武广铁路客运专线东平水道桥三主桁钢桁拱架设的技术创新

东平水道桥为武广客运专线控制性工程,是三主桁钢桁拱。在该桥架设过程中,采用了"三主桁钢桁拱线形控制技术"、"边墩顶落(主墩不起顶)与调索的综合合龙方法"和"双向可调式后锚固"等诸多创新技术,为高效率、高质量地建设武广客运专线提供了可靠的保证。同时也为今后类似桥梁的建设提供了借鉴。

大跨度钢屋架吊装平面外稳定的内力控制方法

大跨度厂房在安装中最经济的方法就是单榀提升就位,此方法存在一个容易忽视的问题就是钢屋架吊装过程中的平面外稳定性。文章通过工程实例,探讨大跨度钢屋架吊装平面外稳定的内力控制方法。

广州明珠湾大桥主桥中跨合龙技术

广州明珠湾大桥主桥为(96+164+436+164+96+60)m中承式钢桁拱桥,采用双层桥面布置,主梁采用N形三主桁钢桁梁结构。主桥采用斜拉扣挂法、拱梁同步架设;中跨合龙时,拱肋与主梁分别采用“多点同步合龙”与“节点拼装合龙”法进行先拱后梁施工,以提高大桥的合龙效率。通过敏感性分析确定该桥采用26号、29号墩顶、落梁为主,竖向、横向、纵向顶拉为辅的合龙措施调整拱肋合龙口空间姿态。该桥中跨合龙施工中,在边跨采用抗倾覆压重设计,以控制大桥悬臂施工阶段由自重产生的倾覆力矩;在26号、29号墩顶支座处布置顶、落梁及纵移装置,以消除合龙口高差与转角位移,实现精准对位;在拱肋与主梁合龙口设置微调装置,以实现钢梁合龙口间距微调;在27号主墩设置顶推装置,使结构整体纵移0.085 m,实现上、下拱肋同步合龙;主梁合龙节点杆件拼装后,利用吊杆与顶拉装置调节高差与合龙口间距,实现大桥无应力精确合龙。

Application of laminated vierendeel truss in high-position transfer story structure

To meet the demands for large space and flexible compartmentation ofbuildings, laminated vierendeel trasses are adopted in high-position transfer story structures.First the bearing characteristics are analyzed, in which reasonable stiffness ratio of the upperchord, middle chord, and lower chord is derived. Then combined with an actual engineering model (1:8similar ratio), the static loading and pseudo-dynamic tests of two models for laminated vierendeeltrass used in transfer story structures are conducted, in which one model adopts reinforcedconcrete, and the other adopts prestressed concrete and shape steel concrete. Seismic behaviors areanalyzed, including inter-story displacement, base shear-displacement skeleton curves, andequivalent viscosity-damping curves. A program is programmed to carry out the elasto-plastic dynamicanalysis, and displacement time-history curves of the two models are derived. The test and analysisresults show that the laminated vierendeel trass with prestressed concrete and shape steel concretehas excellent seismic behaviors. It can solve the disadvantages of laminated vierendeel trussesused in transfer story structures. Finally, some design suggestions are put forward, which can bereferenced by similar engineering.

广州明珠湾大桥主桥总体设计

广州明珠湾大桥主桥为(96+164+436+164+96+60)m中承式钢桁拱桥,采用双层桥面布置。大桥主跨采用结构自平衡体系,无外部推力;主梁采用N形三主桁钢桁梁结构;拱肋、钢桁梁均采用箱形截面,腹杆部分采用工字形截面、部分采用箱形截面,弦杆、腹杆与主桁架之间采用栓焊结合连接方式;桥面板采用正交异性钢桥面板,桥面铺装采用浇筑式沥青混凝土;主跨吊杆采用1670 MPa的镀锌平行钢丝索;主墩深水基础采用钻孔灌注桩基础。采用12000 t级双曲面球型减隔震支座,解决了全桥强震作用下的纵、横向减隔震问题。在主墩与边墩分别设置B型转筒式与C型护舷防撞装置,可有效预防3000 t级船舶失控对大桥的撞击。为提高架梁效率、适应通航水域条件,大桥架设采用拱梁同步施工方案。采用MIDAS Civil软件建立全桥空间有限元模型,对该桥静力、动力、稳定、抗风、抗震性能进行分析,结果表明:主桥最大悬臂施工与运营阶段,抖振响应均能满足规范要求,大桥结构受力性能良好、安全可靠。

