Pile foundation underpinning technology is suitable for the strict requirements of the engineering deformation.Through the construction impact on statically indeterminate bridge analysis,in order to grasp the deformation characteristics and construction control requirements,the effective active underpinning design and construction scheme was formulated.Through dynamic monitoring of the whole construction process,this paper verified the validity of the design scheme,which ensured the smooth implementation of the safety of the bridge and engineering.

This paper introduced the equipment and technological innovation(ETI) status in urban rail transit construction of Beijing in the past few years and prospected the ETI in the new round,and then elaborated several aspects of ETI such as the proprietary intellectual property rights,and the comprehensive and thorough application of RAMS insurance system so as to be better adapted to the high-efficiency running of rail transit,allocation of equipment in a network pattern,resource sharing,low-carbon development and the development of passenger-oriented information technology,etc.The paper pointed out that pursuing equipment and technology innovation should be an inevitable direction of the development of rail transportation.

Due to its higher strength,better seismic behavior and faster construction,the structural system of concrete filled steel tubes has been widely used in some significant buildings around the world.The composite action of the steel tube and concrete fill is ensured through the load transfer from steel girders to concrete fill.Even natural bond is often the most economical connection detail;bond capacity is substantially underestimated in countries' codes due to the poor understanding on the bond mechanism.This paper introduces the evolution of the provisions on bond capacity in the Specification for Structural Steel Buildings compiled by American Institute of Steel Construction(AISC).The equation is then elaborated in terms of nominal bond strength and effective bond area involved in bond capacity.Comparing the loading mechanism in the bond interfaces between actual connections and push-out and push-off specimens,connection tests are then proposed to derive the bond strength for modification of the design equation of bond capacity.

By analyzing the application,the model of construction and the technical scheme of existing Video Monitoring System for Urban Transit in the operational dispatching control,the public security monitoring and prevention,it was proposed the scheme to integrate the Specialized Video Monitoring System and Public Video Monitoring System with digital monitoring.Meanwhile through the optimization for practical application of networking solutions and the use of hardware devices,the utilization rate of hardware was promoted to save resources and expense.

In air conditioning system water chillers consume the largest part of energy,thus their efficiency and energy-saving capability become the key to the energy-saving requirements of air conditioning system.This article details the program and control strategy of the chiller control system for a certain line of Beijing subway system,showing that the use of system control is an effective technical means for the energy saving of water chiller.System control can automatically adjust,monitor and manage the air conditioning system to keep the whole system in the best working conditions with lowest energy consumption.

Because of small foundation excavation precipitation,pipeline densely covered on the outside of supporting structure and busy traffic,there isn't dewatering well sites and drilling holes is hard in boulder formation and tight schedule.A new composite pile formation dewatering method is proposed which 1meter diameter supporting piles are drilled by hydraulic casing rotator machine.The piles body is extended with the survey report and filter material is filled in the bottom of piles to form water-absorbing area and an assistant reinforcing cage contains a pump and a filter tube which is welded to the supporting pile' reinforcing stage.Water pipeline and wire are protected in the PVC casing which is along the reinforcing stage up to the ground.In the top of the water-absorbing area,sand is filled to separate the prepared constructing supporting pile.Calculations show that the settlement of single pile caused by dewatering is 0.12mm,when dewatering depth is 3m in a supporting pileless than 10% of the total settlement of the pile.The application of the technology reduces the construction cost and obtains economic benefit.

This paper presents an appropriate representation of the damping behavior of vertical structures with upper steel and lower concrete components(S/RC structure).Two types of models are selected theoretically for the damping behavior of S/RC frames,which include an equivalent damping ratio model based on the dissipated energy of Modal Strain Energy(MSE) and a damping matrix model directly assembled by Rayleigh damping matrices for steel and concrete components.A 12-story S/RC frame and a 12-story RC frame are then designed and tested on the shaking table.Based on these tests,two expressions for measuring the damping behavior for the steel and the concrete component within the S/RC frame are derived,and the expressions are employed to form the damping expression for the S/RC frame in accordance with both of the damping models,respectively.Comparing the damping behavior represented by the two models with that identified in the shaking table tests for the S/RC frame,the damping models are assessed both in frequency domain and in time domain.The conclusions are therefore obtained based on theoretical analyses and experimental evaluation.The first model on assembled Rayleigh damping is not applicable to conventional modal analyses due to its non-proportional characteristics.The second damping model is formed on equivalence of the dissipated MSE of structure which embodies the essence of damping.In comparison with the test results,the second model gives better predictions on the damping behavior of the S/RC frame in both domains than the first damping model.In addition,complex modal analyses are used to predict seismic responses of the S/RC frame to exclude the errors due to non-proportional damping in conventional modal analyses.

