Seismic performance analysis and design suggestion for frame buildings with cast-in-place staircases

Many staircases in reinforced concrete （RC） frame structures suffered severe damage during the Wenchuan earthquake. Elastic analyses for 18 RC structure models with and without staircases are conducted and compared to study the influence of the staircase on the stiffness, displacements and internal forces of the structures. To capture the yielding development and damage mechanism of frame structures, elasto-plastic analysis is carried out for one of the 18 models. Based on the features observed in the analyses, a new type of staircase design i.e., isolating them from the master structure to eliminate the effect of K-type struts, is proposed and discussed. It is concluded that the proposed method of staircase isolation is effective and feasible for engineering design, and does not significantly increase the construction cost.

Thermal performance of cast-in-place piles with artificial ground freezing in permafrost regions

During the construction of cast-in-place piles in warm permafrost,the heat carried by concrete and the cement hydration reaction can cause strong thermal disturbance to the surrounding permafrost.Since the bearing capacity of the pile is quite small before the full freeze-back,the quick refreezing of the native soils surrounding the cast-in-place pile has become the focus of the infrastructure construction in permafrost.To solve this problem,this paper innovatively puts forward the application of the artificial ground freezing(AGF)method at the end of the curing period of cast-in-place piles in permafrost.A field test on the AGF was conducted at the Beiluhe Observation and Research Station of Frozen Soil Engineering and Environment(34°51.2'N,92°56.4'E)in the Qinghai Tibet Plateau(QTP),and then a 3-D numerical model was established to investigate the thermal performance of piles using AGF under different engineering conditions.Additionally,the long-term thermal performance of piles after the completion of AGF under different conditions was estimated.Field experiment results demonstrate that AGF is an effective method to reduce the refreezing time of the soil surrounding the piles constructed in permafrost terrain,with the ability to reduce the pile-soil interface temperatures to below the natural ground temperature within 3 days.Numerical results further prove that AGF still has a good cooling effect even under unfavorable engineering conditions such as high pouring temperature,large pile diameter,and large pile length.Consequently,the application of this method is meaningful to save the subsequent latency time and solve the problem of thermal disturbance in pile construction in permafrost.The research results are highly relevant for the spread of AGF technology and the rapid building of pile foundations in permafrost.

Refreezing of cast-in-place piles under various engineering conditions

In the construction of the Qinghai-Tibet Power Transmission Line （QTPTL）, cast-in-place piles （CIPPs） are widely applied in areas with unfavorable geological conditions. The thermal regime around piles in permafrost regions greatly affects the stability of the towers as well as the operation of the QTPTL. The casting of piles will markedly affect the thermal regime of the surrounding permafrost because of the casting temperature and the hydration heat of cement. Based on the typical geological and engineering conditions along the QTPTL, thermal disturbance ofa CIPP to surrounding permafrost under different casting seasons, pile depths, and casting temperatures were simulated. The results show that the casting season （summer versus winter） can influence the refreezing process of CIPPs, within the first 6 m of pile depth. Sixty days after being cast, CIPPs greater than 6 m in depth can be frozen regardless of which season they were cast, and the foundation could be reffozen after a cold season. Comparing the refreezing characteristics of CIPPs cast in different seasons also showed that, without considering the ground surface conditions, warm seasons are more suitable for casting piles. With the increase of pile depth, the thermal effect of a CIPP on the surrounding soil mainly expands vertically, while the lateral heat disturbance changes little. Deeper, longer CIPPs have better stability. The casting temperature clearly affects the thermal disturbance, and the radius of the melting circle increases with rising casting temperature. The optimal casting temperature is between 2 ℃ and 9 ℃.

Physical modeling of behaviors of cast-in-place concrete piled raft compared to free-standing pile group in sand

Similar to free-standing pile groups, piled raft foundations are conventionally designed in which the piles carry the total load of structure and the raft bearing capacity is not taken into account. Numerous studies indicated that this method is too conservative. Only when the pile cap is elevated from the ground level,the raft bearing contribution can be neglected. In a piled raft foundation, pileesoileraft interaction is complicated. Although several numerical studies have been carried out to analyze the behaviors of piled raft foundations, very few experimental studies are reported in the literature. The available laboratory studies mainly focused on steel piles. The present study aims to compare the behaviors of piled raft foundations with free-standing pile groups in sand, using laboratory physical models. Cast-in-place concrete piles and concrete raft are used for the tests. The tests are conducted on single pile, single pile in pile group, unpiled raft, free-standing pile group and piled raft foundation. We examine the effects of the number of piles, the pile installation method and the interaction between different components of foundation. The results indicate that the ultimate bearing capacity of the piled raft foundation is considerably higher than that of the free-standing pile group with the same number of piles. With installation of the single pile in the group, the pile bearing capacity and stiffness increase. Installation of the piles beneath the raft decreases the bearing capacity of the raft. When the raft bearing capacity is not included in the design process, the allowable bearing capacity of the piled raft is underestimated by more than 200%. This deviation intensifies with increasing spacing of the piles.

