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Seismic responses of utility tunnel-soil system were studied via shaking table model tests with considerations of two kinds of double box utility tunnels: with and without joint connections. These two testing utility tunnel models were made of galvanized iron wire and micro-concrete, and the ground was simulated by the dry standard sand through layered tamping treatment. The utility tunnel-soil system was subjected to horizontal vibration in uniaxial direction perpendicular to the longitudinal direction of tunnel model. Via instrumentations of earth pressure gauges, accelerometers and strain gauges, the earth pressure response, acceleration response and bending moment response were measured. The testing results show that the joint connections in the utility tunnel along the longitudinal direction play an important role in determining the characteristic of earth pressure response and bending moment response, whereas the effect of joint connections on acceleration response is less significant. In addition, the partition wall exhibits the consistent acceleration response with the side-wall of double box utility tunnel model under seismic condition. Based on the testing results, it is suggested that the joint connection should be taken reasonably into consideration during design and construction for engineering practice.

Buried pipelines are commonly damaged when laid across strike-slip faults, always leading to some level of destruction with fault movement. The moment of the neutral axis of a pipe section was obtained by integration, and the equations for the bending moment and the bending strain on a pipeline’s section were presented here, based on a trilinear stress–strain model. The calculation method for the lateral soil pressure and pipeline’s bending strain near the fault-crossing point was improved. Lateral soil pressure was regarded as being related to lateral pipeline movement and, for accurate calculation, this part of the pipeline was divided into finite element segments. An iterative process for solving for pipe bending strain was derived, and the algorithm and program for calculating bending strain and the potential damage position of the pipeline’s sections was compiled based on Matlab software. Compared with finite element method (FEM) results and the current standard method, in the situation of a pipeline being in tension under the action of a strike-slip fault (intersection angle

The landslides have an important influence on the force and deformation of existing tunnels, which may adversely affect the liner structures and even endanger normal operation. Current scholars have made few efforts to investigate the reinforcement measures for existing tunnels in the landslide region, and even paid less attention to probe into the pile-anchor strengthening mechanics. A new kind of pile-anchor strengthening system for existing tunnels has been proposed in this paper considering the influences of deforming landslides, in which the anti-slide pile, the anchor cable and the tunnel lining were integrated as one force whole. In order to observe the pile-anchor strengthening mechanics, three physical model tests for comparative analyses were established in case of the tunnel axis parallel to the sliding direction of landslide, including the conditions without reinforcements, only with anti-slide pile and full with the pile-anchor strengthening system. Specially for the pile-anchor strengthening model tests, the extra experimental evaluation for the interaction mechanics between existing tunnel and landslide was added, such as, the tunnel diameter of 40 and 50 mm and the pile-anchor of three and six pairs. In addition, three-dimensional numerical models were implemented to analyze the landslide deformation and the internal force of tunnels after installing the pile-anchor strengthening system. Comparing with non-reinforcement, the bending moment of tunnel and contact stress at interface between tunnel and landslide at the position of 200 m away from tunnel entrance with six pairs pile-anchor reinforcement dropped by 97.2% and 50%. The results show that the deformation of landslide, the bending moment of existing tunnel and the contact stress at the interface between tunnel and landslide pronouncedly diminish after taking the pile-anchor strengthening measures. The new combined pile-anchor system has higher bearing capacity and stability, which can further improve the operation safety of existing tunnels in landslide region.

Excessive structural forces generated inside tunnel linings could affect the safety and serviceability of tunnels, emphasizing the need to accurately predict the forces acting on tunnel linings during the preliminary design phase. In this study, an anisotropic soil model developed by Norwegian Geotechnical Institute (NGI) based on the Active-Direct shear-Passive concept (NGI-ADP model) was adopted to conduct finite element (FE) analyses. A total of 682 cases were modeled to analyze the effects of five key parameters on twin-tunnel structural forces; these parameters included twin-tunnel arrangements and subsurface soil properties: burial depth H, tunnel center-to-center distance D, soil strength s u A , stiffness ratio G u / s u A , and degree of anisotropy s u P / s u A . The significant factors contributing to the bending moment and thrust force of the linings were the tunnel distance and overlying soil depth, respectively. The degree of anisotropy of the surrounding soil was found to be extremely important in simulating the twin-tunnel construction, and severe design errors could be made if the soil anisotropy is ignored. A cutting-edge application of machine learning in the construction of twin tunnels is presented; multivariate adaptive regression splines and decision tree regressor methods are developed to predict the maximum bending moment within the first tunnel’s linings based on the constructed FE cases. The developed prediction model can enable engineers to estimate the structural response of twin tunnels more accurately in order to meet the specific target reliability indices of projects.

In this study, a refined numerical model for segmental lining of a shield tunnel, which contains detailed models of reinforcement and connecting bolts, is established using finite element software. The model is first validated by the results from a full-scale model test. Then, based on the load-structure method, this numerical model is adopted to investigate the internal force distribution and the transverse deformation characteristics of the shield tunnel when it is subject to local soil loosening. The influence of loosening position, loosening range, and loosening extent on the mechanical response is extensively studied through comprehensive numerical analyses. The results show that the main influence of local soil loosening on the ring is to disturb the force balance and change the constraint conditions, thus changing the deformation pattern and force state. After the loosening occurs, the bending moment of the ring in the loosening range increases and the axial force decreases. The vertical convergence of the ring is the largest and the equivalent stiffness of the ring is the smallest when the local soil loosened at the haunch and the loosening range α is 90°. The vertical convergence of the ring increases with increasing of the loosening extent, and the equivalent stiffness decreases linearly with increasing of the loosening extent. The results can enhance our understanding of mechanical behaviors of segmental lining associated soil loosening, and will show a possible way for detecting soil loosening based on the measured deformation and internal forces.

The box girder can be seen as a kind of simplified ship structure that can withstand a vertical bending moment. Dynamic loads play an important role in structural safety analysis, such as ship bow slamming during harsh sea conditions. In this paper, the dynamic elastic–plastic response and ultimate strength of a box girder under a bending moment are analyzed. A box girder with the same cross-section scantlings and span length as the Nishihara experiment is selected as the analysis object. Based on the model experiment results, the non-linear FE analysis method is validated to capture the ultimate strength of a box girder under bending moment. Then, six box girders were designed to study the critical influence factors on the dynamic ultimate moment, including the model length, plate thickness, mass density and load excitation period. On the basis of structural dynamic response, an evaluation criterion of dynamic limit state for the box girder under a bending moment is proposed in this paper. Compared with the static ultimate moment, the change in the dynamic ultimate moment is discussed in detail to obtain the general principal method for dynamic strength analysis. The conclusions in this paper can provide guidance for dynamic ultimate strength evaluation.

Coupled walls with replaceable steel shear link coupling beams are used to minimize the repair cost and downtime of buildings after major earthquakes. In this study, the direct displacement-based design (DDBD) method for coupled walls with steel shear link coupling beams using inelastic displacement spectra is developed. For capacity design, a continuum model of the coupled walls that accounts for the stiffness degradation due to expected damage in the first mode is adopted, to obtain equations to estimate the shear forces and bending moments generated due to higher modes. The effectiveness of the DDBD design method for coupled walls with steel shear link coupling beams is assessed by comparing the drift demands with nonlinear response history analysis (NLRHA) results and for capacity design purposes the shear force and bending moment profiles obtained from NLRHA are compared with the results obtained from the equations derived in this study and the weighted capacity design (WCD) method. The results obtained for 5-, 10-, and 15-story coupled walls with steel shear link coupling beams, show that the proposed design methodology is suitable to achieve the design objectives.

