Plastic zone distribution laws and its types of surrounding rock in large-span roadway

In order to study the distribution laws and types of plastic zone of surrounding rock in large-span roadway, we analyzed the distribution laws with different spans and lateral pressures using FLAC3D numerical calcu- lation software. Based on the roadway support difficulty and distribution laws of the plastic zone of sur- rounding rock, we defined the large-span roadway and classified the types of large-span rectangular roadways. As a result, the distribution laws of the plastic zone on surrounding rock in a rectangular roadway with different spans and lateral pressures were obtained. The results show that the area of the plastic zone on surrounding rock increased with the increase of the spans and lateral pressures, and the plastic zone was symmetrical to the center line of roadway. At λ=0.5, 1.0, 1.5, and 2.0, the plastic zone presented ＂addle- shape＂ distribution, ＂ellipse＂ distribution, ＂thin and high＂ distribution and ＂inverse trapezium＂ distribu- tion, respectively. In addition, we classified the roadways into four types according to the different lateral pressures and spans, including small-span, moderate-span, large-span and extreme-large-span roadways.

Development of a new type of foam concrete and its application on stability analysis of large-span soft rock tunnel

The long-term stability of large-span soft rock tunnel is influenced greatly by the creep effect of surrounding rock.The development of a new type of foam concrete which has the property of high compressibility and low ductility was introduced.And it was made as filling material of reserved deformation layer between the first lining and the second lining used in large-span soft rock tunnel.The effect of the new type of foam concrete was simulated as filling material of reserved deformation layer using numerical simulation.Through the comparison with the common large-span soft rock tunnel,the vault settlement and surrounding convergence are reduced by about 61% and 45%,respectively,after creep of 100 a.And in the second lining,the plastic zone reduces apparently and the maximum equivalent plastic strain decreases relatively.So,it can be found that the application of the new type of foam concrete as the filling material of reserved deformation layer can relieve the excessive force in second lining induced by rock creep,reduce its deformation and improve the stability of tunnel.

In Situ Experiments on Supporting Load Effect of Large-span Deep Tunnels in Hard Rock

A section of the Nanliang high speed railway tunnel on Shijiazhuang-Taiyuan high-speed passenger railway line in China was instrumented and studied for its mechanical properties and performances. The cross section for the tunnel was300 m2and is classified as the largest cross section for railway tunnels in China. Through in situ experimental studies, mechanistic properties of the tunnel were identified, including the surrounding rock pressure, convergences along tunnel perimeter and safety of primary support and lining structure.Based on the field measured data, the surrounding rock pressure demand for large-span deep tunnel in hard rock is recommended as double peak type in the vertical direction and fold line type was recommended for horizontal pressure. The results suggested that Promojiyfakonov's theory was most close to the monitored value. Specific recommendations were also generated for the use of bolts in tunnel structures.Numerical simulation was used to evaluate the safety of the tunnel and it confirmed that the current design can satisfy the requirement of the current code.

Seismic response of large-span spatial structures under multi-support and multidimensional excitations including rotational components

To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.

Characteristics of wind pressure pulse on large-span flat roofs

The wind pressure pulse events, among the most important characteristics of wind pressure fluctuations on large-span flat roofs, were investigated by wind tunnel tests in this paper. Incorporating the formation mechanism of wind pressure pulse events, the peak over threshold method was employed to study properties of this kind of events. The event duration time, the energy contribution, the number of the pulse events, and the distribution of average peak pressure were calculated. Probability density functions of some typical samples in separation region were also given. Results show that the non-Gaussian roof pressure is strong in the flow separation region owing to the wind pressure pulse events. Evaluations of the extreme peak pressures, which can be determined by the peak over threshold method effectively, are important to the design of building cladding.

Research on Construction Control Technology of Large-Span and Small Clear Distance Underpass High-Voltage Line Tunnel

Hanping tunnel is a control project of national highway 310 Dahejia to Qingshui highway project.It needs to cross a 330kV high-voltage transmission line under the condition of small clear distance,which requires high construction requirements.In view of the difficulties such as shallow buried depth of tunnel and small clear distance between tunnel and tower of high-voltage line,multiple excavation blasting method is adopted,and smooth blasting,charge quantity control and damping hole setting are comprehensively used to reduce the impact on the tower and structure of high-voltage line.In order to ensure the smooth progress of the project,the large-scale finite element analysis software is used to simulate the whole excavation project.The influence of the full-section method and the middle partition wall method(CD method)on the surrounding rock and the high-voltage electric tower is compared.It is found that the CD method can effectively control the displacement of the surrounding rock and the tower on it and the uneven settlement.

