In situations where we need to find the internal forces only in a few specific members of a truss, the method of sections. The results showed an average reduction in cost for the truss bridge of approximately 3% by using the optimised geometry. Depending upon the site conditions and the span length of the bridge, the truss may be either through type or deck type. Of course, designbuild project delivery also has its disadvantages. This is our final calculations for the final design we choose the biggest compression load from the software is 92 when the applied force is 100. We will develop a truss configuration, analyze the struc. Method of sections the method of joints is good if we have to find the internal forces in all the truss members. Simple truss solver, as the name suggests, is a free truss design calculator software. These results are compared together in order to identify the most optimal bridge.
The purpose of this example is to illustrate the use of the aashto lrfd bridge design for the design of a continuous two span steel igirder bridge. Trusses have a very high strengthtoweight ratio, which allows them to span long distances. We will use the software to create a structural model, then run a simulated load test to evaluate the design. Pdf a bridge must be designed to safely resist all loads and forces that may. The truss bridge was designed to determine member sizes, extract a bill of materials and apply live project cost rates for a range of geometry. Aashto specification references are presented in a dedicated column in the right margin of each page, immediately adjacent to the corresponding design procedure. The design process and corresponding calculations for steel igirders are the focus of this example, with particular emphasis placed on illustration of the optional moment redistribution procedures. In this learning activity, we will analyze and evaluate one of the main trusses from the grant road bridge.
It lets you draw a truss structure and calculate truss problem. Design manual for bridges and structures sixth edition, 2016 nj. Truss facts book an introduction to the history design and mechanics of prefabricated timber roof trusses. Pratt truss design and stress analysis with concept youtube. In addition to the three basic truss systems, there are many other structural forms developed in the bridge design practice, as shown in fig. In the through type, the carriage way is supported at the bottom chord of trusses.
The goal of this project is to investigate the tensile and compressive forces in structural members. When we design a structure, we need to select members that. Planar truss, on the other hand has a 2dimensional design. Nov 09, 2017 design hub pratt truss design in solidwork. Users can also control settings such as units, display settings of truss members etc. It comes with some predesigned projects including bridge 3 trusses with forces, one truss tension, vaulted parallel chord, etc. Worked examples presented at the workshop bridge design to eurocodes. Steel truss member strengthening design example fhwa. Rating factor and tonnage calculations for truss members.
Design and build a model truss bridge bridge design contest. The soil of the site was identified as site class b rock and the highest importance category, iv was assigned to the structure. Njdot design manual for bridges and structures 6th edition, 2016. Background a truss is a rigid framework whose internal members are connected in a triangular pattern. Design of a truss bridge for low cost using structural. Four lrfd design examples of steel highway bridges, vol. Show full abstract design of steel truss bridge, the bridge is 40m long and 12 m width and 8 m high, the spaces between the trusses in the roof are various, from the beginning we leave space.
Common types of trusses bridge trusses in particular, the pratt, howe,and warren trusses are normally used for spans up to 61 m in length. We were given specific specifications that we needed to follow, or else or. The structural calculations included here are for the analysis and design of primary structural system. Truss bridge the american association of state highway and transportation officials aashto needs your help in designing a model of a truss bridge made completely out of paper. Edsgn100 truss bridge design final design report executive summary we were approached by a company to design a bridge that was strong, aesthetically pleasing, and economically efficient. Dec 06, 2012 bridge design tutorial pratt vs howe truss duration. The trusses were designed with and without the use of a steel beam along. The sto procedure indicated a strong preference towards the warren truss as being the optimal shape for a bridge of this type. Bailey bridge missouri university of science and technology. This design example is targeted at bridge owners and bridge engineers who have been. What are truss bridge designs and how do they really work. All sam ple design calculations are based on the lrfd bridge design specifications, 5th ed. It incorporated triangular trusses that extended to the maximum height allowed which created stability and helped dissipate the weight throughout the members.
