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In the field of the system reliability analysis with multiple failure modes, the advances mainly involve only random uncertainty. The upper bound of the system failure probability with multiple failure modes is usually employed to quantify the safety level under Random and Interval Hybrid Uncertainty (RI-HU). At present, there is a lack of an efficient and accurate method for estimating the upper bound of the system failure probability. This paper proposed an efficient Kriging model based on numerical simulation algorithm to solve the system reliability analysis under RI-HU. This method proposes a system learning function to train the system Kriging models of the system limit state surface. The convergent Kriging models are used to replace the limit state functions of the system multi-mode for identifying the state of the random sample. The proposed system learning function can adaptively select the failure mode contributing most to the system failure probability from the system and update its Kriging model. Thus, the efficiency of the Kriging training process can be improved by avoiding updating the Kriging models contributing less to estimating the system failure probability. The presented examples illustrate the superiority of the proposed method.

The concrete-faced rockfill dam (CFRD) is one of the widely constructed dam types, the concrete slab is the key anti-seepage structure of CFRD, and its safety directly affects the safety of the dam. In view of the traditional reliability analysis methods are complicated to calculate and cannot assess concrete slab cracking risk in real-time. In this paper, through the analysis of the response mechanism of slab stress and dam deformation, the coupling relationship between the reliability of concrete slab and monitoring data is revealed. Considering the randomness of the material parameters of CFRD, the limit state functions of concrete slab cracking are established by the response surface method (RSM). The accurate numerical simulation of the construction and operation process of CFRD is realized through the back analysis, then the time-variant reliability calculation of the concrete slab is realized. By analyzing the correlation between concrete slab reliability and some key factors such as dam displacement, water level, and time, a coupled evaluation model of reliability and monitoring data is proposed. Houziyan CFRD is selected as an example, the engineering application shows that the simulation relative error by using this coupled evaluation model is less than 5.0%, this model has the advantages of high efficiency, good precision, and strong applicability. The real-time reliability analysis of the concrete slab is realized and a new method for prediction and early warning of concrete slab cracking of CFRDs is provided.

The proper explicit testing with a rotation impact is wavering parabolical stream antique. It is an incomprehensive, electrical forceful liquid. Isothermal vertical plates are done standardized accelerated abundant lack magneto hydrodynamic described. T’W and the centre equal close to the vessel have been higher near C’w. The value by a plate degree and density grade closer to the plate are step-up constantly. This Logical methodology of the issue addressed the limit state with temperature. Fixations are t. Dimension - less equivalence was assimilated by using the Laplace approach. Velocity outline, climate, absorption shape is developed alternate bodily models corresponding deep (or) mass Grashof value, Schmidt value, prandtl value, rotational boundary, period. The velocity will venture rising appraisal deep Grashof rate. It is furthermore tried that the speed ventures up with diminishing rotational parameters.

Bridges are the essential parts of the transportation facilities and are subjected to various forces depending on the onsite conditions and specific location of the bridge. T-beam bridges are pivotal in commuting from one place to other especially in shorter spans. The major forces acting on the T-beam bridges are static load, moving load and seismic load. Design of the T-beam bridges is conventional and versatile, as the main components are beams and slabs. There are various methods for the design of RC bridges, depending on the safety and serviceability. The earlier bridges were designed based on the working stress method as safety was the only criteria. Nowadays, the design is based on safety and serviceability. Most of the short span bridges in India are constructed as per the design details of standard plans by Ministry of Surface transport, Govt. of India. The complete design details for RCC slab and T-beam bridges (volume II) are available for the span ranging from 10 m to 24 m. The design details are established on the basis of working stress method as per code IRC 21: 1987. Provisions of IRC-6:1985 for seismic loading has also been incorporated in the design details. At present, working stress method of design of RC Road bridges has been outdated and IRC 112: 2011 code is in use. The study is about, to check the suitability of standard design drawings for spans varying from 10 m to 24 m based on limit state guidelines. design details are checked for the suitability at all seismic zones. MIDAS Civil (2019) software has been adopted to conduct this study. Comparative study has been made for the suitability of the design details of all spans in all seismic zones as per the new code.

This paper presents the effect of plasticity and the limit states on the electrical resistivity of bentonite as grounding material. The material used in this study was extracted from Andrassy volcanic formations in Tawau district. The geotechnical properties such as the plasticity characteristic, water content and electrical resistivity of the bentonite were investigated. The electrical resistivity was measured at different limit state of the bentonite using a soil box and a 4-pin resistivity meter. In this study, the Andrassy bentonite showed appropriate composition and technical properties commonly associated in electrical grounding application. Test results indicated that the electrical resistivity is somewhat similar to most bentonites. The resistivity values were found to vary with the bentonite limit state. Water content greatly influences the electrical resistivity of the bentonite. Under dry solid-state, the resistivity is the highest at 11 kΩm. Surprisingly, under liquid state, three distinct resistivity values were observed. Under wet conditions, the resistivity were 4500, 180 and 1.8 Ωm for semi-solid, plastic, and liquid states, respectively. Thus, it is expected that bentonite performance as good grounding enhancement material depends on its wet conditions, mainly when the water content is greater than the plastic limit.

Whether UnReinforced Masonry (URM) infills should be employed as structural members in frame structures is a debatable subject in performance-based earthquake engineering. This paper presents a detailed assessment of the seismic response of infilled moment-resisting steel frames. A recently proposed multi-strut model is applied here to consider both the local and global effects of URM infills. The capability of the employed model in predicting the local and global effects of URM panels has previously been verified by the authors of this study. Two structures, a four-story building and a two-story building, were designed using seismic design codes, and one of the outer frames of each structure was selected for the numerical models. Based on the conventional layouts of URM panels in buildings, three different configurations are considered: the bare frame (model in which the URM panels are isolated from the surrounding frame), the infilled frame, and the soft-first story frame. Fifteen ground motion records have been used to perform nonlinear Incremental Dynamic Analyses (IDA), which were then employed to derive the fragility curves of the studied structures for the Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP) limit states. The results show that in lower limit states, the masonry infill leads to some beneficial effects. However, at more severe limit states, these beneficial effects diminish and at some point, revert to adverse effects. This is evident in the CP limit state, wherein the masonry infill weakens the seismic performance of the structure.

The dynamic response of modern slender footbridges is usually sensitive to both the pedestrian actions and the uncertainties associated with their inherent structural behavior. Thus, tuned mass dampers have been widely integrated in the design of these structures to guarantee the fulfillment of the vibration serviceability limit state during their overall life cycle. Three different techniques of tuned mass dampers (active, semi-active and passive) are usually considered for this purpose. Although there are algorithms for the robust design of each particular technique, however, this specificity makes difficult the implementation of all these techniques in practical engineering applications. Herein, the motion-based design method under uncertainty conditions is proposed and further implemented to create a common framework for the robust design of all these techniques when they are employed to mitigate pedestrian-induced vibrations in slender footbridges. According to this method, the design problem may be transformed into the combination of two sequential sub-problems: (i) a reliability multi-objective optimization sub-problem; and (ii) a decision-making sub-problem. Subsequently, the performance of this proposal has been validated through a numerical case study in which the dynamic response of a steel footbridge has been controlled by three different tuned mass damper techniques designed according to the proposed common framework.

