior reinforced concrete panels (which had lower mass per unit volume) exhibited reduced flexural resistances at the cracking limit state and the ultimate limit state in comparison with the one with flat exterior reinforced concrete panels. This paper develops a set of analytical models based on the test data and simplified strain/stress diagrams for analyzing flexural behavior of the proposed sandwich wall panel. Result comparisons show that the models can provide reasonable predictions and they can be used for future practice.

Single-blade installation is a popular method for installing blades on bottom-fixed offshore wind turbines. A jack-up crane vessel is often employed, and individual blades with their roots equipped with mechanical joints and bolted connections are lifted to the tower-top height and mated with a pre-assembled hub. The final mating phase is challenging and faces significant risks of impact. Due to relative motions between the blade and the hub, substantial impact forces may arise and lead to severe structural damages at root connections, thereby causing delays in the installation task. The present paper considers a realistic scenario of the mating process and investigates the consequences of such impact loads. Here, a single-blade model with tugger lines and a monopile model were established using a multi-body formulation, and relative velocities under collinear wave and wind conditions were obtained. A three-dimensional finite element model was developed for the blade root with T-bolt connections, and an impact investigation was performed for the case in which a guiding connection impacts the hub. The results show severe bending and plastic deformation of the guide pin bolt together with failure of the adjoining composite laminate at the root connection. Based on the type of damage obtained for the different environmental conditions considered, this paper also discusses its consequence on the installation tasks and suggests onboard decision making in case of an impact incident. The results of this study provide new insights regarding the mating phase and can be utilised to establish response-based operational limits.

The geometry of shell structures plays an essential role in their capacity to withstand earthquakes. However seismic loading is rarely considered when determining the overall geometry of shells. This paper presents a novel form finding methodology for the conceptual seismic design of corrugated shells. The method ensures that a compression load path exists to carry lateral earthquake accelerations by deriving shell geometries from a series of funicular polygons obtained through a graphic statics procedure for combined gravity and horizontal loads. While the method can be applied to any material that resists compressive stresses, it is employed in this paper to find the shapes of corrugated thin-tile masonry shells. Non-linear pushover analysis is then used to quantify lateral capacity and evaluate form finding results in terms of material efficiency to resist lateral loads. The analysis furthermore provides insights regarding the collapse mechanisms and flow of forces. It is demonstrated that the lateral capacity before cracking in the corrugated shell shapes is up to 79% higher than the capacity of a non-form-found reference shell shapes considering identical material use. All form-found shells were found to fail through a similar collapse mechanism which is defined by four crack zones. The location of these crack zones can be manipulated through the form finding process and identify the locations where reinforcement could be most efficiently introduced. Finally, the flow of forces within the form-found shells is used to propose alternative designs that provide additional openings in the shell surface while maintaining similar seismic capacity. Thus, the paper provides a new approach for the conceptual design of safe corrugated shell structures in earthquake prone areas.

This paper presents an experimental program aimed at providing reliable and comprehensive experimental data for assessing the available models of predicting the shear deformation of diagonally-cracked reinforced concrete (RC) beams. The non-contact measuring technique, Digital Image Correlation (DIC), was used to monitor the full-field displacement and strain in the shear span of five RC beams with thin webs. Virtual measuring grids were created to measure the mean shear strain and other critical deformation results which reflects the mechanism of shear deformation after shear cracking (i.e. the principal compressive strain angle, the principal compressive strain, the mid-depth longitudinal strain and the mean vertical strain). The experimental mean shear strain and other critical deformation results were compared with the predictions with several available models. The comparison indicates the available models fail to reproduce the principal compressive strain angle, the mid-depth longitudinal strain and the mean vertical strain which constitute the key parameters in estimating the shear deformation after shear cracking. As a result, significant discrepancies in the shear deformation of the beams tested in this paper are observed between the experimental and calculated results. It is also found that the predicted shear deformation of a number of beam specimens tested by other researchers with the available models deviates considerably from the experimental results. In general, the existing models are not capable of providing accurate predictions of the shear deformation of RC beams and further investigation into this topic is needed.

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.

