Experimental Study on Seismic Performance of SRUHSC⁃RC Frame Exterior Joints with Cyclic Loads

SRUHSC⁃RC(Steel Reinforced Ultra High Strength Concrete⁃Reinforced Concrete)structures are used extensively in super high⁃rise buildings.However,it has obvious brittleness.Wrapping structural steel inside is a good way to alleviate the brittleness problem.The purpose of this study is to investigate seismic behavior of SRUHSC⁃RC exterior joints on the basis of experimental results of eleven specimens under the reversed cyclic loading.The relationship among the force⁃displacement curve,ductility,energy dissipation property,strength degradation,stiffness degradation,the strains of steel bone and stirrup at the core area of the joint were analyzed based on the test results.It is shown that axial compression ratio and stirrup volumetric ratio have significant effects on the shear behavior of SRUHSC⁃RC frame exterior joints.The general requirement on the axial⁃load level and the amount of confinement stirrup for the joints in the design is suggested.

Pushover analysis of reinforced concrete frames considering shear failure at beam-column joints

Since most current seismic capacity evaluations of reinforced concrete （RC） frame structures are implemented by either static pushover analysis （PA） or dynamic time history analysis, with diverse settings of the plastic hinges （PHs） on such main structural components as columns, beams and walls, the complex behavior of shear failure at beam-column joints （BCJs） during major earthquakes is commonly neglected. This study proposes new nonlinear PA procedures that consider shear failure at BCJs and seek to assess the actual damage to RC structures. Based on the specifications of FEMA-356, a simplified joint model composed of two nonlinear cross struts placed diagonally over the location of the plastic hinge is established, allowing a sophisticated PA to be performed. To verify the validity of this method, the analytical results for the capacity curves and the failure mechanism derived from three different full-size RC frames are compared with the experimental measurements. By considering shear failure at BCJs, the proposed nonlinear analytical procedures can be used to estimate the structural behavior of RC frames, including seismic capacity and the progressive failure sequence of joints, in a precise and effective manner.

Seismic Behaviour of Beam-Column Joints of Precast and Partial Steel Reinforced Concrete

A beam-column joint of precast and partial steel reinforced concrete( PPSRC) is proposed for precast reinforced concrete frames. The PPSRC consists of partial steel and reinforced concrete. The partial steel is located in the core joint region and the connections between concrete members. This paper presents an experimental study of a series of PPSRC specimens. These specimens are tested under low cyclic loading.Experimental results demonstrate that the bearing capacity of the PPSRC specimens is 3 times that of the ordinary reinforced concrete( RC) beam-column joints. The strength and stiffness degradation rates are slower compared with that of the RC beam-column joints. In addition,the strength of the core joint region and the connections is higher than other parts of the PPSRC specimens. Beam failure occurs firstly for the PPSRC specimens,followed by column failure and connections failure. The failure of the core joint region occurs finally.Test results show that the seismic performance of the PPSRC is better than that of the ordinary RC beam-column joints.

Experimental Studies on Seismic Behavior of Exterior SRUHSC Joints

To investigate the seismic behavior of the joints,six steel reinforced ultra high strength concrete( SRUHSC) frame exterior joints were tested. Three levels of axial compressive ratio varying from 0.25 to 0.45 were investigated to determine how this variable might influence the performance of the joints including failure mode,ductility,energy dissipation capacity,stiffness degradation,shear strength and shear deformation by the quasi-static cyclic test on SRUHSC exterior joints. This research program suggests that the design of joint should make full use of the joint panel deformation to dissipate energy of earthquake. It is tested that the value of 0.38 as a dividing point about the effect of axial compression ratio on the seismic performance of SRUHSC exterior joints should be taken into account in design. In addition,the increase of volumetric ratio of stirrup could possess the ductility for adequate response to unexpected strong earthquakes and a recommended value of minimum volumetric ratio of stirrup with high axial-load level is pointed out.

