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Reliability-based design (RBD) can overcome some limitations and ambiguities in the partial factor design approach found in Eurocode 7 (EC7) and the load and resistance factor design (LRFD) method used in North America. The aim of this study is to show how RBD via the first-order reliability method (FORM) can complement LRFD and EC7 codes. Three geotechnical engineering examples are used to demonstrate that RBD-via-FORM can provide guidance to the partial factor design approach in situations with load-resistance duality, shear strength parameters with context-dependent sensitivities, parameters not covered in design codes, cross-correlated parameters, and designs aimed at a target reliability or failure probability. Insights from RBD-via-FORM are presented. The differences and similarities between the design points in RBD, partial factor, and LRFD methods are explained. Comparisons are made with Monte Carlo simulations, the mean-value first-order second-moment method, and the Bathurst–Javankhoshdel closed-form reliability index solution which is restricted to simple linear limit state performance functions with lognormally distributed load and resistance terms and bias factors. It is suggested that RBD-via-FORM can be conducted in tandem with EC7 and LRFD methods in order to overcome limitations and ambiguities which sometimes arise using these methods.

Slope reliability analysis can effectively account for uncertainties involved in a slope system. However, commonly used slope reliability analysis methods often require huge computational cost, especially in large-scale problems, which hinders its wide application to engineering practice. This paper proposes an efficient slope reliability analysis method based on the active learning support vector machine (SVM) and Monte Carlo simulation (MCS). The proposed method makes use of an active learning function and cross-validation techniques to select the most suitable training samples to update the SVM model. The selected training samples are associated with a small distance to the limit state surface of the slope stability model and a large local uncertainty, which are more informative to gradually tune the SVM model to approximate the actual slope performance function. As a result, the proposed method can estimate the slope reliability with a small number of evaluations of the slope performance function, thus improving the efficiency significantly. Four slope examples are employed to demonstrate the effectiveness of the proposed method. The presented approach is also compared with some other commonly used surrogate models in slope reliability analysis. It is shown that the proposed method performs better in terms of computational efficiency to obtain similar estimation accuracy of the failure probability for the investigated examples.

Based on the first-order second-moment method, a comparative study on seismic fragility analysis with consideration of modeling uncertainty is carried out for a 12-story reinforced concrete frame structure under excitation with far-field and pulse-like near-field ground motions by using the multiple stripes analysis method. The sensitivity of the median fragility capacity of the building to fourteen parameters in the cases of three limit states (i.e., immediate occupancy, life safety, and collapse prevention) is analysed, and the effect of the selection of ground motion intensity measures on the determination of modeling uncertainty is investigated. Finally, the annual probabilities of exceeding each limit state with different confidence levels are calculated, and two methods, the mean estimates approach and the confidence interval method, are used to incorporate uncertainties. The results show that the characteristics of ground motions affect the sensitivity of the median capacity to the disturbance of structural parameters. The modeling uncertainty estimated in the near-field records is meaningfully less than that in the far-field records. Judging from this limited case study, the modeling uncertainty estimated may be underestimated by using an inefficient IM. The influence of the modeling uncertainty in the fragility analysis for each limit state cannot be ignored when using the confidence interval method.

In this study, performance comparison for steel and biaxial geogrid reinforced concrete samples is explored. The basic properties of geosynthetics and concrete ingredients were studied. Formulae and derivations of limiting moment, maximum load, and area of geogrid reinforcements for flexural slab were obtained by limit state design methodology. Three types of textile and one biaxial geogrid were individually employed in concrete specimens (cubes, prisms, and slabs). From the results, the geogrid exhibited good performance with the concrete. The flexural behaviour of the steel-reinforced sample is compared with the geogrid reinforced ones. The flexural test of geogrid reinforced flexural members showed satisfactory results. The load-carrying capacity, deflection, and energy absorption of the geogrid reinforced slab, as compared to the steel-reinforced slab, increased by 25, 6.5, and 23%, respectively. The study demonstrated a sustainable reinforcement of concrete that can be a practical solution to corrosion issues experienced in the construction field.

The near field pulse-like ground motion has significant effects on a long-period structure like a wind turbine. Such pulses can be due to source effect (directivity) or site effect (presence of basins), to name a few. The presence of such pulses in the existing recordings of earthquakes is well documented. However, due to the paucity of such pulse-like recordings, simplified shapes have been proposed in literature in accordance with the observed features. In this study, the influence of characteristics parameters of earthquake velocity pulse on the monopile-supported offshore wind turbine (OWT) determined. The four parameters of velocity pulse, i.e., vp the velocity amplitude, fp the prevailing frequency, n number of pulse, and the α/β parameter of envelope function, are considered. To perform the incremental dynamic analysis, the numerical model of OWT is developed in open-source software OpenSees. The pulse-like ground motion parameters effects are shown in terms of fragility curves for the serviceability limit state and ultimate limit state.

Current design methods for the internal stability of geosynthetic-reinforced soil (GRS) walls postulate seismic forces as inertial forces, leading to pseudo-static analyses based on active earth pressure theory, which yields unconservative reinforcement loads required for seismic stability. Most seismic analyses are limited to the determination of maximum reinforcement strength. This study aimed to calculate the distribution of the reinforcement load and connection strength required for each layer of the seismic GRS wall. Using the top-down procedure involves all of the possible failure surfaces for the seismic analyses of the GRS wall and then obtains the reinforcement load distribution for the limit state. The distributions are used to determine the required connection strength and to approximately assess the facing lateral deformation. For sufficient pullout resistance to be provided by each reinforcement, the maximum required tensile resistance is identical to the results based on the Mononobe-Okabe method. However, short reinforcement results in greater tensile resistances in the mid and lower layers as evinced by compound failure frequently occurring in GRS walls during an earthquake. Parametric studies involving backfill friction angle, reinforcement length, vertical seismic acceleration, and secondary reinforcement are conducted to investigate seismic impacts on the stability and lateral deformation of GRS walls.

We study the models of multicomponent discrete dynamical conflict systems with attractive interaction characterized by a positive value called the attractor index. The existence of limit equilibrium states in these systems is proved and their description in terms of the attractor index is given. An explicit relationship between the limit state of the system and the attractor index is established. A series of concrete examples is presented. They illustrate the dynamics of the system for different attractor indices.

