Roberto Crocetti

• PhD
• Professor at KTH Royal Institute of Technology

Compared to steel plates, plywood plates are competitive in structural connections due to their low carbon footprint, high tolerance during assembly, relatively low cost, and less prefabrication demand (Kromoser et al. 2021). During the last few decades, plywood depicts its imprint as connections in timber structures such as truss connections, beam...

Birch plywood exhibits outstanding mechanical properties with regards to tensile, compressive, and shear behaviors, making this wood engineered product promising in timber connection applications. However, the edgewise bending strength and stiffness, which are often critical for the design of gusset plates, have not been investigated thoroughly. Mo...

Plywood made from birch has superior mechanical properties compared with that made from most softwoods, which makes it suitable for structural application. Several previous studies have addressed birch plywood’s structural usage and angle-dependent mechanical properties (Crocetti et al. 2021; Furuheim et al. 2021; Wang et al. 2021, 2022a; Kromoser...

This chapter introduces the history and advantages of long-span timber structures, along with typical structural form and systems. It discusses general aspects of analysis for long-span timber structures, as well as the influence of the span on the structural design of long-span timber structures in terms of structural stability, bracing, and joint...

There is an increasing demand for engineered wood products (EWPs) due to the flourish of modern timber structures during recent years. However, the durability-related issues are still unignorable limitations when applying timber to outdoor structures. Therefore, treatment measures are still needed to enhance the durability of timber. The acetylatio...

There is an increasing demand for engineered wood products in modern structures. Birch plywood is promising in structural applications, due to the combined advantages of its superior mechanical properties and the cross lamination configuration. However, the off-axis mechanical properties of birch plywood have not been thoroughly investigated. The a...

The objective of this article is to study the dynamic behaviour of a timber pedestrian bridge by performing in-situ tests at four different construction stages: 1) on only the timber structure 2) on the timber structure with the railings 3) on the timber structure with railings and an asphalt layer during warm conditions and 4) same as stage 3 but...

The outstanding mechanical properties of birch plywood make it promising to be applied for structural purposes. However, the poor durability of birch against biodeterioration limits its outdoor uses. Chemical modification, e.g., acetylation, is one of the potent ways to mitigate the durability issues. Embedment strength is one of the main parameter...

Timber-concrete composite systems are widely used in Europe, North America, and Australasia, primarily due to their good mechanical performance in terms of statics, dynamics, and seismic response. In addition, the concrete slab provides excellent protection to the timber, making such systems suitable for outdoor application. The seismic performance...

An innovative timber-steel hybrid system, composed of glulam beams reinforced by means of steel rods with shear keys as connectors, was proposed to improve glulam structural performance in terms of strength, stiffness, and ductility. This hybrid system can be used for both reinforcing prefabricated timber members and retrofitting existing timber me...

The acetylation process involves chemical reaction between acetic anhydride and wood, which results in esterification of accessible hydroxyl groups in the cell wall, with formation of the by-product acetic acid. Acetylation of wood has been widely studied during the past decades, and several experimental studies have proven it to be effective in re...

The presented project aims to develop prototypes for building connections inspired by the furniture and interior industry and explore them with representatives from the timber construction industry. The long-term vision is that actors from furniture and building industry together develop a smart system for assembly of building elements, which provi...

This paper deals with experimental and numerical dynamic analyses of two timber footbridges. Both bridges have a span of 35 m and consist of a timber deck supported by two timber arches. The main purpose is to investigate if the dynamic properties of the bridges are season dependent. To this end, experimental tests are performed during a cold day i...

There is an increasing interest in large-dimensional timber structural elements within the construction sector in order to fulfil the combined demand of sustainability, open spaces and architectural flexibility. Current timber technology allows for efficient production of long-size beams, but many problems are related to their overall high costs du...

In recent years, large-dimensional structural timber elements are highly demanded for the construction of high-rise timber buildings as well as large-span structures. However, long-span wooden products are not easy to handle during transportation and erection phases, making them particularly expensive. To meet this challenge, an innovative timber-s...

Wind-induced dynamic excitation is becoming a governing design action determining size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway – i.e. vibration serviceability failure. Although some TTBs have been instrumented and...

h i g h l i g h t s Monotonic tensile tests of hybrid dowel and bonding steel plate joints. Experimental evaluation on ultimate load carrying capacity and deformation of the joints. Numerical analysis of shear stress distribution and mechanical behaviour of the innovative hybrid joints. a b s t r a c t This paper summarizes the experimental and num...

The long-term performance of bonding steel-plate joints in controlled environmental conditions in this work. The bonding steel-plate joint consists of a steel plate with a vulcanized rubber layer and six wood screws. The vulcanized rubber layer is intended to improve the ductility of bonding steel-plate joints. Six pull-pull specimens were tested i...

