Abstract:Monolithic precast concrete utility tunnel structure generally does not set the axillary angle. In order to study the failure mechanism, bearing capacity and crack condition of the structure of the utility tunnel without axillary angle, a static concentric load test was performed on the full-scale model of a multicellular utility tunnel with and without axillary angle. The results showed that the crack width of the long span roof of the utility tunnel reached a short time limit of 0.133 mm for the control condition，and the roof finally showed shearing damage. The finite element model was established and the test results were used to verify the model. Then, the nonlinear finite element method was used to analyze the utility tunnel model，and the results show that the mechanical properties of the section model under both uniform load and concentric load are basically the same. According to the segmental model test and nonlinear finite element analysis, the design control conditions for the utility tunnel structure with and without axillary angle are the maximum crack width, but the ultimate damage is the shearing failure of the roof. The structure performance of the utility tunnel without axillary angle is close to that of the utility tunnel with axillary angle by properly increasing the longitudinal bar ratio of the roof.

Abstract:Reinforced concrete shear walls are the primary lateral-load carrying elements in the high-buildings. Its stiffness property has significant influence on the internal force distribution of structures. Reinforced concrete shear walls were set up by MSC.Marc and validated by comparing with lots of test data. A parametric study was conducted on reinforced concrete shear wall to study effective stiffness influenced by the shear-span-to-wall-length ratio, axial compression ratio, yield strength of longitudinal bars in wall boundaries, longitudinal reinforcement content in wall boundaries and concrete strength. The results show that axial compression ratio is the main factor. A simplified formula to evaluate the effective stiffness of reinforced concrete shear wall was proposed on the basis of the parametric study. The results obtained from the simplified formula is in good agreement with those from experiments. It proves that the simplified formula is reasonable and reliable and can be used for reference.

Abstract:The dynamic response of the remaining structures under sudden failure of a corner column in a reinforced concrete (RC) frame structure was studied. The finite element model of ABAQUS / Explicit was established based on the loss of a corner column tested by Qian K. The finite element model took into account the strain rate effect of reinforced concrete materials and simulated the actual loading process. The simulation results were in good agreement with the field-test dynamic response curves and failure modes, which simulated the whole process of sudden removal of a corner column. Based on the finite element model, the influence of corner column failure time and lateral restraint stiffness on the dynamic response of the structure was analyzed. The results show that prolonging the failure time and increasing the lateral horizontal restraint stiffness can effectively improve the collapse resistance of the structure.

Abstract:A Controlled Rocking Reinforced Concrete Frame with Column-end-hinge joints (CR-RCFC) is a new type of resilient structure. Firstly, the configuration of CR-RCFC joint was introduced. The ABAQUS software was used to establish the finite element model of the conventional RC frame (RCF) and CR-RCFC. The rationality of the finite element model of CR-RCFC was verified by shaking table test results. Ten ground motions were selected based on earthquake platform and seismic information and input into CR-RCFC model to simulate the natural frequencies and dynamic time-history responses of the structures with different joint stiffness ratios. Finally, the inter-story drift amplification coefficient α and the base earthquake-reduction coefficient β were defined, and the displacement responses and inter-story shear responses were selected as the control parameters for selecting the joint stiffness. Through the elasto-plastic time-history analysis, the peak inter-story drifts and peak inter-story shear forces of the structure under different ground motions were compared to analyze the effects of joint stiffness degradation on the coefficients α and β, and reasonable range of joint stiffness ratio was obtained.