Slope stability assessment is one of the most important issues for geotechnical engineers. In the framework of a nonlinear failure criterion, four different types of safety factors are presented and their relationships are investigated for soil slope in this study. The variational method is incorporated into the kinematic approach of limit analysis to assess the stability of soil slope with known geometric boundary, and seismic effects are considered. The seismic loads are simplified as external forces acting on the slope. A rotational failure mechanism is used to describe the sliding mode of slopes. The differential equations for the sliding surface and corresponding stress distribution are derived using the variational method and then are employed to generate the sliding surface via the fourth-order Runge-Kutta approach. To avoid the computational complexity, the energy-work balance equation of the kinematic approach, instead of the static equilibrium equation, is used to judge whether the state of the slope is critical. The safety factor is designed as the minimum factor that brings the slope in the limit state. Computational schemes are proposed to calculate the values of safety factors. The validity of the proposed approach is demonstrated through comparison with previous works. Finally, parametric study is conducted to further reveal the relationships among the four types of safety factors.

By using an analog of the δc -model, we reduce the problem of stressed state and limit equilibrium of an inhomogeneous shell of revolution weakened by an internal crack of any configuration with plastic strains developed on the continuation of the crack in the form of a narrow strip to an elastic problem. The indicated elastic problem is then reduced to a system of singular integral equations with unknown limits of integration and discontinuous functions on the right-hand sides. We propose an algorithm for the numerical solution of these systems with regard for the conditions of plasticity of thin shells and the conditions of boundedness for stresses. The effects of loading, geometric parameters, and mechanical characteristics on the crack-opening displacement and the sizes of plastic zones are investigated for cylindrical and spherical shells made of functionally graded materials and containing internal parabolic cracks.

Placement of shallow foundations near or adjacent to slopes reduces their seismic and static bearing capacities. In this paper, the seismic behavior of shallow foundations adjacent to sandy slopes has been studied using a two-dimensional finite element method. Most of the previous studies have focused on upper bound solutions in limit state analysis framework via pseudo-static loading, and the effects of actual seismic loading such as loading frequency effects, acceleration amplitude above 0.30 g, non-linear dynamic analysis, and so on are ignored. The shallow foundations are located at a certain distance from the slope crest (i.e., d = 0.5b, 1.5b and 2.0b). The slope inclination angle studied in this paper is 25° (1 V: 2 H). The analyzed slope is composed of medium dense sand. The two elastic–perfectly plastic Mohr–Coulomb (MC) and hardening soil (HSM) constitutive models have been considered to investigate the effect of plastic behavior of the sandy soil. Innovatively, the actual seismic behavior of the slope, shallow foundation and the direction of the seismic responses have been studied. The results show that the structural and geotechnical responses of the HSM model are in most cases up to 30% larger and more conservative than the MC model responses. This shows the importance of using the HSM model in the study of seismic stability of slope and foundation.

This paper presents a parametric study of the optimization design for T-shaped deep cement mixing (TDM) and conventional deep cement mixing (DCM) columns improved soft soil for supporting embankments. The objective of the optimization was to find the best compromised solution for the cost effectiveness in conjunction with minimizing the serviceability limit state (SLS) requirements (i.e., settlements, differential settlements, and lateral movements) while maximizing the ultimate limit state (ULS) requirement (i.e., factor of safety against bending failure). A combination between a genetic algorithm and the response surface method was employed as an optimization approach for determining the optimal solution. The relations and interpretations between design column parameters and design requirements are presented and discussed through parametric studies. The optimization results indicate that the optimal TDM column can allow to permit a lower construction cost than the optimal DCM one.

The paper presents the comparison of the results obtained on a masonry building by nonlinear static analysis using different software operating in the field of continuum and discrete-macroelement modeling. The structure is inspired by an actual building, the "P. Capuzi" school in Visso (Macerata, Italy), seriously damaged following the seismic events that affected Central Italy from August 2016 to January 2017. The activity described is part of a wider research program carried out by various units involved in the ReLUIS 2017/2108 - Masonry Structures project and having as its object the analysis of benchmark structures for the evaluation of the reliability of software packages. The comparison of analysis was carried out in relation to: global parameters (concerning the dynamic properties, capacity curves and equivalent bilinear curves), synthetic parameters of structural safety (such as, for example, the maximum acceleration compatible with the life safety limit state) and the response in terms of simulated damage. The results allow for some insights on the use of continuum and discrete-macroelement modeling, with respect to the dispersion of the results and on the potential repercussions in the professional field. This response was also analyzed considering different approaches for the application of loads. URM building.

This paper analyzed the ultimate grout-to-soil bond strength based on a database of 40 full-scale static load tests conducted on micropiles in glacial deposits in the province of Ontario, Canada. The Decourt extrapolation method was used to extrapolate the field load–settlement curves to identify the ultimate limit state. The elastic length method was modified by considering the shear stress influence to more accurately predict the failure loads of micropiles. A set of the ultimate bond strengths were correlated with the field standard penetration test blow count for different types of micropiles in different soil conditions. The results were compared with existing design values recommended by the Federal Highway Administration manual. The findings will help to improve the design of micropiles in similar soil conditions and the development of a reliability-based design method for soil-bonded micropiles.

With complex limit state functions and small failure probability, the analysis of engineering structure reliability is a challenging problem. Most of the traditional methods require a lot of calculation time, which results in delaying the progress of solving engineering. To overcome this issue, a new structural reliability analysis method aiming to select a set of better initial design of experiment (DoE) is proposed in this study. The proposed method combines a weighted sampling based on sample probability and a novel selection strategy to select DoE and conduct active learning. Weighted sampling based on sample probability density makes the DoE uniformly distributed in the sampling space. The novel selection strategy is proposed to make selected DoE near limit state surface (LSS) and has better predictive ability. Numerical examples and engineering examples show that this method can perform energy efficiency analysis in important areas. The results show that the method is accurate and efficient in solving low failure probability and nonlinearity problems.

