Tahir Akgül

Thermal degradation modeling for single-shear nailed connections

ABSTRACT The load-carrying capacity of a timber structure is highly dependent on the strength of its connections. Very limited information exists on the thermal degradation, or the properties at elevated temperatures, of such connections. This insufficient information is one of the major impediments for modeling elevated temperature performance for wood-frame structures. The objective of this study was to characterize thermal degradation of yield load capacity of single-shear nailed connections between wood and oriented strand board (OSB) as a function of time and temperature. The mechanism of degradation was explained using first order kinetics. Using the principles of time–temperature superposition (TTS), predictive models for connection capacity degradation were developed. A total of 450 wood-to-OSB connections were tested laterally after exposure to nine different elevated temperature regimes. The degradation of yield load strength over time occurred at a constant linear rate. Temperature dependence of this rate was modeled using the Arrhenius activation energy theory. Using Arrhenius activation energy theory and principles of TTS, a master curve was developed to predict the performance of connections after exposure to a temperature of 150°C. The predictions matched well with independent experimental observations. The master curve developed using TTS provides predictive estimates of residual capacity in a connection as well as its failure times.

Investigation of Buckling Behavior of FRP-Concrete Hybrid Columns

The use of fiber reinforced plastic (FRP) composite materials in the construction industry increases with each passing day. In recent years, these materials are used as carrier material or reinforcement material in the structure. Glass fiber reinforced plastic (GFRP) profiles are among the most preferred FRP composite materials. GRFP profiles stand out with their high tensile strength, light weight and high corrosion performance. The hybrid use of these materials with classical construction materials offers new advantages. The buckling behavior of the hybrid material formed by placing concrete in plastic state into GFRP box profiles with high tensile strength was investigated in this study. The buckling performance of hybrid columns formed using GFRP profile, normal concrete or reactive powder concrete (RPC) was studied. To this end, normal concrete-GFRP profile and RPC-GFRP profile hybrid columns were produced and buckling testing was performed at different slenderness values. Charts were created after buckling experiments to examine differences in the behavior of the material. As a result of the examinations, the effect of RPC and column slenderness on the buckling performance hybrid columns was identified.

INVESTIGATION OF HEAT INSULATION PERFORMANCE OF DIFFERENT WALL VARIETIES USED IN BUILDINGS

In this study, the most preferred types of wall heat insulation performance are determined experimentally. For this purpose, with the actual construction features 1/3 of a reinforced concrete structure can be manufactured and column spans are built with six different wall element. These materials are extensively used in the production of housing; horizontal hollow brick, the vertical hollow brick, pumice, aerated concrete blocks, brick and sandwich wall. A heat source placed inside the model building, with the help of thermo couples fixed to the internal heat is provided. The building operated for 30 days with a heat source to provide heat balance and every wall surface of the thermal images were taken with the camera. The images and heat values are interpreted, heat efficiency of the wall varieties are defined. Consequently, the wall varietiess thermal conductivity resistance, thermal conductivity coefficient and the amount of heat loss have been identified.