The bridge is located in Port Coquitlam, B.C. See fig (11), which will provide a connection between the north and south sides of the city. The bridge is cable stayed, and contains 6 spans (102.5, 125, 110.75, 125, 71.3, and 46.55 m) over the CP Rail Port Coquitlam Yard. It has tow expansion joints at the extreme ends, and 4 steel pylons. The steel superstructure is a slight tapering near the north abutment seat. The cross section is twin spine composite steel plate box girders with stiffeners and rolled bracing sections. It contains floor beams, diaphragms, and concrete deck. The twin braced box girders are supported with stay cables (fan layout), fig. (12). The stay towers are fabricated steel box with internal stiffeners. The piers are single line driven steel piles extended above ground with reinforced concrete octagon shaped piers which form an integral connection with the pier cap. The piles for substructure will be driven into the glacial till. Reinforced concrete infill is provided to a depth the structure can resist lateral seismic loads under typical and liquefied soil conditions. 350 AT Steel, 50Mpa concrete and low-relaxation 7-wire strand were used as well.
The main bridge with the steel nose will be erected using the Incremental Launching Method. The full bridge deck, with twin box-girders, will be launched at the same time. The lead tower will be used to provide support for a temporary cable at the tip of the lead span in addition to the 4 sets of permanent stays. No temporarily supports among the permanent piers are allowed as the railway yard underneath is very busy, however 4 temporarily supports will be erected on the south approach (as a fabricating back yard). The bridge will be fabricated into 22 segments ranged from 23 to 30.5 m long. The launching equipment will be anchored on the south abutment which is the starting point. To keep positive reaction in this support is a critical matter, and regarding this, it was found that changing the elevations of the supports is useful in some launching increments and would keep the reactions within optimal values. See fig (13) and fig. (14) below.
My Role in the Project (in Detail):
1) The most appropriate analytical tool to check the launching process was FE model, using MIDAS Civil Software. I created the model after thorough reviewing of the drawings and connections, geotechnical, and the technical design reports. The road profile, bearing elevations and the structural camber (in each incremental step during launching) would effects the position of the inclined nose and the resting part of the nose on these specific bearings (This differs in each step and according to the pretensions of the cables as well), see fig (15). In the model I took into account the exact geometric profile of the finished structure, and the camber. I took advantage of AutoCad and Excel to get the nodal coordinates and transferred them to the geometry file in the software.
2) The properties of the different cross section were calculated manually and with the aid of Excel.
3) I calculated the weight of the nose and superstructure elements carefully, and I included them into the model. Also, I employed Tension-only trusses, nonlinear cable elements and beam elements. By using cable element (which simulate the reduction of the stiffness of the cable while it is sagging), I verified that the cables would not sag during launching; while the forces in the cables would tend to be almost zero in some increments. I utilized gap elements to simulate the changes in boundary conditions for each launch increment. The reason for using the gap elements in the model that the superstructure (in its real shape) would rest on the exact elevation of the supports when the gaps of these certain elements reduced to zero. As a result the displacement (which is the gap) will depend on the location of the superstructure over the supports as well as the structural deformations. I created an excel spread sheets to get the value for each gap during launching (at all increments that belong to a certain construction stage).
4) In the model, I used general-link element which is spring has 2 DoF. This represented the saddle of the temporarily cables at the top of the lead pylon. I selected the lateral stiffness for these elements to represent the friction of the cables over the saddle; while the vertical stiffness was very rigid. A very flexible spring support was included in the model to prevent the instability issues and singularity cases of the unsupported structure. 5m increment movements were analyzed in the software. I ran Geometric Nonlinear Analysis for this type of engineering problem. The 120 output result files were classified into 5 construction stages:
- CS 1: launch from SA to P1, 7 segments, 22 increment and 22 input files.
- CS 2: launch from P1 to P2, 3 more segments, 31 increment and 30 input files.
- CS 3: launch from P2 to P3, 4 more segments, 23 increment and 23 input files.
- CS 4: launch from P3 to P4, 5 more segments, 26 increment and 26 input files.
- CS 5: launch from P4 to P5, 2 more segments, 18 increment and 18 input files.
5) Due to variable support conditions during launching or even during the adjustment of the support elevations, a reversal of actions moments as the structure is launched will be created (with the combination of shear and axial forces), making the flanges and webs of the bare steel superstructure in complicated stress combinations. Through results I checked the general stability and safety during launching, In other words, I found the internal forces, moments, maximum stresses and the related structural safety margins. Fig. (16) shows increment cases in some construction stages.
6) I used lots of excel sheets to draw scattered charts for forces, moments and the nose tip location in space, taking into account the probability of encroachments inside the CP rail permitted envelope.
7) I confirmed the pretensions of the cables and their changes during launching increments, and compared them with the designer values. Also, I checked the displacements at the nose tip, girder tip and back span, see fig (17). When the forces in the cables increase the deflection of the nose tip decrease and the internal forces in the sections increase and vice versa. Adjustment of the temporarily cable’s forces was carried out for each stage (through negotiation with the designer and fabricator) to keep the deflections of any part of the superstructure, and for each increment within the permissible values. Also, attention was paid not to increase the forces to a level that would produce high internal combined stresses or plastic strains in the bare steel superstructure.