Steel I beams or girders with sinusoidal corrugated profile webs have become popular in the recent development of the steel structural designs, since corrugated-web beams (CWBs) can provide better performance in terms of less deformation and more stability against buckling failure. It is verified in previous research that CWBs can be considered as an alternative to replace normal beams in the structural designs with their numerous favourable features. Since CWBs are being used as the main structural elements, it is apparent that some essential practical properties of this type of beams should be studied, where the prediction of the shear capacity is one of the most significant design aspects that should be accurately investigated. Calculations to the design formulas from other standards and several finite element simulations have been carried out to compare the differences in obtained results and to find an adequate approach to calculate the shear capacity of CWBs for the Australian civil engineering community. Ultimate Limit State design theory has been utilised in conjunction with AS4100 (2017) along with linear analysis in SAP2000. By comparing the results of the theoretical calculations and numerical simulations, it has been concluded that the highly formed equations presented by EN 1993-1-5 (Design of Steel Structures Part 1–5: Plated Structural Elements, Eurocode 3, Brussels, 2006), Hancock et al. (2012) could well estimate the shear capacity constraining requirements and rules in accordance with Australian standards, which can be adequately used in Australian structural design fields.

The strength of a layered shell structure of composite materials is investigated by combining modern strength criteria, the theory of deformable solid orthotropic medium mechanics, and methods of fracture mechanics. An adapted method of determining the limit state is used to assess the bearing ability of layered shell structures that have supercritical defects in the form of surface operational damages. The problem is solved analytically and numerically via the finite element method. A finite-element three-dimensional shell model of strength research is considered as a two-layer body, each layer of which is a composite material with given physical and mechanical characteristics, taking into account the structure of composite materials and the relations between the relevant components. To assess the strength of the developed model with a surface roundsegment damage, a crack is additionally introduced, which surface length and depth of propagation in the body of the upper layer of the cylindrical composite shell are varied. The obtained dependences of the parametric length and crack front on the limit values of the internal pressure are analyzed, fixing the moment of its displacement for this type of material and determining the limiting equilibrium state of the shell at the fracture stage. Evolution curves of crack resistance force characteristics in the form of stress intensity factors are constructed. The limit state analysis is based on the values of the critical stress intensity coefficients obtained due to mechanical tests of bidirectional fiber composite specimens with notches. The results obtained using the refined method of strength assessment are compared with the experimental ones, showing their close correlation.

Sheet pile wharfs are widely used coastal structures with good adaptability for geological conditions. A reliability evaluation is required for safety. Challenges are raised from the complicated solution in both the structural response and reliability. To provide a flexible and efficient approach, an integrated reliability analysis model was proposed: The virtual simply support beam (VSSB) model was developed to estimate the structural response; Based on probabilistic methodologies and artificial intelligence (AI) models, the limit state surface was fitted to search reliability solutions. A case study was used to illustrate the applicability of the proposed model and compare the prediction performance of AI models. An extensive parametric study was performed to investigate the influential factors on structural reliability. Compared with finite element analysis, the VSSB model presented reasonable estimations on structural response. The genetic programming performed best in predicting structural response with an average relative absolute error (RAE) of 0.018. The corresponding integrated models gave the reliability solutions with an average RAE of less than 0.014. Soil parameters in different positions significantly affected the structural stability, that the material qualities should be addressed. This study provides references in engineering safety design and guidelines the reliability analysis framework for complicated structures.

Currently, knowledge of the failure mechanisms of narrow backfills with retaining walls rotating about the top (RT mode) is still lacking which leads to inaccurate estimations of the earth pressure. Numerical simulations using finite element limit analysis find that under the effects of backfill geometries, interface strengths, and soil properties, the upper soil layer supported by soil arching retains its integrity and the lower soil layer is sheared by multiple curved sliding surfaces in the limit state. Based on the failure mechanisms of narrow backfills, a calculation model is established which considers the soil arching effect, curved sliding surface, and cohesive soils. Analytical solutions for the earth pressure of narrow cohesive backfills with retaining walls rotating about the top are derived by using the limit equilibrium horizontal slice method. Compared with previous studies, the present method predicts the earth pressure distribution with higher accuracy. Several extensive parametric studies have also been conducted. Thus, decreasing the aspect ratio of backfills, increasing the inclined angle of natural slopes, interface strengths, and soil cohesion are beneficial for maintaining backfill integrity and reducing earth pressure against retaining walls.

An innovative reliability estimation procedure for Jacket-type offshore platforms is proposed. The information on risk is extracted using multiple deterministic analyses using advanced mathematical theories resulting in compounding beneficial effects. The platforms are modeled by finite elements. Nonlinearity and major sources of uncertainty are incorporated. The wave loading model is realistically developed to satisfy the underlying physics. It is applied in three-dimension in time domain incorporating the uncertainties in the parameters. Implicit performance functions are expressed explicitly using several advanced factorial schemes and significantly improved response surface method. The efficiency and accuracy of the method are improved using a comprehensively improved Kriging-based surrogate modeling technique. The risk is evaluated for the serviceability and strength limit state functions for a jacket-type offshore platform using about two hundred nonlinear finite element analyses. The procedure was verified using simulation techniques. The concept can be considered an alternative to the conventional random vibration techniques and the standard Monte Carlo simulation procedure.

Steel I-section-plate girders with corrugated webs have been used worldwide as they provide more stability and light beam features in practical design. It is known from previous investigations that due to having numerous favourable properties, the corrugated-web beams have been used in different areas of structural engineering. Considering the raising popularity of using CWBs in steel design, some practical aspects of CWBs need to be investigated further, in which post-buckling strength is one of the most critical strengths that should be precisely estimated. To fulfill this requirement regarding the post-bucking strength determination for structural designers community, a numerical investigation has been conducted in this study to determine the moment capacity reduction factors for steel I girders with corrugated-web profile and to compare reduction factor values extracted from EN 1993-1-5 (Design of steel structures part 1–5: Plated structural elements, Eurocode 3, Brussels, 2006), AS4100 (Steel structures, Standard Australia, Sydney, 1998), and finite element analysis. Theory of Ultimate Limit State design has been adopted in accordance with AS4100 (1998) along with considering geometric and material non-linearity in the numerical analyses in SAP2000 software. Eventually, the results of the parametric study have been compared and discussed leading to presenting practical recommendations on the design of CWBs for bending strength.

