塑性铰区采用FRC柱试验研究及正截面承载力分析

采用简化的纤维增强混凝土应力应变关系,根据截面变形的平截面假定和截面力的平衡方程,推导出塑性铰区采用纤维增强混凝土柱在不同极限状态时的曲率。根据各极限状态点曲率,求得截面上各分布力,对截面形心轴取距,到塑性铰区采用FRC柱的开裂、屈服、峰值和极限点的弯矩表达式。与试验结果对比表明,计算值与试验值吻合较好。     

黄河宁夏灌区覆膜与土壤温湿度的响应对蓖麻生长的影响

本试验针对黄河宁夏灌区的生态气候和生产条件,对蓖麻不同播种时期、不同播种方式下蓖麻出苗期的土壤温度,以及蓖麻的生长发育情况,于田间布设小区精确试验,进行观测与研究。研究结果,地膜覆盖栽培有利于土壤保温增湿,延长了营养生长期和生殖生长期,十分有利于蓖麻增产,从而使蓖麻出苗早、生长快、开花早、结果早、果穗多,蓖麻的穗部特征、产量均优于露地栽培,且全程覆膜优于苗期覆膜优于露地栽培,同时,从不同播种期结果来看,早播比晚播增产明显,覆膜较露地栽培增产显著,平均增幅43.4%,露地栽培的以4月20日播种较为适宜,而覆膜栽培的播期以4月中旬较为适宜。     

施肥和覆膜垄沟种植对旱地红芸豆耗水特征及产量效应的研究

[目的]为了探明在高寒冷凉区芸豆生长的水肥耦合效应,[方法]采用田间试验法,研究了施肥和覆膜垄沟种植对旱地芸豆耗水特征、水分利用效率及产量的影响。[结果]结果表明,在底墒较好,降水丰富的年份,施肥和覆膜垄沟种植的产量与农户模式相比,均有显著提高,单株荚数是其产量提高的关键因素;高肥具有明显的增产和提高水分利用效率的作用,在此基础上的覆膜垄沟种植可有效的减少土壤水分损耗,而显著的提高水分利用效率。[结论]在高寒冷凉区,水分和养分都是作物生长的限制因子,在施肥和覆膜垄沟种植方式下,水肥互作效应显著,能够大大的提高产量和水分利用效率。     

山西省典型地区农用地膜利用现状及残膜污染调查分析

为阐明山西省目前的地膜利用和残膜污染现状,采用问卷调查和样方检测方法,对山西省各市县进行地膜问题的相关统计分析,同时对寿阳大田中的铺膜情况进行实时观测。结果表明:目前全省使用的地膜厚度大多在0.008 mm以下;全省90%以上都使用普通地膜,可降解类地膜很少;地膜覆盖面积居前三位作物分别是:蔬菜、玉米、马铃薯,南部盆地内有部分覆盖冬小麦;地膜使用量最多的市级单位是大同、忻州、临汾;地膜回收率极低,且大都是搁置路头、填埋、焚烧或者直接翻入土壤,残膜在土壤里越来越多,主要集中在0~20 cm土层,若一直沿用目前的地膜覆盖方式,不重视对残膜的回收,很快就会超过国家农田残膜限制标准,抑制作物的生长发育,进而影响产量和质量。本次调研统计分析可为山西省残膜防治提供参考。     

Elasto- plastic Analysis of Pressure Circular Tunnel with Liner

According to the strain nonlinear softening constitutive model having inflexion point after peak stress of practical rock and considering intermediate principal stress, the plastic zone of circular cavern with liner under the condition of uniform pressure is analyzed. The elasto - plastic boundaries both for the lining and surrounding rock are discussed. The stress distribution law is different due to the different position of elastic - plastic boundary. Based on this, different stress formulas are gained. The critical pressure caused by excavation of cavern leading to the yield zone and that caused by inner pressure leading to the yield of the liner and surrounding rock is introduced.     

Analysis of the Double-layer Sub-grade with Rigid Upper Layer and Soft Lower Layer by FEM

The double layer subgrade with rigid upper layer and soft lower layer is common in engineering construction. In this paper, the elastic and elasto-plastic analysis on such subgrade by ANSYS was carried out. According to the calculation results of FEM, the plastic zone of subgrade would appear in the upper layer soil of interface, then, it would be expanded up and down with increase of the load. As for the lower layer soil is relatively soft, the plastic zone is expanding rapidly. Finally, as the plastic zone reaches the bottom and the subgrade in the state of ultimate bearing capacity, the calculation starts to be non-convergent. The results can serve as reference to the engineering designers.     