The mega-sub controlled structural system (MSCSS) is a new structural system that combines structural response control theory with the construction principle of mega frame structure (MFS), and has significant response control effects. It is of practical significance to study the method which accurately evaluate the seismic vulnerability of structures. In this paper, Multiple Stripes Analysis (MSA) and Incremental Dynamic Analysis (IDA) are used to evaluate the vulnerability of MSCSS structure. The comparison between these two methods certify the accuracy of MSCSS vulnerability evaluation along with the impact of the number of stripes used in MSA method. In addition, through the comparative analysis of structural vulnerability analysis results, it is found that under limit state LS4, the failure probability of MSCSS is 30% lower than that of MFS, and the exceeding probability of megastructure is 50% lower than that of substructure, indicating that MSCSS structure has advanced disaster prevention design concept. Afterward, by introducing the seismic damage index used for regional structural seismic damage assessment into the vulnerability assessment, an intuitive seismic risk assessment method for buildings is anticipated by combining the seismic damage index and the beta distribution function, which can provide a reference for the risk assessment of super high-rise buildings.

Lateral responses of a pile are governed by its mutual interaction with the supporting soil, known as the Pile-Soil Interaction (PSI), which in turn influences its structural limit states. The present study evaluates the seismic limit states for bridge pile in sand, while incorporating the parametric influences of pile and soil assessed through PSI. Such influences have not been dealt with in the past, except for the p (soil-pile reaction) – y (pile deflection) responses (though with only few pile parameters). Pile cross sectional size, grades of concrete and reinforcement, longitudinal and transverse reinforcement ratios, axial load ratio and the sand effective friction angle are observed to affect the PSI and consequently the limit states. Thus, limit states are proposed as parameterised expressions, generated through regression on the limit state data obtained by analysing the damage model (developed herein) for the pile-soil system samples generated over wide ranges of the influential parameters. These expressions, validated through the compliance with the expected trends and a fair agreement with a test result, can be readily used to obtain the expected values of the limit states over a broad range of parametric combinations and without requiring analysis repetition. These, in turn, can contribute to reliable estimation of fragility of a bridge system with the given properties for its pile foundation.

The stiffness of the stiffener plate of a tube-gusset plate joint (TGPJ) with a multi-ring stiffener plate is much larger than that in the chord wall. The load on the gusset plate will be concentrated in the area where the stiffener plate is located, and the joint will eventually fail in this area as a result of the ultimate state of the ring stiffener plate. This study investigated the stiffness and ultimate strength of a ring stiffener plate under an axial load. First, an experimental study was carried out on X-shaped TGPJs with double-ring stiffener plates. The failure mode of the joints was clarified, the variation law of the joint stiffness was revealed, and the rationality of using a 3% chord wall deformation as the criterion for determining the ultimate state of joints was verified. Then, based on the test results, finite element models (FEMs) of the X-type joint and ring stiffener plate were established, and their accuracy was verified. Numerical analysis results clarified the synergistic mechanism of the double-ring stiffener plate of an X-type joint, and the equivalence between the joint failure and the single-ring stiffener plate failure was revealed. Different nominal yield strength parameters (345 and 420 MPa), different dimensions (D/t = 32.3–55.9 and R/tr = 6–33.3), and different load conditions (tension and compression) for ring stiffener plates were analysed, and the accuracy of the calculation methods for the limit state of the ring stiffener plates proposed in this paper was verified. A comparison showed that the ‘four-hinged ring beam model’ proposed in this paper did not consider the changes in the curvature of the ring beam between plastic hinges. Thus, the calculation results of the model were obviously conservative, and the ‘deformation stiffness model’ was more accurate than the calculation results of other methods mentioned in this paper.

Structural fuses can be implemented in buildings as steel plates subjected to shear loading. Strategically engineered cut-outs in these steel plates can be used to create shear fuses with energy dissipating capability. The structural fuses are used to protect the surrounding structure from damages and significant inelastic deformations, and then be replaceable after a major earthquakes. Previous studies indicate that structural fuses with shear fuses improve the initial elastic stiffness, energy dissipation capability, and ductility of structures. Butterfly-shaped fuses with varying width between larger ends and a smaller middle section have been used to better align bending capacity with the moment demand along the length of the fuse. These fuses have been shown in previous tests to be capable of substantial ductility and energy dissipation. In this study, equations are developed to capture load–displacement behavior of butterfly-shaped and straight shear fuses. The butterfly angle, defined as the angle between intersections of the inclined edges at the middle of the fuse, is investigated. Using the flexural and shear limit state equations, the critical butterfly angle identifying the transition from the shear to flexure is proposed. Subsequently, equations describing the geometric hardening of butterfly-shaped shear fuses are proposed. Along the same lines, the stiffness of a typical butterfly-shaped fuse is developed by dividing the stiffness into four major parts: fuse flexural deformations, fuse shear deformations, and shear and flexure deformations of the end zones. In addition, the post-yielding hardening behavior is investigated considering axial forces generated under shear loading deformations. Subsequently, computational finite element models are presented and validated with laboratory tests for two different configuration examples to examine the implementation of the proposed limit state prediction. To verify the provided applicability of the proposed analytical equations, a set of computational models are considered, and the associated backbone behavior of the models are compared with their corresponding proposed equations. The procedures presented in this paper to predict the behavior of fuses could be useful for the design of butterfly-shaped fuses with more than 90% accuracy in predicting the backbone behavior of the fuse system.

A novel method for bamboo scrimber strengthening timber beams with anchorage structures was proposed. Bamboo scrimber was adhered to the bottom of the timber beam and anchored with carbon fiber-reinforced polymers (CFRPs) or wooden pins. Through the bending tests of eight reinforced beams and two control beams, the effects of different forms of anchorage and thicknesses of bamboo scrimber on the strengthening effect of timber beams were studied. The failure characteristics of the timber beams were observed, and the ultimate load, stiffness and ductility were analyzed. The results show that the failure modes of timber beams can be divided into bending failure and bending-shear failure and that the timber beams exhibit obvious signs of ductile deformation before failure. The ultimate bearing capacity of the reinforced beams increased by approximately 20%–70%, and the cross-sectional stiffness at the serviceability limit state increased by approximately 40%–160%. The test results confirm that CFRPs and wooden pins can firmly adhere to the timber beam and bamboo scrimber, so the bamboo scrimber strengthening timber beams with anchorage structures can substantially increase the ultimate bearing capacity and stiffness and improve the ductility of the member.

