Gioi thieu chung ve Kiem dinh do cong veh trong cong trinh xay dung
Khi tham quan hoac danh gia bat ky co co cong trinh nao, dac biet la cac cong trinh dan dung va cong nghiep co kich thuoc lon, viec nhin mat bang mat khong bao gio duoc xem la mot phan tich khoa hoc. Mot trong nhung yeu to quyet dinh den tinh vat chat va su binh yen cua he khung chiu luc chinh la do cong veh. Trong hanh nghe kiem dinh xa y dung, doi tuong nay luon duoc danh gia la mot chi tieu "keo dai" nhat va de xuat loi nhat.
Kiem dinh do cong veh khong don gian chi la vien dong may do vao mot so lieu. Do la qua trinh phan tich toc hop cac yeu to: thi cong, chat luong vat lieu, thiet ke ban dau va su thay doi cua moi truong theo thoi gian. Lam boi noi dung nay, chung toi - Kiem Dinh Xay Dung Mien Nam - se cung cap cho ban mot cuc trieu chi tiet ve cach dien dich, phan loai, bien phap do luong va tien hanh kiem dinh do cong veh mot cach khoa hoc va chinhxac nhat.
Trong bat ky cong trinh nao, khong the tranh khoi nhung sai sot nho ve mat hinh hoc. Tuy nhien, giua mot "lo loit" va mot "khiem khuyet tai hai" la mot khoang cach rat mong manh. Kiem dinh do cong veh ra doi de lam ro khoang cach nay, dam bao rang cong trinh van dang trong trang thai an toan, chap nhan duoc voi cac tieu chuan Viet Nam va Quoc te.
Cơ so phap ly va Tieu chuan ky thuat ap dung
De viec kiem dinh co gia tri phap ly va ky thuat, chung toi phai dua tren mot he thong van ban phap luat hoan chinh. Tai Viet Nam, hoat dong nay khong the lam mot cach mang tinh. Noi dung lien quan den kiem dinh do cong veh va cac khuyet tat ve hinh hoc dugc quy dinh rui trong nhieu van ban phap luat cao nhat.
Nhung van ban phap luat nen tang
- Luat Xay dung 2014 (va cac van ban sua doi, bo sung): Dieu 116 quy dinh ve viec thanh lap, hoat dong cua to chuc kiem dinh doc lap. Cong trinh sau khi xay dung xong hay trong qua trinh su dung deu phai duockiem tra tinh toan kha nang chiu luc va tinh vuong goc.
- Nghi dinh 06/2021/NĐ-CP: Day la van ban quan trong nhat hien hanh, quy dinh chi tiet ve quan ly chat luong xay dung. Theo do, cac san pham, van pham xay dung neu khong dat tieu chuan thiet ke va tieu chuan ky thuat (bao gom do chech lech, do vong vung) se bi ket khong chap nhan hoac phai co bien phap xu ly.
- QCVN 06:2021/BXD: Qui chuan ky thuat quoc gia ve an toan cong trinh xay dung. Van ban nay quy dinh cac yeu cau toi thieu ve chiu luc, bao ve chong chay va khong chi dam bao an toan cho con nguoi ma con bao ve cuoi cong trinh.
"Tieu chuan ky thuat khong chi la con so, ma la 'lua' de lochot cac cong trinh khong dat yeu cau. Vi vay, mot chu thau hay chu dau tu can hieu ro cac van ban nay truoc khi giao viec kiem dinh." - Chuyen vien ky thuat Kiem Dinh Xay Dung Mien Nam.
Cac tieu chuan ky thuat co ban (TCVN)
De tien hanh kiem dinh, cac ky su cua chung toi se ap dung truc tiep cac tieu chuan viet nam (TCVN) lien quan. Cac tieu chuan nay duoc tap hop va dua ra cac gioi han cho phep (tolerance).
- TCVN 9438:2012: Co cong xay dung - Thi cong va nghia thu cong. Tieu chuan nay quy dinh ve do chech lech, do song mac va do vong vung cua cot, dam, ban.
- TCVN 4453:1995: Cong trinh thon gop - Quy trinh cong nghe thi cong va nhan bien ban. Duoc su dung nhieu trong cac cong trinh cu.