Field observation of the thermal disturbance and freezeback processes of cast-in-place pile foundations in warm permafrost regions

The bearing capacity of pile foundations is affected by the temperature of the frozen soil around pile foundations.The construction process and the hydration heat of cast-in-place(CIP)pile foundations affect the thermal stability of permafrost.In this paper,temperature data from inside multiple CIP piles,borehole observations of ground thermal status adjacent to the foundations and local weather stations were monitored in warm permafrost regions to study the thermal influence process of CIP pile foundations.The following conclusions are drawn from the field observation data.(1)The early temperature change process of different CIP piles is different,and the differences gradually diminish over time.(2)The initial concrete temperature is linearly related with the air temperature,net radiation and wind speed within 1 h before the completion of concrete pouring;the contributions of the air temperature,net radiation,and wind speed to the initial concrete temperature are 51.9%,20.3%and 27.9%,respectively.(3)The outer boundary of the thermal disturbance annulus is approximately 2 m away from the pile center.It took more than 224 days for the soil around the CIP piles to return to the natural permafrost temperature at the study site.

Improving the Seismic Performance of Staircases in Building Structures with a Novel Isolator

A staircase provides the main escape way from a building in an emergency.Unfortunately,it may suffer severe damages or even collapse during an earthquake.For improving the seismic performance of staircases,this paper proposes an innovative staircase isolator with the features of lightweight,costeffective and ease of construction and replacement,which is formed by suitable engineering plastic shims between rubber layers.A connection construction scheme is also proposed for the isolated staircase.Systematic performance tests have been carried out to characterize the isolator in terms of mechanic behavior and ultimate states.The test results show that mechanical properties of the proposed staircase isolator are excellent and suitable for staircase in building structure.In order to investigate the influence of staircase on building structural responses,time history analyses of a typical building structure without staircase(WS),with fixed staircase(FS)and with isolated staircase(IS)are conducted and compared within the environment of SAP2000.Results show that staircase isolation can effectively eliminate the diagonal bracing effect of staircase slab and make structural components uniformly stressed.When the novel isolator is employed for staircase in a building structure,there is no vulnerable position in staircase and the performance of staircase in building structure can be greatly enhanced.

Field study of plastic tube cast-in-place concrete pile

The compositions, technical principles and construction equipments of a new piling method used for ground improvement plastic tube cast-in-place concrete pile were introduced. The results from static load tests on single piles with different forms of pile shoes and on their composite foundations were analyzed. The distribution patterns of axial force, shaft friction and toe resistance were studied based on the measurements taken from buried strain gauges. From the point of engineering application, the pile has merits in convenient quality control, high bearing capacity and reliable quality, showing higher reasonability, advancement and suitability than other ground improvement methods. The pile can be adopted properly to take place of ordinary ground improvement method, achieving greater economical and social benefits.

Design and construction of high and large span cast-in-place reinforced concrete cantilever flowering frame beam

The high and large span cast-in-place reinforced concrete cantilever structure of the office building of some court, which is located I-steel at the cantilever and used steel pipe scaffold as the support, has guaranteed the frame body and structure security by the frame body calculating, on-site test and reasonable construction order.

A Prelude Staircase to a Type V Intermittency in Two—Dimensional Discontinuous Maps

A sequence of periodic attractors has been observed in a two-dimensional discontinuous map, which canbe considered as a model of impact oscillator. The so-called 'transfer number', which is defined as the mean numberof transfer from non-impact state to impact state per iteration, is locked onto a lot of rational values to form a curveconsisting of many steps. Our numerical investigation confirms that every step is confined by conditions created by thecollision between the periodic orbit and the discontinuous boundary of the system. After the last collision the systemshows a chaotic motion with intermittent characteristics. Therefore the staircase can be addressed as a 'prelude staircaseto type V intermittency'. The similar phenomenon has also been observed in a model of electric circuit. These resultsof our study suggest that this kind of staircases is common in two (or even higher) dimensional discontinuous maps.

Non-linear Invertible Maps that Preserve Staircase Subalgebras

Let g be the general linear Lie algebra consisting of all n x n matrices over a field F and with the usual bracket operation {x, y} =xy - yx. An invertible map φ ： g →g is said to preserve staircase subalgebras if it maps every staircase subalgebra to some staircase subalgebra of the same dimension. In this paper, we devote to giving an explicit description on the invertible maps on g that preserve staircase subalgebras.

