Optimization of bonding parameters of laminated wood using a novel bio-based RPF adhesive

Adhesive is the key component and factor for the manufacture of glulam, affected both the properties and cost of glulam product. Bio-based resorcinol-phenol-formaldehyde (BRPF) resin was developed by partly replacing the expensive resorcinol and phenol with the cheap biomass derived pyrolysis oil. The press process parameters and the dosage of adhesive and corresponding curing agent were selected as the factors and extensively studied. BRPF resin was successfully used to bond the laminas to produce glulam, and the optimized process parameters for the cold-pressing adhesion of BRPF resin with pine wood were obtained as follows: the cold-pressing pressure 1.4 MPa, the cold-pressing time 9 h, the amount of adhesive coating 320 g/m2, and the proportion of curing agent (poly-formaldehyde) 17%. The mechanical performances of laminated wood bonding with BRPF resin under the optimal condition were further verified. It is believed that the results obtained here will promote the use of bio-based resin in the bonding of laminated wood, and then contribute to the green manufacturing of glulam with lower cost

Long-Term Performance of a Deep Excavation in Silty Clay in Xi’an—A Case Study

The long-term deformation of a 17.5 m deep excavation constructed with the bottom-up technique in silty clay in Xi’an was monitored in this study. The retaining wall was built with one or two rows of contiguous bored concrete piles and tie-back prestressing tendons. The monitoring of settlement and lateral deflection at the top of the retaining structure, and the settlement of the ground surface and of the adjacent building lasted for more than 4 years. After the final depth was reached, the excavation was surveyed for more than 3.1 years. It was observed that the deformation of the excavation increased with the increase in the excavation depth, and a significant increase in displacement was recorded after the excavation reached the final depth. The averaged time-dependent rates of the deflection of the retaining wall, and the settlement of the ground surface and of the adjacent building when the excavation remained partially unfilled were around 0.23–0.25 mm/month in this study. The time-dependent behavior of the excavation could lead to excessive deformation and cause severe safety risks to the retaining system. The recorded data, together with a comparison with cases reported in the open literature, are presented in this paper

Failure Modes and Mechanical Properties of Bracket Anchor Connections for Cross-Laminated-Timber

The paper presents some experimental data and phenomenon on bracket anchor connections for Cross-Laminated-Timber. The goal of this research is to provide a better understanding of the seismic performance of bracket connections subjected to seismic actions and how to choose and design bracket connections for Cross-Laminated-Timber structures. Test configuration and experimental setups are illustrated in details; cyclic displacement schedules of the connections in two directions are presented considering that CLT wall has horizontal sliding in the plane and uplift at the end in quasi-state tests. Different failure modes and force transmission mechanisms of different connections under the loading protocol were analysed. And important quantities for seismic design such as strength, and stiffness, equivalent yield load, peak load and ductility of the connections are evaluated and compared among different kinds of connections; an excellent connector is revealed in ductility and load capacity by test data analysis. In addition, some suggestions to choose and design bracket anchor connections are given

Study of the Mechanical Properties of Wood under Transverse Compression Using Monto Carlo Simulation-Based Stochastic FE Analysis

Wood is an anisotropic material, the mechanical properties of which are strongly influenced by its microstructure. In wood, grain compression strength and modulus are the weakest perpendicular to the grain compared to other grain directions. FE (finite element) models have been developed to investigate the mechanical properties of wood under transverse compression. However, almost all existing models were deterministic. Thus, the variations of geometry of the cellular structure were not considered, and the statistical characteristic of the mechanical property was not involved. This study aimed to develop an approach to investigate the compression property of wood in a statistical sense by considering the irregular geometry of wood cells. First, the mechanical properties of wood under radial perpendicular to grain compression was experimentally investigated, then the statistical characteristic of cell geometry was extracted from test data. Finally, the mechanical property of wood was investigated using the finite element method in combination with the Monte Carlo Simulation (MCS) techniques using randomly generated FE models. By parameter sensitivity analysis, it was found that the occurrence of the yield points was caused by the bending or buckling of the earlywood axial tracheid cell wall in the tangential direction. The MCS-based stochastic FE analysis was revealed as an interesting approach for assessing the micro-mechanical performance of wood and in assisting in understanding the mechanical behavior of wood based on its hierarchical structure

