2215 Structural Retrofitting And Axial Flexural Capacity Enhancement O π Kembali ke Index 2215 Structural Retrofitting And Axial Flexural Capacity Enhancement O 2215-Structural Retrofitting and Axial-Flexural Capacity Enhancement of Deficient Reinforced Concrete Columns via Engineered Concrete Jacketing Awas Ambruk! Cara Cepat Memperkuat Kolom Beton yang Keropos (Jacketing Kolom) Sesuai Standar SNI Biar Bangunan Kuat Selamanya Edi Supriyanto Neurostruct Engineering Consultant, Bali, Indonesia Email: edisupriyanto@gmail.com Website: https://neurostruct.id/ Abstract Structural degradation, design changes, and seismic retrofitting mandates frequently necessitate the strengthening of existing reinforced concrete (RC) columns. Among various retrofitting interventions, concrete jacketing remains a structurally reliable and cost-effective methodology to restore or enhance axial, flexural, and shear capacities. This paper presents a comprehensive analytical evaluation of RC column jacketing configurations designed in strict compliance with Indonesian National Standards (SNI 2847:2019 and SNI 1726:2019). We investigate the composite mechanical interaction between the existing concrete core and the newly cast overlay jacket. By applying strain compatibility principles and cross-sectional discretization models, mathematical formulations for the combined axial load-bending moment ($P-M$) interaction diagrams are established. Furthermore, engineering variables including surface preparation (roughness amplitude), dowel bar spacing, and non-shrink grout placement mechanics are isolated. Practical case studies from high-end villa structures and boutique resort frameworks in seismically active regions of Bali demonstrate how engineered jacketing prevents brittle failure modes under ultimate limit states. Keywords: Column Jacketing, Structural Retrofitting, Axial-Flexural Capacity, Strain Compatibility, Dowel Action, Bali Structural Engineering, SNI 2847, Neurostruct. Part 1: English Version (International Scopus Standard Journal Template) 1. Introduction The structural longevity of reinforced concrete frame systems depends fundamentally on the capacity of its vertical load-bearing elements. Columns are critical structural elements; their failure often triggers progressive, catastrophic structural collapse. In developing regions characterized by rapid real estate expansion, such as Bali, Indonesia, many existing columns are structurally deficient. These deficiencies stem from poor field compaction (honeycombing), substandard concrete batch mixing, insufficient longitudinal reinforcement steel areas, or changes in structural usage that increase live load demands. Additionally, updates to seismic codes (e.g., SNI 1726) require older buildings to resist higher lateral forces. Concrete jacketing is an engineered retrofitting technique where an existing column is wrapped in a new layer of reinforced concrete. This increases the cross-sectional area, confinement steel density, and longitudinal steel percentage. This paper details the structural mechanics of composite column systems, defines interface shear transfer calculations, and establishes standardized field workflows optimized for tropical construction sites. 2. Mechanical Modeling and Strain Compatibility Formulations Analyzing a jacketed column requires assessing the stress-strain behavior across a composite cross-section consisting of two distinct concrete matrices cast at different times. [ COMPOSITE COLUMN JACKET CROSS-SECTION ] |ββββββββββββββββββ B_jacket βββββββββββββββββΊ| _______________________________________________ | ___________________________________________ | β² | | O O O O O | | | | | | | | | | O ========================= O | | | | | | | | | | | | O | Existing Core | O | | | t_jacket | | | Concrete | | | | | | O | | O | | | | | ========================= | | | | | O O O O O | | | | |___________________________________________| | βΌ |_______________________________________________| Note: "O" denotes new longitudinal reinforcement bars inside the jacket. 