Ultimate Bearing Capacity of Concrete Two-way Composite Slabs with Precast Concrete Ribbed Panels

New types of precast concrete ribbed panels are developed in order to adapt to the complex loading conditions and different floor spans. Based on the yield line theory, equations for the ultimate bearing capacity and yield patterns of two-way composite slabs of different edge conditions and under uniformly distributed loading are developed, and the simplified formulas for the ultimate moment per unit width are proposed. The plastic limit analyses of two examples on the simple support and the fixed support are conducted, and the calculation results show good agreement with the experimental data.     

A finite difference method simulation for stability of buildingslopes in urban areas

We simulate the stress, displacement and the stability of an urban building under load on the top of a slope during different excavation stages. Our research is based on a perfectly elastic plastic constitutive model and applied the Mohr Coulomb yield cri     

冬种马铃薯新品种‘闽薯1号’高产栽培试验

以 ‘闽薯1号’为试验材料,采用裂区设计,探讨不同品种和栽培方式对冬种马铃薯产量的影响。结果表明：（1）6种不同处理间商品薯产量差异均达极显著水平。其中,以‘闽薯1号’稻草包芯+地膜覆盖栽培的鲜薯产量为39.39 t/hm2,增产44.23%,大中薯率高达95.2%,生育期缩短5天,每公顷可增加纯收入1.66万元,增产增效最为显著。其次是‘闽薯1号’地膜覆盖栽培,‘紫花851’常规栽培处理最低。（2）同一品种不同栽培方式的产量、大中薯率和商品率表现依次为稻草包芯+地膜覆盖>地膜覆盖>常规栽培。（3）同一栽培方式不同品种的产量差异显著,表现依次为‘闽薯1号’>‘紫花851’。稻草包芯+地膜覆盖栽培具有增产增效显著、增温保墒、保水防旱、抑制杂草、减轻病虫害和防霜冻害等优点。马铃薯新品种‘闽薯1号’采用稻草包芯+地膜覆盖配套栽培技术,具有良好的推广应用前景。     

揭膜对花生生长发育、干物质积累和产量的影响

为探讨新疆地区膜下滴灌条件下花生栽培模式,于2015年以高产油用大花生新品种花育36号为试材,利用田间试验与室内分析相结合的方法,研究花前揭膜(UPF)和全生育期覆膜(MPF)2种种植方式对花生生长发育、各器官干物质积累动态变化和荚果产量的影响。结果表明,在UPF和MPF 2种方式下,花育36号的农艺性状、各器官干、鲜质量动态变化以及荚果产量间均存在不显著差异。与MPF种植方式相比,UPF方式有利于增加花生主茎高、侧枝长、分枝数、主茎绿叶数和主茎节数等。同时,UPF前期根茎叶和荚果的鲜质量以及根茎叶各器官的干质量均大于MPF,但荚果的干质量小于MPF,UPF下的荚果减产871.3 kg/hm2,减产率为8.1%。在综合考虑环境保护和花生种植效益的前提下,UPF种植方式是可行的,采用该种植方式不但能够较好的利用地膜前期的正向效应,而且大大提高了残膜回收率并增加花生秸秆的附加值。     

砂土地基上圆形浅基础三维破坏包络面的理论研究

对砂土地基上圆形浅基础在竖向荷载V、水平荷载H及力矩M复合加载条件下的承载力进行了系统的三维有限元分析。在分析中,砂土假定为纯摩擦材料,遵循基于Mohr-Coulomb破坏准则的理想弹塑性本构关系。首先,对圆形浅基础的竖向承载力进行了有限元计算, 并与滑移线解法进行了对比,两种方法所得结果比较吻合。进而探讨了砂土内摩擦角对于基础在V-H、V-M荷载平面与V-H-M三维荷载空间内的破坏包络轨迹的影响。计算结果表明,与不排水情况下软黏土地基上基础破坏包络面相比,砂土地基上圆形浅基础的破坏包络面形状有较大差异, 但V-H和V-M平面内的破坏包络面形状仍具有较好的归一化特性。基于有限元计算结果,建立了圆形浅基础在V-H-M三维荷载空间内的破坏包络面方程, 该方程可用来合理评价复合加载条件下砂土地基上圆形浅基础的整体稳定性。     

