Mustafa Özakça

• Ph.D --- Prof.Dr
• Head of Faculty at Gaziantep University

Reinforced concrete two-way slabs are important elements in the construction field, and their impact response under drop-weight impact is a complex mechanical issue that can cause the collapse of heavy structures. Previous research has documented the analysis of conventional steel-reinforced concrete slabs under impact loads. However, the investiga...

Concrete is a brittle material when subjected to design and accidental impact loads, which are expected along the life span of the structure. To improve the impact performance of concrete, steel fibers are used as short discrete material reinforcing elements. Among the available impact test, the ACI 544-2R repeated impact test is considered as the...

Despite that concrete is a fire-resisting construction material, its microstructure suffers significant chemical and physical changes when subjected to temperatures higher than 400 oC. Therefore, the combined effect of unexpected impacts and fire can lead to the collapse of the structure. To evaluate this combined effect, an experimental program wa...

Basalt Fiber Reinforced Polymer (BFRP) is an environment friendly strengthening material that can be used in several engineering applications. In this research, an experimental program was directed to investigate the BFRP strengthening adequacy of reinforced concrete beams. Eight simple-span beams were tested under the four-point bending test and w...

Aiming to introduce a simplified flexible design model for thermal actions in concrete bridge superstructures, experimental and finite element works were carried out in this study. From an experimental concrete box-girder segment, concrete temperature, solar radiation, air temperature and wind speed records for a complete one-year cycle were record...

The shear connector is one of the main parts in composite steel-concrete structures that resist horizontal shear and vertical uplift forces. One of the common connector types is the perfobond rib, which is mainly used in composing steel girders in bridges. The load-slip behavior has a significant effect on the composed section. In the current work,...

The shear connector is one of the main parts in composite steel-concrete structures that resist horizontal shear and vertical uplift forces. One of the common connector types is the perfobond rib, which is mainly used in composing steel girders in bridges. The load-slip behavior has a significant effect on the composed section. In the current work,...

Despite the fact that the mechanical properties of Engineered Cementitious Composites (ECC) after high-temperature exposure are well investigated in the literature, the repeated impact response of ECC is not yet explored. Aiming to evaluate the residual impact response of ECC subjected to sub-high temperatures under repeated drop weight blows, the...

Many countries used the precast prestress hollow slabs due to their easy installation and reduced construction time and high-quality control. In recent years raised concerns that ACI318 code provisions may overestimate the web-shear capacity of thick precast prestressed hollow slab (PHCS) members exceeding 315 mm in member depth (h) as a result, th...

The repeated impact performance of engineered cementitious composites (ECC) is not well explored yet, especially after exposure to severe conditions like accidental fires. An experimental research was conducted to evaluate the degradation of strength and repeated impact capacity of ECC reinforced with Polypropylene fibers after high temperature exp...

A full-scale 3D thermo-mechanical Finite Element (FE) model was conducted in this research to investigate the effect of open-field thermal loads on the structural response of box-girder bridges. A box-girder bridge with a span of 50 m was analyzed for temperature, radiation and displacement fields using COMSOL Multiphysics. To verify the FE model,...

Portland cement concrete is known to have good fire resistance; however, its strength would be degraded after exposure to the temperatures of fire. Repeated low-velocity impacts are a type of probable accidental load in many types of structures. Although there is a rich body of literature on the residual mechanical properties of concrete after high...

Atmospheric thermal loads are considered as one of the effective loads on bridge structures. The thermal actions in bridge superstructures are considered in most of the recent bridge design specifications. In this study, a concrete girder segment was cast in place in an open field to simulate the actual atmospheric exposure case of bridge girders....

Twelve ECC beams with three different fiber types, along with four normal concrete beams, were tested in this study to evaluate the influence of cross-sectional hollowing on their flexural performance. The fiber types used were nylon monofilament (NM), low-cost untreated polyvinyl alcohol (PVA), and polypropylene (PP). Three different square hole s...

Laying of service pipes such as sewage pipes, electricity pipes, and sometimes water pipes ducts and others had presented some problems especially if it gathered in one place. One of the best solutions to minimize the problems and solve the piping and other services is using longitudinal and transverse opening in beams (BLTO), especially when high...