广州明珠湾大桥主墩吊箱围堰定位施工技术

广州明珠湾大桥主桥为(96+164+436+164+96+60)m中承式三主桁钢桁拱桥,该桥27号主墩采用25根直径2.5 m钻孔桩基础、高桩承台,承台尺寸56.5 m(横桥向)×17.5 m(顺桥向)×5.5 m(高)、底标高-2.84 m,桥位处于往复流环境下。27号主墩基础采用双壁钢吊箱围堰兼做钻孔平台方案施工。围堰加工后采用气囊法下水,浮运至墩位处定位、下沉、挂桩,在围堰上铺设钢平台作为钻孔平台;然后进行桩基施工,桩基施工后拆除围堰上铺设的平台;最后进行围堰封底、抽水、承台施工。在围堰定位时,采用靠墩+定位船+重锚定位系统进行施工,其中靠墩布置在围堰上游侧,定位船布置在下游侧,重锚布置在大、小里程方向。围堰定位后,其纵、横向最大偏差分别为30 mm、20 mm,倾斜度2‰,满足设计要求。

Experimental research on ultimate bearing capacity of N-joints of grouted square steel tube trusses

Cave-in failure is apt to occur in joints of trusses made of square hollow sections. In order to turn the failure mode into a strength failure mode of joint members, the idea is proposed that the chord of the truss is grouted to increase the cave-in beating capacity of a hollow tube chord. An experiment of eight specimens of N- joints made of grout-filled square steel tubes is performed. Based on the experimental study, the geometrical parameters of specimens are analyzed, and the effects of the confinement index ε, the spacing between the two web members g and the ratio of side length of the vertical web member to that of the chord β on the behavior of specimens are investigated through simulation analysis by simulation analyses, the mechanical properties and the failure an ANSYS program. Based on the test results and modes of this kind of joints are analyzed and the formulae to predict the ultimate bearing capacities corresponding to different failure modes are developed. The ultimate bearing capacity of compressive N-joints is calculated in accordance with the cave-in failure mode of a chord member; the ultimate bearing capacity of tension N-joints is calculated in accordance with the punchingshear failure mode; the ultimate bearing capacity of a chord member is calculated in accordance with the shear failure mode in normal sections.

Train-induced vibration on elevated railway station

Results of in-situ vibration measurement carried out at Tianjin West Elevated Railway Station which has the trains running on the station structure were reported. The main excitation source is the train passing through the station. Vibration measurements were recorded in the vertical direction of the supporting track beam, the platform and the steel truss beam of the waiting hall, as well as in the vertical, longitudinal and transverse directions of the roof arch base of the station. Acceleration time responses were obtained. The maximum value, vibration level and one-third octave band RMS spectra of the measured accelerations were studied. The propagation of vibration in different structural floors was discussed. The influence of train speed, distance to the vibration source and the type of train on the structural vibration were analyzed. Results show that the vibration level increases with the train speed, while it attenuates with the distance to the track. Furthermore, the vibration responses of different structural floors were compared, and it is noted that the vertical vibration of the bottom slab of the platform is most severe and the transverse vibration of the roof arch base is the smallest. The results provide reference on the vibration characteristics and vibration energy distribution of this type of "Train on building frame" system used as an elevated railway station.

Research on stress concentration at tubular joints in concrete filled steel tubular truss arch bridge

In this paper stresses at joints forming by hollow steel tube and concrete filled steel tube （CFST） are calculated, analyzed and compared. It is founded that the stress concentration at joints of CFST is a quite different from that of hollow steel tube. A conclusion can be made that analysis of fatigue at the joints of CFST truss arch bridge can not apply the results developed from analyzing at joints of hollow steel tube in marine structure.

