Steel pipe integral girders for constructing prestressing force and construction method thereof
Belongs to the technical field The invention relates to a building truss and its construction method, in particular relates to a prestressed steel pipe whole truss and its construction method. Background Art In in a modern building, to steel pipe is a steel truss member, because of its bearing capacity is large, flexible arrangement, convenient construction, has been widely applied to large SPAN and the large cantilever structure, in the structure of the transfer beam. At present, the plane truss member rigid connection and nodes are divided into two forms. When a hinged node, for plane truss static structure, means has no redundant constrained geometry unchanged system, only one line of defense, damage as long as there is a pole piece, the collapse of the instant structure, the consequences would be unthinkable; when a rigid connection node, although truss are still statically indeterminate structure, means to have redundant geometric unchanged system, but if we want to ensure that the truss structure in a bar or node at the time of destruction, can still have a certain ability of plastic deformation, without is instantaneously collapse, the truss in bearing capacity and rigidity of the rod needs to be improved greatly, the production cost is increased, resulting in great economic burden. In particular in large SPAN suspension structure, the more conspicuous this problem. Furthermore, plane truss bar node whether hinged or rigid connection, considerable deformations of the truss, but the integrity of the just met more conducive to the anti-knock and coordination stress and deformation; the truss member in stress is of the bar is not the average, while very large, a very small one, even for zero member , but also the waste of material. Therefore the popularization and the application of a greater or lesser extent, subject to certain restrictions. To sum up, the ordinary rectangular steel truss has the following defect: (1). The node of the static structure, without safety reserve; (2). The rigid connection node, need for great economic inputs for the smaller will be the price of the security reserve; (3). Individual rod stress is very large, and is almost zero member individual member, causing local pole piece section is large and a plurality of material; (4). Rigid connection of the node is more difficult to achieve, often because of node truss the deformation of the deformation of the whole is increased. Content of the invention The purpose of this invention is to provide a prestressed steel pipe whole truss and its construction method, the whole truss is a steel, concrete, prestressed steel truss system combined with a plurality of materials, the bearing capacity and rigidity of the truss, and through a relatively small economic investment for the truss systems provide a secondary line of defense. The technical scheme of the present invention can be realized through the following measures: a prestressed steel pipe whole truss, the truss component of the composition of the tension member and the node, the rod member includes upper chord, the chord and web members of the lower chord; which is characterized in that the and of the truss is connected with the pull rod in a node of a prestressed steel strand is provided with at least one beam, the two ends of the prestressed steel strand are respectively fixed on the truss is connected by pull rod member and the node of the two ends of the tension, in the truss is connected by member bar and the nodes of the pouring the concrete. Upper chord of the truss, the last quarter of the chord member and web member can be a circular cross-section or rectangular cross-section, such as of steel pipe. The node is a "K" type node, that is, an upper, the lower chord between the chord and the web members by the "K" type node is connected, the "K" type node of the vertical-side horizontal arrangement, is connected with the chord ;-type node "K" of the bevel edge of the web member is connected is inclined; connecting the nodes of the bar is driven through the prestressed steel strand of the hole, the hole is set on the leads close to the port of the node where the stiffening ribs of the at. General, two leads into a group of holes, is located in the vicinity of the second port in the node, in the node are respectively used as the strand into the hole and a delivery hole, according to the different position of the node, into the holes and the delivery hole can be flexibly arranged, not only can be arranged on the horizontal rod of the boom is connected with, but also can be connected with the chord are respectively set at the level of the rod member and the tilt member in the web member is connected. The invention can be improved as follows, connecting the nodes of the bar can also be provided with a lead pipe, the two ends of the drag line tube are respectively fixed in the node at the second end of the stiffening rib in the hole of the lead, so as to be more convenient to wearing is installed prestressed steel strand, according to the shape of the truss is drag line tube steel strand in the direction of the design of the determined, can be a linear, can also be arc shape; the node drag line tube can also be provided with a support rib used for supporting, in order to increase the structural strength, the supporting rib which is arranged at the upper end of the tube section to adapt to the outline of the supporting groove. This invention is in the truss is arranged in a rectangular steel tube of prestressed steel strand, the use of the prestressed steel strand tension, the reverse-form a truss structure, and the concrete is poured into a rectangular steel tube, the steel pipe concrete and the tension of the steel strand, greatly improve the bearing capacity and the rigidity of the truss rod. When the truss steel close to Modei damaged, because the steel tube of rectangular cross-section of the compression resistance property of concrete member is good, and strong tensile property of prestressed steel strand, is provided with a filling of concrete of prestressed steel strand to be capable of forming a kind of steel pipe