Model truss bridge design murray states digital commons. We were to come up with a prototype using wood craft sticks and white elmers glue. Bridge design to eurocodes worked examples worked examples presented at the workshop bridge design to eurocodes, vienna, 46 october 2010 support to the implementation, harmonization and further development of the eurocodes y. Truss is a structure which is commonly used in the construction of bridges. The truss analysis is being performed by our fea solver, which is also used in our structural 3d program. Design employed prefabricated panels and parts can be carried by trucks and assembled using manpower alone erection using simple tools ropes, pulleys, jacks and hammers can be moved, rebuilt, or replaced in several hours, even under enemy fire. For larger spans, a truss with a polygonal upper cord, such as the parker truss, is used for some savings in material. Pdf analysis and design of steel truss bridges researchgate. The small construction depth reduces the length and height of the approach embankments that would be required for other deck forms. In this example it is considered that there is no need for a dynamic response procedure. Click reactions or axial force to display your results in a nice, clean and easytointerpret graph for your truss design. This design example, steel truss member strengthening, involves the addition of steel cover plates to steel truss members.
Overview of the activity in this learning activity, we will use a specially developed software package called the west point bridge designer to design a truss bridge. The project discussed analysis and design of steel truss bridge, the bridge is 40m long and 12 m width and 8 m high, the spaces between the trusses in the roof are various, from the beginning we. Trusses are generally used for bridge spans between 30m and 150m where the construction depth deck soffit to road level is limited. We will create a mathematical model of the truss, then use this model as the basis for a structural analysisa series of mathematical calculations to determine the internal force in every member of the truss. Lrfd design examples nhi course 081 load resistance factor design lrfd for highway bridge superstructures, design examples pdf, 7. Such structures are frequently used in long span structures such as truss bridge design and roof trusses. The most elementary 3d space truss structure is the tetrahedron. Therefore, three different designs based on each of the design standard are included in this project. In short, we used known values of internal force and strength to calculate unknown factors of safety. Design of industrial truss university of asia pacific. The project discussed analysis and design of steel truss bridge, the. There are four main assumptions made in the analysis of truss. Steel truss bridge design example truss stress mechanics. Structural evaluation of tiedarch and truss bridges.
Design of sackett harbors bridge worcester polytechnic institute. Steel truss bridge design example free download as excel spreadsheet. The most common form is the warren truss with verticals. In the process of designing a truss bridge, along with application of newtons laws of motion, certain assumptions are taken. The members are connected with balland socket joints. Components of a space frame truss attain a 3dimensional form. These calculations shall govern the structural portion of the working drawings. In this project, several wood bridge design options were proposedas future replacements for. Steel truss bridge design example free download as excel.
Truss height m spacing between two truss m b3 load factors as per table 1 bs 5400 part 2. Consider structural slab thickness for ratingdesign. Define the bridge data, material properties, section properties and existing dead load member forces. In the design procedure for the support beams, the dead load was. The calculations made are based on splitting the member into 10 smaller elements and calculating the internal forces. After the approval of the design, the final design work can begin with rigorous calculations of forces, stresses etc. Teacher tips objective students will design and build a truss bridge to span a 61 cm 24 in open space.
The third chapter presents and contains the design calculations of slab, stringer and. We will analyze the owners needs, then formulate specific design requirements. How to design a bridge bridge structural designing steps. Truss members are connected together at their ends only. Members of truss bridges, no matter the design, share a common. The scaffolding and equipment, which will be needed for the construction of the particular type of bridge, also has to be worked out. Upon the completion of structure analysis, the truck load as well as other live loads and. Steel bridge design had not been standardized each bridge was an original design that requires time and money, whereas concrete bridges are standardized designs the sssba developed standard simplespan and modular designs espan140 short span steel bridge design. Simple space trusses can be obtained by adding 3 elements at a time to 3 existing joints and joining all the new members at a point. Overview of the activity in this learning activity, we will design, build, and test a model truss bridge. However, where any discrepancies occur between these calculations and the working drawings, the engineer shall be notified immediately so proper action may be taken.
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