This paper takes common masonry structures built in mountainous areas prone to debris flow as a research object and proposes carbon fiber-reinforced polymer (CFRP) to improve the resistance of the structures under debris flow impacts. According to a series of impact loading tests on an unreinforced model (hereinafter referred to as UM) and a CFRP-strengthened model (hereinafter referred to as CM), dynamic responses and failure mechanisms of these two structures under debris flow impacts are analyzed. To simulate the impact of large boulders in debris flows, steel balls with different diameters are placed on a loading device, and they roll down along the track from different heights to input homologous impact energy to the scaled models. The test results reveal that the maximum peak acceleration of the CM is only 51.3% of that of the UM, and the peak displacement of the CM is 50% of that of the UM, while the residual displacement is 65% of that of the UM (under the loading case G6 in this paper). When the models reach the serviceability limit state (defined in this paper), the absorbed impact energy of the CM is 7.35 times that of the UM. The test results show that CFRP is an effective reinforcement material to significantly improve structural bearing capacity and reduce dynamic response of structures under debris flow impacts. This study will be helpful for building construction and reinforcement in mountainous areas prone to debris flow impact.

The perfobond connector is the most widely used connector in the steel–concrete joints of long-span hybrid bridges, and the behavior of the perfobond connector group directly determines the reliability of the connection and the smoothness of force transmission of the joint. However, the existing model test can only reveal some of the connector group’s information in the joint, which leads to the force transfer mechanism of the joint group remaining unclear. To solve these problems, establishing the numerical and theoretical models is necessary. Numerical analysis shows that the stress of the connector on the steel beam loading side is far greater than that on the concrete loading side at the initial stage of loading, and the connector has enough slip capacity to ensure the uniform distribution of interface shear when it reaches the limit state. The reduction of connector spacing weakens the effective support on the concrete dowel and then reduces the shear capacity. In terms of theoretical analysis, four factors determine the interface slip distribution: the length of the steel–concrete joint, the interface stiffness, the axial stiffness of concrete members and the axial stiffness of steel members. The increase of the interface stiffness and the steel–concrete joint length can decrease the maximum slip and reduce the effective utilization ratio of the connector group. When the axial stiffness of concrete or steel members tends to be the same, the effective utilization ratio of the whole group of connectors can improve. Finally, the simplified calculation formula of the maximum slip Smax, the effective utilization ratio μj of the connector group and the load ratio ξj of the connector are put forward.

The current paper presents an experimental investigation on the working mechanism of pre-stressed steel strips, used for the strengthening of brick masonry walls when subjected to axial loads. Three strengthening schemes were used, involving vertical and in some cases horizontal strips, with or without pre-stress, installed onto the walls through binding bolts. A total of nine unreinforced masonry walls were prepared and tested up to failure, by using the level of pre-stress on the steel strips as well as the axial preload level on the walls, as parameters. The test results showed that pre-compression on the vertical strips increases the crack initiation and the crack distribution loads by percentages as high as 60%, and 50% respectively, whereas the level of preloading, not resulting in the initiation of cracking, do not play a significant role in the overall behavior of the walls. Pre-tension on the horizontal steel strips on the other hand, controls the behavior of masonry at the ultimate limit state and increases the axial load bearing capacity of the walls by almost 43%. Moreover, the pre-tension on the horizontal strips, enhances the lateral support conditions of the vertical counterparts and changes the post-buckling behavior from unstable to stable. In general, the intervention scheme which involved pre-stressing in the horizontal strips performed better, in terms of the ultimate and the serviceability limit states. Based on the observed behavior of the strengthened walls, a design procedure is proposed with the use of a failure criterion for bi-axially compressed anisotropic masonry.

Accurate structural reliability assessment of floating wind turbine (FWT) systems is a desideratum for achieving consistent optimal reliability levels and cost-effective design. Such reliability assessment should consider relevant system uncertainties—a nontrivial task. Formulation of the reliability problem requires structural demand in form of load and load effect. Support structure loads are predicted with time-domain dynamic simulations. This represents a challenge when thousands of such simulations are required to capture the uncertainty associated with design variables. Finite element analysis (FEA) is commonly used to evaluate load effects such as stresses, strains etc. This can be computationally expensive if not prohibitive when such evaluation is carried out for every time step. To tackle these issues, a framework for expeditious load effect computation and robust reliability analysis of FWT support structures under ultimate limit state design is presented. The framework employs linear elastic FEA and Kriging surrogate models. The adequacy of Kriging as applied in this study is investigated using high fidelity simulation data. The results highlight the importance of incorporating the Kriging uncertainty in the formulation of the limit state function. With the framework presented, FWT support structures can be designed at consistent reliability levels leading to cost reductions.

Geosynthetic reinforced column supported embankments predominantly utilise two mechanisms to transfer embankment loads towards column heads, soil arching and membrane actions. When undertaking the design of column supported embankments, it is common practice to perform a two-step design, whereby the arching actions are estimated independently of the subsoil deformation and membrane actions. This approach is unable to capture the deformation dependency exhibited by both arching and membrane actions. This paper presents deformation dependent arching and membrane action models and implements them within an interaction diagram. It is shown that an interaction diagram-based design approach is capable of performing an ultimate and serviceability limit state design of a geosynthetic reinforced column supported embankment. In contrast, most existing analytical design methods only consider the ultimate limit state. The proposed method is applied to a design example where the benefits of such a design approach are demonstrated.

The paper addresses the reliability change of a road bridge pile foundation due to the unpredictable increase of settlements in time. The analysis is based on the Redzinski Bridge in Wroclaw, Poland, its design assumptions, and monitoring results. The bridge foundation rests on a multi-layered subsoil assumed random. The Finite Element model of the subgrade is generated in ZSoil® software. To simplify the probabilistic approach, substitute soil strata stiffness parameters are adopted. Tracing their time decrement allows for a comprehensive definition of the entire foundation over-settlement produced by numerous factors. Preliminary sensitivity analysis of settlements to the stiffness variation properly simplifies the random model. The Serviceability Limit State helps to assess the foundation reliability index, further compared with the condition in the EN 1990:2002/A1:2005 standard. In addition, real-life settlements are also measured in the first year of bridge operation, they are used to calibrate the reliability index assessment. An innovative approach is proposed, where appropriate time-wise fluctuation functions represent the expected settlement increase and the related reliability reduction. These fluctuation functions help to plan the future remedial actions to maintain the initial bridge safety and to indicate the action frequency and scope. Future reliability levels may be extrapolated too. The real-life survey database of settlements makes it possible to validate the results of probabilistic calculations. A dedicated flowchart is devised to support further analysis of a wide structural domain.

