# Cross-Laminated Timber: A Survey on Design Methods and Concepts in Practice

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## Abstract

**:**

## 1. Introduction

## 2. State of the Art

#### 2.1. Particularities of Cross Laminated Plates

#### 2.2. Current Cross Laminated Timber Regulation in Standards

## 3. Description of the Questionnaire

## 4. General Experience on Cross Laminated Timber Construction

#### 4.1. Background and Experience

#### 4.2. Cross Laminated Timber Knowledge

## 5. Design Methods for Cross Laminated Timber in Practise

#### 5.1. General

#### 5.2. Reference Literature

#### 5.3. Used Background Theories

#### 5.4. Used Tools and Design Verification

#### 5.5. Joints and Connections

## 6. Design Methods in Special Cases

#### 6.1. Complex Design Situations: Challenges, Problems and Improvements

#### 6.2. Seismic Design

## 7. Final Considerations

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**Example of a cross laminated timber panel [6].

**Figure 2.**Increase in the volume of cross laminated timber production according to Sandoli et al. [5].

**Figure 4.**Shear deformations between layers of a cross laminated timber plate cross-section according to Mestek et al. [13], where t are the applied shear forces, ${u}_{i}$ the resulting deformation of a transverse layer, and u the total deformation of the plate. Redrawn and adapted by the authors.

**Figure 5.**Failure modes of shear walls according to Danielsson et al. [14]. Redrawn and adapted by the authors.

**Figure 10.**Software used for cross laminated timber (CLT) design (

**left**), and satisfaction with available software solutions (

**right**). Legend: ${}^{\mathrm{a}}$ CLTdesigner, TimberTech, etc.; ${}^{\mathrm{b}}$ Binderholz (DC/Wallner-Mild), KLH Designer, StoraEnso Calculatis, etc.; ${}^{\mathrm{c}}$ Dlubal, SAP 2000, SOFiSTiK, etc; ${}^{\mathrm{d}}$ Abaqus, Ansys, etc.; ${}^{\mathrm{e}}$ MatLab, MS Excel, etc.

**Figure 11.**Verification methods. Legend: ${}^{\mathrm{a}}$ This includes the application of alternative finite element software and own software solutions i.e., Matlab, MS Excel, etc.

**Figure 13.**Challenging design situations for cross laminated timber (CLT): (

**a**) openings in walls, (

**b**) openings in floors, (

**c**) deep CLT beams (with openings), (

**d**) CLT beams (with openings), (

**e**) point supports and concentrated loads, (

**f**) cantilevers, (

**g**) asymmetrical lay-ups.

**Figure 14.**Other challenging situations. Given reasons: ${}^{\mathrm{a}}$ resistance and compartmentalization; ${}^{\mathrm{b}}$ member and global system; ${}^{\mathrm{c}}$ e.g., at connections, openings, etc.; ${}^{\mathrm{d}}$ e.g., ribbed plates, etc.

**Figure 16.**Reasons why CLT or hybrid (CLT-concrete) structures are not commonly used for high-rise buildings in seismically active regions.

**Figure 17.**Seismic design with cross laminated timber (CLT). Type of analysis used for seismic design (

**left**) and structural systems used in combination with CLT (

**right**).

**Figure 19.**Reasons why CLT or hybrid (CLT-concrete) structures are not commonly used for high-rise buildings in seismically active regions.

(a) Professional Sector | ||||||
---|---|---|---|---|---|---|

Design company | Construction company | Supplier/Manufacturer | Researcher at company | University/Research institute | Software developer | Other |

$47.4\%$ | $20.8\%$ | $4.0\%$ | $5.2\%$ | $18.5\%$ | $1.2\%$ | $2.9\%$ |

(b) Work Experience | ||||||

<3 years | 3 to 10 years | 11 to 20 years | >20 years | |||

$13.5\%$ | $34.0\%$ | $34.8\%$ | $17.7\%$ |

(a) Size based on the number of employees (single choice). | |||||
---|---|---|---|---|---|

<5 | 5 to 10 | 11 to 30 | >30 | ||

$19.2\%$ | $9.9\%$ | $17.7\%$ | $53.2\%$ | ||

(b) Percentage of timber structures (or research projects) in the volume order (single choice). | |||||

<10% | 10–40% | 41–70% | >70% | ||

$21.3\%$ | $23.4\%$ | $12.1\%$ | $43.3\%$ | ||

(c) Percentage of cross laminated timber structures (or research projects) in the order volume (single choice). | |||||

<10% | 10–40% | 41–70% | >70% | ||

$44.0\%$ | $27.0\%$ | $15.6\%$ | $13.5\%$ | ||

(d) Type of cross laminated timber buildings that are designed/built by the respondents (multiple choice). | |||||