Structures on incline ground are vulnerable to earthquakes because of irregularities in plan and elevation. The structural configurations on slopes have been observed, with stepback and stepback-setback configurations being the most common. In mid to high rise buildings, shear wall and C-shaped shear wall cores are commonly used lateral load resisting components. The current research focuses on comparing the seismic performance of L-shear walls(LSW) at the corners, C shear-walls at core(CSW) and Reinforced concrete-filled steel tube column (RCFST) at corners and cores in stepback, and stepback-setback configurations buildings considering the base of the structures fixed designed for Indian codes using response spectrum analysis. The structural analysis tool ETABS 2017 was used to perform seismic analysis. Buildings on a hill slope with various configurations are studied: bare frame, concrete blockwork infill, LSW full bay at corners, LSW half bay at corners, CSW and RCFST column at corners and core. The characteristic parameters such as base shear, forces in the columns at the ground floor, storey drift, maximum storey displacement, time period, the bending moment in columns at every floor level and storey shear in structures will be determined and analysed for the different structures at the sloping ground. Structures with corner LSW perform better than buildings with centrally located shear walls at the core, whereas LSW at half bay in the corner and RCFST columns at corners and core serve the dual objective of space constraint and improved performance.

Many riveted joints bear the action of out-of-plane bending moments in steel truss bridges. The fatigue resistance of these joints isn’t stipulated in the current design criteria. Ensuring the safety of structures necessitates analysing the fatigue process of such riveted joints. This paper attempts to evaluate the fatigue life of riveted lap joints from the perspective of engineering applications. The study first found through fatigue tests with two types of fatigue details in riveted lap joints: plate surface cracking and rivet hole edge cracking. Then, the fatigue progression is divided into three stages: the microstructure short crack (MSC) stage, the physical short crack (PSC) stage and the long crack stage. The crack propagation model in the short crack stage is established by combining a scanning electron microscope test of the material and an empirical formula. The crack propagation model of the long crack stage is established by the crack propagation test and considering the crack closure effect. Results show that the fatigue life corresponding to the hole edge crack fatigue detail category is shorter than that to the plate surface crack. In each crack propagation stage, the crack propagation life decreases with increasing load and decreasing load ratio RL. For the two fatigue detail categories, the proportion of the long crack stage to the whole fatigue life is small, and the effect of the crack closure on the overall fatigue life is limited; therefore the effect of the load ratio RL on the fatigue life can be ignored.

In the present study, the flexural behavior of concrete-filled steel tube (CFST) beams strengthened by welding round steel at the soffit of the beam has been investigated. First, a total of six specimens were tested under four-point bending load, which includes one reference beam and five retrofitted beams strengthened by welding round steel of different diameters at the soffit of the beams. Then, the corresponding nonlinear finite-element models have been developed and calibrated against the experimental results. By combining indoor experiments and numerical simulations, the bending moment versus mid-span curvature curves, the flexural capacities, flexural stiffness, ductility, vertical deflection curves, strain distribution across the cross-section, and neutral axis offset of the test beams have been systematically analyzed. The results show that the welded round steel at the soffit can improve the flexural bearing capacity and stiffness of the CFST beams significantly. This can be attributed to the CFST beams benefitting from the flexural bearing effect of the round steel and the downward offset of the neutral axis which causes more core concrete to be in compression. Further, the larger the diameter of the round steel, the greater the benefit. Finally, comparisons have been made with the flexural stiffness calculated using the existing design codes, such as AIJ standard, BS5400, Eurocode 4 and AISC specification. The comparisons show that the flexural stiffness of the unstrengthened CFST beam can be predicted by AIJ and BS5400 perfectly, whereas those of the strengthened CFST beams can only be accurately calculated by AISC.

This paper proposes the use of a novel modular joint to overcome the shortcomings of existing aluminium alloy gusset joints. Bearing capacity tests are performed on the bearing capacity of four sets of joints in the early stage, and the force characteristics and failure mechanism of the novel modular joint are summarized. On this basis, this study conducts theoretical research on the design method of this new type of joint. According to the four failure modes that occurred in the experiment, namely, the bending failure of the aluminium alloy beam, the shear failure of the bolt group, the tensile and shear failure of the modular unit, and the local buckling failure of the unit bottom plate, a formula for calculating the ultimate bearing capacity of each component is provided. According to the working mechanism of modular joints, theoretical formulas for the ultimate flexural bearing capacity and initial stiffness of the joints are derived according to the three-part bending moments produced by each component. Based on a power function model, a prediction formula is fitted to the bending moment-rotation curve of the new joint and compared with the measured values of the joint and 22 numerical models. The results show that the average errors of the two sets of theoretical formulas are only 2.85% and 4.5%, fully verifying their validity and reliability. The results provide a theoretical basis for the engineering design and application of this type of joint.

Welded hollow spherical joints (WHSJs) are commonly used joints in reticulated shell structures. The WHSJs in actual projects are always subjected to tension force and moment. The appearance of tension force (TF) may affect the probability distribution of moment capacity for WHSJs with random corrosion. The stochastic FE analyses are conducted in this study to investigate the influence of TF on the probabilistic distribution of bending capacity of WHSJs. This study aims to investigate the influence of TF on bending capacity and construct a probabilistic distribution model of bending capacity considering the influence of TF. The proposed method for predicting probability distribution of reduction factor is also validated. Results show that the method has high accuracy in predicting the probabilistic distribution of bending capacity of WHSJs in complex force state. In addition, the proposed method is convenient for actual applications.

Partially encased composite (PEC) columns are efficient structural elements that offer ease and agility for prefabrication, requiring no molds for casting concrete. The manufacture of these elements involves anchoring the reinforcement to the metallic profile, which is a laborious process. Thus, alternative solutions capable of maintaining the column performance can propel PEC columns, providing more practical construction technics. One of these alternatives is substituting steel rebar with Fiber Reinforced Concrete (FRC), saving time. The benefits of such solutions were already proven with laboratory experiments. Therefore, this study aims to numerically analyze the structural behavior of PEC columns under different load conditions from available experiments based on a calibrated numerical model. The performance of the models was compared using two reinforcement configurations: conventional reinforcement and steel fiber reinforced concrete. Several cases of eccentric axial loads were evaluated, presenting the influence of the eccentricity and the skew angle relative to the major axis of inertia. Finally, simulations were carried out on columns subjected to non-uniform moments along with their height. The models showed a more abrupt rupture when bending around the minor axis of inertia when subjected to a constant moment on the length. Regarding non-uniform moments, the critical situation in all cases investigated occurs when the moment is constant along with the height. Results were favorable to FRC use because the two reinforcement configurations evaluated showed similar behavior in all the conducted analyses; the model of FRC showed higher ductility than the model with conventional reinforcement, mainly due to the confinement provided by fibers. Nevertheless, columns with FRC presented more significant lateral displacements, resulting in slightly lower maximum loads than those shown by columns with conventional reinforcement.