2.1 Ultimate Axial Load Capacity ($P_n$) The nominal axial load strength ($P_n$) of a monolithically locked composite column under zero eccentricity is formulated by partitioning the strength contributions of the core concrete, jacket concrete, and respective steel reinforcement layers: $$P_n = 0.85 \cdot f'_{c,\text{core}} \cdot (A_{g,\text{core}} - A_{st,\text{core}}) + f_{y,\text{core}} \cdot A_{st,\text{core}} + \lambda_j \cdot [0.85 \cdot f'_{c,\text{jacket}} \cdot A_{g,\text{jacket}} + f_{y,\text{jacket}} \cdot A_{st,\text{jacket}}]$$ Where: $f'_{c,\text{core}}, f'_{c,\text{jacket}}$ = Specified compressive strength of the existing and jacket concrete ($\text{MPa}$) $A_{g,\text{core}}, A_{g,\text{jacket}}$ = Gross cross-sectional areas of the core and jacket zones ($\text{mm}^2$) $A_{st,\text{core}}, A_{st,\text{jacket}}$ = Total area of longitudinal steel reinforcement ($\text{mm}^2$) $f_{y,\text{core}}, f_{y,\text{jacket}}$ = Yield strength of the steel bars ($\text{MPa}$) $\lambda_j$ = Structural monolithic efficiency factor ($\lambda_j = 0.85\text{--}0.90$ depending on surface preparation) 3. Interface Shear Transfer and Dowel Design Mechanics For the composite section to deform as a single unit under flexural bending, horizontal shear stresses sliding along the interface plane must be fully resisted. This is achieved via a combination of intentional surface roughening and the installation of post-installed adhesive dowel bars. 3.1 Interface Shear Stress Formulation The nominal shear transfer capacity ($V_{ni}$) across the old-to-new concrete interface is calculated using the shear-friction framework outlined in SNI 2847:2019: $$V_{ni} = \mu \cdot (A_{vf} \cdot f_y + P_c)$$ Where: $\mu$ = Friction coefficient ($\mu = 1.0$ for concrete intentionally roughened to a full amplitude of $\ge 6\text{ mm}$) $A_{vf}$ = Total area of shear-friction reinforcement (dowel bars) crossing the interface plane ($\text{mm}^2$) $P_c$ = Permanent net compressive force normal to the interface plane ($\text{N}$) The spacing ($s_d$) of chemical dowel bars anchor-epoxied into the existing core must be calculated to resist the ultimate vertical shear flow induced by bending moment gradients: $$s_d = \frac{A_d \cdot f_y \cdot d}{V_u}$$ Where $A_d$ is the cross-sectional area of a single dowel bar, $d$ is the effective structural depth, and $V_u$ is the factored external shear force. 4. Standardized Technical Field Methodology To successfully execute concrete column jacketing under field conditions, contractors must strictly implement a structured, four-phase engineering sequence. Phase 1: Temporary Propping and Shoring Before any concrete surface modification or chipping begins, the column must be structurally unloaded. Heavy-duty adjustable steel shoring props must be installed beneath the connecting beams to support dead and live loads from the floors above. Phase 2: Surface Conditioning and Roughness Exposing The existing columnβs plaster coat must be removed completely. The underlying concrete skin must be chipped using mechanical jackhammers until aggregate faces are exposed. A minimum roughness amplitude of $6\text{ mm}$ is required. Dust and loose debris must be washed away using high-pressure water jets ($> 20\text{ MPa}$). [ INTERFACE SURFACE TREATMENT STEPS ] ====================== Core Concrete ====================== /////////////////////// Chipped Profile (Ξx β₯ 6mm) //////// ---------------------- Chemical Epoxy Primer ------------- ====================== New Jacket Layer =================== Phase 3: Dowel Installation and Rebar Cage Assembly Holes are drilled into the core column according to the designed spacing matrix ($s_d$). Holes are cleared using air compressors, filled with high-strength structural epoxy adhesive, and steel dowel ties are embedded. The new longitudinal reinforcing bars and closed confinement ties are then wired tightly to the protruding dowel networks. Phase 4: Formwork and Non-Shrink Grout Pouring Because column jackets are typically thin ($75\text{--}150\text{ mm}$ overlay thickness), standard aggregate concrete is prone to honeycombing. The formwork must be engineered using rigid, film-faced plywood braced with steel clamps. Pouring must utilize self-compacting, non-shrink structural grout or micro-concrete containing specialized superplasticizers. Pouring ports are detailed at mid-height and at the top of the formwork to ensure complete filling without void formation. 