- TCVN 6327:1998 (va TCVN 5755:1993): Lien quan den cong tac dat va do duong day, dam bao do chinh xac trong thi cong.
- TCVN 4054:2012 (Duong oto): Neu la cong trinh giao thong, tieu chuan nay se duoc ap dung de kiem tra do song mac cua mat duong.
Phan tich nguyen nhan dan den tinh trang cong veh trong cong trinh
Vi sao co the xuat hien hien tuong cot benh, dam u, hay ban beo khong dong deu? De giai quyet van de, chung ta phai tim ra goc.nguyen. Voi kinh nghiem thanh lap tu nhieu nam trong linh vuc Kiem Dinh Xay Dung Mien Nam, chung toi da phan loai cac nguyen nhan thanh 4 nhom chinh.
1. Nguon goc tu thiet ke (Design Errors)
Bat dau tu giai doan mau me, neu viec tinh toan kha nang chiu luc khong chinh xac, hoac chon tieng tam (section) cua cot/dam khong phu hop voi tai troi thuc te, cong trinh se co xu huong uong, vung sau mot thoi gian. Vac vi, viec thiet ke khong tinh den hieu ung nhiet do (thermal effect) co the lam cho co co cong trinh bi dahn, bong ra, dan den do cong veh tuong doi.
2. Nguon goc tu vat lieu va qui trinh thi cong (Construction & Materials)
Day la nguyen nhan pho bien nhat. Cau tao betong (concrete) co dac diem la co su co hang va co khi (shrinkage). Neu thi cong khong dong deu, hoac viec thuc day (curing) khong tot, betong se bi co lac khong deu, gay ra luc noi bo dan den beo cong.
Mat khac, viec bo go (formwork removal) muon hay som cung anh huong rat lon. Neu bo go muon, co the gay ra suc nong (stress) trong betong khi no khong chua co du do dai. Ngoai ra, viec dat co the (rebar) sai vi tri (duoi day beo) se lam giam kha nang chiu luc, tang do vong.
3. Yeu to Moi truong va Su dung (Environment & Usage)
Doi voi cac cong trinh co su dung da qua nhieu nam, su luan khong deu cua nen nha (settlement) la nguyen nhan chien loy. Khi mot phan nen nha bi luan nhieu hon phan con lai, toa cong trinh bi uong, dam va cot bi benh. Khie luan khong deu, cac phan tu be tong co the bi tran, beo, dan den tinh trang nguy hiem.
Chinh nhiet do va do am thay doi theo mua cung gay ra su nong co la (expansion and contraction). Nen co cac cong trinh bi uong do nhiet do gay nen, dac biet la cac cong trinh co ket cau thep.
4. Su thay doi chuc nang (Change of Function)
Mot so cong trinh sau khi xay dung, chu dau tu thay doi muc dich su dung. Vi du, tir nha o thanh kho, tu van phong thanh cong ty san xuat. Luc luong tang len, tai troi tang len, dan den cong trinh khong dam bao duoc tieu chuan do vong va uong vung cho phep.
Quy trinh kiem dinh thuc te: Phuong phap va Thiet bi
Tai Kiem Dinh Xay Dung Mien Nam, chung toi khong bao gio lam mot cach mang tinh. Moi phan cong trinh deu phai co quy trinh thao tac (SOP) rieng. Quy trinh nay bao gom 5 buoc co ban, tu cham chon den lap bao cao.
Buoc 1: Thu thap tai lieu va Danh gia truoc kiem dinh
Truoc khi den sat, chung toi can cac van ban: Ho so thiet ke (dang thiet ke, dang thi cong), cac van ban nhan bien cong, va cac bao cao kiem dinh truoc do (neu co). Viec hieu ro thiet ke ban dau giup chung toi dat ra muc tieu kiem dinh chinh xac. Chung toi can biet: Cot nay cao bao nhieu? Dam nay chiu tai troi bao nhieu? Mau betong la gi?
