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Engineering Challenges in Construction

Radu Crahmaliuc - construction

During the design process in construction and building optimization, a large number of technical and standard criteria should be taken into consideration: structural behavior, seismic risks, spatial flexibility, energy efficiency, as well as thermal comfort and environmental impact.

At the same time, building optimization design is a process that needs multiple professions working interdisciplinary such as architects, building engineers and designers, among others.

In modern times, a large spectrum of computer software and more specialized applications packages were created for handling complex engineering projects. Nowadays we have dedicated applications for architecture, civil and industrial building, plants and factories, utilities and transportation infrastructure or special structures engineering.

With a wide range of functionalities, the SimScale simulation platform can be used to test and optimize designs in construction and architecture. Building optimization includes buildings, tunnels, roads, railways, canals, dams, flood, and bridges, using a wide set of analyses, including FEA/structural analyses, CFD/fluid dynamics, or vibration harmonic analyses of buildings and metallic structures.

  1. Structural and vibration analysis in construction engineering

When talking about structural behavior, every building engineering project is a challenge. Starting from local to general, in conventional design processes, the structural analysis is focused on the local structural behavior of each individual element: columns, beams, floor slabs, walls, roofs, windows systems, utilities pipelines, HVAC systems, etc.

Global structural analysis in buildings optimization is driven by sophisticated and complex analysis based on computer packages handling a huge volume of structure with a great number of elements. In a very comprehensive review, speaking about structural analysis in building, we can discuss about stability, frequency, and stress analysis based on critical load, fundamental frequency, and maximum stress and deformations [1]:

  • Basic critical loads include various coupling of basic models, concentrated top load, soils structure interaction and complex seismic risk analysis
  • Stress simple and multiple analysis can be made for horizontal loads (wind, seismic, compression, and misalignment), loads distribution, horizontal displacements, and rotations.
Golden gate bridge

Photo Source: Pixabay

Engineering masterpieces: San Francisco Golden Gate Bridge

 

Here are few most unknown facts related to Golden Gate history [2]:

  • First design project was rejected by the public being considered “ugly” or “a ponderous, blunt bridge that combined a heavy tinker toy frame at each end with a short suspension span”
  • Finished in 1937, it was the longest span in the world, until the Verrazano Narrows Bridge was built in New York in 1964.
  • Today, it still has the ninth-longest suspension span in the world.

A few Golden Gate Bridge facts and figures:

Total length: including approaches, 1.7 miles (8,981 feet or 2,737 m); Middle span: 4,200 feet (1,966 m).; Width: 90 feet (27 m); Clearance above the high water(average): 220 feet (67 m); Total weight when built: 894,500 tons; Total weight today: 887,000 tons (weight reduced because of new decking material); Towers: 746 feet (227 m) above the water, 500 feet (152 m) above the roadway; Steel Facts: made in New Jersey, Maryland and Pennsylvania and shipped through the Panama Canal; Total weight of steel: 83,000 tons (75,293,000 kg); Cable Facts: Two main cables pass over the tops of the main towers; each cable is made of 27,572 strands of wire. There are 80,000 miles (129,000 km) of wire in the two main cables; Cable diameter (including wrapping): 36 3/8 inches (0.92 m); Cable length: 7,260 feet (2,332 m); Traffic average crossings: about 41 million/year.

The SimScale Public Projects are offering various types of analyses for bridge structures. The truss bridge is one of the most common structures analyzed in infrastructure design. A truss is a structure of connected elements forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. Due to their good strength and durability, truss bridges normally serve for automotive or train rivers crossing.

In this truss bridge eigenfrequency analysis, natural frequencies are considered. Assuming the structure may vibrate without any external load, the truss bridge is simulated for its first 20 eigenmodes. The geometry created with Onshape was uploaded to the SimScale platform. The figure below shows the displacement modal magnitude for deformation of the truss bridge at eigenmode 13. The animated version of the final model can also be found here.

Truss Bridge Analysis with SimScale

Another SimScale project is this bridge elastomer bearing pad using a nonlinear static analysis. The elastomer bearing pads are mostly used to smoothly distribute the load of the bridge beams to substructures and sustains the compression, shear and rotational load of the bridge. The elastomer model was meshed with second order hexaderal mesh in order to get accurate results with minimal elements distortion. Steel was selected as a default material for the plates in this analysis and signorini hyperelastic model was used for the elastomer material. Three types of common elastomer pads deformation cases are simulated:

  • Compression
  • Compression with shear
  • Combined (compression with rotation)

For all the cases, bottom face of the lower steel plate is constrained in all directions. For compression, the top steel plate is displaced by 1 cm in the negative z-direction. Furthermore, with the same compression, the top plate is displaced by 4 cm in positive x-direction for the shear case and rotated 2 degrees along positive y-axis for the combined deformation case. The figure below shows the results of the Cauchy stress (σz) contour plots for compression with rotation. It can be seen that the stresses are equally distributed in the elastomer due to reinforced steel plates.

Elastomer bearing pad analysis

Other interesting case for special engineering projects is high-building vibration and airflow analysis. SimScale is offering us an interesting simulation of Olympia Tower Munich, one of the iconic building structures in the Bavarian city.