Engineering groundwater treatment using vacuum technology had been widely used in Beijing subway construction But the settlement calculation method of vacuum dewatering was not sufficient.In this paper,the settlement caused by vacuum was calculated by solving half-space elasticity mechanics problem using displacement method.The whole settlement of the soil surface was worked out by adding the settlement caused by phreatic aquifer and confined aquifer dewatering to the settlement caused by vacuum.A field experiment in the Anding Road to Beitucheng Road of Beijing subway was carried out,and the vacuum degree,water level,ground settlement and layered settlement of soil in different distance and depth were monitored and analyzed.The theoretical analysis and experiment data both proved that the ground settlement caused by vacuum pressure was little,with a value of 0.69 mm caused by vacuum pressure and 2.5 mm of total settlement in field experiment.Therefore,the ground settlement caused by vacuum pressure can be neglected when conducting the vacuum dewatering project under similar geological condition.

According to the security risk characteristics of urban rail transit,the implementation of security risk management during the construction period and the preparatory stage in Beijing metro Line 9 are introduced in terms of its technology and management.The related engineering experience is also summarized and reviewed,with suggestions to further strengthen security risk management in new metro construction proposed.

The joint stiffness coefficient of shield segment is a direct influence factor which affects the correctness of shield tunnel design.By establishing a 3D discontinuous model of shield tunnel segment and bending bolts and setting up a rational contact model of joints,the influence of the joint stiffness coefficient can be eliminated..This paper studies the stress and the deformation of shield tunnel segments under the actual loads.The results show that the opening of joints on top and bottom of tunnel oriented toward inside,and the opening of joints on two sides of tunnel oriented toward outside.Because block assembly form was used and the connecting bolt elements between segments were installed,the entire stiffness of segment ring was changed and non-uniform wavy chart appeared near segment joints.Relative to routine method model,the axial force of 3D discontinuous model has obviously been magnified near joints,and the biggest positive bending moment of 3D discontinuous model is bigger.The biggest negative bending moments of both models are similar.The finding can be used as reference for the design of shield tunnel segment.

By studying the development and changes of the ratio of motor cars and trailers in a train,this paper analyzes the dynamic braking performance on different configurations of motor cars and trailers,expounds the wheel-rail adhesion force,the rescuing performance and the cost of whole life cycle,points out the debates that new metro operators should adopt more than 66%the ratio of motor cars and trailers in a six-car train,this ratio of motor cars and trailers depends on many factors,including railway line conditions and operational requirements.On the ratio of motor cars and trailers in a train,the guideline should be made according to different conditions rather than only taking a part for the whole.

In order to keep the safety construction TBM tunneling and avoid surface settlement and failure accidents at the TBM Portal areas,This paper carries out studies on how to determine the length of longitudinal reinforcement scopes and establish a new stability model for sandy stratum for the portal areas.It analyzes and summarizes the limitations of existed theoretical models.It refines some existing conclusions.It further presents a new load equivalent and sliding failure models based on strength and stability theories.The new theoretical models can better reflect the mechanical characteristics and deformation modes of actual cases and have a good stratum adaptability.Meanwhile,in order to certify its rationality of improved strength model,the two strength models have been put into use for calculating one actual engineering stratum reinforcement of TBM portal areas.Sensitivity analysis on the main influence factors of existed and new improved models have also been made.The conclusions are: when the diameter of shield tunnel is small,the deviation of calculation results of existed and the new models are small.But as the diameter of shield tunnel is continuously increasing,the deviation of existed model is bigger,which may cause serious accidents if the existing models are applied into actual engineering.So,for large diameter shield tunnel engineering,especially when the diameter is lager than 10meters,the new improved model will be better for designing and quantifying the longitudinal reinforcement scopes.It has the big significant for engineering construction.The load equivalent model presented in this paper gives a new analyzing and computing method for studying load asymmetric problem based on strength theory.It also provides a good reference for similar problems.

