I. Introduction
Generally speaking, the main load-bearing members of cable bridges are anchored on the anchorage. In a few cases, in order to meet the special design requirements, the main cable can also be directly anchored on the stiffening beam, thus canceling the huge anchorage and becoming a self-anchored suspension bridge.
In the past, the stiffening beams of self-anchored suspension bridges were mostly steel structures, such as Japan Huahua Bridge, Korea Yongzong Suspension Bridge, San Francisco-Oakland Bay New Bridge, and Muhu Island Pier in Estonia, which was opened to traffic at 1990. In July 2002, the world's first reinforced concrete self-anchored suspension bridge, Jinshitan Golden Bay Bridge, was completed in Dalian, which provided valuable experience for the research of this kind of pier. Since then, Jilin, Hebei and Liaoning are designing, designing and building four reinforced concrete self-anchored suspension bridges.
Self-anchored suspension bridge has the following advantages: ① There is no need to build mass anchorage, so it is especially suitable for areas with poor geological conditions.
(2) Limited by the terrain, it can be flexibly arranged in combination with the terrain, and can be made into a suspension bridge with two towers and three spans and a suspension bridge with two spans in one tower.
(3) For the stiffening beam made of reinforced concrete, the stiffness will be improved because it needs to bear the pressure transmitted by the main cable, which saves a lot of prestressed structures and devices and overcomes the shortcoming that steel is prone to buckling under large axial force.
(4) The use of concrete materials can overcome the shortcomings of the former self-anchored suspension bridge, such as large steel consumption, high construction and later maintenance costs, and can achieve good economic and social benefits.
⑤ It retains the shape of the traditional suspension bridge, which is a very competitive scheme in medium and small span bridges.
⑥ Due to the low cost, reasonable structure and beautiful appearance of the bridge, reinforced concrete materials are unfairly used in areas with poor foundation and difficult anchorage construction.
Self-anchored suspension bridge inevitably has its own shortcomings: ① Because the main cable is directly anchored on the stiffening beam, the beam bears great axial force, so it is necessary to increase the cross section of the beam. For the stiffening beam of steel structure, the cost is obviously increased, while for the stiffening beam of concrete material, the self-weight of the main beam is increased, thus increasing the steel consumption of the main cable, so the span of using these two materials will be limited.
(2) The construction steps are limited. After the stiffening beam and bridge tower are completed, the main cables and slings must be hoisted, and a large number of temporary supports need to be erected to install the stiffening beam. Therefore, if the span of self-anchored suspension bridge increases, its additional construction cost will also increase.
③ The local stress in the anchorage zone is complex.
(4) Compared with the ground-anchored suspension bridge, the construction control of the suspender is more complicated due to the nonlinear influence of the main cable.
Second, historical review.
/kloc-in the second half of the 0/9th century, Austrian engineer Joseph. Rankin and American engineer Charles. Bender independently conceived the shape of self-anchored suspension bridge. Bender applied for a patent in 1867, while Rankin built a small railway self-anchored suspension bridge in Poland in 1870.
In the 20th century, self-anchored suspension bridges mushroomed in Germany. 19 15, German designers built the first large-scale self-anchored suspension bridge-Cologne-Dietz Bridge on the Rhine River in Cologne. At that time, engineers chose this type of bridge mainly because of the limitation of geological conditions. The main span of the bridge is 185m, and the steel beam is supported by wooden scaffolding until the main cable is in place. Since then, three bridges across the Allegheny River in Pittsburgh, Pennsylvania and the Cheongju Bridge built in Tokyo, Japan have been influenced by the Cologne-Dietz Bridge. Although the Cologne-Dietz Bridge was destroyed at 1945, the steel box girder on the original abutment is still preserved to this day. The span of three suspension bridges in Pittsburgh is smaller than that of Cologne-Dietz Bridge, but the construction technology has made great progress than that of Cologne-Dietz Bridge. Within 25 years after the completion of the Cologne-Dietz Bridge, four suspension bridges were built on the Rhine River in Germany, the most famous of which was the Cologne-Mirheim Bridge built in 1929, with a main span of 3 15m. Although the bridge was destroyed at 1945, it still kept the span record of self-anchored suspension bridge. In 1930s, engineers thought that the axial force of stiffening beams of self-anchored suspension bridges would make the mechanical properties of such bridges close to the elastic theory, so many self-anchored suspension bridges were built in the United States and Germany during this period.