Pretensioned spun high-strength concrete (PHC) piles have been widely used in building foundations in many parts of the world. However, PHC piles are also known to have poor lateral deformation and ductility capacity and hence are not suitable for seismic regions. To improve the horizontal load bearing and deformation capacities, pretensioned centrifugal spun concrete piles with steel strands alone (hereafter referred to as PSC piles) or a combination of steel strands and mild steel deformed rebars (referred to as PSRC piles) have been developed. PSRC piles are expected to benefit on the one hand from steel strands with high deformation capacity, and on the other hand from deformed steel bars with good bond with concrete and hence better control of cracks. This paper presents a comprehensive study on the comparative flexural performance of PSC and PSRC piles. The bending tests of PSC piles and PSRC piles were firstly conducted on six full-scale pile specimens with three different pile diameters, respectively. The flexural performances are evaluated in terms of crack resistance, flexural and deformation capacities, as well as crack distribution. The results show that the cracking bending moment of PSRC piles is similar to that of PSC piles, but the ultimate bending moment is about 55% higher due to the addition of deformed rebars. The general cracking behavior of PSRC piles exhibit remarkable improvement comparing to PSC piles, with an extended crack region, denser distribution of cracks, and much reduced maximum crack width. Following the experimental study, a theoretical method is proposed for the calculation of the flexural strength and flexural stiffness of prestressed concrete piles considering the presence of both steel strands and deformed rebars. Furthermore, a finite element (FE) model has been developed to simulate the flexural performance of the piles. The accuracy of the FE model is validated through comparing with the experimental results, and subsequently parametric analyses are conducted to explore the influences of three parameters, including the prestressing level of the prestressing strands, prestressing strand ratio and deformed steel bar ratio, on the flexural performance of PSRC piles.

This paper assesses a number of direct strength methods (DSM) for thin-walled steel members under combined major axis bending and compression. These methods consist of two ways of calculating the compression – bending moment (P-M) interaction surface (plastic or first yield) of the cross-section, and the following three methods of operating on the P-M surface: using a compound value of the surface; converting a beam-column to an equivalent beam; and converting a beam-column to an equivalent column. The aim of this research is to identify the most consistently accurate and easy to implement DSM equations to calculate the resistance of thin-walled steel beam-column members, by comparison against numerical simulation results, obtained using a validated ABAQUS model. The numerical simulations investigated the effects of changing different design parameters to ensure a sufficient dataset for each failure mode, including section size, member length, flange restraint, load eccentricity and yield strength. Based on an evaluation of the mean and standard deviation of ratios of the calculated resistances to ABAQUS simulation results, it has been found that for global buckling, any of the methods can produce accurate results. For local buckling, the standard deviation values for all the methods are similar, about 0.05. However, when judging the mean values, the best methods are the equivalent beam method using plastic P-M surface, with a mean value of 0.995. For distortional buckling, upon modification of the existing DSM equations for pure bending using the plastic P-M surface, the equivalent beam method gave an average of 0.998 and a standard deviation of 0.102. Overall, the equivalent beam method using the plastic P-M surface is the most consistently accurate method.

This paper describes a simple analytical tool for the calculation of the shear strength of r.c. rectangular members with shear reinforcement and subjected to only truss mechanism. The proposed method considers simplified stress fields and evaluates the shear strength of members subjected to axial force, bending moment and shear force by means of the application of the static theorem of limit analysis. Unlike most of the formulations proposed in codes and in other research studies, the proposed method considers a single physical model to explain the resistance to axial force, bending moment and shear force, and simultaneously satisfies the equilibrium under all the above internal forces. The paper identifies basic points of the N-M-V ultimate domain and reports relations and procedures to calculate the values of the internal forces of these points as well as the internal forces of the points in between. The method is applied to a set of beam and column members and a comparison is drawn between the shear strength resulting from the simplified method and that from a more complex non-linear mathematical program proposed in the past by the same author. Finally, to prove the value of the method and define the field of reliable application, the proposed method is applied to members tested in laboratory by other researchers and characterised by different geometric and mechanical properties. The obtained results are also compared with those deriving from other methods present in the literature.

Even though aluminium latticed domes are widely used as roofing structures in case of very large areas, few researchers have focused their attention on the influence of the structural details on the overall structural behaviour and on the development of models to account for such influence in the design process. Conversely, the most significant part of the research efforts is devoted to steel structures. In particular, the semi-rigidity of joint behaviour can play an essential role in the structural response. In this paper, the behaviour of bolted Aluminium Alloy Gusset (AAG) joints under axial force and bending moment is investigated by developing a mechanical model based on the application of the component method which is currently codified for the analysis of steel connections. The experimental tests available in the technical literature have been analysed to gain insight into the actual behaviour of AAG joints. The proposed mechanical model is presented, leading to the evaluation of both the moment-rotation curve and the axial force versus axial displacement curve of AAG joints. Finally, the analytical results obtained from the mechanical model herein proposed have been compared with the experimental results showing the accuracy of the component method also for the modelling of non-conventional connections such as those used in the case of aluminium alloy latticed domes.

Reinforced concrete (RC) slabs of highway bridge decks are gradually deteriorated due to the traffic vehicle wheel-loading. Fatigue is one of a number of possible causes for the deterioration. Cantilever RC slabs of the bridge are also damaged by fatigue loading. To increase the fatigue durability of the bridge deck slab, the near-surface mounted (NSM) technique is used with carbon fiber reinforced polymer (CFRP) rods embedded in the RC slab as an effective strengthening method. This study presents the fatigue characteristics of cantilever RC slabs strengthened with CFRP rods with a high-modulus of elasticity. A cantilever RC slab specimen with embedded CFRP rods with high moduli was constructed on a moving-wheel load testing machine and tested for approximately 11 months. The slab had a minimum thickness of 160 mm (as stipulated by the Japanese design code), and the minimum number of steel reinforcements was embedded to ensure (negative) flexural failure of the RC slab where CFRP rods were not used. During the test, the CFRP strengthened slab specimen was subjected to a negative bending moment from repeated moving-wheel loads. Very limited experimental data are available for the evaluation of the structural behavior of cantilever bridge decks subjected to wheel loads. Therefore, the moving-wheel fatigue experiment of the cantilever RC slab with NSM CFRP rods would be useful information for strengthening. The moving-wheel loading test confirmed the increase in fatigue durability of the CFRP strengthened slab as the slab specimen endured approximately 3.56 million equivalent-cycles at an initial load of 60 kN, which was 32% higher than the designed service load. The experimental investigation revealed that the ultimate failure of the cantilever slab was punching shear failure attributed to the rupture of the CFRP rods.

In this paper, the nonlinear bending behavior of functionally graded porous (FGP) plates under uniformly distributed transverse loads is studied based on the neutral surface concept within the framework of first-order shear deformation theory (FSDT) including geometrical nonlinearity. The FGP materials with three porosity distribution patterns namely uniform, non-uniform symmetric and non-uniform asymmetric are considered. Using the stress function and Galerkin method, the analytical solutions are obtained to examine the load vs deflection and load vs bending moment curves for various edges boundary conditions. The present results are compared with reference solutions to show the accuracy and the effectiveness of the proposed approach. The effects of the geometric, material parameters, elastic foundations and in-plane constraints on the nonlinear bending behavior of FGP plates are studied in detail through numerical investigations.

