Advances on Structural Engineering, 2nd Volume

This study proposes a computational fluid dynamics and computational structure dynamics (CFD/CSD) coupled method for calculating the buffet response of a variant tail wing. The large-scale separated flow in the buffet is simulated by the detached vortex approach, vibration deformation of the tail wing is solved by the dynamic mesh generation technique, and structural modeling is based on the mode method. The aerodynamic elastic coupling is calculated through the cyclic iteration of aerodynamics and the structural solution in the time domain. We verify the correctness of the proposed method through a typical delta wing calculation case, further simulate the buffet response of a variant tail wing in maneuver state, and finally realize buffet mitigation using an active excitation method. Overall, this study can provide an important reference for the design of variant-tailed aircraft. Full article

New or in-service truss bridges, with or without upper bracing systems, may display instability phenomena such as general lateral torsional buckling of the upper chord. The buckling of structural elements, particularly in the case of steel bridges, can be associated with the risk of collapse or temporary/permanent withdrawal from service. Such incidents have occurred in the case of several bridges in different countries: the collapse of the Dee bridge with truss girders in 1847 in Cheshire, England; the collapse of the semi-parabolic truss girder bridge near Ljubičevo over the Morava River in Serbia in 1892; the collapse of the Dysart bridge in Cambria County, Pennsylvania in 2007; the collapse of the Chauras bridge in Uttarakhand, India in 2012; and the collapse of a bridge in Nova Scotia, Canada (2020), and such examples may continue. Buckling poses a significant danger as it often occurs at lower load values compared to those considered during the design phase. Additionally, this phenomenon can manifest suddenly, without prior warning, rendering intervention for its prevention impossible or futile. In contemporary times, most research and design calculation software offer the capability to establish preliminary values for buckling loads, even for highly intricate structures. This is typically achieved through linear eigenvalue buckling analyses, often followed by significantly more complex large displacement nonlinear analyses. However, interpreting the results for complex bridge structures can be challenging, and their accuracy is difficult to ascertain. Consequently, this paper aims to introduce an original method for a more straightforward estimation of the buckling load of the upper chord in steel truss bridges. This method utilizes the theory of beams on discrete elastic supports. The buckling load of the upper chord was determined using both the finite element method and the proposed methodology, yielding highly consistent results. Full article

In recent years, the alarming number of terrorist attacks has highlighted the critical need for extensive research aimed at fortifying structures against explosion-induced loads. However, the insufficient energy absorption and brittleness of conventional concrete make it ineffective in withstanding blast loading, encouraging researchers to explore innovative strategies for augmenting the energy dissipation capabilities of construction materials. This study specifically delves into the incorporation of recycled rubber, a sustainable and environmentally friendly solution to the pressing issue of scrap tire disposal. The primary focus of this research revolves around the integration of rubber recycling and steel fibers into concrete, with the ultimate goal of enhancing the dynamic response of reinforced concrete (RC) beams. This novel approach not only contributes to the structural resilience required for resisting blast impacts, but also aligns with eco-friendly practices by reusing recycled rubber. A meticulous numerical investigation was undertaken to comprehensively assess the static and blast response of these augmented beams. The numerical study involved developing finite element (FE) models using ABAQUS version 6.14 for static implicit analysis and LS-DYNA R11 for blast explicit simulations. The ABAQUS model was validated against previous experimental testing for load–displacement and failure patterns. Similarly, the LS-DYNA model was validated for blast pressure in accordance with UFC-3-340 standards and for material response under blast loading, utilizing existing experimental data. The numerical models were designed to accommodate varying weight percentages of rubber, ranging from 5% to 20%, and a consistent 1.0% incorporation of steel fibers. This comprehensive analysis aims to provide valuable insights into the efficacy of these materials in improving the structural integrity and blast resistance of RC beams, thereby contributing to the development of more secure and sustainable construction practices. By reducing the reinforcement ratio in order to meet the minimum code requirements, it became evident that the failures of the rubberized RC beams tended to exhibit ductility on the tension side under static loading. In addition, the increase in the reinforcement ratio correlated with a higher failure load and decreased deflection. Furthermore, the findings indicated an optimal concrete mixture characterized by improved ductility, energy absorption, and blast load capacity, achieved by combining 5–10% rubber with steel fibers. Full article

This article introduces the experimental and analytical research results of two precast insulation mortar concrete sandwich panels (PIMSP) and two precast concrete composite panels as one-way slabs under bending load. Obtaining a prefabricated floor slab that can balance thermal insulation and structural performance can reduce material consumption and increase inter-story usage height. As the sandwich material for PIMSP, insulation mortar with a strength of 6 MPa was used. Truss-shaped shear connectors were used for shear force transfer. Then, finite element analysis was used to analyze and study the unidirectional flat plate model. The results showed that the tested PIMSP achieved a complete composite effect in the elastic stage and a semi-composite effect in the plastic stage. The PIMSP crack pattern resembles that of a precast concrete slab when utilized as a one-way slab. The load transfer capacity of truss-shaped shear connectors is relatively small, and it is mainly used as a connection between floors. Experiments have demonstrated that PIMSP panels can serve as a structural substitute for regular concrete floors in residential buildings. Full article