This article presents a computational reliability analysis of reinforced soil-retaining structures (RSRS) under seismic conditions. The internal stability of RSRS is evaluated using the horizontal slice method (HSM) with modified pseudo-dynamic seismic forces. Two different failure modes of RSRS are identified and their reliability indices are computed using the first-order reliability method (FORM). The critical probabilistic failure surface is identified using a three-tier optimization scheme. Reliability index of the system is computed by considering the modes of failure to be connected in series. The tension mode is found to be the most critical mode of failure. The present study identifies that the wall height (H), shear wave velocity of the soil (Vs), and predominant frequency of the input motion (ω) govern the response of RSRS. Reliability indices depend on a parameter termed as the normalized frequency (ωH/Vs) and their values decrease with an increase in the value of ωH/Vs. Increase in the damping ratio of soil, increases the value of reliability indices, especially for ωH/Vs values, which are close to π/2. The FORM suffers from few critical shortcomings such as linear assumption of limit state surface at the most probable point of failure and its ability to consider only the statistical uncertainties excluding the effect of epistemic uncertainties. This calls for sampling-based numerical techniques such as Monte-Carlo simulation (MCS) which gives more comprehensive understanding of the problem under consideration in a probabilistic framework. Thus, a computationally efficient surrogate-assisted MCS is carried out to validate the present formulation and provide numerical insights by capturing the system dynamics over the entire design domain. Adoption of the efficient surrogate-assisted approach allowed us to quantify the epistemic uncertainty associated with the system using Gaussian white noise (GWN). Subsequently, its effects on the system reliability index and probabilistic behavior of the critical parameters are presented. The numerical results clearly indicate that it is imperative to take into account the probabilistic deviations of the critical performance parameters for RSRS to ensure adequate safety and serviceability under operational condition while quantifying the reliability of such systems.

Deflection of the steel I-sections is an important phenomenon that needs to be taken into account to ensure that the serviceability limit state criteria of the Australian Standards are met. The method that is widely used to calculate the deflection of steel I-sections is by the use of existing formulae that only accommodate the bending stiffness of the beams. A numerical investigation is performed in this study to find the contribution of shear effects in the final deflection of the Welded-Beams (WB) and Welded-Columns (WC). The numerical analyses were carried out in SAP2000 and numerical model was first validated using the experimental results of welded plate girders. The model was then used to analyse simply supported WB and WC sections under uniformly distributed load (UDL) with varying span lengths. The results of the numerical analyses are reported in this study which compare the mid-span deflection values from the simply supported deflection formula with the numerical model deflection values. The data acquired from the numerical analyses were used to establish a span to depth ratio for WB and WC sections below which the shear deflection becomes significant. The analysis of the results obtained from the numerical investigation suggests that a predication error begins to emerge in the result that is acquired from flexure deflection formulae at a certain span-depth ratio.

This paper is a contribution to the analysis of skew cracking (orientation, spacing, maximum and residual crack width) in reinforced concrete shear walls subjected to seismic loading. First, it presents the experimental campaign of the French national research project CEOS.fr and several test results obtained by different measurement techniques applied on the test specimens. Although the tests were carried out under cyclic conditions, with or without reversing the direction, the obtained information could be compared with the results given by the application of the design codes, based on the post-treatment of stresses evaluated by a structural analysis. To that end, the reinforced concrete shear wall specimen is modelled by the Finite Element software Code_ASTER, using different constitutive models. Structural modelling is a crucial phase for a good assessment of crack width. This article proposes procedures to calculate crack width based on the fib Model Code 2010 approach with appropriate complements; this approach leads to a good agreement to the experimental results. Finally, the article presents and discusses the effects of the cyclic loading at Ultimate Limit State, as the values of residual crack width under reversing load cycles. The study of all these aspects results in operational procedures for engineering applications.

Stiffened plates are main structural building block in vessel hull, and their structural response subject to combined loads is a topic of significant practical interest in ship and offshore structural design. A stiffened panel from a bulk carrier side is analysed with respect to buckling and ultimate strength by means of nonlinear finite-element code ABAQUS. The findings are compared to DNVGL Panel Ultimate Limit State (PULS) buckling procedure for stiffened plates. Combinations of in-plane transverse compression and shear load as well as lateral pressure are analysed. The stiffened panel under consideration is analysed both with a plate thickness of 12.5 mm and with 15.0 mm. Further, four restart analyses are carried out, where the panels are offloaded from the ultimate limit state to zero loads in order to quantify permanent sets. A total of 36 analyses are conducted, where the imperfection tolerances are set to 1/200 times stiffener spacing in the local mode and 1/1000 times stiffener span in the global mode. The shapes of the imperfections are in general based on a combination of the lowest elastic buckling mode, together with a sine varying asymmetric global imperfection for the stiffeners. The PULS and ABAQUS predictions are utilized, and quite good agreements are achieved between the predictions.

High strength concrete is becoming widely popular for multi-storey buildings due to its several advantages such as reduction in the size of section, reduces the weight of building and also for aesthetical appearance of structure. Further, the strength and other parameters of high strength concrete are different then the ordinary concrete. There are no special guides lines provided by IS 456-2000 for designing the high strength concrete slab, and the span-to-depth ratio provided in this code is not compatible for high strength concrete. Therefore, a study is carried out on the seismic behaviour of high strength concrete slabs for limit state of serviceability and further extended about the seismic behaviour of these buildings. A modification factor has been introduce for depth to span ratio of high strength concrete slab, further the result indicates that earthquake responses of high strength concrete slab buildings are much superior than then ordinary concrete.

The ultra-low cycle fatigue (ULCF) fracture initiation caused by cyclic large plastic strain in structural steels is often the governing limit state in steel structures when subjected to strong earthquake actions. Based on the author’s previous work, this paper presents the improved cyclic void growth model (CVGM) and degraded significant plastic strain (DSPS) model considering the dependence of cyclic damage degradation parameters on stress triaxiality. To this end, tests on circular notched specimens and coupon specimens made of Q345qC steel were conducted, and scanning electron microscopy studies were performed on fracture surfaces of specimens, analysis results of which show that the ULCF fracture of Q345qC steel exhibits the typical behaviour of “void nucleation, growth, and coalescence.” The cyclic damage degradation parameters of CVGM and DSPS model were calibrated at different stress triaxialities based on experimental results of specimens and complementary finite element analysis, and empirical formulas were subsequently established between cyclic damage degradation parameters and stress triaxiality. Finally, detailed finite element analysis results demonstrate that the improved CVGM and DSPS model can predict ULCF fracture behaviour with higher accuracy in comparison with original models.

