Effect of Shear Lag on Structural Behaviours in Indeterminate Box Girders

A finite element method considering interaction betwee bending and shear lag deformation was proposed and the finite element formulations including the effect of shear lag was deduced. The effect of shear lag on structural behaviours in indeterminate box girders was studied in detail based on the proposed method. Firstly, the shear lag effects on deflection and the shear lag coefficients were analyzed for both determinate and indeterminate beams. The results obtained by using the proposed method were compared with those by using the analytical method. Finally, the effect of shear lag on redistribution of internal forces including shear force, bending moment, and additional bending moment due to shear lag in indeterminate box girder bridges was studied. It is found that the effects of shear lag on deflection and stresses at a cross section are obvious for both determinate and indeterminate beams, while the effect of shear lag on internal forces in indeterminate box girder bridges is small and may be neglected.     

Calculating the Support Reaction Increment''s Correlation Equation of R.C Continuous Beams

According to the hypothesis of plain section and the equation of moment versus curvature of R.C section, the elastic-plastic response of pressed continuous beams is analyzed with CDC-method. The correlation equation of support reaction increment and displacement increment is induced through the relation of moment increment and curvature increment,and the adjustment value of support reaction increment of continuous beams is determined by solution of linear equation systems,which provides a rule the support reaction to follow. It can roundly and quantificationally display the moment redistribution behavior of continuous beams. A case of 4 spans continuous beam shows a high calculation rate and precision of this method.     

Experimental Investigation of "Column with Weaker Beam" Frame and "Column with Equally Strong Beam" Frame

By the way of experiment and analysis of two "one story and one bay" reinforced concrete frames, namely a "beam with weaker column" frame and a "column with equally strong beam" frame, the features of internal force redistribution are investigated and an elementary comparison about bending moment redistribution of three kinds of frames namely the "column with weaker beam", "beam with weaker column" and "column with equally strong beam" is given. Through this comparison, the objective existence of such "three kinds of frame" is proven, the moment redistribution is different for each frame and for the moment modulation, the elastic moment diagram and the difference of the internal force redistribution in different frames should be considered together.     

Suggestion for Moment Modulation of Prestressed Concrete Continuous Beams

Based on the information from China and overseas,a design suggestion for moment modulation of post-tensioned prestressed concrete continuous beams with bond has been put forth in this paper. The result calculated by the suggestion is consistent with the result of varying rigidity method.     

Experimental Study on a Prestressed Frame of Two Spans Under Unsymmetric Load

By the experimental study on a full-dimensioned prestressed frame of two spans, the relative factors are analyzed such as relative height of equivalent compression zone in critical section, secondary moment, ratio of beam rigidity to column and development of cracks in the top of columns etc., which influence the moment distribution of the post-tensioned prestressed concrete frame from the side of internal force redistribution. It is believed that that the factors of relative height of concrete equivalent compression zone and secondary moment influence the moment modulation in most degree, and ratio of column rigidity to beam also plays a part in the moment modulation to some extent. Second, the plastic joints of frame with excessive spans exit in the span which endure the whole load, at last the whole frame is destroyed because of the destruction of the loading frame, the influence to the non-loading span is little.     

Experimental Study on Moment Modulation of Prestressed Frames

Based on the experimental study of two prestressed frames in redistribution of Internal force, it can be concluded that the dominating influence factors on moment modulation are the relative height of equivalent compression zone, the secondary moment, the ratio of beam rigidity to column and development of cracks in the top of columns.The secondary moment is very important in modulation of frames. Especially, the secondary moment will governing the modulation when the relative height of equivalent compression zone is large enough.     

Analysis Theory of Unbonded Prestressed Concrete Continuous Beams

In this paper, the energy method has been used to study the change of the secondary moment of unbonded prestressed concrete continuous beams and it has been contrasted with bonded prestressed beams. The question, whether the secondary moment changes or not while loading, was answered. It shows that the primary secondary moment does not change when increment method is adopted to study the beams, but the total secondary moment will change while the force in prestressed reinforcement changes.     

Discussion on the Secondary Moment of Prestressed Frame

The secondary moment of prestressed concrete frame is different from that of continuous beam. In this paper,the principle and calculation method of equivalent load secondary moment and axial secondary moment are discussed,and the infection of secondary moment in moment modulation is analyzed,together with the suggestions of moment modulation for prestressed concrete frame with adopting the total control. The suggestions would be able to distinguish the advantageous and disadvantageous effect of secondary moment. Some helpful advises for moment modulation design are given in this paper.     

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.     

THE CALCULATION OF INTERNAL FORCES AND DISPLACEMENTS IN FRAME-SHEARING WALL STRUCTURE UNDER THE HORIZONTAL LOADS

In general,the calculating result of a comparatively regular frame-shearing wall system in tall buildings,a 4-order differential equations are established according to the deformation-coordination of beams,columns and four boundary conditions.Then a series of formulas concerning internal forces and displacement is obtained These formulas are hyperbolic functions.This paper presents a method,which changes 4-order differential equations into 2-order and solves them by the expressions of new homogeneous solutionThen the formulas of internal forces and displacements become exponential functions By this method,the calculation is very convenient The result of suggested method agrees well with the general by comparison This paper is also applicable to buildings with some part of different height of storey or stiffness.     

BENDING PROBLEM OF RECTANGULAR PLATES STIFENED ALONG ONE DIRECTION UNDER LOCAL LOADS

By using mixed triangle series,this paper discusses the calculation of rectangular stiffened plates with simply supported edge along direction of stiffeners under several local loads,such as uniform load on local rectangular area,concentrated force,concentrated moment of couple,line loads,line moments of equal and some equivalent concentrated forces acting on a line with equaldistance among them.All analytical solutions of both displacements and internal forces are derived.A numerical example to treat an engineering problem is given.     

