A3 Sachin Patel

A3 Truss Analysis:

 Those were the pictures for my Calculations using the MOJ.

The force calculations done by the online simulator.

The online simulation for Our own bridge design. 

Analysis: 

 Using the method of joints on the online simulator helped us get realistic numbers for own own 

A3-JACOB

1.Calculations of forces in  the truss members using the Method of Joints.

Truss Bridge That was used in Method of Joints

Calculation of Forces via Method of Joints (MOJ)  - 1

Calculation of Forces via Method of Joints (MOJ)  -  2

Labeled Diagram showing results of MOJ.

2.Results of the Analysis

From the truss analysis it can be concluded that the members connected to the center node will have tension and the members not connected to the center node will have compression.

 3.

Bridge Designer Image Replicating MOJ

4.

The bridge designer is a very convenient method for calculating the tension and compression of each member in a Truss bridge design. The data collected from hand analysis and the online Bridge Designer is very similar. In order for both analysis to correspond, the length of the members and the angles must scale to each other. In Bridge Designer, each block represents 2 inches in length. Therefore, the ratio between the members must stay the same for the angles to stay the same. 

5.

Bridge Designer Applied to our Knex Truss

6. How to Use Analysis to Improve the Design of Knex Bridge

Using the method of joints analysis, we can determine a value of the tension and compression of members of the bridge for a given load. The testing information about the K’NEX rods and K’NEX connectors provides the tensile pull-out force for various modes of connection. The web page displays three different modes of connections that contain different number of membranes connected to one connector. Analyzing the tensile pull-out force, it is evident that the pull0 out force increases with the number of membranes attached to the connectors. I was also ale to observe that the pull out-force greatly increased going from Mode 2 to Mode 3 rather than Mode 1 to Mode 2. This Tensile pull-out force table is useful in understanding that the how the number of membrane to connector ratio directly correlates with the stability of the bridge. From this information, our objective for this week would be detected the weakest connections and strengthening it by additional membranes.

Week 8 - Analysis Process

The Method of joints is a nice approach to calculating the force load of the bridge. However, this method wouldn’t be sufficient for constructing a bridge in the real world. In a real world, there are many other forces that need to be considered such as the load of the bridge itself.  Method of joints mainly focuses on the forces going vertical, but in real world there are horizontal forces that impact the tension and compression of the members in a bridge design. Some of the other forces that can impact a real bridge would be the wind, location, weather and natural disasters like earthquakes. I would like to learn more about the each connectors and how the strength increases with more members get attached to it. I would also be really interested in learning about software like Bridge Designer that makes calculations more convenient.  

During the previous week in class, we discussed the new set of constraints for our K’NEX bridge. The Bridge is required to span 36 inches with a minimum width of 3.5 inches. Along with that the bridge must be a tube for the vehicles to drive across the bridge. Majority of the class focused on learning the proper method drawing free body diagrams, as well as calculating the forces using the method of joints. Method of joints can be used to calculate the tension and compression in the membranes involved in the bridge design. Using the calculated values, we can improve the design of our bridge. This week in lab, we will be conducting more truss analysis and finishing up the final design of the bridge.

A3 - Parth Patel

1) Method Of Joints

2) Results of Analysis

3) Bridge Design Replicate

4) Hand Analysis Correspond to Bridge Designer

          For the hand analysis to correspond with the Bridge Designer, the length of the membranes need to be scaled equally. In Bridge Designer, the length is contained and scaled to 2 inches per graphical unit, while on the hand drawing we can draw membranes at any sizes. Therefore, Bridge Designer needs to scale their bridge so the forces correlate with the values calculated.


5) Bridge Designer for Knex Bridge

6) Final Analysis

          According to the Knex joints test page, it shows that it requires more force to remove a membrane from a 180 gusset plate as the number of membranes added to the gusset increases. Using the given average pull-out force for the different types of modes, such as one, two or three attached membranes, we can compare it with our Knex truss bridge. The online Bridge Designer has already computed the values of forces applied on each membrane of our bridge; so now we only need to identify the membranes close or far from the maximum limit of force. Than we could adjust those certain membranes to build a better cost to weight ratio bridge. For example, if a membrane if suffering force close to its maximum capacity, we can add more membranes in that region, such as to the gusset plates to make a stronger bridge. Similarly, if a membrane is suffering very few amounts of force, we could take the piece out and reduce the estimated bridge cost.

Week 8 - Analysis Process

      In my opinion, “Method of Joints” for analysis is not sufficient enough for a real bridge in a realistic situation. First of all, the load applied on a real bridge is different than the situation we considered for class where it only has vertical force. A real bridge will have force from all directions, for example the horizontal load from wind. Also the size and type of membranes included on a real bridge will contribute to how much load is actually felt on the joints. Another factor is the constant change of load applied on a real bridge, such as number of vehicles or weather patterns. Therefore, there will be a constant variation of forces applied on each membrane and joints.  In addition with “Method of Joints” I would also like to know the strengths of each membrane and joint so I could predict at which forces will the bridge collapse due to the specific parts. One more think I would like to analyze is the failure of the two 180 grooved gusset plates because they are found to be weak and caused our first bridge to easily collapse. 

       Last week in lab we discussed how to analyze the forces applied on a bridge by using the process called “Method of Joints.” With this method, students are able to learn how to compute tension or compression forces felt on each membrane of the truss bridge. This mathematical tool can help students compute the forces applied on their Knex bridges and make adjustments for a better result. For example, if certain membrane is experiencing a great amount of force, the best method is to make that area strong and compatible for the load applied. This week in class we will finish designing a truss bridge that will span over 36 feet and follows the new constrains. This will be the second bridge that the students will be testing in class.