Side Span Research Articles

Aerodynamics of wind effects on the Akashi Kaikyo Bridge

The Akashi Kaikyo Bridge, which will cross the Akashi Kaikyo Straits with a shore-to-shore distance of about 4 km, is a very long-span truss-stiffened suspension bridge for six road lanes with a main span of 1,990 m and two side spans of 960 m. Its extremely flexible features, caused by the span length never experienced, increase importance of careful detailed considerations on static as well as dynamic effects in the aerodynamics of the superstructure. The paper describes some design considerations of wind effects and the outlines of full aeroelastic bridge model wind tunnel tests, together with primary test results analyzed so far, which have been conducted in order to carry out final verification of the wind resistance safety of this bridge at an especially constructed boundary layer wind tunnel of 41 m width.

Construction of boundary layer wind tunnel for long-span bridges

In order to carry out final verification of the aeroelastic safety of the Akashi Kaikyo(strai) Bridge, which has a main span of 1,990 m and two side spans of 960 m and a truss stiffening girder, its full aeroelastic model wind tunnel tests were planned and are now in progress. A geometrical 1 100 scale model was selected and primary dimensions required for the test section of wind tunnel were determined as follows: width 41 m, height 4 m and length 30 m. This paper presents some discussions related to this large boundary layer wind tunnel facility and some new ideas of modeling for the bridge.

A SIMPLIFIED METHOD OF ESTIMATING NATURAL FREQUENCIES OF THREE-SPAN CONTINUOUS TYPE CABLE-STAYED BRIDGES WITH INTERMEDIATE SUPPORTS IN SIDE SPANS

The intermediate supports in side spans are expected to increase the total rigidity of cable-stayed bridges. Therefore, it is significant to examine the effects of intermediate supports on the dynamic behavior of this type of bridges.In this paper, natural frequencies of cable-stayed bridges with and without intermediate supports are compared with respect to nondimensionalized parameters, in order to get the simplified method of estimating natural frequencies of the three-span continuous type cable-stayed bridges having intermediate supports in side spans. The validity of this method is also confirmed by comparing the results by means of the eigenvalue calculation.

STIFFNESS CHARACTERISTICS OF MULTICABLE SUSPENSION BRIDGES.

A multicable suspension bridge is considered to be one in which two or more cables develop different profiles. Sets of such cables may support both sides of a bridge deck. Deflexions have been compared in a non-dimensional form for both classical (having parabolic cable profiles) and multicable suspension bridges subject to point and distributed loading. Also, natural frequencies have been compared in non-dimensional form. The influence of deck stiffness, side span arrangement and the introduction of horizontal cable restraints are investigated. It is found that multicable suspension bridges tend to have improved stiffness characteristics as compared with a bridge of corresponding classical configuration. (Author/TRRL)

Construction of East Huntington Bridge

T East Huntington Bridge is a cable stayed structure over the Ohio River connecting West Virginia and Ohio at East Huntington. The stayed girder has a main span of 900 ft (274 m) and a side span of 608 ft (186 m) with approach spans at both ends (Fig. 1). This is a two-lane bridge with a total deck width of 40 ft (12 m) at the cable stayed portion and 33 ft6 in, (10.2 m) at the approaches, The actual curb to curb roadway is 30 ft (9.1 m) wide. The cable stayed portion of the bridge girder has a concrete slab supported by steel floor beams spaced at 9 ft (2.7 m) on center, These floor beams are framed transversely into the two longitudinal concrete edge girders. The cables are anchored in the edge girders. The 33 ft 6 in. (10.2 m) wide approach at the Ohio side is a single cell concrete box girder. A transition piece connects the box girder to the stayed girder. The construction plans specified that the cable stayed portion of the girder shall be built in precast segments while the box sections are to be cast in place. The pylon is also cast in place.

A STUDY ON THE DETERMINATION OF THE BASIC CONFIGURATION OF THE THREE SPAN CONTINUOUS CABLE-STAYED GIRDER BRIDGE WITH MULTIPLE CABLES

In recent years, many cable-stayed girder bridges with a long span length more than 400 m have been planned and these projects are mostly planned as structures with multiple cables. Nevertheless, the materials for basic planning of them have not been prepared sufficiently so far. In this paper, the materials for basic planning of them are presented. That is to say, the determining method of prestress quantity of the cables which is most important on designing the cable-stayed bridges is discussed and presented relating to the anchoring points of the cables to the girder. Furthermore, the materials for selecting the ratio a side span length to a center span length are presented.

