Reference no: EM132302079
Design of Highway Bridge Superstructure Systems (A)
The design bridge is illustrated using the twin bridges over Nambucca Flood Plain (BR14) as an example.
Figure 1: (a) the plan of twin bridges 14; (b) the plan of HW10 pacific highway upgrade warrell creek to Nambucca heads, which shows the location of twin bridges 14; (c) the longitudinal section of twin bridges 14; and (d) the photo of twin bridges 14.
The twin bridges are nearly completed with each bridge carrying one-way traffic. The bridge A (on the northern carriageweay, Fig. 1(a)), is a road bridge with three spans (24.0 m + 26.0 m +22.0 m), as shown in Fig. 2. For bridge A, the road is designed to have two traffic lanes, as shown in Fig.3. The vehicle parapet is located on each side.
Figure 2: Longitudinal elevation
Figure 3: Cross Section
The bridge A is a beam bridge and the deck system is the cast-in-place reinforced concrete slab. Design the superstructure systems of the bridge A based on material properties prescribed below.
Material properties (Material properties, which are not given here, should be found in AS5100. 5 and AS5100. 6)
Reinforced concrete density = 25 kN/m3 Concrete density = 24 kN/m3
Density of bituminous wearing surfaces = 24.5 kN/m3 Thickness of bituminous wearing surfaces = 0.065 m
Pre-Design Activities
a) Select the deck supporting system. (It is recommended a steel I beam, but the prestressed concrete beam is also permitted.)
b) Estimate the depths of structural members based on span/depth ratios.
Loads and Load combinations
Design information and requirements:
Only structure dead loads, superimposed dead loads and vehicular traffic loads are considered in the load combinations. Regarding vehicular traffic loads, M1600 and W180 moving loads are considered to find the most critical case for the bridge.
a) Find the dead and superimposed loads. For the assessment of dead and superimposed loads, the following elements are considered: structural members, parapets and non- structural elements such as bituminous wearing surfaces. The dimension of parapets is given in Fig. 4.
b) Determine load factors, reduction factors and load combination factor.
c) Determine load combinations for both ultimate limit state and serviceability limit state.
Structural Analysis
Design information and requirements:
The structural analysis can be carried out either using the software package such as Space Gass or using beam-line simplified method.
When the latter is used, the distribution factor for moment and shear can be determined according to AASHTO method. If the first method is used, the modelling file must be submitted.
Fig. 4 (a)
The beams allow to be designed as simply supported for structural dead loads, superimposed dead loads and vehicular traffic loads.
a) Decide whether the beams are simply supported (at piers) or continuous for loads.
b) Carry out a longitudinal analysis of the bridge to determine the envelope of maximum bending moments and shears. Plot the envelopes of moments and shears (both negative and positive) of interior beams (in Span 1). The ultimate design loads of the interior beams should be presented in a table.
c) Carry out a transverse analysis of the bridge deck. Plot the deck ultimate design moments diagram. The ultimate design value should be presented in a table.
Deck Slabs Design
a) Design for ultimate positive flexure.
b) Design for ultimate negative flexure.
c) Design for punching shear.
Design of Steel I beams (Interior Beams in Span 1)
a) Design for flexural capacity under ultimate limit state.
b) Design for shear capacity under ultimate limit state.
c) Check serviceability limit state.
Additional Information
All design and detailing is to be in accordance with AS 5100.1, 5100.5 and 5100.6 (2017). All loads are to be determined using AS 5100.1 and 5100.2 (2017).
Presentation of the Assignment
It should be legible and logically arranged. A typical presentation would contain, in order: a title page including names of structural engineers involved in the design, detailing of structural elements in applicable sections, supporting calculations in each section, and appendices containing any appropriate technical information.