Single/double family houses | Apartment buildings (1–3 storeys) | Multi-storey buildings (4+ storeys) | Industry buildings | Public buildings/ buildings for assemblies | Special constructions |

$70.2\%$ | $62.4\%$ | $60.3\%$ | $36.2\%$ | $59.6\%$ | $28.3\%$ |

(a) Are you familiar with the CLT construction? | ||||
---|---|---|---|---|

Not familiar | Very familiar | |||

$0.7\%$ | $1.4\%$ | $10.6\%$ | $34.0\%$ | $53.2\%$ |

(b) Are you confident that the current CLT design concepts are adequate? | ||||

Not at all | Yes | |||

$0\%$ | $9.2\%$ | $38.3\%$ | $39.0\%$ | $13.5\%$ |

**Table 4.**Assumptions used for structural modelling of material and plates in bending (multiple choice).

(a) Structural modelling of plates in bending | ||||
---|---|---|---|---|

Designer | Constructor | Researcher | Total | |

Modelling of plates in bending | ||||

$[63$ replies] | $[33$ replies] | $[26$ replies] | $[141$ replies] | |

$\gamma $-method | $\mathbf{57}.\mathbf{1}\%$ | $\mathbf{48}.\mathbf{5}\%$ | $\mathbf{50}.\mathbf{0}\%$ | $\mathbf{43}.\mathbf{3}\%$ |

Shear analogy | $39.7\%$ | $27.3\%$ | $42.3\%$ | $27.0\%$ |

Beam theory | $27.0\%$ | $39.4\%$ | $26.9\%$ | $20.6\%$ |

Theory of plates | $22.2\%$ | $42.4\%$ | $26.9\%$ | $22.7\%$ |

I do not know | $19.0\%$ | $15.2\%$ | $11.5\%$ | $27.0\%$ |

Other | $1.6\%$ | $0.0\%$ | $0.0\%$ | $5.0\%$ |

(b) Structural modelling of the material | ||||

Designer | Constructor | Researcher | Total | |

Modelling of the material | ||||

$[63$ replies] | $[33$ replies] | $[26$ replies] | $[141$ replies] | |

Homogeneous cross-section with effective properties | $\mathbf{49}.\mathbf{2}\%$ | $39.4\%$ | $\mathbf{57}.\mathbf{7}\%$ | $42.6\%$ |

Non-homogeneous cross-section with layer properties | $46.0\%$ | $\mathbf{51}.\mathbf{5}\%$ | $53.8\%$ | $\mathbf{43}.\mathbf{3}\%$ |

I do not know | $17.5\%$ | $18.2\%$ | $11.5\%$ | $22.0\%$ |

**Table 5.**Approach for cross laminated timber (CLT) verification (multiple choice). Legend: ${}^{\mathrm{a}}$ Binderholz (DC/Wallner-Mild), KLH Designer, StoraEnso Calculatis, etc.; ${}^{\mathrm{b}}$ CLTdesigner, TimberTech, etc.; ${}^{\mathrm{c}}$ Dlubal, SAP 2000, SOFiSTiK, etc.; ${}^{\mathrm{d}}$ Abaqus, Ansys, etc.; ${}^{\mathrm{e}}$ MatLab, MS Excel, etc.

Designer | Constructor | Researcher | Total | ||

Cross Laminated Timber (CLT) verification | |||||

$[63$ replies] | $[33$ replies] | $[26$ replies] | $[141$ replies] | ||

By hand calculation | $42.9\%$ | $51.5\%$ | $46.2\%$ | $40.4\%$ | |

Software provided by a CLT producer ${\phantom{\rule{0.166667em}{0ex}}}^{\mathrm{a}}$ | $50.8\%$ | $72.7\%$ | $46.2\%$ | $50.4\%$ | |

CLT oriented software ${\phantom{\rule{0.166667em}{0ex}}}^{\mathrm{b}}$ | $54.0\%$ | $69.7\%$ | $46.2\%$ | $50.4\%$ | |

Practice oriented FEM software ${\phantom{\rule{0.166667em}{0ex}}}^{\mathrm{c}}$ | $\mathbf{69}.\mathbf{8}\%$ | $\mathbf{72}.\mathbf{7}\%$ | $\mathbf{53}.\mathbf{8}\%$ | $\mathbf{61}.\mathbf{7}\%$ | |

Advanced FEM software ${\phantom{\rule{0.166667em}{0ex}}}^{\mathrm{d}}$ | $3.2\%$ | $6.1\%$ | $15.4\%$ | $8.5\%$ | |

Own solutions ${\phantom{\rule{0.166667em}{0ex}}}^{\mathrm{e}}$ | $42.9\%$ | $57.6\%$ | $46.2\%$ | $49.6\%$ |