Comparative Study on Plastic Hinges of Prestressed Concrete Frames Under Vertical or Horizontal Loads

In With one-storey, two-span prestressed frames, a comparative study is done between under vertical and horizontal loads. The studies include the pattern of the plastic hinges occurring and, the demanded and available rotational capability of the hinges in critical sections. The relative height of compression zone and prestressed degree are considered. The result indicates that there is much difference in the pattern of the plastic hinge occurring when each plastic hinge has enough rotational capability. The beams can finish a full redistribution of internal force under vertical loads, but not under horizontal loads. Moreover, as increasing of the relative height of compression zone, a stronger rotational capability of hinges will be demanded to finish a full redistribution under vertical loads when a weaker rotational capacity will be needed under horizontal loads.     

AREA-VECTOR METHOD CALCULATJJNG THE DISPLACEMENTS OF BEAMS AND FRAMES

A new method with which to calculat the displacements of beams and frames is presented. The areas of tending moment diagram of beam or frame and the slope at the origin of the elastic curve are treated as some rotatable vectors with this method. Angular displacement and in-line displacement can be calculated by using the projection and moment of these vectors. This method can be used to calculate displacement of the bar and the bar syttem ( including three dimensional forms. ) , which made from linear or ncnlinear elastic materials. The cross section of the bar is changeable.     

Dynamic Response Analysis of High-rise Pile Cap-soil-structure under the Wave and Earthquake Action

Finite element software was used to simulate the internal force and deformation of high-rise pile cap-soil-structure under the wave and earthquake action. Meanwhile, wave force was calculated by using Morison equation, and the mechanical behavior of structure was simulated by inputing horizontal El-Centro wave. Then, the initial state and the state of the largest positive and negative acceleration were selected to study the structure according to the time history curve, and the displacement, bending moment, shear and axial force changes of pile foundation under wave and earthquake action were discussed, which was compared and analyzed with the structural response under the action of earthquakes solely. The result shows that the moment of front row of piles is biggest, and the force of pile bolck is the most dangerous; the axial force of the corner piles is the largest, and one of the center piles is the smallest under the action of wave and earthquake. When the wave forces and seismic forces are in the same direction, the displacement, moment, and shear force of pile bolck will be increased, on the contrary, the displacement, moment, and shear force of pile bolck will be decreased.     

Experimental Analysis on the Mechanical Properties of Concrete Composite Slabs with Precast Prestressed Rectangular Rib Panels

For the convenience of industrialized production and site operation,specification design of PPCRP (precast prestressed concrete ribbed panels) is discussed. In order to obtain ultimate bearing capacity,bending rigidity and crack resistance,four PPCRP with two types of spans are studied,and the results show that PPCRP can satisfy the requirements of bearing capacity in construction phase and can serve as stay-in place formwork. To verify the mechanical property,shear behavior on contact interface of composite member and moment redistribution factor of continuous composite member,two single-span composite members and one two-span continuous composite member are studied. It is indicated that computational method for bearing capacity of composite member can be the same as cast-in-situ concrete slab. Besides,section strain analysis for composite member in two-loading is conducted,which suggests that thickness of bottom board can be used as calculated height with the consideration of two-loading.     

Section Optimization Design of Steel-Concrete Continuous Composite Beams Based on the Finite Element Method

This paper introduces the efficient computer aided design method to optimize the section of steel-concrete continuous composite beams by combining FEM for structure analysis with optimization arithmetic and an efficient shearing force link model of steel-concrete composite beams.The authors established a finite element analysis model,optimization parameter model,optimization mathematics model of steel-concrete continuous composite beams and programs analysis file and optimization control file by using the ANSYS parameter design language. The optimum of the steel-concrete continuous composite beams section is obtained after computing and the optimization result indicates that this method is efficient in optimizing the section of steel-concrete continuous composite beams.So it could be applied extensively in the steel-concrete continuous composite beams section optimization design.     

A Method of Plastic Ultimate Analysesfor RC Waffle-slab Structures

In order to calculats the ultimate load of a Waffle_slab structure with the method of plastic analysis,this paper supposes the structure as a virtual isotropic plate of structural orthogonal anisotropic plat es.The formulations of the ultimate moments distribution between the virtual plate and the virtual beams are deduced.The virtual work of the internal forces can be figured out easily under the given failure mechanism models,and then the ultimate load of the structure can be determined according to the virtual work principle.     

STATIC ANALYSIS OF THE BODY OF MAN''S DRY GAS HOLDER WITH A VOLUME OF 120000m~3

This paper presents finite element calculations of the body of MAN'S dry gas holders with a volume of 120000m~3 under internal pressure and wind load. The analyses of displacements and internal forces of the body are presented. The control points of strength and rigidity check are determined. The work in this paper is very valuable to body's design.     

Test & Analysis of Moment-Torque Distribution Between Spandrel Beams And Beams of Floor System With P.C. Long-span Beams

The test of four large scale specimens of floor system with P.C. long-span beams is introduced.The restraining torsional moment of spandrel beams caused by P.C. beams with or without slab is focused on,along with change of the load-torque relationship affected by the beams' bending rigidity and the spandrel beams' torsional rigidity under different load level. The result presents important reference to the revision of national design standard and structural design.     

Calculation and Analysis on Critical Moment of Thin-walled Beams under Unequal End Moment

In this paper, comparing the bending-twisting model with the tension-bending one, the critical moment of the thin-walled beams under unequal end moment is derived easily by the improved CDC (column deflection curve) method based on the increment interaction equations of beam-columns.A simplified formula is presented and the calculated results show a good agreement with the numerical ones.