地膜覆盖对辣椒地土壤氮素的影响

地膜覆盖在西南地区农业生产中有着广泛的应用,但关于地膜覆盖对土壤养分的研究还比较匮乏,为了揭示地膜覆盖对土壤氮素的影响,于2014 年5—9 月在重庆市北碚区进行了辣椒种植的田间试验,对地膜覆盖条件下辣椒地的土壤水热条件、氮素以及辣椒产量进行观测。相比于对照,试验期间覆膜种植土壤10、20、30 cm平均温度分别提高了2.3、2.8、2.0℃,增温效果显著,而对土壤重量含水量的影响不明显;覆膜种植条件下,土壤耕层全氮、碱解氮、铵态氮和硝态氮含量分别为1.30 g/kg、150.83 mg/kg、112.25 mg/kg、105.80 mg/kg,分别比对照处理增加了7.44%、32.84%、88.72%和73.90%;另外,地膜覆盖能够促进植株发育并提高辣椒产量,使其开花坐果期提前4 天,结果时间提前5 天,辣椒产量提高14.11%。实验结果表明,地膜覆盖在改善土壤水热条件、增加土壤氮素含量以及提高作物产量方面具有积极作用。     

栽培方式对夏直播花生植株生长及产量的影响

为了探讨麦后夏直播花生的适宜栽培方式及其作用效果,为指导生产实践提供依据。在田间试验条件下,以‘青花7号’花生品种为材料,研究了不同栽培方式对夏直播花生植株生长和产量的影响。结果表明：采用花生夏直播高产保护性栽培法,可矮化株高,主茎高度较地膜覆盖的减少15.7%,防止徒长和倒伏;促进营养器官干物质积累,增加有效开花数、有效果针数;促进荚果发育,单株结果数较其他处理增加0.8~2.0个,公斤果数减少23.8~66.5个;显著增加干物质向荚果中分配的比例,经济系数提高0.08~0.17,荚果产量提高5.5%~29.2%。地膜覆盖的植株生育状况和产量优于露地栽培的,秸秆还田的优于不还田的。研究认为,在本试验条件下,采用花生夏直播高产保护性栽培法是取得夏直播花生高产的最佳栽培方式。     

不同灌溉方式对大棚黄瓜生长、产量及水分生产效率的影响

以黄瓜中农16为试材,研究了不同灌溉方式对其生长、产量、水分生产效率和经济效益的影响。结果表明:与对照相比,膜上沟灌、膜下沟灌和灌水带处理能够促进植株生长、提高产量和水分生产效率。其中膜下沟灌处理的产量、水分生产效率和经济效益最高,产量提高10.1%,处理间差异显著;水分生产效率提高6.5kg/m3,经济效益增加6291元/hm²。因此,膜下沟灌是春茬黄瓜大棚栽培适宜的灌溉方式。     

A simplified approach to define the yield surface of concrete-filled square steel tubes subjected to compression-bending

When the plastic hinge method is used to simulate the elasto-plastic properties of concrete-filled steel tubular structures,the plastic interactive yield surfaces of concrete-filled steel tubular column sections need to be defined.Although the fiber model approach can be well applied to the yield surface analysis,the numerical method is still complicated for the real applications.Therefore based on the experimental and theoretical researches on concrete-filled square steel tubular (CFST) members,this paper develops one method to determine the elastic element parameters.Then a simplified approach to quickly define the axial force-moment interactive plastic yield surface of concrete-filled square steel tubular columns is developed through theoretical analysis and a large number of parametric analyses.Finally,the fiber model method is adopted to verify the feasibility and validity of the proposed method.Results of the two methods are in good agreement,which indicates that the proposed method is reliable.     

不同栽培方式对中单808产量和经济效益的影响

以中草808为供试材料,比较育苗覆膜栽培、直播覆膜栽培与常规栽培技术对玉米产量和效益的影响.结果表明：玉米育苗覆膜栽培产量最高,效益最好,直播覆膜栽培次之,常规栽培相对较低.建议加大推广玉米育苗覆膜栽培技术.     

Several Matters to be Noticed During the Moment Modulation Design of Prestressed Concrete Frame

The moment modulation of prestressed concrete frame has some differences compared with that of continuous beam.Based on the analysis of ratio of column linear rigidity to beam one,form of load,second moment and plastic hinge in column,this paper is intended to get some helpful advise for moment modulation design.     