In this paper, a new genetic algorithm-based framework aimed at efficiently design multiple seismic retrofitting interventions is proposed. The algorithm focuses on the minimization of retrofitting intervention costs of reinforced concrete (RC) frame structures. The feasibility of each tentative solution is assessed by considering in an indirect way the expected annual loss (EAL), this evaluation is performed by referring to different limit states whose repairing costs are expressed as a percentage of reconstruction costs and evaluating the respective mean annual frequency of exceedance. As the EAL takes into account the overall structural performances, to involves both serviceability and ultimate limit states, two different seismic retrofitting techniques are considered. In particular, FRP wrapping of columns is employed to increase the ductility of RC elements managing life safety and collapse limit state demands. On the other hand, steel bracings are used to increase the global stiffness of the structure and mainly increase operational and damage limit states performances. The optimization procedure is carried out by the novel genetic algorithm-based framework developed in Matlab® that is connected to a 3D RC frame fiber-section model implemented in OpenSees. For both the retrofitting systems, the algorithm provides their position within the structure (topological optimization) and their sizing. Results will show that seismic retrofitting can be effectively designed to increase the overall structural safety by efficaciously optimizing the intervention costs.

Despite realizing the importance of risk-based frameworks in fire engineering, current fire safety guidelines are largely prescriptive and over-conservative in nature, which do not consider the effect of uncertainties influencing the fire resistance of the structural systems. In this context, a probabilistic framework is presented to investigate vulnerability of a reinforced concrete (RC) portal frame subjected to fire. Here, a three-dimensional (3-D) nonlinear finite element (FE) model for the RC portal frame exposed to elevated temperature is developed, and transient thermo-mechanical analysis is carried out by duly incorporating temperature variation of thermal and mechanical properties of concrete and steel rebar. Probabilistic study is conducted by developing fragility curves based on limit state of deflection to quantify the vulnerability of the structural members exposed to fire loading. Parametric studies are conducted by varying the material properties of the RC portal frame to investigate the influence of uncertainties in the fire loading on its structural performance and fragility. The failure probability starts at a higher fire load density (450 MJ/m2) for the structure with higher concrete grade as compared to the relatively lower fire load density (200 MJ/m2) for lower grade. Therefore, the fire resistance of the RC structures has been recommended to be based on the strength of the member, rather than merely sizes of the members. The proposed stochastic analysis framework, thereby, provides a rational approach to improve the performance-based fire design of RC structures at member and structure levels by identifying the parameters affecting the structural fire resistance.

Adopting crushed coal gangue as aggregates for new concrete production could be a sustainable alternative to natural aggregates and could reduce landfill space. For the structural applications of innovative concrete, the elastic modulus is a key parameter influencing its serviceability limit state. Prediction models are presented herein for the elastic modulus of concrete prepared with coarse coal gangue aggregates (CGAs), including spontaneous-combustion coal gangue aggregate (SCGAs) and rock coal gangue aggregate (RCGAs). Experimental data from our previous studies and other literature were first collected to quantify the effects of the replacement ratio of CGAs, as well as the density and compressive strength of CGA concrete on the elastic modulus of the resulting concrete. Based on our previous experimental data, empirical models were proposed and validated against 150 groups of tested data. The obtained results indicated that the replacement ratio of CGAs is the major factor, and there were up to 57% and 41% reductions in the elastic modulus of the resulting concrete prepared with 100% SCGAs and RCGAs, respectively; by considering the replacement ratio, compressive strength and density of concrete, the newly proposed models in this study estimated the elastic modulus of both SCGA and RCGA concrete accurately.

Eight structural fire tests on an aluminum alloy shell specimen are conducted in this paper. Firstly, the test program is described in detail. Then, test results, including the test phenomenon, the temperature-time curves, and the displacement-time curves, are exhibited. In the structural fire tests, the specimen under ventilation-controlled fires had greater thermal and structural responses. The maximum measured air temperature was 128 ℃, and the maximum temperature of the members and the gusset plates were 85 ℃ and 80 ℃, respectively. The specimen performed arching during the test process, and the maximum displacement was smaller than the restriction value for the serviceability limit state in existing design codes. After all the tests, no damage that would influence the structural behavior was observed. Subsequently, based on the test results, two approaches, namely the empirical formula and the field simulation, are proved to be useful to predict the non-uniform temperature distribution. Finally, the global deformation patterns, the distribution of internal forces, and the variation of the ultimate bearing capacity of the shell specimen, are analyzed through numerical analysis. The results indicated that the fire located at the corner is more disadvantageous to the specimen.

The paper demonstrates deterministic and reliability-based assessment of strength limit states (tensile resistance and pullout) and the service limit state for soil failure for mechanically stabilized earth (MSE) walls constructed with polyester (PET) strap reinforcement. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty in the estimate of nominal load and resistance values at time of design. Reliability index is computed using a closed-form solution that is easily implemented in a spreadsheet. Three PET strap MSE wall case studies are used to demonstrate the reliability-based assessment approach and to compare margins of safety using different load and resistance model combinations. In some walls using the Coherent Gravity Method to compute loads, the recommended nominal factors of safety for tensile strength and pullout limit states were not satisfied. However, reliability analyses showed that the walls satisfy recommended minimum target reliability index values for the limit states investigated, usually by large amounts. The most critical limit state is the soil failure limit state which is used in the Simplified Stiffness Method to keep the reinforced soil zone at working stress conditions assumed for geosynthetic MSE walls under operational conditions.

Precast construction of caps is adopted to reduce on-site construction time and facilitate installation. A corbel joint (CJ) is proposed as an innovative joint form to improve the mechanical behaviour and construction performance of precast concrete segmental inverted-T caps. To obtain a further understanding of the failure modes and resistance mechanisms of CJs subjected to combined shear and bending, eight cap specimens with different shear-span ratios (1.61, 2.37, and 3.89) and joint types (CJ, monolithic concrete, and straight joints with a single tooth or multiple teeth) were match cast and tested. The experimental results showed that the CJs achieved superior mechanical and deformation performance and higher bearing capacity compared to conventional straight joints. Owing to corbels intercepting cracks, the CJs were not fully opened similar to straight joints at the limit state. Furthermore, the reinforcement in the corbels reached the yield strength, which suggested that the CJs could transfer the shear force between two adjacent segments effectively and reliably. When the shear-span ratios changed from 1.61 to 3.89, the ultimate shear force in the joint plane reduced by 57.9%, while the ultimate bending moment increased by 5.2%. Therefore, the ultimate shear and bending moment of the CJs were correlated.

In engineering applications, narrow backfills are often squeezed by retaining walls. Insufficient information is available with respect to the passive earth pressure, whereas the active earth pressure of narrow backfills against retaining walls has been considerably investigated. In this study, the passive failure mechanism of a narrow cohesionless backfill under translation mode has been investigated via a finite element lower-bound limit analysis, considering the effect of backfill geometries and external friction on the failure mechanism. Multiple-slip surfaces could be observed in a narrow backfill in the passive limit state. Further, we summarized the number of slip surfaces under various conditions and proposed a fitting function for the inclined angles of the slip surfaces. In addition, a multiple-slip surface calculation mode was developed. Subsequently, a method was derived for calculating the passive earth pressure of a narrow cohesionless backfill using the differential slice element method, the wedge limit equilibrium, and the finite difference method. Parametric studies explored the effects of the backfill geometries and internal and external frictions on the passive earth pressure. The results demonstrated an increase in the passive earth pressure and the number of slip surfaces when the backfill space decreased, in which the passive earth pressure was nonlinearly distributed.

