Mechanical Model of Steel Plate Composite Shear Walls

Based on concepts of mechanics, a mechanical model of novel type of steel plate composite shear wall is presented. The novel type of structure is formed by steel plate shear wall and T-shaped solid-web composite columns. Flexural stiffness of steel beams, lateral stiffness of the T-shaped solid-web composite columns, shear stiffness of steel plate composite shear wall and shear stiffness of beam-column connection are taken into account in the mechanical model. And the equivalent damping between steel plate and boundary is considered. Based on the deformation features of structures and the calculation hypothesis, the lateral stiffness model and the energy dissipation model of structures are developed. Meanwhile, the calculation equations of elastic ultimate and plastic ultimate of shear strength of structures are set up. The theoretical analysis results inosculate better with the results of experiment. The comparison between the result calculated from the formula and the experimental result shows that the calculation precision is high enough to meet the demand of theoretical analysis. The difference, including equivalent model, stress states, manufacturing defect and installation error, between the formula and the experiment has been further discussed.     

The Seismic Shear Capacity of I-Shaped and T-Shaped Reinforced Concrete Structural Walls

There are numerous shear walls with flanges in the high-rise buildings in P.R.China.The shear strength formula for shear walls in Chinese design codes lacks experimental data,while test results in other nations lack aseismatic shear strength test results for shear walls with flanges under axial force.In this paper,we report low-cyclic reverse load test results of shear wall models with large dimensions,one shear wall having an I-shaped cross-section and two with a T-shaped cross-section.We discuss why the aseismatic shear walls of high-rise buildings with large height-to-length ratios have small shear span ratios.We assess the reliability of the shear strength formulary in the Chinese codes for design of shear wall using the international shear wall test results.     

Experimental Investigation of Steel Frames with Infill Prefabricated Reinforce-Concrete Shear Walls

In order to improve seismic performance of steel frame with prefabricated reinforce-concrete infill shear walls (SFCW), the ear bar device was used in the connection between the steel frame and the infill wall. Two one-bay, two story and one-third scaled models of SFCW were tested with low cyclic load. The working performance of ear bar connection, the cracks development in infill walls and deformation performance of SFCW were investigated. And the failure mode, hysteretic behavior,stiffness degradation,deformation and ductility and energy dissipation of composite structure were analyzed. The comparison study of steel frame with prefabricated, cast-in-place and silt reinforce-concrete infill shear walls was carried out. The results show that no failure occurs in the connection between the steel frame and the infill wall because ear plates below and up the beam-to-column connections are added in the specimens, and the connection device of ear plate presents good working performance. The properly designed SFCW has good ductility.     

Finite Element Analysis of Hysteretic Behavior of PR Steel Frame-steel Plate Shear Wall

In order to investigate the seismic behavior of partially-restrained steel plate shear wall (Steel Plate Shear Wall, SPSW), the effects of partially-restrained connection on the hysteretic behavior, lateral bearing capacity, stiffness, energy dissipation of SPSW with strong and weak steel frame were simulated under low cyclic loading via equivalent strip model that had been verified by experiment. The results show that hysteretic behavior of SPSW has dual characters. The hysteretic curves of SPSW with strong surrounding steel frame become fat, and the hysteretic curves of SPSW with weak surrounding steel frame become narrow. With the increase of the bending capacity of PR connection, the hysteretic curves of SPSW become fat gradually, and the capacity of energy dissipation and lateral bearing increase. However, the effect on lateral stiffness of PR connection of SPSW with strong steel frame is higher than the one with weak steel frame.     

Refined Probabilistic Model of Resistance of RC Eccentric Compression Members

The probabilistic model of resistance in the current unified standard for reliability design is imprecise for RC members subjected to eccentric compression. The reason is that it lacks full considerations of influences of varying eccentricities. An improved probabilistic model of resistance with different eccentricities and reinforcement ratios is obtained by using the Monte Carlo sampling method and the current probabilistic models of all resistant factors. The results indicate that it is accurate to fit the probabilistic distribution of resistance with normal distribution. Given that, the applicability of the improved model is analyzed for reliability analysis of RC members subjected to eccentric compression with random eccentricities. It shows that when the design value of eccentricity is close to or larger than the eccentricity producing balanced failure, there would be large errors in reliability analysis if the probabilistic model of resistance given in the current reliability unified standard is used. However, it is accurate when using the proposed probabilistic model. The results also show that the design of RC members subjected to large eccentric compression is unsafe based on the current reliability unified standard because it lacks full considerations of effects that the resistance decreases as eccentricity increases.     

Calculation of Capacity of Vertically Loaded RC Joint of Local Transf er from Square Column to Straight Wall

On the basis of experimental results on four specimens of vertically loaded RC joints of local transfer from square column to straight wall, interaction between the transfer beam and the straight wall above it is analyzed. In the test, the effect of height of armpit on the transfer beam upon the behavior of the joint is specially studied. As a result, determination of the design shear force and shear capacity of the transfer beam and calculation of capacity of the straight wall are suggested, taking into account the effect of shear span ratio of the beam.     