This study examines the effect of vehicle–bridge interaction (VBI) on the vibration of coupled train–bridge systems and proposes a consistent approach to decouple the VBI problem; the Extended Modified Bridge System (EMBS) method. This constitutes an extension of the formerly developed, for simply supported bridges, Modified Bridge System method. The analysis considers a generic, multi-degree of freedom (MDOF) vehicle–MDOF bridge configuration, representative of a wide class of practical train–bridge systems. This approach enables the MDOF representation of the constituent VBI mechanisms on the mechanical system of the bridge. Based on an asymptotic expansion analysis of the coupled system response, the study brings forward the dominant coupling parameters and their relative importance on the bridge response. The proposed decoupling EMBS method solves the bridge independently of the vehicle by changing its mechanical system via additional damping, stiffness and loading terms. The MDOF description of these terms makes the proposed scheme appropriate for involved bridge configurations, such as continuous and arch bridges. In addition, it allows the accurate estimation of the deck acceleration of bridges, which is an important serviceability limit state. Numerical examples demonstrate the accuracy and efficiency of the EMBS method compared with the solution of the fully coupled system and other decoupling methodologies. Lastly, the proposed approach is simpler than the coupled analysis, which can be of particular importance in bridge design practice.

Limit equilibrium methods have been extensively used in the design of reinforced soil structures using various types of failure surfaces. A significant problem in limit equilibrium analysis of reinforced soil is the need to know the force at each reinforcement layer in the limit state. Limit equilibrium analysis with log spiral failure mechanism has been employed to locate the critical failure surfaces emerging at or above the toe and to study the behavior of geosynthetic-reinforced soil slopes. This paper describes a numerical procedure, using limit equilibrium methods, to evaluate the distribution of the soil slope reinforcement tensile forces. Both, log spiral and circular slip surfaces are considered. The effect on the required tensile forces of the target safety factor value, the ratio of the mobilized soil shear strength, and the reinforcement layer spacing are examined. Results show that the distribution of reinforcement tensile forces is dependant on reinforcement layer spacing; however, the total reinforcement force is not. The total reinforcement force required to ensure equilibrium is strongly dependant on the target safety factor value and the ratio of the mobilized soil shear strength. Modified Bishop Method with circular failure surface and Shiwakoti–Leshchinsky log spiral failure surface led to comparable results.

An insufficient separation distance between adjacent buildings is the main reason for structural pounding during severe earthquakes. The lateral load resistance system, fundamental natural period, mass, and stiffness are important factors having the influence on collisions between two adjacent structures. In this study, 3-, 5- and 9-story adjacent reinforced concrete and steel moment resisting frames (MRFs) were considered to investigate the collision effects and to determine modification factors for new and already existing buildings. For this purpose, incremental dynamic analysis was used to assess the seismic limit state capacity of the structures using a developed algorithm in OpenSees software including two near-field record subsets suggested by FEMA-P695. The results of this paper can help engineers to approximately estimate the performance levels of MRFs due to pounding phenomenon. The results confirm that collisions can lead to the changes in performance levels, which are difficult to be considered during the design process. In addition, the results of the analyses illustrate that providing a fluid viscous damper between adjacent reinforced concrete and steel structures can be effective to eliminate the sudden changes in the lateral force during collision. This approach can be successfully used for retrofitting adjacent structures with insufficient in-between separation distances.

Under-clearance of bridges is one of the major considerations when planning and designing bridges. Especially for sea-crossing bridges, under-clearance is more important for safe passage of ships. Long span cable bridges with steel orthotropic deck usually show relatively large deflections and excessive deflections may be not only disadvantageous to the clearance plan, but also a problem in bridge serviceability. The clearance of sea-crossing bridge is designed with air draft from the waterline to top of mast, ship’s trim, psychological free space, sea level, height of wave and bridge deflection by live loads. At design stage, bridge engineers need a live load deflection limit to ensure adequate clearance. The limitation of live load deflection is also considered for ensuring the serviceability of vibration of bridges. For vibrational serviceability, the live load deflection limit is expressed as a ratio to the span or the formula by natural frequency. On the other hand, some standards specify vibration serviceability limit by peak or root-mean-square (RMS) acceleration. The purpose of this study is to propose new deflection limit criteria for long span steel cable bridges based on analysis and long-term measurement data. Structural analysis was performed on two steel suspension and three steel cable-stayed bridges with more than 200 m of main span under design live load model of DL24 and new live load model KL510 in limit state design code. Also, the deflection limit criterion was evaluated by probabilistic method using the deflection data measured for 1 year. The results of this study are expected to be useful data for bridge engineers designing long span steel cable bridges.

This study first develops a database containing 56 measured facing tensile forces from instrumented soil nail walls during or at completion of construction. Based on the compiled database, the accuracies of both default and modified federal highway administration (FHWA) simplified models for estimation of short-term facing tensile forces are evaluated. Here, accuracy is defined by the model bias computed as the ratio of measured to predicted facing tensile force. The analysis results show that predictions are highly conservative and highly dispersive using the default model, and moderately conservative and medium dispersive using the modified model. Moreover, the prediction accuracy is statistically correlated with magnitudes of the computed facing tensile forces and several model input parameters. An out-of-sample approach is used to develop and validate a recalibrated FHWA model which is then demonstrated to have least empirical constants but best accuracy compared to the default and modified models. The biases for the three models are characterized as lognormal random variables. An example of reliability-based analysis for facing flexure limit state is illustrated to both elaborate the application and highlight the benefit of using the recalibrated model for design practice from the perspective of cost-effectiveness.

The paper analyzes the main criteria for the limit state of structural materials at the stage of macrocrack nucleation, which are based on the basic provisions of thermodynamics of irreversible processes in continuum mechanics of damageability. The limits of their application for the case of complex stressed state are established. A model of scattered damage accumulation depending on the level of irreversible strain is presented and the dependences of kinetics parameters of damage accumulation and damage limit value on the elastic-plastic characteristics of the material under pure tension conditions are established. The kinetics of damage accumulation according to the presented model is compared to the experimental values for several of structural materials. The methodology of the basic experiment with cylindrical solid specimens is described, taking into account the non-uniformity of the strain distribution along the specimen radius. The results of damage accumulation by shear failure mechanism obtained via the developed technique are compared with the experimental results of thin-walled specimens. It is shown that the value of damageability parameter essentially depends on the type of stressed state. On the basis of Davidenkov–Fridman approach, which takes into account two (tear and shear) failure mechanisms, a generalized phenomenological criterion of limiting state is proposed and substantiated using the Nadai–Lode stress state type parameter.