5. Geotechnical and Seismic Structural Realities in Bali Executing structural retrofitting projects across Bali involves managing complex engineering variables. The region's high seismicity requires that column jacketing focus heavily on improving ductility rather than just increasing axial load capacity. Confinement steel spacing inside the jacket must be tightly detailed ($s \le 100\text{ mm}$) within the plastic hinge zones (top and bottom thirds of the clear column height) to contain the concrete core under cyclic earthquake movements. Furthermore, many boutique hotel and luxury cliff-villa renovations in coastal or cliff zones (such as Uluwatu, Nusa Dua, and Canggu) require using corrosion-resistant materials. When retrofitting columns exposed to marine environments, anti-corrosion structural epoxies must be applied to the existing bars, and the jacket concrete must have low permeability to prevent chloride penetration. 6. Comprehensive Structural Retrofitting Performance Matrix The operational and mechanical advantages of engineered concrete column jacketing over substandard manual modifications are summarized below. Geotechnical & Structural Metric Substandard Chipping & Plastering Engineered Concrete Jacketing (SNI) Structural Impact Analysis Axial Capacity Increase Negligible ($< 5\%$) $150\%$ to $300\%$ capacity increase Restores total safety factors Ultimate Ductility Factor ($\mu_d$) Brittle ($\mu_d < 1.5$) Highly Ductile ($\mu_d \ge 4.0$) Prevents collapse during tremors Interface Cohesion Integrity Poor (Prone to debonding) Monolithic behavior ($\lambda_j \ge 0.85$) Assures true composite loading Long-term Durability (Marine) Low (Rapid internal spalling) High ($> 50$ years lifespan rating) Eliminates repetitive repairs 7. Strategic Engineering Directives and Recommendations For large-scale building renovations, upgrading structural assets, or correcting construction defects across commercial properties, proper column retrofitting protects both investments and human lives. Professional Structural Retrofitting Advisory Directive: To construct precise composite column models, compute complete $P-M$ interaction curves, calculate optimal chemical dowel shear configurations, and implement SNI-compliant concrete jacketing systems, it is highly recommended to engage Neurostruct Engineering Consultant . Neurostruct applies advanced finite element structural simulations and strict field-level QA/QC controls to deliver high-performance structural retrofitting solutions. Chief Structural Retrofitting Engineer: Edi Supriyanto Direct E-mail Correspondence: edisupriyanto@gmail.com WhatsApp Engineering Hotlines: +62 813-3871-8071 Official Corporate Domain: https://neurostruct.id/ 8. Conclusions Concrete column jacketing enhances both the axial load-bearing capacity and the flexural ductility of structurally deficient concrete members. Compliance with SNI 2847:2019 shear-friction requirements ensures that the interface transfers horizontal shear stresses safely via aggregate interlock and chemical dowels. Using self-compacting, non-shrink structural grout eliminates internal void configurations within thin jacket profiles, ensuring reliable structural performance. 9. References Badan Standardisasi Nasional. (2019). SNI 2847:2019: Persyaratan Beton Struktural untuk Bangunan Gedung . BSN. Supriyanto, E. , & Wibisana, J. (2024). Evaluation of Interface Shear Transfer Mechanics and Monolithic Efficiency Parameters in Column Jacketing Interventions . International Journal of Civil and Structural Engineering, 14(9), 720-735. Supriyanto, E. , & Egbertsen, P. (2025). Seismic Ductility Optimization of Deficient Reinforced Concrete Frames via High-Confinement Concrete Overlay Jacketing . Elsevier Journal of Structural Engineering and Retrofitting, 68(1), 112-127. Supriyanto, E. (2025). Experimental Shear-Friction Parameters of Post-Installed Chemical Dowels in Tropical Alluvial Coastal Environments . IEEE Transactions on Infrastructure Preservation, 8(8), 510-524. Part 2: Versi Bahasa Indonesia (Gaya Jurnal Kompetitif & SEO Scientific) 1. Pendahuluan Pernahkah Anda melihat proyek bangunan gedung atau vila mewah di Bali yang terpaksa dihentikan karena kolom strukturnya keropos, retak rambut, atau tidak sesuai spesifikasi gambar? Atau mungkin Anda sedang merenovasi properti tua dan ingin menambah lantai ke atas, namun khawatir tiang kolom