Thirdly, foreign modern self-anchored suspension bridges.
Japan Jihua Bridge 1
Japan Jihua Bridge, formerly known as Osaka North Port Contact Bridge, is the world's earliest super-long self-anchored suspension bridge and the only English self-anchored suspension bridge in the world. 1990 opened to traffic.
The span arrangement is (120300 120)m, which is the largest self-anchored suspension bridge in existence. The vertical span ratio is 1/6, so as to reduce the cable force of the main cable and make it borne by the cross beam.
The bridge adopts single main cable and PWS method, including 30 strands, each strand 184 steel wires. There is only one cable plane, and the sling is made into an inclined shape to form a triangular suspender, which, together with the steel box stiffening beam, embodies the characteristics of the English suspension bridge.
The stiffening beam of steel box is a three-chamber box with a beam height of 3. 17m. Due to the single cable plane, the total box width is 26.5m, and the box height is larger according to the requirements of torsion. The tower is vase-shaped, but the lower tower column is shorter. The herringbone upper tower column can only be installed after the stiffening beam section is erected.
2 Yongzong Suspension Bridge in Korea
Yongzong Suspension Bridge is located on the expressway from Incheon International Airport in Seoul, South Korea to downtown Seoul. It is the world's first self-anchored county cable bridge with double-deck traffic.
The span layout is 125300 125m, and the main span is the same as that of Jahwa Bridge in Japan. The vertical span ratio is 1/5 to reduce the main cable force.
The tower is designed as a vase with a height of 104.6m, which is more beautiful. Cable laying adopts aerial rotation method. The diameter of the main cable is 46.7cm, and the transverse spacing at the tower of the main cable is limited by the tower type, which is 6.6m, while the width at the middle of the main span is 35m (the same as that in Liang Kuan). The main cable presents a three-dimensional curved surface.
The stiffening beam is three-span continuous, and its web and the lower part of the running railway are trusses. The total height of the beam is 12m and the width is 35m. There are six lanes on the upper floor. There are four lanes and a double-track railway. The upper layer of the stiffening beam is a steel box bearing huge horizontal axial force. The height of the box is 3m, and the total width of the tuyere is 41m.. The construction of the beam is divided into eight sections, which are erected by a 3000t offshore floating crane, all of which are placed on temporary bent frames or towers, and then slings are installed.
Protection system: the stiffening beam is protected by dehumidification. As long as one sensor measures that the relative humidity is higher than 50%, the dehumidification system will automatically start all the work until the relative humidity drops below 40%.
The main cable is protected by S-shaped steel wire winding, painting and dry air system, which is the same as Akashi Strait Bridge in Japan.
3. New Bridge between San Francisco and Oakland Bay, USA
Built in the mid-1930s, the San Francisco-Oakland Bay Bridge is 12.8m in length, which is the longest bridge with the highest technical level in the world at that time. Up to now, it is still the trunk line from San Francisco Peninsula to Dongwan, with heavy traffic, with nearly 280,000 cars passing by every day. The design earthquake force is very small, and its east bridge (steel truss bridge) partially collapsed under the earthquake intensity of 1989 Richter scale 7. 1 degree, so it was decided to build a new bay bridge instead of the existing east bridge, with a total length of 3.6km and a deck width of 25m in each direction, including 5 lanes and light rail. Considering the earthquake returning from 1500, there is also a sidewalk with a width of 4.8m on the south side.