This paper formulates a mathematical model using the extrapolation of load-settlement curves with a rational function for analyzing the capacity of piles obtained from the static load test (SLT). In preliminary analyses, the extrapolation was based on the application of a number of mathematical functions that were gradually eliminated by iterative selection and filtering. The solution was obtained by extrapolation with a rational function. Using a rational function in the extrapolation of the load-settlement curve, a clearly identifiable part is obtained in which the asymptote is vertical, indicating the reached limit state of capacity in the soil and/or in the pile. The probabilistic analysis showed that no unique value for pile capacity was obtained, and that the spectrum of capacity values depends on the probability of occurrence of the corresponding event.

Geo-synthetic reinforced soil retaining wall (GRS-RW) combined with a Gravity Retaining wall (GRW) facing or Full High Rigid (FHR) facing is a new type of retaining wall. This type of retaining wall is used to get full advantages of GRW and reinforced soil retaining wall (RS-RW) and to avoid their drawbacks. The design method based on the principle of working strain considers the backfill in the limit state but the reinforcement not in the limit state; while in traditional design method based on the tensile strength of reinforcement, consider both backfill and reinforcements in the limit state and it cannot reflect the influence of reinforcement stiffness. In this paper, numerical analyses were performed to evaluate the stress and strain of both reinforcement and backfill. From the analyses, deformation of the retaining wall, the working performance of GRS-RW with GRW facing, and contribution of geo-grids to GRS-RW with a GRW facing, were evaluated. Analyses are performed for determining the force between GRS-RW with a GRW facing and reinforced soil. Analytical methods, for the calculation of soil pressure acting on the back of GRW, based on the principle of working stress are obtained by comparative analysis between the working performance characteristics of common GRS-RW and GRS-RW with GRW facing. A new analytical method for determining the force between GRS-RW with a GRW facing and reinforced soil “E” is proposed. By comparative study between theoretical and numerical analysis results, method 1 and method 2 are recommended for determining the “E”. A method for determining the tension in the reinforcement of GRS-RW with a GRW facing based on the principle of working strain is also presented in this paper.

Recently, the modification of bituminous binders is an ongoing trend. However, most current analytical methods are insufficient to characterize bitumen. Generally, standardized laboratory techniques are often time and cost consuming. Moreover, they use one-purpose devices requiring a considerable amount of samples and solvents. Therefore, we investigated three special instrumental analytical techniques to find out bitumen properties. Our main objective was to obtain some additional parameters of bituminous binders to allow their more accurate description. The first studied method, thermogravimetric analysis operated especially in a high-resolution mode that can be used as a fingerprint area in spectrometry to determine the bitumen quality. The second one modulated differential scanning calorimetry provided many various important parameters, including temperature of glass transition, cold crystallization and serviceability limit state. The third one, the thermomechanical analysis also measured the value of glass-transition temperature for comparison with the method mentioned above. We have found correlations between the results from thermal instrumental techniques and standardized laboratory tests.

The residual strength capacity of ship hull with full corrosion appearance in every structural member has been considered in a large number of research works; however, the influence of local corrosion on the ultimate strength and cross-section properties has not been taken into account and analyzed. Hence, this study aims to assess the effect of corrosion appearance in the flange section and web section on the ultimate vertical bending moment and several cross-section properties of a bulk carrier. To perform this task, a probabilistic corrosion rate estimation model and the common structural rule model are introduced and employed. The incremental-iterative method given by the International Association of Classification Societies-Common Structural Rules (IACS-CSR) is applied to determine the ultimate vertical bending moment, neutral axis position at the limit state, and other properties of the cross-section. The calculation results and discussions relative to the effect of corrosion on ship hull are presented.

To further exploit the potential of marine composites applications in building ship hulls, offshore structures, and marine equipment and components, design approaches should be improved, facing the challenge of a more comprehensive and explicit assessment of appropriately defined limit states. The structure ultimate/limit conditions shall be verified in principle within the whole structural domain and throughout the ship service life. What above calls for extended and reliable materials characterization on the one hand and for accurate and wide-ranging procedures in structural analyses. This paper presents an overview of recent industrial developments of marine composites limit states assessments and design approaches, as available in open literature, focusing on pleasure crafts and yachts as well as navy ships and thus showing a starting point to fill the gap in this respect. After a general introduction about composites characterization techniques, current design practice and rule requirements are briefly summarized. Both inter-ply and intra-ply failure modes and corresponding limit states are then presented along with recently proposed assessment approaches. Three-dimensional aspects in failure modes and manufacturing methods have been identified as the main factors influencing marine composite robustness. Literature review highlighted also fire resistance and hybrid joining techniques as significant issues in the use of marine composites.

The planning and design of buildings and civil engineering concrete structures constitutes a complex problem subject to constraints, for instance, limit state constraints from design codes, evaluated by expensive computations such as finite element (FE) simulations. Traditionally, the focus has been on minimizing costs exclusively, while the current trend calls for good trade-offs of multiple criteria such as sustainability, buildability, and performance, which can typically be computed cheaply from the design parameters. Multi-objective methods can provide more relevant design strategies to find such trade-offs. However, the potential of multi-objective optimization methods remains unexploited in structural concrete design practice, as the expensiveness of structural design problems severely limits the scope of applicable algorithms. Bayesian optimization has emerged as an efficient approach to optimizing expensive functions, but it has not been, to the best of our knowledge, applied to constrained multi-objective optimization of structural concrete design problems. In this work, we develop a Bayesian optimization framework explicitly exploiting the features inherent to structural design problems, that is, expensive constraints and cheap objectives. The framework is evaluated on a generic case of structural design of a reinforced concrete (RC) beam, taking into account sustainability, buildability, and performance objectives, and is benchmarked against the well-known Non-dominated Sorting Genetic Algorithm II (NSGA-II) and a random search procedure. The results show that the Bayesian algorithm performs considerably better in terms of rate-of-improvement, final solution quality, and variance across repeated runs, which suggests it is well-suited for multi-objective constrained optimization problems in structural design.