A national research project to investigate proper structural design methods for cross-laminated timber (CLT) buildings has been initiated by a subsidiary of the Ministry of Land, Infrastructure, Transport and Tourism of Japan since 2011. In the final stage of the project, shaking table tests were conducted for CLT buildings designed according to a proposed structural design procedure which confirmed damage limit state, safety limit state, allowable stress, and ductile factors, etc. This paper presents results of shaking table testing for full-scaled CLT building and a design procedure. The three different systems examined are buildings composed of narrow panels, wide panels with an edge tensile connection, and wide panels with an edge tensile connection for each no-window shear part. The focus of this paper is the building of narrow panels. This building system is suitable for midrise CLT building with high ductility produced through rocking. The structure was shown to behave well during severe strong motion as specified in the Japanese building standard law and to have survived the 1995 Kobe earthquake despite the occurrence of a compressive rupture in shear walls which are support elements against the vertical load. Story shear capacity calculated from a numerical model and element tests (such as connections) were safely evaluated; but to evaluate the capacity correctly, further research is required in the element and system levels. Though a variety of undetermined issues and challenges remains, the Building Standard Law and Notification for three different CLT construction systems was enforced in April 2016 to ensure the construction of safe CLT buildings.

The technical development and characterisation of deformed 6Al4V titanium reinforcing bars for concrete has been reported and the use of titanium reinforcing bars demonstrated. This paper describes aspects of reinforced concrete design using titanium reinforcing bars based on ACI practices. The stress-strain behaviour of titanium is similar to that of steel although titanium is half as stiff and twice as strong. A combination of ACI 318 provisions for strength and ACI 440.1R provisions for serviceability are recommended when designing with titanium. This paper describes the resulting hybrid design approach in the context of flexural design. A series of benchmark designs comparing comparable reinforced concrete slab and beam designs using A615 steel, GFRP and titanium reinforcing bars is presented. An additional benchmark design of a near surface mounted (NSM) titanium bar retrofit of a steel-reinforced concrete beam is presented. The hybrid design approach proposed provides initial recommendations for design of experimental and demonstration titanium-reinforced concrete structures and provides appropriate bases for comparing accepted reinforcing materials with novel material, specifically 6Al4V titanium reinforcing bars.

In performance-based structural fire engineering, “travelling fires” is being gradually accepted as an important fire boundary condition. However, its application is still limited by uncertainties in the selection of different design travelling fire parameters, resulting from the lack of relevant experimental data and corresponding validated structural finite element models which can be used with advanced travelling fire methodologies, e.g. the Extended Travelling Fire Methodology (ETFM) framework. This paper aims to fill this gap through modelling a prototype steel-composite floor structure (representing a “slice” of a large open-plan office), to investigate its true structural response under a wide range of travelling fire scenarios, with an emphasis on considering the effect of concrete slab in a 3D finite element model, using LS-DYNA. To ensure the credibility of this numerical study, the model was first validated against the experimental data of the structural response from the Veselí Travelling Fire Test. In the parametric studies, 32 cases were examined to investigate the thermal and structural response, related to the selection of key design parameters for travelling fires (i.e. fire spread rates, fuel load densities and inverse opening factors (IOF)); fire protection (i.e. different fire protection schemes and required fire resistance rating (FRR)), and the effect of slab specification (i.e. thicknesses and steel reinforcements).It was found that solely satisfying the critical temperature and deflection criteria for the structural members might not guarantee a sufficient structural design for travelling fire scenarios, and it is suggested that the steel stress utilisation should also be examined. Compared with the IOF, it appears that the selection of fire spread rates and fuel load densities are likely to be more critical in identifying the worst travelling fire scenario for the structural response with fire protection. Moreover, the global structural response under travelling fire is also affected by the combination of fire protection (i.e. equivalent FRR in this paper) and fire spread rate. Under a “slow” travelling fire (e.g. 0.5 mm/s) with increasing FRR, the failure of structural elements during the cooling phase was prevented effectively; however, under a relatively “fast” travelling fire (e.g. 2.5 mm/s, 12.5 mm/s), increasing FRR may not always improve the fire performance of the structure. This work also indicates that steel reinforcement ratio has a greater influence on structural response than slab thickness under travelling fires. Furthermore, the 3D finite element model is very important for structural fire analysis, not only due to the more conservative internal force captured by the 3D model (i.e. reduced by over 80 % on the 2D model in our case) thereby reproducing the collapse triggered by the failure of the connection under fire in general, but also the 3D model was able to better represent the deflection and the “internal force reversal” caused by travelling fires.

