Strut and tie model optimization for reinforced concrete bridge pier head structure using a genetic algorithm

Strut and tie model (STM) is more suitable to design the pierhead structures which resist high shear forces transferred from the girders. These pierhead structures behave like the disturbed regions as in reinforced concrete deep beam. The design of the struts and ties elements requires the initial geometry configuration of the truss model where its boundaries are limited by the shape of the pier head structures. To find the optimum topological shape of the truss model, the genetic algorithm (GA) optimization technique is used in this paper. The objective functions in the GA optimization consisted of minimizing the usage of concrete and steel reinforcement material and ensuring all the stress ratio of the strut and tie elements are less than equal to unity. Both prestressed and non-prestressed pierheads are investigated in this paper. The use of prestressing in the pierhead structures reduces the stresses in the main tension tie significantly and allowing some members of the shear tie and compression struts to have almost zero stresses. For these elements with zero stresses, the elements can be removed and reduces the concrete and rebar materials usage. Furthermore, the genetic algorithm optimization is found to be successful to ensure all the stress ratio in the members to be less than equal to unity

Plastic dilation rate characteristic of concrete confined with steel tube

The use of external confining devices to confine concrete has become widely used. One of the purposes is to gain additional concrete strength and ductility. Although there are many types of external confining devices, in this paper, the attention is limited to the use ofthe steel tube as anexternal confining device. One of the main objectives ofthis research is to study the plastic dilation rate behavior of concrete-filled-steel-tube (CFST) columns. The experimental data for the plastic dilation rate is extracted, and compared with the authors concrete plasticity model. In the authors’ previous research, the calibration of the plastic dilation rate model was based on confined concrete tested under both active and passive confinement using FRP wraps. Since the behavior of the steel tube and the FRP materials are different, the author’s plastic dilation rate model needs to be re-evaluated for CFST columns. Comparisons of the extracted experimental plastic dilation rates with the model prediction for CFST specimens with normal strength concrete show good agreement and requires no adjustment in the formulation. However, for a specimen with 80 MPa concrete, the proposed formulation showsslightly lowerplastic dilation rates.More experimental data for CFST using high strength concretes is required for further investigation. For the sake of completeness, the overall response of two CFST specimensisalso evaluated using anin-house three-dimensional non-linear finite element analysis (3D-NLFEA) using the author’s proposed plasticity formulation for confined concrete

Strut and tie model optimization for reinforced concrete deep beam using genetic algorithm

This paper presents strut and tie model structural optimization of reinforced concrete deep beam using genetic algorithm. Genetic algorithm is used as the optimization platform as it does not require differentiation of the exact mathematical formulation to get the optimum solution. The force analysis is carried out using two-dimensional linear finite element method with truss element. The struts and ties design are based on ACI 318. One RC deep beam example is presented as an example. During optimization, there are two constraints which consisted of strength of the member alone and combination with deformation limit of the nodes. The stress ratio for both struts and ties are set to not exceed unity while the deformation was limited to 2.0 mm. From the optimization analysis, it can be concluded that genetic algorithm can be used to get the most optimum structural configuration which yield the most economical solution for design purposes. On the other hand, it is found out that optimizing only the strength alone can yield a more economical solution compared to the design references. However, if deformation constraint is added in the optimization parameters, larger deep beam depth is required to satisfy the deformation limits