Optimization of bonding parameters of laminated wood using a novel bio-based RPF adhesive

Adhesive is the key component and factor for the manufacture of glulam, affected both the properties and cost of glulam product. Bio-based resorcinol-phenol-formaldehyde (BRPF) resin was developed by partly replacing the expensive resorcinol and phenol with the cheap biomass derived pyrolysis oil. The press process parameters and the dosage of adhesive and corresponding curing agent were selected as the factors and extensively studied. BRPF resin was successfully used to bond the laminas to produce glulam, and the optimized process parameters for the cold-pressing adhesion of BRPF resin with pine wood were obtained as follows: the cold-pressing pressure 1.4 MPa, the cold-pressing time 9 h, the amount of adhesive coating 320 g/m2, and the proportion of curing agent (poly-formaldehyde) 17%. The mechanical performances of laminated wood bonding with BRPF resin under the optimal condition were further verified. It is believed that the results obtained here will promote the use of bio-based resin in the bonding of laminated wood, and then contribute to the green manufacturing of glulam with lower cost

Study of the Mechanical Properties of Wood under Transverse Compression Using Monto Carlo Simulation-Based Stochastic FE Analysis

Wood is an anisotropic material, the mechanical properties of which are strongly influenced by its microstructure. In wood, grain compression strength and modulus are the weakest perpendicular to the grain compared to other grain directions. FE (finite element) models have been developed to investigate the mechanical properties of wood under transverse compression. However, almost all existing models were deterministic. Thus, the variations of geometry of the cellular structure were not considered, and the statistical characteristic of the mechanical property was not involved. This study aimed to develop an approach to investigate the compression property of wood in a statistical sense by considering the irregular geometry of wood cells. First, the mechanical properties of wood under radial perpendicular to grain compression was experimentally investigated, then the statistical characteristic of cell geometry was extracted from test data. Finally, the mechanical property of wood was investigated using the finite element method in combination with the Monte Carlo Simulation (MCS) techniques using randomly generated FE models. By parameter sensitivity analysis, it was found that the occurrence of the yield points was caused by the bending or buckling of the earlywood axial tracheid cell wall in the tangential direction. The MCS-based stochastic FE analysis was revealed as an interesting approach for assessing the micro-mechanical performance of wood and in assisting in understanding the mechanical behavior of wood based on its hierarchical structure

Enhancing the In-Plane Behavior of a Hybrid Timber Frame–Mud and Stone Infill Wall Using PP Band Mesh on One Side

Traditional village dwellings in China consisting of timber frames with mud and stone infill walls represent an important part of cultural heritage and civilization. Due to the lack of an effective link between the wood frame and the infill and the poor cohesiveness of clay, the masonry infill can collapse during an earthquake, whereas the wood frame suffers minimal damage. In this study, current retrofitting techniques for village buildings were investigated and discussed. A method using polypropylene (PP) band mesh and cement mortar to retrofit the timber frame with a mud and stone infill was proposed and the connection construction details were designed. In-plane static cyclic tests were conducted on two full-scale wood–stone hybrid walls reinforced on one side with different grid sizes of the PP band mesh. The failure behaviors of the reinforced and non-reinforced sides of the specimens were compared, and the failure mechanics and seismic capacity of the two specimens, i.e., the strength, stiffness, ductility, and energy dissipation, were investigated. The results were also compared with those of a previous frame with stone infill without pebbles and no reinforcement. The study indicated that the retrofitting method strengthened the integrity and lateral resistance of the hybrid structure and prevented the collapse of the stone infill of the reinforced surface in a plane earthquake. The grid size of the PP band mesh substantially affected the lateral performance of the reinforced specimens. The hybrid wall with the narrow PP band mesh grid (150 mm × 150 mm) had a higher lateral stiffness (79%) and lateral capacity (50%) than the wall with the wide grid (250 mm × 250 mm). However, the narrow PP band mesh resulted in a lower ductility of the wall than the wide PP band mesh. The involvement of pebbles in the stone infill led to collapses sooner and a weaker lateral resistance than in the structure without pebble infill