Olympia Tower Munich

Photo source: Pixaby

Engineering masterpieces: Olympia Tower Munich – placed in the Olympic Park from Munich was built for the 1972 Summer Olympics. It has an overall height of 291 m and a weight of 52,500 tons. At a height of 190 m there is an observation platform housing called “Rock Museum”. At 182 m, there is a revolving restaurant, which seats 230 people. A full revolution takes 53 minutes. [3]

In the first Olympia Tower project, a frequency analysis has been performed considering the first ten natural eigenfrequencies. The tower’s geometry provided by Filippo Balloni was imported to the SimScale platform. The geometry was meshed using parametrized tetrahedralization. The bottom of the tower was fixed in all directions and then the simulation was run for the first ten eigenfrequencies. The displacement modal magnitude for mode 3 can be seen in the figure below.

Olympia Tower Simulation

In a second project, the harmonic and static analysis subjected to a wind pressure was performed. The same tower geometry was imported to SimScale and was meshed using the same parametrized tetrahedralization. Both the static and harmonic analyses were performed. The bottom of the tower was fixed in all directions and a surface load of 500 N/m² was applied in negative x direction on the above red highlighted faces. Two harmonic analyses were performed with one having probe point on the top of the tower and the other with probe point on the restaurant. The displacement and vonMises stresses produced in the tower due to the wind pressure (static analysis) are the main simulation results shown of SimScale Public Projects. Other results are showing the real x, y and z (article figure) displacements from harmonic analysis), and two graphs showing the real displacement in x direction vs. frequencies computed on the probe point of tower top and restaurant respectively.

Olympia Tower simulation with SimScale

         2. CFD analyses in buildings construction and infrastructure

HVAC simulation and CFD analyses are important building optimization tools which are used for evaluation of building performance, including thermal comfort, indoor air quality mechanical system efficiency and energy consumption. In buildings, simulation is mainly being used for the followings purposes:

  1. Thermal analysis: through walls, roof, and floor of the buildings
  2. Ventilation and airflow analysis
  3. Orientation, site, and location selection of buildings – based on local geographical and environmental conditions.

In buildings design, both external and internal airflows are generally considered:

External airflow analysis:

  • New building positioning to minimize “canyoning” effects
  • Pressure distribution on structures and wind impact on pedestrian comfort
  • Using elements like walls, trees, and landscape to improve the wind flow patterns
  • Courtyards designing

Closely related to building performance simulation (BPS), the internal airflow analysis is proposing to solve:

  • Expected airflow rate and temperature at a given location
  • Efficient design of HVAC systems
  • Designing building spaces and atria to better ventilation

Engineering masterpieces: Energy Saving System from Chicago Sears Tower (Willis Tower) 

Willis Tower

Photo Source: Radu Crahmaliuc

 

With its 527 m structure (including antennas) high, the Sears Tower was the highest civilian building structure in USA until the finishing of ONE World Trade Center (opened in 2013, 546 m high). Besides the impressive dimensions and architectural concept, the SkyDeck is very interesting for his advanced energy saving model [4]. Each day heat builds up inside the skin of the Willis Tower. Sunlight pours in the windows; computers and other electrical equipment generate heat; and all those warm people help push the temperature up. A sophisticated air-handling system cools, filters and circulates air throughout the building. The air comes in and out of each floor through ceiling vents. Sometimes heat is needed on the shady side of the building. Or perimeter heating is needed all over on cold winter days. At the direction of the command center, air can be filtered and exchanged between the warm and cool areas of the building or electric boilers can supply heat throughout the offices on the perimeter. On the main mechanical floor are enormous chillers. These large refrigerator units cool water to chill the air and pump it to major physical plant areas throughout the building, where it is then circulated to each floor. Four large cooling towers three stories high on the 106th – 109th levels take water already used by the chillers and cool it down using fans as the water runs down the inside of each tower.

 

The most common analysis for buildings is airflow research for wind velocity and pressure field simulation. In this basic simulation related to airflow around a building, a CAD model of the building has been uploaded to SimScale in STEP format. The mesh was generated using the automatic hex-dominant mesh operation for external flow. In order to minimize effects of the bounding walls, a virtual wind-tunnel around the building was set to 350x350x300m. The resulting mesh consists of a little more than 400.000 cells. The simulation was set up using the steady-state incompressible flow analysis type with a k-Omega-SST turbulence model. The airflow was simulated at 10m/s incoming wind velocity. For this simple simulation setup, the effect of the ground is neglected. In this case, the results allow the visualization of wind velocities as well as the pressure field around the building. The acting force onto the building can therefore be computed.

Airflow around a building with SimScale

Starting from a individual building airflow analysis, it is possible to extrapolate the simulation for a building ensemble, a residential area or for a city. In this airflow around Singapore simulation, a CAD model of Singapore city has been uploaded to SimScale in STEP format. The mesh was generated using the automatic hex-dominant mesh operation for external flow. The flow domain around the buildings was set to 8000x8000x1200m in order to minimize effects of the bounding walls. The resulting mesh consists of a little more than 3,000,000 cells. The steady-state incompressible flow analysis type with a k-Omega-SST turbulence model was set up for the simulation. The airflow was simulated at 5m/s incoming wind velocity. Like in the other case presented here, the effect of the ground was neglected in this first simple simulation setup.

Singapore simulation with SimScale

All the projects presented in this article can be imported into your own workspace and used as templates. If you want to learn more about the benefits of using engineering simulation in Architecture and Construction, click here.


References:

[1] Zalka, K. – Global Structural Analysis of Buildings, E & FN Spoon, 2000

[2] McCarthy E. – 20 Awesome Facts About the Golden Gate Bridge, Mintal Floss, May 2015.

[3] Wikipedia https://en.wikipedia.org/wiki/Olympiaturm

[4] Fead K. – The Hows, Whats and Wows of the Willis Tower – A Guide for Teachers, Skydeck Chicago, U.S. Equities Realty, 2009

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