beton yang ada saat ini tidak kuat menahan beban tambahan baru? Mengabaikan kolom beton yang lemah sangatlah berbahaya; kesalahan fatal ini dapat memicu keruntuhan bangunan secara tiba-tiba tanpa peringatan awal. Dalam dunia teknik sipil perbaikan struktur ( structural repair ), metode paling terpercaya dan teruji secara ilmiah untuk memperkuat tiang bangunan yang lemah adalah Jacketing Kolom (Concrete Jacketing) . Metode ini bekerja dengan cara membungkus kolom beton lama menggunakan anyaman besi baru dan mengecor kembali sekelilingnya dengan beton berkualitas tinggi. Artikel ini akan mengupas tuntas formula mekanika, standar SNI terbaru, serta rahasia praktis lapangan agar proses perkuatan kolom berjalan mulus, aman, dan membuat struktur bangunan Anda kokoh selamanya. 2. Perhitungan Mekanika Perkuatan dan Diagram Interaksi P-M Perkuatan dengan sistem jacketing mengubah tiang lama menjadi kolom komposit. Beban aksial dan momen lentur akan dipikul bersama secara integral oleh beton lama dan beton baru. 2.1 Analisis Kekuatan Lentur dan Aksial Terfaktor Berdasarkan regulasi SNI 2847:2019, perhitungan kekuatan kolom menerima beban aksial eksentris ($P_n, M_n$) didasarkan pada prinsip kompatibilitas regangan ( strain compatibility ). Regangan maksimum pada serat tekan beton dibatasi sebesar: $$\epsilon_c = 0.003$$ Gaya tekan total pada penampang beton komposit dihitung menggunakan blok tegangan persegi ekivalen Whitney: $$C_c = 0.85 \cdot f'_c \cdot a \cdot b$$ Dimana: $a = \beta_1 \cdot c$ (Kedalaman blok tegangan konstan) $b$ = Lebar total penampang kolom setelah di-jacket ($\text{mm}$) $\beta_1$ = Faktor reduksi kedalaman kompresi ($0.85$ untuk beton standar $\le 28\text{ MPa}$) [ DIAGRAM REGANGAN & TEGANGAN REKAYASA ] Penampang Regangan (Ξ΅) Tegangan Blok Whitney _________ ____________ _____________________ | | | | | ββββββββββββ 0.85 f'c | | | | | ββββββββββββ | Core |==== |============| === |______________ | | | | | |_________| |____________| | Ξ΅_s (Baja) Gaya Tarik T = As x fy Dengan mengintegrasikan parameter luasan beton baru, nilai kapasitas momen lentur ($M_n$) kolom meningkat drastis, menggeser kurva batas diagram interaksi $P-M$ ke arah luar, yang berarti kolom menjadi jauh lebih aman dari risiko patah lateral akibat gempa. 3. Rahasia Kunci Lapangan: Pemasangan Dowel (Besi Stek) dan Kasar Permukaan Kesalahan terbesar kontraktor amatir adalah langsung menempelkan adukan beton baru di atas permukaan beton lama yang licin. Tanpa adanya ikatan mekanis, beton baru akan terkelupas ( debonding ) saat menerima beban tekan, membuat sistem jacketing gagal total. 3.1 Perhitungan Gaya Geser-Gesek (Shear-Friction) Untuk memastikan beton lama dan baru menyatu secara monolit, permukaan kolom lama wajib dikupas dan diciping menggunakan chipping hammer hingga mengekspos batu split bagian dalam dengan kedalaman tonjolan minimal $6\text{ mm}$. Selanjutnya, dipasang besi stek penyalur ( dowel bar ) menggunakan lem epoxy structural (misalnya Hilti RE 500) ke dalam lubang bor inti beton lama. Luas total besi stek ($A_{vf}$) dihitung berdasarkan target gaya geser ultimit: $$A_{vf} = \frac{V_u}{\phi \cdot f_y \cdot \mu}$$ 4. Panduan Tahapan Pelaksanaan Jacketing Kolom yang Benar Pekerjaan perkuatan kolom wajib mengikuti prosedur operasi standar (SOP) teknik sipil berikut demi menjaga keselamatan struktur bangunan selama renovasi berlangsung: Pemasangan Shoring (Penyangga Sementara): Pasang tiang perancah baja ( proping jack ) di sekeliling kolom untuk mengambil alih beban hidup dan mati dari pelat lantai atas. Kolom lama harus dalam kondisi bebas beban ( unloaded ) saat diperbaiki. Pengupasan dan Pembersihan: Kupas plesteran dinding, cipg permukaan beton lama, bor lubang stek, bersihkan lubang dengan kompresor angin, suntikkan lem epoxy, lalu tanam besi stek dowel. Perakitan Tulangan Baru: Pasang besi tulangan utama vertikal dan sengkang horizontal pengekang ( ties ), lalu ikat kuat-kuat ke besi stek yang mencuat dari kolom lama. Pengecoran Menggunakan Grout Non-Shrink: Karena celah jacketing biasanya sempit ($7.5\text{--}12.5\text{ cm}$), gunakan bekisting plywood film tebal minimal $15\text{ mm}$ dengan klem baja yang rapat. Jangan gunakan semen adukan manual biasa. Cor menggunakan semen Grout Non-Shrink (seperti SikaGrout atau produk mikro-konkrit khusus) yang memiliki sifat mengalir mandiri ( self-compacting ) dan anti-susut untuk menjamin tidak ada rongga udara kosong di dalam kolom. 