An experimental study on the duration of load effects in a glued shear plate dowel joint was conducted. The joint design features a single large diameter dowel for load transfers between members, via external steel plates, which are bonded to the timber with a low stiffness bond line. Due to the low bond line stiffness, the timber element is subjec...

The aim of the paper is to gain data on the mechanical behaviour of CLT-concrete composite floors and subsequently to check if commonly adopted analysis methods are suitable for this particular type of structure. The studies are conducted through laboratory tests, analytical models and numerical modelling. In the shear tests, the notched connection...

The design of slender structures is often associated with a number of assumptions made by engineers in checking on the stability of the structure. Not seldom, these assumptions are rather uncertain. In the present paper the effects of the stiffness of different members on the bracing stiffness of timber structures is studied. Both full-scale labora...

The arch is a very efficient load bearing structure, especially when its shape is affine to the funicular of forces. However, if live loads are predominant as compared to permanent uniformly distributed gravity loads, the arch will be subjected to substantial bending moments, thus losing a great part of its structural efficiency. In traditional arc...

The present study investigates the significance of potential slip in the bracings of simply supported slender timber members. Three bracing configurations are considered. The first case is that of a timber beam braced at one point at mid-span, the second one braced at two points and the third one braced at three points. Possible slip in the bracing...

The TRE3 research project focuses on the development of a new and innovative timber frame wall modulus for emergency housing facilities. The wall modulus, in this paper referred to as Hybrid Timber Frame (HTF) wall system, is an evolution of the traditional Light-Frame Timber (LFT) structural systems and combines the advantages and some peculiar as...

Many slender roof structures have collapsed due to snow loading and instability. Although accurate stability calculations can be performed using theoretical models, these calculations may not always reflect the behaviour of real structures as a result of the uncertainties relating to e.g. loading, material behaviour, geometry, initial imperfections...

The load capacity of long adhesive lap joints is often governed by stress concentrations at the lap ends. This paper investigates a method to minimize these stress concentrations by using a bond line with low shear stiffness and sufficient strength, here denoted as a resilient bond line. The resilient bond line is intended to increase the load carr...

Mechanical behavior of the shear connections has a significant influence on both the load-carrying capacity and the bending stiffness of timber-concrete composite (TCC) beams. All the studies reported so far have concentrated on the performance of TCC connections in mature concrete. The performance of shear connections for TCC beams at early concre...

Uneven exposure to e.g. solar radiation can cause temperature differences between various structural parts of a bridge, which leads to tensile stresses if the parts cannot move freely. In this study, thermal simulations and stress calculations on a model of a portal frame bridge are performed with the aim of evaluating the temperature difference be...

A timber-concrete composite structure (TCC) is economically and environmentally friendly. One of the key design points of this kind of structure is to ensure the reliability of the shear connectors. The objective of this paper is to study the mechanical property of stud-groove-type connectors and to provide shear capacity equations for stud-groove...

In the design of concrete bridges an important aspect is limiting crack widths, since large cracks can lead to e.g. corrosion and affect the bridge functionality. Restraint forces caused by thermal loads and shrinkage will likely constitute a large part of the total forces acting on the bridge in crack width design. In this paper, restraint stresse...

Finding new efficient connectors or improving existing ones are important issues in timber construction. This research investigates an innovative large-diameter dowel-type connection by using a finite elements model calibrated with experimental results. This connection is made of a large-diameter single dowel reinforced by means of a steel plate wi...

In the past, structural engineers have had to base their design on simplified methods such as hand calculations, rules of thumbs, experience and engineering intuition. Predominantly, engineers worked with safe sided assumptions and design conservatism as a way to compensate for the uncertainties involved. In more recent decades, the trend has been...

Slight bracing of steel bridges to control end warping of the compression flanges near the end supports can be very effective in enhancing the load-carrying capacity of the main girders that are involved. Relatively little information is available, however, regarding the stiffness and strength requirements of end-warping bracings. The results of se...

Uneven exposure to e.g. solar radiation can cause temperature differences between various structural parts of a bridge, which leads to tensile stresses if the parts cannot move freely. In this study, thermal simulations and stress calculations on a model of a portal frame bridge are performed with the aim of evaluating the temperature difference be...

The key point of design for timber-concrete composite structure is to ensure the reliability of shear connectors. This study examined the mechanical properties of bolt-type connectors in timber-concrete composite structures theoretically and experimentally. The theoretical study was based on the Johansen yield theory (European Yield Model). Push-ou...

The competitiveness of timber as structural material in large structures is often governed by the cost of structural joints. Tests indicate that the new joint concept presented herein using glued wood-to-steel plate joints can possibly reduce the cost by matching joint strength to member strength. The design is inspired by two previously proposed d...