Flexural behaviour of SFRRAC two-way composite slab with different shapes

To promote the application of green renewable materials in concrete composite slabs(CCSs)and study the flexural behavior of CCSs with different shapes,the bending performances of three CCSs with a SFRRAC base plate,one cast-in-site concrete slab of ordinary concrete and one CCS of ordinary concrete by steel bar truss(as recommended in the technical specification for precast concrete structures in Chinese)were compared through experiments.The carrying capacity,flexural behaviour and bi-directional mechanical properties of the specimens were systematically analyzed from the failure modes,load-deflection curves,load-bar strain curves,load-slip curves and crack distributions.Results show that the bending failure process of CCSs with a SFRRAC base plate is similar to that of the cast-in-site concrete slab of ordinary concrete and CCS of ordinary concrete by steel bar truss,as all of them went through the plastic phase,elastic plastic phase and failure phase with fully developed cracks and deflection.No sudden breakage or horizontal cracking of the connecting interface between the base plate and concrete topping was observed.The shape of the base plate has a major impact on the bearing capacity of the CCS with the SFRRAC base plate.When calculating the ultimate bearing capacity with the plastic yield line theory,the influence of the base plate shape on the plastic yield line position should be taken into account.

Bending behaviour of lightweight aggregate concrete-filled steel tube spatial truss beam

A lightweight aggregate concrete-filled steel tube(LACFST) spatial truss beam was tested under bending load. The performance was studied by the analysis of the beam deflection and strains in its chords and webs. According to the test results, several assumptions were made to deduce the bearing capacity calculation method based on the force balance of the whole section. An optimal dimension relationship for the truss beam chords was proposed and verified by finite element analysis. Results show that the LACFST spatial truss beam failed after excessive deflection. The strain distribution agreed with Bernoulli-Euler theoretical prediction. The truss beam flexural bearing capacity calculation results matched test evidence with only a 3% difference between the two. Finite element analyses with different chord dimensions show that the ultimate bearing capacity increases as the chord dimensions increase when the chords have a diameter smaller than optimal one; otherwise, it remains almost unchanged as the chord dimensions increase.

Approach for analyzing the ultimate strength of concrete filled steel tubular arch bridges with stiffening girder

A convenient approach is proposed for analyzing the ultimate load carrying capacity of concrete filled steel tubular (CFST) arch bridge with stiffening girders. A fiber model beam element is specially used to simulate the stiffening girder and CFST arch rib. The geometric nonlinearity, material nonlinearity, influence of the construction process and the contribution of prestressing reinforcement are all taken into consideration. The accuracy of this method is validated by comparing its results with experimental results. Finally, the ultimate strength of an abnormal CFST arch bridge with stiffening girders is investigated and the effect of construction method is discussed. It is concluded that the construction process has little effect on the ultimate strength of the bridge.

Mechanical Analysis and Numerical Simulation for New Type of Dynamic Control Devices

The conventional dynamic control devices,such as fluid viscous damper(VFD)and isolating bearings,are unsuitable for the double-deck cable-stayed bridge due to a lack of sustainability,so it is necessary to introduce some high-tech dynamic control devices to reduce dynamic response for double-deck cable-stayed bridges under earthquakes.A(90+128)m-span double-deck cable-stayed bridge with a steel truss beam is taken as the prototype bridge.A 3D finite element model is built to conduct the nonlinear time-history analysis of different site categories in fortification intensityⅨ(0.40 g)degree area.Two new types of dynamic control devices-cable sliding friction aseismic bearings(CSFABs)and elasticity fluid viscous dampers composite devices(EVFDs)are introduced to reduce the dynamic responses of double-deck cable-stayed bridges with steel truss beam.The parametric optimization design for the damping coefficient C and the elastic stiffness of spring K of EVFDs is conducted.The following conclusions are drawn:(1)The hybrid support system by EVFDs and CSFABs play a good function under both seismic and regular work,especially in eliminating the expansion joints damage;(2)The hybrid support system can reduce the beam-end displacement by 75%and the tower-bottom bending moment by 60%under the longitudinal seismic excitation.In addition,it can reduce the pier-bottom bending moment by at least 45%under transverse seismic and control the relative displacement between the pier and beam within 0.3 m.(3)Assuming the velocity indexα=0.3,the parametric optimization suggests the damping coefficient C as 2000 kN·s·m-1in siteⅠ0,4000kN·s·m-1in siteⅡ,6000 kN·s·m-1in siteⅣ,and the elastic stiffness of spring K as 10000 kN/m in siteⅠ0,50000 kN/m in siteⅡ,and 100000 kN/m in siteⅣ.