Adaptability of Conservative Staircase Scheme for Live Videos

Existing broadcasting schemes provide services for the stored videos. The basic approach in these schemes is to divide the video into segments and organize them over the channels for proper transmission. Some schemes use segments as a basic unit, whereas the others require segments to be further divided into subsegments. In a scheme, the number of segments/subsegments depends upon the bandwidth allocated to the video by the video server. For constructing segments, the video length should be known. If it is unknown, then the segments cannot be constructed and hence the scheme cannot be applied to provide the video services. This is an important issue especially in live broadcasting applications wherein the ending time of the video is unknown, for example, cricket match. In this paper, we propose a mechanism for the conservative staircase scheme so that it can support live video broadcasting.

Quantum Conductance Staircase of Edge Hole Channels in Silicon Quantum Wells

We present the findings for the quantum conductance staircase of holes that is caused by the edge channels in the ultra-shallow p-type silicon quantum well (Si-QW), 2 nm, confined by the δ-barriers heavily doped with boron on the n-type Si (100) surface. This longitudinal quantum conductance staircase, Gxx, is revealed by the voltage applied to the Hall contacts, Vxy, to a maximum of 4e2/h. In addition to the standard plateau, 2e2/h, the variations of the Vxy voltage appear to exhibit the fractional forms of the quantum conductance staircase with the plateaus and steps that bring into correlation respectively with the odd and even fractional values.

Asymptotically Necessary and Sufficient Quadratic Stability Conditions of T-S Fuzzy Systems Using Staircase Membership Function and Basic Inequality

Asymptotically necessary and sufficient quadratic stability conditions of Takagi-Sugeno (T-S) fuzzy systems are obtained by utilizing staircase membership functions and a basic inequality. The information of the membership functions is incorporated in the stability analysis by approximating the original continuous membership functions with staircase membership functions. The stability of the T-S fuzzy systems was investigated based on a quadratic Lyapunov function. The asymptotically necessary and sufficient stability conditions in terms of linear matrix inequalities were derived using a basic inequality. A fuzzy controller was also designed based on the stability results. The derivation process of the stability results is straightforward and easy to understand. Case studies confirmed the validity of the obtained stability results.

Nuclear-Magnetic-Resonance Properties of the Staircase Kagome Antiferromagnet PbCu3TeO7

We report the first nuclear magnetic resonance （NMR） study on single crystals of staircase Kagome antiferromagnet PbCu3Te07 （TN1 -36K）. A Curie constant θ -140K is obtained by a Curie Weiss fit to the high- temperature Knight shift of 125 Te. The hyperfine coupling constant is estimated to be 125Ahf = -67 kOe/#B, and a strong interlayer coupling among staircase Kagome planes is suggested with such a large hyperfine coupling, according to the lattice structure. The 63,65Cu NMR spectra are found by the zero-field （ZF） NMR at T = 2 K, and the internal hyperfine fields are estimated to be 10.3 T and 9.6 T, for Cu（1） and Cu（2） sites, respectively, in the lattice. A second type of ZF NMFt signal with a large rf enhancement is also seen after field-cycling through a high magnetic field.

User Preference Survey on Staircase Rotation

Staircase is an important means of vertical transportation. Staircase design exerts a great influence on the aesthetics, transportation efficiency, user comfort and experience level. In this paper, a survey on the staircase rotation preference was conducted, based on the environment behavior studies. Different user frequencies of a pair of scissors stairs in the 2nd teaching building of North China University of Technology were analyzed. The psychological effect was evaluated and quantified, and the user preference on the two staircase rotations was then withdrawn. The survey found that the type of staircase with clockwise upstairs was much more preferred （78%） than the other staircase rotation anti-clock upstairs. Considering different genders, the female shows a 66% higher preference inclination of this type of staircase rotation than the male. To improve the transportation efficiency of the staircase in case of fire, the result of this paper can be very constructive for the evacuation staircase rotation choice for the high-rise buildings.