Distribution characteristics and the evolution law of excavation damage zone in the large-span transition section of high-speed railway tunnel based on microseismic monitoring

Purpose–The microseismic monitoring technique has great advantages on identifying the location,extent and the mechanism of damage process occurring in rock mass.This study aims to analyze distribution characteristics and the evolution law of excavation damage zone of surrounding rock based on microseismic monitoring data.Design/methodology/approach–In situ test using microseismic monitoring technique is carried out in the large-span transition tunnel of Badaling Great Wall Station of Beijing-Zhangjiakou high-speed railway.An intelligent microseismic monitoring system is built with symmetry monitoring point layout both on the mountain surface and inside the tunnel to achieve three-dimensional and all-round monitoring results.Findings–Microseismic events can be divided into high density area,medium density area and low density area according to the density distribution of microseismic events.The positions where the cumulative distribution frequencies of microseismic events are 60 and 80%are identified as the boundaries between high and medium density areas and between medium and low density areas,respectively.The high density area of microseismic events is regarded as the high excavation damage zone of surrounding rock,which is affected by the grade of surrounding rock and the span of tunnel.The prediction formulas for the depth of high excavation damage zone of surrounding rock at different tunnel positions are given considering these two parameters.The scale of the average moment magnitude parameters of microseismic events is adopted to describe the damage degree of surrounding rock.The strong positive correlation and multistage characteristics between the depth of excavation damage zone and deformation of surrounding rock are revealed.Based on the depth of high excavation damage zone of surrounding rock,the prestressed anchor cable(rod)is designed,and the safety of anchor cable(rod)design parameters is verified by the deformation results of surrounding rock.Originality/value–The research provides a new method to predict the surrounding rock damage zone of large-span tunnel and also provides a reference basis for design parameters of prestressed anchor cable(rod).

阿尔瓦·阿尔托的景观语言

芬兰建筑大师阿尔瓦·阿尔托在处理建筑与环境的对话和建筑向自然的延伸中,形成了独特的景观设计语言,如室外剧场、折线形台阶或堤状草坡等。这些设计语汇的运用对欧洲园林设计师产生了重要影响。借用语言学的词汇和句法概念,归纳和解析其景观设计的语言及运用。

定县农民戏剧试验及对中国农村文化建设的启示

1932-1937年熊佛西领导的河北定县农民戏剧试验是一次重要的乡村文化建设尝试,它的时代背景为中国20世纪30年代农村社会经济凋敝、农民积贫积弱的现状,以及当时的中国文化界存在一种"向下看"的大众化潮流。定县农民戏剧是中华平民教育促进会晏阳初所领导的"定县乡村建设试验"的一个有机组成部分,试验过程中产生了不少经典的农民戏剧文本,并极大地调动了定县农民大规模参加话剧演出的热情,在试验中首次出现农民自发建造剧场。从对中国农村文化建设的角度看,定县戏剧试验在文化切入途径、跨越文化障碍、"树人"等方面取得丰硕经验。

“永恒之都”与“废墟之美”--从城市美学视角重释罗马角斗场的文化意义

罗马角斗场是罗马艺术宝库中最奇特的瑰宝,它是罗马人充分吸收希腊和希伯来建筑艺术之精华而创造的人间奇迹。在其问世之初,它就远不只是帝国首都的一座地标建筑;在其坍塌之后,它也绝不只是一处供人凭吊的历史遗迹。神奇的角斗场,铭刻着一个时代的辉煌和耻辱,也记载着一个民族的悲喜与兴衰,它不仅是"伟大罗马"震撼人心的狂欢之所,也是"永恒之都"孤标傲世的绝美圣墟。作为人类城市审美文化史上堪称不朽的典范之作,就像雅典的帕特农神庙代表着古希腊建筑艺术的最高成就一样,大角斗场代表着古罗马建筑艺术的最高成就。

Grouping response method for equivalent static wind loads based on a modified LRC method

Wind loading is one of the most important loads for controlling the design of large-span roof structures. Equivalent static wind loads, which can generally aim at determining a specific response, are widely used by structural designers. A method for equivalent static wind loads applicable to multi-responses is proposed in this paper. A modified load- response-correlation （LRC） method corresponding to a particular peak response is presented, and the similarity algorithm implemented for the group response is described. The main idea of the algorithm is that two responses can be put into one group if the value of one response is close to that of the other response, when the structure is subjected to equivalent static wind loads aiming at the other response. Based on the modified LRC, the grouping response method is put forward to construct equivalent static wind loading. This technique can simultaneously reproduce peak responses for some grouped responses. To verify its computational accuracy, the method is applied to an actual large-span roof structure. Calculation results show that when the similarity of responses in the same group is high, equivalent static wind loads with high accuracy and reasonable magnitude of equivalent static wind distribution can be achieved.