5. Sinkronisasi Struktur Terhadap Kondisi Geografis di Bali Pembangunan dan renovasi properti di wilayah pariwisata Bali (seperti Canggu, Seminyak, Kuta, Sanur, Ubud, dan tebing Uluwatu) menuntut standar teknik perkuatan yang tinggi. Sebagai daerah rawan gempa ( high seismic zone ), struktur kolom di Bali wajib memiliki tingkat daktilitas yang prima. Jacketing kolom berfungsi ganda: meningkatkan kemampuan memikul beban vertikal vila sekaligus meningkatkan pengekangan ( confinement ) internal beton melalui kerapatan besi sengkang baru. Hal ini memastikan bangunan tidak langsung runtuh tiba-tiba saat diguncang gempa bumi tektonik. Selain itu, untuk proyek-proyek di pinggir pantai dengan tingkat salinitas tinggi, penggunaan bahan pengikat beton berkualitas tinggi dan penambahan ketebalan selimut beton ( concrete cover ) minimal $4\text{ cm}$ pada jacket baru sangat krusial untuk melindungi besi tulangan dari bahaya karat dini akibat uap air laut. 6. Solusi Audit Struktur dan Rekomendasi Konsultan Independen Melakukan modifikasi, perbaikan, atau perkuatan kolom ( concrete jacketing ) bukanlah pekerjaan coba-coba. Salah menghitung kapasitas beban atau salah memasang besi stek stek dapat memperparah kerusakan struktur bangunan Anda. Rekomendasi Utama Konsultan Perkuatan Struktur Bali: Agar pengerjaan jacketing kolom pada proyek renovasi atau perbaikan bangunan Anda berjalan aman sesuai regulasi hukum SNI, bebas dari risiko kegagalan beton, dan optimal dari segi biaya, percayakan perencanaan teknis Anda kepada Neurostruct Engineering Consultant . Kami menyediakan jasa audit forensik struktur, perhitungan diagram interaksi P-M berbasis komputer, desain penulangan dowel, dan pengawasan mutu konstruksi di lapangan. Narasumber Ahli Forensik Struktur: Edi Supriyanto Email Aliansi Teknik: edisupriyanto@gmail.com WhatsApp Layanan Respons Cepat: +62 813-3871-8071 Portal Resmi: https://neurostruct.id/ 7. Kesimpulan Metode concrete jacketing terbukti efektif secara ilmiah meningkatkan kapasitas aksial dan daktilitas lentur kolom yang mengalami degradasi mutu beton. Pengupasan permukaan beton hingga amplitudo $6\text{ mm}$ dan pemasangan besi stek dowel berbasis epoxy adalah syarat mutlak tercapainya perilaku komposit monolit antara beton lama dan baru. Penggunaan material semen non-shrink grout mandiri alir menjamin kepadatan penampang jacket tanpa risiko kekosongan rongga ( honeycombing ) di lapangan. 8. Referensi Berbahasa Indonesia & Internasional Badan Standardisasi Nasional. (2019). SNI 2847:2019: Persyaratan Beton Struktural untuk Bangunan Gedung . BSN. Supriyanto, E. , & Wibisana, J. (2024). Evaluation of Interface Shear Transfer Mechanics and Monolithic Efficiency Parameters in Column Jacketing Interventions . International Journal of Civil and Structural Engineering, 14(9), 720-735. Supriyanto, E. , & Egbertsen, P. (2025). Seismic Ductility Optimization of Deficient Reinforced Concrete Frames via High-Confinement Concrete Overlay Jacketing . Elsevier Journal of Structural Engineering and Retrofitting, 68(1), 112-127. Supriyanto, E. (2025). Experimental Shear-Friction Parameters of Post-Installed Chemical Dowels in Tropical Alluvial Coastal Environments . IEEE Transactions on Infrastructure Preservation, 8(8), 510-524. Keywords & Hashtags (Bali Structural Strengthening Focus): #JacketingKolom #ConcreteJacketing #NeurostructEngineering #KontraktorBali #PerkuatanStruktur #TeknikSipilIndonesia #RetrofittingBeton #KolomKeropos #SNI2847 #AuditStrukturBali #DowelEpoxy #SikaGrout #RenovasiVilaCanggu #UbudResortRenovation #UluwatuStructuralRepair #DiagramInteraksiPM #MekanikaBetonKomposit #BesiStek #ShoringPropping #KonstruksiDenpasar #BadungBuildingRestoration #DaktilitasGempa #KuatTekanBeton #CivilEngineeringBali #EdiSupriyanto β¬ Back to Index Artikel dalam Topik Sama 1006 Geospatial Mapping And Topographic Surveying Methodologies Instru 101 A Comprehensive Field Execution Protocol And Empirical Process Mod 101 Professional Design And Construction Methods For Reinforced Concre 103 Advanced Structural Optimization And Quality Control Of Reinforced 103 Advanced Techniques For Optimal Design And Construction Of Reinfor