member pole rope structure system, as a secondary line of defense of the truss. The following improvements can be made of this invention, when the invention is used for when the cantilever structure of the truss, the truss upper chord tension, the lower chord pressed, the prestressed steel strand in the upper chord of the truss is set on, in other words is set up in the first quarter boom and the node of which is connected with the; and pouring the concrete for the part of the bottom chord of the truss web members and pressure, that is, the last quarter of the chord, node and pressed web member. The invention can also be made the following improved, when the invention is used for the transfer beam large-SPAN structure and when in the structure of the truss, the contrary force of the cantilever structure, the truss upper chord pressed, the lower chord tension, the prestressed steel strand in the bottom chord of the truss is set on, in other words is set up in the last quarter of the boom and the node of which is connected with the; and pouring the concrete for the truss upper chord of the part of the web and is pressed, that is, the first quarter chord, node and pressed web member. Because of the large SPAN structure, the compression of the web members of the truss upper chord with the internal force of the chord is much smaller compared with, in order to reduce the weight of the structure itself, pouring the concrete can also be only the part to the pressure the first quarter chord and node. The invention can also be made the following further improved, when the truss of the invention is used for a large-scale suspension structure, the symmetry of the truss, the truss is out of a structure of the two ends, wherein the stress condition of the cantilever portion of the truss with a common cantilever similar structure, that is, the upper chord of the truss tension, the lower chord pressed, the prestressed steel stranded wire can be arranged on the upper chord of the truss, and the pouring of the concrete and the lower chord of the truss web being pressed. For truss of the invention in large-scale suspension structure, when the size of the cantilever portion of the truss is relatively small, its midspan large-SPAN structure similar to stress conditions, that is, the upper chord of the truss is pressed, the lower chord tension, at this moment, the prestressed steel stranded wire can be arranged on the lower chord of the truss; and pouring the concrete for the truss upper chord of the part of the web and is pressed. For truss of the invention in large-scale suspension structure, the large size of the truss when the cantilever, the cantilever portions than during the stress of the greater part of it, at this moment in order to balance the moment generated by the cantilever portion, in addition to the lower chord of the cantilever portion of the truss web being pressed and pouring the concrete into the outer, part of the casting of the concrete can also include non-cantilever portion of the midspan of all components of a part, in order to increase the weight and the rigidity of the middle step. Furthermore, the truss can be prestressed steel strand is the upper chord length, symmetrical stretching, in this way, a symmetric truss may also be against the deformation of the deformation, its prestressed load can be used as a restoring force, just like a human balance of the two shoulders for a thread, the two shoulders "shoulder" play between the deformation and the coordination of the role of the vertical vibration is reduced. The application of the invention-the whole truss construction method of a steel pipe, comprising the following steps: (1). First using steel into a pipe member, the member includes a rod and a node, the rod member includes, chord and web member of lower chord, the prestressed steel strand drag line hole reserved in the node, device reserved in the concrete pouring hole; (2). Then utilize the reserved drag line hole in the tensioned bar and of prestressed steel strand in the node, the required stretching of steel, and to the pressed rod and node pouring concrete. The step (1) in, can also be reserved in the node which is between the holes of the pipe leads, the step (2) in, which the tube is steel. When allowed by the construction conditions, complete the step (1) then, in the step (2) in, first the use of prestressed steel strand drag line hole according to the truss through the assembling order of the truss in the pull rod member and a node, then the all components assembled to form steel truss, and according to the design requirements to the prestressed steel strand tension once or several times, finally, a concrete pouring hole to the pressed rod and node into the concrete. When the conditions do not permit of construction, the step (1) in, the reeving reserved in tension of the hole, the hole in which the reserved in the node only, and no lead in the hole, to ensure that the construction of the prestressed cable through the entire truss can be smoothly arranged reeving hole needs to be left, the step (2) in, the first according to the design requirements of all components assembled to form steel truss, re-use of the technological holes drag line hole and reeving through the prestressed steel strand and of the truss in the node by the pull rod. The construction method of this invention for the cantilever structure, the tension the upper chord of the truss, the lower chord pressed, in the step (1) in, reserved in the truss top chord node hole leads, and at least at the bottom chord of the truss web being pressed in the boom and reserved concrete pouring hole; said step (2) in, conjunction with the hole in the first quarter chord of prestressed steel strand passes through the inside of the and node, the required stretching of steel, and to the lower boom, node and pouring the concrete into the pressed web. The construction method of this invention applied to the large-SPAN structure and conversion beam structure, the stress situation of the truss opposite the cantilever structure, the upper chord of the truss is pressed, the lower chord tension, therefore, in the step (1) in, the reserved in the bottom chord of the truss which