This paper presents the experimental results of a full-scale concrete box-girder segment subjected to ambient thermal loads. The experimental segment was instrumented with 62 thermocouples to measure the concrete temperatures in different locations and a weather station to measure air temperature, wind speed, and solar radiation. The records from t...

The trend and behavior of Composite Box Girder Bridge (CBGB) are distinctly affected by the surrounding combination environment actions due to these constructions are erected in open environments. From this consideration, this research deals with the effect of the bridge's longitudinal axis, the geometrical configuration of CBGB and the thickness o...

In this work, 14 reinforced concrete solid and hollow beams were tested under four-point bending test to evaluate the flexural behavior of hollow concrete beams. The experimental program focused on two main variables which are the size reduction percentage and the inclusion of steel fiber. In addition, the longitudinal reinforcement ratio and the p...

This paper investigates the flexural behavior, ultimate load carrying capacity, deflection, and cracking for High-Strength Concrete (HSC) and Normal-Strength Concrete (NSC) one way solid slab. For this, reinforced concrete slabs with rectangular in cross-section and nominally 3500 mm long, 600 mm width, and 150 mm thickness with a clear span (dista...

This research deals with the thermal and thermo-structural behavior of concrete-steel composite box-girder bridge under the amalgamation of environmental thermal loads: global solar radiation, ambient air temperature, and wind speed. To achieve this goal, the experimental composite box-girder bridge segment with a full-scale cross-section erected i...

Basalt fiber-reinforced polymer (BFRP) is adopted widely in recent years in many countries to rehabilitate or strengthen structural elements such as reinforced concrete (RC) beams because it is cheap and it has stellar mechanical performance. By activating the finite element (FE) simulation, the present research submits an extensive study on the st...

Engineered cementitious composite (ECC) refers to the group of cementitious mixtures possessing the strain-hardening and crack control abilities. In this research, the mechanical performance of ECC beams will be investigated with respect to the effect of aggregate size and amount, by employing nonlinear finite element method. The proposed models wo...

In this study, an experimental work was directed toward comparing the flexural behavior of solid and hollow steel fiber-reinforced concrete beams. For this purpose, eight square cross-sectional beam specimens, four solid and four hollow, were prepared. One concrete mixture with four different steel fiber contents of 0, 0.5, 1.0, and 1.5% were used....

This experimental study presents the effect of nano-silica and steel fiber on the transport properties and compressive strength of alkali-activated slag/fly ash concrete incorporated cold-bonded fly ash aggregate. In order to reduce energy consumption and provide environmental impact, the cold-bonded process was used to manufacture cold-bonded fly...

stiffener that effect on the strutural behavior on liquid storage tank , there was used different steel shape profile and the tank seperate with courses that we have 1-6 courses , we are calculated the placed stiifener on the tank wall , thus we are using software finite element program that is called ANSYS then it is analyzed fundamental frequency...

It became well known that steel fibers could significantly improve the mechanical properties of concrete and the ductility of flat plat-column assembly at ambient conditions. The investigation of the contribution of the steel fiber and the high strength concrete under high temperature conditions on the structural behavior of flat plates is still in...

Engineering Cementitious Composite (ECC) materials with Polyvinyl Alcohol (PVA) fibers are employed to investigate the effect of the ductile matrix on the behavior of flat plat-column connection. Totally four slabs are casted and tested, three of PVA-ECC slabs are compared to control slab of normal concrete. The thickness of the three slabs is vary...

The behavior of reinforced concrete hollow simply support beams under four-points flexural test load are discussed in this study, to investigate the ultimate load capacity of a hollow beams compared to a solid and hollow plain beams. Five hollow beams with square cavity (80 × 80 mm) along a beam are constructed and tested in this study. All beams h...

Concrete is characterized by its brittleness strength criterion; therefore many researchers had been conducted in order to enhancing this criterion. Many types of fibers are investigated, the key point of the judgment on the suitability of the fibers for such a concrete is basis on member loading type, type of the fiber, the proportion of the concr...

Behaviors of the flat plate-column assembly of four reinforced slabs are investigated. Polypropylene synthetic fibers are added to the dense concrete that includes 63% of fine aggregate, the dimensions of the tested square slabs were 500 × 500 × 60 mm, reinforced by constant reinforcement ratio of 0.9%. The main parameter was the polypropylene volu...