The wind energy sector is constantly looking for improving the efficiency of their facilities, including on offshore locations. Part of that strategy is the demand for increasingly larger offshore structures. This cannot be met only by simply upscaling existing solutions, as there are several reasons that prevent such a simple approach. Often the connections are decisive for the dimensioning of the load bearing structures. Novel approaches, as the one this paper presents, are necessary. To allow for even larger structures, a novel hybrid joint, which combines adhesive bonding with welding, is presented. The first part of this paper fully addressed the requirements, and allowed to select two suitable adhesives significantly differing in strength by a ratio of 10:1, and stiffness by a ratio 50:1. Based thereupon, this paper first addresses the design, and the corresponding manufacturing concept, which were fully simulated numerically. Time and effort put into these preliminary steps proved crucial, as it allowed implementing changes and adaptations that otherwise would have hampered the project. Due to its nature, it largely reduces complex, labour, and cost intensive welding operations on the legs of the jacket structure, and substitutes them by relative simple, fast, and cost-effective adhesive bonding. The solution devised offers an alternative to the complex welding on the primary structural elements, resulting notch stresses, and associated local weakening. Thus, the innovative approach relocated the critical section of the joint well outside the former welding seams, and capacity of the hybrid joint is now limited by that of the tubular elements under static and fatigue loading. This was validated at medium size, with samples scaled down to 1:10, and large scale, at 1:5, respectively.

This paper presents nonlinear finite element (FE) simulations to predict the structural behavior of simply supported reinforced concrete (RC) slabs retrofitted with carbon fiber reinforced polymer (CFRP) as externally bonded reinforcement (EBR) and subjected to the blast loads in order to evaluate the effectiveness of using the CFRP strips as EBR for blast protection. The objective of this paper is to develop detailed numerical models in order to predict the blast response of non-retrofitted and retrofitted RC slabs during the inbound and rebound phases. A plastic material model including the strain rate effects of the material and able to predict the cracks is used to model the concrete. An elasto-plastic material model and an elastic material model are used to model the steel reinforcement and the CFRP strips, respectively. The bond interface between concrete and CFRP strip is simulated using a special contact algorithm including the strain rate effect at the interface between concrete and CFRP strip with failure criteria. The numerical results are validated by experimental tests. The maximum deflections, crack distribution and strain evolution in the steel reinforcement and in the CFRP strips found by the numerical analysis are in good agreement with the experiments. The concrete material model gives a good prediction of the blast response of the RC slab with and without EBR. Increasing the amount of the CFRP strip reduces the maximum deflection at the mid span of the slabs and the strain distribution in the steel reinforcement and in the CFRP strip. Parametric studies with respect to CFRP width and CFRP thickness are performed in order to evaluate the effects on the blast response of the RC slabs.

In the last decade, damage-resisting reinforced concrete (RC) shear walls, which offer improved self-centering and damage properties compared to conventional RC shear walls, have become an attractive research trend in structural engineering. Recent studies have experimentally proved that damage-resisting RC shear walls that benefit from advanced materials and details sustain reduced permanent displacements and concrete damage, cracking and spalling, than contemporary code-compliant walls. However, the evidence is still scarce as the available experimental studies have only addressed single-story shear walls with a limited selection of length, height, axial loading, and reinforcement ratio due to financial and experimental constraints. Furthermore, most of the performed studies were focused on the “as is” performance of innovative walls that have been fitted with novel details without following explicit design guidelines for such shear walls. In this case, numerical models that closely capture the response of tested innovative RC walls can be used to overcome the mentioned limitations of experimental studies, making it possible to study several shear walls with various dimensions, reinforcement ratios, and axial loads. The present paper, first, discusses developing verified analysis models using the state-of-the-art RC finite element analysis software, VecTor2, and performing a parametric study on three types of self-centering shear walls with different aspect ratios, axial load ratios, and reinforcement ratios. Then, the paper shows how the obtained results can be used to develop a set of design criteria for the studied shear walls, which were detailed with a type of self-centering reinforcement consisting of either shape memory alloy bars, glass fiber reinforced polymer bars, or post-tensioned high-strength steel strands. Specifically, this paper discusses how the ductility, self-centering, energy dissipation, and stiffness in self-centering shear walls change with the geometric, reinforcement, and loading specifications of the walls. In addition, a design method and three graphical tools are presented in this paper to aid the design of self-centering, ductility, and stiffness properties of self-centering shear walls.