the node of the hole, and the upper chord of the truss boom, node and pressed concrete pouring hole in the web; the step (2) in, which is reserved in the lower chord of the boom and of prestressed steel strand passes through the inside of the node, the required stretching of steel, and to the first quarter chord, node and pouring the concrete into the pressed web. The construction method of this invention applied to the large-scale suspension structure, wherein the cantilever portion of the cantilever structure is similar to the ordinary situation, the corresponding, construction method of the cantilever portion of the truss can be the same as with ordinary cantilever structure, that is, the arrangement of prestressed steel strand and concrete casting part of the same the cantilever structure. When the flag in the structure of the size of the cantilever portion of the truss is relatively small, its midspan large-SPAN structure similar to stress conditions, construction method can be of the truss structure with large SPAN of the truss in the same method of construction, the arrangement mode of prestressed steel strand and concrete casting part and a large-SPAN have the same structure. When the flag in the structure of the size of the cantilever portion of the truss is relatively large, in addition to the lower chord of the cantilever portion of the truss boom, node and the pouring the concrete into the pressed web, can also be in a non-cantilever portion of the spring during the pouring of the concrete, in order to increase the weight and the rigidity of the middle step. Compared with the prior art, the advantage of this invention is to: (1). In the invention, the rectangular steel pipe member, of prestressed steel strand, concrete is poured into the partial rectangular steel tube three combination, fully utilizes the characteristics of the above-mentioned three kinds of material, the combined into a kind of than conventional steel truss good rigidity, high bearing capacity of the novel combined truss; (2). Local truss of the present invention is a rectangular steel tube concrete component, is to use thick steel plate coated concrete, under pressure, because the rectangular steel tube of the constraint action of the concrete, thereby effectively improving the rectangular steel tube and the bearing capacity of the concrete member; (3). A truss of the present invention due to the increase of in-prestressed steel strand of a pre-stressed component, the presence of the, effectively reducing the truss is pulled the stress in the component; (4). The pressure member of the present invention in concrete material of the bearing capacity of the girder, there is a great ability of plastic deformation, and the prestressed steel strand of steel pipe member, than the conventional steel bearing capacity of several times, and the deformation capacity is very large, when the truss steel a rectangular steel tube damage Modei close to the first, because the rectangular cross-section of the whole truss system of good performance and compression of the concrete component the steel articulation line anti-pulls performance, by forming the a new pulls the intensity of pressure assembly, thereby forming a secondary line of defense; (5). The present invention is applied to the truss on the large-scale suspension structure, because the vertical seismic power in response to the large influence structure, effectively reduces the pre-stressed as a restoring force in the vertical structure deformation under earthquake effect, is of great significance for the security structure. In order to this invention is applied to the suspension structure, for example, through the following test examples further demonstrate the effect of the invention 1. Applying prestress of the invention the overall truss to the suspension structure when in use, directed against different prestressed and concrete arrangement of calculation, analysis and comparison (1). Calculate the total description The integral calculation to calculate ETABS MIDAS/GEN and, in the computation requirements can be accurately simulated structure itself, can be prestressed to be considered in the overall calculation, temperature effect, the construction sequence the influence of the structure; in addition to obtain the stress performance of the truss and the working state of the stress distribution of the composite cross section of the, to the truss of the calculation of the overall analysis of the ANSYS. Truss ≤ 35 mm in the steel sheet adopts Q345C, > 35 mm using GJC345, the strength grade of the concrete truss of C60. Is calculated according to the actual cross section, comprises a steel structural member, rectangular steel tube with prestressed concrete member and the member, and the truss steel, high-strength concrete pouring of the truss and the prestress already exert high-strength concrete and pouring the computational comparison of the truss. Figure 20 the overall computation model of a suspension structure, shown by an arrow in the Figure for the actual prestressed member. (2). Compared with the result of calculation MIDAS/GEN, the result of calculation and ANSYS ETABS although different, but the difference is relatively small, and the three different situations the result of the calculated contrast the difference are not many. Calculate the MIDAS only here is given a certain independent of the result of calculation of the truss. Table live load displacement value are dead load and the vertical displacement of the combination of. Pouring concrete with-and-aft displacement results (mm) table 1 Restressing back and forth displacement results contrast (mm) table 2 Restressing the front and back of the truss is compared with the maximum stress (MPa) the results of table 3 Furthermore, according to the results of the time course of MIDAS analysis and calculation, taking into account after the pre-stressing of the recovery function, structure under the function of an earthquake in a vertical direction to reduce the displacement of about 10%. (3). SUMMARY As can be seen from the result of the calculation, the rigidity of the truss of the concrete is greatly improved, reducing the deflection of the cantilever end of the 20% the left and right; and after applying prestress can not only reduce the deflection of the cantilever end, can be more effectively reduce the tensile stress of the rod member. Through the pre-stressing force in the pull rod and to pressure the concrete is poured into, greatly improve the loading capacity and rigidity of the truss, the truss provides greater safety reserve. 