Computerised Gate Firing Control for 17-Level MLI using Staircase PWM

A basic 7-level MLI topology is developed and the same is extended to the 9-level then further increased to 17-levels.The developed structure minimizes the component’s count and size to draw out the system economy.Despite the various advantages of MLIs,efficiency and reliability play a major role since the usage of components is higher for getting a low Total Harmonics Distortion(THD)value.This becomes a major challenge incorporated in boosting the efficiency without affecting the THD value.Various parametric observations are done and realized for the designed 9-level and 17-level MLI,being the Total Standing Voltage(TSV),efficiency,cost function per level count,and power loss.The respective parameters are compared with several existing and modern circuits and found to be effective in their performance.A novel single-phase 17-level asymmetrical Multi-Level Inverter(MLI)topology is developed to reduce the number of overall components.The developed topology generates 17-levels by using unequal DC sources.The developed MLI is proved under various tests con-ducted experimentally for the various loads like resistive,inductive,and combinational loads.A detailed comparison is done on several factors and represented graphically represented.Further,the proposed design provides a less TSV value is 6 V_(dc),efficiency is 94.21%and cost factor per level CF/L value for both values ofαis 2.01 and 2.05 and devices count with a low THD value 41.4%with respectively.

新型建筑楼梯钢模板施工技术研究

楼梯是每个工程刚需构件,其是由混凝土浇灌而成,而浇灌前需根据设计中楼梯的尺寸搭设各种模板,待混凝土浇灌完成并凝固后,拆开模板,即得到所需楼梯。传统的楼梯木模板在支设中由于支设流程复杂,支设模板偏位变形率高,其主要表现在楼梯踏步几何尺寸偏差大、观感质量差等。无论是支设过程还是拆卸过程,用时均较长,施工效率低下,故不易进行施工进度控制和质量控制。楼梯钢模板的施工质量决定楼梯混凝土成形质量,故将新型的楼梯钢模板施工技术应用在实际项目中,最终取得了较好的经济效益及社会效益。

杭州电竞中心基础及地下室设计

杭州电竞中心项目采用桩基、筏板基础等多种基础形式,采用YJK软件进行多种基础形式之间的沉降差计算,并提出多种基础形式运用于同一建筑物时的加强措施。对于三面覆土、一面开敞地下室的不平衡水、土压力问题,利用桩基抵抗不平衡水、土压力,并提出相应的加强措施。将抗拔桩、无粘结预应力抗浮锚杆以及排水泄压多种抗浮技术应用于本工程,基于连通器原理的排水泄压主动抗浮技术的应用,大大减少抗浮锚杆的数量,获得了良好的经济效应;对于工程中多向框架梁与斜柱的连接节点,采用圆形柱帽有效约束各个方向相交的框架梁,并采用ABAQUS进行了有限元分析来模拟其受力性能,证明连接节点的可靠性。最后介绍了下沉庭院大跨度无柱弧形楼梯的设计,并对其进行舒适度验算,结果满足规范要求。

基于Pyrosim的楼梯间火灾烟气数值模拟与分析

为分析老旧高层住宅楼在火灾场景下烟气的发展过程,以某高层住宅建筑为研究背景,通过Pyrosim软件建立火灾仿真模型,分析火灾场景下烟气在楼梯间的蔓延规律并通过开启不同楼梯间高度的窗户分析其对烟气排放的效果,对比不同楼梯间高度开窗烟气排放仿真模拟结果。结果发现:在烟气充满整个楼梯间的条件下,7层楼梯间开窗180 s时可达到3层楼梯间清晰;27层楼梯间开窗180 s时可达到6层楼梯间清晰;7层和27层楼梯间同时开窗180 s时可达到7层楼梯间清晰;在楼梯间最高处开窗180 s时可达到8层楼梯间清晰。综合楼梯间开窗排烟效果可知,楼梯间最高处开窗>中和面上、下同时开窗>中和面以上开窗>中和面以下开窗。

基于激光雷达的多层楼梯检测和建模方法

移动机器人在多层建筑进行自主导航时,需要具备楼梯检测和建模能力。然而,目前楼梯检测和建模主要面向单层直楼梯,对具有回转结构的多层楼梯适用性差,且场景中存在的动态点云会影响建模精度。针对以上问题,提出了一种基于激光雷达的多层楼梯检测和建模方法。首先,构建了轻量化的2.5D点云滤波器,高效滤除动态和噪声点云;其次,提出了一种基于主成分分析的台阶分类方法,实现了对单个及具有回转结构的复杂多层楼梯的鲁棒台阶检测;同时,设计了一种基于区域分割的台阶尺寸估计方法,提高了楼梯模型的构建精度;此外,提出了一种基于多阈值判断的楼梯模型追踪方法,实现了实时楼梯检测和快速动态建模;最后,分别使用Tang数据集和四足机器人在室内外多重场景下采集的点云数据进行试验验证。结果表明,提出的算法在室内外场景下,能够对单层及具有回转结构的多层楼梯进行动态检测和建模,其中台阶尺寸的估计精度在1 cm以内,计算量降低了51.23%。