Bond stress-slip behavior between the reinforcing steel and the concrete is one of the basic properties which influences the performance of the structure at the serviceability as well as at the ultimate limit state. However, this behavior changes with the exposure to elevated temperatures. Bond slip behavior after exposure to elevated temperatures have been studied using pull out specimens because of its ease of operation and economy. These specimens do not simulate the actual state of bond stress in reinforced concrete structures during testing. Therefore, an experimental study was conducted to investigate the effect of elevated temperatures on the bond behavior between reinforcing steel and concrete using splice beam specimen. The specimens were heated to three temperatures of 350 °C, 550 °C and 750 °C inside the furnace at a rate of 5 °C/min till the desired temperatures are achieved. The specimens were tested under four point bending to obtain i) relative slip between steel and concrete, ii) strain in the reinforcing bar and iii) mid span deflection of the beam specimens. The results show that the bond stress between reinforcing steel and concrete decreases after the exposure to elevated temperature while there relative slip increases. The reduction in bond stress is significant after the exposure to 550 °C. The reduction in the bond strength at a temperature is directly proportional to the reduction of its compressive strength at that temperature. A shift in the failure mode was observed in the beam specimens from a more brittle to a gradual failure after the exposure to 550 °C. Prediction of the bond strength for the beam specimens after elevated temperatures were also made using elastic, plastic and elastoplastic analysis based on thick wall cylinder theory. The analysis shows that the prediction based on plastic analysis overestimates the bond strength at elevated temperatures while the elastic and elastoplastic analysis shows conservative results. Based on the analysis, a model is proposed, which can predict the bond strength of splice beam specimens after exposure to elevated temperatures with considerably good efficiency.

The Butterfly-shaped Link Steel Plate Shear Wall as a novel lateral resisting system is proposed and experimentally investigated. In this system, by creating the peripheral Butterfly-shaped links in the web plate, the lateral load resisting mechanism is determined by the shear strength of the links. The geometric attributes of the links are effective parameters for predicting the values of stiffness and strength of the proposed system, as investigated in this paper. To fulfill this aim, four experimental specimens with different geometric parameters containing the taper, slenderness, and width ratios are constructed. The samples are loaded by using the cyclic loading protocol to investigate the behavior of the system. The experimental results confirm that the link dominant limit state controls the stiffness, strength, and ductility of the specimens. The Butterfly-shaped link geometry with the dominant shear limit state results in higher stiffness and strength, and the link geometry with a dominant flexural limit state shows the higher ductility. Besides, the hysteresis diagram of specimens shows the optimal ductility and high energy dissipation even at low drifts. Then, by numerical modeling verification, Butterfly-shaped Links Steel Plate Shear Wall with the restrained web plate is intended to improve the cyclic behavior. The principal purpose of the numerical study is to investigate the restrainer's impact on the energy dissipation capacity of the samples. The results show that the out-of-plane instability is reduced, the pinching phenomena eliminated, and the dissipated energy of the specimens is increased considerably by the web plate restraining.

In this study, the reliability assessment of the system of structure-MR damper in controlling seismic responses of the structure via semi-active control is studied. In this regard, numerical results are presented for two different examples including three and ten-storey shear structures. The limit state functions are defined based on the control responses obtained from the use of MR dampers in the structure stories. By defining several uncertainties in parameters of the structure-MR damper system, probability of failure of structure is obtained using weighted uniform simulation (WUS) method and compared with the results of traditional Monte Carlo Simulation (MCS). Moreover, the most probable point of failure, which cannot be calculated by MCS, is determined for each uncertain event. Graphs of system reliability are derived and interpreted. The results show satisfactory performance of the WUS method in the reliability analysis of smart structures. The results also indicate that reliability of the system is highly dependent on the mass uncertainty of the structure. Moreover, the highest probability of failure takes place when all parameters are considered to be simultaneously uncertain.

This study proposes an analytical method for the calculation of the safety factor against lateral spreading in embankments, both for cases with and without basal reinforcement. Hence, a new limit equilibrium approach is presented based on the lower bound plasticity theorem, which allows the computation of the required distribution of stresses along presumed slip surfaces at the limit state. Comparing the required distribution of stresses with the available resistances, the safety factor in the absence of basal reinforcement is calculated. If the safety factor is unsatisfactory, basal reinforcement can be introduced and its contribution to stability quantified. The lower bound approach allows the computation of mobilized resistance along the reinforcement. Accordingly, the proposed method allows the calculation of the safety factor against lateral spreading for problems involving basal reinforcements. Finally, the proposed method is compared with well-established methods in literature. Results suggest that the proposed method is reliable, practical, and applicable to safe and economical designs.

This study focuses on the stability of stone column-supported and geosynthetic-reinforced embankments on soft soil. An upper-bound limit state plasticity failure discretization scheme (known as discontinuity layout optimization (DLO)), which determines the embankment stability without pre-assuming a slip surface, is used. The relationships between the stability of stone column-supported and geosynthetic-reinforced embankments and various influencing parameters, including the soil strength, geometric configuration, reinforcement strength, and area replacement ratio, are analysed. It is found that geosynthetics provide a significant contribution to embankment stability. Two failure mechanisms of geosynthetics (i.e., rupture failure and bond failure) are revealed and the effect of geosynthetics on embankment stability is governed by the failure mode. The application of stone columns mitigates the risk of geosynthetic failure. To provide an analytical solution for primary design in engineering practice, an approach based on the limit equilibrium method is proposed. Validations are performed with the DLO solution to demonstrate the accuracy and reliability of the developed analytical approach.

This study introduces an efficient method for safety evaluation of the structures with small failure probability. The proposed approach reformulates basic failure probability formula based on control variates method and suggests to firstly substitute the nonlinear limit state function with a linear limit state function for taking the advantages of linear problems during reliability process. Reliability analysis of linear problems would be fully accurate and dimension insensitive. Subsequently, the control variates method imposes the effect of limit state function nonlinearity on the obtained first-order failure probability by using a very small sampling size simulation. The result is a new reliability formulation that is highly suitable for solving nonlinear and high dimension problems. The capabilities of the method examined by solving several benchmarks numerical/engineering problems involving non-normal random variables, complex/noisy limit state functions, and nonlinear high dimension problems. Compared with mainstream reliability methods, for all solved problems, it is demonstrated that the proposed approach presents accuracy close to Monte Carlo simulation while the required number of performance function valuation is close to first-order reliability method.