A high percentage of reinforced concrete (RC) buildings in Portugal were designed and built before the introduction of modern seismic codes. This research aims to assess the seismic capacity and vulnerability of RC buildings in the city of Lisbon. For that purpose, nonlinear static procedures have been used and fragility curves have been developed. These buildings are reaching the end of their nominal life. Therefore, ageing effects have been taken into account, as well as the presence of smooth rebar. To do so, a sensitivity analysis has been performed by considering the chloride-induced corrosion of the reinforcement steel rebar and the degradation of the concrete cover. To illustrate the effects of ageing and the procedure adopted for the seismic fragility assessment of old RC structures, three RC buildings with masonry infills have been selected as case studies. They were all built between 1960 and 1980, and they are representative of the current building stock in Lisbon. The seismic capacity of the buildings has been determined by means of nonlinear static analyses of three-dimensional numerical models. The N2 method and its extended version have been considered to determine the target displacement. The seismic safety of the buildings has been estimated in terms of the demand/capacity ratio for each vertical structural element (columns and walls) according to the bending and the shear failures. Then, a set of fragility curves has been developed for all buildings to represent the probability of RC elements reaching or exceeding the significant damage limit state. Results have shown that the concrete strength degradation has had more influence than reduction of the rebar diameter in the seismic capacity. When considering steel corrosion, it has been demonstrated that the corrosion rate has reduced the capacity more than the time of exposure. It can be concluded that ageing affects the seismic behaviour of RC structures, increasing the vulnerability of these buildings.

Using surrogate models to substitute the computationally expensive limit state functions is a promising way to decrease the cost of implementing reliability-based design optimization (RBDO). To train the models efficiently, the active learning strategies have been intensively studied. However, the existing learning strategies either do not individually build the models according to importance measurement or do not completely relate to the reliability analysis results. Consequently, some points that are useless to refine the limit state functions or far away from the RBDO solutions are generated. This paper proposes a multi-constraint failure-pursuing sampling method to maximize the reward of adding new training points. A simultaneous learning strategy is employed to sequentially update the Kriging models with the points selected in the current approximate safe region. Moreover, the sensitive Kriging model as well as the sensitive sample point are identified based on the failure-pursuing scheme. A new point that is highly potential to improve the accuracy of reliability analysis and optimization can then be generated near the sensitive sample point and used to update the sensitive model. Besides, numerical examples and engineering application are used to validate the performance of the proposed method.

Full design analysis of a bridge usually has lots of load cases and leads to the analysis process, which is extremely time-consuming. To reduce the computational cost, the existing hanger pre-tensioning force optimization approaches for cable-supported bridges always consider only a few critical load cases. This study presents an efficient approach for hanger pre-tensioning force optimization of steel tied-arch bridges, which can include all the operational loads and their combinations based on the code requirements. The proposed method develops a load decoupling approach (LDA) to enhance the computational efficiency of structural analysis in optimization and utilize the particle swarm optimization algorithm to search the global optimal design. The LDA divides the structural analysis procedure into two systems: (1) iteration-varying and (2) iteration-invariant. The former evaluates the structural responses induced by different hanger forces using unit load method (ULM) and the latter solely needs a single finite element (FE) analysis before iteration to calculate the structural responses caused by the other loads. The superposition principle combines the results from the two systems to identify the minimum safety margin of the bridge under the ultimate limit state. A practical bridge is examined to compare the proposed method with three traditional hanger force determination approaches. The obtained results illustrate that the proposed method not only owns high efficiency but also leads to a safer design and has a broader application range.

The research on the seismic assessment of pipe racks accounting for coupling and soil-structure interaction effects is still scarce. Common industrial practice overlooks critical design aspects due to the insufficiency of current codes that might result in over-conservative or unsafe design. This work addresses the nonlinear analysis of a petrochemical plant steel pipe rack accounting for dynamic interaction with horizontal vessels and pipelines. Soil-structure interaction was evaluated both on pipe rack and pipelines in terms of interstorey-drift ratio and stress–strain response. An attempt was made for correlating the ratio with piping strain to make comparisons with common acceptance criteria for building structures, since code provisions do not address currently limit state design concept for pipe racks. Additionally, seismic fragility curves along with 95% confidence intervals were evaluated for different intensity measures and were used as a tool to demonstrate that the soil deformability could act as an isolation mechanism for pipelines. The increase of pipe rack displacements was an additional impact of soil, though, it was not as much profound as on the seismic response of the pipelines. The detailed structural assessment through extensive nonlinear dynamic analyses demonstrated that the return period of exceedance of pipe rack and pipelines limit state, considering the median spectral acceleration as a measure, occurred 1.84 and 2.64 greater than the design one, and this might be an indication that the performance-based concept should be applied for pipe rack systems to achieve a safe, risk-consistent among structural and nonstructural members and cost-effective design.

As an attractive substitute of natural aggregate for asphalt mixture, steel slag raises many concerns on the water resistance of steel slag asphalt mixture in frozen and wet areas, due to the special interaction between steel slag and asphalt. This study aims to investigate the deterioration process of water resistance for asphalt mixture with different steel slag contents in dry–wet and freeze–thaw cycles environments. The Marshall immersion test and indirect tensile test were conducted, and the residual stability and tensile strength ratio (TSR) were measured to characterize the water resistance of the steel slag asphalt mixture. Furthermore, dry–wet and freeze–thaw repeated cycling conditions were designed to simulate the effect of actual environments on the long-term water resistance of asphalt pavement. Finally, the microstructures of the aggregate–asphalt interface area were observed, and the enhancement mechanism of the steel slag replacement in asphalt mixture was revealed. Results show that steel slag asphalt mixture exhibits significant resistance to water damage. With the increase in dry–wet or freeze–thaw repeated cycles, the water resistance of steel slag asphalt mixture rapidly deteriorates first and then tends to be stable, and there is a limit state of water damage. In dry–wet repeated cycles condition, the asphalt mixture with 50% steel slag content has a better water resistance, while the asphalt mixture with 100% steel slag content has a better water resistance under freeze–thaw repeated cycles condition. The interface phase structure of steel slag asphalt mixture is stable and dense, where the asphalt mortar evenly and tightly wraps the steel slag and forms a certain penetration depth. The enhancement mechanism of steel slag with asphalt mainly includes the physical anchoring effect and the chemical adhesion effect.