The main channel bridge is a single-tower self-anchored suspension bridge with a span of 385 180m. The diameter of the two main cables is 0.78m, and the east side (385m side) is anchored on the east pier beam. Its saddle is supported by a box beam and designed to be movable to balance the force difference between the two main cables. The west main cable (180m side) surrounds the west pier through two separate cable saddles, which are fixed on the west pier. In the construction process, the force difference between the two main cables is balanced by the stepped seat plate. The prestressed capping beam is designed on the west pier. Its weight can balance the dead load force generated on the west pier due to the asymmetry of the bridge span, and can also be used to bear the different stresses generated by the flat saddles of the two main cables of the west pier under operating load and earthquake load. Tower height160m. The main cables are not crossed, but fixed on a single saddle. The tower consists of four columns connected by shear bars along the height direction. The tower column is a steel box. The columns are connected by a diaphragm beam with a spacing of 3m. The pile cap is 6.5m high and supported on a 13 steel pipe pile with a diameter of 2.5m. Concrete is poured into the pile, with a net length of 20m and embedded in the rock.
The superstructure consists of two hollow anisotropic plates, and the suspender load is distributed on the box girder, which is connected by beams with a width of 10m, a height of 2.5m and a spacing of 30m. The cross beam bears the lateral load of the 72m span of the suspender, which ensures the overall function of the two boxes under the load, especially the wind and earthquake load. The suspenders are arranged outside the two boxes to form a two-dimensional cable plane, which is very beautiful.
4. Other self-anchored suspension bridges
Solo Island Bridge is a bridge connecting Korea and Geogcum Island. The span layout is 1 10480m200m, the rise-span ratio is 1: 8, the stiffening beam is a steel box girder, the height-span ratio is 1: 400, and the bridge tower is H-shaped. From 65438 to 0996, J.F.Klcin introduced a comparison scheme of self-anchored suspension bridges. The span arrangement is 303m950m303m, and a single main cable is used. The main cable with a length of about 200m in the main span is in the beam, which is consolidated with the beam and has high structural stiffness and cable clamps.
Fourthly, domestic self-anchored suspension bridges.
Although the self-anchored suspension bridge came into being and developed earlier in China, few bridges were built in China, and there were few related documents, which made the development of this type of bridge in China far behind that of foreign countries. In 2002, the world's first self-anchored suspension bridge with reinforced concrete stiffening beams was built in Dalian. Since then, the Bridge Research Institute of Dalian University of Technology has designed several reinforced concrete self-anchored suspension bridges, providing valuable experience for domestic bridge construction.
1 Dalian Jinshitan Jinwan Suspension Bridge
Jinshitan Jinwan Suspension Bridge is the first self-anchored suspension bridge with reinforced concrete structure in China and even in the world. It is located on the coastal road of Dalian Jinshitan Tourist Resort, across the estuary of sailing port, and has become a special local scenery.
The main bridge of Jinshitan Jinwan Bridge is a self-anchored concrete suspension bridge. The main cable is directly anchored at both ends of the stiffening beam to make the stiffening beam arch (hanging arch system), and the horizontal component of the main cable is used to counter the thrust of the arch foot, thus playing the role of a tied arch bridge. This not only meets the clearance requirements of the middle span navigation, but also reduces the height of both ends of the main bridge, greatly reducing the length of the approach bridge and saving investment. This camber can also increase the stiffness of the stiffening beam and reduce the deflection of the stiffening beam, so that the bridge has achieved good results in terms of stress and economy. The total length of Jinwan Suspension Bridge is 198m, including main bridge 108m, approach bridge 90m, main bridge span (246024)m, bridge width 10m and rise-span ratio 1:8. It is a double tower and double main cable structure. The stiffening girder of the main bridge is in the form of reinforced concrete side girder, and the beam height is1m. A diaphragm beam is poured in the middle of the beam section, and the approach bridge is a reinforced concrete continuous beam. The bridge tower is a reinforced concrete portal tower with a height of 27m and a diameter of1.5m. The stiffening beam and cross beam of the main bridge are made of 50 # concrete. The main cable adopts Ф 7, and the suspender adopts Ф 5 galvanized high-strength steel wire and cold-cast anchorage. The foundation adopts Ф1.6m bored pile foundation. The main cable passes through the saddle of the bridge tower and does not scatter. The two ends of the main cable are anchored on the main beam, and a shock absorber is arranged in the sleeve at the end of the main cable. The distance between the suspenders on the beam is 3m. The main construction procedures of the main bridge are: bored pile foundation; Pouring piers and towers; Erecting temporary supports, and pouring stiffening beams on the supports; After the stiffening beam reaches the strength, hang the main cable, hang the cable clamp and tension the suspender.
