Numerical Modeling Strategy for the Simulation of Nonlinear Response of Slender Reinforced Concrete Structural Walls

A three-dimensional nonlinear modeling strategy for simulating the seismic response of slender reinforced concrete structural walls with different cross-sectional shapes is presented in this paper.A combination of nonlinear multi-layer shell elements and displacement-based beam-column elements are used to model the unconfined and confined parts of the walls,respectively.A uniaxial material model for reinforcing steel bars that includes buckling and low-cyclic fatigue effects is used to model the longitudinal steel bars within the structural walls.The material model parameters related to the buckling length are defined based on an analytical expression for reinforcing steel bars embedded in reinforced concrete elements,which are developed based on beam-on-springs model,and validated with experimental tests of boundary elements of structural walls available in the literature.Six experimental case studies of reinforced concrete walls with rectangularshape,T-shape,and U-shape cross-section are used to validate the structural wall numerical modeling strategy.

Full－range nonlinear analysis of fatigue behaviors of reinforced concrete structures by finite element method

The offshore reinforced concrete structures are always subject to cyclic load, such as wave load.In this paper a new finite element analysis model is developed to analyze the stress and strain state of reinforced concrete structures including offshore concrete structures, subject to any number of the cyclic load. On the basis of the anal ysis of the experimental data,this model simplifies the number of cycles-total cyclic strain curve of concrete as three straight line segments,and it is assumed that the stress-strain curves of different cycles in each segment are the same, thus the elastoplastic analysis is only needed for the first cycle of each segment, and the stress or strain corresponding to any number of cycles can be obtained by superposition of stress or strain obtained by the above e lastoplastic analysis based on the cyclic numbers in each segment.This model spends less computer time,and can obtain the stress and strain states of the structures after any number of cycles.The endochronic-damage and ideal offshore concrete platform subject to cyclic loading are experimented and analyzed by the finite element method based on the model proposed in this paper. The results between the experiment and the finite element analysis are in good agreement,which demonstrates the validity and accuracy of the proposed model.

NONLINEAR ANALYSIS OF REINFORCED CONCRETE RECTANGULAR SLABS USING FINITE ELEMENT METHOD

The nonlinear analysis of reinforced concrete rectangular slabs undermonotonic transverse loads is performed by finite element method.The layered rectangu-lar element with 4 nodes and 20 degrees of freedom is developed,in whichbending-stretching coupling effect is taken into account.An orthotropic equivalentuniaxial stress-strain constitutive model of concrete is used.A program is worked out andused to calculate two reinforced concrete slabs.The results of calculation are in goodconformity with the corresponding test results.In addition,the influence of tension stif-fening effect of cracked concrete on the results of calculation is discussed.

Achievements of Truss Models for Reinforced Concrete Structures

Achievements are presented for truss models of RC structures developed in previous years: 1. Two constitutive models, biaxial and triaxial, are based on regular trusses, with bars obeying nonlinear uniaxial σ-ε laws of material under simulation;both models have been compared with test results and show a dependence of Poisson ratio on curvature of σ-ε law. 2. A truss finite element has been used in the nonlinear static and dynamic analysis of plane RC frames;it has been compared with test results and describes, in a simple way, the formation of plastic hinges. 3. Thanks to the very simple geometry of a truss, the equilibrium equations can be easily written and the stiffness matrix can be easily updated, both with respect to the deformed truss, within each step of a static incremental loading or within each time step of a dynamic analysis, so that to take into account geometric nonlinearities. So the confinement of a RC column is interpreted as a structural stability effect of concrete. And a significant role of the transverse reinforcement is revealed, that of preventing, by its close spacing and sufficient amount, the buckling of inner longitudinal concrete struts, which would lead to a global instability of the RC column. 4. The proposed truss model is statically indeterminate, so it exhibits some features, which are not met by the “strut-and-tie” model.

Nonlinear seismic response analysis of reinforced concrete tube in tube structure

Super-highly reinforced concrete tube in tube structure is a developing structure system of high-rise building. The more reasonable derivation process of the multi-vertical-line-element model stiffness matrix is given.On the premise of pointing out the problems of present multi-spring element model, combined with present multivertical-line-element model for analyzing on shear wall, the model is expanded to spatial one, and the stiffness matrix of which is derived. Combined with hysteretic axial model and hysteretic shear model, it is suitable for columns,wall limbs and beams with all kinds of section form. Some examples are calculated and compared with test results,which shows that the models have relatively good accuracy. On the base of the experimental phenomenon and failure mechanism for tube in tube structure specimen, nonlinear seismic responses analysis program on the basis of the advantaged element model for tube in tube structure is developed. Calculation results are in good agreement with those of the pseudo-dynamic tests and the failure mechanism can be well reflected.