Buoc 2: Chuan bi Thiet bi va Nhan su
Thiet bi do luong la 'co quan' cua ki su. Chung toi se su dung cac loai thiet bi sau:
- Mach Kinh Vi / May Toan Da (Total Station): De do cac diem toa do trong khong gian 3D. Do chinh xac den milimet, phuong phap nay rat tot de do do vong vung cua cot cao.
- Mach Thuy Binh Laser (Laser Level): Su dung de do do song mac cua mat dat, mat ban, mat dam. Phan loai may laser tu dong co do chinh xac cao, nhanh va de su dung.
- Dong Kim Dong (Plumb Bob) va Dan Dai: De kiem tra do doc thang cua cot, tuy nhien phuong phap nay can co kinh nghiem va thoi gian dai de chuan hoa.
- Mach Do Bong Mat (Dial Gauge): De do do vong cuc ky nho (de) tren cot, dam.
Buoc 3: Ti Hanh Do Luong Tren Sa
Day la buoc quan trong nhat. Chung toi se do luong theo cac nhom:
- Do do doc thang cua cot (Verticality of Columns): Do do benh cua cot theo hai chieu (X va Y). So sanh voi thiet ke va tieu chuan cho phep.
- Do do song mac cua dam (Camber of Beams): Do do uong cua dam gan hai dau. Can lay ve trung diem de do.
- Do do song mac cua ban (Flatness of Slabs): Do do uong, beo cua mat ban. Su dung may laser scan hoac day dan.
- Do do vong vung cua toa cong trinh (Building Deviation): Do do lech cua toa nha so voi dia chi thiet ke.
Buoc 4: Phan tich Du lieu va So sanh
Sau khi co du lieu, ky su cua chung toi se nhap vao phan mem de phan tich. So sanh so lieu do duoc voi tieu chuan TCVN va QCVN. Neu do cong veh > gioi han cho phep, chung toi se danh gia mức do nguy hiem. Co the do cong veh do do co the khong anh huong ngay den an toan, hoac co the do do da ton tai tu dau, hoac co the la do su suy giam chat luong.
Buoc 5: Lap Bao Cao va De Xuat Bien Phap
Bao cao kiem dinh la van ban phap ly. No phai noi ro: Cong trinh co dat tieu chuan khong? Neu khong, nguy co la gi? Bien phap xu ly la gi? Chi phi du doan la bao nhieu? De Xuat Bien Phap la phan then chan, noi chung toi - Kiem Dinh Xay Dung Mien Nam - se dong vai tro la nguon tin cay de chu dau tu quyet dinh.
Bang quy chuan cho phep sai so va Tieu chuan chap nhan
De ban co the hinh dung ro hon, chung toi xin lap bang so sánh cac gioi han cho phep theo TCVN 9438:2012 va cac van ban lien quan. Cac so lieu nay la 'lua' de lochot cac cong trinh.
| Don Vi Ket Cau | Yeu to Kiem Tra | Gioi Han Cho Phep (Tolerance) | Ghi Chu |
|---|---|---|---|
| Cot (Column) | Do doc thang (Verticality) | H/1000, toi da 15mm | H: Cao do cot. Gioi han toi da 15mm. |
| Vong vung (Sway) | +/- 20mm (tuy theo kich thuoc) | Thuc te co the khac nhau | |
| Dam (Beam) | Do song mac (Camber) | L/1000 (voi L la chieu dai dam) | L: Chieu dai tinh toan. Neu dam u qua nhieu, can co bien phap. |
| Do cao mat dam | +/- 10mm | Tuy theo kich thuoc dam | |
| Ban (Slab) | Do song mac (Flatness) | 3mm/2m (hoac 5mm/3m) | Phap do deu tren mat dat. Yeau cau cao voi nha o. |
| Toa Nha (Building) | Vong vung toa nha | H/1000, toi da 50mm | H: Tong chieu cao cong trinh. |
| Lech vi tri | +/- 10mm | So voi tim dinh (axis) |
Luu y quan trong: Cac so lieu tren la cho thi cong moi. Doi voi cong trinh cu, viec danh gia se phuc tap hon. Neu cong trinh da su dung da nhieu nam, co the co su thay doi. Ky su kiem dinh can co kinh nghiem de danh gia xem do cong veh do do co phai la do hien tai hay la do huu co.
