Journal of Performance of Constructed Facilities

This study discusses the advantages and limitations of adopting time-based maintenance (TBM) and condition-based maintenance (CBM) strategies for natural stone claddings. In this study, an imperfect model for the system under stochastic deterioration is adopted, considering historical data about the degradation patterns of 203 natural stone claddings. This study introduces a probabilistic maintenance optimization method and a life cycle cost analysis framework to determine the optimal strategies for CBM and TBM strategies. The advantages of CBM over TBM are highlighted. CBM demonstrates the potential to achieve higher reliability levels while minimizing maintenance costs compared to TBM. CBM allows a more controlled and planned approach to maintenance, where interventions are strategically carried out based on the specific needs and condition of natural stone claddings. An optimized TBM policy is proposed, which offers a practical and reliable solution for managing the natural stone claddings. It strikes a balance between maintenance requirements, costs, and performance, ensuring the durability and performance of the claddings while minimizing unnecessary interventions.

The identification of damage to concrete bridge surfaces is of great significance to maintaining the durability and reliability of bridges. However, it is difficult to identify small areas of damage, especially in high-resolution images. To conduct damage identification research in a targeted manner, this paper proposes a method of multidamage identification in high-resolution images based on You Only Look Once version 5 (YOLOv5). In this paper, a data set labeled with four types of damage (crack, spallation, hole, and rebar) is used for training, validation, and testing. To ensure that the network adequately learns the damage features, the high-resolution images are cropped into subimages via the autoadaptive window cropping method (AWCM) proposed in this paper. The cropping method can crop images according to the label information and protect the damage features from destruction during the cropping process. To avoid overfitting, it is necessary to balance the volume of different types of damage. After balancing, the count for each category is as follows: crack (4,980), spallation (5,225), hole (5,211) and rebar (5,020). The balanced data set can be used to train the deep learning network and construct the multidamage identification model. After identification, the subimages, and the prediction boxes of damages in them are restored to their original high-resolution images. The results show that the mean average precision (mAP) of all classes is 94.2%, and the values for cracks, spallation, holes, and rebars are 86.9%, 98.1%, 92.3%, and 99.4%, respectively, which indicates that the proposed method outperforms the other three methods (inputting original images directly, the sliding window cropping method, and the random centroid cropping method).

Braced timber frames (BTFs) are an efficient lateral force resisting system that can effectively resist wind and earthquake loads. It is well-known that the performance of BTFs is strongly dependent on connection behavior, but clear design guidelines are not available for detailing ductile BTFs. Furthermore, conventional connections with steel fasteners can exhibit significant stiffness and strength degradation under earthquake loads and result in large residual deformations. There is a need for more resilient energy-dissipating connections for BTFs and other mass timber systems. This study investigates the behavior of dowel-type and bolted wood-steel-wood connections with superelastic nickel-titanium (NiTi) shape memory alloy (SMA) fasteners. Under bending, the SMA fasteners are able to effectively recover their original shape with negligible residual deformation, even after undergoing large deflections. The SMA connections tested in this research showed significant potential for self-centering. Post-test autopsies of the connection test specimens showed ductile deformation mechanisms and similar levels of wood crushing between the steel and SMA fasteners under cyclic loading. However, the connection displacement ductility ratios of 4.6 and 6.2 observed with SMA fasteners is not sufficient to meet the requirement for moderately ductile frames. Additional research is required to better understand and characterize the behavior of SMA connections at the component and connection levels.