Experimental investigation of glued laminated timber beam-to-beam connection

Abstract

Semi rigid mounting joints of glued laminated timber elements are connections that are fully assembled on construction site and capable to handle bending moments, axial and shear forces. The need for new type of semi rigid timber elements’ connection is obvious. The manufacturing possibilities of glued laminated timber elements’ are wide: straight element's length may extend up to 40 m or curved axis elements with dimensions of up to 10 meters in height, therefore, manufacturers, erectors and others face with transportation problems of non-standard, oversized elements. Semi-rigid mounting joints are used to solve this problem. In factory non-standard, oversized, glued, laminated timber elements are cut into standard transportation dimensions and fully mounted into integral element on construction site, using semi rigid mounting joints. In this article semi-rigid, glued, laminated timber elements’ joints which are used as beam to beam, beam to column and column to foundation connections are analysed. Also the main design principles of semi-rigid joints are discussed. The new type of semi rigid beam to beam connection is proposed and experimentally analysed. The experimentally and theoretically analysed connection is composed of welded steel details which are anchored into timber element. The main experiment is four point bending; the analysed connection is in the middle of the span. The beam's span is 3.20 m; the dimensions of the timber element's cross section are: width 200 mm; height 400 mm; mounting bolts are M16. Glued laminated timber strength class is GL24h. The tight contact between timber element and steel detail is created by anchoring steel detail's T shape part into timber element. The initial movement between timber element and steel detail is eliminated using fillers. Two types of fillers are used in these experiments: two component polyurethane and cement based filler with polymer fibres. Two joints with different fillers are tested in laboratory experiments. Bending bearing capacity and stiffness (displacements) of the joints’ are determined in laboratory. Experimental bearing capacities are compared with theoretical calculations according to European (EC5) and Lithuanian timber structures design codes. Conclusions and recommendations are presented for further experiments and computer simulations.

Santrauka

Straipsnyje analizuojami pusiau standūs montuojamieji klijuotosios medienos konstrukcijų mazgai, kurie naudojami elementams sujungti per ilgį, rėmų kampinėms jungtims tarp kolonos ir sijos bei jungtims tarp kolonos ir pamato. Aptariami pagrindiniai pusiau standžių montuojamųjų medinių konstrukcijų mazgų konstravimo principai. Pasiūlytas ir eksperimentiškai tirtas per ilgį sujungtų lenkiamųjų klijuotosios medienos sijos elementų mazgas. Mazgas įrengiamas naudojant plienines detales, suvirintas iš lakštinio plieno, kurios inkaruojamos medienos elementuose. Kontaktas tarp medienos ir metalo užtikrinamas ir pradinis mazgo slankumas panaikinamas užpildant tarpus tarp medienos ir metalo užpildu. Pasirinkti du skirtingo pagrindo (sudėties) užpildai: dviejų komponentų poliuretano ir cementinis, kurio sudėtyje yra polimerinių plaušų. Nustatytas cementinio užpildo lekiamasis ir gniuždomasis stipriai. Eksperimentinės jungčių laikomosios galios palyginamos su teoriniais skaičiavimais pagal Lietuvos ir Europos medinių konstrukcijų projektavimo normas. Pateikiamos išvados ir rekomendacijos tolesniems tyrimams.

Reikšminiai žodžiai: klijuotosios medienos elementų jungtys, elementų sujungimas per ilgį, sijos elementų tarpusavio jungtys, klijuotosios medienos rėmai

Keyword : glued laminated timber joints, beam-to-beam connections, glued laminated timber frames