In this present study, an effort has been made to investigate the performance of reinforced concrete (RC) beam-column joints (BC) sub-assemblage using flat strips (FS) as an amended technique for confinement, to enhance the shear capacity of BC sub assemblage in the RC structure. Furthermore, the finite element (FE) model for tested joint assemblage using ANSYS was also carried out to compare the effects of ductility in terms of load-carrying capacity and ultimate load. The assemblage was provided with adequate transverse reinforcement as per ACI-318. The specimens were investigated into two groups. The reference specimen, BC-SS (joint standard stirrups) detailed with conventional stirrups of 10 mm-O and modified specimen, BC-FS (detailed by using flat strips). The specimens were tested under vertically monotonic loading to study their behavior at the ultimate limit state (ULS). The results show the significant improvements in the BC-FS specimen referred to in terms of ductility factor, stiffness, and strength.

This paper deals with the application of the semi-probabilistic design concept (level I, DIN EN 1990) to structural silicone adhesives in order to calibrate partial material safety factors for a stretch-based limit state equation. Based on the current legal situation for the application of structural sealants in façades, a new Eurocode-compliant design concept is introduced and compared to existing design codes (ETAG 002). This is followed by some background information on semi-probabilistic reliability modeling and the general framework of the Eurocode for the derivation of partial material safety factors at Level I. Within this paper, a specific partial material safety factor is derived for DOWSIL 993 silicone on the basis of experimental data. The data were then further evaluated under a stretch-based limit state function to obtain a partial material safety factor for that specific limit state function. This safety factor is then extended to the application in finite element calculation programs in such a way that it is possible for the first time to perform mesh-independent static calculations of silicone adhesive joints. This procedure thus allows for great optimization of structural sealant design with potentially high economical as well as sustainability benefits. An example for the static verification of a bonded façade construction by means of finite element calculation shows (i) the application of EC 0 to silicone adhesives and (ii) the transfer of the EC 0 method to the finite element method with the result that mesh-independent ultimate loads can be determined.

An investigation is conducted on the static ultimate limit state assessment of ship hull plates with elastically restrained edges subjected to axial compression. Both material and geometric non-linearities were considered in finite element (FE) analysis. The initial geometric imperfection of the plate was considered, while the residual stress introduced by welding was not considered. The ultimate strength of simply supported ship hull plates compared well with the existing empirical formula to validate the correctness of the applied boundary conditions, initial imperfection and mesh size. The extensive FE calculations on the ultimate strength of ship hull plates with elastically restrained edges are presented. Then a new simple empirical formula for plate ultimate strength is developed, which includes the effect of the rotational restraint stiffness, rotational restraint stiffness, and aspect ratios. By applying the new formula and FE method to ship hull plates in real ships, a good coincidence of the results between these two methods is obtained, which indicates that the new formula can accurately predict the ultimate strength of ship hull plates with elastically restrained edges.

Professor Jonathan Wu’s career was devoted to rigorous development of internal stability in reinforced soil as a new and evolving technology. This paper presents two of Professor Wu’s students’ work on the search for internal stability by tracing his work. Engineering design of reinforced soil originated in France with Schlosser and Vidal in the late 1960s. The first designs were based on a simple limit state method. Analyzing test data, Schlosser later found that the limit method was insufficient and that internal stability involves stiffness. Wu found that stiffness was affected by reinforcement spacing. Settlement or collapse is shown in examples that violate this spacing criterion. Initial analysis and validation involved geosynthetic sheets, but these were extended to other materials and to strip reinforcement. The analysis has been validated both by laboratory data and by field observations. These findings corroborate those of international companies in the reinforced soil community, but they are often incompatible with code in North America. The studies and discussions presented in this paper are further enhanced with the most current testing and work to confirm Professor’s Wu insights and visions.

This paper describes the full-scale test program of a code-conforming Post and Beam shearwall system conducted in a curtain wall test facility. The two-story test specimen is taken from a slice of index full-scale test structure to represent the first-mode dominant response properties. The design of the full-scale index building was carried out following the code requirements of wood buildings classified equal to or higher than the Grade-2 index buildings regarding the seismic grading scheme. The test program was not only aimed to provide an in-depth understanding of the seismic response characteristics of the shear wall assembly under cyclic deterioration but also contributed to developing reliable numerical models during the preliminary design phase of the 2019 full-scale shake table test program of the Tokyo Metropolitan Earthquake Resiliency Project. Moreover, the effectiveness of the instrumentation scheme to trace the distinct damage states and identification of the failure mechanism was examined using the advantages of full-scale testing. A novel cyclic loading test protocol was systematically applied to the shearwall assembly to capture the progressive damage starting from the initiation of elastic deformations to the near-collapse limit state. Shearwall assembly was tested until reaching the 1/21 rad interstory drift angle to determine the failure criterion of the shear wall assembly. Applied test procedure using a curtain wall test rig is useful and cost-effective for testing two different forms of systems to establish the damage pattern and deterioration characteristics of structural systems rather than only performing conventional tests for a particular structural system. At the end of the test sequence, gypsum wallboards were fallen apart due to the detachment of nails and out-of-plane buckling failure of diagonally brace. A numerical model incorporating negative stiffness branch in the backbone curve and all significant modes of cyclic deterioration of the P&B shearwall assembly is generated based on the energy-based hysteretic model. The generated numerical model and the test results were found compatible as a result of sensitivity analyses.

The first-order reliability method (FORM) is a prevalent method in the structural reliability community. However, when solving the high-dimensional problem with a highly nonlinear limit state function, FORM usually encounters non-convergence or divergence. In this study, an improved FORM combining Harris Hawks Optimization (HHO-FORM) is presented for high-dimensional reliability analysis. HHO is a meta-heuristic algorithm mimicking the predatory behavior of Harris hawks, and efficient in finding the global optimum of high-dimensional problems. In HHO-FORM, the reliability index is firstly formulated as the solution of a constrained optimization problem according to the FORM theory. Then, the constraints are handled with the exterior penalty function method. In addition, the optimal reliability index is determined by the Harris Hawks Optimization that accelerates the convergence by the population-based mechanism and the strategy of Levy Flight. The HHO-FORM does not require the derivatives of the limit state functions that reduce the computational burden for high-dimensional problems. So the simplicity of HHO-FORM greatly improves the efficiency in solving high-dimensional reliability problems. The HHO-FORM is firstly tested on three challenging numerical high-dimensional problems and then applied to two high-dimensional engineering problems to verify its performance. Four gradient-based FORM algorithms and four heuristic-based FORM algorithms are also compared with the proposed method. The experimental results demonstrate that HHO-FORM provides good accuracy and efficiency for high-dimensional reliability problems.