Simplified Elasto Plastic Analytical Model for Stiffened Steel Plate Shear Wall with Slits

Based on the mechanism of steel slit wall, a simplified elasto plastic analytical model which allows for nonlinear dynamic and static analysis was proposed. The parameters of simplified model related to configuration and nonlinear behavior were defined. In order to validate the simplified model, the pushover analysis of steel slit wall and a frame with steel slit wall were conducted. The results show that the load displacement curves obtained from simplified models, experiments and FEM are similar. The proposed model can fully represent the mechanism of steel slit wall, and it can correctly predict the internal forces and deformations of each member in the model.     

Calibration of Nonlinear Dynamical Analysis for RC Frame-wall Structure with Slender Coupling Beams Considering Stiffness Reduction

Two 16-storey frame-wall structures with slender coupling beams in regions of Intensity 8(0.2 g),with and without considering the stiffness reduction of the coupling beams,were designed.Nonlinear dynamic response analyses of two typical frame-wall structures subjected to several ground motions were carried out.The analyses were based on the quasi-tridimensional program for nonlinear dynamic response analysis TS-EPA.The analyses led to the following conclusions: Under rare earthquake actions,the coupling beams in framewall structures yield first.This shows that the coupling beam in frame-wall structures is the member at the forefront of earthquake resistance.Comparison of the analytic results of two couples with and without considering the stiffness reduction of the coupling beam found that,in view of the dynamic response to and the requirement for ductility under rare earthquake motions,reducing stiffness causes a minor unfavorable influence on the dynamic response of frame-wall structures.     

Strut and Tie Model Method of ReinforcedConcrete Beam Column Joint Core

“Macro model” in OPENSEES is an ideal and effective method for simulating RC beam column joint. Some disadvantages, however, exist in both the modified compression field theory (MCFT) and diagonal compression strut model, with which they are commonly used to obtain the shear stress strain relation of joint core. A new method by means of strut and tie model (STM), which reflected three mechanisms in joint well, was proposed to simulate the shear stress strain response of joint core. The deformation compatibility and equilibrium condition of the model were deduced thereafter. It was indicated that the result of STM method was in good agreement with that of test data. And it could simulate more accurately the shear stress strain response of joint core with a wide range of stirrup ratio.     

Seismic Behaviors of Frames in Frame Wall Structures under Rare Earthquakes on the Zone of Fortification Intensity 8 in China

To investigate the seismic behaviors of frames in frame wall structures (dual system), which may be different from those of frame structures, two frame wall structures were designed conforming to current Chinese design codes. One is a twenty four story building on the Zone of Fortification Intensity 8 (0.3g), and the other is a thirty story building on the Zone of Fortification Intensity 8 (0.2g). Then inelastic dynamic response analyses of the two structures were conducted with series of inputs of ground motions in a rare earthquake level. The seismic behaviors of the two structures were investigated preliminarily. It was found that the columns and beams of the frames in the frame wall structures did not experienced yielding under strong earthquake, while coupled beams in walls were the major energy dissipation elements with their post yielding plasticity. And the bases of some walls formed hinges as well. The reasons for the frames of dual system remained non yielding states were analyzed and discussed from the aspects of their favorable load carrying state and strengthening measures for them in dual systems in Chinese design codes. A preliminary proposal was made that it may be feasible to loosen moderately some seismic fortification measures concerning the frame in the dual system with a height exceeding 60m on the Zone of Fortification Intensity 8.     

Influence Factors Study of Bearing Capacity of T Shaped RC Steel Reinforced Concrete Short-pier Shell Wall

In order to ensure that the T shaped steel reinforced concrete short-pier shear wall ductile shear failure occurs, the failure mechanism on the basis of experimental research, using ANSYS finite element analysis software to simulate the failure mode. In the process of analysis considered the influence factors of horizontal steel reinforcement ratio, concrete strength, axial compression ratio and the content of steel. The results show: the level of reinforced volume reinforcement ratio, concrete strength and the content of steel can obviously change the the bearing capacity and ductility of components.     

Seismic Performance of Regular RC Frame with Specially Shaped Columns

According to the code and technical regulation,an irregular RC frame with specially shaped columns has been designed,which situated at the area of fortification intensity 8. Subsequently,the nonlinear dynamic analysis has been carried out for the structure by inputting ground motions in two directions. After summing up the calculation results,this paper has examined seismic performance of the structure under the rare seismic actions and given a primary evaluation on the structure to see if it could achieve the predetermined anti-seismic aims. It indicates that the structure designed according to the codes can achieve the predetermined anti-seismic aim under the rare earthquake.     