This paper focused on a new type of double-skin composite wall in which concrete-filled steel tubes are used as boundary elements, and steel-bar space trusses are used to stabilize the faceplates. The new composite wall is architecturally attractive and has some perceived advantages in strength and construction. However, limited knowledge exists regarding its behavior under the combined cyclic in-plane lateral load and axial compression. This paper reports the test results of five experimental specimens subjected to the intended combined loading. Among the tested specimens, four developed the preferred flexure-dominated limit state, while one developed the undesired shear-dominated limit state. The specimens with the flexure-dominated limit states exhibited ductile behavior up to the drift of 0.036 rad with minor strength degradations. It was found that local buckles in the faceplates of the composite wall did not compromise wall lateral resistance. The effect of using supplementary steel headed studs to stabilize faceplates is also addressed in the paper. Aside from the experimental work, a simplified model was established to compute the wall plastic moment and lateral resistance of the wall with the flexure-dominated limit state. Predictions from the model were found to agree well with the test results, suggesting the model can be used for future design and analysis of the composite wall.

The observation of the damage occurred to ancient masonry buildings is the necessary first step to understand the seismic behavior of the elements that compose them. Looking at the recent seismic events in Italy, a severe damage could be noticed on a wide range of historical buildings, in some cases even for low values of peak ground acceleration. In particular, the present paper focuses on ancient fortified architectures, characterizing the historic city centers and landscapes, investigating the seismic vulnerability of its most typical element: the merlon. The analysis of the observed damage on the fortified building typology, collected and catalogued in previous works, clearly points out that merlons are frequently damaged, particularly by out-of-plane mechanisms and even for low accelerations. Given the fact that these elements are particularly vulnerable and, at the same time, particularly meaningful from a historical and cultural point of view, the present work focuses specifically on the out-of-plane damage mechanisms suffered by these protruding elements, in order to better understand their behavior during earthquakes, to quantify their vulnerability and to provide simple instruments for their seismic protection. Indeed, though the collapse of merlons is rather common, it has received little attention in the literature. The present paper analyses both merlons on towers and on walls, in clay brick masonry or in stone masonry, and describes, through a parametric analysis, their behavior as the features change. A simple linear elastic model was adopted to identify the activation of the out of plane mechanisms, while the subsequent collapse was analyzed with a non-linear kinematic model. Moreover, appropriate filtering equations were chosen to modify the response spectrum at the ground, thus taking into consideration the seismic filtering effect exerted by the supporting wall or tower. The proposed procedure is discussed and validated by means of three different case studies: the San Felice sul Panaro Fortress (damaged in the Emilia 2012 earthquake), the Arquata del Tronto Fortress, and the Rancia Castle (both damaged in the 2016 Central Italy earthquake). By changing the parameters (geometries, materials, soil) between extreme but realistic values, the curves that relate the slenderness of the merlons to the PGA that leads to the activation of the mechanism (or collapse) are plotted. These graphs supply ranges of vulnerable conditions, representing a straightforward and reliable instrument, also for practitioners and public bodies in charge of heritage preservation, useful to define priority lists for interventions and to optimize the resources for the prevention of future damage.