Seismic Resistance of Timber Frames with Mud and Stone Infill Walls in a Chinese Traditional Village Dwelling

Traditional Chinese wood residences consist of timber frames with masonry infill walls or other types of infill, representing valuable heritage. A field investigation of traditional village dwellings in northern China consisting of timber frames with mud and stone infill walls was conducted. Their construction characteristics are reported, and static cyclic tests were performed on two full-size wood-stone hybrid walls with different configurations (exterior transverse wall and internal transverse wall) and no openings (doors or windows). Their failure mechanics and seismic capacity, i.e., the strength, stiffness, ductility, and energy dissipation, were investigated. The results are compared with a previous experimental study of two full-size timber frames with the same traditional structure but no infill to determine the effect of the mud and stone infill on the lateral resistance. The experimental results indicate that the stone infill has a critical influence on the lateral performance of traditional village buildings, resulting in a high lateral stiffness, high strength (>20 kN), and a high ductility ratio (>10). An increase in the vertical load leads to an increase in the lateral resistance of the timber frame with infill walls, larger for the internal transverse wall than the external gable wall. The incompatibility of the deformation between the timber frame and stone infill is the main failure reason, resulting in falling stones and collapse with undamaged timber frames. Suggestions are provided for the protection and repair of traditional wood residences in northern China

Seismic Resistance of Timber Frames with Mud and Stone Infill Walls in a Chinese Traditional Village Dwelling

Traditional Chinese wood residences consist of timber frames with masonry infill walls or other types of infill, representing valuable heritage. A field investigation of traditional village dwellings in northern China consisting of timber frames with mud and stone infill walls was conducted. Their construction characteristics are reported, and static cyclic tests were performed on two full-size wood-stone hybrid walls with different configurations (exterior transverse wall and internal transverse wall) and no openings (doors or windows). Their failure mechanics and seismic capacity, i.e., the strength, stiffness, ductility, and energy dissipation, were investigated. The results are compared with a previous experimental study of two full-size timber frames with the same traditional structure but no infill to determine the effect of the mud and stone infill on the lateral resistance. The experimental results indicate that the stone infill has a critical influence on the lateral performance of traditional village buildings, resulting in a high lateral stiffness, high strength (>20 kN), and a high ductility ratio (>10). An increase in the vertical load leads to an increase in the lateral resistance of the timber frame with infill walls, larger for the internal transverse wall than the external gable wall. The incompatibility of the deformation between the timber frame and stone infill is the main failure reason, resulting in falling stones and collapse with undamaged timber frames. Suggestions are provided for the protection and repair of traditional wood residences in northern China

Experimental Investigations and Numerical Simulations of the Vibrational Performance of Wood Truss Joist Floors with Strongbacks

This paper provides an experimental study and computer modeling analysis of vibration performance of full-scale wood truss joist floors, related to the static deflection and vibration mode/frequency and single-person-induced vibration. The vibration behavior of full-scale truss joist floors was investigated and the influences of the strongbacks on the vibration behavior were assessed. The results showed that the simulated predictions agreed well with the measured results. Strongbacks do not significantly affect the fundamental frequency of the truss joist floors but influence the second and third modal frequencies. The use of strongback rows at mid-span effectively decreased the maximum deformation of point loading at floor center. The effect of adding strongbacks at one-third of each span on decreasing maximum deformation at the floor center was minimal. The case of walking parallel to the joist produced higher acceleration response at the floor center than that of walking perpendicular to the joist. The closer the placements of strongbacks were to the mid-span, the more significant reduction of the vibration at floor center was. Two strongback rows at mid-span performed the best effect on reduction of vibration response at floor center. However, the use of strongbacks had limits of reduction peak acceleration of the sheathing between the joists. The study provides a valuable guide for future vibration serviceability study and design optimization of wood truss joist floors