Finite Element Analysis (FEA) for the Beam-Column Joint Subjected to Cyclic Loading Was Performed Using ANSYS

This paper analyses the seismic performance of exterior beam-column joints strengthened with unconventional reinforcement detailing. The beam-column joint specimens were tested with reverse cyclic loading applied at the beam end. The samples were divided into two groups based on the joint reinforcement detailing. The first group (Group A) of three non-ductility specimens had joint detailing in accordance with the construction code of practice in India IS456-2000, and the second group (Group B) of three ductility specimens had joint reinforcement detailed as per IS13920-1993, with similar axial load cases as the first group. The experimental studies are proven with the analytical studies carried out by finite element models using ANSYS. The results show that the hysteresis simulation is satisfactory for both un-strengthened and ferrocement strengthened specimens. Furthermore, when ferrocement strengthening is employed, the strengthened beam-column joints exhibit better structural performance than the un-strengthened specimens of about 31.56% and 38.98 for DD-T1 and DD-T2 respectively. The analytical shear strength predictions were in line with the test results reported in the literature, thus adding confidence to the validity of the proposed models.

配筋PVA-钢混杂纤维增强水泥基复合材料梁柱边节点抗震性能试验研究

改善工程材料韧性和耐久性,提高框架梁柱节点抵抗变形和破坏的能力,是提高框架结构抗震韧性的有效途径之一。采用PVA-钢混杂纤维增强水泥基复合材料代替普通混凝土应用到梁柱边节点,考虑轴压比和加密区体积配箍率的影响,设计6个配筋PVA-钢混杂纤维增强水泥基复合材料、1个配筋单掺PVA纤维增强水泥基复合材料和1个钢筋混凝土梁柱边节点试件进行拟静力试验,分析其破坏形态、滞回曲线、骨架曲线、延性、耗能能力、钢筋应变和梁端塑性铰区转角,探讨混杂纤维的加入对梁柱边节点抗震性能的影响。结果表明:与钢筋混凝土节点和单掺PVA纤维增强水泥基复合材料节点相比,PVA-钢混杂纤维增强水泥基复合材料节点的承载力高、变形能力大、延性好、耗能能力强,抗震性能显著提升。当试验轴压比从0.12增加到0.24,梁端塑性铰区产生一定的外移,塑性性能发挥更充分,同时试件的变形能力、延性、耗能能力增加。在加密区体积配箍率减小的情况下,试件仍表现出良好的抗震性能。

建筑外墙保温板接缝专用改性聚醚密封胶制备及特性研究

为提升建筑外墙保温板的使用寿命,制备装配式建筑外墙保温板接缝用改性聚醚密封胶,并通过试验分析该密封胶性能。以封端硅烷偶联剂和异腈酸酯基硅烷作为改性剂,聚醚元醇作为基料制备改性聚醚密封胶,应用在装配式建筑外墙保温板接缝中。依据标准测试该密封胶的表观性能,研究养护时间、紫外光照对该密封胶的粘接强度影响,分析催化剂和填料用量对于该密封胶表观性能与拉伸性能影响。试验结果表明,该密封胶表观性能符合标准,养护7 d后粘接性能基本稳定,催化剂用量20%,填料用料30%时表观性与拉伸性能最好。

装配式混凝土建筑外墙接缝密封胶施工技术

混凝土建筑外墙接缝密封施工是装配式建筑施工过程中的重要环节,对整个建筑的施工质量有重要影响。在对装配式建筑工程概况进行介绍的基础上,分析了常见密封胶的类型与性能,选用MS密封胶对外墙接缝进行施工。密封胶施工时先要向墙缝内部填入背衬材料并在外墙表面粘贴美纹纸,然后才能对密封胶进行施工。从深化设计、接缝清洁、背衬材料填入、密封胶施工等多个方面对相关施工技术进行介绍。

建筑外墙结构伸缩缝支模防变形施工技术

在建筑工程项目施工环节,建筑外墙结构伸缩缝支模施工属于重要施工流程。但是结合大量的建筑工程施工案例可知,在建筑外墙结构伸缩缝支模施工环节,非常容易产生支模变形问题。基于此,笔者结合实际工程案例分析建筑外墙结构伸缩缝支模变形施工工艺,期望对提升建筑工程项目施工质量有所帮助。

装配整体式剪力墙结构住宅外墙防渗漏施工技术的应用

装配整体式剪力墙结构住宅的施工效率较高,是现代建筑事业发展中的常见建筑形式,在外墙施工阶段,需提高防水、防渗漏意识,结合装配式住宅特点选择合适的防水材料,保证材料应用功能,进行科学的装配整体式剪力墙结构住宅外墙防水设计,并结合建筑工程实际优化建筑外墙灌浆工艺,实现外墙防渗漏施工技术有效落实,提高住宅外墙使用性能,预防渗漏问题发生。