The Structural Behavior of Low/Medium/High Rise Concrete Office Buildings in Kuwait

The main concern of this paper is to provide an extensive study for the structural behavior of low/medium/high rise office buildings aiming to deepen structure and architect designers understanding for such type of buildings. The study is performed on reinforced concrete and emphasized only on Kuwait city conditions for wind. Regular layout plan building with different heights ranging from five to fifty typical office stories are investigated in this study. Three dimensional finite element techniques through ETABS software are used in conducting analysis for structures presented here-in. A serviceability study is performed to ensure that buildings have sufficient stability to limit lateral drift and peak acceleration within the acceptable range of occupancy comfort. In addition, an ultimate strength study is carried out to design and verify that all the structural elements are designed to withstand factored gravity and lateral loadings in a safe manner according to the international building codes. The building slenderness ratio and the building core size and location are the studied parameters since they are the key drivers for the efficient structural design. Analysis results are presented and discussed and finally conclusions are summarized as guidelines for designers of concrete office buildings in Kuwait.

Strength&Conduct of Reinforced Concrete Corner Joint under Negative Moment Effect

The aim of our study is to reveal the effect of steel reinforcement details,tensile steel reinforcement ratio,compressed reinforcing steel ratio,reinforcing steel size,corner joint shape on the strength of reinforced concrete Fc'and delve into it for the most accurate details and concrete connections about the behavior and resistance of the corner joint of reinforced concrete,Depending on the available studies and sources in addition to our study,we concluded that each of these effects had a clear role in the behavior and resistance of the corner joint of reinforced concrete under the influence of the negative moment and yield stress.A study of the types of faults that can be reinforced angle joints obtains details and conditions of crushing that are almost identical for all types of steel reinforcement details and the basic requirements for the acceptable behavior of reinforced concrete joints in the installations and the efficiency of the joint and this may help us to prepare for disasters,whether natural or other,as happens with tremors The floor and failure that may occur due to wrong designs or old buildings and the possibility of using those connections to treat those joints and sections in reinforced or unarmed concrete facilities to preserve the safety of humans and buildings from sudden disasters and reduce and reduce risks,as well as qualitative control over the production of concrete connections and sections free from defects to the extreme.

Exploring the Synergy: Experimental and Theoretical Investigation of Steel and Glass Fiber Reinforced Polymer (GFRP) Reinforced Slab Incorporating Alccofine and M-Sand

Introduction: This study investigates the Experimental and Theoretical Investigation of Steel and Glass Fiber Reinforced Polymer (GFRP) Reinforced Slab Incorporating Alccofine and M-sand. Objective: Specific objectives include evaluating the mechanical properties and structural behaviour of steel and GFRP-reinforced one-way slabs and comparing experimental and theoretical predictions. Methods: Four different mix proportions were arrived at, comprising both conventional concrete and Alccofine-based concrete. In each formulation, a combination of normal river sand and M-sand was utilized. Results: Concrete with Alccofine exhibits superior mechanical properties, while M-sand incorporation minimally affects strength but reduces reliance on natural sand. GFRP-reinforced slabs display distinct brittle behaviour with significant deflections post-cracking, contrasting steel-reinforced slabs’ gradual, ductile failure. Discrepancies between experimental data and design recommendations underscore the need for guideline refinement. Conclusion: Alccofine and M-sand enhance concrete properties, but reinforcement type significantly influences slab behaviour. GFRP-reinforced slabs, though exhibiting lower values than steel, offer advantages in harsh environments, warranting further optimization.

Analysis of structural response under blast loads using the coupled SPH-FEM approach

A numerical model using the coupled smoothed panicle hydrodynamics-finite element method （SPH-FEM） approach is presented for analysis of structures under blast loads. The analyses on two numerical cases, one for free field explosive and the other for structural response under blast loads, are performed to model the whole processes from the propagation of the pressure wave to the response of structures. Based on the simulation, it is concluded that this model can be used for reasonably accurate explosive analysis of structures. The resulting information would be valuable for protecting structures under blast loads.