A cantilever block wall-panel attachment strip (CBW) flexible connection node was designed to connect precast concrete (PC) exterior wall panels to steel frames. To investigate the performance of the CBW flexible connection node and PC exterior wall panels during earthquakes, a partial two-storey steel frame was extracted from an actual engineering structure, and a full-scale steel frame–exterior wall panel shaking-table model was designed. Two sets of shaking-table tests were conducted under seismic intensity 7, 8, and 9 (Chinese Seismic Intensity Scale) earthquakes. The acceleration and displacement responses of the composite wall panel, open window panel, and integral wall panel along the in-plane and out-of-plane motions were analysed. The acceleration amplification factors of the PC exterior wall panels ranged from 0.753 to 1.400 (in-plane) and from 0.998 to 2.199 (out-of-plane). The CBW flexible connection node had a deformation capacity that could coordinate the deformation of the exterior wall panel and prevent severe damage. The surfaces of the PC exterior wall panels remained intact during a very strong seismic intensity 9 earthquake. Full article

To investigate the damage characteristics of the lower critical damage coal samples under different perimeter pressure unloading spans, a 13-group plus unloading perimeter pressure and then uniaxial loading test scheme was designed. Firstly, the coal samples were subjected to triaxial lowering and raising of the circumferential pressure to determine the critical damage range of the coal samples. Finally, acoustic emission signal, fractal theory, and energy theory were used to study the mechanical characteristics of the coal samples during damage. The results show that the surface cracks of the critically damaged coal samples develop from tension cracks to coexistence of tension and shear cracks to shear cracks as the unloading span of the surrounding pressure of the critically damaged coal samples decreases; through the triaxial unloading–uniaxial reloading experimental scheme, the critical damage range of the coal samples is determined as 60–70% of the triaxial compressive strength during axial pressure loading in the process of surrounding rock stress adjustment. The smaller the unloading span of the critically damaged coal sample, the smaller the peak strength of the sample, the more severe the damage, the weaker the energy storage capacity, the weaker the ability to deform elastically, the easier it is for the specimen to crack and deform plastically, and the larger the weak surface formed in the specimen, resulting in the larger the size of the fragment produced by the damage, the smaller the fractal dimension. Full article

This study aims to investigate the local elastic buckling behavior of simply-supported prismatic web plates under pure shear loading. Comprehensive finite element analysis is conducted to analyze the effects of various geometric parameters, such as tapering ratio, aspect ratio, and web slenderness, on the local elastic buckling behavior with simply-supported boundary conditions. An eigenvalue analysis is conducted to determine web plates’ natural frequencies and corresponding shape modes with varying geometric parameters. Particular attention is given to the effect of the slenderness ratio, since current formulas do not consider the impact of the slenderness ratio on the elastic shear buckling coefficient. A sensitivity analysis is conducted to examine the importance of the web slenderness ratio for estimating the critical buckling coefficient of a prismatic plate under pure shear loading. Finally, a formula of the elastic local critical buckling coefficient for a simply-supported prismatic web considering the web slenderness effect is proposed, which can be used in international codes. Full article

The steel tube-reinforced concrete (STRC) shear wall plays an important role in the seismic design of high-rise building structures. Due to the synergistic collaboration between steel tubes and concrete, they effectively enhance the ductility and energy dissipation capacity of conventional shear walls. To identify vulnerable areas prone to brittle failure and optimize the design, it is essential to develop a rapid method for identifying the failure mode of STRC shear walls. In this study, a fast identification method of STCR shear wall failure modes based on a Blending fusion model with Generative Adversarial Network (GAN) augmented data is proposed. The GAN is employed to address the issue of inadequate experimental data by generating new samples. This method combines classification boosting (Catboost), Random Forest (RF), K-Nearest Neighbors (KNN), and Least Absolute Shrinkage and Selection Operator (LASSO) to establish the Blending-CRKL fusion model to improve the prediction accuracy of the failure mode of STRC shear walls. The results reveal a significant improvement in the prediction performance of KNN, Backpropagation Neural Network (BPNN), RF, Light Gradient Boosting Machine (LightGBM), Catboost, and Blending-CRKL models after augmenting the training set with GAN. On average, the accuracy increased by 13%, precision increased by 81%, recall increased by 48%, and F1 score increased by 67%. The proposed Blending-CRKL fusion model outperforms the tested KNN, BPNN, RF, LightGBM, and Catboost models, achieving an accuracy rate of 97% in predicting the failure mode of STRC shear walls. Additionally, the stability and robustness of the Blending-CRKL model were validated, while the important features and value ranges of different failure modes were analyzed. This study provides a reference for the rapid identification of the failure mode of STRC shear walls. Full article

