Abstract:This paper provides a comprehensive review of the research on fiber-reinforced polymer（FRP） reinforced glulam bending members， systematically summarizes the existing reinforcing technologies， and elaborates on the influencing factors and analytical methods of the interfacial bond performance， the bending performance， and the creep performance of FRP-reinforced glulam beams. The findings demonstrate that FRP reinforcing technologies effectively utilize the strength of wood in glulam bending members， enhance their bending capacity， control bending deformation， and improve the brittle failure mode. Considering the constraints of FRP-reinforced glulam bending members in engineering applications， it also proposes key issues that need to be addressed in the research on the prestressing technologies， long-term performance， fire resistance， and reliability.

Abstract:Dowel laminated timber（DLT） is a kind of novelty structural timber made of lumber connected by dowels. Compared with glulam， it has the advantages of fast processing， low cost， and more green environmental protection. To evaluate the bending performance of DLT beams， eight groups of DLT beams were tested under four-point loads. The testing parameters include the types of dowels （wood and bamboo dowels）， dowel spacing （70， 100 and 140 mm）， and the number of laminates （3， 4， and 6 layers）. In addition， to reveal the contribution of the interfacial dowelled connection among lumbers to the bending performance of DLT beams， push-out tests were also conducted on the wood or bamboo dowelled connection of DLT. The test results indicate that the bamboo dowel connection show a higher slip stiffness and a better ductility compared with wood dowel connections， and the bending performance of DLT beams with a composite action range from 0.11 to 0.15 which is lower than that of glulam beams but higher than that of unconnected timber beams. The bending performance of DLT beams increases significantly when adding the number of the laminates， while reducing the dowel spacing could improve the bending capacity and stiffness of DLT beams. Due to the fact that the bending stiffness of the DLT beam would be overestimated by the γ method provided in Eurocode 5， a recommended reduction factor was proposed for the connection stiffness when it was used to calculate the bending stiffness of the DLT beam， to facilitate engineering design.

Abstract:In order to solve the difficulties of slotting and perforating of laminated bamboo， and the problem of bamboo splitting when the beam-to-column connections were rotated， the rotational behavior of innovative laminated bamboo beam-to-column connections using side steel plates and self-tapping screws were studied. Two types of connections were designed， and a monotonic loading test was conducted on 5 specimens， including T-shaped extended end plate connections with side plates that confine the beam and double L-shaped end bracket connection partially confining both the beam and column， to analyze the failure mode， initial stiffness， ultimate bearing capacity， deformation capacity， and ductility coefficient of the connections. The results of the test show that most mechanical parameters of T-connections are better than those of L-connections. The failure of the T-connection using more screws of smaller diameter （T8×8-M） is caused by tensile rupture of steel plates and self-tapping screws， while the failure of the T-connection using less screws of larger diameter （T6×10-M） is caused by bamboo splitting and shear failure of steel plates. The reinforcement of self-tapping screws transversely enhances the mechanical behavior of all connections， especially T-connections. The design code “Standard for design of engineered bamboo structures” （T/CECS 1101—2022） can conservatively predict the bending capacity of the laminate bamboo connections.

Abstract:Connections are essential in ensuring the seismic performance of timber structures， and the energy dissipation capacity of connections is an important index to measure the serviceability of connections for earthquakes. In this paper， the novel dissipative angle bracket and hold-down for cross-laminated timber（CLT） structures were proposed. Fifteen sets of cyclic loading tests were conducted to evaluate the failure mechanisms and mechanical properties of these connections. Almost all the tested specimens have a ductility larger than 9.0， meeting the requirements of Eurocode 8 for high ductility connections with D>6， and belonging to the high ductility class. The strength degradation of the novel dissipative connections in the working stage less than 20%， indicating the engineering applicability of the novel connections. The equivalent viscous damping ratio of the novel dissipative connections in the working stage is 12%~22%， and that of the common commercial connections is 2.5%~15.8%， indicating the high energy-consuming capacity of the novel connections.

Abstract:To investigate the lateral performance of the cross-laminated timber （CLT） shear walls connected by innovative energy-dissipating connections with a mechanism of “yielding of soft steel” and “shear deformation of rubber”， a series of monotonic and reversed cyclic loading tests were conducted on six full-scale specimens with a height of 2.4 meters， considering various factors including vertical load distributions， aspect ratios， and replaceability of the energy-dissipating connections. A comparative test was also conducted on a CLT wall specimen with common metal connections. The failure process， mechanical properties， and the influence of preset factors were obtained and analyzed. The results indicate that the damage of the CLT walls with the innovative energy-dissipating connections mainly concentrates on the dissipative connections with yielding fracture of the soft-steel dissipative sections and debonding failure of the rubber， preventing the CLT panels and screws from damage. The increase of the vertical load effectively enhances the lateral resistance performance of the wall， while the increase of aspect ratio mainly improves the deformation capacity and ductility of the wall. Compared with the wall with common metal connections， the load-carrying capacity of the wall with energy-dissipating connections is similar， but its ductility increases by 26%， energy dissipation capability increases by 38%， and the maximum inter-story drift can reach 1/23. Moreover， the lateral performance of the wall repaired by the in-situ replacement of the energy-dissipating connections is similar to that of the original wall. The results indicate that the CLT shear walls connected by innovative energy-dissipating connections exhibits an excellent seismic performance， which can achieve the design objective of replaceable connections and repairable structures after a strong earthquake.