武汉某学校阶梯教室的结构设计

通过对武汉某学校2层阶梯教室的结构设计设计过程的介绍,阐述了该类结构的合理布置和后张预应力梁的设计方法,并提出了预应力梁的一些细部工程处理方法和监测方法。

Dynamic Reliability Assessment of Heavy Vehicle Crossing a Prototype Bridge Deck by Using Simulation Technology and Health Monitoring Data

Overloads of vehicle may cause damage to bridge structures,and how to assess the safety influence of heavy vehicles crossing the prototype bridge is one of the challenges.In this report,using a large amount of monitored data collected from the structural health monitoring system(SHMS)in service of the prototype bridge,of which the bridge type is large-span continuous rigid frame bridge,and adopting FEM simulation technique,we suggested a dynamic reliability assessment method in the report to assess the safety impact of heavy vehicles on the prototype bridge during operation.In the first place,by using the health monitored strain data,of which the selected monitored data time range is before the opening of traffic,the quasi dynamic reliability around the embedded sensor with no traffic load effects is obtained;then,with FEM technology,the FEM simulation model of one main span of the prototype bridge is built by using ANSYS software and then the dynamic reliability when the heavy vehicles crossing the prototype bridge corresponding to the middle-span web plate is comprehensively analyzed and discussed.At last,assuming that the main beam stress state change is in the stage of approximately linear elasticity under heavy vehicle loads impact,the authors got the impact level of heavy vehicles effects on the dynamic reliability of the prototype bridge.Based on a large number of field measured data,the dynamic reliability value calculated by our proposed methodology is more accurate.The method suggested in the paper can do good for not only the traffic management but also the damage analysis of bridges.

Seismic performance evaluation of large-span offshore cable-stayed bridges under non-uniform earthquake excitations including strain rate effect

This paper presents a novel and precise seismic performance evaluation method for large-span offshore cable-stayed(LSOCS)bridge by considering the strain rate effect of RC materials and the spatial variation effect of seafloor seismic motions. Threedimensional finite element(FE) model of a LSOCS bridge located in the southeast coast of China is constructed in the ABAQUS platform. The non-uniform ground motions at the offshore site beneath the bridge are stochastically simulated and used as seismic inputs. Moreover, a subroutine for considering the rate-dependent properties of RC materials in a fiber-based beamcolumn element model is developed to account for the strain rate effect of RC materials in the nonlinear time-history analysis.The numerical results indicate that seismic responses and fragilities of the LSOCS bridge are both considerably affected by the non-uniform seafloor seismic motions and strain rate effect. The seismic performance evaluation approach presented in this paper can provide vital support for earthquake resistant design of LSOCS bridges.

Green Construction of National Speed Skating Oval

1 Background As the basic principle of the world economy,environment,and social development,sustainable development is the focus of the international community today.In the Olympic Agenda 2020 published by the International Olympic Committee(IOC),sustainable development was officially listed as one of the core concepts of the Olympic Games.Since the beginning of the bid,the concept of ctathlete-centered,sustainable and economical”was proposed,which was highly consistent with the idea of the Olympic Agenda 2020.To implement the concept of holding“green”Olympic Games and meet the sustainability requirements of the IOC,the Organizing Committee of Beijing Winter Olympic Games issued a series of documents related to the sustainability of sports venues such as Sustainability Policies for 2022 Beijing Winter Olympic Games and Winter Paralympic Games,and strived to realize the sustainable development of sports venues in the whole life cycle of planning and design stage,construction stage,operation stage,and post-game utilization.

镇江新区文化馆结构设计

镇江新区文化馆地上两层,地下一层,属于大跨度圆形剧场。地上结构采用钢框架结构,屋顶采用平面交叉桁架,地下室采用型钢混凝土结构,楼屋面板采用钢筋桁架楼承板。由于本工程建筑功能需要楼板大开洞,局部设夹层,结构存在扭转不规则、楼板不连续、刚度突变及穿层柱等多项不规则,为特别不规则多层建筑。根据计算分析结果和概念设计方法,对关键、重要构件和薄弱部位做了适当的加强和性能设计,保证结构在地震作用下的延性以及其他各种作用效应下的可靠性。并采用YJK和MIDAS Gen软件进行小震下应力比包络结果设计,保证结构的安全性。对地上钢结构的次梁进行了优化,对其按组合楼盖设计,适当降低了次梁的用钢量,满足了业主对建设成本的控制要求。