In order to accommodate more transportation-supporting facilities, the expansion of structures’ inner diameter has become the development trend of metro shield tunnels. But for large inner-diameter shield tunnels, the segment thickness design and bearing performance characteristics of tunnels under lateral unloading are still unclear. The purpose of the research was to select the optimal segment thickness and clarify the bearing performance of large inner-diameter shield tunnels. Therefore, in this study, a 3D refined numerical model was established to analyze and determine the optimal segment thickness for a shield tunnel with an inner diameter of 5.9 m. Furthermore, a full-scale test was carried out to study the bearing performance of the shield tunnel under lateral unloading. The results showed that the maximum tunnel horizontal deformation difference between the calculation and the test did not exceed 5%, and the maximum difference in the overall structure deformation between the calculation and the test did not exceed 7%. Increasing the segment thickness can reduce the convergence deformation of the shield tunnel nonlinearly; the deformation reduction was no longer significant when the segment thickness increased to 400 mm with an inner diameter of 5.9 m. Under the lateral unloading condition, the internal force of the tunnel structure increased significantly at sections of 0°, 55°, 125°, and 190°. Compared with the normal design load stage, the maximum bending moment and axial force increased by 36% and 74.1%, respectively, in the final failure stage. There was no bolt yield during the entire unloading process, indicating that the excessive strength of the bolt could not fully play a role in the entire life cycle of the large inner-diameter tunnel structure. The failure mechanism of the shield tunnel can be described as follows: in the early stage of a load, a shield tunnel will appear with joints open and dislocated. As the load increases, cracks in different directions gradually appear near the tunnel joint. In the ultimate load stage, the shield tunnel loses load-bearing capacity, and large areas of falling blocks appear at the top and bottom of the tunnel. Full article

A new method to evaluate the maximum seismic story velocities for steel buildings is examined here. It is well known that story velocities are vital parameters for the design of steel structures with supplementary dampers. It has been recognized that nonlinear time history analysis is required to achieve an accurate evaluation of actual velocities, but this approach seems to be complicated and time-consuming for practical engineers. For this reason, this paper investigates the inelastic velocity ratio, which can be defined as the ratio of the maximum inelastic velocity to the maximum elastic one for steel buildings. The knowledge of this ratio, a unique factor for the whole structure, can be used to evaluate the maximum inelastic story velocities directly from the elastic counterparts. The proposed study is general and can be used in both ordinary steel structures as well as steel structures with supplemental damping devices. Widespread parametric studies are executed to achieve simple yet effective expressions for inelastic velocity ratios. Full article

Blast loadings have become the subject of research in recent decades due to the threats they pose to the surrounding medium. On 4 August 2020, a huge explosion occurred in the Port of Beirut that led to massive damages in the medium surrounding it. Researchers have conducted studies in order to estimate the equivalent explosive mass as well as the damage extent left on structures; however, the studies considered the soil–structure interaction by simple methods. For that, this paper aims to understand the effect of explosion on the grain silo structure present at the port with an emphasis on the soil–structure interaction effects. The structure consists of a group of silos resting on a raft footing that is supported by group of driven piles. A soil–structure model analysis is performed in order to investigate the soil behavior, the damage extent in piles, and the soil–structure interaction due to the Beirut explosion using the CEL (Coupled Eulerian–Lagrangian) approach that suits events involving large deformation. The analysis is performed using the ABAQUS/Explicit FEM software (version 6.14) taking into account the properties of soil medium, the contact algorithm at the soil–structure interface, and the boundary conditions in order to better simulate the real field conditions and ensure accurate results. The work is primarily validated through site data such as the crater size and silo damage. Full article

Saline soils belong to the category of problematic soils with high compressibility and weak shear strength when exposed to water. Water dissolves the salts in soils which are the primary cementing agents. Therefore, stabilization methods that provide sustainable cementing substances are employed in this study using deep soil mixing techniques to enhance the properties of saline soil. In this regard, a laboratory-scaled deep soil mixing procedure was developed to treat the soil in a way similar to the field methods. A binder, consisting of marble powder and cement, was employed to treat the soil. This study aimed to select the most efficient binder mix design in terms of optimum marble powder/cement ratio and optimum water/binder ratio. Unconfined compressive strength, durability, density measurements and ultrasonic velocity pulse tests were conducted on the treated soil. To determine the treatment efficacy, microstructure analysis of the treated samples was conducted. The 80C20MP and 70C30MP samples exhibit a dense soil structure with minimal voids, and their microstructure is denser than the other treated specimens. Additionally, the EDX analysis shows increased calcium percentages with up to 30% MP replacement, aligning well with the microstructure analysis and the UCS values. The results indicate that the economical and eco-friendly binder mix consisted of (70% to 80%) cement and (20% to 30%) marble powder with water/binder ratio in the range of 1.1 to 1.3. This mix contributed greatly to the improvement in soil strength and integrated columns. Full article