The paper presents the research on reinforced concrete beams strengthened with pre-tensioned CFRP laminates under self-weigh only and self-weight and external preload. In the first part the results of experimental campaign (Kotynia et al., 2013) are briefly described and discussed. Next a two-dimensional plane stress model of beams was developed on the basis of experimental observation. The model takes into account the nonlinear behaviour of concrete, steel bars and the concrete-to-laminate interface. A new uncoupled interface model was developed and programmed in order to properly describe the concrete-to-laminate connection for severely cracked structures. Numerical simulations performed for the calibrated material parameters exhibit very good convergence with the experimental results. The analysis confirmed suitability of the model to predict behaviour of RC members strengthened in flexure with CFRP materials in the whole range of loading. Moreover, in this part of the paper the numerically obtained effectiveness of active strengthening in relation to general passive methods of strengthening RC members in flexure was analysed. The calculations show that prestressing increases load bearing capacity in comparison with passively strengthened elements. The second part of the paper contains parametric study of the effect of concrete class, steel ratio, CFRP laminate width and stiffness, maximum concrete-to-laminate bond strength, loading configuration and preloading on load-deflection behaviour and load capacity of actively strengthened beams. The performed parametric study considerably broadened the scope of the experimentally investigated cases by Kotynia et al. (2013).

Unbonded post-tensioning (PT) monostrands have traditionally been used in buildings to sustain monotonic loads on members subjected mainly to gravity loads. As a result, most of the technical information on commercially available unbonded PT anchorage systems focused only on applications for gravity-loaded members. Despite the recent experimental research efforts on the behavior of PT anchorages under earthquake-simulated demands, this information has not been well quantified in design documentation. Consequently, further research is needed on unbonded PT anchorages for their use in members subjected to seismic loads. This paper presents the results of a comprehensive experimental evaluation on the ultimate capacity of monostrand anchorages subjected to high-amplitude concentric and eccentric cyclic loads. In addition, this paper addresses the influence of anchorage type, loading patterns and strand size on the ultimate deformation capacity of these anchorages. Specimens consisted of monostrands assembled with anchorages at both ends. Two types of anchorages were tested. Moreover, seven-wire, uncoated, low-relaxation PT monostrands in two sizes were considered. Several cyclic loading conditions were applied, in order to evaluate the behavior of anchorages under different scenarios. The ultimate capacity of the specimens was dominated by a premature fracture of one or few wires inside the wedges and two types of wire fractures were recognized: (1) with little reduction in the wire cross-sectional area and (2) with a notable reduction in the wire cross-sectional area prior the fracture. It was also observed that increased number of wire fractures correlated with larger strain capacity in some specimens. In addition, it was observed that eccentric loads reduced the strain capacity by about 18% for eccentricities of 6% in some cases. The fracture of the specimens occurred at relatively small strains, with values as low as 1.4%. Therefore, strains in unbonded post-tensioned strands should be limited to about 1.0% when designing for seismic loads. Furthermore, an analytical model was proposed to evaluate the influence of anchorages in unbonded post-tensioning precast structures.

Nowadays, there are growing interests in vibration serviceability assessments of high buildings, slabs, metallic and timber structures, and composite footbridges. Indeed, new design trends of composite footbridges make them slender civil structures that may be affected by the load action of walking pedestrians resulting in large deflections or even uncomfortable vibrations. Furthermore, the presence of people on the footbridges cause the addition of mass to the structural system and due to the human bodýs ability to absorb vibrational energy, an increase in structural damping. In this paper, the interaction between pedestrian and structure is modelled using data from pedestrian characteristics and vibration data from a measured footbridge as a comparison basis. The novelty of the papers relies on the proposed new Biodynamic Synchronized Coupled Model (BSCM). It consists in a fully synchronized force model in the longitudinal and lateral direction of pedestrian’s movement and a biodynamic model (with parameters mass, damping and stiffness). This model is coupled to the structural FEM at the feet’s contact points. Pedestrians are treated as individuals with intrinsic kinetic and kinematic parameters following a measured correlation matrix obtained by the use of an especially designed force platform. Finally, the adequacy of the proposed model to represent the pedestrians as BSCM for the walking effects on the structure is investigated by experimentally measured vertical accelerations on a footbridge where two crowd densities, freely walking and synchronism of the pacing rate with continuous crossing are also investigated.

Ultra-high strength steels (UHSS) have significant potential applications in the engineering fields due to their unique specifications. In recent years, it has been experimentally shown that the post-fire stress-strain response of this material is highly dependent on the maximum steel temperature and the sustained load applied to it during fire. This paper employs the Bernstain-Bezier functions to present the relationship between the stress, strain, the maximum fire temperature and the sustained axial load ratio ( β ) for Grade 1200 UHSS cooled for fire temperatures to room temperature. The experimental results are used to verify and validate the proposed model throughout the paper. The model showed to be capable of not only interpolating the stress-strain curves, but also extrapolating them out of the range of the available experimental tests data. Also, taking advantage of the stress-strain-temperature response of the UHSS tested at elevated temperatures, the instantaneous stress-induced strain and consequently the creep strain of UHSS subjected to different constant sustained load values during transient fire are obtained.