Finite-element programs can be used for designing columns and their bracing systems. It is well known, however, that the output obtained from such programs is highly dependent upon the input (such as imperfections and stiffness properties). In the present study, the effects of imperfections on the predicted strength and stiffness requirements of st...

This paper deals with theoretical and experimental investigations of nailed steel plate connections. For the experimental part, a total of 43 laboratory tests on connections loaded in tension parallel to the grain are reported. The paper deals also with finite element analysis of the connection, presenting a study on the 3D stress distributions wit...

Slight bracing of steel bridges to control end warping of the compression flanges near the end supports can be very effective in enhancing the load-carrying capacity of the main girders that are involved. Relatively little information is available, however, regarding the stiffness and strength requirements of end-warping bracings. The results of se...

This paper deals with theoretical and experimental investigations of nailed steel plate connections. For the experimental part, a total of 99 laboratory tests have been carried out in order to study failure mechanism and shear capacity of nailed steel plate connections. The testing programme comprised two nail lengths, two steel plate thicknesses a...

imber is a structural material which has excellent strength and stiffness properties. As an example, it can be mentioned that the specific strength and the specific stiffness of spruce for tension and compression parallel to the grain – i.e. these mechanical properties divided by the material density – are superior to that of common structural stee...

Steel girders require stability controls for different construction stages before the lateral-torsional support from the concrete deck occurs. The load-carrying capacity of bridge girders and bracing forces generated in their bracings are sensitive greatly to the girders'¬ initial imperfections in terms of both the magnitude and distribution along...

Stress-laminated-timber (SLT) bridge decks are a valid alternative to conventional short- and medium-span bridges in terms of cost and performance. SLT decks are made from a number of planks or glulam beams positioned side by side and stressed together using high-strength steel bars. A concentrated load can therefore be distributed from the loaded...

The presented investigation concerns the study of novel types of timber-concrete composite floors, manufactured with “dry connections” (Crocetti et al. In: 11th WCTE, Riva del Garda: international conference proceeding of 11th WCTE, Riva del Garda, 2010; In: RILEM 2013: Materials and Joints in Timber Structures—Recent Advancement of Technology Stut...

Förord Avsikten med Limträhandbok Del 2 är att hjälpa konstruktören att dimensionera limträkonstruktioner. I synnerhet betonas förståelsen av: • Bakgrunden för dimensionering av konstruktionssystem utförda med limträ, särskilt konstruktioner med lång spännvidd. • Bakgrunden för dimensionering av förband i konstruktionssystem utförda med limträ. Den...

Förord Avsikten med Limträhandbok Del 3 är att hjälpa konstruktören att dimensionera limträkonstruktioner. Boken är ett komplement till Limträhandbok Del 2. Dimensionering av limträkonstruktioner med stor spännvidd och därtill hörande förband har prioriterats. Förstärkning av limträkonstruktioners svaga zoner har även behandlats. Två delar ingår: •...

Timber is a structural material which has excellent strength and stiffness properties. As an example, it can be mentioned that the specific strength and the specific stiffness of spruce for tension and compression parallel to the grain – i.e. these mechanical properties divided by the material density – are superior to that of common structural ste...

Large spans structures should ideally be designed so that they work primarily in tension and/or compression. In fact, minimizing bending moments leads in general to an optimum utilisation of the structure, regardless what material is chosen. This often results in slender and elegant shapes. Timber is a structural material which has excellent streng...

Relatively slight bracing of steel girders can significantly reduce the risk of buckling failures before the composite action between steel and concrete occurs. This paper aims at both experimentally and numerically, studying the torsional bracing performance of a typical type of scaffoldings that are commonly used in bridge construction. Minor imp...

This paper describes theoretical and experimental work undertaken to obtain a structural model for assessment of historical Latin-American vertically laminated planked timber arches, as built by the Spanish, mainly in the seventeenth and eighteenth centuries. Many such arches still stand, and represent an important historical heritage. Following in...

This paper describes theoretical and experimental work undertaken to obtain a structural model for assessment of historical Latin-American vertically laminated planked timber arches, as built by the Spanish, mainly in the seventeenth and eighteenth centuries. Many such arches still stand, and represent an important historical heritage. Following in...

In the bridge sector, lateral bracings can be provided e.g. in the form of metal decks or horizontal truss bracings. Those bracings are more efficient at the regions of maximum lateral shear deformations generated from destabilizing forces of compression flanges e.g. near to the twisting supports. A model is presented in this paper, which relates t...

This paper summarizes an experimental investigation on several innovative reinforcing techniques for the “Single Large Diameter Dowel Connection”, SLDDC in timber truss structures. Besides lateral reinforcing or prestressing, also steel plates glued on two sides of the glulam specimens were used as reinforcing measure. To study the efficiency of th...