The innovation inherent to employing expanded polystyrene (EPS) beads lies in its transformative impact on traditional concrete practices. Through the incorporation of EPS beads in concrete mixtures, a novel approach emerges that significantly alters the material’s characteristics, and opens up new avenues for construction and design. Studying the shear behavior of RC beams made with EPS beads is essential for advancing knowledge, improving design practices, ensuring structural integrity, and promoting the effective and responsible use of innovative materials in construction. This research experimentally investigated the effect of using EPS beads and pozzolana aggregate (PA) on the shear behavior of the RC beams. A total of 27 simply supported rectangular beams were cast, using three novel distinct mix designs, and were subjected to two-point load testing until failure. These three mixes were categorized as follows: a control mix, a mix with only EPS, and a mix with EPS, along with an additive. The ultimate failure load was experimentally recorded for all specimens, and the influence of the temperature (300 °C and 600 °C) on the RC beams made with EPS was examined. The findings revealed a reduction in the concrete compressive strength and density in the beams containing EPS and EPS with superplasticizers of (21.7%, 24.9%) and (11.3%, 16.2%), respectively. Additionally, EPS played a significant role in diminishing the ultimate shear capacity of the beams, compared to the control beams, by about 19.4%. However, the addition of a superplasticizer along with the EPS helped to maintain the beam capacity, to some extent. Conversely, the beams exposed to a temperature of 300 °C exhibited an almost similar capacity to that of the control beams without heating. Nevertheless, at 600 °C, the beams displayed a noticeable decrease in the ultimate load capacity, compared to the unheated control beams. Full article

To overcome the limitations of using time interval division to calculate the bridge impact coefficient (IM), a sieving method has been proposed. This method employs multiple sieves on bridge time–history curve samples to ultimately obtain the bridge impact coefficients. Firstly, CA cellular automata are used to establish different levels of traffic flow fleet models. The random traffic flow–bridge coupling dynamic model is established through wheel–bridge displacement coordination and mechanical coupling relationships based on the theory of modal synthesis. Then, the variation of bridge dynamic time–history curves for different classes of random traffic flow, speed and pavement unevenness parameters are analyzed. The sieving method is applied to screen the extreme points of the dynamic time–history curve of the bridge, enabling the distribution law of the bridge IM to be obtained using the Kolmogorov–Smirnov test (K–S test) and statistical analysis. Finally, the calculated value is then compared with the IM specifications of multiple countries. The results show that the proposed method has high identification accuracy and produces a good inspection effect. The value obtained using the sieving method is slightly larger than the value specified in the US code, 0.33, which is considerably larger than the values specified in other national codes. As pavement conditions deteriorate, the IM of the bridge increases rapidly, especially under Class C and Class D pavement unevenness, which exceed the values specified in various national bridge specifications. Full article

This study addresses the problem of predicting convergence outcomes in the Duffing equation, a nonlinear second-order differential equation. The Duffing equation exhibits intriguing behavior in both undamped free vibration and forced vibration with damping, making it a subject of significant interest. In undamped free vibration, the convergence result oscillates randomly between 1 and −1, contingent upon initial conditions. For forced vibration with damping, multiple variables, including initial conditions and external forces, influence the vibration patterns, leading to diverse outcomes. To tackle this complex problem, we employ the fourth-order Runge–Kutta method to gather convergence results for both scenarios. Our approach leverages machine learning techniques, specifically the Long Short-Term Memory (LSTM) model and the LSTM-Neural Network (LSTM-NN) hybrid model. The LSTM-NN model, featuring additional hidden layers of neurons, offers enhanced predictive capabilities, achieving an impressive 98% accuracy on binary datasets. However, when predicting multiple solutions, the traditional LSTM method excels. The research encompasses three critical stages: data preprocessing, model training, and verification. Our findings demonstrate that while the LSTM-NN model performs exceptionally well in predicting binary outcomes, the LSTM model surpasses it in predicting multiple solutions. Full article

Passive energy dissipation systems and devices are helpful in mitigating the danger of earthquake damage to structures. Metallic slit dampers (MSDs) are one of the most efficient and cost-effective solutions for decreasing seismic energy intake. The potential importance of MSDs in managing vibrations and limiting structural fatigue continues to grow as research advances and new materials and designs are introduced. This study evaluated the seismic performance of single-plate MSDs (SPMSDs) through a combination of numerical simulation and assessment of experimental results. ABAQUS software was used to create an assembly consisting of endplates, bolts, and SPMSDs. A real-world earthquake scenario was simulated using cyclic loads based on ASCE/SEI standards, and displacement-measuring devices such as strain gauges and LVDT were employed to record the behavior of the SPMSDs. The results of the experiment are used to assess the compliance of the SPMSDs and discuss their behavior as they undergo minimum and maximum displacements due to minimum and maximum applied forces. The energy dissipation capabilities of the dampers are presented by analyzing and comparing the area of their hysteresis loops, equivalent viscous damping, and their damping ratios. Actual failure modes are identified and shown to describe the limitations and potential vulnerability of the dampers. The relative error between the lowest and greatest recorded forces from experimental data and numerical simulation ranges from 4.4% to 5.7% for SPMSD 1 and from 1.6% to 2.1% for SPMSD 2, respectively. These deviation values represent a satisfactory level of precision, demonstrating that the numerical simulation accurately predicts the actual performance and behavior of the dampers when subjected to cyclic stress. The topology optimization performed in this study yielded an improved geometry of the SPMSD suited for a corresponding maximum considered earthquake (MCE_R) displacement of ±33 mm. This research also suggests practical implementations of the investigated and improved SPMSDs. Full article

