Development of deformable connection for earthquake‐resistant buildings to reduce floor accelerations and force responses

This paper presents the development of a deformable connection that is used to connect each floor system of the flexible gravity load resisting system (GLRS) with the stiff lateral force resisting system (LFRS) of an earthquake‐resistant building. It is shown that the deformable connection acts as a seismic response modification device, which limits the lateral forces transferred from each floor to the LFRS and allows relative motion between the GLRS and LFRS. In addition, the floor accelerations and the LFRS story shears related to the higher‐mode responses are reduced. The dispersion of peak responses is also significantly reduced. Numerical simulations of the earthquake response of a 12‐story reinforced concrete shear wall example building with deformable connections are used to define an approximate feasible design space for the deformable connection. The responses of the example building model with deformable connections and the example building model with rigid‐elastic connections are compared. Two configurations of the deformable connection are studied. In one configuration, a buckling restrained brace is used as the limited‐strength load‐carrying hysteretic component of the deformable connection, and in the other configuration, a friction device is used. Low damping laminated rubber bearings are used in both configurations to ensure the out‐of‐plane stability of the LFRS and to provide post‐elastic stiffness to the deformable connection. Important experimental results from full‐scale tests of the deformable connections are presented and used to calibrate numerical models of the connections. Copyright © 2016 John Wiley & Sons, Ltd.     

Intensity of Rubber Planted and Population Urbanization: A Spatial Econometric Analysis Based on Panel Data of Cities and Counties in Hainan Island

Population urbanization is the core of new urbanization in China and is an important task in the long term. Based on mediation effect models, spatial panel data econometric models, and coupling coordination models, this study attempts to identify the direct and indirect effects of the proportion of rubber-planted areas and the indications of population urbanization using panel data of counties on Hainan Island, explaining the mechanism. The results show that rubber plantations dominated by state-owned farms weakly impacted farmers' income in 1992-2002 (first phrase), and the effects became positive in the period of smallholding expansions from 2003 to 2013 (second phrase) at a statistically significant level of 10%. However, the effects became negative between 2013 and 2020 (third phrase) due to the continuously low prices of natural rubber compared to the second phrase; the regions with higher share of rubber plantations had less local fiscal revenues per capita—especially in the third phrase—mainly because of the short industrial chain of rubber in producing regions. Shares of rubber-planted areas in the city or county (defined as rubber-planted intensity, RPI) were negatively related to proportions of staff in the non-private sector (SNS) and nonrural employees (NRE) compared to people with jobs and census registered population urbanization rates (PUR). The reversed connections between RPI and NRE became weaker over time; a 10-percentage point increase in PRI might have led to a 10.3-percentage point decrease in NRE in the first phrase, but it reduced to 3.3 percentage points in NRE with no statistical significance in the third phrase. Conversely, the negative correlation of RPI with SNS and PUR became stronger from the first to third phrase; the farmers' income and local fiscal revenue could ease the negative relationships between RPI and SNS or NRE, but they turned to enhance the relation of RPI with PUR in the second and third phrase. The evidence from Moran's I and Geary's c indices proved the existence of obvious spatial correlations in the distribution of natural rubber and farmers' income and indicated that GDP per capita and other variables are also spatially related. The estimated spatial panel data models with adjacent, geographical and economical distance matrices indicated that the direct influences of RPI on SNS, NRE, and PUR were almost negative in all phrases, but the spillover and total effects can be positive in some situations, such as in the second phrase with adjacent and geographical distance matrices of PUR; this means that an increase in rubber-planted areas may promote nonfarm job market of adjacent regions mainly due to rural labor mobility. The coupling coordination degrees between the intensity of rubber planted and population urbanization of Haikou and Sanya reach 0.96 and 0.87, respectively, in the second and third phrases—much higher than those of other regions. Compared to the first phrase, the margin of increases in the degrees of coupling coordination in the second and third phrases are reducing from the east to west in Hainan Island. The key routes to mitigate the negative links are to improve labor productivity and extend the industrial chain of natural rubber along with the nonfarm job creation, and Hainan's population urbanization should consider many other possible angles across the island. © The Author(s) 2023.     

贺庄橡胶坝工程建设综合后评价

构建了橡胶坝工程建设综合后评价的指标体系,建立了合理的后评价数学模型,并以贺庄橡胶坝工程建设为实例,应用多目标模糊层次分析法对其进行了综合后评价.该方法将定性指标数量化及各项指标的无量纲化,使定性指标和定量指标有机的结合起来,从而更准确、直观地反映橡胶坝建设项目的成功度,对实际的橡胶坝工程后评价有一定实用价值.     