The flat plate-column connection is a critical region in concrete structures because of the possible punching shear failure due to brittleness, which is aggravated in the presence of fire. Many studies have been carried out on flat plate-column connections in ambient conditions. However, only a handful of experimental works have examined this regio...

This paper presents the numerical study of behavior of the sandwich panels, which consists of glass fiber reinforced polymer skins, and a polyurethane foam core and the sandwich panels, which contains glass fiber reinforced polymer U profile by using the ANSYS APDL program. The behavior of these panels was examined under 4 point load tests and the...

The impact of non-uniform temperature distributions in concrete, steel, and composite girders due to the environment thermal loads has been recognized by former structural health monitoring studies and bridge design codes. Although extensive efforts have been directed to study these effects, more researches are required to study the temperature dis...

Resistance of steel fiber reinforce slabs to punching are extensively investigated, which showed that the steel fibers enhanced the ultimate slab resistance made of normal strength concrete. Current work involved the testing of three small high strength slabs. The slabs were 500 mm square, and of 60 mm thickness, reinforced by two steel fiber dosag...

Engineering Cementitious Composite (ECC) materials with PolyVinyl Alcohol (PVA) fibers are employed to investigate the effect of the ductile matrix on the behavior of flat plate-column connection. Totally four slabs are cast and tested, three of PVA-ECC slabs are compared to control slab of normal concrete. The thickness of the slabs used was varia...

This paper deals with the effectiveness of various bracing systems used in lattice towers. Seven types of bracings used in 4-legged square based self-supporting power transmission and telecommunication towers and four types of bracings used in 3-leg triangular based self-supporting telecommunication towers are analyzed. The investigated bracing sys...

Resistance of steel fiber reinforced slabs to punching is extensively investigated, which showed that the steel fibers enhanced the ultimate slab resistance made of normal strength concrete. Current work involved the testing of three small high strength concrete slabs. The slabs were of 500 mm square sides, and of 60 mm thickness. The slabs were re...

Enhanced tensile properties of fiber reinforced concrete make it suitable for strengthening of reinforced concrete elements due to their superior corrosion resistance and high tensile strength properties. Recently, the use of fibers as strengthening material has increased motivating the development of numerical tools for the design of this type of...

Engineered Cementitious Composite (ECC) is a special class of the new generation of high performance fiber reinforced cementitious composites (HPFRCC) featuring high ductility with relatively low fiber content. In this research, the mechanical performance of ECC beams will be investigated with respect to the effect of slag and aggregate size and am...

Main aim of this paper is to apply a numerical analysis of reinforced concrete hollow beam using three dimensional (3D) finite element model under monotonic loading, for this purpose, a well-known finite element traditional software ANSYS has been used. Many variables were studied in the model such as the ratio of hollow area to effective section a...

Engineered cementitious composite (ECC) refers to the group of cementitious mixtures possessing the strain-hardening and crack control abilities. In this research, the mechanical performance of ECC beams will be investigated with respect to the effect of aggregate size and amount, by employing nonlinear finite element method. The validity of the mo...

Engineered cementitious composite (ECC) refers to the group of cementitious mixtures possessing the strain-hardening and crack control abilities. The mechanical performance of ECC beams will be investigated with respect to the effect of aggregate size and amount, by using nonlinear finite element method and nonlinear parametric study. The comparati...

Engineered cementitious composite (ECC) refers to the group of cementitious mixtures possessing the strain-hardening and crack control abilities. In this research, the mechanical performance of ECC beams will be investigated with respect to the effect of aggregate size and amount, by employing nonlinear finite element method. The proposed models wo...

Fiber reinforced polymers materials have a wide use in a variety of applications, which are produced with a range of different stiffness and strength characteristics. However, these materials share identical orthotropic properties and ductility. In contrast, the ordinary concrete is isotropic and brittle material. This review study provides an effi...

Fiber reinforced polymers materials have a wide use in a variety of applications, which are produced with a range of different stiffness and strength characteristics. However, these materials share identical orthotropic properties and ductility. In contrast, the ordinary concrete is isotropic and brittle material. This review study provides an effi...