Seismic isolation is a powerful tool for mitigating seismic risk and improving structural performance. However, some parameters, such as earthquake inputs and soil characteristics, influence the technology’s performance. This research aims to investigate the effects of soil–structure interaction (SSI) with regard to different moderate earthquakes associated with different distances of the source to the site, frequency content, and different soil characteristics on the seismic response of the isolated bridges. Near-fault (NF) and far-field (FF) records are applied to the conventional and isolated bridge with and without considering the underlying soil. For this reason, using the direct and simplified methods, three soil properties representing rock, dense, and stiff soils are modeled in Abaqus software. Nonlinear time history analysis (NLTHA) is carried out, and structural responses of both approaches in terms of maximum deck acceleration, base shear, and displacement of the deck and the isolation system are studied. Results demonstrate that the difference between the two approaches is significant. Using the simplified method is a rather simple approach that roughly captures the important features of the record characteristics and SSI. Furthermore, careful attention should be paid to the base shear responses and the isolator displacement demands, as they are significantly amplified in softer soils. In addition, the peak ground acceleration to peak ground velocity ratio (PGA/PGV) plays a decisive role in all dynamic responses. Records with a lower PGA/PGV ratio cause higher dynamic responses in terms of displacement and acceleration/force, regardless of the distance of the ruptured fault, while NF records show higher dynamic responses compared to FF records. Full article

Concrete-cored deep cement mixing (DCM) pile is a novel type of pile foundation, and its lateral dynamic response analysis has great practical significance. Based on the elastic dynamic theory, this study investigated the lateral dynamic response of a concrete-cored DCM pile in the single-phase viscoelastic soil using theoretical deduction and parametric analysis. Considering the special structure of the concrete-cored DCM pile, the lateral vibration equation of the concrete-cored DCM pile is first established with mechanical equilibrium, and then the dynamic behavior of the soil around the pile is described using the existing governing equations of single-phase soils. Subsequently, the solutions for the dynamic impedances at the pile top are deduced after a series of rigorous theoretical derivations. Finally, the influence of the pile and soil parameters on the dynamic impedances at the pile top is studied using calculation examples and parameter analysis. The results reveal that the radius of the concrete-cored DCM pile obviously affects the dynamic impedances at the pile top. Enhancing the elastic modulus of the concrete-cored DCM pile is beneficial for augmenting the dynamic impedances at the pile top. An improvement in the soil density will increase the stiffness factors of the dynamic impedances at the pile top but will reduce their damping factors. Full article

In this work, a test bed and stand structure were designed for the thrust test of an aircraft. The engine test rig consists of a thrust stand, test bed, transport system, and hoisting device. In this study, structural design and analysis of the stand and bed for engine thrust test equipment were performed. The stand structure supported the engine, and the test bed moved the thrust test equipment and the engine. Structural design loads were defined by analyzing the operating conditions. Structural analysis was performed based on the structural design results. As a result of analyzing the structural safety against thrust, which is the main design load, it was considered to be sufficiently safe. Finally, the target structure was manufactured to verify the design result. Full article

Fatigue-damaged concrete improves the load-bearing capacity of components by increasing the cross section. However, the creep performance of damaged components after the repair has received less attention. Thus, this study establishes a constitutive creep model of strengthened fatigue-damaged concrete on the basis of damage mechanics and numerically simulates the strengthened component. The accuracy of the proposed model is verified by conducting creep tests on fatigue-damaged concrete beams. According to the numerical simulation results, increasing the section height profoundly affects the ability to control their creep deflection. The incremental creep deflection of the beams with a strengthened section height of 50, 100, and 150 mm loaded for 365 days decreased by 0.107, 0.228, and 0.326 mm, respectively, compared with the unstrengthened damaged beam. Moreover, this reinforcement method excellently controls the deflection of the damaged components under a negative bending moment. The model can forecast the creep deformation of undamaged components or damaged components after being strengthened, which facilitates structural maintenance and decision-making about reinforcement. Full article