This study relates to the development of innovative composite structures, comprising timber beams and prefabricated concrete slabs, with high prefabrication level, high performance and good durability. For such a purpose completely dry shear connection systems were investigated. Moreover, innovative and very efficient materials, such as fibre reinf...

This paper presents the results of an investigation conducted on a number of practicing structural engineers. The investigation was designed as a round-robin investigation were 16 engineers performed two early stage structural engineering tasks; the first a load take-down calculation for a five-storey concrete building, and the second the conceptua...

A novel type of timber-concrete composite floor, consisting of longitudinal glulam beams with a fibre reinforced concrete (FRC) slab on the top is proposed. In order to check some relevant mechanical properties of such a floor, full-scale laboratory tests along with numerical analyses were carried out. The shear connector system used in the investi...

Stress-laminated timber (SLT) bridge decks are generally designed using either linear hand calculation methods or linear finite-element models. Several studies have shown, however, that the behavior of SLT decks is nonlinear when loaded until failure. In this paper, several linear design methods are compared with one another and with an ultimate lo...

The required moment of inertia for steel plate girders is commonly provided by using relatively slender webs to achieve high strength-to-weight ratio. A large part of the shear capacity of such plate girders depends on the post-buckling reserve strength of the web panels due to the diagonal tension field mechanism. The effectiveness of the tension...

The required moment of inertia for steel plate girders is commonly provided by using relatively slender webs to achieve high strength-to-weight ratio. A large part of the shear capacity of such plate girders depends on the post-buckling reserve strength of the web panels due to the diagonal tension field mechanism. The effectiveness of the tension...

Trapezoidal cross sections are often used as main longitudinal load-bearing systems in steel-concrete composite bridges. A critical design stage for these girders occurs during casting of the bridge deck, when the non-composite steel section must support the entire construction load, including the wet concrete. A research work was undertaken to stu...

A general assumption reported in the literature is that the structural response of a stress-laminated-timber (SLT) bridge deck is linear until failure. However, few studies of ultimate-load tests (ULTs) on timber bridges have been reported. A full-scale test of a SLT deck (span, 4.9 m; thickness, 270 mm) was performed to obtain the deformations at...

In this paper, research on timber bridges both in the past in Scandinavia and on-going in Sweden is summarised. The on-going, more recent research at Chalmers University of Technology focuses on improving our understanding of the mechanical behaviour of stress-laminated-timber (SLT) decks loaded until failure. The experimental results from three fu...

During January and March 2010 a large number of roofs collapsed in Sweden due to heavy snowfall. The temperature was below zero and the wind came from the north and the east during the whole period. It was mainly steel and timber structures that failed. SP has created a database with information about 180 collapsed or seriously damaged buildings. T...

The limiting factors when it comes to design of timber structures are often stiffness properties of timber products. The stiffness requirements in serviceability limit state, both short-term and longterm deformation especially in horizontal members, is a factor that often makes it necessary to increase the dimensions of the member. Both the results...

Expansion joints in medium-size and long bridges should be regarded as important bridge components.There is a trend to minimize the number of joints, and design each joint to permit large movements. It is therefore important to develop suitable joint types that function smoothly for such large movements during a long time without damages or malfunc...

Retrofit of bridge expansion joints correspond to a relatively large part of the total maintenance cost of medium-length and large bridges. In the future, it is therefore important to design suitable joint types that function smoothly for such large movements during a long time without damages or malfunctioning. A widely used, modern joint type for...

Several premature fatigue failures of modular bridge expansion joints have occurred in Europe and the United States. The principal causes of such failures have been poor detailing (for instance, choice of fillet welds instead of full-penetration welds) and the tendency to reduce production costs by adopting larger beam spans. A critical analysis of...

The results of a series of fatigue tests on four full-scale slender plate-girders with medium to large panel aspect ratios (α=1.5 and 3) subjected to repeated combined action of bending and shear, are presented herein. The plate girders (span: 7.5 m, depth: 1200 mm, web thickness: 5 mm) were tested under constant amplitude fatigue loading up to fai...

This thesis concerns three specific fatigue topics related to steel members in bridges, namely: (1) Modular Bridge Expansion Joints (MBEJs). Several premature fatigue failures of MBEJs have occurred in Europe and USA during the past decades. The principal cause of such failures has been an insufficient knowledge of the magnitude of the acting force...

Glulam beams made of Norway spruce are stressed together with high strength steel bars creating a Stress laminated timber deck (SLTD). Deflections and stresses can be estimated with both finite element models based on orthotropic plate theory as well as with simplified hand calculation methods based simple beam theory. If SLTDs are loaded until fai...

The limiting factor when it comes to design timber structures is often the stiffness properties of timber products. The stiffness requirements in serviceability limit state, both short-term and final deformation especially in horizontal members, is a factor that often makes it necessary to increase the dimensions of the member. This cause increased...