2. Restressing part of the rectangular steel tube concrete cantilever truss to the suspension structure when in use, directed against different prestressed and concrete arrangement of the single truss test comparison (1). Experimental overview (1). Test purpose Research in static load under the action of the structure of the stress, deformation characteristics, the breaking load of the structure is obtained, and the stress distribution of the damage mode, each node and the study of the role in the static load the mechanical performance, the force-transmitting mechanism, stress, and strain distribution and deformation of the situation, the limit structure and static bearing capacity and damage shape; according to the structure of the bearing performance and the damage, comprehensive judgment the weak part of the structure, such as test design calculation results, the steel structure design for an integrated analysis and assessment programme. (2). The design and manufacture of the test piece Model from the actual engineering, according to the 1 [...] 7 is the proportion of the, is mainly composed of the middle and the two ends of a double-cantilever truss out, loading device, such as a three-part support, wherein the truss is formed by the rectangular cross-section of the boom and a web member. A total of two independent of the truss the test, one of the independent truss according to the design requirements is the upper chord 4 φ 15.24, in other words 4 root φ 15.24 high-strength of prestressed steel strand (fptk=1860N/mm2), and the two independent of the truss structure are in the symmetrical half of the concentrate according to the design requirements of the cement mortar, of prestressed steel strand 4 and filling cement mortar 5a specific arrangement of Figure 21. The steel of the test piece Q235B, the mortar grouting of the M20 the blending proportion of the mortar, and adulterating 5% of the bulking agent. Grouting hole in the laboratory site spud in, mortar of the vibration device ensures that; the prestressed zhang La in carried out in the laboratory, to control tension each prestressed reinforced 82kN. (2). Loading method and test method (1). Loading method In the experiment 4 a of the loading point loading means exerting load at the same time, loading a schematic diagram as shown in Figure 22. The test in a three cycle of unloading loading mode, after reading in the stability of the load. Test design load for the end node P1 = P4=270kN. 1st time loaded to the first P1=P4=270kN, inspection can meet designed bearing capacity of the structure, then unloaded to 0 ; 2nd time of loading to the design load of 1.5 times, in other words P1=P4=400kN, then unloaded to 0 ; 3rd time the ultimate bearing capacity was to study structure, has been loaded into the structure to be damaged and, subsequently unloaded to 0. Yield a steel plate the test piece 50kN each level of the loading speed, to yield of the steel plate after each stage 25kN the loading speed, according to the test piece at the same time to adjust the actual situation. In plan, P2, P3 is due to the deformation of the structure stress, the resulting load. (2). Test content and method The main elements of the test include: measuring at all levels of the test piece under the action of loading and horizontal deflection of the lateral displacement; determining every component of the test piece under the action of loading at various levels of strain; determining the strength of the test piece. Test using BX120 resistance strain gage test component strain, displacement of the displacement test dial test indicator, DH3816 for, DH3815N static data acquisition system for the automatic acquisition all levels of load and displacement data of resistance should be variable. Specific arrangement as shown in Figure 23, end node is provided with a 33 × 2=66 sheet should be variable, is provided with a the nodes in the 30 × 2=60 sheet should be variable, chord member is provided with a 40 × 2=80 sheet should be variable sheet, web member is provided with a 12 × 2=24 strain gauges, supporting seat is provided with a 2 piece should be variable, displacement totaling 12 a, the total measuring point 244 a. (3). Test results (1). The deformation of the component after applying prestress characteristics After tensioning pre-stress, the whole truss scragging, deformation of the two suspension arm end of the trend is upward, the middle part of the deformed down. Displacement specific measured points shown in table 4. Because the "shoulder pole effect", tightening directly transmitted to the support web, after the pre-stressing the overall deformation is not obvious. Prestressing of deformation measured value table 4 (2). Destroy process and characteristics Non-prestressed of the test piece in the test process, the concentrator, position for details sees the chart 24 : 2nd grouting test piece cantilever at a 2nd upper chord and which is connected with the top chord node brittle fracture takes place in the weld seam, the weak area of the test piece; non-grouting test piece lower chord of the cantilever at a 3rd and 2nd root node of the web plate of the lower chord adjacent the seat and the partial-flex, the two sides of the outermost support the flexing deformation of the additional steel, at this moment, the carrier strain is large, the yield has been reached. Restressing of the test piece in the test process, there are also two concentrator, position for details sees the chart 25: support and the truss the connection part of the welding seam damage, the damage from inside to outside in sequence, finally only the remaining one of the outermost connecting with a truss support, form a simple support; 2nd from the outside to the inside of the upper chord-destruction of the weld bead, this is by the inner of two prestressed the muscle is curving , the test piece, in order to bend in a small angle opening in the prestressed high flow uniformity, and then welding to fill, can be known by the strain of the upper chord, an indication of the stress-strain is large, is weak part of the test piece. (3). Bearing capacity analysis Test piece measured ultimate bearing capacity as shown in table 5 is shown, we can see that the grouting and the limit of the test piece after applying prestress, the bearing capacity can be improved by 10% the left and right. Test piece bearing capacity table 5 (4). Deflection analysis Table 6 to an end of the corresponding load value , pre-stressing can be seen after the grouting and, in the design of the test piece under the action of loading can be respectively reduced deflection of the 20% the left and right. Since each different ultimate bearing capacity of the test piece, the deformation when the bearing reaches the limit of no practical significance. Load deflection value corresponding to the key 6 (5). Contingency analysis For non-grouting test piece, the position of the strain is on the cantilever of the root of the wing edge of the lower of the lower chord, corresponding to the position of the limit load occurs when the local flex the web; for grouting test piece, strain is at the position of the upper chord of the root of the cantilever, and achieve the maximum limit load should value less grouting of a truss to be small. Furthermore, prestress, in other words steel strand in the vicinity of the corner and anchorage place local stress-strain is large. (4). SUMMARY (1). Grouting and the limit of the test piece after applying prestress can improve the bearing 10% the left and right; (2). Grouting and restressing the deflection of the cantilever end point can be reduced 20% the left and right, and the residual deformation is relatively small; (3). After grouting to adjust the stiffness of the truss, the maximum strain position of the transfer bar from the lower to the upper chord pull rod, and achieve the maximum limit load less grouting should be variable to the truss; (4). The prestressed near the corner and anchorage place local stress-strain is large; (5). Applying prestress in the pull rod by the pressure of the concrete and to the filling, can greatly improve the loading capacity and rigidity of the truss, for the truss to provide greater safety reserve. Description of drawings Figure 1 is the whole truss schematic diagram of the embodiment of the invention 1 the applied pre-stress; Figure 2 is enlarged a schematic diagram of the embodiment of the invention 1 in the overall truss drag line hole and reeving process hole; Figure 3 is enlarged a schematic diagram of the embodiment of the invention 1 in the overall truss concrete pouring hole; Figure 4 is enlarged a cross-sectional view of the embodiment of the invention 1 the node 7; Figure 5 is the amplifying a perspective view of the embodiment of the invention 1 the node 7; Figure 6 is the amplifying a cross-sectional view of the embodiment of the invention 1 the node 8; Figure 7 is enlarged a perspective view of the embodiment of the invention 1 the node 8; Figure 8 is the amplifying a cross-sectional view of the embodiment of the invention 1 the node 9-11; Figure 9 is enlarged a perspective view of the embodiment of the invention 1 the node 9-11; Figure 10 is an amplifying a cross-sectional view of the embodiment of the invention 1 the node 12; Figure 11 is an amplifying a perspective view of the embodiment of the invention 1 the node 12; Figure 12 is an amplifying a cross-sectional view of the embodiment of the invention 1 the node 13; Figure 13 is an amplifying a perspective view of the embodiment of the invention 1 the node 13; Figure 14 is an amplifying a cross-sectional view of the embodiment of the invention 1 the node 14, 16; Figure 15 is an amplifying a perspective view of the embodiment of the invention 1 the node 14, 16; Figure 16 is an amplifying a cross-sectional view of the embodiment of the invention 1 the node 15; Figure 17 is an amplifying a perspective view of the embodiment of the invention 1 the node 15; Figure 18 is the overall truss schematic diagram of the embodiment of the invention 2 the applied pre-stress; Figure 19 is a schematic diagram of the embodiment of the invention 2 in the overall truss hole leads, reeving process hole and concrete pouring hole; Figure 20 is a schematic diagram of the overall calculation model suspension structure test example of the present invention; Figure 21 is a schematic diagram of a specific arrangement of the invention and of prestressed steel strand experimental example filling cement mortar; Figure 22 is a schematic diagram of load point of the truss the test example of the present invention; Figure 23 is a schematic diagram of measuring point arranged truss stress-strain test example of the present invention; Figure 24 is a schematic diagram of the position of the test piece destruction of the invention test example of a truss non-prestressed; Figure 25 is a schematic diagram of the test piece destruction position of a truss of the present invention test example of applying the pre-stress. Mode of execution Embodiment 1 The embodiment of the invention 1as shown in Figure 1-17, in this embodiment, the application of the invention the whole truss is of prestressed steel pipe used for large SPAN suspension structure of the main stress truss, the truss member including a rod and a node, the member 1, the lower chord 2 boom 1a, 2a and the web 3, the bottom chord of the truss 2 are also arranged below the cantilever support 6. The upper chord of the truss 1, the lower chord 2 boom 1a, 2a and web member 3 are rectangular cross-section steel pipe; winding 1, the lower chord 2 boom 1a, 2a and the web member 3 and a "K" type node is connected, the "K" type node of horizontally arranged vertical side, and the chord 1a, 2a are connected; "K" of the two-type node of the web members with the inclined bevel 3 ;; connecting the nodes of the bar of prestressed steel strand is 4 hole passing through the leads, the node where the hole is set on the leads close to the at the end of the stiffening rib 25 on. Two leads into a group of holes, is located in