Currently, the problem of restoring the service reliability of residential multi-storey buildings in ultimate limit state is an urgent problem. Basically, buildings that are in the emergency group have an excess of standard building tilt. This problem is solved, most effectively, by lifting and leveling by means of the hydraulic robot-based system. In the aforementioned system, including the hydraulic part, a system of sensors, control of geometric characteristics, and a management software, when lifting a building, the comparison of measurement results from two groups of sensors is performed. The first group of sensors is linear displacements installed in the area of ​​the separation cavity and monitoring the amount of movement of the building relative to its base. The second group of sensors – building tilts installed on horizontal and vertical bearing structures of buildings, monitor the change in the leans and tilts of building structures. The software provides a comparative analysis of two information flows, evaluates their identity and adequacy, and performs a control action on the hydraulic part or on the continuation of the lifting procedure, or on the termination of this action.

Today, most energy companies face serious problems with the reliability and safety of large power equipment due to the long-term operation at off-design modes. This is especially true for hydraulic units that are traditionally used to ensure the required level of energy output and maintain the stability of a power grid due to their maneuverability. Off-design operational modes cause increased loads and stresses in the unit’s components, accelerate the growth of defects, stimulate premature failures, and can lead to a grave accident with large losses. Standard diagnostic systems for hydraulic units usually do not allow tracking hazardous defects such as fatigue cracks in the runner blades, guide vines, shaft, etc. The individuality of hydraulic units also excludes the use of any statistical methods to determine the time when the equipment will go to the limit state and its operation will become unreasonably dangerous. Therefore, the predictive analytics system is proposed as an additional approach to forecasting the appearance and growth of dangerous operational defects. The system realizes an analytical algorithm based on evaluating the fatigue strength of hydraulic unit elements under variable operating conditions and allows summing up damage from various external loads and in different time ranges. Input data for this predictive system is information about the actual operating time at every working mode and expected regime parameters for the upcoming period. The output data is information about actual and residual lifetime. All individual features are taken into account by the digital model which is a multidimensional matrix of equipment’s response to external influences. Data is generated in the cells for each unit’s elements with reference to the operating parameters and time scale. The proposed predictive analytics system allows not only to reduce the risk of accidents and unplanned shutdowns but it also is a way to smart maintenance of hydraulic turbines due to the development of the most effective, most reasonable, most lifetime-saving strategy of using the equipment.

Stainless steel reinforcement has become a very attractive option for reinforced concrete structures owing to its distinctive properties including outstanding corrosion resistance, excellent fire behaviour, long life cycle as well as low maintenance requirements. Additionally, stainless steel reinforcement offers exceptional ductility and strain hardening characteristics compared with other common materials, which are very desirable in design to avoid sudden collapse. However, most global design standards do not incorporate an appropriate design approach for reinforced concrete members with stainless steel. The substantial strain hardening characteristics of stainless steel are typically not represented in standardised material models and therefore this attractive characteristic is not exploited in design resulting in structural and economic inefficiencies. Hence, the aim of this paper is to propose and validate a new deformation-based design approach for stainless steel reinforced concrete beams based on the continuous strength method, with reference to the current design rules provided in Eurocode 2. This approach is shown to be an effective design tool that exploits the distinctive characteristics of stainless steel reinforcement in an efficient and reliable manner. It is shown to provide a more efficient design with less over-conservatism and greater accuracy, compared with other methods. A comprehensive parametric study is conducted using Abaqus software to study the influence that various geometric and material properties have on the capacity of the members. Moreover, the serviceability limit state is also explored through a detailed analysis of the deflection behaviour.

This paper presents a probabilistic limit state framework for the evaluation of the base resistance of drilled shafts in soft rock. In situ load tests and the Griffith fracture theory are used to evaluate the mode of failure for the rock mass under the drilled shaft base. The base resistance or the limit state in the context of this paper is defined by the contact pressure at which load induced vertical to subvertical cracks form and the contact pressure-displacement relationship passes into a steep and fairly straight tangent. The parameters affecting the base resistance are evaluated using an in situ load test database. A statistical approach using the maximum likelihood method is utilized for the development of the design model for the base resistance. Reliability analysis is used to calibrate the corresponding resistance factors. The in situ load tests and the Griffith fracture theory suggest that the soft rock mass underlying the drilled shaft base primarily fails by the formation of vertical to subvertical cracks. Field observations indicate that the displacements in the underlying rock mass are largely in the vertical direction and that the base displacements required to mobilize the proposed base resistance are generally less than 30 mm. Load test data show that the base resistance is chiefly related to the unconfined compressive strength of soft rock. The calculated resistance factors are found to slightly decrease with increase in the span length of the structure and increase with the increase in the foundation redundancy.

Fiber-reinforced polymers (FRP) are being used in reinforced concrete structures featuring their lightweight, high tensile strength, nonmagnetic, and corrosion resistance properties, contrasting conventional steel reinforcement. However, low bend strength, anisotropic and non-plastic nature of FRP composites are the major concerns for their assertive applications in construction industry. Pultruded FRP bar stirrups are characterized by premature failure either due to slippage at overlapping region or rupture at bend portion due to kinking of fibers. In this experimental study, close-type direct wound rectangular cross-section CFRP sheet strip stirrups (CSS) were proposed to mitigate the shortcomings of pultruded CFRP bar stirrups (CP). Total of seven full-scale beam specimens reinforced with steel longitudinal bars and CFRP stirrups were cast and tested to investigate the performance of proposed stirrups. The main study parameters include shear reinforcement material type, the cross-sectional geometry of CFRP stirrups, and the inclination angle of CSS stirrups with the beam axis. Specimens reinforced with CSS stirrups provided better shear capacity and crack control ability compared to steel and CP stirrups for same shear reinforcement ratios. Shear capacity of beam corresponding to serviceability limit state was improved up to 13% by changing the inclination of CSS stirrups from 90° to 45°.

This study proposes a new reliability sensitivity analysis approach using an efficient hybrid simulation method that is a combination of subset simulation, importance sampling and control variates techniques. This method contains a probability term (a fast-moving by subset simulation) and an adaptive weighting part that improves the calculated probability. The Finite Difference Method is used to obtain reliability sensitivities, and the related formulation is derived. Five numerical examples (four-branch model, beam-cable system, one-story frame, ring-stiffened cylinder buckling, and 25-bar steel truss) are presented to describe the applications of the proposed method. The results are compared with those obtained by the available techniques. The results revealed that the proposed method efficiently and accurately solves rare-event, system-level, and real-world engineering problems with explicit and implicit limit state functions.

Cement-fly ash-gravel (CFG) piles comprise one of the novel ground-improvement methods. They are attracting considerable attention, as their beneficial role in accessible soft foundations is being increasingly exploited by the surging urban industrial development in China. Despite their recognised significance, however, the load-settlement behaviour of CFG piles is poorly understood, particularly in the context of probabilistic assessments. This study focuses on six full-scale CFG pile load test datasets, consisting of 245 samples collected at six sites in the Beijing region, under static axial compression loading. As a part of this investigation, a regression curve is applied to the load-settlement data for each load test in the database using a two-parametric hyperbolic or power law curve-fitting equation. Moreover, an assessment of the multiple load-displacement curves, based on the full set of pile load measurements conducted at a particular test site, reveals that the scatter observed in the regression parameter values is mainly caused by the inherent soil variability. Thus, a bivariate copula-based mixed distribution is chosen to represent the dependence between these regression parameters. A simple copula-based simulation model is used to estimate the reliability index at any specific allowable settlement for the serviceability limit state (SLS) design. The correlation coefficients in the copula-based distributions of the regression parameters are proven to have an impact on the reliability index of this pile foundation. A scatter analysis of the load-displacement behaviour provides insight into the probabilistic design of site-specific CFG pile foundations.