Abstract:This paper introduces a novel node connection method in wooden structures known as the multi-bolt steel insert plate connection. It categorizes specimens into 12 groups， each containing six specimens， for tensile testing， with four influencing factors， i.e.， bolt number， arrangement， bolt diameter， and base material thickness considered. The parameters obtained include failure modes， initial stiffness， yield load， peak load， and ductility coefficient. The test results reveal that， under the same conditions of consistent wood thickness and bolt diameter， damage occurrence increases with the number of bolts， and the failure mode exhibits a similar pattern. Splitting cracks of different degrees emerge on the left and right sides of the wood， extending from the top to below the last row of bolts. In terms of mechanical properties， an increase in the number of bolts corresponds to higher initial stiffness， yield load， and peak load， accompanied by a decrease in ductility. Ultimately， formulas for the initial stiffness and peak load of multi-bolt steel insert plate connection nodes are derived， utilizing bolt diameter and quantity as independent variables. These formulas align closely with the experimental data， validating their accuracy.

Abstract:The impact of windborne debris on buildings is one of the most important causes of envelope destruction in strong wind. To build an impact damage probability model considering multiple factors for different type of building envelopes， an impact damage probability model of plate-like debris based on the three-dimensional plate-like debris trajectory considering Magnus effect is proposed. Compared with the commonly used models， this model additionally considers the effects of parameters of debris including different sources， initial conditions and relative positions of buildings at different wind speeds and in different wind directions. An impact damage estimation of a low-rise building roof considering multiple factors is given using the wind speeds of 15 m·s^-1~45 m·s^-1， the wind directions of 0°~90°， and the upstream building heights of 8.0 m~12.5 m to verify the availability of the model. The calculation method of this model is simple and can be applied to the vulnerability analysis of building roofs.

Abstract:The aim of this paper is to summarize existing studies with regards to residual seismic performance of steel structures considering atmospheric corrosion. First， the variation laws of corrosion degree of mild steel with time in atmospheric environment is discussed. Then， state-of-the-art about the influence of atmospheric corrosion on seismic behavior of steel structures is reviewed from material， structural member， and structural system. Finally， a detailed review is provided on the limitations of currents studied in this field. A review of the current work indicates that further study should be focused on new methods of corrosion prediction， modeling method considering corrosion pits distribution randomness， interdisciplinary study on weld corrosion and weld ultra-low cycle fatigue （ULCF）， and high-efficiency modeling method suitable for seismic fragility analysis of corroded steel structures.

Abstract:The soil sample is subjected to a coupling effect of wind and wave action with various frequencies during the operation of offshore wind turbines. A series of tests were conducted to investigate the influence of the frequency ratio between wind and wave loads on sand using a multi-directional cyclic simple system （VDDCSS）. The effect of frequency ratio on the dynamic strain，pore water pressure，and dynamic strength of sand was analyzed. The test results show that the development of shear strain is affected by the bidirectional frequency coupling and the combination of x and y-direction stress caused by the frequency ratio. At a C_SR of 0.15， the bidirectional frequency coupling effect is greater than the stress combination effect. With the increase of the stress level （at a C_SR of 0.20 or 0.25）， both the frequency coupling effect and the stress combination effect are strengthened. At a low-stress level， the pore pressure curve of the failed specimen is "upward concave" and the frequency ratio has little effect on the pore pressure development of other specimens. As the stress level increases （at a C_SR of 0.20 or 0.25）， the final value of pore pressure u_max increases with increasing C_SR. Except for the samples corresponding to a f_r of 1.00 and 10.00， the dynamic strength of others soil samples decreases with the increase of f_r and C_SR. At a f_r of 5.00， the sample has a large strain，a high pore pressure value， and a low dynamic strength， which is related to the superposition effect of the two-way frequency coupling and stress combination.