The disparity cable bridge in Jinshitan adopted a brand-new structural form, with a total cost of only 4.98 million yuan, which not only achieved good economic benefits, but also added a beautiful scenery to the beautiful coastal city of Dalian with its unique design, providing valuable experience for the construction of such bridges.
2. Haiyan Tangqiao, pinghu city, Zhejiang Province
Haiyan Tangqiao is located in East Lake Scenic Area, pinghu city City, Zhejiang Province. The superstructure is a self-anchored reinforced concrete suspension bridge with a span combination of (307030)m and a total length of164m. The total width of the bridge deck is 40.0 meters; ; The longitudinal slope of the bridge is 2.20%.
Pinghu TangHaiyan self-anchored suspension bridge makes full use of the mechanical characteristics of self-anchored suspension bridge, draws on some advantages of similar bridges and makes improvements. Its main features are: the main cable is anchored at the beam end, and it is not necessary to build expensive anchorage; The main girder adopts reinforced concrete box girder, and the horizontal component of the main cable is used to apply free prestress to the main girder, and the prestressed steel beam is no longer configured in the main girder; There is no saddle at the top of the tower, and the main cable is directly anchored at the top of the tower. This kind of bridge is novel in structure, beautiful in shape, light in structure, reasonable in stress of members, economical in materials and lower in cost than prestressed concrete continuous beam bridges and partial cable-stayed bridges with the same span. It is a very competitive bridge type in medium and small spans.
Force analysis of verb (verb abbreviation) self-anchored suspension bridge
1, stress principle
The superstructure of self-anchored suspension bridge includes four parts: main beam, main cable, suspender and main tower. The transmission path is: vertical loads such as bridge deck weight and vehicle load are transmitted to the main cable through the derrick, and the main cable bears tension, while
The main cable is anchored at the beam end to transfer the horizontal force to the main beam. Because the horizontal force of suspension bridge is related to the rise-span ratio of the main cable, the horizontal force in the main girder can be adjusted by adjusting the rise-span ratio. Generally speaking,
When the span is large, the rise-span ratio can be appropriately increased to reduce the pressure in the main girder, and when the span is small, the rise-span ratio can be appropriately reduced to appropriately increase the prestress in the concrete main girder. Because the main cable is anchored at the top of the tower, in order to minimize the horizontal force borne by the main tower, it is necessary to ensure that the horizontal force in the side span main cable is basically equal to that generated by the middle span main cable, which can be adjusted by reasonable span ratio or changing the line shape of the main cable.
In addition, the dead load in the self-anchored suspension bridge is borne by the main cable, while the live load needs to be borne by the main beam, so the main beam must have a certain bending stiffness, and the box section with a certain bending stiffness is more suitable as the form of the main beam.
2. Structural characteristics
Compared with the ground anchor type, the self-anchored structural system can ignore the influence of geological conditions, cancel the huge anchor ingot and reduce the project cost. Self-anchored type is adopted, and the main cable is anchored on the stiffening beam. Compared with other bridge types of the same span, it has its unique curved line shape and elegant appearance. Modern bridges not only meet their own structural requirements, but also pay more and more attention to landscape design, which has great development prospects.