the vicinity of the second port within the node, as a steel strand respectively 4 in the node into the hole and the guide hole of the, not only can be arranged on the horizontal rod connected to the chord, and can be respectively with the chord 1a, 2a the horizontal bar and is connected with the web member 3 of the is connected with the tilt member. Connecting the nodes of the bar is also provided with a lead pipe 17, which pipe 17 are respectively fixed on the two ends of the second port in the node stiffening rib 25 which is in the hole of; the node drag line tube can also be provided with a support 17 of the support rib 26, the supporting rib 26 with the leads which is arranged at the upper end of tube 17 to the outline of the cross section of the supporting groove. The "K" type node of assembling the rectangular cross-section of a steel pipe. Of the girder which is connected with the bar and is provided with a prestressed steel strand in a node 4, of prestressed steel strand 4 are respectively fixed on the two ends of the truss is connected by pull rod member and the node of the two ends of the tension, and the device and of the truss which is connected with the concrete is poured in the node 5. Because the truss used for large-scale suspension structure, the symmetry of the truss, the truss is out of a structure of the two ends, wherein the stress of the cantilever portion of the truss with a common cantilever which is similar to the structure of the situation, but also because the upper chord of the truss 1 tension, the lower chord 2 is pressed, the prestressed steel strand 4 is arranged on the cantilever portion of the truss upper chord of the truss 1 in, and pouring concrete 5 of the part of the bottom chord of the truss to the cantilever portion 2 and pressed web member 3. And in this embodiment, the total length of the truss 113.5m, the midspan thereof 67.5m, the two ends of the cantilever 23m, high 8.0m, because the truss of the cantilever has a large size, the stress of the cantilever portions than during the greater part of it, at this moment in order to balance the moment generated by the cantilever portion, in addition to the lower chord of the cantilever portion of the truss 2 and pressed web member 3 pouring the concrete 5 outer, midspan non-bracket part of the part, that is, all components of a non-cantilever part of pouring the concrete 5. Furthermore, pre-stressed steel strand 4 upper chord of the truss 1 boom 1a and node 7-11 length provided in the, in this embodiment, two beams of the truss steel strand arrangement, one of the beam are respectively used for the two ends of the rivet 28 located in the bottom chord of the truss is 2 the node of the valve 12 in, the other beam are respectively used for the two ends of the rivet 28 is fixed to the and node 12 adjacent node 13 in, symmetrical stretching, in this way, a symmetric truss may also be against the deformation of the deformation, its prestressed load can be used as a restoring force. Node 7-11 drag line hole and leads in the concrete of the tube is set up as follows: Node 7 is located in upper chord 1 end, the node 7 in, a hole is provided with a pair of leads which, with the chord, respectively 1a and the horizontal rod which is connected with the outer side of the web member 3a in the inclined member is connected, between the two conducting rope hole which pipe 17 is located in upper chord 1 and web member 3a in the corner between, is arc-shaped. Node 7 is also used for supporting drag line tube 17 of the support rib 26, the supporting rib 26 with the leads which is arranged at the upper end of tube 17 to the outline of the cross section of the supporting groove. Node 8 and node 7 adjacent, in the node 8 in, is provided with two pairs of leads a hole, wherein a pair of respectively located at node 8 and two side chord 1a in the horizontal member is connected, between the two conducting rope hole pipe leads 17 to a horizontal straight line; the other hole are respectively located on a pair of leads with the chord member 1a and the horizontal rod which is connected with the web member 3b in the inclined member is connected, between the two conducting rope hole pipe leads 17 is arc-shaped, linear leads located in the tube 17 below the of the, web member 3b and the abdomen catches up with 3a adjacent, and are parallel. Node used for supporting an arc-shaped lead is arranged in the tube 17 of the support rib 26, which tube 17 is supported on the supporting rib 26 at the top end of, the supporting rib 26 with the leads arranged at the top end of the pipe 17 to the outer contour of the supporting groove. Node 8 is also used for fixing the linear-shaped lead pipe 17 of the support rib 27, which tube 17 can pass through the support rib 27, in other words, the quantity of a supporting rib 27 which is provided with a pipe 17 adapted to the outer contour of the cavity, so as to be its support. Node 9-11 have the same structure, are provided on its the horizontal rod is provided with two holes for the lead, the second lead pipe is horizontally arranged, an upper a lower, node in the middle of the set symmetrically to fix the two straight linear drag line tube support rib 27. Furthermore, in this embodiment, the cantilever portion of the truss upper chord node 7, 8 also pouring the concrete, is in order to guarantee the pressed web is connected with the 3 inner concrete can be poured and dense; the second is prestressed turning node to the node, in order to avoid the stress at the stress transfer concrete centralized pouring. In this embodiment, the prestressing of the whole truss construction method of a steel pipe, comprising the following steps: In this embodiment, the construction conditions do not permit, need to finish the steel truss manufacturing and assembling, then through the truss in prestressed steel strand, finally injecting high-grade concrete. Specific steps are as follows: (1). The first rectangular cross-section of steel material for the manufacture of steel pipe member a, member includes a rod and a node 7-16, rod member includes upper chord 1, the lower chord 2 boom 1a, 2a and the web 3, the prestressed steel strand 4 through node 7-11 drag line hole and the