In order to safely and efficiently use soft rock aggregate cemented dams in red bed regions and promote the development of widely sourced cemented sand and gravel dam materials, the Jinjigou project in China applied soft rock for the first time in the construction of cemented material dams. This article further explores the concept of cemented material dams from conducting on-site direct shear tests and research on soft rock material ratios and explores and invents a new structure and construction method by combining soft rock cemented sand and gravel with cemented rockfill. This article also proposes a digital mixing and intelligent dynamic control method for cemented material dams with soft rock. The research results show that soft rock aggregate content not exceeding 60% can produce soft rock cemented gravel with a compressive strength of no less than 6 MPa. The stress on the dam body is small and does not produce tensile stress. The dam body with added soft rock has certain shear-bearing capacity, with a shear friction coefficient of 0.99~1.10 MPa, cohesion of 0.26~0.53 MPa, and high residual strength, accounting for 60~80% of the peak strength. At the same time, the problems of large fluctuations in moisture content and the uneven grading of the soft rock and riverbed gravel mix during the mixing and production process, and the significant influence on safety caused by the large strength dispersion of the cemented sand and gravel, are resolved, ensuring the quality of soft rock cemented sand and gravel preparation. The successful application of soft rock cemented material dams in Jinjigou has achieved a breakthrough in key technologies for soft rock cemented dam construction in red bed regions, proving the feasibility of soft rock cemented material dam construction and having broad prospects for application and promotion. Full article

Manufacturing process accuracy is obtained by proper arrangement of fixture elements known as fixture layout. A N-3-2-1 method is used for sheet metals which requires (N + 3) fixture elements to constrain deformation normal to surface. Genetic Algorithm (GA) is used for fixture layout optimization, but it requires high computational effort due to large number of populations. A new method for fixture layout optimization is proposed by integrating topology optimization into GA. In this method, topology optimization reduces the population for GA. The objective function is to reduce the population for GA and minimize total deformation normal to the plane of workpiece. The proposed approach comprised three stages. In the first stage, the initial number of clamps are determined. In the second stage, the population is reduced for GA and the feasible area of clamps are identified using the topology optimization technique. In the third stage, the number and position of clamps, earlier identified in stage one, are optimized using GA. Two different case studies are solved by varying applied load position and magnitude. The proposed method results 47.5% and 65% decreases in the population for subcase 1 and subcase 2, respectively. However, in subcase 3 and subcase 4 the population reduced was 90% and 80%, respectively. The 25% of reduced population is used as the convergence criteria. Similarly, total deformation normal to the plane is reduced in each subcase, with the highest reduction of 86.31% in subcase 1 and lowest of 59.85% in subcase 4. The experiment is performed on the first case study to validate results. This concludes that the proposed method is valid and that optimal results are found. Full article

Engineering site and shaft pillars are excavated to prolong the life of collieries and excavate more underground coal. The Jinggezhuang colliery (‘JGZ’) is a resource-exhausted coal mine in eastern China. It was determined that the industrial site and shaft pillar of JGZ would be extracted in 2008. This study excavated an experimental panel to examine the effect of pillar excavation on surface buildings in complicated geological conditions. A new pillar design was proposed based on surface monitoring to increase the recovery ratio. To maintain the safety of the shaft and engineering facilities, panel 0091 was mined and surface deformation was monitored during the experiment. The deformation characteristics and parameters were obtained using a back analysis method. A new pillar was designed using the parameters measured from panel 0091. The design maintained the safety of the shaft but relaxed the restriction of the influence of constructions at the engineering site. The prediction results of the surface subsidence and the deformation of the main building were analyzed. The maximum subsidence of the surface was 7419 mm, but the surface subsidence of the shafts was less than 10 mm. The shafts were weakly influenced by the pillar excavation. The prediction results can be used as basic information for the monitoring and maintenance of buildings in the future. Using the new pillar design, 2.54 million tons of coal resources were mined. This study provides an engineering example and a reference for shaft pillar excavation in the future. Full article

Southern Romania is a geographic region with alluvial deposits. This soil type leads to rather long corner periods and provides as a particularity of the response spectrum an enlarged plateau. These conditions produce large displacement demands. Moreover, pulse-type ground acceleration records make this seismic area more unique. Research on the seismic behaviour of structures built under such unusual conditions is limited and Romanian engineers are not confident to apply alternative solutions such as base isolation. Although capacity design is still the regular design method applied in Romania, modern base isolation solutions may overcome the large displacement demand expectation produced by seismic events and fulfil immediate occupancy requirements. This study presents the seismic performance of an existing hospital from Bucharest, for which two seismic design solutions were applied: (i) classical approach based on capacity design and (ii) base isolation. Both approaches are compared in terms of drift, acceleration and base shear values. Static as well as non-linear dynamic analysis methods were applied. Full article

This study presents analysis of two types of experimental test related to the crack propagation in concrete specimens subjected to high-sustained loading levels and quasi-static loadings. The concept of the equivalent crack length is introduced to perform this analysis. Even though this analysis is partial, it shows the influence of loading rate conditions on the crack process rate. This result shows that, in the domains of low and very low loading rates, the concrete mechanical characteristics linked to the cracking process (for example, tensile strength, post-cracking behaviour, etc.) are dependent on the loading rates applied to the specimens for determining them. Full article