The self-anchored suspension bridge adopts concrete stiffening beam, which not only increases the self-weight of the system, but also increases the stiffness of the system, so that the safety index, applicability index, economy index and aesthetics index of the bridge can be perfectly unified within a certain span. As far as structural stress is concerned, it is undoubtedly equivalent to providing concrete, a material with good compressive performance, with a self-anchored system, anchoring cables on the main girder and using the main girder to resist horizontal axial force. It's free. Prestress. Therefore, the common reinforced concrete structure is adopted, which saves a lot of prestress devices, and the project cost is greatly reduced because of the economy of concrete material relative to steel. However, due to the poor tensile and flexural properties of concrete, this characteristic should be considered comprehensively when analyzing its stress.
Because the tension of the main cable of self-anchored suspension bridge is transferred to the bridge itself, not to the anchor ingot, the horizontal component of the tension of the main cable produces pressure in the superstructure of the bridge, and its vertical component will produce uplift force at both ends of the bridge if the two ends are not restrained. For example, Jinshitan suspension bridge adopts two methods to resist this uplift force: one is to set tension and compression bearings at the anchor pier; Second, a bracket is arranged at the joint of the main bridge and the approach bridge, so that the weight of the approach bridge is pressed on the main beam.
Because the main girder is composed of concrete, the shrinkage and creep of concrete must be considered in the design and calculation, which makes the design of concrete self-anchored suspension bridge more complicated than that of steel bridge.
Six, construction technology
1, main tower construction
The main tower of suspension bridge is generally high, and the tower body is usually poured in sections by turnover formwork method. Pay attention to the reserved reinforcement and formwork support embedded parts at the connecting plate of the main tower. The concrete at the top of the cable saddle tunnel should be poured after the erection of the main cable is completed, so as to facilitate the construction of the cable saddle and cable. The construction control of the main tower is mainly verticality monitoring. After each section of concrete construction is completed, when the temperature is relatively stable at 8:00 ~ 9:00 the next morning, the perpendicularity of the tower is monitored by using the total station, so as to adjust the concrete construction of the tower. It is necessary to avoid testing in the period of drastic temperature change, and at the same time, observe the quality of concrete at any time and adjust the concrete mixture ratio in time.
2. Saddle structure
Check the elevation of the top surface of steel plate. After meeting the design requirements, clean the pin holes on the surface and around it, hoist them in place, align the pin holes, and pin the base with the steel plate. Oil the surface of the base and install the main body of the cable saddle. Cable saddle is composed of cable seat, bottom plate and cable cover, so it is difficult to hoist and place it as a whole. It can be hoisted by cranes or lifting equipment. The installation error of the cable saddle should be controlled within the maximum error of the transverse axis of 3mm and the maximum error of the elevation of 3 mm. After hoisting in place, the pin should be inserted for positioning, the bottom surface of the saddle should be closely attached to the base, and the gaps around it should be filled with butter.
3, the main girder casting
The pouring of main girder concrete is the same as that of ordinary bridges. First of all, the control of beam height must be accurate, and the settlement and deformation of the reserved bracket must be accurately calculated. Secondly, the pre-embedding of beam embedded parts requires high precision, especially the reserved hole of tie rod should have accurate position and good verticality, so as to ensure that the tie rod is always in the center of the hole during normal tensioning.
The pouring sequence of the main girder should be symmetrically constructed from both ends to the middle to prevent the bracket from deviating due to eccentric load. During construction, the settlement value of the support shall be observed with a level and recorded in detail. Re-survey the beam line type immediately after forming, compare the actual line type with the design line type, feedback information in time, and adjust the next construction.
4. Construction of cable department
(1) Erection of main cable
According to the structural characteristics, the erection of the main cable can be directly carried out on the outside of the temporary bridge or on the poured bridge deck, and lifted into place from the side of the main girder with a winch and a long-arm truck crane.