Abstract:The construction of underground tunnel engineering using the AGF method often encounters the problem of diaphragm walls affecting the frozen curtain development， which brings difficulties to the design of the freezing scheme and the evaluation of the sealing water effect， and endangers the safety of subsequent excavation operations. In order to find out the freezing temperature distribution under the action of adiabatic boundary such as diaphragm wall， and to grasp the development law under the local restriction of freezing curtain， a mathematical model of temperature field containing adiabatic boundary in semi-infinite plane was established. The analytical solution of single， double and triple freezing pipes were derived based on the thermal potential function and mirror method， and their accuracy and applicability were verified by numerical simulation. The results show that the analytical solution agrees well with the steady-state numerical results， the error with the transient results decreases gradually with freezing time， and the errors of three models on the 50th day are 0.39℃， 0.17℃， and 0.06℃， which can be controlled within 0.5℃. The isotherm is perpendicular to the boundary， and there is only heat flux parallel to the boundary but no normal heat flux. The adiabatic boundary is beneficial to the temperature reduction between the freezing pipes and adiabatic boundary. As the distance d increases， the effect of adiabatic boundary gradually decreases， and the freezing model transforms into an infinite model. Therefore， the pipe spacing l and boundary distance d should be reasonably matched according to the designed thickness of the frozen curtain in practical projects.

Abstract:Glulam bolted beam-to-column connections with slotted-in steel plates are usually regarded as hinges in structural design due to their low moment-resisting properties. In this paper， an innovative glulam reinforced beam-to-column connection with long steel rods was proposed， aiming to provide good moment-resistant properties for mid-rise timber frames without braces or infill shear walls. Three sets of specimens with different diameters of long steel rods were designed and manufactured. The stiffness， load-carrying capacities， failure modes， and energy-dissipating capacities of the specimens were analyzed based on the monotonic static loading tests and cyclic loading tests. Finite element models of such connections were developed using ABAQUS. The simulated results were proved to be consistent with the experimental results. Then， a parametric analysis was conducted based on the validated numerical models. The results reveal that the proposed connections have an excellent moment-resistant stiffness and a load-carrying capacity. The damage is mainly focused on the long steel rods following the concept of the connection. Besides， the damaged long steel rods can be replaced after being damaged， extending the seismic resilience and the life span of the proposed connections. The results from the parametric analysis show that the moment-resistant stiffness is positively associated with the diameter and the arm of long steel rods. Finally， based on the experimental and numerical results， a theoretical approach was proposed to estimate the moment-resistant stiffness and load-carrying capacity. The approach proposed provides important reference for the future design of such innovative connections in real projects.

Abstract:In order to make the design of cold recycled mixture in the laboratory truly reflect the actual working conditions in the field， this paper measured the process of temperature variation in the cold recycled layer during the construction of the hot-mix asphalt（HMA） mixture above the cold recycled layer. Based on the measured temperature， the effect of the cold recycled layer thickness， the overlying hot-mix layer thickness， and construction seasons were analyzed. The temperature prediction equations in the cold recycled layer were established. Simultaneously， the volumetric parameters and mechanical strength of the core samples after the secondary thermal compaction of the cold recycled layer at different construction temperatures were tested. The results show that during the paving process of the HMA， the temperature change in the cold recycled layer is greatly affected by the construction environment. The void ratio， flexural tensile strength， shear strength， and fracture work of cold recycled mixture are significantly affected by the construction temperature and laboratory secondary forming temperature. Compared with 0 ℃， when the construction temperature is about 30 ℃， the void ratio is reduced by about 25%， while the flexural tensile strength， shear strength， and fracture work are increased by at least 45%， 66%， and 77% respectively. Compared with 40 ℃， when the laboratory secondary compaction temperature is 80 ℃， the void ratio decreases by about 20%， while the flexural tensile strength， shear strength， and fracture work increase by at least 42%， 35%， and 80% respectively. The influence of secondary forming temperature should be considered in the design of cold recycled mixture to simulate the effect of the cold recycled layer on the performance due to the change of internal temperature.

Abstract:Real-time scheduling plays an important decision-making role in public transport operation organization because of its flexibility. Although the current scheduling （or dispatcher） performance evaluation can assess the implementation of the bus schedule， it ignores the passenger experience and enterprise input-output evaluation of the scheduling performance. It also does not support backtracking the implementation performance of the scheduling in the past. In order to enable dispatchers to accurately improve their dispatching skills and performance， solve problems such as wasted capacity caused by lagging dispatching decisions and increase passenger satisfaction， from the two dimensions of input-output and retrospective dynamic evaluation， this paper proposes a performance evaluation method for bus scheduling based on the three-stage Super-SBM （super-efficiency slack-based measurement） model. Considering the impact of road conditions and passenger flow on the scheduling performance， and based on the existing indicators， three output indicators， i.e.， travel speed， waiting time change rate， and standard deviation of load factor， are added from the perspective of passengers to build an evaluation system. The retrospective evaluation of the actual scheduling of two bus routes in Shanghai verifies that the evaluation method proposed in this paper can more accurately distinguish the difference in scheduling performances. The results show that the flexible scheduling strategy in peak periods can produce more obvious benefits than that in off-peak periods， and the scheduling strategy shows different applicability in different space-time scenarios. The retrospective analysis of the performance of historical scheduling records， on the one hand， can provide scheduling decision support for dispatchers in different scenarios， and on the other hand， can select appropriate learning samples for the real-time bus scheduling strategy generation technology based on machine learning， to improve the efficiency of bus operation and organization.