İNŞAAT MÜHENDİSLİĞİNDE HAREKETLİ MEMBRAN YAPILAR İÇİN TASARIM METODOLOJİSİNİN GELİŞTİRİLMESİ ÖZET Bu çalışmada, son zamanlarda inşaat sektöründe kullanılmaya başlanılan farklı şekillerde biçimlendirilebilen, açılıp kapanabilir, hareketli yapılar için bütüncül bir tasarım yöntemi geliştirilmiş olup, çok fonksiyonlu ve iklim koşullarına uyum sağlaya...

This research deals with the behavior of Composite Box Girder Bridges (CBGBs) subjected to environmental effects such as solar radiation, atmospheric temperature, and wind speed. It is based on temperature and thermal stress results, which were recorded hourly from a full-scale experimental CBGB segment and Finite Element (FE) thermal analysis. The...

A three-dimensional (3D) finite-element (FE) model with multiple elements was used to simulate a shear connector with static loading. The behaviour of the steel-in-concrete connection was critical to the global behaviour of the structural element. The geometry and material non-linearities of the studded steel beam shear connector were included in t...

A three-dimensional thermal analysis using the finite element method was conducted in this research to evaluate the heat conduction in deep concrete box-girder bridges considering the temperature change of air, the thermal radiation from the sun and the speed of the wind. The current finite element analysis has predicted the concrete temperatures e...

In this paper, the integrated design methodology for flexible, responsively adaptable, deployable, kinematic structures, which are recently starting to use in the construction industry, has been developed and also intended to design a deployable structure which is multi-functional and adapting itself to climatic conditions. Integrated design method...

A three-dimensional (3D) finite-element (FE) model with multiple elements was used to simulate a shear connector with static loading. The behaviour of the steel-in-concrete connection was critical to the global behaviour of the structural element. The geometry and material non-linearities of the studded steel beam shear connector were included in t...

Lap joints are widely used in the manufacture of stiffened panels and influence local panel sub-component stability, defining buckling unit dimensions and boundary conditions. Using the finite element method it is possible to model joints in great detail and predict panel buckling behaviour with accuracy. However, when modelling large panel structu...

Since thin-walled structural analysis and design procedures are utilized for cold-formed steel columns, it is first necessary to understand thin plate behavior to employ proper cross sections which will serve under compression actions. As is well known, thin plates without any longitudinally and/or laterally stiffening elements usually are not pres...

In general, the present bridge design codes introduce special provisions to control the possible effects of thermal loads that results from solar radiation and variation in air temperature. In this research, a thermal finite element analysis was conducted to study the temperature distributions and temperature gradients in precast concrete bridge gi...

The analysis of bridge temperatures during the early age of concrete is a complicated problem. At early ages, cement hydration produces an internal heat, which depends mainly on the chemical composition of cement. This heat is added to the permanent and fluctuated time-dependent heat gained from or lost to the surrounding atmosphere. This continuou...

The objective of this study was to examine the influences of geomaterial properties and geogrid reinforcement on the deformation behavior of an embankment model. Plaxis software, a finite element program, was used for modeling and analyzing the behavior of an embankment. Two types of soil were used in this research. The effect of geogrid reinforcem...

Steel-concrete composite structures are today widely used for bridges and industrial buildings. Headed shear studs provide the transfer of longitudinal shear forces at the interface between both components. In this study, a three-dimensional finite element model using ANSYS software was proposed to study the behaviour of shear connectors allowing f...

The use of composite structures is increasingly present in civil building works. Composite Box Girder Bridges (CBGB), particularly, are study of effect of shear connector’s numbers and distribution on the behavior of CBGBs is submitted. A Predicti structures consisting of two materials, both connected by metal devices known as shear connectors....

The study of bridges in general and composite box girder bridges in particular, requires considerably more information than is contained in codes. A sound understanding of bridge behavior at all stages of loading is essential. Analysis and design of composite box girder bridges is complicated by many factors including composite interaction between...

The effect of the fluctuation of air temperature and solar radiation had been recognized as one of the issues that should be considered in bridge design. The effect of the daily temperature rise and drop can lead to serious thermal movements or stresses along the span of the bridge. Moreover, the nonlinear temperature gradients along the depth of t...

The curvilinear nature of box girder bridges along with their complex deformation patterns and stress fields have led designers to adopt approximate and conservative methods for their analyses and design. The Finite Element (FE) method is the most general of the methods utilized. It can treat any loading and boundary conditions, varying girder dime...