Cable bracket: To avoid twisting, put the ring cable on the rotatable bracket. Cable idlers (or flexible materials such as straw bags) are arranged on the bridge deck every 4-5m. ) to ensure that the cable sheath will not be damaged by direct friction with the bridge deck when the cable moves longitudinally. Due to the heavy weight of the anchor end, a trolley is used to carry the anchor end of the cable during traction.
Traction of cables: Winches are used for traction. In order to avoid the rope being too long, the longitudinal movement of the cable can be carried out in sections. The cable movement is divided into three sections, and three winches are respectively installed at the second bridge tower and the cable terminal.
Cable hoisting: guide pulleys are arranged on both sides of the tower body, and a winch is fixed near the tower of the main bridge on the approach bridge deck, and the winch cooperates with the cable release device to spread the cable on the bridge deck. The crane is mainly used for lifting to avoid the friction between the cable and the side of the bridge tower during lifting. When the cable is lifted to the top of the tower, lift the cable into the saddle. When the main cable is installed, three cranes are arranged on the bridge side, namely the crane in the anchorage area, the crane at the top of the main cable and the chain hoist.
After the anchor end of the cable is pulled in place, install the main cable anchor in the anchorage area with a lifting crane, and anchor it to the design position at one time, with the lifting force of the crane above 5t; The crane for placing the main cable at the top of the tower is a truck crane with a lifting force of more than 45t when the lifting height on both sides of the two towers exceeds 25m. It is used to directly lift the main cable to the saddle at the top of the tower and put it in place. In order to avoid damaging cables during hoisting, special cable clamps are used to protect cable hoisting points. When the main cable is hoisted to the top of the tower, due to the long cable section of the main span, in order to ensure the stability of the crane, the inverted chain on the tower can be used to assist the hoisting at an appropriate time.
(2) Main cable adjustment
During the manufacturing process, cables should be accurately marked. Mark points include anchor point, cable clamp, cable saddle and mid-span position. Before installation, check the control values according to the design requirements, and make adjustments after the approval of the design unit. According to the adjusted control value, the installation is generally carried out at night when the temperature is relatively stable. Adjustment work includes measuring span length, cable saddle elevation, cable saddle pre-deflection, main cable verticality elevation, cable saddle displacement and external temperature, and then calculating the elevation of each control point.
The main cable is tensioned with 75t jack in the anchorage zone. First, adjust the vertical elevation of the cable in the main span to complete the fixing of the cable saddle. When adjusting, please refer to the mark on the main cable to ensure the adjustment range of the cable. After the main span is adjusted, the side span will stretch the main cable in place according to the cable force provided by the design.
(3) Install the cable clamp
In order to avoid cable clamp distortion, cable clamp shall be carried out after the installation of main cable is completed. Check the installation position of the clamp marked by the manufacturer first, and then peel off the PE sheath there after confirmation. The cable clamp installation adopts the working basket as the working platform, and the working basket is installed on the main cable (or a catwalk is set like a common suspension bridge) to carry the installer to operate on it. Hoist the cable clamp with a steam crane. The key to the installation of the cable clamp is the firmness of the bolt, which should be carried out twice. ) After the cable clamp is installed in place, pre-tighten it with a wrench, then tighten it with a torque wrench, and then tighten it with a torque wrench for the second time after the cable force of the boom is loaded. The installation sequence of cable clamps is from the middle span to the top of the tower, and the side span is from the vicinity of the anchorage point to the top of the tower.
(4) Installation and loading of derrick
The sling shall be installed immediately after the cable clamp is installed. The small boom is installed manually, and the large boom is installed by crane.
Due to the obvious geometric nonlinearity of self-anchored suspension bridge under load, the loading of suspenders is a complex process. The stiffness of the main cable is very small compared with that of the main beam. If the suspenders are directly anchored in place at one time, it is difficult to control the stroke or tension of the tensioning equipment, and it is not economically feasible to adjust the suspenders of the whole bridge by tensioning. In order to solve this problem, it is necessary to obtain the best loading scheme by computer simulation according to the stiffness and self-weight of the main girder and main cable. And in the process of construction, through observation, the tension is corrected.
