A few days ago, the partial collapse of a 60 cm thick tapia party wall at the old Beat Domènec Library in Esparreguera highlighted the structural importance of discharge arches in historic buildings. This collapse, caused by the instability of the tapia wall, could have resulted in widespread damage to the building if it had not been for the effectiveness of the formation of a discharge arch on the upper floor. This formation prevented the direct transmission and diversion of the upper loads to the sides of the damaged wall, ensuring the stability of the entire structural system.
Tapia and its Structural Limitations
Tapia, a traditional material made of compacted earth, has been used in many constructions due to its availability and thermal efficiency. However, it has structural weaknesses, particularly when subjected to tensile stress or concentrated compression. Tapia walls can lose integrity due to erosion, moisture, or alterations in load distribution, as seen with this party wall.
At the Beat Domènec Library, the loss of cohesion in the wall was caused by the direct entry of rainwater through the roof, which initiated a sliding process that could have led to the total collapse of the structure.
Discharge Arches: Efficient Load Redistribution
Curved discharge arches redistribute vertical isostatic forces toward stronger areas of the walls and are essential for maintaining the stability of wall structures. In this particular case, the formation of a discharge arch on the upper floor played a decisive role:
- Diverting the Upper Loads: The arch transferred the weight of the 60 cm wall, the floors it supported, and the roof to the stable sides of the wall.
- Preventing Progressive Collapse: The sliding of the tapia did not affect the adjacent areas thanks to the structural decongestion provided by the arch.
- Protecting the Rest of the Building: The redistributed load allowed the remaining wall to maintain its stability and functionality.
This formation, which appeared simple in behavior, was crucial in preventing more severe damage.
Rehabilitation and Structural Reinforcement
As the person in charge of consolidating the Beat Domènec Library and the adjacent building, Cal Boter, the planned intervention will include actions aimed at reinforcing the stability of the entire structure:
- Reconstruction of the Party Wall: Tapia reinforced with compatible materials and modern solutions will be used to improve its mechanical resistance. The reconstruction will be linked to existing masonry piers and the floors that rested on it.
- Pathology Control: Actions will be taken to address moisture and cracks that could compromise the stability of the rest of the structure and have been the cause of the tapia's moisture.
Lessons Learned: The Importance of Arches in Historic Buildings
This incident serves as a reminder that the formation of discharge arches is essential in buildings with linear load-bearing walls, especially when working with materials like tapia. Their ability to redistribute forces not only protects the walls from overloads or material defects but also acts as a structural safeguard in emergency situations.
For architects, this case reinforces the need to integrate traditional knowledge with modern techniques, especially in rehabilitation projects. In addition to respecting the constructive history of the building, its stability and functionality for future generations must be ensured.
At the Beat Domènec Library and Cal Boter, the intervention we are carrying out reflects this balance between tradition and innovation, ensuring that the buildings continue to serve as a testament to the past and an inspiration for the future.