Finite element analysis on nut post structure of Three Gorges Project ship lift

A nonlinear finite element model of the nut post reinforced concrete （RC） structure of the safety mechanism in the Three Gorges Project （TGP） ship lift was built by ANSYS software. Some irregular structures such as the nut post and the rotary rod were divided by curved surface into a series of regular parts, and the structures were all meshed to hexahedron. Constraint equations were defined between two interfaces with different element sizes and mesh patterns. PRETS179 elements were used to simulate the preload in the tendons and the pre-stressed screws, and the loss of prestressing force was calculated. Five extreme load cases were analyzed. The stress of each part in the structure was obtained. The results indicate that the maximum compressive stress of concrete C35 is 24.13 MPa, so the concrete may be partially crushed; the maximum tensile stress of the grouting motar is 6.73 MPa, so the grouting motar may partially fracture; the maximum yon Mises stress of the rotary rod is 648.70 MPa, therefore the rotary rod may partially yield.

Arc-length technique for nonlinear finite element analysis

Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.

菠菜播种收割一体机结构设计与有限元分析

针对现有菠菜收割机留根、铲根深浅不一以及播种机撒播效率低、线绳播种成本高等问题,通过理论计算和SolidWorks建模分析,设计了一种犁地深度可调、整株收割、定量等距播种的菠菜播种收割一体机。采用Simulation模块对优化的机架和犁进行有限元分析发现,机架的大部分最大应力点位于机架前端的输料口处,在制造时需提高此处的焊接质量;犁须选用耐腐蚀性好的材料以减少其在腐蚀性土壤环境中的损坏。通过综合比较和有限元分析发现,机架所受最大应力均小于玻璃钢屈服极限,若通过合理成型设计弥补玻璃钢的成形性差等问题,有望使其成为未来农机具中犁制造的优选材料。研究结果可为菠菜播种收割一体机设计和关键部件优化提供一定理论参考。

复合材料格栅结构筋条纤维形态与拉伸性能

复合材料格栅结构已大量应用于航空航天飞行器中,探究其力学性能具有重要的工程研究价值。为提高复合材料格栅结构的承载效率,提出一种基于“断筋”处理的纤维形态改善方法,通过有限元分析与试验验证的手段,研究了不同断筋比例对复合材料格栅结构节点处纤维形态和拉伸性能的影响。利用建立的有限元模型分析了断筋处理的复合材料格栅结构拉伸失效机理,仿真与试验结果误差均小于10%。结果表明:在成型过程中适当进行断筋处理,能够显著降低节点处纤维弯曲角度,提高拉伸性能。相较于不进行断筋处理,断筋比例为30%时,拉伸极限载荷提高了24.4%。

某厂房混凝土柱柱根补强加固工艺的应用与研究

结构房屋在新建施工中也会出现很多问题,可能受到施工环境、工序等原因出现疏松、蜂窝、麻面等混凝土质量缺陷。本研究以晋北地区某厂房为例,探讨新浇筑混凝土柱出现烂根、露筋等问题后,进行补强加固处理的具体方法、施工流程,并通过有限元计算进行对比验算,为混凝土结构加固方案选择提供参考。

CFRP加固RC梁力学性能试验研究及有限元分析

为了研究碳纤维增强复合材料(CFRP)对钢筋混凝土梁的加固效果,对6组钢筋混凝土梁的抗弯性能开展试验研究,在试验研究中重点考察了CFRP加固对RC梁受弯时力学性能的影响。结果表明:①经CFRP布加固后的RC梁相较于未加固的RC梁,开裂荷载增加47.4%,屈服荷载增加34.2%,极限荷载增加27.4%。②CFRP加固后,梁内纵筋屈服时最大裂缝宽度减小0.1 mm,梁破坏时最大裂缝宽度减小0.8 mm。③CFRP加固能较大程度提高梁的力学性能及梁的延性,改善梁的破坏过程。为了继续探究CFRP的最佳加固形式,通过ABAQUS有限元数值模型模拟未加固及不同加固形式作用下梁加载的受力全过程,模拟结果与试验结果基本吻合。结果表明:增加加固层数、加固层厚度及改变加固形式都能显著提高梁的承载力,其中四面环绕式及三面U形的加固形式加固效果最好,加固层数控制在3层内加固效果最佳。