8) Like any other analysis, I did approximate hand calculation to verify the reactions, and all results.
The launching of the bridge was started in May 2009.
The main bridge with the steel nose will be erected using the Incremental Launching Method. The full bridge deck, with twin box-girders, will be launched at the same time. The lead tower will be used to provide support for a temporary cable at the tip of the lead span in addition to the 4 sets of permanent stays. No temporarily supports among the permanent piers are allowed as the railway yard underneath is very busy, however 4 temporarily supports will be erected on the south approach (as a fabricating back yard). The bridge will be fabricated into 22 segments ranged from 23 to 30.5 m long. The launching equipment will be anchored on the south abutment which is the starting point. To keep positive reaction in this support is a critical matter, and regarding this, it was found that changing the elevations of the supports is useful in some launching increments and would keep the reactions within optimal values. See fig (13) and fig. (14) below.
My Role in the Project (in Detail):
1) The most appropriate analytical tool to check the launching process was FE model, using MIDAS Civil Software. I created the model after thorough reviewing of the drawings and connections, geotechnical, and the technical design reports. The road profile, bearing elevations and the structural camber (in each incremental step during launching) would effects the position of the inclined nose and the resting part of the nose on these specific bearings (This differs in each step and according to the pretensions of the cables as well), see fig (15). In the model I took into account the exact geometric profile of the finished structure, and the camber. I took advantage of AutoCad and Excel to get the nodal coordinates and transferred them to the geometry file in the software.
2) The properties of the different cross section were calculated manually and with the aid of Excel.
3) I calculated the weight of the nose and superstructure elements carefully, and I included them into the model. Also, I employed Tension-only trusses, nonlinear cable elements and beam elements. By using cable element (which simulate the reduction of the stiffness of the cable while it is sagging), I verified that the cables would not sag during launching; while the forces in the cables would tend to be almost zero in some increments. I utilized gap elements to simulate the changes in boundary conditions for each launch increment. The reason for using the gap elements in the model that the superstructure (in its real shape) would rest on the exact elevation of the supports when the gaps of these certain elements reduced to zero. As a result the displacement (which is the gap) will depend on the location of the superstructure over the supports as well as the structural deformations. I created an excel spread sheets to get the value for each gap during launching (at all increments that belong to a certain construction stage).
4) In the model, I used general-link element which is spring has 2 DoF. This represented the saddle of the temporarily cables at the top of the lead pylon. I selected the lateral stiffness for these elements to represent the friction of the cables over the saddle; while the vertical stiffness was very rigid. A very flexible spring support was included in the model to prevent the instability issues and singularity cases of the unsupported structure. 5m increment movements were analyzed in the software. I ran Geometric Nonlinear Analysis for this type of engineering problem. The 120 output result files were classified into 5 construction stages:
- CS 1: launch from SA to P1, 7 segments, 22 increment and 22 input files.
- CS 2: launch from P1 to P2, 3 more segments, 31 increment and 30 input files.
- CS 3: launch from P2 to P3, 4 more segments, 23 increment and 23 input files.
- CS 4: launch from P3 to P4, 5 more segments, 26 increment and 26 input files.
- CS 5: launch from P4 to P5, 2 more segments, 18 increment and 18 input files.
5) Due to variable support conditions during launching or even during the adjustment of the support elevations, a reversal of actions moments as the structure is launched will be created (with the combination of shear and axial forces), making the flanges and webs of the bare steel superstructure in complicated stress combinations. Through results I checked the general stability and safety during launching, In other words, I found the internal forces, moments, maximum stresses and the related structural safety margins. Fig. (16) shows increment cases in some construction stages.
6) I used lots of excel sheets to draw scattered charts for forces, moments and the nose tip location in space, taking into account the probability of encroachments inside the CP rail permitted envelope.
7) I confirmed the pretensions of the cables and their changes during launching increments, and compared them with the designer values. Also, I checked the displacements at the nose tip, girder tip and back span, see fig (17). When the forces in the cables increase the deflection of the nose tip decrease and the internal forces in the sections increase and vice versa. Adjustment of the temporarily cable’s forces was carried out for each stage (through negotiation with the designer and fabricator) to keep the deflections of any part of the superstructure, and for each increment within the permissible values. Also, attention was paid not to increase the forces to a level that would produce high internal combined stresses or plastic strains in the bare steel superstructure.
8) Like any other analysis, I did approximate hand calculation to verify the reactions, and all results.
The launching of the bridge was started in May 2009.
Figure (11) location of Coast Meridian Bridge 
Figure (12) Coast Meridian Bridge
Figure (14) Bridge Cross Section
Figure (13) Launching method that will be used to construct the bridge.
Figure (15) using the gap elements with the exact bridge profile, to get the best simulation of the displacement during launching.