The deployable bridge based on scissor structures is one of the effective methods to quickly restore traffic after natural and man-made disasters. Scissor structures have the advantages of high storage rate, lightweight, and convenient storage and transportation. However, when scissor structures are used as load-bearing structures, their stiffness and bearing capacity are low. In this study, a three-dimensional deployable bridge based on the cable-strengthened scissor structures was proposed. In addition to rapid expansion, steel cables were used to strengthen scissor structures to improve the stiffness and bearing capacity. Besides, the static loading comparative tests on cable-strengthened scissor structures and traditional scissor structures (cable-free scissor structures) were performed. The results show that the stiffness of the cable-free scissor structure is small, the bending moment of members is large, and the stress distribution is uneven. The stiffness of cable-strengthened scissor structure is significantly improved; the bending moment of members is significantly reduced; and the stress distribution in the member section is more uniform. It is proved that cables can be used to improve the stiffness and load-bearing capacity of scissor structures without affecting the deployability.

The core objectives of sustainable development are to develop access to renewable, sustainable, reliable, and cost-effective resources. Wind is an essential source of renewable energy, and monopile wind turbines are one method proposed for harnessing wind power. Offshore wind turbines can be vulnerable to earthquakes and liquefaction. This numerical study defined the effects of wind turbine weight on the seismic response of a wind turbine-monopile system located in liquefied multilayered soil with layer thicknesses of 5, 10, 15, and 20 m using four far-field records. OpenSees PL analysis indicated that if the liquefied sand had a lower density or a thickness of more than 10 m, then an increase in the earthquake acceleration beyond 0.4 g caused the pile to float like liquefied soil and to lose its vertical bearing capacity. Moreover, increasing the wind turbine power from 2 to 5 kW had no significant effect on the soil-structure interaction response. As the earthquake acceleration increased, the bending moment of the pile-column also increased as long as liquefaction did not occur and the pile-column deformation remained rotational-spatial in shape. As the acceleration and liquefaction increased and the pile began to float in response to its transverse motion, there was no significant difference in the pile-column displacement along the length, but there was a decrease in the pile-column bending moments. As this phenomenon increased and the pile continued to float, transformation of the pile increased the difference between the displacement of the pile-column along its length and further increased the bending moments. These results were derived from multiple correlation analysis, the bending moment relations, and lateral displacement of the pile-column of the wind turbine.

This paper studies the application of the inerter-based passive structural control in seismic response mitigation for a wind turbine. The inerter-based passive control system used here is called inerter-based dynamic vibration absorber (IDVA), in which a spring and an inerter-based mechanical network are connected in parallel. A multi-degree-of-freedom (MDOF) system is used to describe the wind turbine system with the consideration of the interaction between wind turbine structure and soil. For the purpose of mitigating seismic response, the inerter-based mechanical network is regarded as a controller to be designed using two different methods. Then, a variety of different network configurations are selected in the fixed-structure method, and only the low-order admittances are taken into account in the network synthesis method. By optimizing the controller parameters with $$H_{2}$$ optimization method, response parameters such as tower-top displacement are improved. The comparisons of the tower-top displacement performance corresponding to the traditional tuned mass damper (TMD) and the inerter-based dynamic vibration absorbers (IDVAs) show that the inerter-based control can use a smaller additional mass ratio to achieve the same tower-top displacement performance as the TMD control. Finally, the numerical simulation results obtained with different types of ground motions for a 5-MW NREL wind turbine also demonstrate the superiority of IDVAs compared to TMD, and a similar decreasing trend is observed for tower-top displacement performance and tower bottom bending moment performance.

To study the dynamic response of vertical and batter pile groups in saturated sand, dynamic tests of these pile groups in saturated sand were carried out using the ZJU400 geotechnical centrifuge at Zhejiang University. The following results were obtained. (1) As the motion intensity increased, the peak acceleration in soil layers at different depths significantly decreased, indicating that the soil stiffness was significantly reduced. (2) During the motion process, the instantaneous bending moment of the vertical and batter pile groups at different depths changed continuously, which had a strong relationship with the saturated sand liquefaction. In the process of sand liquefaction, the residual bending moment generated by the batter pile was more obvious than that of the vertical pile. (3) With the liquefaction of the saturated sand, the distribution of the maximum bending moment of the vertical pile group changed, and the bending moment near the pile cap of the vertical and batter pile groups was always large. (4) In certain cases, the horizontal acceleration and dynamic displacement of the vertical pile cap were amplified. When the motion intensity was large, residual displacement of the batter pile cap occurred.

This study investigates the flow dynamics of a dry granular flow and force interaction with a rigid wall using the material point method (MPM). The model equations and solution scheme of the MPM are presented, and the inscribed Drucker–Prager model is adopted in the constitutive model of the MPM. An analytical solution to the classical dam-break problem is used to validate that the MPM can accurately simulate the large deformation problem. Then, the simulation of a channel flow experiment of a dry granular flow impacting a rigid wall is conducted. In the simulations, a bottom friction algorithm is presented based on the MPM. The simulation results of the normal force and bending moment of the rigid wall are consistent with the experimental results, which validated the correctness and effectiveness of the simulations. The internal velocity distribution of the granular flow at a critical time, the motion path of the key points, the influence of the bottom friction angle on the total normal force of the rigid wall, and the velocity and kinetic energy of the granular flow are analysed and discussed. Through the analysis of the granular flow position, the velocity vector of the internal point, and the force vector of the rigid wall at several key moments in the process of the granular flow impacting the rigid wall, the mechanism of the granular flow impacting a rigid wall is summarized. It can provide a scientific reference and basis for the prevention and control of the granular flow disaster and the design of a retaining wall.

Purpose The purpose of this paper is to quantify the combined effect of shape distortion and bend angle on the collapse loads of pipe bends exposed to internal pressure and in-plane closing bending moment. Non-linear finite element analysis with large displacement theory was performed considering the pipe bend material to be elastic perfectly plastic. Design/methodology/approach One half of the pipe bend model was built in ABAQUS. Shape distortion, namely, ovality (Co) and thinning (Ct), were each varied from 0% to 20% in steps of 5% and bend angle was varied from 30° to 180° in steps of 30°. Findings The findings show that ovality has a significant impact on collapse load. The effect of ovality decreases with an increase in bend angle for small thickness. The opposite effect was observed for large thickness pipe bends. The influence of ovality was more for higher bend angles. Ovality impact was almost negligible at certain internal pressure denoted as nullifying point (NP). The latter increased with an increase in pipe bend thickness and decreased with increase in pipe bend radius. For small bend angles one NP was observed where ovality impact is negligible and beyond this point the ovality effect increased. Two NPs were observed for large bend angles and ovality effect was maximum between the two NPs. Thinning yielded a minimal effect on collapse load except for small bend angles and bend radii. The influence of internal pressure on thinning was also negligible. Originality/value Influence of shape distortions and bend angle on collapse load of pipe bend exposed to internal pressure and in-plane closing bending has been not revealed in existing literature.

To improve the stress state of traditional antislide pile and utilize the stable soil on both sides of a landslide and slope foot, a spatial arc antislide pile supporting structure was proposed. Based on numerical calculation, a parametric study was conducted to assess the influence of the rise-span ratio on the stress state of the supporting structure, the displacement of the pile top, and the earth pressure in the front of the pile. The optimal rise-span ratio was 3-16 according to the numerical simulation results. An indoor model test at the optimal rise-span ratio was carried out, recording the pile strain and the earth pressure in front of the pile. The results showed that some indices increased with the increase in rise-span ratio, such as the load transferred to the pile at the arch foot, the bending moment of the piles, the displacement of the pile top, and the earth pressure; within a certain depth near the pile top, the soil in front of the pile is loose during the loading processes, and the earth pressure at the range was zero. The overall safety factors of the four supporting models were 2.42, 2.66, 2.78, and 2.84, respectively, which can satisfy the requirements for practical engineering. The test results verify the feasibility and rationality of the spatial arc antislide pile supporting structure, which can provide a new idea for landslide treatment.