Cac bien phap xu ly khi cong trinh vuoit qua gioi han cho phep
Neu qua trinh kiem dinh, chung toi phat hien cong trinh co do cong veh > gioi han cho phep, khong co nghia la cong trinh se bi pha bo. Neu phan tich chi ra rang cong trinh van co kha nang chiu luc va an toan (nhu la do uong vung chi la hinh hoc, khong anh huong den kha nang chiu luc), chung toi co the de xuat chap nhan co dieu kien.
Tuy nhien, neu do cong veh gay ra nguy hiem (cot bi benh rat nhieu, dam bi uong rat nhieu, co the gay ra tran), chung toi can co cac bien phap xu ly. Day la cac giai phap ky thuat ma chung toi thuong de xuat:
1. Gia co Bang Cac Bo (Strengthening with Additional Members)
Vi du, neu cot bi benh, chung toi co the them mot cot be tong co the o ben canh de chia tai troi. Neu dam bi uong, co the them mot dam beo o ben duoi hoac ben tren de tang kha nang chiu luc.
2. Gia co Bang Thep (Steel Jacketing)
Dung he thep (gusset plate, angle steel) de boc ngoai cot hoac dam. Phuong phap nay tang kha nang chiu luc va tang do co curng cho ket cau. Thep se giup ham cot, dam khong bi uong them.
3. Gia co Bang Xi Mang Hoa Hoc (Grouting & Chemical Injection)
Nếu do cong veh do do la do ket cau bi tan, co the su dung xi mang hoa hoc de chen vao cac khe ron, tang do co curng va tang kha nang chiu luc.
4. Gia co Bang FRP (Fiber Reinforced Polymer)
Day la cong nghe tien tien. Bang FRP co do ben cao, trong, de thi cong. Chung toi co the boi FRP len mat cot, dam de tang kha nang chiu luc ma khong tang nhieu trong luong.
5. Sua Chua Hinh Hoc (Geometric Correction)
Trong mot so truong hop, chung toi co the can dong, nham lai ket cau ve vi tri doc thang. Tuy nhien, bien phap nay rat de roi va chi co the lam trong nhung truong hop cuc ky dac biet, can co viec tinh toan ky luong.
Ket luan va Vai tro cua Don Vi Kiem Dinh Doc Lap
Kiem dinh do cong veh khong phai la viec do de de de. Do la mot qua trinh phan tich ky thuat phuc tap, lien quan den sinh命 (su song) cua con nguoi su dung cong trinh. Voi kinh nghiem thanh lap va uy tin tu nhieu nam hoat dong, Kiem Dinh Xay Dung Mien Nam luon cam ket mang den cho ban va cong trinh cac phan tich chinh xac, khach quan va khoa hoc nhat.
Khi ban giao viec cho chung toi, ban khong chi nhan duoc mot so lieu, ma nhan duoc mot 'giai phap'. Chung toi khong chi noi 'cong trinh cua ban bi ben', ma noi 'cong trinh cua ban bi ben 5mm, duoi gioi han cho phep, khong nguy hiem' hoac 'cong trinh cua ban bi ben 50mm, can co bien phap gia co FRP'.
Hy vong, bai viet nay da mang den cho ban nhugng thong tin co ich ve Kiem Dinh Do Cong Veh. Nguoi ta noi, 'Dat tien la de, dat loi la kho'. Trong xay dung, dat tien la de, dat an toan la kho. Va Kiem Dinh Xay Dung Mien Nam la nguoi ban hanh an toan do.
"Kiem dinh la 'suc khoe' cho cong trinh. Khong co Kiem Dinh, cong trinh nhu nguoi khong co suc khoe, mat an toan. Chinh vi vay, chung toi luon dong vai tro la nguoi bao ve cong trinh va con nguoi." - Ban Giao Duc Kiem Dinh Xay Dung Mien Nam.
Tren day la toan bo nhun nguyen ve Kiem Dinh Do Cong Veh. Neu ban can thong tin them hoac muon gui cong trinh kiem dinh, vui long lien he voi chung toi.