Ambient Vibration Studies of Golden Gate Bridge: I. Suspended Structure

Extensive experimental investigations were conducted on the Golden Gate Bridge in San Francisco, California, to determine, using ambient vibration data, parameters of major interest in both wind and earthquake problems, such as effective damping, the three‐dimensional mode shapes, and the associated frequencies of the bridge vibration. The paper deals with the tests that involved the simultaneous measurement of vertical, lateral, and longitudinal vibration of the suspended structure; a subsequent paper addresses the measurement of the tower vibration. Measurements were made at selected points on different cross sections of the stiffening structure: 12 were on the main span and 6 on the side span. Good modal identification was achieved by special deployment and orientation of the motion‐sensing accelerometers and by summing and subtracting records to identify and enhance vertical, torsional, lateral, and longitudinal vibrational modes. In all, 91 modal frequencies and modal displacement shapes of the suspended span were recovered: 20 vertical, 18 torsional, 33 lateral, and 20 longitudinal, all in the frequency range 0.0–1.5 Hz. These numbers include symmetric and antisymmetric modes of vibration. Finally, comparison with previously computed two‐ and three‐dimensional mode shapes and frequencies shows good agreement with the experimental results, thus confirming both the accuracy of the experimental determination and the reliability of the methods of computation.

Response of suspension bridges to travelling earthquake excitations: Part II-lateral response

The lateral response of suspension bridges to travelling earthquake excitations is investigated in the time and frequency domains. The ground motion inputs at one support are assumed to propagate, with different speeds, such that they hit the other supporting points of the structure with no change of shape (non-dispersive waves). It is assumed that the vibration of the center span can be treated separately from that of the side spans; furthermore, both the piers and towers are assumed to be relatively rigid in the lateral direction. A finite element dynamic analysis is utilized to investigate the lateral earthquake response. The response of the Golden Gate Bridge to ground motions recorded during the 1979 Imperial Valley earthquake is studied. It was found that the transmission time can have a significant effect on the response, that a relatively large number of modes is necessary to obtain a reasonable representation of the response, that uniform ground motion is not a good assumption, and that the additional cable tension induced by the lateral excitation is very small in comparison with the dead-load value; however, the induced displacements and flexural stresses can be significant live load conditions.

Lateral Buckling Tests on Welded Continuous Beams

Twenty-one two-span continuous beams with nominally identical cross sections of welded I-250x100x6x8 mm are tested in seven groups of three, each group having different span length. These continuous beams are tested under a concentrated load on the midspan of one side span. The continuous test beams are on the simple and clamped supports at the both ends against in and out-of plane displacements with an intermediate support. The test results are compared directly with the buckling behavior of simple beams and also with the buckling results based on the effective length concept. The ultimate strengths of the present continuous beams are higher than those of simple beams and scatter between the elastic buckling strength curves of simple beams and of propped cantilever beams which are considered to have a nonloaded span with infinite rigidity. However, in the plot of (P\du/P\dy) vs (λ\N = P\dy/P\dE) the test results of continuous beams scatter on the lower part of the results of simple beams and the coefficients of variation are close to the values of simple beams.

CONSTRUCTION OF THE NAVIGATION SPANS OF THE RIO NITEROI BRIDGE, BRAZIL.

Keywords HOWARD NEEDLES TAMEN & BERGENDOFF REDPATH DORMAN LONG, CLEVELAND BRIDGE AND ENGINEERING, MONTREAL ENGENHARIA CONSTRUCTION, SPANS, FABRICATION, LARGE, GIRDERS, CONCRETE, ORTHOTROPIC, WELDED, SECTIONS, RING, JACKING, CAPACITY, STEELWORK, WORKS, THREE SPAN, CONTINUOUS, MANAGEMENT, FINISHING, BRIDGES, COUNTRIES, ERECTION, STEEL, CENTRE, LANES, DECKS, SITES, SIDES, PIERS, EQUIPMENT, TENSION, WELDING, DESIGN, RELIEF, PRECAST, PLANNING, MAIN, NAVIGATION, DEVELOPING, ASSEMBLY, BOX, TWIN, TRAFFIC, SURFACING, FLOATING, TEMPORARY, BASES, JACKING UP, MEMBERS, LIFTING, PERMANENT, STRESS, PRESTRESSED, CONTRACTS, PONTOONS RIO NITEROI, NITEROI, RIO DE JANEIRO, GUANABARA BAY BRAZIL, SOUTH AMERICA... Show All

Puente Río Colorado - Costa Rica

The Colorado River bridge is located in a 95 m deep canyon, with a 122 m span. To choose the type of bridge, it has been endeavoured to use the largest possible number of national building materials which, together with the difficulty of reaching the site, meant that a series of classical solutions had to be rejected. That of an arch bridge was adopted, with a reversed support on prestressed cables, on which the road passes. The system is based on the hanging bridge principle, but with the rolling track resting on the cables, instead of hanging from them. There is a first cover, made up of prefabricated components, on the cables, which strengthens the bridge's stability. This cover supports three portal-columns, the pillars of the final roadway. The cables were prestressed from the heads of the two sloping pillars. The two side spans were designed with prefabricated T girders.

Lateral Wind on Side Spans of Suspension Bridges

Lateral wind on side spans of suspension bridges is examined. A generalized solution for the deflection of the side span is presented by means of dimensionless parameters. Existing suspension bridges with controlling ranges of side span characteristics are examined and limiting values for the side span parameters are selected accordingly. Curves for moment, reaction and deflection coefficients are presented for the purpose of rapid design.