Tighten the sling symmetrically from the tower column and anchor head with 8 jacks. The anchor at the bottom of the sling is cold-cast, and its anchor cup is cast with internal and external threads. The internal thread is used to connect the connecting rod for jack action when tensioning, and the external thread is connected with a nut to fix the derrick on the anchor pad. Due to the high elevation of the main cable under self-weight, the anchor head under the suspender is located in the main girder before loading, and temporary working support and connecting rod need to be provided during tensioning.
Apply the design force of 1/4 for the first time to temporarily lock each boom! The order of the second pass is the same as that of the first pass. Tension is completed according to the design force, then the actual load of each suspender is detected, and finally each suspender is fine-tuned according to the design force. During the tensioning process of the sling, the top of the tower and the saddle move together! The tower root bears bending moment! This may lead to the danger that the stress of the tower root exceeds the limit, in order to prevent the stress of the tower root from exceeding the limit! After stretching to a certain extent, calculate and analyze according to actual observation! Push the saddle to restore the top of the tower to its original state without horizontal displacement, and so on! Adjust the tension of each sling to the design value.
The control of construction process is very important for all the construction processes of self-anchored concrete suspension bridge, especially in the cable construction process, the cable force of each sling should be fed back in time and accurately. When the sling is tightened, the oil gauge reading of the jack is an intuitive reflection. In addition, the intelligent signal acquisition and processing analyzer measures the tension of the sling through the vibration of the sling. The two methods check each other to ensure that the cable force of each sling is consistent with the design during tensioning.
Seven. Problems needing further study
Research on (1) better construction method. For example, anchoring the mid-span main cable at the bottom of the main girder and adopting swivel construction can overcome the construction difficulty to a certain extent, but how to ensure the stability of swivel construction under the condition of long span needs further study.
(2) Study on the stress distribution under the anchor of the main cable anchorage point.
(3) When the main cable is wrapped with concrete filled steel tube, the anchorage mode of the suspender on the main cable is studied.
(4) Research on the reasonable tensioning sequence of suspenders and main cables.
(5) Research and development of new materials.
(6) Further improvement of stress system and theory.
Eight. Conclusion and its development
(1) The domestic engineering time has proved that the reinforced concrete self-anchored suspension bridge is an economical and beautiful bridge type in medium and small spans, and its structural stiffness is relatively large, so it is suitable for the construction of medium and small span highway bridges and pedestrian bridges.
(2) For the self-anchored suspension bridge with reinforced concrete structure, the design of anchor block is a key link, which not only affects the overall working performance of the structure, but also affects the economic benefits and aesthetic requirements of the bridge, and should be given enough attention.
(3) The biggest difference between the main cable anchorage form of self-anchored suspension bridge and the ground anchor type. According to the different requirements of stress and anchor block structure, direct anchorage, decentralized anchorage and peripheral anchorage can be adopted.
(4) Due to the nonlinear influence of the main cable, the construction control of sling tension becomes particularly critical.
(5) The steel used for stiffening beam is expensive, and the steel structure is easy to buckle under axial force. The use of reinforced concrete materials can just overcome these two shortcomings.
Today, with the rapid development of science and technology, the analysis method is more and more advanced and perfect, and some novel and beautiful structures are studied and valued by designers. Although self-anchored suspension bridge has its own shortcomings and limitations, it is a very competitive scheme in medium and small spans and will be paid more and more attention and welcomed by people. This bridge type, which was neglected for a long time in the 20th century, has been recognized again with the progress of society. With the gradual accumulation of practical experience, the design theory and construction method of self-anchored suspension bridge will be improved and the spanning capacity will be improved. I believe that more and more schemes will favor this bridge type in the future.
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