装配式建筑外墙施工缝的防渗漏施工技术分析

在进行装配式建筑现浇外墙施工过程中不可避免地会出现水平施工缝,若没能进行妥善处理,则极易出现渗漏的现象,会对整体建筑的稳定与安全产生严重威胁,因此必须予以重视。文章对该技术的施工要点进行了详细的阐述,结合一处棚户区改造工程,深入分析了建筑外墙水平缝渗漏的原因,同时探讨了在建筑工程中的铝合金模板K板上安装三角形防渗漏企口装置的应用效果。

浅析建筑外墙接缝密封胶现场施工技术

接缝密封胶技术是建筑外墙连接作业中的一种常用技术,可有效提升外墙接缝区域防水能力和立面效果。工程人员应基于工程实际情况,合理制定密封胶技术应用方案,进而保障整体工程建设质量与建设效率。基于此,本文简单分析建筑外墙接缝密封胶现场施工技术要点,并深入探讨技术应用实例,以供参考。

Seismic performance of steel reinforced ultra high-strength concrete composite frame joints

To investigate the seismic performance of a composite frame comprised of steel reinforced ultra high-strength concrete （SRUHSC） columns and steel reinforced concrete （SRC） beams, six interior frame joint specimens were designed and tested under low cyclically lateral load. The effects of the axial load ratio and volumetric stirrup ratio were studied on the characteristics of the frame joint performance including crack pattern, failure mode, ductility, energy dissipation capacity, strength degradation and rigidity degradation. It was found that all joint specimens behaved in a ductile manner with flexural-shear failure in the joint core region while plastic hinges appeared at the beam ends. The ductility and energy absorption capacity of joints increased as the axial load ratio decreased and the volumetric stirIup ratio increased. The displacement ductility coefficient and equivalent damping coefficient of the joints fell between the corresponding coefficients of the steel reinforced concrete （SRC） frame joint and RC frame joint. The axial load ratio and volumetric stirrup ratio have less influence on the strength degradation and more influence on the stiffness degradation. The stiffness of the joint degrades more significantly for a low volumetric stirrup ratio and high axial load ratio. The characteristics obtained from the SRUHSC composite frame joint specimens with better seismic performance may be a useful reference in future engineering applications.

Seismic performance and global ductility of RC frames rehabilitated with retrofi tted joints by CFRP laminates

This paper presents a new FRP retrofi tting scheme to strengthen local beam-column joints in reinforced concrete(RC) frames.The new retrofi tting scheme was proposed following a preliminary study of four different existing retrofi tting schemes.A numerical simulation was conducted to evaluate the effectiveness of FRP-strengthened reinforced concrete frames by bridging behavior of local joints to the whole structure.Local confi nement effects due to varying retrofi tting schemes in the joints were simulated in the frame model.The seismic behavior factor was used to evaluate the seismic performance of the strengthened RC frames.The results demonstrated that the new proposed retrofi tting scheme was robust and promising,and fi nite element analysis appropriately captured the strength and global ductility of the frame due to upgrading of the local joints.

Study on Strengthening of RC Beam Column Joint Using Hybrid FRP Composites

Beam-Column joints are critical zones in reinforced concrete structures which are most vulnerable to earthquake forces. Hence strengthening beam-column joint is vital to save the structure and its inhabitants in case of seismic forces. Numerous retrofitting works using fibre reinforced polymer (FRP) composites are being undertaken worldwide. This work aims to investigate the effectiveness of strengthening beam-column joints using natural and artificial fibres. In this study, basalt (natural fibres) as monolithic composite (BFRP) and as hybrid composite along with glass (artificial fibres) were used for strengthening of beam-column joints. Totally six specimens were prepared and tested under monotonic loading. Specimen details used were: two control specimen, two specimens for monolithic wrapping and remaining two specimens for hybrid wrapping. The test results were compared with control and rehabilitated specimens. The performance of the treated joints was studied using the following parameters: initial and ultimate cracking loads, energy absorption, deflection ductility and stiffness at ultimate. From the test results, it was found that the hybrid combination of Basalt and Glass FRPs were found to be more effective in the treatment of beam-column joints. The strong column weak beam concept was achieved by failure in beam portion which helped in preventing the catastrophic failure of the entire structure.