In response to housing shortages in densely inhabited urban areas, there is a search for structural engineering solutions for serial and modular construction. Prefabricated concrete columns can make an important difference. Using industrial manufacturing processes, it is possible to produce highly loadable, durable and true-to-size columns that enable accelerated construction progress and dismantling or reuse of the components at the end of the structure’s economic life. However, there are challenges in designing the detachable connection between highly loaded columns due to an undesired reduction of the load-bearing capacity on the one hand and a high sensitivity to geometrical deviations on the other hand. To investigate the load-bearing and deformation behaviour of butt-jointed columns, large-scale component tests as well as three-dimensional numerical analyses using the finite element method were carried out. The analyses show that measures to increase the stiffness of the joint, such as thicker steel plates, lower mortar thickness, etc., lead to an increase of the ultimate load. It could also be demonstrated that butt-jointed columns are very sensitive to unevenness of the end faces. Finally, the investigations allow first conclusions on the design and detailing of detachable compression connections between prefabricated concrete columns. Full article

Geopolymer concrete is concrete made from industrial materials, such as fly ash, GGBS, silica fume, and metakaolin, used as a cement alternative. In this study, geopolymer concrete will be based on fly ash as a binder material, alkaline activators of sodium hydroxide and sodium silicate, GPC beams of dimensions 800 mm × 250 mm × 100 mm, circular columns with diameter 350 mm and depth of 700 mm and GPC slabs of dimensions 500 mm × 500 mm × 100 mm are all cast with fly ash content of 350 kg/m³. The ratio of alkaline solution to fly ash was equal to 0.5 and was kept constant, and the Na₂SiO₃-to-NaOH ratio was 2.5 and the NaOH molarity was kept constant at 12 M. The beams reinforcement was changed to study the shear and flexural behaviour, and the slabs and columns reinforcement ratio was kept constant. The load capacity, stress–strain behaviour of the GPC and load-deflection behaviours of the members were also examined. The results showed that reinforced geopolymer members can be used as an alternative to reinforced concrete structural members, but they are more expensive than reinforced concrete. Further study is recommended to provide more practical design recommendations for incorporating geopolymer concrete into structural elements in order to accelerate the adoption of this concrete for large-scale field applications in the future. Full article

The provisions for out-of-plane stability of steel arch bridges in three major design codes are presented in this paper. By employing an existing steel arch bridge as a model, the influence of bridge type, arch rib to lateral bracing stiffness ratio, rise-to-span ratio, arch rib spacing, and range of lateral bracing arrangements on the out-of-plane critical axial force of the arch rib is studied using FE analysis. The accuracy of the critical axial force provisions is then evaluated against the FE analysis. The results show that the influence of the rise-to-span ratio on critical axial force is generally small. The critical axial force decreases with increasing arch rib spacing when the stiffness ratio is relatively large. A smaller ratio of arch rib length provided with lateral bracing (γ-value) significantly reduces the critical axial force and normalized critical axial force decreases with increasing stiffness ratio. The critical axial force of half-through type arch bridges is lowest when the stiffness ratio is relatively small. A deck-type bridge has a larger critical axial force than a through-type bridge when the stiffness ratio is relatively large, while the results are the opposite when the ratio is small. The different assumptions made in the provisions result in the various parameters having different impacts on the out-of-plane critical axial force in each code, thus affecting code accuracy. Considering the influence of the rise-to-span ratio, ratio of lateral bracing, and arch rib spacing with different stiffness ratios, factors to improve the accuracy of the critical axial force obtained by the three codes are proposed for a practical design process. Full article

Flexural strengthening of steel structures by fastening fiber-reinforced polymers (FRPs) has been proposed by a few researchers to overcome the brittle de-bonding failure associated with the bonded strengthening technique. This paper investigates the experimental flexural performance of steel beams strengthened by fastening hybrid FRPs (HFRPs). Staggered steel bolts are used to attach the HFRP strips to the steel tension flange. Fourteen steel beams were tested in a four-point loading setup to examine their behavior under various bolt spacing values, HFRP lengths and HFRP thicknesses. All strengthened beams experienced ductile failure with yield load enhancement ranging between 5.22 and 11.73% and improvement in the ultimate load from 8.5 to 18.76%. Reducing the spacing between the bolts from 150 to 45 mm enhanced the ultimate load and the level of composite action between the fastened components. Doubling the HFRP length resulted in a slight increase in the ultimate load and a remarkable reduction in the mid-span deflection. Meanwhile, doubling the thickness of the HFRP revealed an insignificant effect on the beam’s ultimate load and composite action. The recorded sectional strains were used to analyze the level of composite action between the fastened elements. Full article