Puente Verrazano-Narrows

This outstanding suspension bridge underwent a long process of preparation, and it has finally served to solve a most urgent and intense problem of communication between Brooking and Staten Island. This bridge represents an exceptional engineering achievement firstly because of the 1,298 m span between its two towers, and the two side spans of 370 m; secondly due to the vast amounts of materials involved in its construction. The suspended deck will have two directions of traffic, each consisting of six lanes, the two directions separated by a central division. The anchorage and foundations reach down to a depth of 50 m. The towers supporting the main suspension cables are 210 m high above the mean sea level. Their prefabricated external metal shell contain inside a complex system of thousands of metal cells. The deck hangs from four main suspension cables, each 90 cm in diameter. Hanger cables, each 55 cm in diameter, support the deck. The cable spinning over the main towers was a difficult and highly complicated operation. Details of this are given in the accompanying diagrams. Simultaneous with the construction of the bridge, the main access roads to it have been improved and altered, in order to chanalise the heavy traffic more effectively towards it. The whole project, including the construction of the bridge and alterations to the approaches, has amounted to a total cost of the order of 400 million dollars. The safety of the personnel working on this project has been very carefully studied. Ellaborate arrangements are being rigidly enforced for the protection of human lives. It is hoped that this huge project will be completed within the present year.

Golden Gate Bridge Vibration Studies

Analysis of movement at ten locations on main and side spans of Golden Gate bridge; it is shown that oscillations are almost always symmetric with amplitude inhibited by sharply downward deflection of prevailing west wind as it passes over high hill before passing north side of span; installation of bottom lateral system to prevent recurrence of torsional motion.

VIBRATION OF SUSPENSION BRIDGE DUE TO VERTICAL GROUND MOTION

As regards the vibration of suspension bridge due to horizontal ground motion, which can be represented by sinusoidal wave, and whose direction is parallel to the bridge axis, the writer has already published the results obtained by model tests and by theoretical analysis at the 2 nd World Conference on Earthquake Engineering, 1960. In order to investigate the vibrational characteristics of vibration of suspension bridged, and to prove the validity of the theory, the writer made a model, whose total length is 548 m, and the vibration tests were done by using the model. After confirming the validity of the theory given by the writer, he applies his analytical method to analyze the vibration of suspension bridges due to vertical ground motion, and performs numerical analysis about the Wakato Bridge, which is now under construction.In this paper, the writer does not analyze the vibrational characteristics of suspension bridges due to horizontal ground motion, whose direction is perpendicular to the bridge axis, because the perpendicular strength of the suspension bridge is mostly checked against large wind load, and usually lateral vibration of the suspension bridge causes the torsional vibration which does not give rise to large additional cable tension.The ratio of vertical acceleration to horizontal one of earthquakes is obtained by using the acceleration records in the past. The number of kinds of cases which are treated in this paper is four, owing to the combination of both side span with stiffening girder or not and condition of the top of the tower, sliding or fixed.

Golden Gate Bridge Vibration Studies

The records of bridge movement obtained over a period of years by means of instruments at ten locations on the main and side spans of the Golden Gate Bridge are analyzed. They are plotted against wind velocity and correlated with theoretical analyses of wave form and against model test indications of the response to winds of different velocities. It is shown that the oscillations are almost always in a symmetric mode with the amplitude inhibited by the sharply downward deflection of the prevailing west wind as it passes over a high hill before striking the north side span. It is shown that during one forty minute period the oscillation was in an asymmetric torsional mode, uninhibited, and reached amplitudes predicted from the model tests. A bottom lateral system has been installed. Tests indicate that it will prevent a reoccurrence of the objectionable torsional motion.

The Golden Gate Bridge, San Francisco

Engineering of July 7 contains the first of a series of articles on the Golden Gate Bridge, San Francisco, by Mr. C. E. Paine, who acted as principal assistant engineer during its construction. This bridge, which was opened in May 1937, is notable as having the longest suspension span of any bridge yet erected, the length of the span being 4,200 ft. as against the 3,500 ft. of the Hudson River Bridge built in 1931. Its side spans are 1,125 ft. long, giving a total suspended structure of 6,450 ft. The two supporting towers are 690 ft. 4 in. from the top of the piers to the bottom of the saddles and have a combined weight of 35,178 tons, while the wire cables are each over 30 inches in diameter and contain 27,572 steel wires 0·195 inches in diameter, arranged in 61 strands. the roadway across the bridgo is 60 ft. wide, giving room for six lines of motor traffic, and there are two side-walks 10 ft. wide. The dead load of the main span per lineal foot is 9·51 tons and the live load allowed for is 1·78 tons per lineal foot. The bridge leads from San Francisco to a district ideal for suburban development and for recreational purposes, and it has closed almost the last break in the two thousand miles long coast road which extends from Canada to Mexico. The American Institute of Steel Construction selected the Golden Gate Bridge as the most beautiful bridge, costing more than 1,000,000 dollars, completed in the United States in the year 1937.