Maximum Displacement Estimation of Seismic Structures Based on Hysteresis Energy

Based on characteristics of hysteretic energy of structures which are simplified single freedom degree systems and under the short duration impulse modle mid duration and long duration modle earthquakes, correlation between the maximum hysteretic energy increment per cycle and the maximum inelastic displacement of different structures is investigated. Simplified equations to estimate the maximum inelastic displacement are obtained. The validity of the equation is recognized. It is pointed out that the impact destroy of the structures may occur when energy increment per cycleis 50 80 percent of total hysteretic energy, and the maximum hysteretic energy increment per cycle, and that the maximum inelastic displacement can be used to evaluate aseismic capacity.If energy increment per cycleis small relative to total hysteretic energy, the destroy of the structures by cumulate dissipation energy may occur, and the total hysteretic energy can be used to evaluate aseismic capacity.     

偏载下板柱结构中柱节点破坏试验研究

采用重剪比以及配筋率两个试验变量对4个板柱中节点的破坏过程进行了对比试验,并在试验过程中采用特制应变测杆对试件内部斜裂缝的形成和发展予以监测。试验结果表明：试件最终破坏形态受重剪比和配筋率两因素共同影响;重剪比相同的试件,配筋率的提高也可有效提高中柱节点对不平衡弯矩的承载力;板内斜裂缝在节点发生冲切破坏之前已产生,并从靠近柱头的受压区向板底受拉区开展。基于试验结果和历史试验数据,将中国规范GB 50010—2010所采用的基于偏心剪应力模型的计算方法和欧洲规范Eurocode2-04进行对比,分析了偏心剪应力模型不足的原因。     

Finite Element Analysis of the Effects of U-wrap Anchorages on RC Beams Strengthened with CFRP Sheets

Premature debonding between CFRP and concrete commonly occurs in RC beams strengthened with CFRP sheets. U-wrap anchorages installed at the ends of CFRP sheets or along the entire beams are currently well accepted for preventing the debonding failure in engineering practice. Three schemes of CFRP strengthening beams without U-wraps, with U-wraps at CFRP ends and along the entire beam are numerically studied. The loading capacities and deflections of the beams, bond-slips in the interfaces and strains of CFRP sheets in the three cases are compared under different loading levels. The result shows that the strength and stiffness of the strengthened beams are effectively improved with the clamping of U-wraps. After the yield of steel reinforcement, U-wrap anchorages along entire beam are more effective for preventing the debonding failure than those at CFRP ends and lead to the uneven strains of CFRP sheets as well At the ultimate state,CFRP can rupture locally at the places of high strain concentrations leading to decrease in the loading capacity compared to the beam anchored at two ends of CFRP.     

Seismic Tests and Pushover Analysis of Spatial RC Frame-Shear Wall Structures

Pseudo-static tests of three one-storey spatial RC frame-shear wall structures with floor slabs were conducted to investigate their failure modes and hysteretic behaviors. The test results were compared with those of pushover analysis. It is shown that: 1) damage of the frame beams occurs later and is less than that of the shear wall and the frame columns; 2) damage of the floor slabs under lateral loading is significant in regions close to the shear wall, and tensile stresses of slabs' steel bars in these regions are much larger; 3) in comparison with the case that the floor slabs are neglected, the maximum lateral load that a frame-shear wall structure can bear is larger in the case that the floor slabs are taken into account, and the contribution ratio of the shear wall also increases; 4) shear forces carried by the frame columns with identical cross sections and reinforcement details but located at different positions are close to each other on the whole.     

农户模型中生产专业化的动态分析

在农业领域,明确的产业分工依然没有出现,农户为主的生产模式依然占主要地位。为研究农业生产的农户生产模式,运用动态分析的方法,从生产的角度对于农业生产进行分析。笔者将生产主体分为劳动密集型与资本密集型的农户,这样就实现了全面的专业化分工,并运用最优控制理论与Bellman方程分析专业化生产下的农户的最优增长路径,分析农户在动态生产过程中的选择行为。同时,从要素供给的角度分析农户生产模式无法专业化的原因。基于上述分析,认为农户的专业化生产是实现资源最优配置的最优路径,而专业化生产的失业风险,是导致农户无法成为劳动与资本2种要素生产者的主要限制因素。     

成孔机构与土壤相互作用的力学模型及应用

为实现油菜移栽机成孔机构形成满足农艺要求的栽植孔,并为设计新型移栽机提供理论依据,针对不同类型土壤具有不同物理机械力学特性等问题,进行成孔机构与土壤相互作用力学试验研究。分析土壤极限抗剪承载力Qu与土壤摩擦阻力Qf的计算公式,建立成孔机构与土壤相互作用的力学模型,完成不同类型土壤的物理机械力学特性指标的测定,结合成孔机构相关结构参数,求解圆柱形孔刺垂直刺入土壤75cm处所受抗剪阻力Ff1与垂直弹出土壤时所受摩擦阻力Ff2,得出圆柱形孔刺在不同类型土壤中,其抗剪阻力Ff1最大值1139.7N,摩擦阻力Ff2最大值达到107.6N。该研究为设计栽植孔成型机构提供了试验依据,为进一步研究不同类型土壤与成孔机构的阻力提供了理论依据。