Taking the occurrence conditions of the hard main roof in the deep 13-1 coal mining roadway in Huainan mining area as the research object, based on the mechanical parameters of the surrounding rock and the stress state of the main roof obtained by numerical simulation, a simply supported beam calculation model was established based on the damage factor D, main roof support reaction RA, RB, and critical range C (9 m) and B (7 m) at the elastoplastic junction of the solid coal side and mining face side (hereinafter referred to as “junction”). Considering that the damage area still has a large bearing capacity, the vertical stress of the main roof at the junction is K1γH (0.05γh, 0.15γh, and 0.25γh) and K2γH (0.01γh, 0.10γh, and 0.2γh). The maximum deflection is 21 mm, 324 mm, and 627.6 mm, respectively. According to the criterion of tensile failure, the maximum bending moment of the top beam is 209 mN·m at the side of the working face 3.1 m away from the roadway side when K1 = 0.15 and K2 = 0.10, and the whole hard main roof is in tensile failure except the junction. To control the stability of the top beam and simplify the supporting reaction to limit the deformation of the slope angle, RC and RD are used to construct the statically indeterminate beam. By adding an anchor cable and advance self-moving support to the roadway side angle, the problem of difficult control of the surrounding rock with a large deformation of the side angle roof is solved, which provides a reference for roof control under similar conditions.

Resilience in bridges is of paramount importance as bridges are important transport assets that maintain mobility after disasters. The most common cause of extreme stress development on structures and especially bridges is dynamic loads due to floods, earthquakes, strong winds, truck and ship collisions. In the international literature, there an ongoing research in support of adaptable and low-damage bridge connections for bridges and structures exposed to dynamic loads. This paper focuses on the design and assessment of a novel connection based on extensive numerical modelling of a 3D Finite Element (FE) model of the connections developed in Abaqus. The connection, which is essentially a resilient hinge, connects the foundation with the bridge pier and the latter with the deck, which are the positions where typically RC hinges are formed during extreme dynamic loads, e.g. earthquakes. A similar connection was designed before, however, this paper offers a design methodology and advances the connection by providing improvements to its mechanical characteristics, i.e. the geometry, resolving issues with regard to stress concentration by improving the contact surface geometry, the consideration of the friction and the optimization of its components. The paper concludes with a discussion on the connection constructability, therefore enabling further applications of the proposed design. The results also demonstrate that even though the rebars of the hinge undergo excessive elongation, the connection maintains a significant bending moment capacity, therefore not hindering the integrity of the bridge. Moreover, it is observed that the compressive zone of the hinge remains intact, thanks to the high strength of the steel, therefore no shortening of the RC column is expected.

To evaluate the seismic responses of bundled conductor interconnected electrical equipment, a model of the interconnected system was established. The bundled conductor model was incorporated into the interconnected model, and the electrical equipment was simplified as a 5-degrees of freedom structure. The bending stiffness of the sub-conductor and the constraint effects of the spacer, usually omitted in previous research, are considered in the paper. The iteration method was used to obtain the terminal forces and moments of the bundled conductor. Then, the model was validated by shaking table tests. We investigated the effects of the slackness and bending stiffness of the bundled conductor on the seismic responses of the interconnected system. Considering the bending stiffness of the sub-conductor and the effects of the spacer, the seismic response characteristics of the interconnected electrical equipment were much different from those connected by a flexible conductor without bending stiffness in previous research. Not only the terminal forces, but also the terminal bending moment should also be considered in the seismic performance evaluation of interconnected electrical equipment.

Gradual changes of weight and geometry of vehicles combined with traffic values sometimes leads to old existing bridges having to be strengthened and retrofitted. The optimal solution to follow is based on the resistance capacity reserves of each structure, on the existing traffic level at the moment of retrofitting works and on the estimated future traffic. Almost all existing road bridges in Romania were designed according to national provisions/standards. Starting with 2010, following the European Community’s decision, the projects should be designed according to the Eurocodes and the existing bridges, must also comply with the new European load models. The process of checking existing bridges for the action of load models described in Eurocodes is a complicated task. However, the process for the evaluation of the bearing capacity reserves can be significantly simplified using a probabilistic approach. The approach presented in this paper is based on the effects, in terms of bending moments and vertical displacements, produced by several types of vehicles on the bridge superstructure. For presenting the use of this proposed methodology, typical bridge superstructures with precast concrete girders of different lengths were analyzed. The proposed methodology allows to establish the “vulnerability” of existing bridges on live loads.

Rehabilitating the deteriorated deck of post-tensioned concrete box-girder bridges by ultra-high-performance concrete (UHPC) overlay is studied in this paper. Three post-tensioned concrete box-girder bridges in California were selected for the deck overlay analysis. Rehabilitation construction procedures for each bridge were described, including the practical lane closure and traffic re-routing. Detailed finite element models were established incorporating the staged construction modeling of the rehabilitation process, the time-dependent properties for existing concrete and prestressing tendon, and a “double-layer” modeling technique for the simulation of the deck. The time-dependent curves and equations of a specified UHPC were fitted based on experimental data, including creep, shrinkage, and elastic modulus, and this particular mix has been assumed in the FE analysis. How the thickness of the deck layer to be replaced affected the stress distributions in the UHPC overlay and the existing box girder was parametrically studied. Results indicated that stress variations in the existing box-girder were acceptable during the deck rehabilitation construction, but significant tensile stresses were developed in the newly placed UHPC deck overlay. Shrinkage-mitigation measures, such as adding the shrinkage-reducing admixture (SRA), should be considered during the placement of the UHPC overlay to control the shrinkage-induced tensile stress. Steel reinforcement may be adopted in the negative bending moment region to resist the flexural tensile stress by the live loads. The rehabilitation thickness of 3.8–5.1 cm (1.5–2.0 in.) is deemed appropriate for the bridges selected in this study.

This article presents a study to evaluate the structural response of a cable-stayed bridge under a novel system, partially earth-anchored system with crossing cables at the main span. Six side-to-main span ratios, ranging from 0.24 to 0.39 in increments of 0.03, are tested for different bridge response parameters for both the superstructure and substructure. The loads considered in the analysis are the dead load and traffic load. Three-dimensional finite element models of the bridge are developed using structural analysis software SAP2000 and are validated based on the data available in the literature. From this study, it is found that the side-to-main span ratios have a significant effect on girder axial force and anchorage forces while having a very minor effect on cable axial forces. The results also show that the ratio does not affect the bending moment of the main span, but that when a small ratio is considered particular attention needs to be paid to the pier farther from the pylon to avoid uplifting. Deck vibration and longitudinal movement, as well as pylon longitudinal displacement, are not to be an issue for this super-long bridge.

