Comparison of the hygrothermal performance of two light-framed timber structure buildings under different operation modes

Light-framed timber structure(LTS)buildings have been highly valued in recent years due to their low-carbon characteristics.However,the applicability of the building envelope is closely related to indoor and outdoor conditions.The hot summer and cold winter(HSCW)climate zone in China has high humidity and great temperature variation throughout the year,resulting in distinct outdoor environments in different seasons.The indoor environment is greatly affected by energy-consumption patterns and window-opening habits,which largely depend upon the regulation operations of occupants.All these interrelated factors lead to extremely complex boundary conditions on each side of the building envelope.Whether the structures of LTS buildings are applicable in this climate zone,therefore,needs to be carefully considered.In this study,two LTS buildings with different envelopes were established in Haining,China,situated in the HSCW climate zone,and selected as the study objects.Different operation modes were adopted to create a variety of indoor environments.Under each condition,the processes of heat and moisture transfer within the building envelopes and the indoor environment were monitored and compared.The comparison indicated that the building envelope with high moisture storage and insulation ability maintained a relatively stable indoor environment,especially when the environment changed abruptly.Conversely,if the outdoor environment was equable(e.g.,relative humidity within the range of 30%–60%)or intermittent energy consumption modes were adopted,the building envelope with a low thermal inertia index and weak moisture-buffering ability performed better because it enabled a faster response of the indoor environment to air conditioning.Moreover,a high risk of moisture accumulation between the thermal insulation layer and other materials with a large water vapour transfer resistance factor was also identified,suggesting a higher requirement for the vapour insulation of the envelopes of LTS buildings.

Influence of core stiffness on the behavior of tall timber buildings subjected to wind loads

This study analyzes the feasibility of the use of cross-laminated timber(CLT)as a load-bearing structural element in a 40-story building based on Chinese design requirements.The proposed design of the high-rise concrete-CLT building utilizes the core-outrigger system.Concrete is used for the central core and outriggers,and CLT is used for the rest of the structure of the building.Finite element models with different types of connections were developed using SAP2000 to analyze the lateral behavior of the building under wind action.The finite element models with rigid connections deduce the wind load distributions on individual structural elements,which determine the total number and the stiffness of fasteners of the CLT panels.Accordingly,spring links with equivalent stiffness that simulate the mechanical fasteners were employed in SAP2000.The results indicate that CLT increases the lateral flexibility of the building.A closed concrete core was substituted by two half cores to measure the requirement of the maximum lateral deflection.However,the acceleration at the building top still exceeded the limitation prescribed in Chinese Code JGJ 3-2010 owing to the lightweight of CLT and decreased stiffness of the hybrid building.To restrict this top acceleration within the limit,further approaches to increase the stiffness in the weak direction of the building are required.Methods such as the modification of the floor layout,increase in the thickness of walls,and addition of extra damping capacity should be considered and verified in the future.

Deflection test and modal analysis of lightweight timber floors

In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors,and strengthen the research on the coupling performance of the lightweight timber floors vibration characteristics and the building comfort,this article discusses the floor of a two-story prefabricated lightweight timber building demonstration house.In this paper,the floor structure of a two-story light-weight wooden house has been carried out on structural calculation modal and experimental modal,static uniform load and concentrated load deflection value testing.The evaluation of the deflection value of the floor structure,the mode shape,the coupling of the fundamental frequency mode parameters,and the vibration comfort were also studied.The results show that the fundamental frequency simulation value,one-way modal test value and two-way modal test value of the floor structure all meet the requirements of BS-6472(BS6472-1:2008).That is,the floor structure is not lower than 8 Hz design requirements,and meets the frequency of BS-6472(BS6472-1:2008).The weighted root mean square acceleration is lower than the requirement of 0.45 m/s^(2);the first three natural frequencies of the floor structure calculated by the finite element simulation are 16.413,31.847 and 48.921 Hz,and the fundamental frequency mode is the bending vibration in the length and width directions.The second order is the bending mode in the length direction,and the third order is the bending mode in the width direction.The fundamental frequency of the two-way modal test of the floor structure is the first-order bending mode in the X direction;and the second-order natural frequency is the second-order bending vibration shape in the X direction.when the uniform load is mainly the weight of floor own,the simulated maximum deflection value is 1.0658 mm;the simulation is performed according to the standard value of 0.566 kN/m for the uniform load of the floor design,and the simulation is the largest.The maximum deflection value of the simulated floor is 1.47383 mm at its midpoint,which meets the requirements of National Building Code of Canada-2015(NBCC).The maximum deflection limit of the light wood structure floor system is lower than 3 m and the maximum deflection limit is 2 mm;the six deflection value test lines simulated under a concentrated load of 1 kN all present a parabolic distribution and are symmetrical.The above results has engineering application value for promoting the research on the vibration characteristics of the fabricated lightweight timber floors structure and its optimization design.