(a) Applied connection stiffness | ||||
---|---|---|---|---|

Rigid | Spring | Hinge | None | |

Applied connection stiffness | ||||

CLT Wall ↔ CLT Wall | $29.1\%$ | $\mathbf{41}.\mathbf{1}\%$ | $22.7\%$ | $7.1\%$ |

CLT Floor ↔ CLT Floor | ||||

CLT Floor ↔ CLT Wall | $31.9\%$ | $\mathbf{46}.\mathbf{8}\%$ | $17.7\%$ | $3.5\%$ |

CLT Wall ↔ CLT Floor | ||||

CLT ↔ Concrete | $31.2\%$ | $\mathbf{41}.\mathbf{1}\%$ | $19.9\%$ | $7.8\%$ |

(b) Reference of the assumed stiffness of the connections | ||||

Designer | Constructor | Researcher | Total | |

Reference for connection stiffness | ||||

$[63$ replies] | $[33$ replies] | $[26$ replies] | $[141$ replies] | |

Documentation from CLT producer | $19.4\%$ | $21.3\%$ | $19.0\%$ | $23.4\%$ |

Documentation from fastener/connector producer | $\mathbf{32}.\mathbf{6}\%$ | $\mathbf{36}.\mathbf{1}\%$ | $\mathbf{35}.\mathbf{7}\%$ | $\mathbf{32}.\mathbf{3}\%$ |

Engineering judgement based on experience | $22.5\%$ | $21.3\%$ | $14.3\%$ | $21.0\%$ |

$\gamma $-method | $3.9\%$ | $1.6\%$ | $4.8\%$ | $3.6\%$ |

Relevant literature | $20.9\%$ | $16.4\%$ | $26.2\%$ | $18.5\%$ |

Other | $0.8\%$ | $3.3\%$ | $0\%$ | $1.2\%$ |

(a) Most challenging design issues | ||||
---|---|---|---|---|

Designer | Constructor | Researcher | Total | |

Challenging design issues | $[63$ replies] | $[33$ replies] | $[26$ replies] | $[141$ replies] |

Openings in walls | $20.6\%$ | $\mathbf{24}.\mathbf{2}\%$ | $\mathbf{26}.\mathbf{9}\%$ | $18.4\%$ |

Openings in floors | $15.0\%$ | $15.2\%$ | $11.5\%$ | $14.9\%$ |

Deep CLT beams | $6.3\%$ | $12.1\%$ | $7.7\%$ | $7.8\%$ |

Holes in CLT beams | $6.3\%$ | $9.1\%$ | $7.7\%$ | $9.9\%$ |

Point supports/concentrated loads | $\mathbf{28}.\mathbf{6}\%$ | $18.2\%$ | $11.5\%$ | $\mathbf{22}.\mathbf{7}\%$ |

Cantilevers | $4.8\%$ | $0.0\%$ | $23.1\%$ | $7.1\%$ |

Asymmetrical CLT lay-ups | $9.5\%$ | $9.1\%$ | $7.7\%$ | $9.9\%$ |

I have not encountered any of the above | $7.9\%$ | $12.1\%$ | $3.8\%$ | $9.2\%$ |

(b) Reasons for the difficulties on solving the complex design situations | ||||

Designer | Constructor | Researcher | Total | |

Missing/incomplete… | $[63$ replies] | $[33$ replies] | $[26$ replies] | $[141$ replies] |

Design concepts | $\mathbf{54}.\mathbf{0}\%$ | $\mathbf{42}.\mathbf{3}\%$ | $\mathbf{52}.\mathbf{2}\%$ | $\mathbf{46}.\mathbf{5}\%$ |

Material/design parameters | $16.0\%$ | $19.2\%$ | $17.4\%$ | $19.3\%$ |

Software implementation | $24.0\%$ | $23.1\%$ | $17.4\%$ | $21.9\%$ |

Geometric parameters | $0\%$ | $7.7\%$ | $0\%$ | $2.6\%$ |

Other | $6.0\%$ | $7.7\%$ | $13.0\%$ | $9.6\%$ |

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**MDPI and ACS Style**

Schenk, M.; Hübner, C.; Cabrero, J.M.
Cross-Laminated Timber: A Survey on Design Methods and Concepts in Practice. *CivilEng* **2022**, *3*, 610-629.
https://doi.org/10.3390/civileng3030036

**AMA Style**

Schenk M, Hübner C, Cabrero JM.
Cross-Laminated Timber: A Survey on Design Methods and Concepts in Practice. *CivilEng*. 2022; 3(3):610-629.
https://doi.org/10.3390/civileng3030036

**Chicago/Turabian Style**

Schenk, Martin, Clara Hübner, and José Manuel Cabrero.
2022. "Cross-Laminated Timber: A Survey on Design Methods and Concepts in Practice" *CivilEng* 3, no. 3: 610-629.
https://doi.org/10.3390/civileng3030036