NUMERICAL INVESTIGATION OF GEOPOLYMER REINFORCED CONCRETE BEAMS UNDER FLEXURAL LOADING USING 3DNLFEA

The development of geopolymer concrete is one of the most significant breakthroughs to replace the OPC concrete causing global warming issues. Investigations on the structural behavior of geopolymer concrete are limited and still need adjustments in numerical simulations to experimental results in previous studies. This study investigated the flexural behavior of geopolymer concrete as a structural member using the numerical method. The utilization of the finite element method is an alternative to widely determining the structural behavior of geopolymer concrete as a construction material. In this study, the author refers to the research conducted by Pham et al. The research developed a four-point bending test with variations in tensile steel reinforcement ratio. The results of the experimental tests that Pham has carried out will be verified by numerical simulation in three dimensions. The validation of experimental specimens with numerical specimens is done to compare the moment-curvature and the crack pattern of concrete. Numerical investigation accurately captures the structural behavior of moment-curvature and crack pattern of geopolymer concrete. The moment maximum deviation between experimental and numerical results is 1.3 to 2.4%. However, there are differences in the number and length of cracks in the bending moment area. The difference of crack pattern in the bending moment area between experimental results and numerical results due to the modeling did not consider the input of fracture energy. The experiment from referenced studies did not include fracture energy data, so the 3DNLFEA modeling used the fracture energy value of OPC concrete

NON-LINEAR SECTIONAL ANALYSIS OF CONCRETE ENCASED STEEL STUB COLUMN SUBJECTED TO AXIAL LOAD

This paper presents a numerical parametric study of Concrete Encased Steel Column (CESC) due to centrically and eccentrically axial load. To model the confining pressure of rebar and steel profile, modified Mander’s equations was used. The non-linear sectional analysis was performed using an in-house NL-Column program using the fiber-based method. The CESC section was discretized using Netgen 2D meshing algorithm. The developed CESC model was validated using the available test results in the literature. After model was validated, parametric studies were carried out to investigate the behaviors of CESC with different concrete compression strength, confinement bar diameter, and confining space. The parametric studies found that the column with higher concrete compression strength tend to have higher axial and flexural capacity but reduce the overall ductility. Increasing the confinement bar diameter slightly increases the axial and flexural capacity and ductility on the other hand, utilizing tighter confinement space resulted in higher ductility but with small increase in axial and flexural capacity

DUCTILITY EVALUATION OF REINFORCED CONCRETE COLUMN MADE OF NORMAL- TO HIGH-STRENGTH CONCRETE UNDER CONSTANT AXIAL LOAD LEVEL COMBINED WITH FLEXURAL LOADING USING NONLINEAR SECTIONAL FIBER BASED MODEL

This study presents the ductility evaluation of reinforced concrete column made of normal-strength material using various empirical stress-strain model with nonlinear sectional fiber based analysis. The purpose is to evaluate the confinement requirement for reinforced concrete column under high axial load level. The concrete strength considered in the analysis are varies from 30 to 70 MPa while the steel reinforcing bar yield strength considered is only 400 MPa. The ductility is evaluated by using the customized ductility index measurement. The ratio of the concrete cover to the concrete core is set to 0.1 but not more than 40 mm. Attard and Setunge’s concrete constitutive model is used in this investigation. Cover spalling behavior is considered in the analysis by including the restrained shrinkage effect on the concrete strength and the softening behavior. From this study, it was found that extra confinement is necessary to maintain the expected minimum level of ductility

Evaluasi Perancangan Jembatan Longspan Cililitan Proyek LRT Jabodebek Menggunakan Balanced Cantilever Precast Post-Tensioned Box Girder

