**3.3. Cantilever bridge deck construction**

**3.2. Incremental launching method**

66 Structural Bridge Engineering

type of cross section is the box girder.

nose are assembled;

(available in [14]).

and displacement of the element takes place.

**Figure 12.** 3D models of the construction elements and landscape.

Another interactive model for the construction of bridge decks was created. The construction of bridge decks using the incremental launching method has existed from the 60s. This method consists of casting segments of the bridge deck in a provisional formwork, and then, each segment is pushed forward along the bridge axis. This method is used in viaducts crossing high valleys. The cross section of the bridge must have a constant height, and the most suitable

Using the VR model is possible to follow the visual simulation of the construction sequence and to learn how the equipment is moved [15]. In order to perform correctly, the construction simulation activity every construction components and equipment was generated as 3D

**•** the external panels of the shuttering are first placed followed by the reinforcement mesh;

**•** after, the interior false work is placed incrementally in sequence, starting with the metallic element, followed by the longitudinal beams, the shuttering panels and finally the launching

**•** a first segment is casted, the nose is removed, the segment is separated from the shuttering,

For the following segments, the process is identical. In the final phase of the construction the worksite yard is removed. Finally, all the finishing elements are positioned. Because consid‐ eration was given during its development, both to technical knowledge and to its use in education, in particular how and what to show, the 4D model could be an important teaching tool to illustrate bridge construction issues during training. The application is designed, not only as a learning tool, but also for use by professionals involved in the construction of these types of bridges. Note that a film was created showing the interaction with the VR/4D model

models (**Figure 12**), and the EON studio, a VR‐based software, was used [16].

The main steps of the construction process are as follows (**Figure 13**):

A further 4D model allowing the simulation of the cantilever method was created [17]. Students and teachers are able to dictate the speed of the process, in order to observe the movement of advanced equipment and how to place each elements of the bridge. The sequence performance is programmed using the VR software followed by an appropriate planning guides for this type of construction.

The case study has a box girder cross section, and its height varies parabolically along three spans. The most common construction technique for this typology is the cantilever method of bridge deck construction.

The aforementioned computer graphic system allows the generation of the deck segments needed for the construction simulation of the bridge [5]. To complete the virtual scenario of the construction site, the advanced equipment, the formwork adaptable to the size of each segment, the platforms for the workers and the false work to be placed near the abutments were also modelled (**Figure 14**).

**Figure 14.** 3D models of a deck segment, the scaffolding and the advanced equipment.

The input and support of bridge designers, not only on the geometric definition of the bridge components and devices, but also on the establishment of the progression sequence and the way the equipment operates (**Figure 15**) were essential to obtain an accurate model:


**Figure 15.** Sequence of the cantilever construction process.

In a real construction site of a bridge, for security reasons, the student is obliged to stay far from the zone where a bridge is under construction and thus cannot observe, in detail, the methodologies or the progression of the construction. However, while using the interactive virtual model, by moving the camera closer to the virtual bridge and applying to it routes around the zones of interest, the student can follow the sequence specifications and observe the details of the configurations of the construction components. Being able to interact with the bridge models therefore should help students gain better understanding.

## **3.4. Integration of interactive capacities**

The attribution of virtual properties to the models in each application was defined by using the VR‐based tool, the EON studio [16]. The implementation of the interactive model, con‐

**Figure 16.** Software used on the implementation of a VR model.

cerned with the incremental launching method, is based on several linked applications as shown in the chart in **Figure 16**.

In the implementation of the 4D model for cantilever method, 3D models of the box girder bridge and of the environment were transposed (as 3D Studio Objects in **Figure 17**) to the EON Studio. The EON system is object programming‐based software: the nodes window contains all actions that can be associated to the elements included in the simulation tree window. For instance, the advanced equipment model is identified, in the simulation tree shown in **Figure 17**, as a group or frame, designated as a "car."

**Figure 17.** 3D model of the advanced equipment in 3DS format and the EON system main interface.

The definition of the construction sequence is based on a *counter* option button, which determines the next action in the process. The first action consists of the insertion of pillars in the landscape. When the components of the model are transposed to the EON, every element, except the landscape, is associated with the hidden characteristic The order to display an element is commanded by the counter node (**Figure 18**), which contains the logical instruction, which means when the value in the *counter* is accurate, then the associated element will be displayed. Consequently, when the mouse is clicked, the counter indicates the next element to be displayed. The correct programming will simulate the steps of the real bridge deck construction.


**•** a first segment is concreted on each pillar and is installed the work equipment on it;

**•** finally, near the abutments, the deck is constructed, using a false work.

and using the advanced equipment;

**Figure 15.** Sequence of the cantilever construction process.

**3.4. Integration of interactive capacities**

**Figure 16.** Software used on the implementation of a VR model.

equipment;

68 Structural Bridge Engineering

**•** the process of concreting segments is defined in symmetrical way, starting from each pillar

**•** the continuity of the deck is established with a closing segment, using just one advanced

In a real construction site of a bridge, for security reasons, the student is obliged to stay far from the zone where a bridge is under construction and thus cannot observe, in detail, the methodologies or the progression of the construction. However, while using the interactive virtual model, by moving the camera closer to the virtual bridge and applying to it routes around the zones of interest, the student can follow the sequence specifications and observe the details of the configurations of the construction components. Being able to interact with

The attribution of virtual properties to the models in each application was defined by using the VR‐based tool, the EON studio [16]. The implementation of the interactive model, con‐

the bridge models therefore should help students gain better understanding.

#### **3.5. Educational considerations**

The aim of the practical application of the VR models is to provide support in civil engineering education, particularly in those disciplines relating to bridges and construction processes in classroom‐based education. They can also be used to assist professional training and distance learning based on e‐learning technology. When this visualization tool was being designed, human perceptual and cognitive capabilities were taken into account [18]. It means that the program is suitable for use in a wide range of learning environments or stages of education.

The traditional way to present the curricular subjects involved in these virtual models is through 2D layouts or pictures. By using the 4D models, teachers may help the students to visualize and engage with the construction process more interactively. The following are some advantages of using the 4D models:


The introduction of the VR model as a new teaching tool in construction and bridge disciplines has been well accepted, although some difficulty in the manipulation of the model was reported. However, this kind of new technological material, based on 3D/4D interactive models, is important in a modern class setting and deserves attention.

Teachers are the key players in the educational process and are the main determiners of quality in the classroom, so they must be kept up to date with new technological material that can contribute to the enhancement of quality in education. Therefore, this new concept of VR technology applied to educational models can bring new perspectives to the teaching and learning process for civil engineering education.

**Figure 19.** The models show in detail the movement of the equipment during the construction process.

**Figure 20.** The menu of events supports interactivity with the model.