Beam-column joint is one of the most vulnerable portions of a building during an earthquake. Sufficiently ductile materials are required to reinforce these joints so that the structure can dissipate energy and exhibit better performance during seismic events. Superelastic Shape Memory Alloys (SE SMAs) are unique materials that have the ability to undergo large inelastic deformation upon stress removal (superelasticity) or heating (shape-memory alloy effect). If such smart materials can be incorporated in the plastic hinge regions of reinforced concrete (RC) beam-column joint sub-assemblage, they can undergo large deformations without experiencing permanent deformation during an earthquake. In this context, this paper discusses the seismic performance of RC beam-column joint sub-assemblages reinforced with five different SMAs, obtained through numerical study, under reverse cyclic loading. In this study, six beam-column joint sub-assemblages, five reinforced with different types of SE SMAs, and one with regular steel, are considered. The performance of the beam-column joint sub-assemblages is numerically evaluated in terms of load-storey drift relationship, energy dissipation capacity, and cumulative energy dissipation-storey drift ratio. Nonlinear static pushover analysis is also carried out to determine the performance-based limit state for the beam-column joint sub-assemblages. The results indicate that all the SMA reinforced beam-column joint sub-assemblages have adequate energy dissipation capacity while experiencing lower residual deformation.

Many variables affect the sealing performance, and their distribution characteristics are difficult to obtain with probabilistic methods owing to the high cost involved. Numerous problems in engineering are similar due to the appearance of small-sample parameters. In this study, the sealing reliability of an aviation seal was defined as the research object, and an interval uncertainty method and multidimensional response surface were proposed to calculate the sealing reliability. Based on this, we first analyzed the failure mechanism of the aviation seal and established a leakage rate model. Then, based on the non-probabilistic interval model, an interval uncertainty method was proposed to construct the analytical model. With reference to the limit state equation from the structural reliability theory, the multidimensional response surface was used for fast calculation. Then, we chose the single-cylinder gas steering gear used in aircraft as the case study, its sealing reliability in working and non-working statuses were calculated, and the results were verified with the actual maintenance records. By analyzing the sensitivity of some variables, we can improve the sealing reliability of the aviation seal by improving the surface roughness only if the cost allows. Finally, we consider that the method proposed in this study realizes the application of small-sample uncertainty analysis in reliability analysis, and could provide a feasible way to solve the similar problems in engineering with multidimensional and small-sample parameters. Keywords: Aviation seal, Interval uncertainty method, Multidimensional response surface, Sealing reliability, Small-sample parameters

In the present paper the structural behavior of under-designed existing structures is investigated. The analyzed existing structure is assumed as originally designed in the past with respect to old codes and with respect to gravitational loads only. The under-designed structure is considered to be located in Italy in an area now classified by the new codes as high seismicity zone. In the investigation traditional and innovative steel braces are modeled and compared for the retrofitting of the structure by using a finite element analysis with a displacement based approach. With respect to a traditional retrofitting strategy the adopted retrofitting strategy with innovative steel braces allows a localization of the input seismic energy into the innovative steel braces which are endowed with dissipative properties and thus a better performance of the original existing structure is noted in the elastoplastic range. With respect to a traditional retrofitting system the innovative steel braces applied to under-designed existing structures show to provide a more robust nonlinear behavior of the under-designed structure and a significant reduction of the plasticization in the original existing structural frames when they are subject to dynamic events. These features are associated to a vulnerability reduction of the under-designed existing structure also at the ultimate limit state.

Non-structural components contribute significantly to the lateral stiffness of a cold-formed steel (CFS) building structure, but are cumbersome to model explicitly in the structural analysis. They are therefore commonly ignored in a 3D structural analysis, and their benefits are lost to the design. This paper proposes an efficient modelling method that enables practical and accurate 3D elastic analysis of a multi-storey CFS building structure to study its lateral behaviour within the serviceability limit state. Each shear or gravity wall is represented by an equivalent shear modulus four-node orthotropic shell element, which incorporates the lateral stiffness (or flexibility) contributions of all components including sheathing, braces and fasteners as present in the wall. The equivalent shear modulus is determined from the experimental test of a representative wall panel, or from the analysis of a finely detailed finite element model of the panel. The resulting two-storey building model, which has much fewer degrees of freedom compared to conventional models, is verified against full-scale shake table test results with respect to the natural period, the peak storey drift and the peak floor acceleration at two different construction phases. This paper demonstrates that the proposed modelling method not only saves analysis time considerably through the drastic reduction of degrees of freedom, but also compares favourably against a published modelling method in terms of accuracy and modelling efforts.

Evidence theory can be used for propagation analysis of structural response with various uncertainties because of its much more flexible and universal framework. However, the discrete characteristic and the ambiguity measure of the propagated result have severely influenced the practicability of evidence theory. Because of the basic probability assignment (BPA), the evidence domain is a countable region composed of all focal elements. Hence, in this study, an efficient uncertainty propagation method is proposed through evidence domain analysis. A multiple linear segment approximation for limit state equation (LSE) rather than structural performance function is firstly constructed, so the support degree of each focal element is directly judged in evidence domain. Then, the belief (Bel) measurement and plausibility (Pl) measurement are calculated by the positional relation of each focal element in the uncertain variable domain without involving response domain. Meanwhile, a volume ratio that can represent the proportion of focal element partly supporting event is calculated by utilizing the approximate LSE. Therefore, a maximum entropy probability measurement between the Bel and Pl can be provided using the volume ratio. One numerical example and two engineering applications are investigated to demonstrate the effectiveness of the proposed method.

When evaluating the probabilistic seismic performance of a structure in the context of Performance-Based Earthquake Engineering (PBEE) applications, only estimates of the true response are obtained due to the finite size of the group of records selected to represent the seismic scenario. The proposed study examines the variability of these estimates, in terms of fragility parameters and failure rates, by implementing a procedure that creates seismic scenario-consistent groups of records based on regrouping criteria applied to a larger set of records. The results are then compared to those obtained from a statistical approach based on the bootstrap resampling procedure, whose validity is disputed due to its incompatibility with common applications involving probabilistic seismic performance assessment. Given that bootstrap resampling assumes that each bootstrap sample is random, this condition is incompatible with requirements involving the need to match specific spectral statistics of the group of records with a target spectrum. Due to the increased computational cost of the procedure based on regrouping criteria, the effect of this incompatibility is analysed by examining the agreement between the two procedures for several case studies and the conditions under which bootstrap resampling leads to a reduced level of error. Further insights about the variability of the estimates are obtained by analysing scenarios with deterministic and probabilistic thresholds of the limit state capacity. Among other aspects, the results show that, for both capacity thresholds, bootstrap resampling can provide acceptable results as long as a sufficient number of ground motions and number of stripes are used.