温度对铅芯橡胶支座隔震桥梁抗震性能的影响分析

为了研究温度对铅芯橡胶支座（LRB）隔震桥梁抗震性能的影响,以一座七跨连续梁桥为对象,考虑LRB在夏季和冬季不同温度下的力学特性,利用OpenSees对桥梁抗震性能进行研究。通过对不同温度下墩柱、支座及桥梁系统的地震易损性分析,获得了温度对铅芯橡胶支座隔震桥梁抗震性能的影响。结果表明:（1）与夏季相比,冬季低温降低了桥墩的延性及LRB的剪切变形和耗能能力,使地震作用时墩顶位移和支座变形均小于夏季,降低了LRB的减震效果;（2）冬季低温增大了地震作用时桥墩、LRB及桥梁系统在各个破坏状态的损伤概率,在中等及严重破坏状态时损伤概率相比夏季分别增加了8%和15%。在寒冷地区进行LRB隔震桥梁设计时,应考虑低温导致的LRB隔震效果降低对桥梁抗震性能的影响。     

基于汶川地震的LRB与RB隔震连续梁桥地震响应对比研究

为了研究铅芯橡胶支座(LRB)和板式橡胶支座(RB)对连续梁桥地震响应及隔震效果的影响,分别采用Bouc - Wen滞回恢复力模型模拟LRB的力-位移非线性特性,采用直线型恢复力模型模拟RB的本构关系,通过结构离散建立了非隔震、LRB隔震和RB隔震3种连续梁桥的有限元计算模型,运用四阶显式Runge - Kutta迭代法和Newmark时间积分法联合求解增量形式的全桥动力微分方程,并结合算例对3种连续梁桥有限元计算模型分别输入汶川地震波进行非线性时程对比分析.结果表明:LRB在控制梁体与支座位移,降低结构加速度和墩、台底内力响应方面均比RB的效果要显著;采用RB隔震后,梁体与支座的位移响应均较大,在桥梁隔震设计时要予以充分重视.     

Effects of rainfall on the spatial distribution of the throughfall kinetic energy on a small scale in a rubber plantation

This study evaluated the spatial distribution of the throughfall kinetic energy (TKE) on a small scale in a rubber plantation. The experiments used Tübingen splash cups with natural rainfall. The results indicate that the leaf area index did not significantly affect the TKE during the foliated season. There was no significant correlation between the TKE and the distance from the trunk. However, the lateral translocation of the throughfall in the canopy significantly affected the spatial distribution of the TKE, and high TKE points appeared in the middle and at the edge of the canopy. The results also show that the spatial distribution of the volume-specific TKE values was similar in different rainfall and rainfall intensity groups. The variogram of the spatial variability demonstrates that the TKE exhibited a strong spatial autocorrelation. We confirm that the rainfall redistribution is important for the spatial distribution of the TKE in a rubber plantation.     

西昌市某高层剪力墙结构隔震设计与分析

针对西昌市某高层钢筋混凝土剪力墙结构进行了橡胶支座隔震设计和抗震性能分析。西昌市抗震设防烈度为9度,历史上曾发生过7.5级地震。该工程场址地质构造较复杂,东侧区域有一条隐伏断层,属则木河断裂带次生断层。则木河断裂带是川西主要发震断裂带之一,至今仍是一条活动较强烈的大断裂。按照《建筑抗震设计规范》(2016版)要求,取近场影响系数1.5,以提高结构的安全度;选取Ⅱ类场地5条天然地震波和2条人工模拟地震波,共计七条符合规范要求的地震波;基于SAP2000软件对结构进行了隔震设计,中震作用下结构层间剪力和倾覆弯矩减震系数最大值为0.24,比非隔震结构地震响应减小显著,罕遇地震下隔震支座的面压、水平位移能够满足规范要求。采用ABAQUS对结构进行了罕遇地震动力弹塑性时程分析,结果表明结构能够满足"大震不倒"的抗震设防目标。     

TRENDS IN THE URBANIZATION PROCESS

Matthiessen, Christian Wichmann: Trends in the urbanization process. The Copenhagen case. Geografisk Tidsskrift 80: 98–101. Copenhagen, June 1980.

Within the framework of the international comparative research project (Cost of Urban Growth) new trends in urban development have recently been observed. The object of this article is to discuss the trends and give impirical evidence on Danish data.     

高分辨率影像的橡胶林分布信息提取

目的 为了准确快速地获取高分辨率影像中橡胶林的分布信息,设计了一种基于纹理特征和多光谱特征的信息提取方法。方法选取合适的植被指数,将多光谱和植被指数的影像进行地统计半方差分析,获得最佳纹理提取窗口并实现各种纹理信息的提取,将纹理信息和光谱信息一起作为参考特征构建地物的分类规则并用C5决策树分类算法实现。选取某高分辨率遥感影像区域对该方法进行验证,橡胶树林提取的生产者精度为81.00%,提取用户精度为82.65%,总精度为83.50%,Kappa系数为0.78。与其他方法分类结果对比表明,本文方法是一种有效的橡胶林提取方法。     

橡胶集料风积沙混凝土柱抗震性能试验研究

为研究橡胶集料风积沙混凝土柱的抗震性能,制作了4根相同尺寸的混凝土柱试件,其中包括普通混凝土柱、风积沙混凝土柱、橡胶集料混凝土柱和橡胶集料风积沙混凝土柱。通过低周反复荷载试验,分析各试件的破坏现象、滞回曲线、骨架曲线、刚度退化和延性等抗震性能指标。在试验的基础上,根据能量耗散原理建立累积损伤评价模型,并对结构进行了累积损伤分析。研究结果表明:10%橡胶集料的掺入能够改善混凝土柱的变形能力,但混凝土柱的承载力有所降低;30%风积沙的掺入可以改善混凝土柱的抗震性能;橡胶集料风积沙混凝土柱具有较好的滞回性能,且耗能能力和延性性能明显高于其余试件,柱的抗震性能得到提高;通过累积损伤分析表明:适量掺入橡胶集料和风积沙的可以有效减缓试件的损伤,且该累积损伤模型能够较好的反映出各试件的损伤程度。