土耳其M_(w)7.8地震工业厂房及设施震害调查与分析

2023年2月6日,土耳其卡赫拉曼马拉什省在短时间内相继发生M_(w)7.8和M_(w)7.5地震。与以往地震相比,此次地震具有强度高、双主震的特点,造成了严重的灾害。地震发生后,通过资料收集、对地震中受损的工业厂房及设施进行现场震害调查,探讨了本次地震的地震动特征,比较了土耳其典型强震台站记录到的地震动加速度响应谱与我国规范谱的差异;总结了该地区典型工业厂房及设施的震害特征,并对其破坏原因进行了分析;选取土耳其典型强震台站记录到的地震波,对某核电厂耦合体系进行了单向地震作用计算,探讨了核电厂耦合体系在强震作用下的响应特征。现场调查结果表明:此次土耳其地震的强度远超我国规范的最高标准,且竖向地震动强度显著;一系列高强度地震造成灾区工业厂房及设施受损严重,厂房主体结构发生了严重的倒塌破坏,厂房中的非结构构件和生产设备也遭到了较为严重的破坏,其中非结构构件的破坏以墙体倒塌和吊顶掉落为主。核电厂房耦合体系计算结果表明,在土耳其强震作用下,核电厂内蒸汽发生器的响应大于其抗震能力中值,主管道应力响应大于其允许应力值。调查证明,工业厂房及设施的抗震薄弱环节在于厂房内部设施和设备,完善工业厂房及设施的抗震措施,提升工业设备的抗震能力,是提高工业厂房及设施抗震韧性的有效举措。

多元算法融合模型的CFRP约束型钢混凝土柱承载力预测

为准确预测多影响因素下碳纤维增强复合材料(CFRP)约束型钢混凝土柱(SRCC)的轴压承载力,提出了一种基于随机森林(RF)、分类提升(Catboost)、极端梯度提升(XGBoost)、梯度提升回归树(GBRT)的多元算法融合预测模型。首先采用合成少数类过采样技术(SMOTE)算法对原始数据集进行扩充,开展了10种传统机器学习和集成学习模型试验,筛选出决定系数R2均大于0.92的RF、Catboost、XGBoost、GBRT的4种集成学习模型,用随机搜索优化其超参数,然后融合形成了RF-Catboost-XGBoost-GBRT预测模型,对CFRP约束SRCC的承载力进行预测。结果表明,两种数据集下RF-Catboost-XGBoost-GBRT模型的预测性能最好,原始数据集经SMOTE算法处理后,5种预测模型R2平均提高20.43%,其中RF-Catboost-XGBoost-GBRT模型的R2达到了0.942,预测值误差均在±10%以内。

基于ANSYS平台非线性分析的RC构件建模方法

分离式模型的建立是钢筋混凝土结构和构件仿真中的关键问题,本文基于A N S Y S平台,以某钢筋混凝土实腹深梁为算例,开展2种共节点建模方法和2种不共节点建模方法下的非线性有限元对比分析,探讨建模方法对于仿真结果的影响。结果表明:节点生成切割法与弱耦合法在极限承载力和变形能力等方面的数值模拟结果较接近且均与试验结果较吻合,而强耦合法得出的极限承载力偏高;基于布尔运算切割几何模型的共节点建模方式,适用于形状规整、配筋简单的构件;在钢筋节点与混凝土节点之间,通过节点位移就近耦合的原则建立刚性连接的强耦合法,以及通过节点位移约束方程建立柔性连接的弱耦合法,都有着更强的通用性,能够完成边界条件或配筋方式复杂的构件建模,但相比之下,强耦合法计算精度略低,弱耦合法实现难度较高,所以在工程仿真中需要根据构件的几何特点和配筋方式选择合适的建模方法。

钢筋混凝土类桁架式转换结构的设计与研究

提出了一种新型钢筋混凝土类桁架式转换结构。以番禺天河城为例,阐述了类桁架式转换与传统梁式转换、钢桁架转换的优缺点,并对比分析了这三种转换方案的整体指标和材料用量。除验算其中震安全性、揭示其受力机理外,还对类桁架转换层构件在大震、超大震下的弹塑性损伤做了评估,揭示其屈服机制。通过类桁架转换节点的三维有限元分析,验证其连接可靠性,并提出相应的节点施工措施。研究结果表明:钢筋混凝土类桁架式转换结构具有良好的受力性能,能拓展建筑使用空间,节省工程造价,方便施工,可实现高层框支结构的合理转换。

钢筋混凝土结构梁柱节点滞回性能对比分析

为验证装配式强化梁柱节点与传统梁柱节点在受力和抗震性能方面的区别,借助ABAQUS的非线性分析功能分别建立了传统梁柱节点和装配式强化梁柱节点有限元模型,选择了合理的参数,分析了二者的破坏形态和滞回性能。结果表明:在相同荷载作用下,传统梁柱节点模型中的部分钢筋已发生破坏,强化梁柱节点中的钢筋未破坏,只部分钢筋进入塑性变形阶段,且通过滞回曲线对比显示:强化梁柱节点曲线的包络面积明显大于传统梁柱节点,说明了装配式强化梁柱节点的耗能能力更好。装配式强化梁柱节点设计的刚度、承载力和耗能能力均优于传统梁柱节点。