Assembling aircraft stiffened panels using friction stir welding offers potential to reduce fabrication time in comparison to current mechanical fastener assembly, making it economically feasible to select structurally desirable stiffener pitching and novel panel configurations. With such a departure from the traditional fabrication process, much r...

The complexity nature of composite box girder bridges makes it difficult to accurately predict their structural response under loading. However, that difficulty in the analysis and design of composite box girder bridges can be handled by the use of the digital computers in the design. An intricate geometry such as that of composite box girder bridg...

The complexity nature of composite box girder bridges makes it difficult to accurately predict their structural response under loading. However, that difficulty in the analysis and design of composite box girder bridges can be handled by the use of the digital computers in the design. An intricate geometry such as that of composite box girder bridg...

In this study main attention is focused on axial load carrying capacity of steel columns. Towards this aim, employing nonlinear geometric and material properties Finite Element models are generated using ANSYS program. In simulations due to its advantages Arc-Length method is utilized for determination of axial load capacity of columns. Computation...

This study deals with the computational analyzes and weight optimization of transmission towers subjected to static loading. The finite element method is used to determine the stresses and displacements. An automated analysis and optimization procedure which integrate finite element analysis and numerical methods have been used for optimization. Al...

In this paper, the basic finite element formulation of a newly developed family of variable thickness, curved, C(0) continuity Mindlin-Reissner model curved beam elements which include shear deformation and rotatory inertia effects is presented. The accuracy, convergence and efficiency of these newly developed curved beam elements are explored thro...

Today's high-strength materials allow for significant increases in working and limit stresses. To fully exploit material improvements as weight savings on structures, it is desirable to enhance the performance of structural components. The work presented in this paper proposes that the buckling behavior of cold form steel columns may be effectively...

This paper deals with the structural optimization of trusses by maximizing the structural fundamental frequency while maintaining a constant total structure weight or minimizing the structure weight while keeping the structural fundamental frequency over a limited value. The fundamental concept is to find shape and dimensions of trusses in which sy...

This paper deals with the structural analysis and shape optimization of bells. Using modal analysis it is possible to reconstruct the dynamic behavior of the bell by superposition of the excited eigenmodes. An examination of the nodal participation reveals that only a few of these modes are importance to the perceived sound the bell makes. From suc...

Today's high-strength materials allow for significant increases in working and limit stresses. To fully exploit material improvements as weight savings on structures, it is desirable to enhance the performance of structural components. The work presented in this paper proposes that the buckling behavior of cold form steel columns may be effectively...

An optimization procedure is presented for the minimum weight and strain energy optimization for arch structures subjected to constraints on stress, displacement and weight responses. Both thickness and shape variables defining the natural line of the arch are considered. The computer program which is developed in this study can be used to optimize...

This paper deals with the structural optimization of vibrating planar and space trusses. The objective of the present study is to develop a robust and reliable shape optimization tool for vibrating trusses. Natural frequencies are determined using standard finite element matrixdisplacement method. The fundamental concept is to generate structural s...

The present work is concerned with the structural shape optimization of vibrating arches. Natural frequencies and mode shapes are determined using curved, variable thickness, C(0) continuity Mindlin-Reissner finite elements. The whole shape optimization process is carried out by integrating finite element analysis, cubic spline shape and thickness...

Today's high-strength and damage tolerant materials permit significant increases in working-and limit stresses. In order to fully exploit these stress increases as weight savings on aircraft, it is important to improve the buckling stability of stiffened panels. The (post-)buckling performance of panels with sub-stiffening or local tailoring of the...

Today's high-strength and damage tolerant materials allow for significant increases in aluminum working and limit stresses. To fully exploit material improvements as weight savings on aircraft primary structures, it is desirable to enhance the buckling stability of stiffened panels. The work presented in this paper proposes that with the introducti...

This paper deals with the structural shape optimization of prismatic folded plates under buckling load consideration. Buckling loads are determined using linear, quadratic and cubic, variable thickness, C(0) continuity, Mindlin-Reissner finite strips. The whole structural optimization process is carried out by integrating finite strip analysis, cub...

This paper deals with adaptive finite element analysis of linearly elastic structures using different error estimators based on flux projection (or best guess stress values) and residual methods. Presentations are given on a typical h-type adaptive analysis, a mesh refinement scheme and the coupling of adaptive finite element analysis with automati...