The author researches the influence of water-cement ratio,retarding component,and water-reducing hardening-accelerating component on compressive strength of repairing concrete and fluidity of concrete mixture with variance analysis and multiple comparison methods.Compressive strength variation of repairing concrete is discussed by regression analysis method.The author summarizes the compressive strength formulae of 1h,2h and 4h and provides the amount of cement,retarding component,and water-reducing hardening-accelerating component for repairing concrete 1h strength of 30MPa,and 2h strength of 40MPa.The maintenance problem of repairing concrete is discussed.

This paper discusses initial-stage fire entity experiment in the subway station with test fire by lighting shredded paper,cotton rope and polyurethane plastic.Simulation of air conditioning and ventilation condition in the subway station is conducted to study and analyze the responsivity of point-type fire detectors when they are installed in different upper and lower positions in a hollow grille ceiling type subway station,and the responsivity of linear infrared beam smoke detectors to different types of fire sources so as to provide data support and design basis for the selection and set-up of fire detectors in a hollow grille ceiling type subway station.

Field detecting experiments of early fire produced by scrap paper,smoldering cotton ropes and urethane foams on subway platform were conducted to study the effects of piston wind on smoke movement and the applicability and setting position of spot detectors.The applicability of two types of spot fire detectors under simulated operating and night stoppage conditions were compared and analyzed.At the same time,for the subway stations with grid ceilings,the performance of spot detectors installed above and under the ceiling were analyzed and studied.The results show that the train piston wind influences smoke rising and diffusing movement,especially the smoldering fires,but open flame smoke could reach the medium plate fast through the gaps of ceiling grid.Under the subway operating condition,the smoke and heat combination detectors perform unsatisfactorily,the alarm time and alarm numbers for spot smoke detectors in different space all change compared with those under stoppage condition.On subway platforms with grid ceilings,spot smoke detectors should be set both under the media plate and under the grid ceiling during operating periods.

In this paper,the characteristics of the natural vibration of this type of bridge are discussed firstly through the dynamic field-test of Pengxihe Bridge under environmental load.Then,the characteristics of the natural vibration of Pengxihe are calculated with the structure analysis software-ANSYS.Compared with the calculated results and the test results,it shows that the FEM model in the paper is credible.The vibratory characteristics of the structure are also tested under a traveling truck and a truck with obstacle and a braking truck.The result shows that the vibratory characteristics of the structure are in good working order.

According to the geological characteristic in Beijing,construction risk of metro shield is described based on machine,construction technique and surrounding environment.Specific measures of safety management and risk prevention are put forward.

With the application of ballastless tracks with a speed of 350 km/h,Wuhan-Guangzhou passenger line,through theoretical analysis and experiments based on reference to common rail and subway grounding technology,has adopted integrated grounding technology such as electrification,electricity,communication,signal,track,and so on.According to the transmission characteristics and the needs of the track ciruit,all these are aiming to guarantee the safety,reliability,stability of the power supply system,communication system and track system.The actual monitoring and the post-operational validation prove that the integrated grounding technology can ensure the normal operation of the whole system.The necessity of its application was described in ballastless tracks and the specific measures,which can provide a reference for the actual integrated grounding construction of ballastless tracks in passanger line.

This paper discusses the environmental risk management in urban rail transit construction in terms of technical,information and economic strategies,pointing out that risk distinguishing,risk pre-controlling and risk supervising are the three phases of risk technical management so as to further standardize the process of environment investigation and evaluation.In terms of the information strategy,the necessity of establishing risk control center and conducting theory research is advanced.For the economic strategy,the concept of risk management cost and profit is advanced and the new thoughts for avoiding environmental risk are highlighted.