To better understand the characteristics of the seismic response of nuclear power stations with fixed-base and pile-raft foundations, a series of shaking table tests were performed. The shaking table tests included three cases: free-field soil, fixed-base structure without soil, and superstructure with a pile-raft foundation embedded in the soil. One white noise excitation and three earthquake motions with different earthquake intensity were selected as the ground motion to identify the seismic response of the structure, raft, piles, and soils. The effects of earthquake intensity, earthquake frequency, soil-pile-structure interaction, and soil nonlinearity on the system dynamic responses were analysed. The test results show that the natural frequency and the damping ratio of the superstructure for the pile-raft foundation and the fixed-base structure are different, owing to the soil-pile-structure interaction effect. The acceleration amplification ratio of the fixed-base superstructure shows a significantly higher value than that of the superstructure with a pile-raft foundation. The average peak acceleration ratio of the raft for the pile-raft foundation (raft/soil surface) is 1.2. Under the long period wave excitations, the bending moment of the pile is greater than that of short-period wave excitations, and the peak bending moment occurs at the pile head. The vertical and horizontal displacement and residual displacement increases with the earthquake intensity. These observations suggested that the design of nuclear power station with a pile-raft foundation embedded in clay cannot be simplified as a fixed-base structure. Moreover, adopting pile-raft foundation for nuclear power station will extend the choice of finding suitable construction sites for the nuclear power stations, and the test results could provide references for engineers.

The present study proposes a practical yet reliable model for stay cables in cable-stayed bridges considering large force variation under seismic actions. The proposed model is capable of approximating the nonlinear equivalent stress-strain relationship of cables, taking into account the variation of equivalent modulus of cables during the earthquake as well as possible cable loosening. The cable performance based on the proposed method shows an overall good agreement with the actual response of cables. Then, the model is applied to a case cable-stayed bridge under seismic actions and the structural response is compared with the conventional method which models the cables with a constant equivalent modulus derived at dead load state. Comparing to the proposed model, the conventional method fails to accurately describe the cable force at the low stress level and shows discrepancies in time histories of the structural response in terms of amplitude and phase angle. Moreover, conventional method might lead to underestimation of the bending moment at the tower bottom and longitudinal displacement at deck end for most cases, resulting in unconservative seismic design. Such result highlights the importance of applying the proposed model in seismic design of cable-stayed bridges.

Eurocode (EC3) bending moment design model of mono-symmetric corrugated web girders (CWGs) is based on the critical failure mode among the tension flange yielding, the compression flange yielding and the lateral-torsional buckling (LTB) of the compression flange. Recently, LTB behaviour of S460 laterally-unrestrained mono-symmetric CWGs with fully-effective flanges has been investigated by the authors, from which EC3 design model has been modified to better represent their actual strength. Nevertheless, the effect of the local buckling (LB) of slender compression flanges on the flexural strength and behaviour of such long girders has not been examined. While the corrugated web potentially makes large contribution to the out-of-plane stiffness, LB of the compression flange is expected to reduce LTB resistance of such girder significantly. Principally, this paper is devoted to exploring such effect on the accuracy of EC3 bending moment design model. Currently, virtual tests, by using ABAQUS software, are generated based on accurate validation. Then, parametric studies, intentionally designed to eliminate the tension flange yielding, are carried out on simply supported girders considering mainly the influences of the flange and web dimensions on the behaviour of S460 mono-symmetric CWGs. The strengths of such girders are compared with EC3 design model, from which it is found to provide unsuitable predictions. Hence, new formula has been proposed to accord better with the FE results. Additionally, several conclusions are provided at the end to assist design engineers in suggesting efficient cross-sections.

Gusset joints connect only the upper and lower cover plates to the flange of aluminium alloy beams through bolts, and there is no connection to the web. To compensate for this deficiency of gusset joints, a new aluminium alloy flower-gusset composite joint (FGC joint) is proposed in this paper. In this paper, compression, shear and bending tests are performed on new FGC joints. The test results show that (1) compared with those of gusset joints, the compressive stiffness and bearing capacity of FGC joints increase by 2.1 and 1.36 times; (2) the shear capacity and shear stiffness of FGC joints are 1.47 times and 1.74 times higher than those of gusset joints; and (3) the bending capacity of FGC joints is 1.2 times higher than that of gusset joints, but the bending stiffnesses of the two kinds of joints are similar. Then, a numerical model is established to analyse the load transfer mechanism of FGC joints. Numerical analysis shows that the FGC joint passes axial compression through the cover plates and the flower body, shear is transmitted mainly through the flower body, and the bending moment is mainly transferred by the cover plates. Finally, based on the test and numerical analysis, the bearing capacity design method of the new joint is proposed through theoretical analysis.

Stress concentration factors (SCF) in steel tubular joints have gained considerable attention since it is the crucial parameter for fatigue design of steel tubular structures. Meanwhile, among various strengthening methods, Fiber Reinforced Polymer (FRP) wrapping has shown to be an effective scheme for reinforcing steel structures. This study is dedicated to the numerical investigation of SCF values in FRP-strengthened tubular KT-joints under the action of In-Plane Bending (IPB) and Out-of-Plane Bending (OPB) moments on the central as well as outer braces with three various practical loading patterns per each moment. The Finite Element (FE) modeling methodology for joint geometry and FRP generation was validated against the available data in the literature and well-known codes. The effects of different geometrical parameters along with the FRP parameters on the SCF values were studied through post-analyzing a total of 2920 FE models. The numerical parametric studies indicated that FRP strengthening could lower the SCF values in KT-connections by about 30 and 55 percent under IPB and OPB moments, respectively. Using the driven data, practical fatigue design formulas were developed for predicting SCF in FRP-strengthened KT-joints under bending moments, and reliability of the proposed equations was examined using Fatigue Guidance Review Panel recommendations.

The impact of ground motion duration often arises when investigating buildings’ performance in regions susceptible to strong earthquakes, where reinforced concrete (RC) shear walls are typically used as a lateral force-resisting system. Although the seismic performance of these reinforced walls has been improved by the use of self-centering devices and materials, the influence of ground motion duration on self-centering RC walls is not yet well understood. This paper, therefore, examines the effect of ground motion duration on seismic performance and the damage scheme of the self-centering shear wall reinforced with three different types of superelastic shape memory alloy (SE-SMA) in the plastic hinge. A ten-story case study building was analyzed and designed according to the current ASCE 7-16 and ACI-318 practice codes. The maximum inter-story drift ratios (IDR), residual drift ratios (RIDR), shear forces, bending moments, material damages, and collapse margin ratios were examined. The results indicate that IDR and RIDR significantly increased as ground motion duration increased. Meanwhile, the shear forces increased by about 24% on average, which induced only a 6% increase in the bending moments. It was also observed that ground motion duration significantly influenced the scaling factor required to reach the collapse level. Among the examined SE-SMA RC walls, the results indicate that Cu-based SMA RC wall exhibits superior performance in terms of IDR, RIDR, shear forces, and bending moments and performs fairly well in terms of material damage and collapse margin ratio compared to other SMA RC walls. Thus, using Cu-based SMA material in seismically active regions prone to short and long duration ground motions is generally recommended.

