Wood is a very easy-to-work material, allowing professional and amateur builders to manufacture simple objects and structures without major problems. However, when thinking about larger-scale housing or buildings, it’s important to take certain precautions that ensure good quality and good construction behavior. To this end, it’s essential to evaluate every project and analyze which connection system best suits its structural and aesthetic needs.
We spoke with the experts of Simpson Strong Tie, a leading company in structural connectors, anchors, and fastening systems, to learn more about these topics. Here are six important lessons and tips for building safer and more resistant wooden houses and buildings.
Architects have to be candid with themselves: they are not experts in everything, nor do they have to be. For this reason, it’s important to collaborate with and trust professionals and technicians in other areas, especially when it comes to complex construction solutions. Simpson Strong Tie’s value lies in developing the best possible project according to the user’s requirements, trusting that these different solutions will meet the engineering requirements and effectively adapt to each design.
To achieve this goal, we recommend always having some considerations in mind:
1. Structures built with connectors are stronger than those built only with nails or bolts, allowing greater safety and durability
Available in a wide variety of shapes and sizes, structural connectors are made of steel and are designed to join the different elements of the structure, helping to prevent damage caused by earthquakes, strong winds, and other threats.
Connector systems, in comparison to joining only with nails, not only deliver a greater capacity for resistance to the structure, but also improve its ductility. In a strong wind storm, for example, it’s likely that nails will work much less efficiently than connectors, separating the joint and failing to correctly transmit the forces from one element to the other. A metal connector is the safest and most efficient way to transmit the entire efforts of the structure to the foundation.
2. The components of a connection system must be work jointly towards a better structural performance
The joint system must be an integrated solution; once the wooden elements and their meeting points are designed, the structural connections must be considered. Taking into account the continuity of the load path of the structure as a whole (beams, pillars, trusses, etc.), all loads that occur in the structure must be taken, as quickly as possible, to the foundation. If one of the connections is lost, a partial or even total collapse of the construction could occur.
In addition to the structure’s own weight (dead load), it’s necessary to consider different types of live loads to resist. The effects of an earthquake first manifest in the foundations, are transmitted to the rest of the structure and then return to the foundation again. On the contrary, wind or snow loads occur at the highest part of the structure, and must be quickly brought down.
3. Poorly chosen connection system components can cause corrosion damage, impacting the structural design completely
The first elements affected by corrosion are the connectors. They then begin to contaminate the wood and enter a cycle extremely harmful to the structure. Too high a degree of corrosion can even cut the steel part, its fixation, or considerably weaken the strength of the wood, losing the structural connection and thus the continuity of the load path.
It’s very important to ensure the compatibility of the connector and its fixings as well as the type of corrosion protection, in the case of use. The essential consideration is to correctly select the connection system depending on the degree to which it will be exposed.
4. A modification of the original project cannot be improvised in the field: the structural elements must not be altered without considering such modifications in the design
Usually, basic errors are made at the construction site that can affect the effectiveness of the entire structure. For example, when installing plant pipelines, some pieces of wood are drilled to let them pass. This can seriously affect the continuity of the load path.
Although the structure may not collapse when facing dead loads, an interruption nonetheless causes a redistribution of the charges, forcing them to be received by another element that was not originally designed to fulfill that function. This can have great consequences when a lateral load is imposed, such as during an earthquake or high winds.
5. The connection system is determined according to the quality of wood and its dimensions
The wood should be chosen first, only after which one can consider the most appropriate connector for it and for the characteristics of the structure. There are connectors that work correctly for different types of wood, and others that are recommended for specific woods.
In the case of exposed wooden structures – for example, those composed of pieces of glued laminated wood (Glulam) – hidden connectors are generally used, leaving a clean wooden structure to be viewed by the casual observer, or failing that, connectors with an attractive design and consistent with the rest of the project. The sections of the wood, which depend on the loads that each point of the structure will receive, will also guide the choice of connectors.
Hidden Connector Example
Exposed Connector Example
6. There exists a software that can help in the process
With the aim of working together with professionals in the area, there exists software that facilitates the process and allows a clearer idea of the structural solution best suited to the application. CG Visions, for example, saves costs and improves the efficiency of the structure in general, helping architects evaluate, select, and implement technological solutions from the early stages of the project.
Application Example: Peñuelas Experimental Tower, 6 floors in wood
Nearing the end of 2018, Minvu and the ‘Wood Innovation Center’ of Universidad Católica (Corma) opened the Peñuelas Experimental Tower in Chile in the National Reserve of the same name. Over the course of 18 months, studies were carried out on the structure’s behavior, investigating how to create effective constructions from materials unique in Latin America. The design and construction of the tower were led by the architect Eduardo Wiegand, and it is 20 meters high and covers an area of almost 120 m2.
According to the former Director of CIM UC and current President of Corma, Juan José Ugarte, wood improves environmental sustainability, energy efficiency, and seismic response capacity. In addition to the use of Simpson Strong Tie connectors and fixings, the Strong Rod system (ATS, of the same brand) has been used in the structure to improve the seismic and wind resistance of the structure.