Experimental research on mechanical properties of prestressed truss concrete composite beam encased with circular steel tube

Tests of 4 simply supported unbonded prestressed truss concrete composite beams encased with circular steel tube were carried out. It is found that the ratio of the stress increment of the unbonded tendon to that of the tensile steel tube is 0.252 during the using stage,and the average crack space of beams depends on the ratio of the sum of the bottom chord steel tube's outside diameter and the secondary bottom chord steel tube's section area to the effective tensile concrete area. The coefficient of uneven crack distribution is 1.68 and the formula for the calculation of crack width is established. Test results indicate that the ultimate stress increment of unbonded tendon in the beams decreases in linearity with the increase of the composite reinforcement index β0. The pure bending region of beams accords with the plane section assumption from loading to failure. The calculation formula of ultimate stress increment of the unbonded tendon and the method to calculate the bearing capacity of normal section of beams have been presented. Besides,the method to calculate the stiffness of this sort of beams is brought forward as well.

Numerical and Experimental Study of Steel Space Truss with Stamped Connection

Tubular section members made of steel are common in space trusses. There are several types of connections to attach these members. The most popular is the staking end-flattened connection. The reduced cost and the fast assemblage of the truss are among the advantages of the staking end-flattened connection on 3D trusses. However, such connections present disadvantages like eccentricities and stiffness weakening of the tubular members. In this work, based on computer simulations and experimental lab tests on prototypes, small changes on the staking end-flattened connections such as reinforcement and eccentricity correction are evaluated. The results show an increase of 68% for local collapse and 17% for global collapse in the truss load carrying capacity when the suggested changes proposed in this article are used for the staking end-flattened connections.

Application of an acrylic vessel supported by a stainless-steel truss for the JUNO central detector

After the success of the Daya Bay experiment, the Jiangmen Underground Neutrino Observatory （JUNO） was launched to measure neutrino-mass hierarchy and oscillation parameters and to study other neutrino physics. Its central detector is set for antineutrinos from reactors, the Earth, the atmosphere, and the Sun. The main requirements of the central detector are con- tainment of 20 kt of liquid scintillator, as the target mass, and 3% energy resolution. It is about a ball-shape detector of 38.5 m with -75% coverage of PMT on its inner surface. The design of such a huge detector is a big challenge because it must meet the requirements for several different types of physics measurement and possess the feasibility and reliability in its structure and engineering, all at reasonable time and cost. One option for the JUNO central detector is a hyper-scale acrylic ball sub- merged in the water to shield the background. This paper proposes a structural scheme for such an acrylic ball that is supported by a stainless-steel truss, inspired by point-supported glass-curtain walls in civil engineering. The preliminary design of the scheme is completed and verified by finite element （FE） method using ABAQUS. FE analysis shows that the scheme can con- trol the stress level of the acrylic ball within the limit of 5 to 10 MPa, in accordance with the demand of the design objective of the central detector. The scheme is of outstanding global stability and allows various chocces on local connections. We prove that the scheme is of good feasibility and should be a reasonable option for the central detector.

Damage-induced material softening and its effect on seismic performance of steel structures

A numerical approach for simulating the seismic performance of steel truss structures, considering damage-induced material softening, is developed based on a ductile damage constitutive model by applying the backward Euler explicit algorithm. It is implemented in ABAQUS through a user-defined material subroutine, by which damage evolution could be incorporated into the analysis of seismic performance of steel structures. The case study taken up here is the investigation of a steel connection with a reduced beam section(RBS) and a steel frame with such connections. The material softening effect during the failure process is particularly investigated. The results show that material softening in the vulnerable zone has a significant effect on the distribution of stress and strain fields, as well as on the carrying capacity of the steel connection with RBS. Further, material softening is found to have almost negligible effect on the seismic performance of the steel frame in the early stages of the loading process, but has a large effect when the steel frame is about to fail. These findings offer a practical reference for the assessment of seismic structural failure, and help in understanding the damage mechanism of steel structures under seismic loading.