Abstract:Steel fiber reinforced green concrete was applied to the composite slab in order to promote the application of green ecological materials in the composite slab. The flexural behavior of the steel fiber reinforced green concrete composite slab with different structural forms were studied. Full-scale comparative test of six steel fiber reinforced green concrete composite slabs and two ordinary concrete composite slabs were carried out. The characteristic parameters, such as failure mode, load-deflection curves, load-rebar strain curves, and load-concrete strain curves, were obtained. Further, the failure mechanism, deformation characteristics, and crack distribution were comparatively analyzed. The results show that the flexural processes of eight specimens are similar, which experienced elastic stage, elastic-plastic stage and failure stage. All specimens are bonded well on the connection interface，without any break-off and other phenomenon but with good cooperative work performance. Meanwhile, different structure forms of prefabricated base slabs have significant influence on the flexural behavior of the composite slab. It is noted that steel bar truss with ribs improves the flexural behavior of the composite slab significantly. In addition, the cracking strength and ultimate load-carrying capacity of the composite slab were affected by the effects of different structural forms and different material on flexural behaviour of prefabricated base slab.

Abstract:In order to study whether the standing seam roof system installed on a flexible roof structure has the ability to adapt to the large deformation of the flexible roof structure and whether panel details of the roofing system can ensure the water tightness under large deformation, taking the roof structure of the swimming stadium in Suzhou Industrial Park Sports Center as an example, a 6.6m×6.6m test unit was used to design the full-scale water tightness test of the metal roofing system under large deformation. Through numerical analysis, stress and deformation distribution of the roofing system was explored under large deformations in the flexible roof structure. A refined finite element model was also established to evaluate the water tightness of key details in the standing seam roof panels. The test and analysis verified that the standing seam roof system had the ability to adapt to the large deformation of the flexible roof structure, the calculated angle between standing seams was only 2.18°，and water tightness can be ensured at the same time.

Abstract:In view of the current calibration problems in a lack of unified calibration method and difficulty to sample expansion, the distribution parameter calibration method for probability damage model and sample expansion method based on Bayesian statistical method were proposed. The typical damage model was considered, and damage indexes of each limit state were calibrated by hysteretic test results of conventional reinforced concrete beam-column components. The impact of the damage model on the performance evaluation was examined from single component damage to overall structural component loss in four RC frame structures with different layers in 8 intensity region. The results show that the sample expansion method proposed can balance the prior information and sampling information, and the calibration process proposed can facilitate the expansion of the following sample. The prominent damage state can be recognized by the calibrated damage models; the displacement damage model is suggested under small and moderate earthquakes as its convenience for computation and the earthquake average losses are basically the same, and the Park-Ang damage model is suggested under rare earthquakes for prudence.

Abstract:Short bridge piers are widely used in high-speed railway. These piers have less reinforcement ratio and lower shear-span ratio than bridge piers for conventional high way. Furthermore, their section sizes in longitudinal and transverse directions are quite different. To compare the seismic performance of bridge pier between the longitudinal and transverse directions, 4 pier models were designed based on the model similarity theory. The prototypes of pier models were determined from the typical piers with ended rectangular cross-sections in high-speed railway, and the height of piers were 8 m and 16 m. After low cyclic tests were carried out in the longitudinal and transverse directions, the seismic performance of piers in these two directions, including the hysteretic curves, skeleton curves and failure modes，was obtained. The test results showed that the model with a shear span ratio of 1.35 failed due to typical shear failure, and the ductility was poor. When the shear span ratio of pier in the transverse bridge is 2.13, a few bending-shear cracks appear at the bottom of the pier, but the pier still fails in bending. The failure modes of pier in the longitudinal bridge are all bending failure, which as the same to the existing test results. When the seismic design of bridge pier with lower shear span ratio is carried, the shear capacity of the transverse pier under earthquake loading should be guaranteed to avoid the shear failure.