轻钢龙骨防火外墙及其与钢框架连接的平面外受力性能分析

针对轻钢龙骨防火外墙在L形角钢连接、异形角钢连接两种连接方式下的平面外受力性能进行了试验研究。然后采用有限元软件ABAQUS对试件进行模拟分析,模拟结果与试验结果吻合良好,验证了有限元模型的有效性。进而考虑竖向轻钢龙骨间距及布置方式、横向轻钢龙骨厚度、异形角钢连接件个数、L形角钢与型钢梁连接自攻螺钉个数、L形角钢厚度六个因素的影响,对轻钢龙骨防火外墙及其与钢框架连接的平面外受力性能进行有限元模拟分析。结果表明:增加异形角钢连接件个数或L形角钢的自攻螺钉个数可提高墙体平面外极限承载力和刚度及连接件平面外刚度,且提高效果最为显著;减小龙骨间距能提高墙体平面外极限承载力及刚度;增加横向轻钢龙骨厚度能提高墙体平面外极限承载力和连接件平面外刚度;增加L形角钢厚度可明显提高墙体及连接件平面外刚度。

高温对装配式建筑外墙接缝密封胶性能的影响

为分析装配式建筑外墙接缝密封胶在高温环境中的性能,以基础树脂、增塑剂为主原料,结合MS专用黑色母料等多种辅原料制备MS密封胶,用制备的密封胶密封2块装配式混凝土外墙板试样,并在热老化和紫外线老化两种条件下设定不同的温度,测试密封胶的性能。试验结果显示:在两种条件下,温度由16℃上升20℃又达到40℃的过程中,拉伸强度由0.544 MPa上升至0.572 MPa又下降至0.537 MPa;其中,温度为20℃时,拉伸强度最佳;同时,随着温度的逐渐增加,密封胶断裂伸长率及粘结强度逐渐下降;密封后的外墙接缝试样在两种条件下随着温度的逐渐增加,防水性能逐渐下降,当温度达到超高温140℃时,防水性能几乎完全丧失,在温度为80℃内时,可保证较好的防水性,满足日常生活需求。

外墙接缝用改性硅酮密封胶的制备与性能研究

针对外墙接缝用硅酮密封胶易受温度变化、紫外线辐射、水分侵蚀等多种环境因素及与其自身材料性能影响,导致老化程度加快的情况。选择二甲基硅油[C_(2)H_(6)OSi)_(n)]作为增塑剂,纳米CaCO_(3)作为补强填料,经过交联剂和偶联剂共同作用,在催化条件下,制备得到外墙接缝使用的硅酮密封胶样品。结果表明:硅酮密封胶样品经纳米CaCO_(3)改性后,纳米CaCO_(3)的皂化程度、硅酮密封胶的密封性和耐水性得到提高,密封胶的拉伸粘接强度随着养护时间的延长而逐渐增大,硅酮密封胶的老化过程逐渐变慢。

装配式建筑外墙水平施工缝防渗漏研究

为有效解决当前装配式建筑与现浇混凝土结合的结构形式普遍存在的水平施工缝渗漏问题,以3751-C地块棚户区改造及环境整治项目安置房工程二标段为例,对其建筑外墙水平缝渗漏原因展开分析,并设计出一种安装于铝合金模板K板上的水平施工缝三角形防渗漏企口装置,对该装置在住宅楼工程中的应用进行探讨,取得较好的外墙防渗漏效果。结果表明,所应用的外墙水平缝防渗漏装置既有效解决装配式现浇外墙水平施工缝渗漏问题,又为装配式建造技术与铝合金模板施工技术的结合应用提供保证。

装配式建筑外墙板防水技术优化研究

装配式建筑外墙板拼接缝众多,是防水的关键,也是防水的难点,如果防水处理不当会影响工程质量。本文结合北京门头沟区龙泉镇大峪化工厂棚改装配式建筑项目,针对外墙板尤其是梁下外墙板横纵缝等接缝多、防水难点大的问题,对外墙板防水工艺进行优化,有效提高装配式建筑外墙板防水关键节点的防水质量,确保主体结构的使用功能、耐久性和安全性,为类似装配式防水工程提供借鉴。