Past and recent earthquakes showed the occurrence of Out-Of-Plane (OOP) failures of Unreinforced Masonry (URM) infills in Reinforced Concrete (RC) frames. Such a type of failure, which is promoted by In-Plane (IP) damage (IP/OOP interaction), is dangerous for human life safety and its effects can be associated with the attainment of the Life Safety limit state. In this work, the seismic capacity of Reinforced Concrete buildings at the first OOP collapse is evaluated with a linear analysis based on code provisions and with a procedure based on nonlinear static analysis. More specifically, 16 buildings designed to Eurocodes, different for number of storeys and design Peak Ground Acceleration (PGA), are infilled by two infill layouts different for thickness and masonry properties. For these buildings, the PGA at which the first OOP infill collapse occurs is evaluated by applying two different approaches. The first is based on linear analysis and consists in the simple application of the demand and capacity models currently provided by the Eurocodes. So, it accounts neither for the effect of the IP/OOP interaction on the OOP capacity nor for the effect of structural non-linearity on the OOP force demand. The second approach is based on nonlinear static analysis and on the application of refined literature formulations accounting for the IP/OOP interaction and for structural non-linearity for the definition of the OOP capacity and force demand. The PGAs at the OOP collapse of infills obtained by applying both approaches are compared to show their significant overestimation if the IP/OOP interaction and structural non-linearity are not considered, i.e., if current code provisions are applied. Considerations concerning the influence of the number of storeys and of the design PGA of buildings on the PGA at the OOP collapse of infills are reported. Frequency distributions of OOP collapses at different storeys and fragility curves relating the probability of OOP collapse to both the PGA acting in the OOP direction and the maximum IDR attained in the IP direction are shown. For all case-study buildings, a range of 42 infill layouts, different for thickness and masonry compressive strength, is considered and, with the application of the more refined, not code-based approach, a “limit state” curve defining the infill height-to-thickness ratio/masonry compressive strength couples for which the OOP safety check of infills can be neglected is reported.

© 2019 Elsevier Ltd Nowadays, longitudinal branch plates are used as structural members in several engineering applications to connect brace members to Circular Hollow Section (CHS) chord members, which are widely employed due to their aesthetical appeal and efficiency. At ultimate limit state, the failure mechanism of T-type branch plate-to-CHS connections is characterized mainly by the formation of yield lines in the chord. This paper presents an analytical methodology developed using the yield line approach to predict the compressive strength of the longitudinal T-type branch connections. A numerical finite element parametric model was developed and calibrated with experimental work from literature to accurately assess the joint capacity in different configurations. Results obtained from the proposed analytical model show very good agreement with the calibrated FE model. Moreover, a comparison between the results of the parametric FE analysis with both previous studies and current design guidelines is presented. The proposed analytical model takes into consideration the most influential geometrical parameters and the effect of membrane stresses, which was found to be significant in slender chord members. The newly proposed equation also considers the slenderness of chord members which is not considered in the current design equations. ispartof: THIN-WALLED STRUCTURES vol:141 pages:73-84 status: published

The knowledge of soil-geosynthetic interface behaviour is a key point in the design of geosynthetic-reinforced soil structures. The pullout ultimate limit state can be reproduced conveniently by means of pullout tests performed with large-size laboratory apparatuses, which allow studying the interaction mechanisms that develop in the anchorage zone. During the service life of geosynthetic-reinforced soil structures, reinforcements may be subjected to long-term cyclic vehicular loads or short-term seismic loads in addition to dead loadings, such as the structure's self-weight and other sustained loads. In order to study the influence of a cyclic loading history (a sinusoidal function with fixed amplitude A, number of cycles N and frequency f) on the post-cyclic peak pullout resistance, the writers carried out a series of multi-stage pullout tests on a high density polyethylene extruded uniaxial geogrid embedded in a compacted granular soil for different vertical effective stress σ′v values. Moreover, the stability of the soil-geosynthetic interface from a point of view linked to the cyclic loading application has also been investigated. Test results showed that the design pullout resistance parameters are affected by the applied cyclic loading history for specific combined conditions (A, N and σ′v) and it should be taken into account for designing geosynthetic reinforced soil structures.

Structural or foundation rocking are effective ways to prevent the development of large force demands in building systems experiencing ground shaking. In practice, structural rocking may result in large displacements and therefore is often accompanied with dampers, while residual and differential settlements are sometimes a barrier for utilisation of foundation rocking. This paper presents a novel approach to test simultaneously in a centrifuge the performances of a building model rocking above its foundation level (structural rocking) and of a dynamically equivalent building rocking below its foundation level (foundation rocking). These tests are used to explore the role of the foundation and soil response when considering the relative trade-offs between the two building types. In the experiments, dry sand was used in both dense and loose states and a series of earthquake excitations were applied. Results demonstrate that the rocking motion of the buildings is evident in the soil response beneath the structures, and foundation rocking causes larger dynamic differential settlements than structural rocking for a given rocking amplitude. However, these differential settlements may still be small enough to be tolerated from a serviceability limit state point of view.

This paper explores the concept of the optimum span to depth ratio of reusable composite beams with demountable bolted shear connectors so that the beams may be designed most efficiently in terms of their weight and the shear connector distribution along the span. Three patterns of shear connectors were evaluated by a simple pseudo-plastic model and calibrated by finite element modules in terms of their effect on the overall composite beam stiffness in the range of 9 to 15 m span. The optimum span to depth ratio of symmetrical and asymmetrical beams was determined and compared to equivalent beams with welded shear connectors. It was found that the optimum span to depth ratio of uniformly loaded unpropped composite beams with demountable bolted shear connectors may be taken as 22 which allows for a utilisation factor of 0.7 at the ultimate limit state to ensure that plasticity does not occur in the first use cycle. It was found that the effect of asymmetry on the optimum span to depth ratio is small. For propped beams with demountable shear connectors, the optimum span to depth ratio may be increased to 24.

Probability-based limit state design is a hallmark of modern civil engineering practice. Code requirements to meet both ultimate limit states (ULS) and serviceability limit states (SLS) have vastly improved the safety and usefulness of concrete structures. To meet increasing challenges of triple bottom line sustainability (covering social, environmental and economic aspects), a new class of design limit states are needed within code-based engineering design practice. A framework for sustainable design and management considering environmental impacts was earlier developed, and a multi-physics and multi-scale deterioration model for reinforced concrete affected by chloride-induced corrosion was established. A simplified case study is presented in which a reinforced concrete panel is exposed to a marine environment. The multi-physics deterioration model is used to determine the time until an engineering limit state (cracking due to reinforcement corrosion) is reached, and a design and maintenance optimization is performed with regard to sustainability (global warming potential footprint).