Connection stiffness identification of historic timber buildings using Temperature-based sensitivity analysis

Abstract

The beam-column connection, called 'Que Ti', is the key component of historic Tibetan timber buildings to transfer shear, compression and bending loads from one structural element to another. This kind of connections can reduce the internal forces and improve the structure's ability to resist earthquakes. Its structure is very complicated and there is little information about the behaviour of this kind of semi-rigid connections. In this paper, a temperature-based response sensitivity method is proposed to identify the connection stiffness of the 'Que-Ti' in typical historical Tibetan buildings from temperature and strain response measurements. The semi-rigid connection is modelled as two rotational springs and one compressive spring. The temperature is treated as a measureable input and the thermal loading on the structure can be determined from the temperature variation. The numerical results show the method is effective and reliable to identify both unknown boundary conditions and the connection stiffness of the structure accurately even with 10% noise in measurements. A long-term monitoring system has also been installed in a typical historical Tibetan building and the monitoring data are used to further verify the proposed method. The experimental results show that the identified stiffness by the proposed method are consistent with that by finite element model updating from ambient vibration measurements.

Condition assessment of heritage timber buildings in operational environments

“…Both sides of the connection are independent. The damage may be happened in one beam but the another one is good (Lyu et al, 2017). The errors in calculation results are shown in Figure 10.…”

“…With consideration of this arrangement, three linear springs are used to simulate the behaviour of a 'Que-Ti' in which two of them are rotational springs with stiffnesses K1 and K2 to simulate the behaviour of the rotating restraint on the beam, and the other one with stiffness K3 has vertical compressive stiffness to simulate the compression behaviour perpendicular to grain as shown in Figure 5. The three spring stiffness matrices are assumed linear and uncoupled (Lyu et al 2017).…”

“…The first and second checks were the mode shapes and frequencies of the structure. A vibration study of the corridor structure was conducted (Lyu et al 2017). The aim was to extract the first few fundamental modes from ambient vibration measurements.…”

“…The thermal load is a slow-varying load compared with other dynamic loads. Lyu and Yang (2017) developed a recursive least-squares method to extract the thermal load of a bridge structure from measured acceleration responses. Lyu et al (2017) identified beam-column connection stiffness from the field monitoring data based on temperature-based sensitivity analysis.…”

“…Lyu and Yang (2017) developed a recursive least-squares method to extract the thermal load of a bridge structure from measured acceleration responses. Lyu et al (2017) identified beam-column connection stiffness from the field monitoring data based on temperature-based sensitivity analysis. In this paper, a finite element model of a typical heritage Tibetan building is built from the site investigation and the existing documents.…”