The hybrid coupled wall (HCW) system consists of steel coupling beams that connect adjacent reinforced concrete (RC) wall piers. In order to minimize or even eliminate the lengthy design iterations of conventional performance-based seismic design method and directly account for inelastic structural behavior, the modified energy-balance based plastic design (EBPD) method is proposed and developed for the seismic design of HCW systems with the consideration of influences of the degradation of hysteretic behavior and pinching effects. The design base shear can be obtained by solving the modified energy balance equation analytically. Twelve HCW prototype structures with different structural heights and coupling ratio (CR) were designed and evaluated by conducting a series of push-over analyses and nonlinear dynamic time-history analyses with the proved-reliable program of PERFORM-3D. The analysis results indicate that all HCW prototype structures exhibit the favorable yield mechanism and satisfactory seismic performance. Particularly, the influences of CR on the deformation characteristics, bending moment distribution among wall piers and vertical distribution of overturning moment are revealed. Suggestions are made in terms of the appropriate selection of CR for different structural heights.

Even though high-strength steel has been widely used across the world, the global buckling behaviour of high-strength steel beams has yet to be systematically investigated through experimental tests and numerical simulations. This paper describes an experimental and numerical study of the lateral-torsional buckling resistance of welded Q690 steel beams. Eight beams with doubly-symmetric cross-sections and different height-to-width ratios were tested under a concentrated point load. To allow free lateral deflections, a special loading system was designed and erected at the mid-span of steel beams. The applied load remained in the vertical direction during the whole loading process, despite significant rotations and lateral deflections of the beam. The critical bending moment of steel beams was quantified in the experimental tests. Besides, numerical models were established by using ABAQUS and initial imperfections were properly defined in the model. Direct comparisons were made among numerical results of steel beams of different steel grades and design curves in different standards. Based on experimental and numerical results, recommendations were provided for the lateral-torsional buckling design of Q690 steel beams. It was suggested that GB50017-2003 and GB50017-201X can predict the buckling resistance of Q690 steel beams with slightly conservative results, Eurocode 3 yields rather conservative estimations, but ANSI/AISC360-10 significantly overestimates the buckling resistance.

Suspension bridge’s main cable under live load undergoes deformation depending on its gravity stiffness, i.e., work done against gravity under the initial dead load. In three-tower suspension bridges (3TSB), the middle tower's effect on the main cable's gravity stiffness is crucial but hard to assess. In this paper, the 3TSB model was simplified to the 2TSB with elastic constraints. The main cable shape was then calculated via the ratio between the simply supported beam's bending moment and the horizontal force component. The 2TSB model results were used to derive the 3TSB main cable's deflection using the middle tower's stiffness under vertical load. The analytical formula for gravity stiffness of 3TSB was derived by matching the latter with the simply supported beam's deflection formula. For a case-study 3TSB with main spans of 248 m + 1060 m + 1360 m + 380 m, analytical predictions were verified by FEM numerical results obtained via ANSYS. Linear relationships between live load and increments of the main cable's deflection and horizontal force component were derived. Besides, the main cable's deflection under live load can be reduced by increasing its sag-to-span ratio and cross-sectional area.

Software users concerning seismic analysis of buildings usually use the concentrated mass (ML) matrix and the Rayleigh damping matrix (C). Similarly, the initial stiffness matrix (KO) and the first two modes are commonly used to calculate C. In addition, it is commonly believed that damping forces are small so there are no significant errors if the Rayleigh model is used. The evaluation of the accuracy of these practices for the case of steel buildings constitutes the main objective of this research. To this aim the seismic responses of three models, representing steel buildings of low-, mid- and high-rise are considered. If ML is used, shears and bending moments in columns are underestimated by up to 31% and 65%, respectively. If the first two modes are used, shears, drifts, and bending moments in beams are underestimated by up to 27%, 50%, and 55%, respectively, while for axial loads and bending moments in columns the underestimation can be up to 78%. Similarly, damping forces and damping moments are underestimated by up to 350% and 325%, respectively. Damping moments represent a considerable fraction (0.47) of plastic moments in beams. If KO is used in C, axial loads in columns are underestimated by up to 80%. The results of this study give rise to state that the consistent mass matrix should be used in the structural modelling of the structural system under consideration. Similarly, first mode and one superior, and the tangent stiffness matrix should be used to formulate the Rayleigh damping matrix.

This paper investigates the behaviour of two popular structural systems subjected to overheating and column removal cases, which may follow fire incidents. A typical 15–storey steel building is designed with two types of structural system framed-tube and moment-resisting frame. The nonlinear behaviour of these structures under different fire scenarios is investigated using OpenSees Software. The results indicate that deflection of heated beams is insignificant below 400 °C but after that, degrading mechanical properties of steel material leads to large deflection and runaway of heated beams at temperatures below 600 °C. Also, heating the beams of structures initially induces large axial forces in the beams due to restraints on thermal expansion. Thermal expansion of heated floors induces large horizontal displacement and consequently causes additional bending moments in the exterior column. So columns reach their elastic limit at the early stages of fire. Columns of the framed-tube system reach their elastic limit at lower temperatures (130 °C) but fail at higher temperatures (380 °C) compared to columns of the moment-resisting frame system (210 °C). In addition, the lower storey and interior columns are more vulnerable to progressive collapse and fail at lower temperatures (330 °C) due to carrying more gravity loads. In most fire scenarios, beams and columns of framed-tube systems fail at higher temperatures and perform well in the fire than moment-resisting frame systems. In column removal scenarios, mid-span displacement of the heated beam increases significantly, leading to downward movement of upper stories. Also, column removal in the framed-tube system is more destructive than in the moment-resisting frame system. In general, in both structural systems, column removal scenarios, which may follow fire, induce more damage to the structures than general temperature rise in considered fire scenarios.

The shear lag of the box girder section of a wide box bowstring arch bridge was investigated in this study. The finite element analysis software Midas Civil was used to discretize the bridge into separate entities, establish its spatial model, and analyze the law of shear lag effect in the longitudinal direction during the main construction stage and the completion stage separately. The shear lag effect is more prominent at certain key points due to the influence of the tension of the boom and the weight of the arch foot during the construction stage. After the bridge is completed, the axial pressure of the arch foot drives the shear lag effect near the midpoint of the main girder section to its maximum; the axial force is transmitted along the longitudinal bridge direction in a V shape along which it gradually decreases. Under the action of uniformly distributed load, the cross-section of the box girder near the middle fulcrum is affected by the axial force of the arch foot; there is both a positive and negative shear lag effect. Under the eccentric load, the positive and negative shear lag effects appear simultaneously at the end fulcrum. The shear lag coefficient is higher in the web on the eccentric load side than the non-load side. There is obvious and widely fluctuating positive/negative shear lag effect in the vicinity of the middle fulcrum. There is significant tensile stress on the roof under the action of the middle fulcrum. The cross-sectional stress of a single-box seven-cell box girder under compression-bending load action was analyzed according to the finite element analysis results. The stress was decomposed into a superposition of bending moment action and axial force action. The shear lag coefficient λ M under the action of bending moment was also solved via energy variation method. Assuming that the axial force is only borne by the compressed area, the shear lag coefficient λ N under the action of the axial force was obtained; λ M and λ N were superimposed to determine the comprehensive shear lag effect coefficient λ .