Dalam perencanaan proyek Longspan Cililitan Proyek LRT Jabodebek mengacu pada Perpres No 65 Tahun 2016, Kementrian Perhubungan selaku owner membawahi supervising consultant dan Project Government Auditor menunjuk PT Adhi Karya (Persero), Tbk. selaku design and built contractor dan PT. Kereta Api Indonesia sebagai operator. Kontraktor harus mememiliki beberapa konsultan yang tertera dalam kontrak sebagai syarat wajib dalam perencanaan proyek tersebut. Yang pertama adalah konsultan untuk membuat Detail Engineering Design (DED). Yang merencanakan detail dimensi dari proyek jembatan bentang panjang. Tetapi penyiapan dokumen Detail Engineering Design oleh konsultan perencana atau kontraktor belumlah cukup untuk meyakinkan dan menjamin kehandalan produk engineering dapat dilaksanakan secara efektif dan efesien. Oleh karena itu diperlukannya pemeriksaan pembuktian oleh pihak ketiga seperti konsultan Independent Proof Checker (IPC) sebagai dasar pertimbangan dan memberikan masukan atau saran sebelum akhirnya desain yang digunakan dinyatakan layak untuk dilanjutkan ke tahap konstruksi. Dalam tugas akhir ini, penulis akan merencanakan ulang Jembatan Longspan LRT Cililitan dengan menggunakan precast posttensioned box girder sepanjang 198 meter yang terdiri dari 3 bentang, masing masing 54 m, 90 m dan 54 m. Struktur jembatan yang direncanakan untuk double track. Dengan menggunakan metode balanced cantilever. Perencanaan harus memperhatikan stabilitas struktur dalam tiap tahap pengerjaannya. Dalam perencanaannya dilakukan perhitungan sebagai Independent Proof Checker (IPC) yang diharapkan dapat menjadi pembanding dari perhitungan Detail Engineering Design (DED) yang sudah ada

Desain Modifikasi Perancangan Struktur Gedung The Alton Apartment Semarang Menggunakan Metode Pracetak

Gedung The Alton Apartment Semarang merupakan bangunan tipe hunian yang memiliki 30 lantai dan 2 basement, dengan ketinggian bangunan 96 meter, menggunakan metode cor ditempat. Sehingga memerlukan waktu pelaksanaan relatif lama, juga hasil yang kurang presisi. Dalam perkembangan teknologi, menuntut adanya efisiensi dari segi kecepatan, mutu dan biaya. Salah satu alternatif menggunakan metode pracetak. Beton pracetak memiliki beberapa keunggulan. Antara lain, kemudahan dalam pengerjaan, kecepatan dalam pelaksanaan, dan kontrol kualitas yang baik. Sehingga dalam tugas akhir ini, dilakukan modifikasi gedung The Alton Apartment Semarang menjadi 20 lantai dan 1 basement menggunakan metode beton pracetak yang diterapkan pada balok, plat, dan kolom. Metode pracetak memiliki perhatian khusus pada sambungan, karena sambungan pada beton pracetak tidak semonolit beton cast in situ. Dalam Tugas Akhir ini, perencanaan struktur gedung The Alton Apartment Semarang mengacu pada peraturan SNI 2847:2019, PCI Handbook 6th Edition dan SNI 1726:2019. Untuk menyambung setiap tulanganya, menggunakan reinforcement splice technology berupa spiral confined yang terbuat dari tulangan polos, yang telah dikembangkan di Indonesia sejak tahun 2014. Gedung The Alton Apartment berlokasi di kabupaten Semarang, memiliki Kategori Desain Seismik (KDS) D, direncanakan menggunakan sistem rangka pemikul momen khusus serta dinding struktural

Experimental and Numerical Bending Analysis of Steel/Resin-Talk Sandwich Material

Sandwich material can be used as the substitute for the ship conventional material. The core sandwich material used in this study consisted of a talk-resin-catalyst. The core mixture proportion is 90% resin and 10% talk. A thick steel plates is used as the face of the core sandwich material. Both experimental and numerical simulations are carried out to investigate the bending or flexural behavior of the proposed sandwich material. Three-point bending test has been carried out to determine the yield stress and maximum stress as well as the damage mechanism of the specimen up-to failure. From the investigation, the first failure process occurred at the mid-span as flexural cracks. As the load continue, these flexural cracks progressed until fully fracture of the core material take places. From the experimental investigation, it was found that the yield stress and maximum stress of the sandwich panel are 22.88 MPa and 28.63 MPa. On the other hand, numerical simulation is carried out using ABAQUS which has shown to be sufficient to predict the response of the sandwich-panel. However, a more sophisticated constitutive model is required to successfully model the experimental behavior in close agreement