mounting lead reserved in the tube 17 ; this embodiment is a total of two beams of prestressed steel strand; the truss upper chord 1 boom 1a process hole is provided with a lead 18, the web of the steel strand 3a, 3b in the process of a small hole 18. In the last quarter 2 boom 2a and eliminates the web member 3a, 3b of the outside of all the web member 3 is provided with a concrete pouring hole 20. Furthermore, during the upper chord of the part 2 of the chord 2a and node 9-11 inner also been reserved for concrete pouring hole 19, 20, in addition, the upper chord node in the cantilever portion 7, 8 is also reserved in the concrete pouring hole 19. In all node 7-16 are reserved in class thick liquid hole 21, 22, so that the concrete can the stiffening ribs through the node, and the node, and the concrete web member area at the same time the full range of the whole node. Taken into account with large pulling force upper chord the cantilever portion, the brittle failure-prone weld rotate, winding 1 larger part of the pulling force, that is, the node 7-11 reserved on the concrete pouring hole 19 and class thick liquid hole 21 adopts D=120mm the round hole, the remaining portion of the concrete pouring hole 20 and class thick liquid hole 22 a 200 mm × 200 mm square; in addition there is a need for node 7-11 is reserved in pouring concrete 5 the required hole 24, when pouring concrete, the, air in the pipe to escape through the air vents, to ensure that concrete has the advantages of compactness. (2). All node according to the design requirements and assembled to form steel truss; then utilize the reserved prestressed drag line hole 17 and hole 18 in the winding 1 boom 1a, web member 3a, 3b and node 7-13 of prestressed steel strand passes through the inside of the 4, steel strand 4 in the winding 1 length provided in, the required tensioning symmetrical steel, and the concrete pouring hole 19, 20 during the upper chord of the part 2 of the chord 2a, all of the lower chord 2 boom 2a and the upper, all nodes lower chord 7-16 inner, in addition to web member 3a, 3b of the web members other than 3 pouring the concrete 5. In this embodiment, a preformed hole of the position of the bar reinforcing processing: wherein the reeving the required process hole 18 and concrete pouring hole 20 using plate-plugged opening, and is connected with the the full penetration butt weld; concrete pouring hole 19 are arranged on the opening of the cover plate 23, provides the four sides of the welding seam pastes the angle ; class thick liquid hole 22 and hole 24 is not of other processing. Prestressed pulls passesrope steel articulation line two beams 4 to form a large-SPAN suspension to the cantilever structure, the advance 7000kN, because prestressed cable is too long, there is a horizontal section of only about 100m left and right, if prestress loss through a long period of time is large, the actual construction, will be prestressed steel strand 4 is divided into two sections in the truss middle part overlapping, in order to meet the requirements of the prestressed pulls Zola to pass. Embodiment 2 The embodiment of the invention 2 as 18, 19 as shown, and the upper one embodiment is different, in this embodiment, of the invention the overall pre-stressing for large SPAN of the truss in structure, the truss upper chord 1, the lower chord 2 boom 1a, 2a and the web member 3 by the rigid connection between the "K" type node, the lower chord 2 with end of the end part of the support 6a. With the ordinary structure of cantilever stress on the contrary, the upper chord of the truss 1 is pressed, the lower chord 2 tension, the lower chord 2 in all the nodes are both provided with two pairs of the two horizontal leads and drag line hole tube 17, is of prestressed steel strand 4 is arranged on the lower chord tensile 2 boom 2a and the lower 2 in node, steel strand 4 for the two ends of the rivet 28 is fixed on the is located in the last quarter 2 at node of the end of; the in in large SPAN structure, the compression of the web members of the truss upper chord of the pressurized internal force of 2 chord 1a is much smaller compared with, in order to reduce the weight of the structure itself, the only the upper chord 1 chord 1a pouring the high-strength concrete, in other words pouring concrete 5 is only the part of the upper chord of the truss 1 boom 1a and upper chord 1 node. The embodiment of the construction method, and the upper one is by the embodiment, because the upper chord of the truss 1 is pressed, the lower chord 2 tension, therefore, in the step 1 in, the lower chord of the truss 2 node is prestressed drag line hole and in which tube 17 ; and the upper chord of the truss 1 boom 1a and concrete pouring hole reserved in the node 20. Because the web member 3 does not need to be cast in concrete, so that the upper chord 1 does not need to be reserved on a node class thick liquid hole , node only of concrete in the winding 1 in the region of the chord can be; stated step 2 in, using reserved prestressed drag line hole 17 in the lower chord 2 boom 2a of prestressed steel strand passes through the inside of the and node 4, of prestressed steel strand the required 4 is used for tension, and to the truss upper chord 1 boom 1a and high-strength concrete pouring in the node. In this embodiment, construction conditions allow, reeving hole are not reserved, completion of step (1) then, in the step (2) in, using reserved first prestressed drag line hole and drag line tube 17 in the lower chord 2 boom 2a of prestressed steel strand passes through the inside of the and node 4, the steel truss assembled to form all the components. Because the pouring of the concrete is only upper member 1 by the pressure of the, step (1) of the reserved in the concrete pouring hole 20 can be a 200 mm × 200 mm square, and in the pouring end concrete after heavy plate member-plugged opening with the same, the full penetration butt weld the connection. The above 2 embodiment, a truss of the present invention between the punch can be orthogonal, promax combined mode, that is, can be shape-phase orthogonal between, is between the punch can also be oblique, between the punch can also be a combination of