The main hall of the Nanchan Temple, the oldest wooden building of the Tang Dynasty (782 C.E.) in China, was built 1200 years ago, representing a valuable heritage building. Thus far, research on the Nanchan Temple has focused on stylistic comparisons and historical documentary evidence. This study concentrates on the oldest timber-framed structure, with our experiments designed to understand the structural behavior of the hall. In this study, a 1:10-scaled specimen of a timber-framed building was fabricated based on the construction method of Yingzao Fashi, and the main hall of the Nanchan Temple was first reviewed; then, quasi-static tests were conducted under different vertical loads to ascertain the seismic mechanism of the oldest wooden building. The stiffness, energy dissipation, vertical load transfer path, bending stress of the component, and axial force were investigated. According to the results obtained on the vertical load transfer path, the roof was found to cause stress to the structural sections. The results indicate that the vertical load of the roof above Cha Shou is transferred down through Ping Liang; it then passes through Ping Liang to Tuo Feng and eventually passes to Sichuan Fu, which causes deformation. We increased the vertical loads, resulting in the increased lateral resistance (resilience) of the Nanchan Temple, and the stability of the timber-framed building in relation to the vertical loads was investigated. Moreover, the effects of horizontal and vertical loads were studied, and thus, we provide proposals for repair and conservation.

Most of the coefficients for the design of reinforced concrete rectangular slabs, recommended in the current provisions of design codes worldwide, do not include the case of slab cast monolithically with their supporting beams, some were computed with approximated methods in plates supported on rigid beams, and some of them are underestimated. Consequently, insufficient steel reinforcement areas may be computed with the available coefficients, which is unsafe. To guarantee safe designs of reinforced one-way and two-way concrete rectangular slabs with the coefficient method, the updating of the simplified flexural moment coefficients, computed with computational mechanics, is performed in this paper. These computed coefficients are compared with the regulatory coefficients recommended in the current provisions of design codes worldwide. It is shown that approximately 50% of the current provided design coefficients are underestimated, so they must be updated to guaranty the structural stability and integrity of slabs. The slabs, columns and supporting beams were modelled with shells and frames FE, respectively, in the software SAP2000. The strain energy was the criterion to choose an appropriate FE mesh size in such a way that the slab models yield accurate results. Seven types of panels are studied, considering two types of construction: slabs cast monolithically and not cast monolithically with their supporting beams. Additionally, two types of supports were modelled: flexible supports and rigid supports; in the former, panels are supported on principal beams with vertical supports at the intersection of the beams and in the latter, panels are supported on confined masonry walls. A comparative design example of a slab with six panels, using both the current provided design coefficients and the proposed coefficients, is presented, where the panels designed with the latter coefficients require more reinforcement than those designed with the former coefficients. Consequently, safer designs are obtained with the proposed coefficients.

In this study, a deep excavation in an under-consolidated deposit in Zhuhai, China, was reported and investigated via plane strain finite element analysis (FEA). First, the project was simulated via FEA (under-consolidated deposit), and a reasonable agreement between the lateral displacement of the measured and simulated retaining wall was obtained. Another FEA was then conducted under the assumption that the deposit was in a normally consolidated state. The numerical results indicate that the under-consolidated case resulted in a 25% increase in maximum lateral displacement of the contiguous pile-formed retaining wall, a 32% increase in bending moment in the wall, and approximately twice the maximum surface settlement behind the wall, when compared with those of the normally consolidated case. The main reasons for this are as follows: (1) the under-consolidated deposit was weaker, and (2) the ongoing consolidation of the under-consolidated deposit induced green-field settlement (approximately 4 mm) during the project period, thereby enhancing the bending deformation of the wall. Therefore, when designing deep excavation in an under-consolidated deposit, not only its weaker strength but also the negative effect of green-field settlement during the project period should be considered.

A pile foundation with ground improvement under the footing is a composite foundation with the objectives of enhancing the seismic performance and rationalizing the substructure by combining the pile foundation with ground improvement. Although the effectiveness of this method has been confirmed in previous studies for application to soft grounds, the applicability of this method to liquefiable grounds has yet to be fully investigated. In this study, therefore, centrifuge model tests and finite element analyses were conducted to clarify the effectiveness of this method and to ascertain the improvement in strength (stiffness) when the method is applied to a liquefiable ground. Firstly, in order to investigate the effect of an improved ground on the behavior of the pile foundation during liquefaction, dynamic centrifuge model tests were conducted for three cases with different strengths of the improved ground. Then, three-dimensional soil–water coupled finite element analyses of the centrifuge model experiments were performed to validate the applicability of the analytical method. After that, parametric studies, in which the strength of the improved ground and the input ground motion were changed, were conducted using the same analytical model. The results confirmed that the horizontal displacement of the pile heads was reduced by the improved ground even in the liquefiable ground, and that the effect of this reduction was more remarkable in cases of high stiffness of the improved ground. Furthermore, it was possible to reduce the bending moments at the pile heads by applying the ground improvement. However, since the bending moment at the boundary between the improved ground and the natural ground became the local maximum, there was an optimum stiffness of the ground improvement at which the maximum bending moment of the piles was reduced. This is because improving the ground around the pile heads has the same effect as extending the footing. It was thus concluded that the behavior of the pile foundation is similar to that of a composite foundation comprised of a caisson and group piles.

Laminated rubber bearings have a large compression stiffness and small tension stiffness and isolation layers show rocking deformation under bending moments. The application of isolation technology is limited in high-rise structures due to the unequal compression and tension stiffnesses. The rocking effect of a high-rise isolated structure was investigated in this work. To do this, a dynamic model of a high-rise isolated structure considering non-linear tension behaviour of the isolator and the stiffness centre offset was established. The limit criterion of the rocking angle and the corresponding input peak ground acceleration of the tension limit, damage limit and collapse limit were determined. A shaking table test of the isolated model was conducted and the aspect ratio was found to have a great influence on the structural rocking response. The response of the large aspect ratio (LAR) model was larger than that of a model with a small aspect ratio. The bearings in the LAR model were more likely to be tensioned. The test results and numerical simulations were close, confirming the accuracy of the proposed dynamic model and the limit criteria. Subsequently, dynamic analysis of frame–shear wall structures was conducted and the influence of aspect ratio and earthquake level was investigated. The proposed theories can be applied for direct predictions of rocking response and the performance state of isolators.

The aim of this paper is to investigate the seismic behavior of square concrete columns reinforced with Grade 600 MPa steel under high axial load and specify the service strength of Grade 600 MPa longitudinal bars. For these purposes, seven high-strength reinforced concrete cantilever columns with high axial compression ratio (0.64) and low aspect ratio (3.3) were constructed and tested under constant axial loading and cyclic lateral loading. A new configuration of transverse reinforcement was proposed and applied in these specimens. The main variables carried out in the current experiment include longitudinal bars ratio, transverse reinforcing strength, and the spacing of transverse bars. The milestone behaviors of these specimens were estimated and interpreted using multiple performance indexes, including failure pattern, hysteresis response, strength capacity, flexural ductility, energy dissipation capacity, strength degradation, and stiffness deterioration. Test results indicated that these specimens can be satisfied with aseismic requirement of Chinese code GB 50011-2010. Based on the strain of longitudinal bars test results, the service strength of Grade 600 MPa longitudinal bars can be specified as 560 MPa in this study. An added design suggestion is proposed with the amount of transverse reinforcement requirement to ensure seismic performance of these columns using the effective confinement index (keρshfyh/fc’). A fiber section analysis program was conducted in XTRACT finite element software. The analysis show that the failure mode of specimens was transformed with a given high axial compression ratio when the confinement effect of core concrete was considered. The method of the China Concrete Code (GB50010-2010) for determining seismic bending moment capacity of RC column was extended on the basic of confined concrete theory. Compared with experimental results, the conservative calculation results were obtained in this manuscript. It could be referenced for engineering seismic design.