耐候地膜对陇中旱农区玉米农田的水热效应及耐候性评价

陇中旱农区水热资源有限,不能满足玉米生长发育需求。全膜双垄沟播技术突破了该区域玉米种植的水热限制,使玉米成为了当地主栽作物,但也带来了严重的残膜污染问题。为了引进耐候易回收地膜,本研究采用田间试验,研究了不同成分PE地膜（T1、T2、T3、T4,其中T1、T2、T3为设计的耐候性地膜,T4为传统PE地膜）和可降解膜(T5)对玉米农田水热状况、玉米光合特性、产量的影响,并评价了各种地膜的耐候性。结果表明：在玉米全生育期,耐候性地膜(T1、T2、T3)与普通地膜(T4)土壤含水率相似,但与降解膜(T5)相比,耐候性地膜T2可提高苗期30~50 cm土层土壤含水率。各种地膜在5、10 cm土层全生育期土壤平均温度基本无显著差异,但降解膜(T5)的全生育期土壤平均温度在15、20、25 cm土层分别较PE膜(T1、T2、T3、T4)降低了0.5~1.4℃、0.3~1.1℃和1.0~2.3℃。拔节期、大喇叭口期、灌浆期PE膜(T1、T2、T3、T4)的玉米叶面积指数均显著大于降解膜(T5),耐候性地膜T1与普通地膜相比可以显著改善玉米大喇叭口期光合特性。PE膜(T1、T2、T3、T4)玉米籽粒产量分别较降解膜(T5)增加了40.41%、45.04%、27.41%和32.80%,生物产量各处理间无显著差异,耐候性地膜(T1、T2、T3)与传统地膜(T4)无显著差异。玉米收获后,耐候性地膜的纵向拉伸负荷显著大于T4,且T1的纵向拉伸负荷、横向拉伸负荷以及纵向断裂标称应变均最大,易回收性高于其他地膜。因此,在陇中旱农区应用耐候地膜T1,与传统PE膜T4具有相似的水热效应,玉米产量也相当,但玉米收获后易于回收,有助于减轻残膜污染问题,但可降解膜由于提温效果有限,会降低玉米产量。     

Field Test Analysis on Belled Pier Foundations under Tensile Load in Gravel Gobi

Forty full scale field tests were conducted on belled pier foundations at seven gravel Gobi sites in Gansu province and Xinjiang Uygur Autonomous Region in China. The uplift load displacement response of belled pier foundations in gravel Gobi almost followed the same pattern and presented three phase behaviors. Under tensile load, the onset of the curve usually started from the elastic linear part resulting from the compression and compaction of gravel Gobi above the enlarged base. And consequently, with the occurrence and further development of a plastic zone around the foundation, the uplift load displacement curve turned into an elasto plastic stage. Finally, the formation of whole rupture surface brought to the entire shearing damage of Gobi soil. The ultimate uplift bearing capacities were obtained by using the slope tangent method for all test foundations. Based on the theory of limiting equilibrium, the Mohr Coulomb yielding criterion and slip line field method, the circle arc rupture surface boundary condition was introduced. And the theoretical calculation equation to determine the ultimate uplift bearing capacity of the belled pier foundation in gravel Gobi was obtained. The theoretical results were compared with those of the tests and they turned out in good agreement.     

不同栽培方式和秸秆还田对水稻产量和营养品质的影响

为阐明水稻产量和营养品质在不同栽培方式和秸秆还田条件下的表现特性, 以两优培九(籼稻)为材料, 常规水作(CFC)为对照, 通过长期定位试验(2001—2010年)研究了覆膜旱作(PFMC)、裸地旱作(NMC)和秸秆还田对水稻产量、精米中蛋白质和氨基酸、糙米中铁和锌含量的影响。2008—2010三年试验结果(平均值)表明, 与CFC相比, PFMC能显著增加水稻产量, 增产幅度达8.0%, 精米中总氨基酸含量下降3.5%, 精米中蛋白质, 糙米中铁锌含量与CFC处理差异不显著; NMC处理产量显著下降5.1%, 蛋白质、总氨基酸和铁含量分别下降4.4%、9.3%和11.9%。秸秆还田较不还田处理, CFC条件下, 产量增加了113.6 kg hm^-2; NMC条件下, 产量增加142.6 kg hm^-2; PFMC条件下, 产量增加522.1 kg hm^-2; 三种栽培方式产量平均增加3.3%, 糙米中的铁和锌含量平均增加3.1%和6.4%, 精米中蛋白质和总氨基酸含量差异不显著。本试验结果表明, PFMC能显著提高水稻产量, 秸秆还田能显著提高水稻产量和稻米中铁、锌含量。