orthogonal and skew, can be at fixed, i.e. rigid connection, so as to form the orthogonal space truss system, the truss structure is beneficial to improve the spatial coordination of deformation capacity and integrity. The concrete is of high grade, i.e., high strength concrete. The patent refers to the field of 'structural elements and building materials'. The invention relates to a pre-stressing whole steel pipe truss; components of the truss include bars and nodes; the bars include chords and webs of upper and lower chords; the invention is characterized in that the pulled bars of the truss and the connected nodes are at least provided with a beam of pre-stress strand; both ends of the pre-stress strand are respectively fixed on both ends of pulled sections formed from the pulled bars of the truss and the connected nodes; concrete is casted in the pulled bars of the truss and the connected nodes. The whole truss is a truss system combined with a plurality of materials, such as steel, concrete, pre-stress strand, which improves the bearing capacity and rigidity of the truss, and provides the secondary defensive line for the truss system only by little economic investment. The invention also discloses the construction method of the pre-stressing whole steel pipe truss. 1. A prestressed steel pipe whole truss, the truss component of the composition of the tension member and the node, the rod member includes upper chord (1), the lower chord (2) the chord member and web member (3); characterized in that at least in the truss is connected by pull rod piece and in a node of a prestressed steel strand is provided with at least one beam (4), the two ends of the prestressed steel strand are respectively fixed on the truss is connected by pull rod member and the node of the two ends of the tension, of the truss in the device and is connected with the concrete is poured within the node (5). 2. A prestressed steel pipe whole truss according to Claim 1, characterized in that said node is a "K" type node, in other words upper chord (1), the lower chord (2) the chord with web member (3) is between the "K" type node is connected, the "K" type node of the vertical-side horizontal arrangement, is connected with the chord; "K" of the two-type node of the web members with the inclined bevel (3) are connected; bar connecting to the nodes of the set of prestressed steel strand (4) hole passing through the leads, the leads within the node where the hole is arranged on the stiffening rib close to the port (25) is. 3. A prestressed steel pipe whole truss according to Claim 2, characterized in that the two leads into a group of holes, is located in the vicinity of the second port in the node, connecting the nodes of the bar is also provided with a lead pipe (17), which tube (17) are respectively fixed on the two ends of the second port in the node stiffening rib plate (25) of the drag line hole , 4. A prestressed steel pipe whole truss according to Claim 3, characterized in that said node drag line tube can also be provided with a support (17) of the support rib (26), (27). 5. A prestressed steel pipe whole truss as in Claim 3 or Claim 4, characterized in that the prestressed steel strand (4) is arranged on the upper chord of the truss (1) in, in other words is set up in the winding (1) is connected to the boom and the node of the same; and pouring concrete (5) to the part of the bottom chord of the truss (2) and pressed web member (3). 6. A prestressed steel pipe whole truss as in Claim 3 or Claim 4, characterized in that the prestressed steel strand (4) is arranged on the bottom chord of the truss (2) in, in other words is set up in the lower chord (2) is connected to the boom and the node of the same; and pouring concrete (5) for the truss upper chord of the part (1) and pressed web member (3). 7. A prestressed steel pipe whole truss as in Claim 3 or Claim 4, characterized in that the prestressed steel strand (4) is arranged on the bottom chord of the truss (2) in, in other words is set up in the lower chord (2) in the node of the boom and; pouring concrete (5) only the part of the to the presses the top chord (1) the chord and node. 8. A prestressed steel pipe whole truss according to Claim 5, characterized in that the pouring concrete (5) of the part also comprises non-cantilever portion of the midspan of all components of a part, of prestressed steel strand (4) of the girder (1) length provided in, the symmetrical stretching. 9. Restressing of the whole truss construction method of the steel according to Claim 1, characterized in that it includes the following steps: (1). First using steel into a pipe member, the member includes a rod and a node, rod member includes upper chord (1), the lower chord (2) the chord member and web member (3), the node of the prestressed steel strand which reserved in the hole, at least in the device reserved in concrete pouring hole; (2). Then utilize the reserved drag line hole node in the tensioned bar and of prestressed steel strand in the (4), the required stretching of steel, and to the pressed rod and node pouring concrete (5). 10. Restressing of the whole truss construction method of the steel according to Claim 9, characterized in that the step (1) in, in the node which is between the holes of the tube leads (17), the step (2) in, which passes through the steel pipe (17) in. Cantilever ends of the bottom chord of the truss 150.962 120.798 19.98% Cantilever ends of the bottom chord of the truss 120.798 95.836 20.7% Truss the maximum tensile stress 260.93 193.54 25.9% The maximum compression stress of the truss -257.24 -247.10 4.0% After twice prestressed applied end 1st displacement (mm) -1.23 0.7 -0.98 After twice prestressed applied end 2nd displacement (mm) -3.09 1.88 -2.42 The displacement direction (for contact pin reduction) Upward Downward Upward The design value (kN) 276 276 276 276 Test values (kN) 506 554 550 615 Mast are/design 1.83 2.01 1.99 2.23 The design value 276 30.18 25.68 25.53 20.62 Unloading 0.73 0.54 0.69 0.43 400 (about design load of 1.5 times) 37.95 32.83 32.42 28.49 Unloading 2.64 1.79 2.51 1.76 The deformation when the bearing reaches the limit 62.84 63.29 60.83 61.28 Unloading 27.65 24.65 25.14 17.55