This paper presents the details of experimental and numerical investigations on the behaviour and axial compression capacity of Carbon Fibre Reinforced Polymer (CFRP) strengthened cold-formed, short Square Hollow Section (SHS) steel columns. Initially, an experimental investigation consisting of seven test columns was conducted to investigate the influence of CFRP strengthening layout on the axial compression capacity of short SHS steel columns. In addition, the effect of CFRP wrapping end condition was also investigated. Experimental results showed that CFRPs are very effective in strengthening short SHS columns, where axial compression capacity enhancements up to 2.6 times were observed. Then a numerical simulation was implemented using ABAQUS by which CFRP and adhesive were modelled using continuum and cohesive elements deploying Hashin and cohesive law criteria. The finite element models were validated using experimental results and then used in a detailed parametric study. Using the finite element analysis results suitable improvements were proposed to the existing design equations available in the literature. Finally, a new set of design equations based on Direct Strength Method (DSM) is proposed in this paper to determine the axial compression capacity of CFRP strengthened SHS columns subjected to local buckling.

The Baixo Sabor dam is a concrete double-curvature arch dam, 123 m high, located in the north-east of Portugal, which is being monitored by a dynamic monitoring system that comprises 20 uniaxial accelerometers. The paper starts with the description of the structure and of the installed monitoring equipment, as well as the monitoring software used to process the data that is continuously retrieved from site through an internet connection. Then, the results obtained during the system’s first six months of operation are presented, which include the characterization of acceleration levels for major events, such as the opening of spillway gates after intense rain, and the evolution of the dam modal properties (natural frequencies, modal damping ratios and mode shapes) during the reservoir first filling. In particular, the continuous characterization of the dam modal properties during important variations of the water level is a very unique experimental result (up to the authors knowledge, this is the first journal paper describing the continuous tracking of the modal parameters of a dam during its first filling), which is particularly interesting for the calibration of numerical models that take into account water-structure interaction. Additionally, it should be noted that the accurate tracking of the modal properties, in quite demanding conditions motivated by the very low vibration levels, associated to the massive nature of the structure, and by the presence of harmonics induced by the turbines of the hydroelectric power plant, was only possible thanks to the use of a carefully designed installation and advanced processing methodologies. At the end of the paper, it is presented a comparison between the results estimated with ambient excitation and the ones obtained with a forced vibration test and also predicted by a numerical model that includes the water effect with the added mass technique.

This paper aims to develop two kinds of innovative precast steel reinforced concrete columns, which are partially precast steel reinforced concrete (PPSRC) columns and hollow precast steel reinforced concrete (HPSRC) columns. Both the two kinds of composite columns have precast reactive powder concrete (RPC) shells, and the PPSRC column has a cast-in-place column core. In this paper, a series of cyclic loading tests on 10 column specimens subjected to combined static axial loading and cyclic lateral loading were carried out to explore their seismic performances. All specimens were evaluated by the failure modes, hysteresis characteristics, strength and stiffness degradation, energy dissipation capacity and ductility. The effects of section shape, stirrup spacing, axial compression and concrete strength of cast-in-place inner-part were investigated in details. The experiment results indicated that the PPSRC columns exhibited more satisfactory seismic behavior than the HPSRC columns in terms of hysteretic behavior, strength degradation, ductility and energy dissipation, while their bearing capacities were almost identical under low axial compression. Steel fibers could effectively prevent the cracked concrete from spalling, therefore, the encased steel shape was efficiently confined by the surrounding concrete during the entire test process. Higher stirrup ratio and lower axial compression of the column leaded to more satisfactory energy dissipation capacity, stiffness degradation and higher ductility. Based on the plastic stress theory, the seismic bending moment capacity analysis was conducted, and the results obtained form the formulas agreed well with those from the experiments.