The coupled steel plate and reinforced concrete (C-SPRC) composite wall is a new type of coupled-wall system consisting of steel coupling beams (SCBs) that join two SPRC walls where the steel plate shear wall (SPSW) is embedded in the RC wall. Although the C-SPRC wall has been extensively constructed in high-rise buildings in seismic regions, research on its behavior has rarely been reported. No code provisions are available for directly guiding the preliminary design of such coupled-wall systems. In the research, three 1/3-scaled C-SPRC wall subassemblies including one-and-a-half stories of SPRC walls and a half-span of SCB were tested under simulated earthquake action, considering the fabrication method of the embedded SPSW and the shear-span ratio of the SPRC walls as two test variables. The prime concern of the research was to evaluate the influences of those popular design and construction parameters on the seismic behavior of the C-SPRC wall. Deviating from the beam tip loading method used in conventional subassembly tests, the lateral cyclic load in this research was applied at the top of the wall pier so that the behaviors of both walls and SCBs could be examined. The test results exhibited the great seismic performance of the subassemblies with the coupling mechanism fully developed. The energy dissipation capacity and inter-story deformation capacity of the subassembly with the assembled SPSW were roughly 9.4% and 13.2% greater than those with the conventional welded SPSW. Compared with the subassembly with the shear-span ratio of 2.2, the interstory-deformation capacity of the one with the shear-span ratio of 2.0 was increased by approximately 13.4%, while the energy dissipation capacity was decreased by 10.9%. The test results were further compared with the simulation results using the proven-reliable finite element analysis with respect to the hysteretic curves, skeleton curves, energy dissipation capacities and failure patterns. Full article

A new built-up closed-rib section is proposed that may improve the installation, performance, and durability of orthotropic steel bridge decks. The rib is composed of two partial or whole standard hot-rolled steel sections which are connected by a steel plate. The concept is used to design a built-up closed-rib replacement for the Benjamin Franklin Bridge deck. In addition, section performance was compared with the actual bulb section as well as a typical trapezoidal section through finite element simulations. The analyses indicate that the built-up section has smaller stress concentration values as compared with the other sections, and hence, improved fatigue resistance is expected. Finally, it is concluded that the built-up rib has potential to be considered in future orthotropic steel deck designs. Full article

Articulated slab bridges have been widely used by transportation administration for short-to-medium span bridges because of their good economy, convenient construction, and environmental advantages, while the presence of shear keys increases the complexity of structural behavior. Developing more reasonable analysis approaches of quick assessment, pre-design, and hand calculations for the articulated slab bridges is a challenge because of the peculiar shear key mechanism. This paper is devoted to presenting a recursive algorithm, based on the force equilibrium conditions of each individual slab, thus resulting in simultaneous equations of the transfer matrix method (TMM). In this procedure, the state vector is an array composed of vertical displacement, shear force, unit constant; and the transfer matrix contains the bending and torsional stiffness parameters of simply supported slabs. Then, the influence line of transverse load distribution (TLD) is calculated for each slab by introducing boundary conditions. To validate and verify the efficiency of the TMM algorithm, a transversely prefabricated void slab bridge with a span of 20 m is considered as a case study. The traditional force (FM) and finite element (FEM) methods are used for comparison and validation. It is demonstrated that the TMM can provide good results with higher algorithm efficiency by exempting the modeling tasks in FM and FEM and capture variations in TLD along the bridge’s span. In addition, the influence of the span length and relative stiffness coefficient of slabs on the TLD of articulated slab bridges are analyzed from the parametric analysis. Full article

Various random factors in the bridge construction process directly affect the safety of the bridge life cycle. The existing theories on the reliability of bridge structure mainly focus on the reliability of components and the reliability of the bridge structure system in the completion and operation stages, while the research on the reliability of the structure system in the construction stage is relatively lacking. Therefore, this paper proposed using the Copula function to calculate the reliability index of the bridge structure construction process system. The basic theory of the Copula function was introduced in detail, and the formula was improved according to the actual situation of bridge construction. Finally, the sensitivity analysis of bridge system reliability was carried out. The research results showed that the method proposed in this paper based on Copula theory to calculate the reliability index of the bridge structure construction process system has strong applicability, simple calculation, and can be used in conjunction with the “interval estimation method”, which is suitable for large and complex bridge structural engineering. At the same time, the conclusion that the influence of failure mode correlation on structural reliability should not be ignored in the actual engineering construction process is confirmed. Full article

To promote the development of timber–steel composite (TSC) structures, this paper proposes a TSC I-beam with an I-beam as the webs, covered with a timber board on its upper and lower surfaces and bolted together; the effect of varying the ratio of the timber board thickness to I-beam on the bending performance of the TSC I-beam was investigated. Considering the same total height of the beam cross-section and the variation of timber board thickness and I-beam height, three groups of six TSC beam specimens were designed and fabricated to carry out bending load failure tests, and the effects of the variation of timber board thickness with respect to I-beam height on the failure mode, flexural load capacity, ductility, and composite degree of TSC beams were analyzed. In addition, a model for predicting the elastic ultimate bending capacity and mid-span deflection of TSC I-beams was proposed on the basis of the composite coefficient method, which avoids the need to test the joints, and the theoretical calculation results were in good agreement with the test results, which can provide a reference for the design of TSC I-beams. Full article