Abstract:In order to investigate the effect of aerodynamic interaction between vehicles and a bridge on the driving safety of vehicles on a bridge, the Taihong Yangtze River Bridge of Chongqing in China was taken as an example, and the driving safety of vehicles and dynamic responses of vehicles and the bridge under strong wind were investigated for the two typical types of vehicles——a van and a car. Firstly, based on the wind-vehicle-bridge coupling analysis system, the vertical, pitching and rolling accelerations of the vehicles, and the lateral acceleration of the bridge were calculated with and without consideration of the aerodynamic interference between the vehicles and bridge. Then, these acceleration responses of the vehicles and bridge were applied to the local accident analysis program built by MATLAB. The sideslip displacement and the reaction force ratio of each wheel of the vehicles were calculated. The accidents of the vehicles were assessed by comparing the calculated responses of the vehicles with the accident criteria. Further, the accident critical wind speeds of the vehicles at different traveling speeds were obtained by gradually increasing the traveling speed and wind speed, and the curves of the accident critical wind speed versus the traveling speed for the two types of vehicles with and without consideration of the aerodynamic interference were plotted. The results show that the aerodynamic interference between the vehicles and the bridge has a significant influence on the driving safety of vehicles on the bridge. The assess results are relatively conservative if the aerodynamic interference between the vehicles and bridge is not considered. In addition, the aerodynamic interference also affects the vehicle accident type. This paper can provide a reasonable theoretical reference and data support for the operation safety and scientific management of long-span bridges under strong wind weather conditions.

Abstract:This article studied the rule of flow separation in low-rise building with flat roof through the combination of experimental method and numerical simulation, when the wind speed is 7 m/s and the turbulence is less than 10%. The results indicated that the mean wind pressure coefficient and extreme wind pressure coefficient of the roof decreased when applying along-wind plasma actuation; The mean wind pressure coefficient and extreme wind pressure coefficient increased in the front portion of the roof, and decreased in the back portion of the roof when applying headwind plasma actuation; The mean wind pressure coefficient and extreme wind pressure coefficient increased in the front portion of the roof and decreased in the back portion of the roof when applying the plasma actuation from middle to the both sides; The mean wind pressure coefficient decreased in the front portion of the roof and in the back portion, and the mean wind pressure coefficient and extreme wind pressure coefficient increased in the middle portion of the roof when applying the plasma actuation from the both sides to middle. The results of this paper can provide reference for wind resistance studies of building.

Abstract:In order to study the spatial correlation of the along-wind fluctuating wind load of lattice tower, two segmental models of a typical lattice tower were selected, and two high frequency force balance technologies were employed. The time histories of the base shear and bending moment for the segmental models considering different horizontal and vertical distances between them were synchronously obtained in the wind tunnel test. Based on the extensive analysis of the obtained data, the coherence function formulas of the along-wind fluctuating wind load on the lattice tower model were obtained. The results show that the coherence functions of the along-wind fluctuating wind load on the lattice tower are related to the frequency, horizontal distance, and vertical distance. There is a certain deviation between the deduced coherence functions obtained by this experiment and the existing coherence functions of longitudinal wind speed or wind load of high-rise buildings. Finally, the least square method was used to fit an empirical formula of the coherence functions of the along-wind fluctuating wind load on the lattice tower. The experimental results are in good agreement with the empirical formula, which can provide a useful reference for the calculation of the wind load and wind-induced response of lattice towers.

Abstract:To clarify the mechanism of wake interference effect on the downstream cylinder, large eddy simulation（LES） method was adopted. The flow around two static staggered circular cylinders was studied at a high Reynolds number of Re=1.4×105, and the ratio of center-to-center pitch （P） to the diameter of the cylinder（D） ranges from P/D=1.5~4. The aerodynamic coefficients, mean pressure distributions, and flow field of the downstream cylinder were discussed along with the changing of incidence angle. The relationship between aerodynamic forces and flow characteristics was analyzed based on the time-averaged wall shear stress and flow structures. The results show that the reasons for the negative drag force of the downstream cylinder at small pitch ratio（P/D<3） lie in two factors, i.e., a pair of recirculation zone with opposite direction for the tandem configuration and the high-speed gap flow for the staggered arrangement with small incidence angles. At small pitch ratios（P/D=1.5~3），the downstream cylinder is subjected to remarkable mean lift coefficient（inner lift），which is caused by the shift of the stagnation point, high-speed gap flow, and separation bubble. At the moderate pitch ratios（P/D=3~4），the mean lift（outer lift） of the downstream cylinder is affected by the shift of the stagnation point and separation point in the gap side.