Abstract:Antibiotic resistance genes（ARGs） are widely distributed in water and soil as a new type of pollutants. Microorganisms which pose a potential threat to human health obtain antibiotic resistance through the proliferation of ARGs. In order to study the possible health risks of a large number of ARGs in urban drinking water systems at this stage， this paper first combines the data reported in the domestic and international literature， introduces the current situation of ARGs contamination in urban drinking water systems， describes their storage characteristics， and finds that the number of ARGs in urban drinking water systems at home and abroad is not to be underestimated， and the number of the highest number of ARGs can be up to 1.38×10⁵ copies·ml^-1. Then， it summarizes the influences of commonly used processes in urban drinking water systems on ARGs accumulation and propagation. It is found that commonly used water treatment processes in urban areas have poor inactivation effects on ARGs， and even tend to promote their enrichment and propagation. Among different environmental factors， microbial community structure is the main driving force influencing ARGs， followed by heavy metals. Finally， it proposes the possible health risks of ARGs to human beings and the limitations of the existing health risk assessment methods， and prospects the future research on ARGs.

Abstract:The extraction of shale oil and gas produces a large number of waste materials that are generally discharged into the groundwater environment， causing contamination of groundwater which threatens human health. First， the distribution and storage mechanism of shale oil and gas， as well as the extraction technologies， which include oil shale retorting， horizontal drilling， and hydraulic fracturing， are introduced. Then， various events that may cause groundwater pollution and the main sources of contamination in the extraction processes， which consist of preparations， drilling and fracturing， and capture of shale oil and gas， are summarized. Afterwards， three types of groundwater pollutants caused by shale oil and gas exploitation， which are organic contaminants， heavy metals， and radioactive material， are discussed， and the characteristics of groundwater contamination are expounded. Finally， the prospect of groundwater pollution research in the exploitation of shale oil and gas is proposed from the perspectives of technological improvement and waste treatment.

Abstract:Aimed at the micro-flow servo control requirements of fuel metering system and thrust vector system of small aircraft such as un-manned aerial vehicle， tactical missile and regional civil aviation， the size constraint and design analysis of key structures such as eccentric ball pair transmission interface and non-full-circle throttle valve port of rotary direct-drive servo valve is conducted. The optimization analysis of important parameters such as throttle valve port width， ball pair eccentricity， and driving motor moment of inertia is performed， and the optimization interval of servo valve structure design is given. In addition， a double closed-loop control method for motor angle and current is proposed. The measured results of amplitude-frequency response are consistent with the theoretical analysis， and the high frequency response above 200 Hz meets the actual requirements. The double closed-loop control method greatly reduces the response overshoot of servo valve and improves the stability.

Abstract:The effects of jet equivalence ratio， jet velocity， and co-flow velocity on the ignition characteristics of methane/air premixed jet were investigated on a controllable thermal-atmosphere combustion experimental system. According to the experimental law， the optimization suggestions for the lean-burn control strategy of natural gas engines were proposed to reduce the occurrence of the misfire. The results show that the lean limit of methane/air premixed jet decreases and the rich limit increases as co-flow temperature rises， which is consistent with the distribution of ignition limits of most hydrocarbon fuel premixes. Besides， there are different critical equivalence ratios at different jet velocities and co-flow velocities， below which the ignition temperature decreases sharply with the increase of jet equivalence ratio. Moreover， at a lower jet equivalence ratio （0.20~0.62）， the improvement in jet velocity can reduce the ignition temperature and optimize the ignition characteristics.

Abstract:Document-level relation extraction aims to extract the relations between multiple entity pairs from a document， a task characterized by high complexity. This paper proposes a method for document-level relation extraction based on attention semantic enhancement to address challenges such as handling multiple entities， capturing relationship correlations， and dealing with imbalanced relationship distributions within documents. The method proposed facilitates the inference of relationships between entity pairs. Specifically， the data encoding module enhances the encoding strategy by incorporating additional entity information， capturing semantic features of the document through the encoding network， and generating an entity pair matrix. Subsequently， a U-Net network employing an attention gating mechanism is devised to capture local information and aggregate global information from entity pair matrices， thereby achieving semantic enhancement. Finally， this paper introduces an adaptive focal loss function to mitigate imbalanced relationship distributions. The Att-DocuNet model proposed is evaluated on four publicly available document-level relation extraction datasets （DocRED， CDR， GDA， and DWIE）， yielding promising experimental results.