Comparison on construction of strut-and-tie models for reinforced concrete deep beams

With consideration of the differences between concrete and steel,three solutions using genetic evolutionary structural optimization algorithm were presented to automatically develop optimal strut-and-tie model for deep beams.In the finite element analysis of the first method,the concrete and steel rebar are modeled by a plane element and a bar element,respectively.In the second method,the concrete and steel are assigned to two different plane elements,whereas in the third method only one kind of plane element is used with no consideration of the differences of the two materials.A simply supported beam under two point loads was presented as an example to verify the validity of the three proposed methods.The results indicates that all the three methods can generate optimal strut-and-tie models and the third algorithm has powerful capability in searching more optimal results with less computational effort.The effectiveness of the proposed algorithm III has also been demonstrated by other two examples.

Application of Strut-and-Tie Model for Design of Interior Anchorage Zone in Post-tensioned Concrete Structure

Currently, traditional analysis and design methods are unreasonable in evaluating the performance and safety of pavements. The characteristic of shakedown theory lends itself particularly to the analysis of pavements. Based on the lower bound shakedown theory, a simple and practical procedure for shakedown analysis of pavements has been developed using plastic strain energy as shakedown criteria via considering a special loading path. The proposed method is verified by using a homogeneous isotropic half space. Then, the method is applied to analyze a two-layered pavement. The dependence of shakedown limit on material properties of pavements is investigated in details. According to the analysis results, some valuable references are suggested for the selection of materials for accurate evaluation of the bearing performance of pavement under traffic loading.

Application of Strut-and-Tie Model Zone in Post-tensioned for Design of Interior Anchorage Concrete Structure

This paper presents an application of strut-and-tie model(STM) to design the interior anchorage zone(IAZ) in the post-tensioned concrete structure.The STM theory and range of IAZ are introduced.Then,based on the finite element analysis,a series of simplified equations to calculate internal forces in IAZ are presented.Finally,the STM model for IAZ is given.In the proposed STM model,internal forces in ties vary with the dimension ratio and the eccentricity of load.The U-turn of internal forces is suggested to allocate rebar to resist bearing flexural tensile force.Compared with the FIP(International Federation for Prestressing) model,the proposed STM model is more reasonable and applicable.

基于STM模型钢筋混凝土开洞深梁的设计

基于strut-and-tie模型理论,采用美国《混凝土结构设计规范》(ACI 318-11)对一开洞深梁进行了设计,并与采用我国《混凝土结构设计规范》(GB 50010—2010)的计算结果做了对比分析。在应用美国规范时采用MIDAS软件分析得到深梁的应力云图,并以此作为设计strut-and-tie模型的依据。最后对两种计算结果进行了分析比较。

新型泡沫混凝土轻钢龙骨复合墙体抗剪承载力计算方法研究

为获得轻钢龙骨蒙皮板复合墙体和新型泡沫混凝土轻钢龙骨复合墙体抗剪承载力的实用计算方法,该文对1∶1的四片墙体DD-1、DD-2、DD-1(D-300)、DD-2(D-400)进行单调加载,对1∶1的两片墙体DZ-1(D-300)、DZ-2(D-400)进行低周反复加载。在试验基础上,确定了基于轻钢龙骨蒙皮板复合墙体螺钉群破坏模型的抗剪承载力计算方法,并分别采用轻钢轻混凝土模型与strut-and-tie模型对新型泡沫混凝土轻钢龙骨复合墙体进行简化,从而推导出抗剪承载力实用计算公式。根据试验结果对抗剪承载力公式进行修正,修正后的计算结果与试验值吻合较好,其中轻钢轻混凝土模型具有更高的吻合度。研究结果可供结构设计和施工参考。

Experimental study on load bearing behavior of large-scaled caps with pile groups

The objective of this investigation was to study the behavior of deep pile caps and the ultimate load-carrying capacity. Four 1/10 scaled models of nine-pile caps were cast and tested on vertical loads to failure. The destruction shapes of pile caps,the correlation between load and displacement,and the internal stresses were analyzed systematically. The results demonstrated that the failures of all the four models are resulted from punching shear; the internal flow of the forces in nine-pile caps can be approximated by "strut-and-tie" model. Furthermore,the failure loads of these specimens were predicted by some of the present design methods and the calculated results were compared with the experimental loads. The comparative results also indicated that the "strut-and-tie" model is a more reasonable design method for deep pile caps design.

压杆-拉杆设计法在花瓶式桥墩设计中的应用

介绍了压杆-拉杆模型进行混凝土构件D区设计的方法,对模型的选择,压杆、拉杆及节点区尺寸的确定进行了阐述,并将其应用于混凝土花瓶式桥墩墩顶区域的配筋设计。建立了桥墩有限元模型进行极限承载力分析,对压杆-拉杆模型参数的选取以及配筋结果进行验证。认为合理的选取压杆-拉杆模型和参数进行构件验算,可以减少按经验配筋的盲目性,优化花瓶式桥墩墩顶配筋。