Abstract:Based on the data obtained from a tower and a local meteorological station, the wind properties at the Jiangdihe Bridge site, located at a deep-cut valley，were investigated. According to statistical data processing, the mean wind properties, wind directions, turbulence integral scales, as well as wind spectra were obtained. The results show that the deep canyon terrain in which the bridge is located plays roles in locking the wind direction and accelerating the wind speed, and shows obvious influence on the turbulence characteristics. The relationship between the turbulent intensity and mean wind speed was obtained by fitting with inverse example functions, resulting in good fitting effect and high wind speed close to the standard value. The vertical turbulence intensities are much higher than those values specified in the China wind-resistant design specification for highway bridges. The wind spectra from the measured wind are quite different from the Kaimal spectrum, but in good agreement with the von Karman spectrum. The wind spectra of the vertical wind fluctuations are obviously larger than the Panofsky wind spectrum, but close to the von Karman spectrum. The measured across-wind spectra are quite close to both the Panofsky spectrum and the von Karman spectrum.

Abstract:In order to study the thermal environment of residences and the thermal comfort sensation of the elderly in the rural area of western Hunan in winter，tests and questionnaire surveys were performed in 50 local residences among the elderly who are over 65 years old in January 2018. The results show that temperature in this area in winter is low：the average temperature in living rooms，bedrooms and bathrooms are 8.3 ℃, 8.5 ℃ and 7.1 ℃, respectively，and indoor temperature of stilted building, wooden structure house and brick building rises successively. The average temperature in morning and evening are 7.5 ℃ and 8.5 ℃ respectively，corresponding with 70% and 40% of the subjects having cold feelings when they are indoors，and the proportion of the subjects who feel cold in the bathroom is the highest. Residents' adaptive behaviours in winter include adding clothes and using warm barrels, and the average thermal resistance of winter clothing for the elderly is 1.60 clo. As area heating devices，warm bareels can not improve the overall indoor temperature significantly, but they can greatly improve the thermal comfort sensation of the elderly. Using the Adaptive Predicted Mean Vote（APMV） Model, the adaptive coefficient of the elderly in this area in winter is calculated to be -0.26, and the comfort temperature range is 16.7~27.1 ℃.

Abstract:Accurate prediction of occupancy in buildings can significantly improve the performance of building energy simulation and further facilitate building design and system operation. Considering the temporal dependency of occupancy, Hidden Markov Model has been widely used to effectively predict occupancy behavior. However, the traditional Hidden Markov model that uses time-independent transition probability matrix is difficult to accurately describe the dynamic variation of occupancy as well as its correlation with environmental parameters. Such a model would greatly reduce occupancy prediction accuracy. To address this issue, an inhomogeneous Hidden Markov Model based on state transition was proposed. In this model, time-dependent transition probability matrices were calculated to capture the temporal dependency of occupancy at different time periods. Meanwhile, probability distribution of environmental parameters was calculated based on state transition instead of state only, aiming at rationally describing the correlation between occupancy and environmental parameters. The method was applied to predict the occupancy of a Belgian office. The results demonstrated that the effectiveness of the proposed approach and the prediction accuracy were improved significantly.

Abstract:Based on the strategy of the rise of central China, a case study on the background and necessity of the planning and construction of utility tunnels within the inland benchmarking free trade area (FTA), i.e., Xiangyang FTA, was carried out. A primary plan for the urban roads using utility tunnels was proposed by analysing the urban space, road system, municipal pipeline, high-intensity exploitation and urban landscape, etc., of Xiangyang City. Then, fuzzy mathematical analysis was conducted to evaluate the suitability for constructing the utility tunnels within those preliminarily selected roads. Sixteen roads were finally determined for tunnel construction where the three-level tunnel system composed of trunk-branch-cable lines within the FTA was suggested. Through this case study, it was found that the planning of utility tunnels should be aligned with the urban master planning and the harmonization of the road planning, where the urban space, traffic conditions, and municipal pipeline distributions need to be thoroughly considered. Dynamic adjustment of the planning layout of utility tunnels can be then made based on the updating of each planning.